Podcasts about mitotic

BUFFALO, NY- February 12, 2024 – A new research paper was published in Oncotarget's Volume 15 on February 5, 2024, entitled, “Differential expression of Mad2 gene is consequential to the patterns of histone H3 post-translational modifications in its promoter region in human esophageal cancer samples.” Raw areca nut (AN) consumption increases esophageal squamous cell carcinoma (ESCC) due to overexpression of securin (pituitary tumor transforming gene1), causing chromosomal instability. Mitotic arrest deficient protein 2 (Mad2), a crucial spindle assembly checkpoint protein, is at risk of aneuploidy and tumor development when overexpressed or underexpressed. In this new study, researchers Chongtham Sovachandra Singh, Nabamita Boruah, Atanu Banerjee, Sillarine Kurkalang, Pooja Swargiary, Hughbert Dakhar, and Anupam Chatterjee from The Assam Royal Global University, University of Pennsylvania, LN Mithila University, University of Chicago Medicine, Nazareth Hospital, Laitumkhrah, and North-Eastern Hill University evaluated Mad2 status in human ESCC with AN consumption habits, revealing unclear molecular mechanisms. Human ESCC samples (n = 99) were used for loss of heterozygosity analysis at 4q25-28, while 32 samples were used for expression analysis of Mad2, E2F1 genes, and Rb-phosphorylation. Blood samples were used for metaphase preparation. The Mad2 deregulation was assessed using chromatin immunoprecipitation-qPCR assay in the core promoter region, establishing its association with the pRb-E2F1 circuit for the first time. “The study revealed overexpression and underexpression of Mad2, premature anaphase, and chromosome missegregation in all the samples.” LOH pattern identified a deletion in D4S2975 in 40% of ESCC samples. The study reveals the deregulation of pRb-E2F1 circuit in all samples. 4q27 disruption could be a factor for Mad2 underexpression in AN-induced esophageal carcinogenesis, while overexpression may be due to the deregulation of the Rb-E2F1 circuit and consequently elevation of H3K4me3 and H3K9ac. “Mad2 expression levels with chromosomal abnormalities can be a clinical biomarker, but further research is needed to understand pRb's role in Mad2 down-regulation.” DOI - https://doi.org/10.18632/oncotarget.28554 Correspondence to - Anupam Chatterjee - achatterjee@rgu.ac, chatterjeeanupam@hotmail.com Sign up for free Altmetric alerts about this article - https://oncotarget.altmetric.com/details/email_updates?id=10.18632%2Foncotarget.28554 Subscribe for free publication alerts from Oncotarget - https://www.oncotarget.com/subscribe/ Keywords - cancer, Mad2 gene, histone methylation, histone acetylation, Rb-phosphorylation; esophageal cancer About Oncotarget Oncotarget (a primarily oncology-focused, peer-reviewed, open access journal) aims to maximize research impact through insightful peer-review; eliminate borders between specialties by linking different fields of oncology, cancer research and biomedical sciences; and foster application of basic and clinical science. To learn more about Oncotarget, please visit https://www.oncotarget.com and connect with us: Facebook - https://www.facebook.com/Oncotarget/ X - https://twitter.com/oncotarget Instagram - https://www.instagram.com/oncotargetjrnl/ YouTube - https://www.youtube.com/@OncotargetJournal LinkedIn - https://www.linkedin.com/company/oncotarget Pinterest - https://www.pinterest.com/oncotarget/ Reddit - https://www.reddit.com/user/Oncotarget/ Spotify - https://open.spotify.com/show/0gRwT6BqYWJzxzmjPJwtVh Media Contact MEDIA@IMPACTJOURNALS.COM 18009220957

In this episode of the Epigenetics Podcast, we caught up with Sheila Teves from the University of British Columbia to talk about her work on the inheritance of transcriptional memory by mitotic bookmarking. Early in her research career, Sheila Teves focused on the impact of nucleosomes on torsional stress and gene regulation. She also highlights the development of a genome-wide approach to measure torsional stress and its relationship to nucleosome dynamics and RNA polymerase regulation. The conversation then shifts to her focus on transcriptional memory and mitotic bookmarking during her postdoc in the Tijan lab. She explores the concept of mitotic bookmarking, whereby certain transcription factors remain bound to their target sites during mitosis, facilitating efficient reactivation of transcription after cell division. She discusses her findings on the behavior of transcription factors on mitotic chromosomes, challenging the notion that they are excluded during mitosis. She also discusses the differences in binding behavior between the general transcription factor TBP and other transcription factors. Finally, the effect of formaldehyde fixation on the potential to find transcription factors bound to mitotic chromosomes is discussed.   References Teves, S., Henikoff, S. Transcription-generated torsional stress destabilizes nucleosomes. Nat Struct Mol Biol 21, 88–94 (2014). https://doi.org/10.1038/nsmb.2723 Sheila S Teves, Luye An, Anders S Hansen, Liangqi Xie, Xavier Darzacq, Robert Tjian (2016) A dynamic mode of mitotic bookmarking by transcription factors eLife 5:e22280. https://doi.org/10.7554/eLife.22280 Sheila S Teves, Luye An, Aarohi Bhargava-Shah, Liangqi Xie, Xavier Darzacq, Robert Tjian (2018) A stable mode of bookmarking by TBP recruits RNA polymerase II to mitotic chromosomes eLife 7:e35621. https://doi.org/10.7554/eLife.35621 Kwan, J. Z. J., Nguyen, T. F., Uzozie, A. C., Budzynski, M. A., Cui, J., Lee, J. M. C., Van Petegem, F., Lange, P. F., & Teves, S. S. (2023). RNA Polymerase II transcription independent of TBP in murine embryonic stem cells. eLife, 12, e83810. https://doi.org/10.7554/eLife.83810 Price, R. M., Budzyński, M. A., Shen, J., Mitchell, J. E., Kwan, J. Z. J., & Teves, S. S. (2023). Heat shock transcription factors demonstrate a distinct mode of interaction with mitotic chromosomes. Nucleic acids research, 51(10), 5040–5055. https://doi.org/10.1093/nar/gkad304   Related Episodes In Vivo Nucleosome Structure and Dynamics (Srinivas Ramachandran) From Nucleosome Structure to Function (Karolin Luger) Structural Analysis of Nucleosomes During Transcription (Lucas Farnung)   Contact Epigenetics Podcast on Twitter Epigenetics Podcast on Instagram Epigenetics Podcast on Mastodon Active Motif on Twitter Active Motif on LinkedIn Email: podcast@activemotif.com

