Podcasts about Xenopus

Play Episode Listen Later Aug 1, 2023

Link to bioRxiv paper: http://biorxiv.org/cgi/content/short/2023.07.31.547741v1?rss=1 Authors: Feng, M. S., Kettelberger, M., Bestman, J. E. Abstract: Neural progenitor cells (NPCs) are the highly polarized dividing stem cells of the developing brain that give rise to all neurons and glia. Early on, NPCs divide symmetrically and expand the pool of progenitor cells, but as development continues the NPCs begin to asymmetrically divide to produce neurons. The mechanisms that govern this irreversible commitment to neurogenesis are not fully understood. Here we use timelapse 3D confocal microscopy to observe NPCs, their cellular progeny, and their mitochondria in the developing Xenopus tectum. Our results track individual NPCs over days and show that they contain abundant mitochondria that form complicated networks distributed throughout the cells. We find that NPCs preparing to divide shift mitochondria toward the cell body where they become asymmetrically distributed, suggesting that the cells control which progeny inherit mitochondria. To test the role that mitochondria play in cell division we overexpressed the mitochondrial biogenesis master regulator, PGC-1a, which induced the NPCs to asymmetrically divide and produce neurons, while PGC-1a knockdown limited neurogenesis. Together these data suggest that the regulation of mitochondria by NPCs prior to cell division and the unequal inheritance contributes to the fate of the newborn cells in the developing brain. Copy rights belong to original authors. Visit the link for more info Podcast created by Paper Player, LLC

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Novel centriolar defects underlie a primary ciliary dyskinesia phenotype in adenylate kinase 7 deficient ciliated epithelium.

Play Episode Listen Later Jul 25, 2023

Link to bioRxiv paper: http://biorxiv.org/cgi/content/short/2023.07.25.550535v1?rss=1 Authors: Sheridan, J., Grata, A., Suva, E. E., Bresteau, E., Mitchell, L. R., Mitchell, B. Abstract: The skin of Xenopus embryos contains numerous multiciliated cells (MCCs), which collectively generate a directed fluid flow across the epithelial surface essential for distributing the overlaying mucous. MCCs develop into highly specialized cells to generate this flow, containing approximately 150 evenly spaced centrioles that give rise to motile cilia. MCC-driven fluid flow can be impaired when ciliary dysfunction occurs, resulting in primary ciliary dyskinesia (PCD) in humans. Mutations in a large number of genes (~50) have been found to be causative to PCD. Recently, studies have linked low levels of Adenylate Kinase 7 (AK7) gene expression to patients with PCD; however, the mechanism for this link remains unclear. Additionally, AK7 mutations have been linked to multiple PCD patients. Adenylate kinases modulate ATP production and consumption, with AK7 explicitly associated with motile cilia. Here we reproduce an AK7 PCD-like phenotype in Xenopus and describe the cellular consequences that occur with manipulation of AK7 levels. We show that AK7 localizes throughout the cilia in a DPY30 domain-dependent manner, suggesting a ciliary function. Additionally, we find that AK7 overexpression increases centriole number, suggesting a role in regulating centriole biogenesis. We find that in AK7-depleted embryos, cilia number, length, and beat frequency are all reduced, which in turn, significantly decreases the tissue-wide mucociliary flow. Additionally, we find a decrease in centriole number and an increase in sub-apical centrioles, implying that AK7 influences both centriole biogenesis and docking, which we propose underlie its defect in ciliogenesis. We propose that AK7 plays a role in PCD by impacting centriole biogenesis and apical docking, ultimately leading to ciliogenesis defects that impair mucociliary clearance. Copy rights belong to original authors. Visit the link for more info Podcast created by Paper Player, LLC

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Non-canonical function of folate/folate receptor 1 during neural tube formation

Play Episode Listen Later Jul 21, 2023

Link to bioRxiv paper: http://biorxiv.org/cgi/content/short/2023.07.19.549718v1?rss=1 Authors: Balashova, O. A., Panoutsopoulos, A. A., Visina, O., Selhub, J., Knoepfler, P., Borodinsky, L. N. Abstract: Folate supplementation reduces the occurrence of neural tube defects, one of the most common and serious birth defects, consisting in the failure of the neural tube to form and close early in pregnancy. The mechanisms underlying neural tube defects and folate action during neural tube formation remain unclear. Here we show that folate receptor 1 (FOLR1) is necessary for the formation of neural tube-like structures in human-cell derived neural organoids. Knockdown of FOLR1 in human neural organoids as well as in the Xenopus laevis in vivo model leads to neural tube defects that are rescued by pteroate, a folate precursor that binds to FOLR1 but is unable to participate in metabolic pathways. We demonstrate that FOLR1 interacts with and opposes the function of CD2-associated protein (CD2AP), a molecule that we find is essential for apical endocytosis and the spatiotemporal turnover of the cell adherens junction component C-cadherin in neural plate cells. The counteracting action of FOLR1 on these processes is mediated by regulating CD2AP protein level via a degradation-dependent mechanism. In addition, folate and pteroate increase Ca2+ transient frequency in the neural plate in a FOLR1-dependent manner, suggesting that folate/FOLR1 signal intracellularly to regulate neural plate folding. This study identifies a mechanism of action of folate distinct from its vitamin function during neural tube formation. Copy rights belong to original authors. Visit the link for more info Podcast created by Paper Player, LLC

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Female-biased expressed odorant receptor genes differentially tuned to repulsive or attractive plant volatile compounds in the turnip moths

Play Episode Listen Later Jul 12, 2023

Link to bioRxiv paper: http://biorxiv.org/cgi/content/short/2023.07.11.548602v1?rss=1 Authors: Zhang, D.-D., Hou, X.-Q., Powell, D., Lofstedt, C. Abstract: Insects rely on their highly efficient and precise olfactory systems to find suitable mates, host plants and oviposition sites, and adapt to the changing environment. The odorant receptors (ORs) including pheromone receptors (PRs) play a vital role in this process. While extensive studies have been focusing on deorphanization of lepidopteran PR genes, the information on the ligand profiles of general ORs is still sparse. In the present study, we identified a repertoire of 61 ORs including the co-receptor Orco from antennal and ovipositor transcriptomes of the turnip moth Agrotis segetum, which clustered in all the major lepidopteran OR clades. We characterized the function of eight female-biased expressed ORs in Xenopus oocytes and found three ORs differentially tuned to plant volatile compounds that might be repulsive or attractive to the moths. AsegOR13 was broadly tuned to a number of herbivore-induced plant volatiles (HIPVs) while AsegOR20 was specific to citral; AsegOR17 was narrowly tuned to the alcohols, isoamyl alcohol, pentanol and benzyl alcohol, that are potentially attractive to moths. The orthologues of the three ORs in other moth species seem to share the conserved function. Our results support the hypothesis that insects recognize their host plants mostly by detecting the mixture of ubiquitous compounds, instead of taxonomically characteristic host compounds. The combination of narrowly and broadly tuned ORs will ensure both the accuracy of the most important odor signals and the plasticity of the olfactory system to the changes in the environment. Copy rights belong to original authors. Visit the link for more info Podcast created by Paper Player, LLC

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Cell contacts and pericellular matrix in the Xenopus gastrula chordamesoderm

Play Episode Listen Later Jul 5, 2023

Link to bioRxiv paper: http://biorxiv.org/cgi/content/short/2023.07.05.547782v1?rss=1 Authors: Luu, O., Barua, D., Winklbauer, R. Abstract: Convergent extension of the chordamesoderm is the best-examined gastrulation movement in Xenopus. Here we study general features of cell-cell contacts in this tissue by combining depletion of adhesion factors C-cadherin, Syndecan-4, fibronectin, and hyaluronic acid, the analysis of respective contact width spectra and contact angles, and La3+ staining of the pericellular matrix. We provide evidence that like in other gastrula tissues, cell-cell adhesion in the chordamesoderm is largely mediated by different types of pericellular matrix. Specific glycocalyx structures previously identified in Xenopus gastrula tissues are absent in chordamesoderm but other contact types like 10-20 nm wide La3+ stained structures are present instead. Knockdown of any of the adhesion factors reduces the abundance of cell contacts but not the average relative adhesiveness of the remaining ones: a decrease of adhesiveness at low contact widths is compensated by an increase of contact widths and an increase of adhesiveness proportional to width. From the adhesiveness-width relationship, we derive a model of chordamesoderm cell adhesion that involves the interdigitation of distinct pericellular matrix units. Quantitative description of pericellular matrix deployment suggests that reduced contact abundance upon adhesion factor depletion is due to some contact types becoming non-adhesive and others being lost. Copy rights belong to original authors. Visit the link for more info Podcast created by Paper Player, LLC

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Cyclin A/cdk activity and FAM122A-dependent inhibition of PP2A-B55 are essential to trigger mitosis.

Wissensnachrichten - Deutschlandfunk Nova

Play Episode Listen Later Jun 22, 2023

Link to bioRxiv paper: http://biorxiv.org/cgi/content/short/2023.06.20.545672v1?rss=1 Authors: Lacroix, B., Vigneron, S., Labbé, J. C., Pintard, L., Labesse, G., Castro, A., Lorca, T. Abstract: Entry into mitosis has been classically attributed to the activation of cyclin B/cdk1 amplification loop by a partial pool of this kinase that becomes active at the end of G2. However, how this pool is activated is still unknown. Here we discovered a new role of the recently identified PP2A-B55 inhibitor FAM122A in triggering mitotic entry. Accordingly, the depletion of the orthologue of FAM122A in C. elegans, prevents entry into mitosis in germline stem cells. Moreover, our data in Xenopus egg extract strongly supports that FAM122A29 dependent inhibition of PP2A-B55 could be the initial event promoting mitotic entry. The inhibition of this phosphatase allows the subsequent phosphorylation of first mitotic substrates by cyclin A/cdk resulting in cyclin B/cdk1 and Greatwall (Gwl) activation. However, interestingly, from Gwl activation, Arpp19/ENSA become phosphorylated and compete with FAM122A promoting its dissociation from PP2A-B55 and taking over its inhibition until the end of mitosis. Copy rights belong to original authors. Visit the link for more info Podcast created by Paper Player, LLC

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Trinkgeld, Mähroboter, Gipfelabbruch

Play Episode Listen Later Jun 13, 2023 6:06

Die Themen in den Wissensnachrichten: +++ Deutsche geben weltweit am häufigsten Trinkgeld +++ Mähroboter sind eine Gefahr für Igel +++ Berggipfel in Tirol wahrscheinlich wegen schmelzendem Permafrost abgebrochen +++**********Weiterführende Quellen zu dieser Folge:Deutsche und Amerikaner geben am häufigsten Trinkgeld, YouGov-Umfrage, 13.06.2023Glyphosate without Co-formulants affects embryonic development of the south african clawed frog Xenopus laevis, Ecotoxicology and Environmental Safety, 15. Juli 2023Wissenschaftliche Daten zeigen: Mähroboter sind eine große und wachsende Gefahr für Igel, Leibniz-Institut für Zoo- und Wildtierforschung, 13.06.2023Erkundungsflug nach Felssturz im Silvrettagebiet mit Landesgeologie, Land Tirol, 12.06.2023Net Zero Stocktake 2023, Net Zero Tracker, 12.06.2023Effect of local climate anomalies on giraffe survival, Biodiversity and Conservation, 10.06.2023**********Ihr könnt uns auch auf diesen Kanälen folgen: Tiktok und Instagram.**********Weitere Wissensnachrichten zum Nachlesen: https://www.deutschlandfunknova.de/nachrichten

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Bilateral retinofugal pathfinding impairments limit behavioral compensation in near-congenital one-eyed Xenopus laevis

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Play Episode Listen Later May 5, 2023

Link to bioRxiv paper: http://biorxiv.org/cgi/content/short/2023.05.05.539408v1?rss=1 Authors: Forsthofer, M., Gordy, C., Kolluri, M., Straka, H. Abstract: To generate a coherent visual percept, information from both eyes must be appropriately transmitted into the brain, where binocular integration forms the substrate for visuomotor behaviors. To establish the anatomical substrate for binocular integration, the presence of bilateral eyes and interaction of both optic nerves during retinotectal development play a key role. However, the extent to which embryonic monocularly derived visual circuits can convey visuomotor behaviors is unknown. In this study, we assessed the retinotectal anatomy and visuomotor performance of embryonically generated one-eyed tadpoles. In one-eyed animals, the axons of retinal ganglion cells from the singular remaining eye exhibited striking irregularities in their central projections in the brain, generating a non-canonical ipsilateral retinotectal projection. This data is indicative of impaired pathfinding abilities. We further show that these novel projections are correlated with an impairment of behavioral compensation for the loss of one eye. Copy rights belong to original authors. Visit the link for more info Podcast created by Paper Player, LLC

Synthetic Human Embryos and Organs with Ali H. Brinvanlou - Breaking News in Stem Cells

Health and Medicine (Video)

Play Episode Listen Later Apr 28, 2023 84:30

Ali H. Brinvanlou, Ph.D., shares his work using in vitro attached human embryos and genome-edited synthetic embryos derived from human embryonic stem cells to learn the molecular, cellular, and embryological basis of early human development. Series: "Stem Cell Channel" [Health and Medicine] [Show ID: 38324]

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Synthetic Human Embryos and Organs with Ali H. Brinvanlou - Breaking News in Stem Cells

University of California Audio Podcasts (Audio)

Play Episode Listen Later Apr 28, 2023 84:30

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Synthetic Human Embryos and Organs with Ali H. Brinvanlou - Breaking News in Stem Cells

Health and Medicine (Audio)

Play Episode Listen Later Apr 28, 2023 84:30

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Synthetic Human Embryos and Organs with Ali H. Brinvanlou - Breaking News in Stem Cells

UC San Diego (Audio)

Play Episode Listen Later Apr 28, 2023 84:30

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Synthetic Human Embryos and Organs with Ali H. Brinvanlou - Breaking News in Stem Cells

Stem Cell Channel (Audio)

Play Episode Listen Later Apr 28, 2023 84:30

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Nuclear growth and import can be uncoupled

Play Episode Listen Later Apr 21, 2023

Link to bioRxiv paper: http://biorxiv.org/cgi/content/short/2023.04.19.537556v1?rss=1 Authors: Chen, P., Mishra, S., Levy, D. L. Abstract: What drives nuclear growth? Studying nuclei assembled in Xenopus egg extract and focusing on importin /{beta}-mediated nuclear import, we show that, while nuclear growth depends on nuclear import, nuclear growth and import can be uncoupled. Nuclei containing fragmented DNA grew slowly despite exhibiting normal import rates, suggesting nuclear import itself is insufficient to drive nuclear growth. Nuclei containing more DNA grew larger but imported more slowly. Altering chromatin modifications caused nuclei to grow less while still importing to the same extent or to grow larger without increasing nuclear import. Increasing heterochromatin in vivo in sea urchin embryos increased nuclear growth but not import. These data suggest that nuclear import is not the primary driving force for nuclear growth. Instead, live imaging showed that nuclear growth preferentially occurred at sites of high chromatin density and lamin addition, whereas small nuclei lacking DNA exhibited less lamin incorporation. Our hypothesized model is that lamin incorporation and nuclear growth are driven by chromatin mechanical properties, which depend on and can be tuned by nuclear import. Copy rights belong to original authors. Visit the link for more info Podcast created by Paper Player, LLC

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Two conserved vocal central pattern generators broadly tuned for fast and slow rates generate species-specific vocalizations in Xenopus clawed frogs

Play Episode Listen Later Jan 28, 2023

Link to bioRxiv paper: http://biorxiv.org/cgi/content/short/2023.01.27.525835v1?rss=1 Authors: Yamaguchi, A., Peltier, M. Abstract: Across phyla, species-specific vocalizations are used by males to attract females. Functional analyses of the neural circuitry underlying behavior have been difficult, particularly in vertebrates. However, using an ex vivo brain preparation that produces fictive vocalizations, we previously identified anatomically distinct fast and slow central pattern generators (CPGs) that drive the fast and slow clicks of male courtship calls in male African clawed frogs, Xenopus laevis. To gain insight into the evolution of neural circuits underlying courtship calls, we extended this approach to four additional species. Here, we show that although the exact rate and duration of the clicks are unique to each species, fast and slow CPGs identified in male X. laevis are conserved across species. Further, we show that the development of fast CPGs depends on testosterone in a species-specific manner: testosterone facilitates the development of fast CPGs in a species with a courtship call containing fast clicks, but not in a species with a courtship call made entirely of slow clicks. Finally, we showed that, unlike other vestigial neural circuits that remain latent, the fast CPGs are not inherited by all species; rather, they are possessed only by the species that produce fast clicks. The results suggest that species specific calls of the genus Xenopus have evolved by utilizing conserved fast or slow CPGs that are broadly tuned to generate fast or slow trains of clicks, the development of which appear to be regulated by a strategic expression of testosterone receptors in the brain of each species. Copy rights belong to original authors. Visit the link for more info Podcast created by Paper Player, LLC

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Crb3 stabilizes activated Ezrin-Radixin-Moesin to organize the apical domain of multiciliated cells

Play Episode Listen Later Jan 24, 2023

Link to bioRxiv paper: http://biorxiv.org/cgi/content/short/2023.01.24.525309v1?rss=1 Authors: Burckle, C., Raitiere, J., Kodjabachian, L., Le-Bivic, A. Abstract: Cell shape changes mainly rely on the remodeling of the actin cytoskeleton. Multiciliated cells (MCCs) of the mucociliary epidermis of Xenopus laevis embryos, as they mature, dramatically reshape their apical domain to grow cilia, in coordination with the underlying actin cytoskeleton. Crumbs (Crb) proteins are multifaceted transmembrane apical polarity proteins known to recruit actin linkers and promote apical membrane growth. Here, we identify the homeolog Crb3.L as an important player for apical domain morphogenesis in differentiating Xenopus MCCs. We found that Crb3.L is initially present in cytoplasmic vesicles in the vicinity of ascending centrioles/basal bodies (BBs), then at the expanding apical membrane concomitantly with BB docking, and finally in the ciliary shaft of growing and mature cilia. Using morpholino-mediated knockdown, we show that Crb3.L-depleted MCCs display a complex phenotype associating reduction in the apical surface, disorganization of the apical actin meshwork, centriole/BB migration defects, as well as abnormal ciliary tuft formation. Based on prior studies, we hypothesized that Crb3.L could regulate Ezrin-Radixin Moesin (ERM) protein subcellular localization in MCCs. Strikingly, we observed that endogenous phospho-activated ERM (pERM) is recruited to the growing apical domain of inserting MCCs, in a Crb3.L-dependent manner. Our data suggest that Crb3.L recruits and/or stabilizes activated pERM at the emerging apical membrane to allow coordinated actin-dependent expansion of the apical membrane in MCCs. Copy rights belong to original authors. Visit the link for more info Podcast created by Paper Player, LLC

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Characterisation and automated quantification of induced seizure-related behaviours in Xenopus laevis tadpoles

Play Episode Listen Later Nov 20, 2022

Link to bioRxiv paper: http://biorxiv.org/cgi/content/short/2022.11.18.517140v1?rss=1 Authors: Panthi, S., Chapman, P., Szyszka, P., Beck, C. W. Abstract: Epilepsy, a clinical diagnosis characterized by paroxysmal episodes known as seizures, affects 1% of people worldwide. An estimated 30% of patients continue to have seizures even on medication, and adverse effects are common. Safe and patient-specific treatment is vital and can be achieved by the development of rapid pre-clinical models of for identified epilepsy genes. Epilepsy can result from either brain injury or gene mutations, and can also be induced chemically. Xenopus laevis tadpoles could be a useful model for confirmation of variants of unknown significance found in epilepsy patients, and for drug re-purposing screens that could eventually lead to benefits for patients. Here, we characterise and quantify seizure-related behaviours in X. laevis tadpoles arrayed in 24-well plates. To provoke acute seizure behaviours, tadpoles were chemically induced with either pentylenetetrazole (PTZ) or 4-aminopyridine (4-AP). To test the capacity to adapt this method for drug testing, we also exposed induced tadpoles to the anti-seizure drug valproate (VPA). Four induced seizure-like behaviours were described and manually quantified, and two of these (darting, circling) could be accurately detected automatically, using the video analysis software TopScan. Additionally, we recorded swimming trajectories and mean swimming velocity. Automatic detection showed that either PTZ or 4-AP induced darting behaviour and increased mean swimming velocity compared to untreated controls. Both parameters were significantly reduced in the presence of VPA. In particular, darting behaviour was a shown to be a sensitive measure of epileptic seizure activity. While we could not automatically detect the full range of seizure behaviours, this method shows promise for future studies, since X. laevis is a well-characterised and genetically tractable model organism. Copy rights belong to original authors. Visit the link for more info Podcast created by Paper Player, LLC

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Mitotic chromosomes scale to nucleo-cytoplasmic ratio and cell size in Xenopus

Play Episode Listen Later Oct 21, 2022

Link to bioRxiv paper: http://biorxiv.org/cgi/content/short/2022.10.20.513104v1?rss=1 Authors: Zhou, C. Y., Dekker, B., Liu, Z., Cabrera, H., Ryan, J., Dekker, J., Heald, R. Abstract: During the rapid and reductive cleavage divisions of early embryogenesis, subcellular structures such as the nucleus and mitotic spindle scale to decreasing cell size. Mitotic chromosomes also decrease in size during development, presumably to coordinately scale with mitotic spindles, but underlying mechanisms are unclear. Here we combine in vivo and in vitro approaches using eggs and embryos from the frog Xenopus laevis to show that mitotic chromosome scaling is mechanistically distinct from other forms of subcellular scaling. We found that mitotic chromosomes scale continuously with cell, spindle and nuclear size in vivo. However, unlike for spindles and nuclei, mitotic chromosome size cannot be re-set by cytoplasmic factors from earlier developmental stages. In vitro, increasing nucleo-cytoplasmic (N/C) ratio is sufficient to recapitulate mitotic chromosome scaling, but not nuclear or spindle scaling, through differential loading of maternal factors during interphase. An additional pathway involving importin scales mitotic chromosomes to cell surface area/volume (SA/V) during metaphase. Finally, single-chromosome immunofluorescence and analysis of Hi-C data suggest that mitotic chromosomes scale through decreased recruitment of condensin I, resulting in major rearrangements of DNA loop architecture to accommodate the same amount of DNA on a shorter axis. Together, our findings demonstrate that mitotic chromosome size is set by spatially and temporally distinct developmental cues in the early embryo. Copy rights belong to original authors. Visit the link for more info Podcast created by Paper Player, LLC

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Ploidy modulates cell size and metabolic rate in Xenopus embryos

Play Episode Listen Later Oct 17, 2022

Link to bioRxiv paper: http://biorxiv.org/cgi/content/short/2022.10.17.512616v1?rss=1 Authors: Cadart, C., Bartz, J., Oaks, G., Liu, M., Heald, R. Abstract: A positive correlation between genome size and cell size is well documented, but impacts on animal physiology are poorly understood. In Xenopus frogs, the number of genome copies (ploidy) varies across species and can be manipulated within a species. Here we show that triploid tadpoles contain fewer, larger cells than diploids and consume oxygen at a lower rate. Treatments that altered cell membrane stability or electrical potential abolished this difference, suggesting that a decrease in total cell surface area reduces basal energy consumption in triploids. Comparison of Xenopus species that evolved through polyploidization revealed that metabolic differences emerged during development when cell size scaled with genome size. Thus, ploidy affects metabolism by altering the cell surface area to volume ratio in a multicellular organism. Copy rights belong to original authors. Visit the link for more info Podcast created by Paper Player, LLC

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Mutation of the ALS/FTD-associated RNA-binding protein FUS alters axonal cytoskeletal organisation

Play Episode Listen Later Oct 7, 2022

Link to bioRxiv paper: http://biorxiv.org/cgi/content/short/2022.10.04.510780v1?rss=1 Authors: van Tartwijk, F. W., Wunderlich, L. C. S., Mela, I., Makarchuk, S., Jakobs, M. A. H., Qamar, S., Franze, K., Kaminski Schierle, G. S., St George-Hyslop, P. H., Lin, J. Q., Holt, C. E., Kaminski, C. F. Abstract: Aberrant condensation and localisation of the RNA-binding protein fused in sarcoma (FUS) occur in variants of amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). ALS is also associated with cytoskeletal defects, genetically and through observations of compromised axonal transport. Here, we asked whether compromised axonal cytoskeletal organisation is an early feature of FUS-associated ALS/FTD. We used an ALS-associated mutant FUS(P525L) and the FTD-mimic hypomethylated FUS, FUS(16R), to investigate the common and distinct cytoskeletal changes found in these two reported Xenopus models. Combining a novel atomic force microscopy (AFM)-based approach for in vitro cytoskeletal characterisation and in vivo axonal branching analysis, we found that mutant FUS reduced actin density in the dynamically remodelling growth cone, and reduced axonal branch complexity. We furthermore found evidence of an axon looping defect for FUS(P525L). Therefore, we show that compromised actin remodelling is potentially an important early event in FUS-associated pathogenesis. Copy rights belong to original authors. Visit the link for more info Podcast created by PaperPlayer

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Early midbrain sensorimotor pathway is involved in the timely initiation and direction of swimming in the hatchling Xenopus laevis tadpole.

director biology tufts university distinguished professor developmental synthetic biology michael levin xenopus

Play Episode Listen Later Aug 26, 2022

Link to bioRxiv paper: http://biorxiv.org/cgi/content/short/2022.08.24.505113v1?rss=1 Authors: Larbi, M. C., Messa, G., Jalal, H., Koutsikou, S. Abstract: Vertebrate locomotion is heavily dependent on descending control originating in the midbrain and subsequently influencing central pattern generators in the spinal cord. However, the midbrain neuronal circuitry and its connections with other brainstem and spinal motor circuits has not been fully elucidated. Basal vertebrates with very simple nervous system, like the hatchling Xenopus laevis tadpole, have been instrumental in unravelling fundamental principles of locomotion and its suspraspinal control. Here, we use behavioral and electrophysiological approaches in combination with lesions of the midbrain to investigate its contribution to the initiation and control of the tadpole swimming in response to trunk skin stimulation. None of the midbrain lesions studied here blocked the tadpole's sustained swim behavior following trunk skin stimulation. However, we identified that distinct midbrain lesions led to significant changes in the latency and trajectory of swimming. These changes could partly be explained by the increase in synchronous muscle contractions on the opposite sides of the tadpole's body and permanent deflection of the tail from its normal position, respectively. Furthermore, the midbrain lesions led to significant changes in the tadpole's ability to stop swimming when it bumps head on to solid objects. We conclude that the tadpole's embryonic trunk skin sensorimotor pathway involves the midbrain, which harbors essential neuronal circuitry to significantly contribute to the appropriate, timely and coordinated selection and execution of locomotion, imperative to the animal's survival. Copy rights belong to original authors. Visit the link for more info Podcast created by PaperPlayer

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Ep. 220: “Developmental and Synthetic Biology” Featuring Dr. Michael Levin

The Stem Cell Podcast

Play Episode Listen Later Jun 14, 2022 76:53

Dr. Michael Levin is the Director of the Allen Discovery Center and a Distinguished Professor of Biology at Tufts University. He is a cognitive biologist who utilizes model systems such as Xenopus to answer fundamental questions in developmental biology. He talks about regenerating frog legs, using bioelectricity to direct development, and the potential applications of xenobots.

Episode 92. African Frogs, Anuran Evolution, Goliath Frogs and More. with Dr. David Blackburn

AmphibiCast

Play Episode Listen Later Jun 10, 2022 97:16 Very Popular

Tonight I am joined by Dr. David Blackburn. David has spent the majority of his career studying African Frog species, as well as frog evolution and morphology. We begin with a discussion on frog evolution, extinct frogs, and the frogs in fossil record; and we continue on to discuss several African species including the goliath frog and a very rare species of Xenopus. We also discuss some of the new technology that scientists are using to study and recreate rare and extinct amphibian species.To support the show by becoming a Patron on Patreon, for AmphibiCast Merch, and for listener discounts on In Situ Ecosystems vivariums visit: https://linktr.ee/AmphibiCast To learn more about the topics discussed in tonight's show check out these links.Data repository for sharing CT-scans: https://www.morphosource.org/ 3D models for education and outreach: https://sketchfab.com/ufherps Lab website: https://www.floridamuseum.ufl.edu/blackburn-lab/ AmphibiaWeb account for Conraua goliath: https://amphibiaweb.org/cgi/amphib_query?where-genus=Conraua&where-species=goliath AmphibiaWeb account for Trichobatrachus robustus: https://amphibiaweb.org/cgi/amphib_query?where-genus=Trichobatrachus&where-species=robustus AmphibiaWeb account for Xenopus longipes: https://amphibiaweb.org/cgi/amphib_query?where-genus=Xenopus&where-species=longipes

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Bio Bytes 28: Systems Approaches to Studying Neural Circuitry with Darcy Kelley

CU Bio Bytes

Play Episode Listen Later Mar 13, 2022 33:02

In which Darcy Kelley, Harold Weintraub Professor of Biological Sciences, and James discuss Xenopus as a model organism for understanding the biology of behavior and evolution of neural circuits. Professor Kelley describes several ways in which contemporary methods like single-cell RNA sequencing and optogenetics are helping us understand the true connection between neurobiology and behavior. Additionally, she provides insight on how young scientists can effectively develop themselves after initial exposure to research.

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Chromosomes in inviable hybrids: Maiko Kitaoka

Audio-only streams of our videos

Play Episode Listen Later Feb 12, 2022 20:44

When we think of what makes two species distinct, we often think of their ability (or inability) to produce viable offspring. But is there anything we can learn from inviable offspring? In this Share Your Research talk, Maiko Kitaoka discusses her work on closely related Xenopus frogs. She reveals how examining hybridization between these species at the cellular level can provide insight into only the mechanisms that restrict cell division and development, but also broader patterns of how new species are able to evolve.

hybrids chromosomes maiko xenopus

Chromosomes in inviable hybrids: Maiko Kitaoka

iBiology Videos

Play Episode Listen Later Feb 12, 2022 21:15

hybrids chromosomes maiko xenopus

Xenopus in Boots

AI with AI

Play Episode Listen Later Feb 11, 2022 41:39

Andy and Dave discuss the latest in AI news and research, including a report from the School of Public Health in Boston that shows why most “data for good” initiatives failed to impact the COVID-19 health crisis [0:45]. The Department of Homeland Security tests the use of robot dogs (from Ghost Robotics) for border patrol duties [5:00]. Researchers find that public trust in AI varies greatly depending on its application [7:52]. Researchers from Stanford University and Toyota Research Institute find extensive label and model errors in training data, such as over 70% of validation scenes (for publicly available autonomous vehicle datasets) containing at least one missing object box [12:05]. And principal researchers Josh Bongard and Mike Levin join Andy and Dave for more discussion on the latest Xenobots research [18:21]. Follow the link below to visit our website and explore the links mentioned in this episode. https://www.cna.org/CAAI/audio-video

covid-19 ai school public health researchers stanford university boots homeland security xenobots mike levin xenopus toyota research institute

Kubernetes 1.23, with Rey Lejano

Kubernetes Podcast from Google

Play Episode Listen Later Dec 8, 2021 31:51

Learn all about what’s new in today’s Kubernetes 1.23 with its release team lead, Rey Lejano. Rey is a Field Engineer at SUSE/Rancher Labs, and a contributor to the Docs, Release and Security SIGs. Long time listener Adam also drops by to ask Craig what’s been happening with the hiatus. Do you have something cool to share? Some questions? Let us know: web: kubernetespodcast.com mail: kubernetespodcast@google.com twitter: @kubernetespod Chatter of the week Ted Lasso Filming locations Knative applies to become a CNCF project Links from the interview African clawed frog Cross-fertilization and structural comparison of egg extracellular matrix glycoproteins from Xenopus laevis and Xenopus tropicalis ITIL RX-M 1.18 release team 1.23 release team Kubernetes 1.23: The Next Frontier Odd numbered Star Trek movies Star Trek V: The Final Frontier SIG Release Charter Enhancements: Dual stack IPv4/IPv6 - Stable Pod security admission - Beta TTL After Finished Controller - Stable Auto delete PVCs created by StatefulSets - Alpha Skip Volume Ownership Change - Stable Generic Ephemeral Inline Volumes CronJobs Deprecation of FlexVolumes Deprecation of klog flags HorizontalPodAutoscaler v2 API - Stable Ephemeral containers - Beta kubectl events improvements - Alpha Kubelet CRI support - Beta 1.22 interview with Savitha Raghunathan 1.23 lead: James Laverack Kubernetes Contributor Celebration Rey Lejano on Twitter

google docs containers kubernetes community management cloud native k8s istio lejano pvcs xenopus

Just Grab em' in the Xenopus!

Dads Who Game

Play Episode Listen Later Dec 7, 2021 71:55

Welcome back! It's an episode of celebration as T Lock FINALLY got his PS5....but not without a last curveball :( Was the next-gen console worth the wait? Is it enough to sway T Lock from being team X Box? Hasan posed a great question...would you sell the image of your face to be on a marketing robot for 200k? Kids today don't know how good they have it...but some kids, including T Lock's, think they have it better than most. Tap in to hear the wish list of T Lock's two kids. Would you let Santa take all the credit for buying the presents? Scientists who made the first living robot, claim that there are new lifeforms, Xenobots, can now reproduce and self heal. The death of humans are on the horizon. As always, tap the link below to follow our IG. Click the support link in the description to subscribe to the channel. Don't forget to click follow/notification button to keep updated when new episodes come out. Click here for DWG Instagram: https://linktr.ee/everythingtlock --- Support this podcast: https://anchor.fm/dadswhogame/support

kids santa scientists xbox tap playstation 5 xenobots xenopus

Developing methods to break new grounds in science and life with James Fraser (UCSF)

Random Walks

Play Episode Listen Later Nov 28, 2021 98:34

In this episode, I converse with Prof. James Fraser at the University of California, San Francisco. James was an undergraduate at McGill University, where he worked in the lab of Dr. Francois Fagotto on Xenopus developmental biology. As a graduate student, with Tom Alber at UC Berkeley, James established room-temperature X-ray data collection techniques and electron density sampling strategies to define protein conformational ensembles essential for catalysis. Prior to starting an independent position at UCSF, he was a visiting EMBO Short Term Fellow in the lab of Dan Tawfik at the Weizmann Institute of Science in Israel and developed expertise in directed evolution and high-throughput assays of enzymatic or binding activity. In January 2011, James started his independent career as a QB3 at UCSF Fellow affiliated with the Department of Cellular and Molecular Pharmacology. In January 2013, he was appointed as an Assistant Professor in the Department of Bioengineering and Therapeutic Sciences and the California Institute for Quantitative Biosciences (QB3) with promotion to Associate Professor in 2016, and Full Professor in 2020. James is also a Faculty Scientist in the Molecular Biophysics and Integrated Bioimaging Division of Lawrence Berkeley National Lab. The long-term goals of James' research group is to understand how protein conformational ensembles are reshaped by perturbations, such as mutation and ligand binding, and to quantify how these perturbations impact protein function and organismal fitness. To accomplish these goals, they create new computational and biophysical approaches to study how proteins move between different conformational states. Additionally, the group uses two complementary approaches to study the relationship between protein conformational ensembles and function. To dissect consequences of mutations on organismal fitness, they use high-throughput systems biology and biophysical methods to analyze large sets of clinically or biophysically interesting mutations and to improve the ability to engineer new protein functions, they investigate changes to the conformational ensemble as new enzymatic and binding functions emerge from directed evolution studies. We indulge in a fascinating conversation on his enjoyable journey through science and life; foraying into academia from a family of non-academics; the thrill of methods development; the enormous influence of his brilliant mentors, friends, and collaborators; creating a more equitable, open, and just environment in science; and many more things!!

Episode 34. Everything Xenopus with Dr. Marko Horb of the National Xenopus Resource

AmphibiCast

Play Episode Listen Later Mar 27, 2021 98:19

Have you ever wanted to know everything there is to know about the Xenopus genus? Well, this is the episode you have been waiting for. Tonight my guest is Dr. Marko Horb of the National Xenopus Resource and we discuss the genus from top to bottom. Xenopus (commonly known as African clawed frogs) have been model organisms in labs for almost a century and are also an extremely popular genus among hobbyists. Our understating of them has grown tremendously over the years and they have been instrumental in the development of medical applications for humans. Marko walks us through their beginnings in early labs, their lifecycles, husbandry specifics, and much more. Dr. Horb is also the Lab's Institutional Animal Care and Use Committee (IACUC) Chairman, and we go on to discuss the specifics of amphibian animal welfare and high standards that the lab consistently exceeds. This episode is packed with information that any amphibian enthusiast can appreciate so sit back and enjoy it.

national african resource lab marko xenopus horb

How Does Fever Help You Get Better?

Curiosity Daily

Play Episode Listen Later Feb 9, 2021 11:56

Learn about how a fever helps you get better; why the first reliable and widely available pregnancy test was the African clawed frog; and a potential breakthrough in the shockingly complicated traveling salesperson problem. How Exactly Does Fever Help You Get Better? by Ashley Hamer TED-Ed. (2016). The surprising reason you feel awful when you’re sick - Marco A. Sotomayor [YouTube Video]. In YouTube. https://www.youtube.com/watch?v=gVdY9KXF_Sg ‌Mace, T. A., Zhong, L., Kilpatrick, C., Zynda, E., Lee, C.-T., Capitano, M., Minderman, H., & Repasky, E. A. (2011). Differentiation of CD8+ T cells into effector cells is enhanced by physiological range hyperthermia. Journal of Leukocyte Biology, 90(5), 951–962. https://doi.org/10.1189/jlb.0511229 The first reliable and widely available pregnancy test was... a frog? by Cameron Duke Tyssowski, K. (2018, August 31). Pee is for Pregnant: The history and science of urine-based pregnancy tests. Science in the News. http://sitn.hms.harvard.edu/flash/2018/pee-pregnant-history-science-urine-based-pregnancy-tests/#:~:text=The%20late%201920s%20marked%20the VAITUKAITIS, J. L. (2004). Development of the Home Pregnancy Test. Annals of the New York Academy of Sciences, 1038(1), 220–222. https://doi.org/10.1196/annals.1315.030 Wells, G. P. (1978). Lancelot Thomas Hogben, 9 December 1895 - 22 August 1975. Biographical Memoirs of Fellows of the Royal Society, 24, 183–221. https://doi.org/10.1098/rsbm.1978.0007 Yong, E. (2017, May 4). How a Frog Became the First Mainstream Pregnancy Test. The Atlantic; The Atlantic. https://www.theatlantic.com/science/archive/2017/05/how-a-frog-became-the-first-mainstream-pregnancy-test/525285/ Traveling salesperson update by Cody Gough Computer Scientists Break Traveling Salesperson Record. (2020). Quanta Magazine. https://www.quantamagazine.org/computer-scientists-break-traveling-salesperson-record-20201008/ Karlin, A. R., Klein, N., & Gharan, Shayan Oveis. (2020). A (Slightly) Improved Approximation Algorithm for Metric TSP. ArXiv.org. https://arxiv.org/abs/2007.01409 Curiosity Daily: Weirdest Types of Lightning, Spotting Audio Lies Easily, and the Traveling Salesman Problem https://omny.fm/shows/curiosity-daily/weirdest-types-of-lightning-spotting-audio-lies-ea Subscribe to Curiosity Daily to learn something new every day with Cody Gough and Ashley Hamer. You can also listen to our podcast as part of your Alexa Flash Briefing; Amazon smart speakers users, click/tap “enable” here: https://www.amazon.com/Curiosity-com-Curiosity-Daily-from/dp/B07CP17DJY See omnystudio.com/listener for privacy information.