Link to bioRxiv paper: http://biorxiv.org/cgi/content/short/2023.08.04.552008v1?rss=1 Authors: Talavera, R. A., Prichard, B. E., Sommer, R. A., Leitao, R. M., Sarabia, C. J., Hazir, S., Paulo, J. A., Gygi, S., Kellogg, D. Abstract: Cell growth is required for cell cycle progression. The amount of growth required for cell cycle progression is reduced in poor nutrients, which leads to a reduction in cell size. In budding yeast, nutrients influence cell size by modulating the duration and extent of bud growth, which occurs predominantly in mitosis. However, the mechanisms are unknown. Here, we used mass spectrometry to identify proteins that mediate the effects of nutrients on bud growth. This led to the discovery that nutrients regulate numerous components of the Mitotic Exit Network (MEN), which controls exit from mitosis. A key component of the MEN undergoes gradual multi-site phosphorylation during bud growth that is dependent upon growth and correlated with the extent of growth. Furthermore, activation of the MEN is sufficient to over-ride a growth requirement for mitotic exit. The data suggest a model in which the MEN integrates signals regarding cell growth and nutrient availability to ensure that mitotic exit occurs only when sufficient growth has occurred. Copy rights belong to original authors. Visit the link for more info Podcast created by Paper Player, LLC

Link to bioRxiv paper: http://biorxiv.org/cgi/content/short/2023.07.26.550666v1?rss=1 Authors: Zhang, G., Zhang, Y., Young, R., Garvanska, D., Song, C., Zhai, Y., Wang, Y., Jiang, H., Fang, J., Nilsson, J., Alfieri, C. Abstract: Accurate chromosome segregation is coordinated by the spindle assembly checkpoint (SAC) through its effector the mitotic checkpoint complex (MCC), to inhibit the anaphase-promoting complex or cyclosome (APC/C). Cdc20 is an essential mitotic regulator since it promotes mitotic exit through activating the APC/C and monitors kinetochore-microtubule attachment through activating the SAC. The proper functioning of Cdc20 requires multiple interactions with APC/C and MCC subunits. To functionally assess each of these interactions within cells requires efficient depletion of endogenous Cdc20, which is highly difficult to achieve by RNAi. Here we generated Cdc20 RNAi sensitive cell lines by CRISPR/Cas9 which display a penetrant metaphase arrest phenotype by a single RNAi treatment. In this null background, we accurately measured the contribution of each known motif of Cdc20 on APC/C and SAC activation. The CRY box, a previously identified degron was found to be critical for the SAC by promoting the MCC formation and stabilizing the interaction between the MCC and APC/C. These data reveal additional regulatory components within the SAC and establish a novel method to interrogate Cdc20 function. Copy rights belong to original authors. Visit the link for more info Podcast created by Paper Player, LLC

Link to bioRxiv paper: http://biorxiv.org/cgi/content/short/2023.07.02.547436v1?rss=1 Authors: Ozato, K., Wu, T., Hou, H., Dey, A., Bachu, M., Chen, X., Wisniewski, J., Kudoh, F., Chen, C., Chauhan, S., Xiao, H., Pan, R. Abstract: BRD4 binds to acetylated histones to regulate transcription and drive cancer cell proliferation. However, the role of BRD4 in normal cell growth remains to be elucidated. Here we investigated the question by using mouse embryonic fibroblasts with conditional Brd4 knockout (KO). We found that Brd4KO cells grow more slowly than wild type cells: they do not complete replication, fail to achieve mitosis, and exhibit extensive DNA damage throughout all cell cycle stages. BRD4 was required for expression of more than 450 cell cycle genes including genes encoding core histones and centromere/kinetochore proteins that are critical for genome replication and chromosomal segregation. Moreover, we show that many genes controlling R-loop formation and DNA damage response (DDR) require BRD4 for expression. Finally, BRD4 constitutively occupied genes controlling R-loop, DDR and cell cycle progression. We suggest that BRD4 epigenetically marks those genes and serves as a master regulator of normal cell growth. Copy rights belong to original authors. Visit the link for more info Podcast created by Paper Player, LLC

Link to bioRxiv paper: http://biorxiv.org/cgi/content/short/2023.05.05.539649v1?rss=1 Authors: Morales, E. A., Tyska, M. J. Abstract: Actin bundling proteins crosslink filaments into polarized structures that shape and support membrane protrusions including filopodia, microvilli, and stereocilia. In the case of epithelial microvilli, mitotic spindle positioning protein (MISP) is an actin bundler that localizes specifically to the basal rootlets, where the pointed ends of core bundle filaments converge. Previous studies established that MISP is prevented from binding more distal segments of the core bundle by competition with other actin binding proteins. Yet whether MISP holds a preference for binding directly to rootlet actin remains an open question. Using in vitro TIRF microscopy assays, we found that MISP exhibits a clear binding preference for filaments enriched in ADP-actin monomers. Consistent with this, assays with actively growing actin filaments revealed that MISP binds at or near their pointed ends. Moreover, although substrate attached MISP assembles filament bundles in parallel and antiparallel configurations, in solution MISP assembles parallel bundles consisting of multiple filaments exhibiting uniform polarity. These discoveries highlight nucleotide state sensing as a mechanism for sorting actin bundlers along filaments and driving their accumulation near filament ends. Such localized binding might drive parallel bundle formation and/or locally modulate bundle mechanical properties in microvilli and related protrusions. Copy rights belong to original authors. Visit the link for more info Podcast created by Paper Player, LLC

Link to bioRxiv paper: http://biorxiv.org/cgi/content/short/2023.05.01.538972v1?rss=1 Authors: Gergely, Z., Jones, M. H., Zhou, B., Cash, C., McIntosh, R., Betterton, M. Abstract: Copy rights belong to original authors. Visit the link for more info Podcast created by Paper Player, LLC

Link to bioRxiv paper: http://biorxiv.org/cgi/content/short/2023.04.25.538283v1?rss=1 Authors: Wong, S.-S., Wainman, A., Saurya, S., Raff, J. W. Abstract: Mitotic centrosomes assemble when centrioles recruit large amounts of pericentriolar material (PCM) around themselves in preparation for cell division. How the mitotic PCM grows to the correct size is unclear. In Drosophila syncytial embryos, thousands of mitotic centrosomes assemble in a common cytoplasm as the embryo proceeds through 13 rounds of near-synchronous nuclear division. During nuclear cycles (NCs) 11-13 these divisions gradually slow, and we find that mitotic centrosomes respond by reciprocally slowing their growth rate and increasing their growth period so that they grow to a consistent size at each cycle. This size homeostasis is enforced, at least in part, by the Cdk/Cyclin cell cycle oscillator (CCO). Moderate levels of CCO activity appear to initially promote centrosome growth by stimulating Polo/PLK1 recruitment to centrosomes, while higher levels of activity subsequently inhibit centrosome growth by phosphorylating centrosome proteins to decrease their centrosomal recruitment and/or maintenance as the embryos enter mitosis. Thus, the CCO initially promotes, and subsequently restricts, mitotic centrosome growth to help ensure that centrosomes grow to a consistent size. Copy rights belong to original authors. Visit the link for more info Podcast created by Paper Player, LLC