S02-E02 - Cancer Removal, Xenobots, Doomsday Glacier, Blue-Eyed Humans, NASA's Perseverance, Human Evolution

Science Bytes with Joe and Craig

Play Episode Listen Later Feb 4, 2021 16:57

Cancer Removal Today is Thursday, February 4, 2021. At the top of our news, a new laser system to aid in cancer treatment will help surgeons remove cells without damaging healthy tissue. Scientists proved in the lab that the laser system could remove cancer cells in a way that does not damage the surrounding, healthy cells. Those healthy cells were within the width of a human hair..... Xenobots An African clawed frog, in biology, it is known as Xenopus laevis. This frog typically lives in sub-Saharan Africa's streams and ponds, scavenging for food that it rips apart with its feet. In January, researchers at the University of Vermont and Tufts University published a report that gave the amphibian a different lot in life. They harvested its embryonic skin and heart cells and reassembled the living matter into robotic devices — transforming Xenopus into xenobot. Xenobots are the first robots made entirely of living materials.... Doomsday Glacier If Thwaites melts away, that much-larger ice block will add water to our oceans as well, further driving up sea level rise. If and when this might happen, however, is what researchers are trying to learn. Scientists know that Thwaites Glacier is very important, but still, how much and how fast sea levels increase into the decades and centuries is still uncertain.... Blue Eyes I've heard that the blue waters near ocean glaciers are beautiful to behold. The same could be said about blue eyes. New research shows that people with blue eyes have a single, common ancestor. A team at the University of Copenhagen have tracked down a genetic mutation that took place 6-10,000 years ago and is the cause of the eye color of all blue-eyed humans alive on the planet today.... NASA's Perseverance NASA's Mars 2020 Perseverance rover mission is just 22 days from landing on the surface of Mars. The spacecraft has about 25.6 million miles remaining in its 292.5-million-mile journey and is currently closing that distance at 1.6 miles per second.... Human Evolution When we think of human evolution, our minds wander back to the millions of years it took natural selection to produce modern-day man. Recent research suggests that humans continue to evolve.... --- This episode is sponsored by · Anchor: The easiest way to make a podcast. https://anchor.fm/app --- Send in a voice message: https://anchor.fm/sciencebytes/message Support this podcast: https://anchor.fm/sciencebytes/support

Crosstalk between repair pathways elicits Double-Strand Breaks in alkylated DNA: implications for the action of temozolomide

PaperPlayer biorxiv biochemistry

Play Episode Listen Later Nov 22, 2020

Link to bioRxiv paper: http://biorxiv.org/cgi/content/short/2020.11.21.391326v1?rss=1 Authors: FUCHS, R. P., Isogawa, A., Paulo, J. A., Onizuka, K., Takahashi, T., Amunugama, R., Duxin, J. P., Fujii, S. Abstract: Temozolomide, a DNA methylating agent, is the primary chemotherapeutic drug used in glioblastoma treatment. TMZ induces mostly N-alkylation adducts (N7-methylguanine and N3-methyladenine) and some O6-methylguanine (O6mG). Current models propose that during DNA replication, thymine is incorporated across from O6mG, promoting a futile cycle of mismatch repair (MMR) that leads to DNA double strand breaks (DSBs). To revisit the mechanism of O6mG processing, we reacted plasmid DNA with N-Methyl-N-nitrosourea (MNU), a temozolomide mimic, and incubated it in Xenopus egg extracts. We show that in this system, mismatch repair (MMR) proteins are enriched on MNU-treated DNA and we observe robust, MMR-dependent, repair synthesis. Our evidence also suggests that MMR, initiated at O6mG:C sites, is strongly stimulated in cis by repair processing of other lesions, such as N-alkylation adducts. Importantly, MNU-treated plasmids display DSBs in extracts, the frequency of which increased linearly with the square of alkylation dose. We suggest that DSBs result from two independent repair processes, one involving MMR at O6mG:C sites and the other involving BER acting at a nearby N-alkylation adducts. We propose a new, replication-independent mechanism of action of TMZ, that operates in addition to the well-established cell cycle dependent mode of action. Copy rights belong to original authors. Visit the link for more info

action dna current breaks implications copy repair pathways strand tmz mmr takahashi crosstalk n3 n7 fujii biorxiv mnu xenopus o6 dsbs onizuka

ATP signaling in the integrative neural center of Aplysia californica

Play Episode Listen Later Nov 21, 2020

Link to bioRxiv paper: http://biorxiv.org/cgi/content/short/2020.11.20.392001v1?rss=1 Authors: Györi, J., Kohn, A. B., Romanova, D., Moroz, L. L. Abstract: ATP and its ionotropic P2X receptors are components of the most ancient signaling systems. However, little is known about the distribution and function of purinergic transmission in invertebrates. Here, we cloned, expressed, and pharmacologically characterized P2X receptors in the sea slug Aplysia californica - the prominent model in cellular and system neuroscience. These P2X receptors were successfully expressed in Xenopus oocytes and displayed activation by ATP (EC50=306 M) with two-phased kinetics as well as Na+-dependence. The ATP analog, Bz-ATP, was a less effective agonist (~20%) than ATP, and PPADS was a more potent inhibitor of the P2X receptors than the suramin. We showed that P2X receptors are uniquely expressed within Aplysia's cerebral bioenergetic center (F-cluster). Using RNA-seq, we found that the F-cluster contains more than a dozen unique secretory peptides, including three insulins, interleukins, and potential toxins, as well as ecdysone-type receptors and a district subset of ion channels. This structure is one of the most prominent integrative centers in the entire CNS and remarkably different from the morphologically similar neurosecretory center (bag-cluster) involved in egg-laying behavior. Using RNA-seq, we also characterized the expression of P2X receptors across more than a dozen Aplysia peripheral tissues and developmental stages. We showed that P2X receptors are predominantly expressed in chemosensory structures and during early cleavage stages. The localization and pharmacology of P2X receptors in Aplysia highlight the evolutionary conservation of bioenergetic sensors and chemosensory purinergic transmission across animals. This study also provides a foundation to decipher homeostatic mechanisms in development and neuroendocrine systems. Copy rights belong to original authors. Visit the link for more info

copy atp integrative neural cns signaling kohn biorxiv moroz romanova xenopus

Sodium-Calcium Exchanger Mediates Sensory-Evoked Glial Calcium Transients in the Developing Retinotectal System

Play Episode Listen Later Nov 15, 2020

Link to bioRxiv paper: http://biorxiv.org/cgi/content/short/2020.11.14.383125v1?rss=1 Authors: Benfey, N. J., Li, V. J., Schohl, A., Ruthazer, E. S. Abstract: Various types of sensory stimuli have been shown to induce calcium elevations in glia. However, a mechanistic understanding of the signalling pathways mediating sensory-evoked activity in glia in intact animals is still emerging. Here we demonstrate that during early development of the Xenopus laevis visual system, radial astrocytes in the optic tectum are highly responsive to sensory stimulation. Calcium transients occur spontaneously in radial astrocytes at rest and are abolished by silencing neuronal activity with tetrodotoxin. Visual stimulation drives temporally correlated increases in the activity patterns of neighbouring radial astrocytes. Following blockade of all glutamate receptors, visually-evoked calcium activity in radial astrocytes is enhanced, rather than suppressed, while the additional blockade of either glutamate transporters or sodium-calcium exchangers (NCX) fully prevents visually-evoked responses. Additionally, we demonstrate that blockade of NCX alone is sufficient to prevent visually-evoked responses in radial astrocytes, highlighting a pivotal role for NCX in glia during development. Copy rights belong to original authors. Visit the link for more info

system developing visual copy li sensory calcium sodium biorxiv glial transients xenopus evoked ncx exchanger

ZIKA virus effects on neuroprogenitors are exacerbated by the main pyriproxyfen metabolite via thyroid hormone signaling disruption

PaperPlayer biorxiv biophysics

Play Episode Listen Later Nov 3, 2020

Link to bioRxiv paper: http://biorxiv.org/cgi/content/short/2020.11.03.366468v1?rss=1 Authors: Spirhanzlova, P., Sebillot, A., Vancamp, P., Gothie, J.-D., Le Mevel, S., Leemans, M., Wejaphikul, K., Meima, M., Mughal, B. B., Butruille, L., Roques, P., Remaud, S., Fini, J.-B., Demeneix, B. A. Abstract: North-Eastern Brazil saw intensive application of the insecticide pyriproxyfen (PPF) during the microcephaly outbreak caused by Zika virus (ZIKV). ZIKV requires the neural RNA-binding protein Musashi-1 to replicate. TH represses MSI1. Being a suspected TH disruptor, we hypothesized that co-exposure to the main metabolite of PPF, 4'-OH-PPF, would exacerbate ZIKV effects through increased MSI1 expression. This was tested using in vitro mouse neurospheres and an in vivo TH signaling reporter model, Xenopus laevis. TH signaling was decreased by 4'-OH-PPF in both models. In mouse-derived neurospheres the metabolite reduced neuroprogenitor proliferation as well as markers of neuronal differentiation. The results demonstrated that 4'-OH-PPF significantly induced MSI1 at both the mRNA and protein level, as well as Fasn mRNA. Other TH target genes were also significantly modified. Importantly, several key genes implicated in neuroprogenitor fate and commitment were not dysregulated by 4'-OH-PPF alone, but were in combination with ZIKV infection. These included the neuroprogenitor markers Nestin, Egfr, Gfap, Dlx2 and Dcx. Unexpectedly, 4'-OH-PPF decreased ZIKV replication, although only at the fourth and last day of incubation, and RNA copy numbers stayed within the same order of magnitude. However, intracellular RNA content of neuroprogenitors was significantly decreased in the combined presence of the PPF metabolite and ZIKV. We conclude that 4'-OH-PPF interferes with TH action in vivo and in vitro, inhibiting neuroprogenitor proliferation. In the presence of ZIKV, TH signaling pathways crucial for cortical development are significantly impacted. This provides another example of viral effects that are exacerbated by drug or pesticide use. Copy rights belong to original authors. Visit the link for more info

effects disruption copy mrna rna zika fini unexpectedly signaling zika virus mughal egfr musashi ppf thyroid hormones exacerbated biorxiv roques metabolite xenopus gfap dcx

Confinement size determines the architecture of Ran-induced microtubule networks

Play Episode Listen Later Sep 1, 2020

Link to bioRxiv paper: http://biorxiv.org/cgi/content/short/2020.09.01.277186v1?rss=1 Authors: Gai, Y., Cook, B., Satru, S., Stone, H. A., Petry, S. Abstract: The organization of microtubules (MTs) is critical for cells during interphase and mitosis. During mitotic spindle assembly, MTs are made and organized around chromosomes in a process regulated by RanGTP. The role of RanGTP has been explored in Xenopus egg extracts, which are not limited by a cell membrane. Here, we investigated whether cell-sized confinements affect the assembly of RanGTP-induced MT networks in Xenopus egg extracts. We used microfluidics to encapsulate extracts within monodisperse extract-in-oil droplets. Importantly, we find that the architecture of Ran-induced MT networks depends on the droplet diameter and the Ran concentration, and differs from structures formed in bulk extracts. Our results highlight that both MT nucleation and physical confinement play critical roles in determining the spatial organization of the MT cytoskeleton. Copy rights belong to original authors. Visit the link for more info

stone mt cook architecture copy networks confinement determines induced ran petry mts biorxiv xenopus microtubule

Behavioral assays to study neural development in Xenopus laevis tadpoles

study roberts lopez simmons copy katz behavioral waldman tadpoles assays biorxiv xenopus neural development

Play Episode Listen Later Aug 22, 2020

Link to bioRxiv paper: http://biorxiv.org/cgi/content/short/2020.08.21.261669v1?rss=1 Authors: Khakhalin, A. S., Aizenman, C. D., Lopez, V. Abstract: Escape responses, orienting reflexes, and social behaviors in Xenopus laevis tadpoles have been well documented in the literature (Lee et al. 2010; Roberts et al. 2000; Simmons et al. 2004; Katz et al. 1981; Villinger and Waldman 2012). In this article, we describe several behavioral protocols that together allow researchers efficiently (in terms of financial cost and time investment) and effectively assess developmental abnormalities in pre-metamorphic Xenopus tadpoles. Copy rights belong to original authors. Visit the link for more info

P2X receptors in Aplysia californica: Chemosensory systems, bio-energetic and development

Play Episode Listen Later Aug 10, 2020

Link to bioRxiv paper: http://biorxiv.org/cgi/content/short/2020.08.09.243196v1?rss=1 Authors: Gyori, J., Kohn, A. B., Moroz, L. L. Abstract: ATP and its ionotropic P2X receptors are components of one of the most ancient signaling systems. However, little is known about the distribution and function of purinergic transmission in invertebrates. Here, we cloned, expressed, and pharmacologically characterized P2X receptors in the sea slug Aplysia californica, a prominent model in cellular and system neuroscience. We showed that ATP and P2X receptors are essential signaling components within the unique bioenergetic center located in the CNS of Aplysia, also known as the cerebral F-cluster of insulin-containing neurons. Functional P2X receptors were successfully expressed in Xenopus oocytes to characterize their ATP-dependence (EC50 = 306uM), two-phased kinetics, ion selectivity (Na+-dependence), sensitivity to the ATP analog Bz-ATP (~20% compare to ATP) and antagonists (with PPADS as a more potent inhibitor compared to suramin). Next, using RNA-seq, we characterized the expression of P2X receptors across more than a dozen Aplysia peripheral tissues and developmental stages. We showed that P2X receptors are predominantly expressed in chemosensory structures and during early cleavage stages. The localization and pharmacology of P2X receptors in Aplysia highlight the evolutionary conservation of bioenergetic sensors and chemosensory purinergic transmission across animals. This study also provides a foundation to decipher homeostatic mechanisms in development and neuroendocrine systems. Copy rights belong to original authors. Visit the link for more info

development copy energetic atp rna cns kohn receptors biorxiv moroz xenopus

Non-canonical Hedgehog signaling regulates spinal cord and muscle regeneration

PaperPlayer biorxiv biochemistry

Play Episode Listen Later Aug 6, 2020

Link to bioRxiv paper: http://biorxiv.org/cgi/content/short/2020.08.05.238139v1?rss=1 Authors: Borodinsky, L. N., Hamilton, A. M. Abstract: Inducing regeneration in injured spinal cord represents one of modern medicine greatest challenges. Research from a variety of model organisms indicates that Hedgehog (Hh) signaling may be a useful target to drive regeneration. However, the mechanisms of Hedgehog signaling-mediated tissue regeneration remain unclear. Here we examined Hh signaling during post-amputation tail regeneration in Xenopus laevis larvae. We found that while Smoothened (Smo) activity is essential for proper spinal cord and skeletal muscle regeneration, transcriptional activity of the canonical Hh effector Gli is repressed immediately following amputation, and inhibition of Gli1/2 expression or transcriptional activity has minimal effects on regeneration. In contrast, we demonstrate that protein kinase A (PKA) is necessary for regeneration of both muscle and spinal cord, in concert with and independent of Smo respectively, and that its downstream effector CREB is activated in spinal cord following amputation. Our findings indicate that non-canonical mechanisms of Hh signaling are necessary for spinal cord and muscle regeneration. Copy rights belong to original authors. Visit the link for more info

research hamilton muscle copy regeneration hedgehog gli hh signaling canonical spinal cord regulates smo pka biorxiv xenopus creb

INTS13 Mutations Causing a Developmental Ciliopathy Disrupt Integrator Complex Assembly

Play Episode Listen Later Jul 21, 2020

Link to bioRxiv paper: http://biorxiv.org/cgi/content/short/2020.07.20.209130v1?rss=1 Authors: Mascibroda, L. G., Shboul, M., Elrod, N. D., Colleaux, L., Hamamy, H., Huang, K.-L., Peart, N. J., Singh, M. K., Lee, H., Merriman, B., Jodoin, J. N., Lee, L. A., Al-Rawashdeh, B., Ababneh, O., El-Khateeb, M., Fathalla, R., Escande-Beillard, N., Nelson, S. F., Wu, Y., Tong, L., Kenney, L. J., Russell, W. K., Amiel, J., Reversade, B., Wagner, E. J. Abstract: Oral-facial-digital syndromes (OFD) are a heterogeneous group of congenital disorders characterized by malformations of the face and oral cavity, and digit anomalies. To date, mutations in 12 ciliary-related genes have been identified that cause several types of OFD, suggesting that OFDs constitute a subgroup of developmental ciliopathies. Through homozygosity mapping and exome sequencing of two families with variable OFD type 2, we identified distinct germline mutations in INTS13, a subunit of the Integrator complex. This 14-component complex associates with RNAPII and can cleave nascent RNA to modulate gene expression. We determined that INTS13 utilizes a discrete domain within its C-terminus to bind the Integrator cleavage module, which is disrupted by the identified germline INTS13 mutations. Depletion of INTS13 disrupts ciliogenesis in human cultured cells and causes dysregulation of a broad collection of ciliary genes. Accordingly, its knockdown in Xenopus embryos lead to motile cilia anomalies. Altogether, we show that mutations in INTS13 cause an autosomal recessive ciliopathy, which reveals key interactions within Integrator components. Copy rights belong to original authors. Visit the link for more info

complex wagner copy singh causing assembly disrupt mutation rna huang wu developmental kenney tong integrator depletion merriman peart elrod amiel biorxiv xenopus ofd

In vivo imaging of microglia-mediated axonal pruning and modulation by the complement system

system copy fundamental vivo imaging pruning complement amphibians modulation depletion mediated biorxiv microglia xenopus overexpression

Play Episode Listen Later Jun 8, 2020

Link to bioRxiv paper: http://biorxiv.org/cgi/content/short/2020.06.07.087221v1?rss=1 Authors: Lim, T. K. Y., Ruthazer, E. S. Abstract: Partial phagocytosis - called trogocytosis - of axons by microglia has been documented in ex vivo preparations but has yet to be observed in vivo. Fundamental questions regarding the mechanisms that modulate axon trogocytosis as well as its function in neural circuit development remain unanswered. Here we used 2-photon live imaging of the developing Xenopus laevis retinotectal circuit to observe axon trogocytosis by microglia in vivo. Amphibian regulator of complement activation 3 (aRCA3) was identified as a neuronally expressed, synapse-associated complement inhibitory molecule. Overexpression of aRCA3 enhanced axonal arborization and inhibited trogocytosis, while expression of VAMP2-C3, a complement-enhancing fusion protein tethered to the axon surface, reduced axonal arborization. Depletion of microglia also enhanced axonal arborization and reversed the stereotypical escape behaviors to dark and bright looming stimuli. These findings demonstrate that microglia remodel axon morphology through the complement system and that neurons may control this process through expression of complement inhibitory proteins. Copy rights belong to original authors. Visit the link for more info

The role of matrix metalloproteinase-9 (MMP-9) in neurodevelopmental deficits and experience-dependent structural plasticity in Xenopus laevis tadpoles

park matrix copy cline dependent structural huang developmental deficits mmp plasticity tadpoles neurodevelopmental vpa biorxiv xenopus

Play Episode Listen Later May 31, 2020

Link to bioRxiv paper: http://biorxiv.org/cgi/content/short/2020.05.29.123661v1?rss=1 Authors: Gore, S., James, E. J., Huang, L.-C., Park, J. J., Berghella, A., Cline, H. T., Aizenman, C. D. Abstract: Matrix metalloproteinase-9 is a secreted endopeptidase targeting extracellular matrix proteins, creating permissive environments for neuronal development and plasticity. Developmental dysregulation of MMP-9 may also lead to neurodevelopmental disorders (ND). Here we test the hypothesis that chronically elevated MMP-9 activity during early neurodevelopment is responsible for neural circuit hyperconnectivity observed in Xenopus tadpoles after early exposure to valproic acid (VPA), a known teratogen associated with ND in humans. In Xenopus tadpoles, VPA exposure results in excess local synaptic connectivity, disrupted social behavior and increased seizure susceptibility. We found that overexpressing MMP-9 in the brain copies effects of VPA on synaptic connectivity, and blocking MMP-9 activity either pharmacologically or genetically reverses effects of VPA on physiology and behavior. We further show that during normal neurodevelopment MMP-9 levels are tightly regulated by neuronal activity and required for structural plasticity. These studies show a critical role for MMP-9 in both normal and abnormal development. Copy rights belong to original authors. Visit the link for more info

Developing in vivo assays for investigation of p75NTR and NRH1 transmembrane domain cleavage events using zebrafish embryos

events developing alzheimer's disease investigation copy newman vivo domain abstract embryos inhibition cleavage ntr amyloid zebrafish assays biorxiv dapt xenopus

Play Episode Listen Later May 4, 2020

Link to bioRxiv paper: http://biorxiv.org/cgi/content/short/2020.05.04.076539v1?rss=1 Authors: Jayne, T., Newman, M., Lardelli, M. Abstract: {gamma}-secretase is an important protease complex responsible for the cleavage of over 100 substrates within their transmembrane domains. {gamma}-secretase acts in Alzheimer's disease by cleavage of AMYLOID BETA (A4) PRECURSOR PROTEIN to produce aggregation-prone Amyloid beta peptide. Other {gamma}-secretase substrates such as p75NTR are also relevant to Alzheimer's disease. How {gamma}-secretase cleavage site specificity is determined is still unclear. A previous study using Xenopus laevis to investigate the proteolytic processing of p75NTR and its homolog NRH1 found that transmembrane cleavage of NRH1 was not sensitive to the {gamma}-secretase inhibitor DAPT, suggesting that it is not processed by {gamma}-secretase. To investigate this further, we identified zebrafish orthologues of the genes p75 NTR and NRH1 and developed in vivo assays to assess cleavage of the resultant p75NTR and Nrh1 proteins. Our observations from these assays in zebrafish are consistent with the Xenopus laevis study. Inhibition of {gamma}-secretase by DAPT treatment results in accumulation of uncleaved p75NTR substrate, while cleavage of Nrh1 is not affected. This supports that p75NTR is cleaved by {gamma}-secretase while Nrh1 is cleaved by a separate {gamma}-secretase-like activity. We extended our approach by generating a chimeric Nrh1 protein in which the Nrh1 transmembrane domain was replaced by that of p75NTR, in an attempt to determine whether it is the p75NTR TMD that confers susceptibility for {gamma}-secretase cleavage. Our results from analysis of this chimeric protein revealed that the p75NTR transmembrane domain alone is insufficient to confer {gamma}-secretase cleavage susceptibility. This is not completely unexpected, as there is evidence to suggest that other factors are crucial for selection/cleavage by the {gamma}-secretase complex. We have established a system in which we can now attempt to dissect the structural basis for {gamma}-secretase cleavage specificity and evolution. Copy rights belong to original authors. Visit the link for more info

2020 April No1: IDM, Ambient & Mid Era ...

Alien Air Podcast

Play Episode Listen Later Apr 3, 2020 120:22

New releases by Anthony Baldino (USA), 36 (England), Sigesmundsen (Denmark), Polwor (Chile), John Spanos (Greece), Comit (USA), AES Dana (France), Alluste (Italy), Burg (Malaysia) TIME - ARTIST - SONG - RELEASE 0:00 Intro-IDM set 0:30 Roel Funcken - boytran kovax (with Recue) - Semtinal Convex 3:17 Anthony Baldino - dust - Twelve Twenty Two 7:33 Pixelord - mage - Hypnorave 12:00 Dissolved - boleskine house blueprints - Snowy Psychoplasmics 13:56 Dissolved - Autotune ... in a lake of leeches - Snowy Psychoplasmics 19:03 36 - galatea - The Lower Lights 25:25 Sigesmundsen - pilgrim - Sofa Crash 29:45 Polwor - mais 3 (Ukyo remix) - Mais 34:10 [break] Ambient set 36:36 John Spanos - lost moments - Absence 43:30 Comit - clouded over - Remote Viewing 49:39 2814 - 新しい日の誕生 - (birth of a new day) 1:00:10 [break] Mid Era set 1:01:29 Alluste - on the wings of a dream - Aludra 1:07:03 RJ Vanderson - electronic impressions part 5 1:17:00 AES Dana - unfold - Inks 1:22:40 Burg - froesen in time - The Silent Earth 1:29:00 Merrin Karras - apex - Apex 1:33:40 Nemesis - columbia - Xenopus 1:40:10 Gert Emmens - run for your life - Dark Secrets Of The Underground 1:49:45 r.roo - somno diu erit - Deviation 1:58:00 [break] Keywords: International electronic music internet electronic artists unsigned electronic artists PsyTrance Ambient Japanese Deep Ambient IDM Psychedelic IDM Tribal TribalTrance Techno Drone

england absence apex comit nemesis burg remote viewing inks deviation dissolved silent earth xenopus aes dana pixelord roel funcken aludra

Xenobots: Living Machines

Move the human story forward! ™ ideaXme

Play Episode Listen Later Feb 20, 2020 28:59

Ira Pastor, ideaXme exponential health ambassador, interviews Dr. Josh Bongard, Professor in the Morphology, Evolution & Cognition Laboratory, Department of Computer Science, College of Engineering and Mathematical Sciences, University of Vermont. Ira Pastor Comments: On a recent ideaXme episode, we delved into the fascinating topics of "living architecture" and "living machines" and the principle of evolution in the built environment. Today, we are going continue along this unique area of the life sciences and segue into the area of "living robotics." Xenobots If you’ve been paying attention to the scientific literature over the last few weeks, you may have come across the term "Xenobots" in the press, named after the African clawed frog (Xenopus laevis). Xenobots are defined as self-healing micro-bots that are designed and programmed by a computer (via an "evolutionary algorithm") and built from the ground up using living biological cells. A Xenobot is a biological machine under 1 millimeter wide, made of heart cells (which naturally contract) and skin cells (which don’t), which are derived from stem cells harvested from Xenopus frog embryos (an extremely important model in the world of developmental biology). A team composed of scientists from both University of Vermont & Tufts University recently created these novel living machines, which were capable of moving towards a target, picking up a payload, and healing themselves after being cut, which may help increase our understanding how complex organs are formed for purposes of for regenerative medicine, and which one day, might be able to do things like safely deliver drugs inside the human body or remove artery plaques, clean radioactive wastes, collect micro-plastics in the oceans, and even maybe help colonize and terraform planets. Xenobots can walk and swim, survive for weeks without food and work together in groups, can heal on their own and keep working. Dr. Josh Bongard Today I’m joined by one of the amazing members of this Xenobot team. Dr. Josh Bongard, is Professor in the Morphology, Evolution & Cognition Laboratory, Department of Computer Science, College of Engineering and Mathematical Sciences, University of Vermont. Dr. Bongard completed his bachelors degree in Computer Science from McMaster University, Canada, his M.S. in Evolutionary & Adaptive Systems, University of Sussex, UK, his Ph.D. in Informatics, University of Zurich, Switzerland, and a post-doc in the Computational Synthesis Laboratory at Cornell University. Evolutionary Robotics Of the many fascinating things that go on in his lab, Dr. Bongard's group is focused on the unique domain of evolutionary robotics. In his evolutionary robotics work, the lab has a goal of directing the evolution of increasingly complex, capable, and autonomous machines to perform a widening array of difficult tasks and asking the broad question of "How can we automatically design a robot with little human intervention?" This work is quite cross-disciplinary in nature merges the disciplines of theoretical biology, embodied cognition, computational neuroscience, as well as psychology and philosophy. He is the co-author of the popular science books entitled "How the Body Shapes the Way We Think: A New View of Intelligence” and "Designing Intelligence: Why Brains Aren't Enough." On this show we hear from Dr. Bongard: About his background, how he developed an interest in computer science, and how he developed a passion for the convergent domains of computers and biology. The principles of "Evolutionary Algorithms" and "Artificial Ontogeny" in developing new organisms with AI. How Xenobot research can inform us as to how cells work together to form intricate complex anatomies. Future applications of Xenobots and how they inform us about non-neural intelligence and cognition dynamics. Credits: Ira Pastor interview video, text, and audio. Follow Ira Pastor on Twitter:@IraSamuelPastor If you liked this interview, be sure to check out ourinterview with Professor Dr. Rachel Armstrong, Professor of Experimental Architecture at the School of Architecture, Planning and Landscape, at Newcastle University. Follow ideaXme on Twitter:@ideaxm On Instagram:@ideaxme Find ideaXme across the internet including oniTunes,SoundCloud,Radio Public,TuneIn Radio,I Heart Radio, Google Podcasts, Spotify and more. ideaXme is a global podcast, creator series and mentor programme. Our mission: Move the human story forward!™ ideaXme Ltd.

university spotify canada ai school college living professor planning evolution united kingdom african soundcloud pastor engineering switzerland intelligence google podcasts landscape vermont architecture machines cornell university computer science zurich sussex radiopublic mcmaster university informatics tunein radio newcastle university morphology mathematical sciences ira pastor rachel armstrong xenopus living machines experimental architecture evolutionary algorithms

Biorobots, The Math Of Life, Science Comics. Jan 17, 2020, Part 2

Science Friday

Play Episode Listen Later Jan 17, 2020 47:57

Living Robots, Designed By Computer Researchers have used artificial intelligence methods to design ‘living robots,’ made from two types of frog cells. The ‘xenobots,’ named for the Xenopus genus of frogs, can move, push objects, and potentially carry materials from one place to another—though the researchers acknowledge that much additional work would need to be done to make the xenobots into a practical tool. The research was published in the Proceedings of the National Academy of Sciences. Josh Bongard, a professor of computer science at the University of Vermont and co-author of the report, joins Ira to talk about designing cell-based structures and next steps for the technology. The Math Behind Big Decision Making What does it mean for your health if a cancer screening is 90% accurate? Or when a lawyer says there’s a 99% chance a defendant is guilty? We encounter numbers in our everyday lives that can influence how we make big decisions, but what do these numbers really tell us? Mathematical biologist explores these concepts and patterns in his book The Math of Life and Death: 7 Mathematical Principles That Shape Our Lives. He joins Ira to talk about the hidden math principles that are used in medicine, law, and in the media and how the numbers can be misused and correctly interpreted. The Science Comics Of Rosemary Mosco Have you ever wondered what a Great Blue Heron would write in a love letter to a potential mate? Or what the moons of Mars think of themselves? These are the scenes that nature cartoonist Rosemary Mosco dreams up in her comic Bird and Moon. “Nature is really funny. It’s never not funny,” Mosco says in SciFri’s latest SciArts video. “You can go into the woods and find 20 or 30 hilarious potential comic prompts anywhere you go.” Viewers may come for the laughs, but they will end up learning facts, she explains. Mosco talks about her inspiration for finding the funny side of snakes, planets, and nature, and how she uses humor to communicate science.

More Flashcards: Hidden Powers Unleashed | Episode 59

The A&P Professor

Play Episode Listen Later Dec 30, 2019 53:00

Second of three episodes about flashcards reveals more behind the use of this tool for learning anatomy & physiology. The term pseudogene may cause problems. A junk-DNA analogy. Bonus track: Delta Wave Radio Hour. 00:47 | Pseudogenes 08:10 | Sponsored by AAA 08:49 | Pseudogene Analogy 12:35 | Sponsored by HAPI 13:18 | Need Some Sleep? 18:20 | Sponsored by HAPS 19:08 | Flashcards Again 28:16 | Survey Says... 29:21 | Flashcard Learning Tricks 43:05 | More Flashcards 34:31 | Staying Connected 46:26 | Delta Wave Radio Hour (BONUS) If you cannot see or activate the audio player click here. Please take the anonymous survey: theAPprofessor.org/survey Questions & Feedback: 1-833-LION-DEN (1-833-546-6336) Follow The A&P Professor on Twitter, Facebook, Blogger, Nuzzel, Tumblr, or Instagram! Pseudogenes 7.5 minutes Are we doing our students the best service by emphasizing the classic definition of a pseudogene as a gene "without function?" Discuss. Pseudogene word dissection found in Preview Episode 59 Overcoming challenges and dogmas to understand the functions of pseudogenes (journal perspective article from Nature Reviews Genetics) my-ap.us/2PMX3DW A pseudogene structure in 5S DNA of Xenopus laevis (research article in Cell using "pseudogene" for the first time) my-ap.us/2ZfqW2R Pseudogene use history in books (from Google Ngram Viewer) my-ap.us/2Q6UdJ7 Improbable Destinies: Fate, Chance, and the Future of Evolution by Jonathan B. Losos amzn.to/2L9fzCE Browse The A&P Professor Book Club https://theapprofessor.org/bookclub.html Sponsored by AAA 0.5 minutes A searchable transcript for this episode, as well as the captioned audiogram of this episode, are sponsored by the American Association for Anatomy (AAA) at anatomy.org. Searchable transcript Captioned audiogram Pseudogene Analogy 3.5 minutes Junk DNA, or pseudogenes, is a rather abstract concept for beginning learners, so perhaps an analogy is in order. Sponsored by HAPI Online Graduate Program 0.5 minute The Master of Science in Human Anatomy & Physiology Instruction—the MS-HAPI—is a graduate program for A&P teachers. A combination of science courses (enough to qualify you to teach at the college level) and courses in contemporary instructional practice, this program helps you power up your teaching. Kevin Patton is a faculty member in this program. Check it out! nycc.edu/hapi Need Some Sleep? 5 minutes Sleep science suggests that podcasts can be useful in helping us fall asleep. This podcast may be especially useful as a safe and effective sleep aid. Listen to this segment to find out why. If you can stay awake for it. Science Supports Your Habit of Falling Asleep to Stupid Podcasts (feature health article) my-ap.us/34GOajz The influence of white noise on sleep in subjects exposed to ICU noise (study of white noise to help induce sleep) my-ap.us/34MF8BR Sleep With Me (podcast specifically for sleep inducement) my-ap.us/35LPKST Sleep Headphones Wireless, Perytong Bluetooth Sports Headband Headphones with Ultra-Thin HD Stereo Speakers Perfect for Sleeping,Workout,Jogging,Yoga,Insomnia, Air Travel, Meditation amzn.to/36W3p9W Sponsored by HAPS 1 minute The Human Anatomy & Physiology Society (HAPS) is a sponsor of this podcast. You can help appreciate their support by clicking the link below and checking out the many resources and benefits found there. Don't forget the HAPS Awards, which provide assistance for participating in the HAPS Annual Conference. Anatomy & Physiology Society theAPprofessor.org/haps Flashcards Again 9 minutes Part of our role as teachers is to be learning therapists who help our students diagnose barriers to learning and then develop effective treatment plans to become better learners. Flashcards: Hidden Powers | Episode 58 Survey Says... 1 minute Please take about 5 minutes to answer some questions—it will really help improve this podcast! theAPprofessor.org/survey Flashcard Learning Tricks 13.5 minutes Building on Flashcards: Hidden Powers | Episode 58, Kevin discusses using images, color coding, the beauty of plaid flashcards (ahem), and the layering (interleaving) effect. Six a Day (blog article for A&P students) my-ap.us/2Z4Y5OV Learn how to Study Using... Retrieval Practice (blog article for any student) my-ap.us/35GW5Ph More Flashcards 1.5 minutes Yep, there's more about flashcards coming in the third part of this series. Check out Episode 60 when the time comes. As promised, I reveal the secret of the levitating flashcard. But the only way to access this video is by using the TAPP app, where the bonus video resides. Plays episodes of this podcast Plus bonus material (PDF hanounds, images, videos) Free of charge Lots of great features and functionality Easy way to share this podcast Even folks who don't know how to access a podcast can download an app Getting the TAPP app Search "The A&P Professor" in your device's app store iOS devices: my-ap.us/TAPPiOS Android devices: my-ap.us/TAPPandroid Kindle Fire: amzn.to/2rR7HNG Delta Wave Radio Hour 6.5 minutes Need to fall asleep fast? Listen to Dr. ZZzzz drone on about Influenza, using information from the CDC, in this popular fictional podcast. Please do not drive or operate machinery while listening to this bonus track after the episode close. Dedicated to Dic and Ellen. If the hyperlinks here are not active, go to TAPPradio.org to find the episode page. More details at the episode page. Transcript available at the episode transcript window. Listen to any episode on your Alexa device. Need help accessing resources locked behind a paywall? Check out this advice from Episode 32 to get what you need! https://youtu.be/JU_l76JGwVw?t=440 Tools & Resources Amazon TextExpander Rev.com Snagit & Camtasia The A&P Professor Logo Items Sponsors Transcript and captions for this episode are supported by the American Association for Anatomy. anatomy.org The Human Anatomy & Physiology Society also provides marketing support for this podcast. theAPprofessor.org/haps Distribution of this episode is supported by NYCC's online graduate program in Human Anatomy & Physiology Instruction (HAPI) nycc.edu/hapi Clicking on sponsor links helps let them know you appreciate their support of this podcast! Follow The A&P Professor on Twitter, Facebook, Blogger, Nuzzel, Tumblr, or Instagram! The A&P Professor® and Lion Den® are registered trademarks of Lion Den Inc. (Kevin Patton)

Richard Harland Part 1: Early Frog Development: How to Make a Tadpole

iBiology Videos

Play Episode Listen Later Aug 8, 2019 24:57

Richard Harland begins his talk by asking how a fertilized egg goes from a single cell to a complex, multicellular organism during vertebrate development. He explains that amphibians, and in particular Xenopus laevis, are an excellent system for addressing this question. For example, early experiments by Spemann and Mangold in newt embryos were the first to demonstrate the presence of an “organizer” region, and more recent studies in Xenopus have identified many signaling molecules that control embryogenesis. Throughout his talk, Harland shows stunning movies to illustrate the beauty and complexity of early frog development.