Link to bioRxiv paper: http://biorxiv.org/cgi/content/short/2023.03.27.534346v1?rss=1 Authors: Burigotto, M., Vigorito, V., Mattivi, A., Gliech, C., Ghetti, S., Bisio, A., Lolli, G., Holland, A. J., Fava, L. L. Abstract: 53BP1 acts at the crossroads between DNA repair and p53-mediated stress response. With its interactor USP28, it is part of the mitotic surveillance pathway (MSP), a sensor that monitors the duration of cell division, promoting p53-dependent cell cycle arrest when a critical time threshold is surpassed. 53BP1 dynamically associates with kinetochores, being recruited during prophase, and then undergoing a time-dependent loss of affinity. However, the relevance of this behaviour remains unclear. Here, we identify CENP-F as an interaction partner and kinetochore receptor for 53BP1. By engineering human cells with a CENP-F point mutation, we demonstrate that preventing 53BP1 kinetochore localization does not reduce MSP proficiency. Strikingly, however, preventing the loss of 53BP1 from the kinetochore by inhibiting Polo-like kinase 1 (PLK1) restrains MSP activity, a phenomenon that is abrogated in the CENP-F mutant condition. Taken together, we demonstrate that kinetochore-loaded 53BP1 represents an MSP functionally inhibited state and that PLK1-dependent re-localization of 53BP1 represents an important layer of MSP regulation. Copy rights belong to original authors. Visit the link for more info Podcast created by Paper Player, LLC

Link to bioRxiv paper: http://biorxiv.org/cgi/content/short/2023.03.21.533625v1?rss=1 Authors: Rosfelter, A., de Labbey, G., Chenevert, J., Dumollard, R., Schaub, S., Machaty, Z., Besnardeau, L., Hebras, C., Turlier, H., Burgess, D., mcdougall, a. Abstract: Although it has been studied for more than a century, the question of how one cell divides into two equal parts is still not fully resolved. Zygotes have provided much of the mechanistic insight into how the mitotic apparatus finds the center of the cell since the centrally-located mitotic apparatus is created from a large sperm aster that forms at the cortex and thus far from the zygote center. Here we show that in ascidians, the sperm aster extends throughout the cytoplasm during interphase yet remains located near the cortex and does not migrate towards the zygote center. It is only at mitotic entry, when the sperm aster has duplicated and the mitotic apparatus is being assembled, that most of the migration and centration occurs. This temporal pattern of centration behavior is mirrored by primate zygotes (including human). The current mechanisms of aster centration include cytoplasmic pulling that scale with microtubule (MT) length, MT pushing against the proximal cortex or MT-based cortical pulling. However, it is not yet known whether and how these 3 mechanisms are coordinated to prevent aster migration during interphase and trigger migration at mitotic entry. By monitoring quantitatively all three mechanisms (cytoplasmic pulling, pushing and cortical pulling) we have discovered that cortical pulling is switched off as the zygote enters mitosis while both cytoplasmic pulling and proximal cortical pushing remain active. Physical simulations could recapitulate both the static and migratory aspects of sperm aster and mitotic apparatus behavior. We therefore surmise that the reduction in cortical pulling at mitotic entry represents a switch that allows proximal cortical pushing forces and cytoplasmic pulling forces to center the nascent mitotic apparatus. Copy rights belong to original authors. Visit the link for more info Podcast created by Paper Player, LLC

Dr. Iyad Alnahhas interviews Dr. Max Kros about his and his team's recent manuscript entitled: "Mitotic count is prognostic in IDH-mutant astrocytoma without homozygous deletion of CDKN2A/B. Results of consensus panel review of EORTC trials 26053 and EORTC 22033-26033", published online in Neuro-Oncology in December 2022.   Read Paper

Link to bioRxiv paper: http://biorxiv.org/cgi/content/short/2023.02.21.528438v1?rss=1 Authors: Nkombo Nkoula, S., Velez-Aguilera, G., Ossareh-Nazari, B., Van Hove, L., Ayuso, C., Legros, V., Chevreux, G., Thomas, L., Seydoux, G., Askjaer, P., PINTARD, L. Abstract: The nuclear envelope, which protects and organizes the interphase genome, is dismantled during mitosis. In the C. elegans zygote, nuclear envelope breakdown (NEBD) of the parental pronuclei is spatially and temporally regulated during mitosis to promote the unification of the parental genomes. During NEBD, Nuclear Pore Complex (NPC) disassembly is critical for rupturing the nuclear permeability barrier and removing the NPCs from the membranes near the centrosomes and between the juxtaposed pronuclei. By combining live imaging, biochemistry, and phosphoproteomics, we characterized NPC disassembly and unveiled the exact role of the mitotic kinase PLK-1 in this process. We show that PLK-1 disassembles the NPC by targeting multiple NPC sub-complexes, including the cytoplasmic filaments, the central channel, and the inner ring. Notably, PLK-1 is recruited to and phosphorylates intrinsically disordered regions of several multivalent linker nucleoporins, a mechanism that appears to be an evolutionarily conserved driver of NPC disassembly during mitosis. Copy rights belong to original authors. Visit the link for more info Podcast created by Paper Player, LLC

Link to bioRxiv paper: http://biorxiv.org/cgi/content/short/2023.02.05.527197v1?rss=1 Authors: Cairo, G., Greiwe, C., Jung, G. I., Blengini, C., Schindler, K., Lacefield, S. Abstract: Proper chromosome segregation depends on establishment of bioriented kinetochore-microtubule attachments, which often requires multiple rounds of release and reattachment. Aurora B and C kinases phosphorylate kinetochore proteins to release tensionless attachments. Multiple pathways recruit Aurora B/C to the centromere and kinetochore. We studied how these pathways contribute to anaphase onset timing and correction of kinetochore-microtubule attachments in budding yeast meiosis and mitosis. We find that the pool localized by the Bub1/Bub3 pathway sets the normal duration of meiosis and mitosis, in differing ways. Our meiosis data suggests that disruption of this pathway leads to PP1 kinetochore localization, which dephosphorylates Cdc20 for premature anaphase onset. For error correction, the Bub1/Bub3 and COMA pathways are individually important in meiosis but compensatory in mitosis. Finally, we find that the haspin and Bub1/3 pathways function together to ensure error correction in mouse oogenesis. Our results suggest that each recruitment pathway localizes spatially distinct kinetochore-localized Aurora B/C pools that function differently between meiosis and mitosis. Copy rights belong to original authors. Visit the link for more info Podcast created by Paper Player, LLC

Link to bioRxiv paper: http://biorxiv.org/cgi/content/short/2023.01.12.523802v1?rss=1 Authors: Li, X.-J., Morgan, C., Nadar-Ponniah, P. T., Kolanus, W., Doetzlhofer, A. Abstract: Cochlear hair cell loss is a leading cause of deafness in humans. Neighboring supporting cells have some capacity to regenerate hair cells. However, their regenerative potential sharply declines as supporting cells undergo maturation (postnatal day 5 in mice). We recently reported that reactivation of the RNA-binding protein LIN28B restores the hair cell-regenerative potential of P5 cochlear supporting cells. Here, we identify the LIN28B target Trim71 as a novel and equally potent enhancer of supporting cell plasticity. TRIM71 is a critical regulator of stem cell behavior and cell reprogramming, however, its role in cell regeneration is poorly understood. Employing an organoid-based assay, we show that TRIM71 reactivation increases the mitotic and hair cell-forming potential of P5 cochlear supporting cells by facilitating their de-differentiation into progenitor-like cells. Our mechanistic work indicates that the RNA-binding activity of TRIM71 is essential for such ability, and our transcriptomic analysis identifies gene modules that are linked to TRIM71 and LIN28B-mediated supporting cell reprogramming. Furthermore, our study uncovers that the TRIM71-LIN28B target Hmga2 is essential for supporting cell self-renewal and hair cell formation. Copy rights belong to original authors. Visit the link for more info Podcast created by Paper Player, LLC