development frogs mangold harland tadpoles xenopus richard harland

17. Ghost in the half-shell

Researchat.fm

Play Episode Listen Later Jul 15, 2019 69:03

カルビーの新ジャガイモ・ぽろしりの凄さ、個体サイズと染色体数・細胞数の関係性、バオバブバー閉店、世界の武器、象、ゲーム開発や研究における職人技について話しました。Show notes ぽろしり…品種改良によって新しく誕生したぽろしりについてぽろしりの開発…カルビーにおける馬鈴薯の開発について倍数体…染色体数の倍数性を持つ個体のこと。2nより大きい3n, 4n, 6n, 8n, 12nなどの染色体数をもつ倍数体のことを多倍体と一般的に呼ぶ Shifting the limits in wheat research and breeding using a fully annotated reference genome…小麦ゲノムの解読に関するサイエンスの論文トランスポゾン動く遺伝因子とトウモロコシ　～深ーい研究の歴史と現在～ POLYPLOIDY IN THE SALAMANDER, EURYCEA BISLINEATA …Fankhauserによるサラマンダーの実験 (1939年) コモドオオトカゲ Nucleus-to-cytoplasm ratio Genome evolution in the allotetraploid frog Xenopus laevis…アフリカツメガエルのゲノム解読に関する論文 Xenopus ruwenzoriensis…ウガンダツメガエル。脅威のdodecaploidy(12n、十二倍体)の染色体を持つ。染色体数の記述としては2n=108。 The fate of duplicated immunity genes in the dodecaploid Xenopus ruwenzoriensis.…貴重な写真付き。ウガンダツメガエル(2n=108)と他のアフリカツメガエルの比較あり。Xenopus tropicalis(二倍体, 2n = 20)とは近い大きさ。Xenopus laevis (異質四倍体, 2n = 36)の方が大きい。ただ、ポッドキャスト内で話したようにおたまじゃくしの大きさを比較した方が、発生生物学的には意味がある(成体はどんどん成長してしまうので)。異質倍数体… 2種類以上のゲノムで構成されている倍数体。パラケルスス…鋼の錬金術師の主人公のファミリーネーム「ホーエンハイム」もパラケルススが元ネタだったりします。クセノフィオフォラ…体長数mmから数十cmの巨大な単細胞の原生動物バオバブにあるバー…南アフリカ共和国に存在する樹齢6000年のバオバブに作られたバー。通称Pub tree。この記事では樹齢6000年のバオバブにつくられたバーとなっている。 Sunland Baobab: サンランドバオバブ…このバーが存在していたバオバブの木。現在、既に木は大破してしまい、このバーは存在していない。2016年と2017年に大破してしまったらしい。 Age determination of large live trees with inner cavities: radiocarbon dating of Platland tree, a giant African baobab…サンランドバオバブの年齢を放射年代測定によって推定した論文。1060歳+-75歳とされている。マスターキートン: 砂漠のカーリマン(Amazon) 「砂漠ではスーツがいい」は本当かトマホーク (Wikipedia) Harvard Museum of Natural History Peabody Museum of Archaeology and Ethnology ハルバード (Wikipedia) ショーテル (Wikipedia) DARK SOULS (Wikipedia) カンナエの戦い(包囲殲滅戦) (Wikipedia) ハンニバル (Wikipedia) ヌミディア (Wikipedia) スキピオ (Wikipedia) マケドニア (Wikipedia) カルタゴ (Wikipedia) ザマの戦い (Wikipedia) 戦象 (Wikipedia) チャトランガ (Wikipedia) シャンチー (Wikipedia) ナーシャ・ジベリ (Wikipedia)… FFシリーズや聖剣伝説に携わった天才プログラマ。ポッドキャスト内ではレストランを経営しているといったが明確なソースはなく、現在の活動は不明。ナーシャ・ジベリの偉業 FF3の飛空挺 Final Fantasy トルネコの大冒険 (Wikipedia) 「不思議のダンジョン」の絶妙なゲームバランスは、たった一枚のエクセルから生み出されている！？ Transfer-messenger RNA, tRNA (Wikipedia) BLAST (Basic Local Alignment Search Tool)…相同なDNA塩基を検索するためのツール。バイオインフォマティクスにとっては最も重要なツールである。目BLAST…職人芸。研究者の一部には、DNAを配列同士を見比べるだけで相同検索ができる(といわれている都市伝説的な、もしくは見栄を張って自称している)人たちがいる。共感覚との関係性に興味がある。転じて、文章の相同性を目で検索する時にも使われる(レポートのコピペなど)。 RNAの二次構造…RNAやDNAは相補的な塩基同士によって特徴的な二次構造を取る。 Dot-bracket format…RNAの二次構造の表現方法の一つ。podcast中ではちゃんと答えられませんでしたが拡張版のExtended Dot-braketを使えばpseudo-knotなども表現可能です。他にもStockholm formatなど、いろいろあります。 Dot-braket formatの例…大腸菌のAla-tRNAの例。tRNAはわかりやすいので訓練におすすめです。例えば右のような感じ： (((((((..((((........)))).(((((.......))))).....(((((.......)))))))))))).... RNA fold…RNA二次構造の予測ソフトウェアの一つ。Webから利用できる。 SPY×FAMILY Editorial notes 台本のないゆるふわトークでも案外みんなの引き出しが多くていけるものですな (soh) エンジニアが投げてくるのはマサカリだった気もしますが、トマホークの方が投げやすそうなのでセーフということで！(coela) 私の体の脂肪は、4倍体になったから大きくなったわけではありません (tadasu)

DNA replication and repair in vertebrate cells

IFOM 2015

Play Episode Listen Later Aug 9, 2017 7:56

Dr Costanzo talks to ecancertv at IFOM EMBL about vertebrate genome stability, focusing on the DNA replication and repair in vertebrate cells. Additionally he discusses his research using extracts derived from Xenopus laevis eggs, which allow extensive biochemical analysis which can be reproduced in vitro complex cell cycle events such as chromatin formation, nuclear assembly, semi-conservative DNA replication, chromosome assembly and mitotic spindle formation.

dna repair cells costanzo vertebrates xenopus dna replication

biosights: June 6, 2016

Crisis and Social Change: towards alternative horizons

Play Episode Listen Later Jun 6, 2016 7:34

Neural crest cells stay within versican's confines Spatial confinement enhances collective cell migration in vitro, but whether it promotes collective migration in vivo is unclear. Szabó et al. reveal that the extracellular matrix protein versican confines neural crest cells to enhance their collective migration during Xenopus laevis embryogenesis. This biosights episode presents the paper by Szabó et al. from the June 6th, 2016, issue of The Journal of Cell Biology and includes an interview with the paper's senior author, Roberto Mayor (University College London, London, England, UK). Produced by Caitlin Sedwick and Ben Short. See the associated paper in JCB for details on the funding provided to support this original research. Subscribe to biosights via iTunes or RSS View biosights archive The Rockefeller University Press biosights@rockefeller.edu

uk england journal spatial neural cell biology szab jcb xenopus

Guest Speaker Dr. Eben Kirksey - The Xenopus Pregnancy Test: A Performative Experiment

Play Episode Listen Later May 27, 2015 82:00

An open seminar sponsored by the Reproductive Sociology Research Group (ReproSoc). Filmed on 22nd May 2015.

experiments pregnancy anthropology filmed reproduction speaker dr performative ethnography pregnancy tests xenopus bioart eben kirksey

biosights: March 16, 2015

Play Episode Listen Later Mar 16, 2015 7:56

PAPC separates tissues at a Snail's pace Brachet's cleft separates the ectoderm and mesoderm of early Xenopus and zebrafish embryos. Luu et al. reveal that, in conjunction with the transcription factor Snail1, the protocadherin PAPC promotes tissue separation by down-regulating planar cell polarity proteins at the ectoderm-mesoderm boundary. This biosights episode presents the paper by Luu et al. from the March 16, 2015, issue of The Journal of Cell Biology and includes an interview with one of the paper's senior authors, Rudolf Winklbauer (University of Toronto, Toronto, Canada). Produced by Caitlin Sedwick and Ben Short. See the associated paper in JCB for details on the funding provided to support this original research. Subscribe to biosights via iTunes or RSS View biosights archive The Rockefeller University Press biosights@rockefeller.edu

canada toronto journal snail cell biology jcb luu disheveled xenopus frizzled

biosights: July 7, 2014

Play Episode Listen Later Jul 7, 2014 8:14

The fluid dynamics of collective cell migration During development and tumor metastasis, cells prepare to migrate by undergoing an epithelial-to-mesenchymal transition that loosens their connections to neighboring cells. But some cell types then migrate en masse to their final destinations, indicating that their intercellular adhesions aren't disrupted completely. Kuriyama et al. reveal that the phospholipid lysophosphatidic acid promotes the collective migration of Xenopus neural crest cells by downregulating the surface expression of N-cadherin, granting the cells fluid-like properties that enhance their movement through embryonic tissues. This biosights episode presents the paper by Kuriyama et al. from the July 7, 2014, issue of The Journal of Cell Biology and includes an interview with senior author Roberto Mayor (University College London, UK). Produced by Caitlin Sedwick and Ben Short. See the associated paper in JCB for details on the funding provided to support this original research. Subscribe to biosights via iTunes or RSS View biosights archive The Rockefeller University Press biosights@rockefeller.edu

uk journal emt cell biology jcb lpa metastasis xenopus

biosights: April 15, 2013

Medizin - Open Access LMU - Teil 20/22

Play Episode Listen Later Apr 15, 2013 6:46

Frog oocytes evade the checkpoint Most dividing cells possess a spindle assembly checkpoint that prevents them from entering anaphase until all their chromosomes are correctly attached to the metaphase spindle. Shao et al. reveal that Xenopus eggs lack this checkpoint, allowing them to undergo meiosis in the absence of microtubules or in the presence of monopolar spindles. This biosights episode presents the paper by Shao et al. from the April 15, 2013 issue of The Journal of Cell Biology and includes an interview with senior author Johné Liu (Ottawa Hospital Research Institute, Canada). Produced by Caitlin Sedwick and Ben Short. See the associated paper in JCB for details on the funding provided to support this original research. Subscribe to biosights via iTunes or RSS View biosights archive The Rockefeller University Press biosights@rockefeller.edu

canada journal frogs cell biology shao jcb meiosis xenopus oocytes

Suv4-20h Histone Methyltransferases Promote Neuroectodermal Differentiation by Silencing the Pluripotency-Associated Oct-25 Gene

Play Episode Listen Later Jan 1, 2013

Post-translational modifications (PTMs) of histones exert fundamental roles in regulating gene expression. During development, groups of PTMs are constrained by unknown mechanisms into combinatorial patterns, which facilitate transitions from uncommitted embryonic cells into differentiated somatic cell lineages. Repressive histone modifications such as H3K9me3 or H3K27me3 have been investigated in detail, but the role of H4K20me3 in development is currently unknown. Here we show that Xenopus laevis Suv4-20h1 and h2 histone methyltransferases (HMTases) are essential for induction and differentiation of the neuroectoderm. Morpholino-mediated knockdown of the two HMTases leads to a selective and specific downregulation of genes controlling neural induction, thereby effectively blocking differentiation of the neuroectoderm. Global transcriptome analysis supports the notion that these effects arise from the transcriptional deregulation of specific genes rather than widespread, pleiotropic effects. Interestingly, morphant embryos fail to repress the Oct4-related Xenopus gene Oct-25. We validate Oct-25 as a direct target of xSu4-20h enzyme mediated gene repression, showing by chromatin immunoprecipitaton that it is decorated with the H4K20me3 mark downstream of the promoter in normal, but not in double-morphant, embryos. Since knockdown of Oct-25 protein significantly rescues the neural differentiation defect in xSuv4-20h double-morphant embryos, we conclude that the epistatic relationship between Suv4-20h enzymes and Oct-25 controls the transit from pluripotent to differentiation-competent neural cells. Consistent with these results in Xenopus, murine Suv4-20h1/h2 double-knockout embryonic stem (DKO ES) cells exhibit increased Oct4 protein levels before and during EB formation, and reveal a compromised and biased capacity for in vitro differentiation, when compared to normal ES cells. Together, these results suggest a regulatory mechanism, conserved between amphibians and mammals, in which H4K20me3-dependent restriction of specific POU-V genes directs cell fate decisions, when embryonic cells exit the pluripotent state.

global consistent promote medizin silencing differentiation eb repressive histone xenopus ptms h3k27me3

Mass spectrometric analysis of global histone modification profiles during xenopus laevis development

Medizinische Fakultät - Digitale Hochschulschriften der LMU - Teil 14/19

Play Episode Listen Later May 3, 2012

Vertebrate embryos are derived from a transitory pool of pluripotent embryonic cells. By the process of induction, these precursor cells are assigned to specific fates and differentiation programs. Histone post-translational modifications are thought to play a key role in the establishment and maintenance of stable gene expression patterns underlying these processes. While at gene level histone modifications are known to change during differentiation, very little is known about the quantitative fluctuations in bulk histone modifications during development. To investigate this issue histones isolated from four different developmental stages of Xenopus laevis were analysed by mass spectrometry. Initally, a variety of different protocols for histone extraction from Xenopus laevis embryos and stable cell lines was tested and evaluated. Since non of the available methods worked sufficiently, a new reliable and effective protocol for nuclei preparation and histone extraction was established. Using mass spectrometry, core histone modifications were unambiguously determined. The techniques for identification and quantification of histone modifications by tandem mass spectrometry were improved as well. In total, an average sequence coverage of 68% of modification sites for the four core histones was achived by tryptic digestion after covalent modification of lysine residues with propionic anhydride. Using both LC-MS/MS and MALDI-TOF mass spectrometry, a total number of 2 modifications of H2A and 3 modifications H2B, 39 modifications of H3 and 20 modifications of H4 were identified and quantified. During this developmental period, an increase in the unmodified states, and a shift from histone modifications associated with transcriptionally active to transcriptionally repressive histone marks, was observed. Furthermore, these naturally occurring histone modifications were compared to the histone modifications of murine ES cells, detecting large differences in the methylation patterns of lysines 27 and 36 of histone H3 between pluripotent cells from Xenopus blastulae and murine ES cells. By combining all detected modification transitions, their patterns could be clustered according to their embryonic origin, defining specific histone modification profiles for each developmental stage. These specific histone modification profiles indicated a stepwise maturation of the embryonic epigenome, which may be cause to the progressing restriction of cellular potency during development. This thesis has revealed major quantitative shifts for several histone modifications known to be involved in gene regulation and furthermore enabled the definition of stage specific histone modification profiles accompanying and potentially regulating the transition from pluripotent to determined cell states using an antibody-independent method.

global development mass profiles modification h3 h2a vertebrates h2b h4 histone xenopus lc ms ms maldi tof ddc:600

Function of the CHD4/Mi-2ß chromatin remodelling ATPase during neural development of Xenopus laevis

Medizinische Fakultät - Digitale Hochschulschriften der LMU - Teil 13/19

Play Episode Listen Later Jan 31, 2012

Tue, 31 Jan 2012 12:00:00 +0100 https://edoc.ub.uni-muenchen.de/13954/ https://edoc.ub.uni-muenchen.de/13954/1/Nieberler_Markus.pdf Nieberler, Markus ddc:610,

function chromatin remodelling atpase xenopus neural development ddc:600

Heat-shock mediated overexpression of HNF1β mutations has differential effects on gene expression in the Xenopus pronephric kidney.

Medizin - Open Access LMU - Teil 18/22

Play Episode Listen Later Jan 1, 2012

The transcription factor HNF1B, encoded by the TCF2 gene, plays an important role in the organogenesis of vertebrates. In humans, heterozygous mutations of HNF1B are associated with several diseases, such as pancreatic β-cell dysfunction leading to maturity-onset diabetes of the young (MODY5), defective kidney development, disturbed liver function, pancreas atrophy, and malformations of the genital tract. The African claw frog Xenopus laevis is an excellent model to study the processes involved in embryogenesis and organogenesis, as it can be manipulated easily with a series of methods. In the present study, we overexpressed HNF1β mutants in the developing Xenopus embryo to assess their roles during organogenesis, particularly in the developing pronephric kidney. Towards this goal, we developed a heat-shock inducible binary Cre/loxP system with activator and effector strains. Heat-shock activation of the mutant HNF1B variants P328L329del and A263insGG resulted in malformations of various organs and the affected larvae developed large edemas. Defects in the pronephros were primarily confined to malformed proximal tubules. Furthermore, the expression of the proximal tubule marker genes tmem27 and slc3a1, both involved in amino acid transport, was affected. Both P328L329del and A263insGG downregulated expression of slc3a1. In addition, P328L329del reduced tmem27 expression while A263insGG overexpression decreased expression of the chloride channel clcnk and the transcription factor pax2. Overexpression of two mutant HNF1B derivatives resulted in distinct phenotypes reflected by either a reduction or an enlargement of pronephros size. The expression of selected pronephric marker genes was differentially affected upon overexpression of HNF1B mutations. Based on our findings, we postulate that HNF1B mutations influence gene regulation upon overexpression in specific and distinct manners. Furthermore, our study demonstrates that the newly established Cre/loxP system for Xenopus embryos is an attractive alternative to examine the gene regulatory potential of transcription factors in developing pronephric kidney as exemplified here for HNF1B.

african heat effects shock medizin kidney mutation defects differential mediated gene expression xenopus overexpression cre loxp

On the function of Xenopus Oct4 protein homologs: Molecular construction of dominant interference variants and functional analysis in early frog development

Medizinische Fakultät - Digitale Hochschulschriften der LMU - Teil 13/19

Play Episode Listen Later Oct 13, 2011

Embryonic development represents a sophisticated multistep process. Hereby, specification, patterning and differentiation of cells and tissue need to be extremely well regulated in a temporo-spatial manner. This is based on repression and activation of a vast number of cell-type specific genes, but only a small number of transcription factors seem to be responsible for their regulation. The transcription factor network of Oct4, Sox2 and Nanog are thought to play an essential role in the maintenance of pluripotency and in timing the onset of differentiation. The importance of mouse Oct4 in the regulation of pluripotency is underscored by recent findings providing evidence that Oct4 is essential for reprogramming somatic cells. Nevertheless, little is known on the molecular function of this transcription factor during normogenesis. Given the extra uterine development of the embryos, the well-studied early development and the established manipulation methods like injection of RNA or DNA, Xenopus leavis offers an ideal model organism to study the role of Oct4 homologs in early development. In Xenopus laevis three Oct4 paralogs – Oct25, Oct60 and Oct91 – are known, which are similar in size and have a high sequence homology compared to mammalian Oct4. There are strong evidences that Xenopus Oct proteins and mammalian Oct4 share similar functions. To gain further insights into the function of Oct proteins I generated dominant activating- (VP16-Oct60), dominant repressing- (EnR-Oct60) and hormone inducible (GR-Oct60) transcription factor variants for all three Xenopus Oct proteins. Protein expression was verified in vitro as well as in vivo. Oct60 shows a unique expression pattern among Xenopus Oct proteins: Oct60 is maternally transcribed and its RNA is detectable in mature oocytes. Expression is downregulated in the gastrula, when the expression of other Xenopus POU proteins begins. Therefore, it is one of the earliest genes to be expressed. I decided to concentrate first efforts on Oct60. The transactivating functions of the Oct60 G.o.F. variants were tested in a luciferase assay on two different Oct4 reporter constructs in vivo. Oct60 and VP16-Oct60 acted as strong activators whereas EnR-Oct60 repressed both reporter constructs. By overexpression of Oct60 and its G.o.F. variants, several phenotypes were observed that affected distinct parts of the body. Beside impaired head differentiation, observed by overexpression of VP16-Oct60 and Oct60, a strong hyperpigmentation was observed by injection of EnR-Oct60 and Oct60. Additionally, EnR-Oct60 injected embryos showed hyperpigmented outgrowths in the trunk region. All injected embryos possessed a shortened body axis that was specifically curved depending on the injected mRNA. In situ hybridizations were performed to investigate the molecular mechanism of the observed phenotypic changes. Experiments revealed that all examined constructs promote neuroectodermal fate while repressing mesoderm formation. These results indicate that Oct60 plays an important role in the induction and specification of germ layer formation. By cloning and testing these different G.o.F. variants I accomplished to obtain important tools for further dissecting the molecular function of Oct4 homologs in Xenopus embryos.

development dna experiments construction frogs protein expression dominant mrna molecular rna variants interference embryonic functional analysis xenopus sox2 ddc:600 nanog

Weakness of innate immunity also contributes to susceptibility of Xenopus tadpoles to FV3 infection

2011 International Ranavirus Symposium

Play Episode Listen Later Jul 28, 2011 13:10

weakness infection contributes tadpoles susceptibility innate immunity xenopus

Complex role of macrophages in Xenopus immune defenses and persistence of the ranavirus FV3

2011 International Ranavirus Symposium

Play Episode Listen Later Jul 28, 2011 15:05

complex persistence immune defenses macrophages xenopus

Four and a half LIM protein 1C (FHL1C)

Medizin - Open Access LMU - Teil 17/22

Play Episode Listen Later Jan 1, 2011

Four-and-a-half LIM domain protein 1 isoform A (FHL1A) is predominantly expressed in skeletal and cardiac muscle. Mutations in the FHL1 gene are causative for several types of hereditary myopathies including X-linked myopathy with postural muscle atrophy (XMPMA). We here studied myoblasts from XMPMA patients. We found that functional FHL1A protein is completely absent in patient myoblasts. In parallel, expression of FHL1C is either unaffected or increased. Furthermore, a decreased proliferation rate of XMPMA myoblasts compared to controls was observed but an increased number of XMPMA myoblasts was found in the G(0)/G(1) phase. Furthermore, low expression of K(v1.5), a voltage-gated potassium channel known to alter myoblast proliferation during the G(1) phase and to control repolarization of action potential, was detected. In order to substantiate a possible relation between K(v1.5) and FHL1C, a pull-down assay was performed. A physical and direct interaction of both proteins was observed in vitro. In addition, confocal microscopy revealed substantial colocalization of FHL1C and K(v1.5) within atrial cells, supporting a possible interaction between both proteins in vivo. Two-electrode voltage clamp experiments demonstrated that coexpression of K(v1.5) with FHL1C in Xenopus laevis oocytes markedly reduced K(+) currents when compared to oocytes expressing K(v1.5) only. We here present the first evidence on a biological relevance of FHL1C.

protein medizin mutation lim xenopus

Stage-specific histone modification profiles reveal global transitions in the Xenopus embryonic epigenome.

Medizin - Open Access LMU - Teil 17/22

Play Episode Listen Later Jan 1, 2011

Vertebrate embryos are derived from a transitory pool of pluripotent cells. By the process of embryonic induction, these precursor cells are assigned to specific fates and differentiation programs. Histone post-translational modifications are thought to play a key role in the establishment and maintenance of stable gene expression patterns underlying these processes. While on gene level histone modifications are known to change during differentiation, very little is known about the quantitative fluctuations in bulk histone modifications during development. To investigate this issue we analysed histones isolated from four different developmental stages of Xenopus laevis by mass spectrometry. In toto, we quantified 59 modification states on core histones H3 and H4 from blastula to tadpole stages. During this developmental period, we observed in general an increase in the unmodified states, and a shift from histone modifications associated with transcriptional activity to transcriptionally repressive histone marks. We also compared these naturally occurring patterns with the histone modifications of murine ES cells, detecting large differences in the methylation patterns of histone H3 lysines 27 and 36 between pluripotent ES cells and pluripotent cells from Xenopus blastulae. By combining all detected modification transitions we could cluster their patterns according to their embryonic origin, defining specific histone modification profiles (HMPs) for each developmental stage. To our knowledge, this data set represents the first compendium of covalent histone modifications and their quantitative flux during normogenesis in a vertebrate model organism. The HMPs indicate a stepwise maturation of the embryonic epigenome, which may be causal to the progressing restriction of cellular potency during development.

stage reveal medizin profiles modification h3 embryonic vertebrates h4 epigenome histone xenopus global transitions

A Role for All-Trans-Retinoic Acid in the Early Steps of Lymphatic Vasculature Development

Medizin - Open Access LMU - Teil 17/22

Play Episode Listen Later Jan 1, 2011

The molecular mechanisms that regulate the earliest steps of lymphatic vascular system development are unknown. To identify regulators of lymphatic competence and commitment, we used an in vitro vascular assay with mouse embryonic stem cell-derived embryoid bodies (EBs). We found that incubation with retinoic acid (RA) and, more potently, with RA in combination with cAMP, induced the expression of the lymphatic competence marker LYVE-1 in the vascular structures of the EBs. This effect was dependent on RA receptor (RAR)-alpha and protein kinase A signaling. RA-cAMP incubation also promoted the development of CD31+/LYVE-1+/Prox1+ cell clusters. In situ studies revealed that RAR-alpha is expressed by endothelial cells of the cardinal vein in ED 9.5-11.5 mouse embryos. Timed exposure of mouse and Xenopus embryos to excess of RA upregulated LYVE-1 and VEGFR-3 on embryonic veins and increased formation of Prox1-positive lymphatic progenitors. These findings indicate that RA signaling mediates the earliest steps of lymphatic vasculature development. Copyright (C) 2010 S. Karger AG, Basel

development camp trans ra acid medizin basel lymphatic rar ebs lyve xenopus vegfr copyright c vasculature prox1 karger ag

biosights: December 27, 2010

germany journal dynamic modeling numa heidelberg cell biology loughlin embl xenopus microtubules

Play Episode Listen Later Dec 27, 2010 7:05

Dynamic microtubules assemble into a steady state bipolar spindle structure but precisely how this is achieved is unclear. Loughlin et al. develop a computational model that predicts how a few key activities organize microtubules in Xenopus meiotic spindles. This biosights episode presents the paper by Loughlin et al. from the December 27, 2010 issue of the Journal of Cell Biology, and includes an interview with author François Nédélec (EMBL, Heidelberg, Germany). Produced by Caitlin Sedwick and Ben Short. Subscribe to biosights via iTunes or RSS View biosights archive The Rockefeller University Press biosights@rockefeller.edu

Lecture 2 - The African Clawed Frog, Xenopus Laevis

Neuroscience - Frontiers of Science

Play Episode Listen Later Sep 29, 2010 1:56

african frogs lecture clawed xenopus

Lecture 2 - Xenopus Laevis as a Model Organism

Neuroscience - Frontiers of Science

Play Episode Listen Later Sep 29, 2010 3:21

model lecture organisms xenopus

Regulation of AMPA receptor function and synaptic localization by stargazin and PSD-95

Fakultät für Biologie - Digitale Hochschulschriften der LMU - Teil 03/06

Play Episode Listen Later Mar 30, 2009

The majority of excitatory transmission in the brain is mediated by glutamatergic synapses. Rapid synaptic signaling is mediated by AMPA and kainate receptors, whereas NMDA receptors mediate slow synaptic currents. Pathophysiological activation of glutamatergic neurons can lead to excitotoxicity and neuronal death, for example in ischaemia and neurodegenerative disorders. Therefore, studying the structure and function of AMPA receptors is important for understanding general mechanisms of synaptic transmission as well as for the development of new therapies. AMPA receptors are associated with auxiliary subunits called Transmembrane AMPA Receptor Regulatory Proteins (TARPs). The first identified member of this family was stargazin. Given the structural similarity to the γ1 subunit of skeletal muscle voltage-gated Ca2+channels, stargazin is also called γ2. The stargazer mouse is a spontaneous mutant that lacks AMPA receptors in granule cells of cerebellum and suffers from ataxia. In addition to stargazin, the family includes γ3, γ4 and γ8. TARPs regulate all aspects of AMPA receptor function - from early steps of synthesis and trafficking to the cell surface, to synaptic localization and biophysical properties. TARPs interact with PSD-95, a main scaffolding protein of excitatory synapses that belongs to the Membrane-Associated Guanylate Kinases (MAGUK) family. Via this interaction AMPA receptors are localized to the synapse. PSD-95 clusters many other synaptic proteins and organizes signaling complexes in the synapse. The goal of this thesis was to investigate the role of stargazin in regulating the antagonism of AMPA receptors. I focused on the commonly used antagonists CNQX, GYKI-53655 (GYKI) and CP-465,022 (CP) and explored how stargazin changes the inhibition of AMPA receptors by these drugs. The second goal was to assess the role of PSD-95 in synaptic function. More specifically, I aimed to investigate how an increased level of PSD-95 in a neuron affects AMPA and NMDA currents, as well as the presynaptic function of a neuron. In the first part of my thesis I used the heterologous Xenopus oocyte expression system to express AMPA receptor subunits alone or with stargazin. Using the two-electrode voltage clamp, I measured the glutamate-evoked currents and obtained dose-response curves for CNQX, GYKI and CP. I found that stargazin decreases the affinity of GluR1 for CNQX, which was explained by the partial agonistic effect of CNQX in the presence of stargazin. In contrast, stargazin increases the affinity for GYKI, and has only a small effect on CP. I also tested the effect of stargazin on recently described GYKI-insensitive receptors and found that inhibition of these receptors is restored by co-expression with stargazin. My data strongly suggest that the identified residues do not constitute the full GYKI-binding site. I could also show that the ectodomain of stargazin controls the changes in antagonist sensitivity of the receptors. In the second part of my thesis I used cultured hippocampal slices and Semliki Forest virus to overexpress PSD-95:GFP in CA1 region of hippocampus. I recorded simultaneously from a cell overexpressing PSD-95 and a neighboring control cell and compared their AMPA and NMDA currents. I confirmed the finding that overexpression of PSD-95 robustly increases currents mediated by AMPA receptors. In contrast to other studies, I observed that PSD-95 increases NMDA currents, although to smaller extent. I addressed the debated role of PSD-95 in regulating the presynatic release probability and found that overexpression of PSD-95 did not change glutamate release probability. Importantly, I observed that cells overexpressing PSD-95 have a lower rectification index of synaptic AMPA receptors, strongly suggesting that PSD-95 overexpression led to an increased fraction of AMPA receptors that lack GluR2 subunit. In conclusion, the work presented in this thesis gives further insights into AMPA receptor physiology, both from the aspect of pharmacology and synaptic trafficking. The results of co-expression of stargazin with the previously described GYKI-insensitive GluR1 mutants strongly indicate that TARP interacts with the linker domains of AMPA receptors. This finding is of great importance for understanding the molecular mechanism of AMPA-TARP interaction. Furthermore, this thesis shows that PSD-95 regulates both AMPA and NMDA synaptic currents by increasing the number of synaptic receptors. In addition, my data suggest that PSD-95 enriches the number of GluR2-lacking receptors in the synapse. Given the Ca2+permeability of GluR2-lacking receptors and their implication in plasticity and excitotoxicity, this finding is important for understanding how the synaptic localization of these receptors is regulated.

regulation rapid function cp localization psd receptor tarp synaptic nmda ampa tarps gfp ca2 xenopus ddc:500 ca1 ddc:570

Seb4 – an RNA-binding protein as a novel regulator of myogenesis during early development in Xenopus laevis

Fakultät für Biologie - Digitale Hochschulschriften der LMU - Teil 03/06

Play Episode Listen Later Dec 22, 2008

Mon, 22 Dec 2008 12:00:00 +0100 https://edoc.ub.uni-muenchen.de/9513/ https://edoc.ub.uni-muenchen.de/9513/1/Oberleitner_Sabine.pdf Oberleitner, Sabine ddc

protein binding regulators early development xenopus ddc:500 ddc:570

Connexin 40 promoter-based enrichment of embryonic stem cell-derived cardiovascular progenitor cells

Medizin - Open Access LMU - Teil 15/22

Play Episode Listen Later Jan 1, 2008

Background: Pluripotent embryonic stem (ES) cells that can differentiate into functional cardiomyocytes as well as vascular cells in cell culture may open the door to cardiovascular cell transplantation. However, the percentage of ES cells in embryoid bodies (EBs) which spontaneously undergo cardiovascular differentiation is low (< 10%), making strategies for their specific labeling and purification indispensable. Methods: The human connexin 40 (Cx40) promoter was isolated and cloned in the vector pEGFP. The specificity of the construct was initially assessed in Xenopus embryos injected with Cx40-EGFP plasmid DNA. Stable Cx40-EGFP ES cell clones were differentiated and fluorescent cells were enriched manually as well as via fluorescence-activated cell sorting. Characterization of these cells was performed with respect to spontaneous beating as well as via RT-PCRs and immunofluorescent stainings. Results: Cx40-EGFP reporter plasmid injection led to EGFP fluorescence specifically in the abdominal aorta of frog tadpoles. After crude manual enrichment of highly Cx40-EGFP- positive EBs, the appearance of cardiac and vascular structures was increased approximately 3-fold. Immuno fluorescent stainings showed EGFP expression exclusively in vascular-like structures simultaneously expressing von Willebrand factor and in formerly beating areas expressing alpha-actinin. Cx40-EGFP-expressing EBs revealed significantly higher numbers of beating cardiomyocytes and vascular-like structures. Semiquantitative RT-PCRs confirmed an enhanced cardiovascular differentiation as shown for the cardiac markers Nkx2.5 and MLC2v, as well as the endothelial marker vascular endothelial cadherin. Conclusions: Our work shows the feasibility of specific labeling and purification of cardiovascular progenitor cells from differentiating EBs based on the Cx40 promoter. We provide proof of principle that the deleted CD4 (Delta CD4) surface marker-based method for magnetic cell sorting developed by our group will be ideally suitable for transference to this promoter. Copyright (c) 2008 S. Karger AG, Basel.

dna copyright medizin promoters stem cells basel cardiovascular enrichment derived characterization ebs progenitor immuno embryonic stem cells willebrand xenopus egfp connexin nkx2 karger ag cx40

The AAA-ATPase p97 in mitosis and fertilization

Fakultät für Biologie - Digitale Hochschulschriften der LMU - Teil 02/06

Play Episode Listen Later Oct 29, 2007

Late mitotic events are chiefly controlled by proteolysis of key regulatory proteins via the ubiquitin-proteasome pathway. In this pathway ubiquitin ligases modify substrates by attachment of ubiquitin (“ubiquitylation”), which usually results in their subsequent degradation by the 26S proteasome. The crucial ubiquitin ligase involved in late mitosis is the anaphase-promoting complex or cyclosome (APC/C). Among the many substrates of the APC/C is the anaphase inhibitor securin, whose destruction leads to activation of separase, which in turn triggers sister chromatid separation by proteolytic cleavage of cohesin. The APC/C also targets cyclin B1, an activating subunit of Cdk1 kinase, whose inactivation is a prerequisite for mitotic exit. The unstable APC/C substrates are often found in association with stable partner proteins. How single subunits of multi-protein complexes are selectively extracted and eventually degraded is largely unknown, but there is increasing evidence that additional factors assist to extract ubiquitin-carrying subunits from stable binding partners. One such factor is vertebrate p97 (Cdc48 in yeast), an abundant and highly conserved member of the AAA-ATPase family. It is involved in such diverse processes as transcriptional regulation, membrane fusion, and ER-associated protein degradation (ERAD). The unifying scheme in these seemingly unrelated functions is that p97 is able to “extract” preferentially ubiquitylated proteins from their environment. Roles of p97 in mitosis have recently emerged: p97 was reported to be required for spindle disassembly and for nuclear envelope reformation during mitotic exit in Xenopus. Furthermore, a genetic interaction between p97, separase and securin, as well as a requirement of p97 for separase stability, were discovered in fission yeast. Given these hints and the importance of ubiquitylation in both mitosis and p97 pathways, this study intended to elucidate additional mitotic roles of p97 in vertebrates. Towards this end, tools to interfere with p97 function in Xenopus egg extracts were developed. These included immunodepletion of the p97 adaptors Npl4, Ufd1 and p47 and addition of recombinant dominant-negative p97-mutants. ERAD, which could be established here for the first time in Xenopus egg extracts, was greatly impaired in the absence of p97 function. However, many aspects of mitosis were found to be unaffected. Importantly, p97’s proposed role in spindle disassembly was clearly falsified within this thesis. Furthermore, p97 was shown to be dispensable for activity and stability of vertebrate separase. Disassembly of the mitotic checkpoint complex, which prevents premature APC/C activation by sequestering its activator Cdc20, did also not require functional p97 despite its dependence on ubiquitylation of Cdc20. However, a novel function of p97 at fertilization was discovered. p97 was found to interact with nucleoplasmin, a histone-binding chaperone that catalyzes the exchange of sperm-specific basic proteins (SBPs) to histones. Indeed, interference with p97 function delayed sperm decondensation in Xenopus egg extracts, thereby confirming a novel role of this AAA-ATPase in sperm chromatin remodelling. In another project the role of securin in human cells was investigated. Human cells lacking securin had been reported to suffer from massive chromosome missegregation, which was in sharp contrast to the mild phenotype of securin knockout mice. In collaboration with the group of M. Speicher it could be demonstrated that chromosome losses in securin-/- cells are transient and give way to a stable segregation pattern after just a few passages. This was despite persisting biochemical defects such as reduced level and activity of separase. These data demonstrate that securin is dispensable for chromosomal stability in human cells.

er human roles b1 speicher fertilization mitosis disassembly atpase xenopus ddc:500 ddc:570 26s erad cdk1

Analysis of Developmental Epistasis by Chromatin Immunoprecipitation in Xenopus laevis

Fakultät für Biologie - Digitale Hochschulschriften der LMU - Teil 02/06

Play Episode Listen Later Jul 25, 2007

The development of an organism from the fertilized zygote to a multicellular organism is a unidirectional process. It occurs in a spatially and temporally tightly controlled fashion. To understand how the genetic information is interpreted and how the cellular identity is inherited, are major challenges towards the understanding of developmental processes. Epigenetic marks like histone modifications, changes of the protein composition binding to DNA or the remodeling of nucleosomes have been shown to be important for the establishment of tissue-specific transcription profiles. Chromatin immunoprecipitation (ChIP) is a method to investigate the association of proteins to specific genomic loci. In this study, I have established two protocols for ChIP analyses of Xenopus laevis embryos: the In Situ ChIP and the Douncer ChIP. In addition, I have generated several antibodies in collaboration with Dr. Elisabeth Kremmer (GSF München) for ChIP analyses, which were directed against the muscle determination factor MyoD and the Wnt/β-catenin signaling components Lef/Tcf transcription factors Lef1 and Tcf1. While optimizing of the ChIP protocols, I have analyzed successfully the binding of various transcription factors, chromatin remodeling enzymes and histone modifications on genomic loci of key developmental regulators. With the In Situ ChIP, I have shown that the serum response factor SRF interacts predominantly with the actively transcribed myoD gene. Together with other data, this result helps to define a specific role of SRF protein in the stable maintenance of myoD transcription, which is essential for proper muscle differentiation. With the Douncer ChIP protocol, a time course study has been performed in order to understand, when and which histone modification marks appear during muscle cell determination and differentiation on the myoD locus. The temporal and spatial distribution of the analyzed histone modification marks was correlated for the most part with the expected patterns. Furthermore, I have demonstrated that direct binding of the chromatin remodeler CHD4/Mi2-β to the 5' part of the sip1 gene in gastrula stage embryos. This interaction represents a crucial regulatory module, which determines the position along the animal-vegetal axis of the embryo, where the border between the mesodermal and neuroectodermal germ layer will be formed. These examples represent on of the very few successful ChIP applications for the endogenous proteins in young Xenopus embryos, and I hope that my protocols will turn out useful for future investigations of regulatory interactions in this vertebrate model organism.

dna chip developmental epigenetic srf chromatin xenopus ddc:500 epistasis ddc:570

Functional characterization of a novel Xenopus polo-like kinase interacting protein