Link to bioRxiv paper: http://biorxiv.org/cgi/content/short/2023.01.11.523633v1?rss=1 Authors: Redemann, S., Chen, Y.-Z., Zimyanin, V. L. Abstract: In metazoans, Polo Kinase (Plk1) controls several mitotic events including nuclear envelope breakdown, centrosome maturation and kinetochore assembly. Here we show that mitotic events regulated by Polo Like Kinase (PLK-1) in early C. elegans embryos depend on the mitochondrial-localized protein SPD-3. spd-3 mutant one-cell embryos contain abnormally positioned mitotic chromosomes and prematurely and asymmetrically disassemble the nuclear lamina. Nuclear envelope breakdown (NEBD) in C. elegans requires direct dephosphorylation of lamin by PLK-1. In spd-3 mutants PLK-1 levels are ~6X higher in comparison to control embryos and PLK-1::GFP was highly accumulated at centrosomes, the nuclear envelope, nucleoplasm, and chromosomes prior to NEBD. Partial depletion of plk-1 in spd-3 mutant embryos rescued mitotic chromosome and spindle positioning defects indicating that these phenotypes result from higher PLK-1 levels and thus activity. Our data suggests that the mitochondrial SPD-3 protein controls NEBD and chromosome positioning by regulating the endogenous levels of PLK-1 during early embryogenesis in C. elegans. This finding suggests a novel link between mitochondria and mitotic events by controlling the amount of a key mitotic regulator, PLK-1 and thus may have further implications in the context of cancers or age-related diseases and infertility as it provides a novel link between mitochondria and mitosis. Copy rights belong to original authors. Visit the link for more info Podcast created by Paper Player, LLC

Link to bioRxiv paper: http://biorxiv.org/cgi/content/short/2023.01.12.523730v1?rss=1 Authors: Ganguli, S., Wyatt, T., Meyer, T., Baum, B., Matthews, H. Abstract: Oncogenic Ras has been shown to change the way cancer cells divide by increasing the forces generated during mitotic rounding. In this way, RasV12 enables cancer cells to divide across a wider range of mechanical environments than normal cells. Here, we identify a further role for oncogenic Ras-ERK signalling in division by showing that RasV12 expression alters the shape, division orientation and respreading dynamics of cells as they exit mitosis, in a manner that depends on MEK and ERK. Many of these effects appear to result from the impact of RasV12 signalling on actomyosin contractility, since RasV12 induces the severing of retraction fibres that normally guide spindle positioning and provide a memory of the interphase cell shape. In support of this idea, the RasV12 phenotype is reversed by inhibition of actomyosin contractility, and can be mimicked by the loss of cell-substrate adhesion during mitosis. Thus, the induction of oncogenic Ras-ERK signalling leads to rapid changes in division orientation that, along with the effects of RasV12 on cell growth and cell cycle progression, are likely to disrupt epithelial tissue organisation and contribute to cancer dissemination. Copy rights belong to original authors. Visit the link for more info Podcast created by Paper Player, LLC

Link to bioRxiv paper: http://biorxiv.org/cgi/content/short/2023.01.09.523293v1?rss=1 Authors: Chiu, K., Berrada, Y., Eskndir, N., Song, D., Fong, C., Naughton, S., Chen, T., Moy, S., Gyurmey, S., James, L., Ezeiruaku, C., Capistran, C., Lowey, D., Diwanji, V., Peterson, S., Parakh, H., Burgess, A., Probert, C., Zhu, A., Anderson, B., Levi, N., Gerlitz, G., Packard, M. C., Dorfman, K. A., Bahiru, M. S., Stephens, A. D. Abstract: Mitosis is an essential process in which the duplicate genome is segregated equally into two daughter cells. CTCF has been reported to be present in mitosis but its importance for mitotic fidelity remains to be determined. To evaluate the importance of CTCF in mitosis, we tracked mitotic behaviors in wild type and two different CTCF CRISPR-based genetic knockdowns. We find that knockdown of CTCF results in prolonged mitoses and failed anaphase segregation via time lapse imaging of SiR-DNA. CTCF knockdown did not alter cell cycling or the mitotic checkpoint, which was activated upon nocodazole treatment. Immunofluorescence imaging of the mitotic spindle in CTCF knockdowns revealed disorganization via tri/tetrapolar spindles and chromosomes behind the spindle pole. Imaging of interphase nuclei showed that nuclear size increased drastically, consistent with failure to divide the duplicated genome in anaphase. Population measurements of nuclear shape in CTCF knockdowns do not display decreased circularity or increased nuclear blebbing relative to wild type. However, failed mitoses do display abnormal nuclear morphologies relative to successful mitoses, suggesting population images do not capture individual behaviors. Thus, CTCF is important for both proper metaphase organization and anaphase segregation which impacts the size and shape of the interphase nucleus. Copy rights belong to original authors. Visit the link for more info Podcast created by Paper Player, LLC

Link to bioRxiv paper: http://biorxiv.org/cgi/content/short/2022.12.29.520610v1?rss=1 Authors: Singh, J., Daniels, N. J., Pirozzi, F., Wynshaw-Boris, A., Lopez-Gonzalez, R., Padgett, R. A. Abstract: Mutations in the single-copy RNU4ATAC gene, which encodes U4atac snRNA of the minor spliceosome are linked to the developmental disorder microcephalic osteodysplastic primordial dwarfism type I (MOPD I). Partial loss-of-function mutations of U4atac snRNA lead to a poor prognosis, with less than three year survival. The most prominent characteristic of MOPD I is disrupted central nervous system development resulting in severe microcephaly and lissencephaly. In this study, we used self-organizing 3D cerebral organoids from patient-derived induced pluripotent stem cells (iPSCs) to investigate defective cellular events that disturb the laminar organization of the cortex and influence brain topology. We analyzed organoids from iPSCs homozygous for the partial loss-of-function U4atac snRNA 51G greater than A mutation and compared them to isogenic organoids obtained from iPSCs expressing wild-type U4atac snRNA, using immunostaining and 10X Genomics single-cell RNA sequencing. In our MOPD I organoids, we observed: a) reduced proliferation accompanied by premature neurogenesis depleting the neuro-progenitor pool due to an increased frequency of horizontal cell divisions in the ventricular zone; b) reduced numbers of intermediate progenitor and outer radial glial cells in the outer sub-ventricular zone; and c) defective radial neuronal migration, which is critical for cortical expansion in humans. Our findings therefore provide insight into MOPD I cellular pathogenesis and underline the value of these cerebral organoids as model systems for human neurodevelopmental disorders. Copy rights belong to original authors. Visit the link for more info Podcast created by Paper Player, LLC

Link to bioRxiv paper: http://biorxiv.org/cgi/content/short/2022.12.07.519401v1?rss=1 Authors: Chalkley, M.-B. L., Mersfelder, R. B., Sundberg, M., Armstrong, L., Sahin, M., Ihrie, R. A., Ess, K. Abstract: Tuberous Sclerosis Complex (TSC) is a debilitating neurodevelopmental disorder characterized by a variety of clinical manifestations including epilepsy, autism, and intellectual disability. TSC is caused by mutations in the TSC1 or TSC2 genes, which encode the hamartin/tuberin proteins respectively. These proteins function as a heterodimer that negatively regulates mechanistic Target of Rapamycin Complex 1 (mTORC1). TSC research has focused on the effects of mTORC1, a critical signaling hub, on regulation of diverse cell processes including metabolism, cell growth, translation, and neurogenesis. However, non-canonical functions of TSC2 are not well studied, and the potential disease-relevant biological mechanisms are not well understood. We observed aberrant multipolar mitotic division, a novel phenotype, in TSC2 mutant iPSCs. The multipolar phenotype is not meaningfully affected by treatment with mTORC1 inhibition, suggesting that multipolar division is an mTORC1-independent phenotype. We further observed dominant negative activity of the mutant form of TSC2 in producing the multipolar division phenotype. These data expand the knowledge of TSC2 function and pathophysiology which will be highly relevant to future treatments for patients with TSC. Copy rights belong to original authors. Visit the link for more info Podcast created by Paper Player, LLC

Link to bioRxiv paper: http://biorxiv.org/cgi/content/short/2022.11.21.517340v1?rss=1 Authors: Carmo, C., Coelho, J., Silva, R., Tavares, A., Boavida, A., Gaetani, P., Martinho, R. G., Oliveira, R. A. Abstract: Mitotic chromatin is largely assumed incompatible with transcription due to changes in the transcription machinery and chromosome architecture. However, the mechanisms of mitotic transcriptional inactivation and their interplay with chromosome assembly remain largely unknown. By monitoring ongoing transcription in Drosophila early embryos, we reveal that eviction of nascent mRNAs from mitotic chromatin occurs after substantial chromosome compaction and is not promoted by condensin I. Instead, we show that the timely removal of transcripts from mitotic chromatin is driven by the SNF2 helicase-like protein Lodestar (Lds), identified here as a modulator of sister chromatid cohesion defects. In addition to transcriptional termination, we uncovered that Lds cooperates with Topoisomerase 2 to ensure efficient sister chromatid resolution and mitotic fidelity. We conclude that mitotic transcriptional termination is not a passive consequence of cell cycle progression and/or chromosome compaction but occurs via dedicated mechanisms with functional parallelisms to sister chromatid resolution. Copy rights belong to original authors. Visit the link for more info Podcast created by Paper Player, LLC

Link to bioRxiv paper: http://biorxiv.org/cgi/content/short/2022.11.08.515699v1?rss=1 Authors: Farrell, K., Wang, J. T., Stearns, T. Abstract: The spindle assembly checkpoint (SAC) temporally regulates mitosis by preventing progression from metaphase to anaphase until all chromosomes are correctly attached to the mitotic spindle. Centrosomes refine the spatial organization of the mitotic spindle at the spindle poles. However, centrosome loss leads to elongated mitosis, suggesting that centrosomes also inform the temporal organization of mitosis in mammalian cells. Here we find that the mitotic delay in acentrosomal cells is enforced by the SAC in a MPS1-dependent manner, and that a SAC-dependent mitotic delay is required for bipolar cell division to occur in acentrosomal cells. Although acentrosomal cells become polyploid, polyploidy is not sufficient to cause dependency on a SAC-mediated delay to complete cell division. Rather, the division failure in absence of MPS1 activity results from mitotic exit occurring before acentrosomal spindles can become bipolar. Furthermore, prevention of centrosome separation suffices to make cell division reliant on a SAC-dependent mitotic delay. Thus, centrosomes and their definition of two spindle poles early in mitosis provide a timely two-ness that allows cell division to occur in absence of a SAC-dependent mitotic delay. Copy rights belong to original authors. Visit the link for more info Podcast created by Paper Player, LLC

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

Link to bioRxiv paper: http://biorxiv.org/cgi/content/short/2022.10.17.512562v1?rss=1 Authors: Vishwanatha, A., Princova, J., Hohos, P., Zach, R., Prevorovsky, M. Abstract: Mitotic fidelity is crucial for the faithful distribution of genetic information into the daughter cells. Many fungal species, including the fission yeast Schizosaccharomyces pombe, undergo a closed form of mitosis, during which the nuclear envelope does not break down. In S. pombe numerous processes have been identified that contribute to successful completion of mitosis. Notably, perturbations of lipid metabolism can lead to catastrophic mitosis and the "cut" phenotype. It was suggested that these mitotic defects are caused by insufficient membrane phospholipid supply during the anaphase nuclear expansion. However, it is not clear whether additional factors are involved. In this study we characterized in detail the mitosis in an S. pombe mutant lacking the Cbf11 transcription factor, which regulates lipid metabolism genes. We show that in cbf11{Delta} cells mitotic defects appear already prior to anaphase, before the nuclear expansion begins. Moreover, we identify altered cohesin dynamics and centromeric chromatin structure as additional factors affecting mitotic fidelity in cells with disrupted lipid homeostasis, providing new insights into this fundamental biological process. Copy rights belong to original authors. Visit the link for more info Podcast created by Paper Player, LLC

Mitotic index is one of the many complicated-sounding medical terms that may be thrown at you after your dog is diagnosed with cancer. At its most basic, mitotic index is the count of how many cells in your dog's tumor are actively dividing, or reproducing. But what does this mean for you and your dog? Dr. Britton breaks down how mitotic index can help determine the prognosis for your dog, as well as which cancers it is most significant for. The aggressive potential of some cancers is closely linked to the mitotic index, while others can still be treated successfully even if the mitotic index is sky-high. Listen in to learn about the nuances of mitotic index, how to get it for your dog's tumor, and when it is most important to know this number before you make treatment decisions. Links Mentioned in Today's Show: National Human Genome Research Institute article on mitosis with images and video Related Links: Mast Cell Tumors – What You Need to Know About Your Dog's Cancer podcast episode Soft Tissue Sarcomas – What You Need to Know About Your Dog's Cancer podcast episode About Today's Guest, Dr. Brooke Britton: Brooke Britton completed her residency training in Medical Oncology at the University of Pennsylvania in 2012, and has been in clinical practice in the NYC and Jersey Shore area since that time. She helmed the Brooklyn and Downtown arms of the Oncology Department for BluePearl Veterinary Partners in New York for the past 9 years, and was an active participant in house officer training and clinical trials during her tenure there. She currently serves as a private consultant and maintains an independent clinical practice. Dr. Britton has lectured nationally and authored several peer-reviewed articles. She has particular interest in hematologic malignancies and the metastatic cascade. LinkedIn Other Links: To join the private Facebook group for readers of Dr. Dressler's book “The Dog Cancer Survival Guide,” go to https://www.facebook.com/groups/dogcancersupport/  Dog Cancer Answers is a Maui Media production in association with Dog Podcast Network This episode is sponsored by the best-selling animal health book The Dog Cancer Survival Guide: Full Spectrum Treatments to Optimize Your Dog's Life Quality and Longevity by Dr. Demian Dressler and Dr. Susan Ettinger. Available everywhere fine books are sold. Have a guest you think would be great for our show? Contact our producers at DogCancerAnswers.com Have an inspiring True Tail about your own dog's cancer journey you think would help other dog lovers? Share your true tail with our producers. If you would like to ask a dog cancer related question for one of our expert veterinarians to answer on a future Q&A episode, call our Listener Line at 808-868-3200 www.dogcanceransers.com. Dog Cancer News is a free weekly newsletter that contains useful information designed to help your dog with cancer. To sign up, please visit: www.dogcancernews.com Learn more about your ad choices. Visit megaphone.fm/adchoices