Fakultät für Biologie - Digitale Hochschulschriften der LMU - Teil 02/06

Play Episode Listen Later Oct 23, 2006

Summary Cell division is one of the most fundamental processes in biology. Meiosis is a specialized form of cell division resulting in cells capable of sexual reproduction. In higher animals male reproductive cells are called sperm cells, the female ones are called oocytes. The life cycle of a typical sexually reproducing organism includes a point where sperm and oocyte fuse to yield a diploid zygote, which develops into a new individual. This process is termed fertilization. The oocytes of most vertebrates are arrested at metaphase of meiosis II before fertilization. This is thought to prevent development in the absence of fertilization (parthenogenesis). In 1971 a biochemical activity was discovered that mediates this cell cycle arrest and was hence termed cytostatic factor (CSF). CSF inhibits a protein complex called the anaphase-promoting complex/cyclosome (APC/C). The APC/C is a ligase that covalently attaches the small protein ubiquitin to cell cycle regulatory proteins in order to target them for proteolytic degradation. This results in ordered cell cycle progression. After fertilization of CSF-arrested oocytes calcium triggers the APC/C-dependent destruction of anaphase inhibitors like cyclin B or securin. This allows for progression beyond metaphase of meiosis II, pronuclear fusion and the subsequent onset of embryonic development. Studies in Xenopus egg extract have shown that the protein kinase Plx1 of the polo-like kinase family is also required for this process. This work has begun to characterize the protein XErp1, which has been found as interacting partner of Plx1. Function and regulation of XErp1 have been investigated in Xenopus egg extracts and oocytes. Inhibition of XErp1 in CSF-arrested Xenopus egg extracts has shown that the protein is required to maintain CSF arrest. Consistently, overexpression of XErp1 leads to an inability of the extract to activate the APC/C after a calcium stimulus which prevents metaphase to anaphase transition. These results suggested that XErp1 might be a direct inhibitor of the APC/C. Indeed, a carboxy-terminal domain of XErp1 was found to be able to directly inhibit the ubiquitin ligase activity of immuno-purified APC/C. Experiments examining the regulation of XErp1 have shown that the protein is degraded rapidly after calcium stimulation. This degradation could be shown to be dependent on a phosphorylated degradation signal in the amino-terminus of XErp1. Furthermore, it was shown that Plx1 phosphorylates the two serine residues 33 and 38 within this motif in vitro. Together these results lead to a mechanistic model of APC/C activation associated with release from CSF arrest. According to this model, Plx1-dependend phosphorylation of XErp1 leads to its destruction and therefore derepression of the APC/C.

experiments studies protein function functional polo interacting characterization inhibition csf kinase meiosis xenopus ddc:500 ddc:570

The role of Xenopus BRG1, a conserved subunit of SWI/SNF class of remodeling complexes, during early frog development

Fakultät für Biologie - Digitale Hochschulschriften der LMU - Teil 02/06

Play Episode Listen Later Jun 7, 2005

BRG1 is a conserved subunit of the SWI/SNF family of ATP dependent chromatin remodeling complexes. These complexes play an important role in the transcription of various genes by making promoters accessible to the transcription machinery. Mutations in BRG1 have been connected to various cancers. In addition, a BRG1 knock-out in mice is lethal at the periimplantation stage, while BRG1 heterozygote mice are predisposed to exencephaly and tumors of epithelial origin, showing the importance of BRG1 in normal development and disease. In this study, I used Xenopus laevis to study the role of BRG1 because this system allows manipulation of endogenous protein levels by the use of antisense oligonucleotide mediated knock-down as well as interference analysis at early stages of development by overexpression of wild type and dominant negative protein variants. Since BRG1 is conserved among all vertebrates, I initially studied the role of BRG1 in Xenopus development by overexpression of wild type and dominant negative human BRG1. Overexpression of dominant negative human BRG1 gave a ventralized phenotype suggesting a role of BRG1 in dorsal-ventral patterning. The specificity of phenotypes was confirmed by using wild type human BRG1. On the other hand, overexpression of wild type and dominant negative variants of human BRM showed no developmental phenotypes. Prompted by these results, a frog brg1 cDNA was cloned by searching the Xenopus laevis EST database, using human BRG1 as a query. In addition, monoclonal antibodies specific to xBRG1 were raised and characterized. The expression pattern of Xbrg1 was found to be ubiquitous until gastrula stage and is tissue specific from neurula stage onwards. A Xenopus homologue of INI1, a subunit of SWI/SNF chromatin-remodeling complex, was cloned using database search. The expression pattern of Xini1 was found to be similar to Xbrg1. Using site directed mutagenesis, a dominant negative construct of xBRG1 was made by mutating the conserved lysine into arginine (K770R). Loss and gain of function studies showed that BRG1 is involved in AP axis formation during Xenopus development. The gain of function studies were done by overex-pressing wild type and dominant negative xBRG1, while loss of function studies were done using highly specific antisense morpholino oligos. Specificity of morpholino treatment was further proven by the rescue of ventralized phenotypes of morphant embryos by overexpression of human BRG1. It was found that BRG1 knock-down affects several tissues as assessed by in-situ hybridization using tissue specific markers. To determine the molecular explanation for these pleiotropic effects, several genes involved in early patterning of Xenopus embryo during organizer formation were analyzed. The analysis was done using whole mount in-situ hybridization, revealing the spatial gene expression pattern. This analysis revealed that BRG1 mostly affects WNT signaling dependent genes required for dorsal mesoderm formation while leaving pan-mesodermal genes unaffected. Furthermore the genetic interaction of BRG1 with the WNT pathway was confirmed by epistasis experiments showing that overexpression of β-CATENIN can rescue the xBrg1 antisense morpholino oligos dependent ventralized phenotypes as well as formation of secondary axis by overexpression of β-CATENIN could be prevented by BRG1 knock-down. Since the whole embryo represents a complex situation whereby many signaling pathways interact with each other and influence the outcome, the animal cap system was used to analyze the effect of BRG1 on various signaling pathways by analyzing corresponding direct target genes. Animal cap assays showed that the effect of BRG1 is signal specific. Moreover, among the affected signaling pathways, BRG1 knock-down affected only specific genes. These results showed that the BRG1 effect is gene and signal specific. The importance of WNT signaling has also been shown in cancer as well as in haematopoietic and embryonic stem cell self renewal. Given the importance of the WNT signaling, the role of BRG1 on the WNT signaling pathway was further investigated. Treatment of animal cap cells with various doses of Wnt8 mRNA showed the differential requirement of the WNT signal for maximal stimulation of direct target genes. The direct target genes of the WNT pathway showed various degrees of reduction in their maximal stimulation upon BRG1 protein knock-down. The requirement of BRG1 for proper stimulation of the WNT target genes was further confirmed by overexpression of xBRG1 under sub-optimal conditions of WNT stimulation. A major conclusion from these experiments is that BRG1 protein defines signaling thresholds for WNT-mediated activation of target genes. This implies that chromatin remodeling complexes are part of the machinery, which translates inductive signals into spatial gene expression domains.

loss development class treatments animal frogs atp mutation remodeling specificity complexes wnt brm cdna conserved xenopus subunit overexpression ddc:500 catenin ddc:570

The subcellular trafficking of the prion protein: Characterisation of the function of the PrPc N-terminus

Medizinische Fakultät - Digitale Hochschulschriften der LMU - Teil 02/19

Play Episode Listen Later Sep 26, 2003

Transmissible spongiform encephalopathies (TSEs) are degenerative diseases of the central nervous system in humans and animals, and include Creutzfeldt-Jakob disease (CJD) in humans, scrapie in sheep and bovine spongiform encephalopathy in cattle. These spongiform encephalopathies can manifest as sporadic, familial and acquired disorders and are caused by the conformational alteration of the non-pathogenic cellular prion protein (PrPc) into a infectious isoform denoted PrPSc. The latter therefore represents a pathogenic agent (prion) which does not contain nucleic acids. During biogenesis, PrPc undergoes posttranslational modifications with the addition of two N-linked carbohydrate chains and a glycosyl-phosphatidyl-inositol-(GPI)-anchor. Properly folded PrPc transits through the Golgi compartment and the secretory pathway and is attached to the outer leaflet of the plasma membrane by the GPI-anchor. The cellular function of the prion protein is still unknown, although binding of copper to the octapeptide repeat sequence located at its N-terminus suggests a role of PrPc related to this phenomenon. In the present work, the physiological function of the N-terminal part of PrPc in subcellular trafficking was analysed. Metabolic labelling and surface-biotinylation assays were performed in order to compare the intracellular trafficking and turnover of PrPc mutants showing specific deletions within their N-terminal sequence with those of wild type PrPc (wtPrPc). Upon transient expression of these constructs in murine neuroblastoma cells, these deletions, although not influencing the biochemical properties or the cell surface expression of these proteins, lead to a delay in their endocytosis. The prolongation of the internalisation kinetics was shown to be dependent on the length of the deletion: truncation of the complete N-terminus leads to the almost complete inhibition of internalisation. The analysis of the kinetics of degradation showed a similar correlation with the N-terminal part of PrPc, since the half-life of the PrP-mutants was significantly prolonged when compared to that of the wild type protein. Additionally performed detailed analysis of the secretory pathway with immunoprecipitation assays showed that N-terminally truncated PrP molecules reach the plasma membrane at a later time point, when compared with wtPrPc. A closer analysis of the processing of the sugar molecules linked to these proteins performing an Endo-H digestion revealed that this delay in the transport to the cell surface takes place in a cellular compartment following the mid-Golgi. The following studies were done with a chimeric protein consisting of the short N-terminal segment of Xenopus laevis, which does not contain the copper-binding octarepeat region, fused to the N-terminally truncated mouse PrPc. These studies showed that endocytosis of this protein and its transport through the secretory pathway were comparable to those of the mouse wtPrPc. It was therefore concluded that the N-terminus belonging to a phylogenetically remote species can rescue the wild type trafficking phenotype. These results indicate that the N-proximal domain of the prion protein functions as a targeting element and is essential for both transport to the plasma membrane and modulation of endocytosis. The data support a model in which the N-terminal part of PrPc represents an epitope for binding to a transmembrane receptor containing internalisation-promoting motifs or for inclusion of PrPc into the secretory raft-compartments. The present work also indicates for the first time that copper affinity of the octarepeats and subcellular trafficking represent separate aspects in the life-cycle of the prion protein.

protein function trafficking metabolic prp gpi prion creutzfeldt jakob transmissible golgi characterisation cjd prpc xenopus ddc:600 n terminus prpsc endoh tses

Transcriptional Regulation of the Xenopus MyoD Gene

Fakultät für Biologie - Digitale Hochschulschriften der LMU - Teil 01/06

Play Episode Listen Later Jul 25, 2003

MyoD is one of the MRFs (Muscle Regulatory Factors) and it functions to determine the muscle cell fate. The mechanism by which MyoD regulates the muscle development program is very well understood. However, the transcriptional regulation of the MyoD gene itself has not studied in Xenopus. In this thesis, I have analyzed the transcriptional regulatory mechanism of the MyoD gene in Xenopus by different approaches, which include transgenic reporter analysis of its cis-regulatory elements of MyoD transcription and gain-of-function and loss-of-function tests of several potential regulaters. Here I showed that the expression of the XmyoD gene is controlled by a combination of induction, repression and maintenance. One activating motif, one repressing motif and one maintenance motif were found by transgenic reporter analysis. XSRF (Xenopus serum response factor) binds with the maintenance enhancer to maintain the expression of XmyoD gene. A repetitive DNA sequence was discovered in the -2.8/-2.0kb region in the XmyoD genomic sequence. The repetitive DNA sequence in the XmyoD gene locus may produce sense and anti-sense transcripts. In addition, several potential regulators have been analyzed. It has been shown that XSEB-4, a direct target of XmyoD protein, is able to induce the expression of XmyoD gene. Xenopus Ying Yang 1 (XYY1) can repress the expression of the XmyoD gene. Lef-1 is necessary and sufficient for the expression of XmyoD gene. This provides strong evidence that Lef-1 is the transcription factor of the zygotic Wnt signaling pathway that activates the expression of the XmyoD gene.

dna regulation lef wnt transcriptional xenopus ddc:500 ddc:570

Etablierung eines Expressions- und Testsystems für Membranrezeptoren an Oozyten von Xenopus laevis

Medizinische Fakultät - Digitale Hochschulschriften der LMU - Teil 01/19

Play Episode Listen Later Jun 5, 2003

Entwicklungsbiologen haben vor über 25 Jahren festgestellt, daß Progesteron (PROG) die Fortsetzung der Reifeteilung an Xenopus Oozyten durch nicht-genomische Mechanismen an der Plasmamembran initiiert. Obwohl mehrere Publikationen dabei keine oder nur späte Veränderungen der intrazellulären Calciumkonzentration [Ca2+]i beschreiben, konnten Wasserman et al. an einigen Oozyten [Ca2+]i-Erhöhungen innerhalb der ersten Minute nach PROG-Zugabe beobachten. Diese Versuche sollten mit der Methode des Calcium Imaging reproduziert werden, wobei der Verlauf von [Ca2+]i durch Fluoreszenzmessung und dem Ca2+-Indikatorfarbstoff Fura-2 gemessen wurde. Dabei konnten innerhalb der ersten Minuten nach PROG-Zugabe keine Veränderungen von [Ca2+]i gefunden werden. Lysophosphatidylsäure (LPA) hingegen löste sehr zuverlässig Calcium-Signale aus. Durch Thrombin, Angiotensin II und Acetylcholin ausgelöste Effekte ließen sich, wenn auch seltener, ebenfalls zeigen. Xenopus Oozyten sind molekularbiologisch als eukaryontisches Expressionssystem nutzbar. Zur Etablierung des Expressions- und Testsystems wurde RNA in die Oozyten injiziert, die für den GnRH-Rezeptor kodiert. Nach erfolgreicher Expression steigt [Ca2+]i 1-3 Minuten nach der Rezeptorbindung über eine Aktivierung von Phospholipase Cb und das InsP3 System an. Auch bei Injektion von weniger als 0,5ng RNA pro Oozyte in das Zytosol konnte nach zwei Tagen, bei weniger als 0,15ng nach vier Tagen, ein schnelles Ca2+-Signal auf GnRH-Zugabe gesehen werden. Ebenso zeigten diese Effekte auch Oozyten, bei denen ein eukaryontischer GnRH-Rezeptor-Expressionsvektor in den Kern mikroinjiziert wurde, nicht aber unbehandelte Oozyten oder andere Negativkontrollen. An glatten Gefäßmuskelzellen (RSMC) kann in vitro eine schnelle Erhöhung von [Ca2+]i auf Aldosteron (ALDO) und an Spermatozoen auf PROG gezeigt werden. Zur Anwendung des Expressionssystems auf schnelle nicht-genomische Steroideffekte wurde einerseits aus diesen Zellen isolierte RNA in den Oozyten exprimiert, als auch RNA, welche für ein membranständiges Progesteron-bindendes Protein (mPR) kodiert. Durch Expression von RSMC-RNA konnte an Oozyten allerdings keine Calciumreaktion auf ALDO beobachtet werden; ebensowenig auf PROG durch Expression von RNA aus Mäusehoden oder mPR-RNA. Die hier vorgestellte Methode ist daher weniger geeignet zur Screening-Untersuchung bei der Expressionsklonierung zur Isolierung putativer Rezeptoren aus Genbanken oder Gesamt-RNA. Insgesamt handelt es sich jedoch um ein sehr gutes System, die Expression eines Rezeptors funktionell nachzuweisen; weitere Untersuchungen zur Rezeptoraktivierung, Signaltransduktion und topographischen Signalausbreitung lassen sich anschließen.

system dabei gef tagen expression kern methode obwohl expressions verlauf rna fortsetzung ebenso insgesamt effekte erh prog mechanismen untersuchungen zellen wasserman publikationen aktivierung etablierung lpa isolierung progesteron rezeptoren injektion ca2 xenopus angiotensin ii signaltransduktion rezeptors ddc:600 acetylcholin zur anwendung plasmamembran zytosol testsystems screening untersuchung genbanken expressionssystem durch expression negativkontrollen membranrezeptoren oozyten

Untersuchungen zur Wirkung von östrogenwirksamen Stoffen auf die Gonadenentwicklung bei Fröschen (Rana temporaria und Xenopus laevis) sowie ultrastrukturelle und immunhistochemische Untersuchungen an Froschgonaden (Rana temporaria)

Tierärztliche Fakultät - Digitale Hochschulschriften der LMU - Teil 01/07

Play Episode Listen Later Feb 7, 2003

The influence of estrogen-like substances on the gonadal development in frogs (Rana temporaria and Xenopus laevis). Ultrastructural and immunohistochemical investiga-tions on the gonads of frogs (Rana temporaria). The aim of the present thesis was the investigation and assessment of the estrogen pollu-tion of a river in South-Germany above and below a sewage plant outlet and its possible effects on the gonadal development in amphibians. In an exposure experiment with differ-ent sewage dilutions the effect on the indigenous gras frog (Rana temporaria) were com-pared with the effects on the African claw frog (Xenopus laevis). Because of the lack of relevant data in current literature it was necessary to first collect some basic data on light microscopy, ultrastructure and immunohistochemistry with reference to frogs. Furthermore the sexual differentiation of two populations of different origin were compared histologically. Characterisation of the gonads The ovaries of Xenopus laevis displayed a garland-like structure in contrast to the compact ovaries of Rana temporaria. The ovaries of both frog species were surrounded by an epi-thelium and filled with germ cells which enclosed an ovarian cavity. The oogonies were mainly found in the peripheral parts of the organ. The oocytes were characterised by a big and irregularly shaped cell nucleolus with peripherally located nucleoli. They were sur-rounded by a thin one-layered follicular epithelium. Electron microscopical examination of the ovaries of Rana temporaria showed elongated tubular mitochondria in the cytoplasm which were found exclusively in oocytes. Some of the mitochondria from subadult frogs contained yolk crystals. Additionally an accumulation of electron-tight Granule was found just below the plasma membrane, which could be a preliminary stage of the cortical granule. The testis of the frogs were enveloped by an epithelium and a tunica albuginea which al-ready showed a tubular structure. The testis from Rana temporaria and the Xenopus laevis differed in their developmental stages. The testis of juvenile Rana temporaria contained only germ cells whereas the testis of some Xenopus laevis already contained spermato-cytes and spermatozoa. The spermatocysts, characteristic of frog testis, could be seen in conjunction with the appearance of spermatocytes only. By using light microscopy two different types of germ cells in both frog species could be distinguished which probably were primary and secondary germ cells. By electron microscopical investigation of the testis of Rana temporaria the somatic cells could, on the basis of location and morphology, be differentiated in two types. The somatic cells of the first type were located inside the Tubuli seminiferi and have probably the same function as the Sertoli cells of mammals. The cells of the second type, the Leydig cells or interstitial cells, were located outside the Tubuli and were characterized by granular vesicle in the cytoplasm. With view to the sexual differentiation of Rana temporaria a comparative histological inves-tigation of the gonads of juvenile and subadult frogs of a native midland population and a high alpine population was performed. The midland population proved to be a sexually semi-differentiated species since apart from clearly male or female animals it also com-prises intersex individuals in different stages of the transformation process. The genotypi-cally male animals developed female gonads in the first place which secondly converted into testis during a hermaphrodite stage. The transformation process from female into male gonads was, on the basis of morphological criteria, classified into three stages. The highal-pin population on the other hand proved to be a sexually differentiated race. By using the Avidin-Biotin-Complex-Technique five different antibodies were tested on the gonadal tissue of juvenile and subadult Rana temporaria. The test for Laminin, a non-collagen glycoprotein, which is part of the basal membrane in mammals, resulted in a posi-tive reaction. It seems therefore that similar to Laminin in mammals a glycoprotein plays an important part in the basal membrane of frogs. α-Actin, a fibrous protein of the smooth muscles, which was detected in the Theca externa of the layer of follicle cells in different species, could be established in the blood vessel wall only and not in the layer of follicle cells. Furthermore the occurrence of a Zona pellucida by using antibodies against the por-cine glycoprotein ZP3 was investigated. The ovum including the surrounding layer of follicle cells showed a negative reaction which however did not implicitly exclude the occurrence of a glycoprotein layer with a different antigenicity. Until now the existence of a glycoprotein layer in anurans, in connection with microscopical anatomy of ovaries in Rana temporaria or other species of frogs has not been mentioned in references. The examination of the go-nadal tissue as to the occurrence of ACE (Angiotensin Converting Enzymes) turned out negative as well. Example of application With the exception of a temporarily higher concentration of alkylphenol in the beginning of the exposure, the chemical analyses revealed a relatively low degree of pollution with alcyl-phenols and steroids. The results were comparable to other results of German rivers and stayed well below other European comparative data. According to the results of this study the current level of pollution of the experimental water with estrogens does not endanger the amphibian population. The examination did not reveal any influence of the sewage on the embryonal and larval development. Furthermore, the histological investigation of the gonads in exposed and unexposed frogs with reference to the gonadal sexual differentia-tion as well as the sex ratios did not reveal significant changes. There was no correlation as to the frequency of the occurrence of intersex in the groups of exposed and unexposed frogs, neither of Xenopus laevis nor of Rana temporaria. Only the transformation process from ovaries to testis of the sexually semi-differentiated species of Rana temporaria was slowed down in the group of exposed animals in contrast to unexposed animals. The rea-son for this phenomenon could be the inhibitive influence of the low-level but more continu-ous estrogen pollution in sewage than in river water. Conversely, a link between the accel-eration of the transformation process within the group of unexposed animals and the tem-porarily higher alkylphenol level in the beginning of the exposure cannot completely be ruled out. According to references alkylphenol can cause an increase of testosterone. The semiquantitative RT-PCR detecting Vitellogenin-mRNA carried out by the Institute of Freshwater Ecology and Inland Fisheries in Berlin showed a minor increase in females of Xenopus laevis which were exposed to sewage in the ration of a 2:1 dilution in contrast to the unexposed animals. Taking into account the synergistic effects of estrogens, the in-crease could be attributed to the higher estrogen pollution of the sewage. The histopa-thological analysis for the detection of toxical effects of the sewage as well as other poten-tial influential factors provided no hints as to a possibly toxical influence of the sewage.