Link to bioRxiv paper: http://biorxiv.org/cgi/content/short/2020.11.17.386177v1?rss=1 Authors: Cuevas-Navarro, A., Van, R., Cheng, A., Urisman, A., Castel, P., McCormick, F. Abstract: The spindle assembly checkpoint (SAC) is an evolutionarily conserved safety mechanism that maintains genomic stability. However, despite the understanding of the fundamental mechanisms that control the SAC, it remains unknown how signaling pathways directly interact with and regulate the mitotic checkpoint activity. In response to extracellular stimuli, a diverse network of signaling pathways involved in cell growth, survival, and differentiation are activated and this process is prominently regulated by the Ras family of GTPases. Here we show that RIT1, a Ras-related GTPase, is essential for timely progression through mitosis and proper chromosome segregation. Furthermore, pathogenic levels of RIT1 silence the SAC, accelerate transit through mitosis, and promote chromosome segregation errors through direct association with SAC proteins MAD2 and p31comet. Our results highlight a unique function of RIT1 compared to other Ras GTPases and elucidate a direct link between a signaling pathway and the SAC through a novel regulatory mechanism. Copy rights belong to original authors. Visit the link for more info

The cell cycle is more than just memorizing the position of chromosomes on a slide, it can help us understand growth and development, lead us to treatments for cancer, or repair damaged organs and limbs. I go over the major steps of the cell cycle including interphase and the mitotic phase. Education level - high school to non-majors

Link to bioRxiv paper: http://biorxiv.org/cgi/content/short/2020.10.15.341305v1?rss=1 Authors: Gerguri, T., Fu, X., Kakui, Y., Khatri, B. S., Barrington, C., Bates, P. A., Uhlmann, F. Abstract: Underlying higher order chromatin organization are Structural Maintenance of Chromosomes (SMC) complexes, large protein rings that entrap DNA. The molecular mechanism by which SMC complexes organize chromatin is as yet incompletely understood. Two prominent models posit that SMC complexes actively extrude DNA loops (loop extrusion), or that they sequentially entrap two DNAs that come into proximity by Brownian motion (diffusion capture). To explore the implications of these two mechanisms, we perform biophysical simulations of a 3.76 Mb-long chromatin chain, the size of the long S. pombe chromosome I left arm. On it, the SMC complex condensin is modeled to perform loop extrusion or diffusion capture. We then compare computational to experimental observations of mitotic chromosome formation. Both loop extrusion and diffusion capture can result in native-like contact probability distributions. In addition, the diffusion capture model more readily recapitulates mitotic chromosome axis shortening and chromatin density enrichment. Diffusion capture can also explain why mitotic chromatin shows reduced, as well as more anisotropic, movements, features that lack support from loop extrusion. The condensin distribution within mitotic chromosomes, visualized by stochastic optical reconstruction microscopy (STORM), shows clustering predicted from diffusion capture. Our results inform the evaluation of current models of mitotic chromosome formation. Copy rights belong to original authors. Visit the link for more info

Link to bioRxiv paper: http://biorxiv.org/cgi/content/short/2020.10.09.331900v1?rss=1 Authors: Strom, A. R., Biggs, R. J., Banigan, E. J., Wang, X., Chiu, K., Herman, C., Collado, J., Yue, F., Ritland Politz, J. C., Tait, L. J., Scalzo, D., Telling, A., Groudine, M., Brangwynne, C. P., Marko, J., Stephens, A. D. Abstract: Chromatin, which consists of DNA and associated proteins, contains genetic information and is a mechanical component of the nucleus. Heterochromatic histone methylation contributes to nucleus and chromosome stiffness, but the contribution of heterochromatin protein HP1 (CBX5) is unknown. Here we used a novel HP1 auxin-inducible degron human cell line to rapidly degrade HP1. Degradation did not alter transcription, chromatin compaction, or histone methylation, but did decrease chromatin stiffness. Single-nucleus micromanipulation reveals that HP1 is essential to chromatin-based mechanics and maintains nuclear morphology, separate from histone methylation. Further experiments with dimerization-deficient HP1I165E indicate that chromatin crosslinking via HP1 dimerization is critical, while polymer simulations demonstrate the importance of chromatin-chromatin crosslinkers in mechanics. In mitotic chromosomes, HP1 similarly bolsters stiffness while aiding in mitotic alignment and faithful segregation. HP1 is therefore a critical chromatin-crosslinking protein that supports cellular functions by providing mechanical strength to chromosomes and the nucleus throughout the cell cycle. Copy rights belong to original authors. Visit the link for more info

Link to bioRxiv paper: http://biorxiv.org/cgi/content/short/2020.10.06.328880v1?rss=1 Authors: Sun, H., Hobert, O. Abstract: In most animals, the majority of the nervous system is generated and assembled into neuronal circuits during embryonic development. However, during juvenile stages, nervous systems still undergo extensive anatomical and functional changes to eventually form a fully mature nervous system by the adult stage. The molecular changes in post-mitotic neurons across post-embryonic development and the genetic programs that control these temporal transitions are not well understood. Using the model organism C. elegans, we comprehensively characterized the distinct functional states (locomotor behavior) and corresponding distinct molecular states (transcriptome) of the post-mitotic nervous system across temporal transitions from early post-embryonic periods to adulthood. We observed pervasive changes in gene expression, many of which are controlled by the developmental upregulation of the conserved heterochronic miRNA lin-4/mir-125 and the subsequent promotion of a mature neuronal transcriptional program through the repression of its target, the transcription factor lin-14. The functional relevance of these molecular transitions are exemplified by a temporally regulated target gene of the lin-14 transcription factor, nlp-45, a neuropeptide-encoding gene. We found that nlp-45 is required for temporal transitions in exploratory activity across larval stages, across sexual maturation, and into a diapause arrest stage. Our studies provide new insights into regulatory strategies that control neuron-type specific gene batteries to modulate distinct behaviors states across temporal, sex and environmental dimensions of post-embryonic development, and also provides a rich atlas of post-embryonic molecular changes to uncover additional regulatory mechanisms. Copy rights belong to original authors. Visit the link for more info

Link to bioRxiv paper: http://biorxiv.org/cgi/content/short/2020.09.29.318055v1?rss=1 Authors: Cantres-Velez, J., Blaize, J., Vierra, D., Boisvert, R., Garzon, J., Piraino, B., Tan, W., Deans, A., Howlett, N. G. Abstract: Fanconi anemia (FA) is a rare genetic disease characterized by increased risk for bone marrow failure and cancer. The FA proteins function together to repair damaged DNA. A central step in the activation of the FA pathway is the monoubiquitination of the FANCD2 and FANCI proteins under conditions of cellular stress and during S-phase of the cell cycle. The regulatory mechanisms governing S-phase monoubiquitination, in particular, are poorly understood. In this study, we have identified a CDK regulatory phospho-site (S592) proximal to the site of FANCD2 monoubiquitination. FANCD2 S592 phosphorylation was detected by LC-MS/MS and by immunoblotting with a S592 phospho-specific antibody. Mutation of S592 leads to abrogated monoubiquitination of FANCD2 during S-phase. Furthermore, FA-D2 ( FANCD2 -/- ) patient cells expressing S592 mutants display reduced proliferation under conditions of replication stress and increased mitotic aberrations, including micronuclei and multinucleated cells. Our findings describe a novel cell cycle-specific regulatory mechanism for the FANCD2 protein that promotes mitotic fidelity. Copy rights belong to original authors. Visit the link for more info

Link to bioRxiv paper: http://biorxiv.org/cgi/content/short/2020.09.23.309633v1?rss=1 Authors: Taguchi, Y.-h., Turki, T. Abstract: The histone group added to a gene sequence must be released during mitosis to halt transcription during the DNA replication stage of the cell cycle. However, the detailed mechanism of this transcription regulation remains unclear. In particular, it is not realistic to reconstruct all appropriate histone modifications throughout the genome from scratch after mitosis. Thus, it is reasonable to assume that there might be a type of ''bookmark'' that retains the positions of histone modifications, which can be readily restored after mitosis. We developed a novel computational approach comprising tensor decomposition (TD)-based unsupervised feature extraction (FE) to identify transcription factors (TFs) that bind to genes associated with reactivated histone modifications as candidate histone bookmarks. To the best of our knowledge, this is the first application of TD-based unsupervised FE to the cell division context and phases pertaining to the cell cycle in general. The candidate TFs identified with this approach were functionally related to cell division, suggesting the suitability of this method and the potential of the identified TFs as bookmarks for histone modification during mitosis. Copy rights belong to original authors. Visit the link for more info

Link to bioRxiv paper: http://biorxiv.org/cgi/content/short/2020.08.11.245829v1?rss=1 Authors: Lau, O. C. E., Damiani, D., Jossin, Y., Chehade, G., Schakman, O., Tajeddine, N., Gailly, P., Tissir, F. Abstract: Diaphanous (DIAPH) 3 is a member of the formin proteins that have the capacity to nucleate and elongate actin filaments and therefore, to remodel the cytoskeleton. DIAPH3 is essential for cytokinesis as its dysfunction impairs the contractile ring and produces multinucleated cells. Here, we report that DIAPH3 localizes at the centrosome during mitosis and regulates the assembly and polarity of the mitotic spindle. DIAPH3-deficient cells display disorganized cytoskeleton, multipolar spindles, and supernumerary centrosomes. DIAPH3-deficiency disrupts the expression and/or stability of microtubule-associated proteins SPAG5 and KNSTRN. SPAG5 and DIAPH3 have similar expression patterns in the developing brain and overlapping subcellular localization during mitosis. Knockdown of SPAG5 phenocopies the DIAPH3 deficiency, whereas its overexpression rescues the DIAH3 phenotype. Conditional inactivation of Diaph3 in the cerebral cortex profoundly disrupts neurogenesis depleting cortical progenitors and neurons; and leading to cortical malformation and autistic-like behavior. Our data uncover uncharacterized functions of DIAPH3 and provide evidence that this protein belongs to a molecular toolbox that links microtubule dynamics during mitosis to aneuploidy, cell death, fate determination defects, and cortical malformation. Copy rights belong to original authors. Visit the link for more info

Link to bioRxiv paper: http://biorxiv.org/cgi/content/short/2020.08.09.242602v1?rss=1 Authors: McHugh, T., Welburn, J. Abstract: The precise regulation of microtubule length during mitosis is essential to assemble and position the mitotic spindle and segregate chromosomes. Prior work has identified key molecular players in this process, including the kinesin-18 Kif18b and the kinesin-13 Kif2C/MCAK, which both promote microtubule depolymerization. MCAK acts as a potent microtubule depolymerase diffusing short distances on microtubules, while Kif18b is a mitotic processive motor with weak depolymerase activity. However, the individual activities of these factors cannot explain the dramatic increase in microtubule dynamics in mitosis. Using in vitro reconstitution and single molecule imaging, we demonstrate that Kif18b, MCAK and the plus-end tracking protein EB3 act in an integrated manner to potently promote microtubule depolymerization. We find Kif18b acts as a microtubule plus end delivery factor for its cargo MCAK, and that Kif18b also promotes EB accumulation to plus ends independently of lattice nucleotide state. Together, our work defines the mechanistic basis for a cooperative Kif18b-EB-MCAK network with emergent properties that act to efficiently shorten microtubules in mitosis. Copy rights belong to original authors. Visit the link for more info

Link to bioRxiv paper: http://biorxiv.org/cgi/content/short/2020.07.29.226639v1?rss=1 Authors: Jinks-Robertson, S., Gamble, D., Shaltz, S. Abstract: Mitotic recombination is the predominant mechanism for repairing double-strand breaks in Saccharomyces cerevisiae. Current recombination models are largely based on studies utilizing the enzyme I-SceI or HO to create a site-specific break, each of which generates broken ends with 3' overhangs. In this study sequence-diverged ectopic substrates were used to assess whether the frequent Pol {delta}-mediated removal of a mismatch 8 nucleotides from a 3' end affects recombination outcomes and whether the presence of a 3' versus 5' overhang at the break site alters outcomes. Recombination outcomes monitored were the distributions of recombination products into crossovers versus noncrossovers, and the position/length of transferred sequence (heteroduplex DNA) in noncrossover products. A terminal mismatch that was 22 nucleotides from the 3' end was rarely removed and the greater distance from the end did not affect recombination outcomes. To determine whether the recombinational repair of breaks with 3' versus 5' overhangs differs, we compared the well-studied 3' overhang created by I-SceI to a 5' overhang created by a ZFN (Zinc Finger Nuclease). Initiation with the ZFN yielded more recombinants, consistent with more efficient cleavage and potentially faster repair rate relative to I-SceI. While there were proportionally more COs among ZFN- than I-SceI-initiated events, NCOs in the two systems were indistinguishable in terms of the extent of strand transfer. These data demonstrate that the method of DSB induction and the resulting differences in end polarity have little effect on mitotic recombination outcomes despite potential differences in repair rate. Copy rights belong to original authors. Visit the link for more info