european german berlin institute african wirkung zona conversely untersuchungen electron sowie stoffen rt pcr actin characterisation xenopus laminin inland fisheries south germany leydig ddc:500 sertoli ddc:590 theca tubuli zp3

Das Dhh1 Protein aus Saccharomyces cerevisiae

Fakultät für Chemie und Pharmazie - Digitale Hochschulschriften der LMU - Teil 01/06

Play Episode Listen Later Dec 18, 2002

Das Dhh1 Protein aus Saccharomyces cerevisiae ist aufgrund von acht hoch konservierten Aminosäure-Motiven als putative RNA Helikase klassifiziert. In S. pombe (Ste13p), Drosophi-la melanogaster (ME31B), Xenopus laevis (Xp54), Mus musculus (mmRCK) und Homo sa-piens (hRCK/p54) findet man Proteine, die zu Dhh1p eine sehr hohe Konservierung von bis zu 83 % aufweisen. Lediglich der N- und C-Terminus dieser Proteingruppe ist nicht konserviert. In der vorliegenden Arbeit wurde die Auswirkung der Deletion von DHH1 in Saccharomyces cerevisiae auf verschiedene Aspekte der DNA Schädigung und Reparatur, sowie die Funktio-nalität verschiedener Domänen von Dhh1p durch Mutationsanalysen untersucht. Im ersten Teil der Arbeit wurde das DHH1 Gen in verschiedenen Hefestämmen deletiert und die Auswirkungen von DNA schädigenden Substanzen auf diese Mutanten untersucht. Die De-letion von DHH1 führte zu einer starken Erhöhung der Sensitivität von Hefezellen sowohl ge-genüber Bleomycin als auch gegenüber MMS. Allerdings zeigten dhh1D-Zellen nur eine schwache Sensitivität gegenüber UV-Strahlung und keine Sensitivität gegenüber g-Strahlung. Dies weist sehr stark darauf hin, dass die beobachteten Sensitivitäten auf einem eventuell durch Membrandefekte verursachten, sogenannten „uptake“-Phänotyp beruhen. In „uptake“ unabhängigen Experimenten wurde die Funktionalität des Non-homologous End-joining Repa-raturweges der Hefe untersucht. Dabei konnte gezeigt werden, dass dhh1D-Stämme eine um den Faktor fünf reduzierte Effizienz in der Rezirkularisierung linearisierter Plasmide zeigen. Allerdings ist nur die Effizienz, nicht die Genauigkeit des End-joining in dhh1D-Stämmen be-troffen – die rezirkularisierten Plasmide wurden zu 100 % genau repariert. Dies weist darauf hin, dass die Deletion sich auf mehr als nur einen einzelnen Aspekt zellulä-rer Vorgänge auswirkt. Im zweiten Teil der Arbeit wurde die extreme Sensitivität der dhh1D-Stämme gegenüber Ble-omycin und MMS als Testsystem für die funktionelle Charakterisierung verschiedener Dhh1p Domänen verwendet. Dabei zeigte sich, dass eine Deletion des N-Terminus von Dhh1p kaum Einfluss auf die Funktionalität des Proteins hat. Die Deletion des C-Terminus führt zu einer deutlichen Sensitivität der Zellen gegenüber Bleomycin. Bei Deletion beider Termini wachsen die Zellen auf Bleomycin nur noch geringfügig besser als der dhh1D-Stamm. Diese Effekte werden durch Überexpression der verkürzten Proteine aufgehoben. Keine der drei Verkürzun-gen hat Einfluss auf das Wachstum auf MMS-haltigen Platten. Die Mutation der ATPase Domäne (Walker A Motiv) hebt die Funktion des Proteins fast voll-ständig auf. Diese Mutanten sind nahezu so sensitiv gegenüber Bleomycin, wie dhh1D Zellen. Die Überexpression der ATPase Mutante führt im Gegensatz zu den Verkürzungen zu keiner Verringerung der Sensitivität gegenüber Bleomycin. Die zusätzliche Entfernung der Termini in der ATPase Mutante führt nicht zu einer Erhöhung der Bleomycin-Sensitivität. Allerdings zeigt die Dreifachmutante deutlich schlechteres Wachstum auf MMS-haltigen Platten. Die Mutation des SAT-Motives in AAA führt ebenfalls zu einer deutlichen Bleomycin-Sensitivität. Der Phänotyp ist vergleichbar mit den Auswirkungen der Deletion des C-Terminus. Das ur-sprünglich als RNA Entwindemotiv charakterisierte SAT-Motiv wind mittlerweile eher als eine Art „Scharnier“ angesehen, das eine Bewegung der Domänen 1 und 2 im Dhh1 Protein relativ zueinander ermöglicht. Die Auswirkung der Mutation des SAT-Motivs in AAA im Vergleich zu den Verkürzungen und den ATPase Mutanten weist auf eine eher strukturelle Rolle des SAT-Motives in Dhh1p hin. Aus diesen Daten ließ sich ein vorläufiges Modell über die Funktionsweise des Dhh1 Proteins ableiten. In in vitro Experimenten wurde mit dem IMPACT-System aufgereinigtes Dhh1 Protein auf seine Fähigkeit hin untersucht, DNA und RNA zu entwinden. Für die verwendeten Substrate konnte keine in vitro Helikase Aktivität festgestellt werden. Zur Analyse der ATPase Aktivität wurde IMPACT-gereinigtes Dhh1p und durch Immunopräzipitation aus Heferohextrakten ge-wonnenes Protein eingesetzt. In beiden Fällen konnte keine ATP Hydrolyse beobachtet wer-den, obwohl die Mutationsanalyse eindeutig darauf hinweist, dass die ATPase Aktivität essen-tiell für die Funktion des Dhh1 Proteins ist.

dna impact arbeit dabei rolle dom auswirkungen protein einfluss keine aaa bewegung daten vergleich aspekte wachstum allerdings verk funktion modell homo mus faktor mutation aspekt rna ins vorg gegensatz effizienz proteins auswirkung erh mms zellen substanzen entfernung funktionsweise platten proteine reparatur motiven experimenten funktionalit ble genauigkeit deletion strahlung aminos hefe lediglich substrate termini mutanten verringerung saccharomyces sensitivit uv strahlung charakterisierung repa konservierung die auswirkung der ph xenopus zur analyse ddc:500 saccharomyces cerevisiae dna sch testsystem c terminus n terminus ddc:540 diese effekte mutationsanalyse plasmide hefezellen immunopr atpase aktivit atp hydrolyse die deletion mutationsanalysen

Biogenese der spleißosomalen UsnRNPs

Fakultät für Biologie - Digitale Hochschulschriften der LMU - Teil 01/06

Play Episode Listen Later Dec 5, 2002

Ribonukleoproteinpartikel (RNPs) sind Komplexe aus RNA und Proteinen, die entscheidende Funktionen bei Prozessen wie Translation, Telomer-Synthese, Protein-Import in das endoplasmatische Retikulum oder RNA-Prozessierung übernehmen. Obwohl stets neue Beispiele die Bedeutung von RNPs untermauern, sind grundlegende Aspekte ihrer Funktion noch unklar. So stellte sich zu Beginn dieser Arbeit die Frage, wie sich die Komponenten von RNPs zu funktionellen Gebilden zusammenlagern. In frühen in-vitro-Studien war beobachtet worden, dass sich RNPs spontan ausbilden und dieser Vorgang keine weiteren Faktoren benötigt. Daraus war die Hypothese abgeleitet worden, dass dies möglicherweise auch der in vivo Situation entsprechen könnte. Unerwartete Einblicke in die Biogenese von RNPs lieferten schliesslich Studien zum "survival motor neurons"-Protein (SMN), dem Krankheitsgenprodukt der spinalen Muskelatrophie. Antikörper gegen SMN und seinem Bindungspartner Gemin2 inhibierten in Xenopus laevis Oocyten die Ausformung von RNP-Untereinheiten des Spleißosoms - den U snRNPs und nährten den Verdacht, dass diese Proteine Hilfsfaktoren der U snRNP-Biogenese sein könnten. Das Ziel der vorliegenden Arbeit war daher, mechanistische Details über die Zusammenlagerung von U snRNPs in vivo zu ermitteln und die Rolle von SMN und Gemin2 zu untersuchen. Die wesentlichen Schritte der Biogenese von U snRNPs können experimentell in X. laevis Oocyten verfolgt werden. Nach dem Export der U snRNAs U1, U2, U4 und U5 in das Cytosol lagern sich dort jeweils sieben sogenannte Sm-Protein an ein gemeinsames Motiv der U snRNAs an und formen so die Grundstruktur jedes U snRNPs, die Sm-Core-Domäne. Hierauf folgen die Hypermethylierung der U snRNA-Kappe und der Import der Sm-Core-Domäne in den Zellkern, wo sich U snRNP-spezifische Proteine anlagern, ehe die reifen snRNPs am Spleißprozess teilnehmen. In der vorliegenden Arbeit wurde zunächst ein zellfreies System entwickelt, durch das die Zusammenlagerung von U snRNPs in der Komplexität des Cytosols untersucht werden konnte. Unter Verwendung von Extrakten aus Xenopus laevis-Eiern oder HeLa-Zellen konnte gezeigt werden, dass die Ausbildung der Sm-Core-Domäne, entgegen bisheriger Vermutungen, nicht spontan erfolgt, sondern Energie in Form von ATP benötigt. Aus Depletionsversuchen wurde deutlich, dass SMN unter diesen zellähnlichen Bedingungen für die snRNP-Biogenese unbedingt erforderlich ist. SMN, dies zeigten immunbiochemische Reinigungen, ist in der Zelle mit 17 verschiedenen Proteinen assoziiert, die hier erstmals vollständig identifiziert wurden. Dieser SMN-Komplex enthält bereits alle Sm-Proteine, jedoch keine U snRNAs. Anhand direkten Sm-Protein-Transferstudien wurde klar, dass der SMN-Komplex allein nicht nur notwendig sondern auch hinreichend für die Ausbildung der Sm-Core-Domäne, ist. Dennoch konnte mit dem pICln-Komplex ein Proteinkomplex entdeckt werden, der mit dem SMN-Komplex interagiert und dessen Aktivität erheblich steigert. Der pICln-Komplex enthält eine neuartige Methyltransferase, die Arginylreste in den Sm-Proteinen B/B’, D1 und D3 zu symmetrischen Dimethylargininen modifiziert. Es ist bekannt, dass hierdurch die Bindung von Sm-Proteinen an SMN verstärkt wird. Die vorliegenden Daten weisen darauf hin, dass SMN- und pICln-Komplexe eine funktionelle Einheit bilden, in der Modifikation und Transfer der Sm-Proteine koordiniert ablaufen. Erste Erkenntnisse aus Versuchen mit HeLa-Zellen und Patientenzelllinien deuten an, dass reduzierte Menge des SMN-Komplexes mit einer reduzierten U snRNP-Zusammenlagerungsaktivität einhergehen, und dass dies einen biochemischen Defekt in Spinaler Muskelatrophie darstellen könnte. In einem weiteren Projekt wurde mit Hilfe von Datenbankanalysen und biochemischen Strategien das SMN-homologe Protein SMNrp identifiziert und charakterisiert. Biochemische Studien zeigten, dass SMNrp eine Komponente des U2 snRNPs ist und eine essentielle Rolle beim Spleißen ausführt. Kernextrakte die kein SMNrp enthalten wiesen einen Defekt der Spleißosomen-Zusammenlagerung auf der Stufe des „prä-Spleißosoms“ auf. SMNrp ist demnach ein Zusammenlagerungsfaktor des Spleißosoms und bezüglich dieser Funktion dem U snRNP-Zusammenlagerungsfaktor SMN ähnlich.

system situation arbeit rolle hilfe energie projekt bedeutung beginn schritte import u2 ausbildung menge translation daten aspekte strategien dennoch beispiele d1 obwohl faktoren aktivit bedingungen funktion studien export atp rna daraus einheit funktionen anhand das ziel d3 motiv bindung komplexit zelle stufe prozessen verdacht komponenten versuchen komponente proteine vorgang antik eiern vermutungen komplexe defekt hypothese proteinen smn u5 grundstruktur modifikation u4 xenopus zellkern unter verwendung hierauf ddc:500 ausformung muskelatrophie methyltransferase hela zellen splei ddc:570 gebilden extrakten biogenese retikulum cytosol proteinkomplex

Identification of a Candidate CD5 Homologue in the Amphibian Xenopus laevis

Tiermedizin - Open Access LMU

Play Episode Listen Later Jan 1, 1995

We identified a novel T cell Ag in the South African clawed toad (Xenopus laevis) by a mAb designated 2B1. This Ag is present in relatively high levels on most thymocytes, approximately 65% of splenocytes, 55% of PBL, and 65% of intestinal lymphocytes, but is rarely seen on IgM+ B cells in any of these tissues. Lymphocytes bearing the 2B1 Ag proliferate in response to stimulation with Con A or PHA, whereas the 2B1- lymphocytes are reactive to LPS. Biochemical analysis indicates that this Ag is a differentially phosphorylated glycoprotein of 71 to 82 kDa. The protein core of 64 kDa bears both N- and O-linked carbohydrate side chains. The amino-terminal protein sequence of the 2B1 Ag shares significant homology with both the macrophage scavenger receptor type 1 motif and the mammalian CD5/CD6 family. The biochemical characteristics and cellular distribution of the 2B1 Ag suggest that it represents the CD5 homologue in X. laevis. While T cells constitutively express this highly conserved molecule, Xenopus B cells acquire the CD5 homologue only when they are stimulated in the presence of T cells

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Cardiac calcium channels expressed in Xenopus oocytes are modulated by dephosphorylation but not by cAMP-dependent phosphorylation

Chemie und Pharmazie - Open Access LMU - Teil 02/02

Play Episode Listen Later Jan 1, 1994

Sat, 1 Jan 1994 12:00:00 +0100 http://epub.ub.uni-muenchen.de/3652/ http://epub.ub.uni-muenchen.de/3652/1/3652.pdf Singer-Lahat, Dafna; Lotan, Ilana; Biel, Martin; Flockerzi, Veit; Hofmann, Franz; Dascal, Nathan Singer-Lahat, Dafna; Lotan, Ilana; Biel, Martin; Flockerzi, Veit; Hofmann, Franz und Dascal, Nathan (1994): Cardiac calcium channels expressed in Xenopus oocytes are modulated by dephosphorylation but not by cAMP-dependent phosphorylation. In: Receptors and Channels, Vol. 2: pp. 215-226.

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Primary structure and functional expression of a cyclic nucleotidegated channel from rabbit aorta

Chemie und Pharmazie - Open Access LMU - Teil 02/02

Play Episode Listen Later Jan 1, 1993

Sequences specific for cyclic nucleotide-gated channels (CNG channels) have been amplified by PCR from cDNA of heart, aorta, sinoatrial node, cerebellum, C-cells and kidney. The complete amino acid sequence of a CNG channel from rabbit aorta has been deduced by cloning and sequence analysis of the cDNA. Synthetic RNA derived from this cDNA induces the formation of a functional CNG channel in Xenopus oocytes.

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Modulation of cardiac Ca2+ channels in Xenopus oocytes by protein kinase C

Chemie und Pharmazie - Open Access LMU - Teil 02/02

Play Episode Listen Later Jan 1, 1992

L-Type calcium channel was expressed in Xenopus laevis oocytes injected with RNAs coding for different cardiac Cu2+ channel subunits, or with total heart RNA. The effects of activation of protein kinase C (PKC) by the phorbol ester PMA (4β-phorbol 12-myristate 13-acetate) were studied. Currents through channels composed of the main (1) subunit alone were initially increased and then decreased by PMA. A similar biphasic modulation was observed when the 1 subunit was expressed in combination with 2/δ, β and/or γ subunits, and when the channels were expressed following injection of total rat heart RNA. No effects on the voltage dependence of activation were observed. The effects of PMA were blocked by staurosporine, a protein kinase inhibitor. β subunit moderated the enhancement caused by PMA. We conclude that both enhancement and inhibition of cardiac L-type Ca2+ currents by PKC are mediated via an effect on the 1 subunit, while the β subunit may play a mild modulatory role.

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The roles of the subunits in the function of the calcium channel

Chemie und Pharmazie - Open Access LMU - Teil 01/02

Play Episode Listen Later Jan 1, 1991

Dihydropyridine-sensitive voltage-dependent L-type calcium channels are critical to excitation-secretion and excitation-contraction coupling. The channel molecule is a complex of the main, pore-forming subunit alpha 1 and four additional subunits: alpha 2, delta, beta, and gamma (alpha 2 and delta are encoded by a single messenger RNA). The alpha 1 subunit messenger RNA alone directs expression of functional calcium channels in Xenopus oocytes, and coexpression of the alpha 2/delta and beta subunits enhances the amplitude of the current. The alpha 2, delta, and gamma subunits also have pronounced effects on its macroscopic characteristics, such as kinetics, voltage dependence of activation and inactivation, and enhancement by a dihydropyridine agonist. In some cases, specific modulatory functions can be assigned to individual subunits, whereas in other cases the different subunits appear to act in concert to modulate the properties of the channel.

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Primary structure and functional expression of a high voltage activated calcium channel from rabbit lung

Chemie und Pharmazie - Open Access LMU - Teil 01/02

Play Episode Listen Later Jan 1, 1990

The complete amino acid sequence of the receptor for organic calcium channel blockers (CaCB) from rabbit lung has been deduced by cloning and sequence analysis of the cDNA. Synthetic RNA derived from this cDNA induces the formation of a functional CaCB-sensitive high voltage activated calcium channel in Xenopus oocytes.

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Participation of Deoxyribonucleic Acid Polymerase a in Amplification of Ribosomal Deoxyribonucleic Acid in Xenopus laevis

Medizin - Open Access LMU - Teil 03/22

Play Episode Listen Later Jan 1, 1981

Thu, 1 Jan 1981 12:00:00 +0100 https://epub.ub.uni-muenchen.de/5374/1/Zimmermann_Wolfgang_5374.pdf Zimmermann, Wolfgang

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The early development and physiology of Xenopus laevis tadpole lateral line system