Link to bioRxiv paper: http://biorxiv.org/cgi/content/short/2020.07.22.216135v1?rss=1 Authors: Stachniak, T. J., Kastli, R., Hanley, O., Argunsah, A. O., Karayannis, T. Abstract: Neuronal identity is controlled in multiple developmental steps by key transcription factors that determine the unique properties of a cell. During embryogenesis, the transcription factor Prox1 has been shown to regulate VIP interneuron migration, survival, and as a result, circuit integration. Here, we explore the role of Prox1 as a regulator of genetic programs that guide the final specification of VIP interneuron subtypes in early post-natal life. Using in-vitro electrophysiology we find that post-natal removal of Prox1 differentially affects the synaptic integration of VIP bipolar and multipolar subtypes. RNA sequencing reveals that one of the downstream targets of Prox1 is the postsynaptic protein Elfn1, a constitutive regulator of presynaptic release probability. Genetic, pharmacological and electrophysiological experiments demonstrate that knocking out Prox1 reduces Elfn1 function in VIP multipolar but not in bipolar cells. Thus, in addition to the activity- dependent and contextual processes that finalize developmental trajectories, genetic programs engaged by Prox1 control the differentiation and connectivity of VIP interneuron subtypes. Copy rights belong to original authors. Visit the link for more info

Link to bioRxiv paper: http://biorxiv.org/cgi/content/short/2020.05.02.073924v1?rss=1 Authors: Huang, J.-Y., Krebs, B. B., Miskus, M. L., Russell, M. L., Duffy, E. P., Graf, J. M., Lu, H.-C. Abstract: Abnormal levels of fibroblast growth factors (FGFs) and FGF receptors (FGFRs) have been detected in various neurological disorders. The potent impact of FGF-FGFR in multiple embryonic developmental processes makes it challenging to elucidate their roles in post-mitotic neurons. Taking an alternative approach, we directly examined the impact of aberrant FGFR function after neurogenesis by generating a FGFR gain-of-function (GOF) transgenic mouse which expresses constitutively activated FGFR3 (FGFR3K650E) in post-mitotic glutamatergic neurons. We found that enhanced FGFR activity in glutamatergic neurons results in abnormal radial migration and axonal miswiring. Regarding the lamination phenotype in GOF brains, we found later-born Cux1-positive neurons are dispersed throughout the GOF cortex. Such a cortical migration deficit is likely caused, at least in part, by a significant reduction of the radial processes normally projecting from the radial glia cells (RGCs). In addition, FGFR3 GOF also results in the misrouting of several long-range axonal projections, including the corpus callosum, anterior commissure, and postcommissural fornix. RNA-sequencing analysis of the GOF embryonic cortex reveals significant alterations in several pathways involved in cell cycle regulation and axonal pathfinding. Collectively, our results suggest that FGFR hyperfunction in post-mitotic neurons at the late embryonic stage result in cortical dysplasia and circuit miswiring. Copy rights belong to original authors. Visit the link for more info

This podcast is part of the 2017 NSH Symposium/Convention Poster Podcast Series.  The lead author of this poster is Sarah Schollmeier. For more information on the author and to view the abstract, visit The Block.

Vladimir Joukov, M.D., Ph.D. Department of Biological Chemistry and Molecular Pharmacology Harvard Medical School, Boston - USA speaks on "Elucidating the mechanisms of mitotic centrosome and spindle assembly and their deregulation in disease"

Mauro Giacca, ICGEB, Molecular Medicine, Group Leader, Trieste - ITALY speaks on "Adeno-associated virus (AAV)-based vectors as powerful tools for gene transfer into post-mitotic cells in vivo". This seminar has been recorded at ICTP Trieste by ICGEB Trieste

Interview with Sarah Shen, MBBS, BMedSci, author of Characteristics and Associations of High-Mitotic-Rate Melanoma

Edith Heard Collège de France Epigenetics and cellular memory Lectures 2012-2013 Epigenetics, development and heredity Mammalian X–Chromosome Inactivation – an example of mitotic cellular memory Lecture 3

Edith Heard Collège de France Epigenetics and cellular memory Lectures 2012-2013 Epigenetics, development and heredity Mammalian X–Chromosome Inactivation – an example of mitotic cellular memory Lecture 3

Edith Heard Collège de France Epigenetics and cellular memory Lectures 2012-2013 Epigenetics, development and heredity Mammalian X–Chromosome Inactivation – an example of mitotic cellular memory Lecture 3

Edith Heard Collège de France Epigenetics and cellular memory Lectures 2012-2013 Epigenetics, development and heredity Mammalian X–Chromosome Inactivation – an example of mitotic cellular memory Lecture 3

Edith Heard Collège de France Epigenetics and cellular memory Lectures 2012-2013 Epigenetics, development and heredity Mammalian X–Chromosome Inactivation – an example of mitotic cellular memory Lecture 3

Edith Heard Collège de France Epigenetics and cellular memory Lectures 2012-2013 Epigenetics, development and heredity Mammalian X–Chromosome Inactivation – an example of mitotic cellular memory Lecture 3

Edith Heard Collège de France Epigenetics and cellular memory Lectures 2012-2013 Epigenetics, development and heredity Mammalian X–Chromosome Inactivation – an example of mitotic cellular memory Lecture 3

Edith Heard Collège de France Epigenetics and cellular memory Lectures 2012-2013 Epigenetics, development and heredity Mammalian X–Chromosome Inactivation – an example of mitotic cellular memory Lecture 3

Mauro Giacca, ICGEB, Molecular Medicine, Group Leader, Trieste - ITALY speaks on "Adeno-associated virus (AAV)-based vectors as powerful tools for gene transfer into post-mitotic cells in vivo". This seminar has been recorded at ICTP Trieste by ICGEB Trieste

Edith Heard Collège de France Epigenetics and cellular memory Lectures 2012-2013 Epigenetics, development and heredity Mammalian X–Chromosome Inactivation – an example of mitotic cellular memory Lecture 3

Edith Heard Collège de France Epigenetics and cellular memory Lectures 2012-2013 Epigenetics, development and heredity Mammalian X–Chromosome Inactivation – an example of mitotic cellular memory Lecture 3

Edith Heard Collège de France Epigenetics and cellular memory Lectures 2012-2013 Epigenetics, development and heredity Mammalian X–Chromosome Inactivation – an example of mitotic cellular memory Lecture 3

Edith Heard Collège de France Epigenetics and cellular memory Lectures 2012-2013 Epigenetics, development and heredity Mammalian X–Chromosome Inactivation – an example of mitotic cellular memory Lecture 3

Mon, 6 Feb 2012 12:00:00 +0100 https://edoc.ub.uni-muenchen.de/14152/ https://edoc.ub.uni-muenchen.de/14152/1/Huels_Daniela.pdf Hüls, Daniela ddc:540, ddc:500, Fakultät für

Mon, 25 Oct 2010 12:00:00 +0100 https://edoc.ub.uni-muenchen.de/15536/ https://edoc.ub.uni-muenchen.de/15536/1/Dulla_Kalyana_Chakravarthi.pdf Dulla, Kalyana Chakravarthi ddc:570, ddc:500, Fakultät für Biologi

Tue, 4 May 2010 12:00:00 +0100 https://edoc.ub.uni-muenchen.de/12319/ https://edoc.ub.uni-muenchen.de/12319/1/Wang_Bin.pdf Wang, Bin ddc:570, ddc:500, Fakultät für Biologie

Mitotic spindle microtubules have long been thought to deliver a signal to the cell cortex that positions the cytokinetic cleavage furrow. A new study reveals that accurate cytokinesis still occurs in the absence of contact between microtubules and the plasma membrane, and suggests that multiple spatial cues combine to define the furrow's location. This biosights episode presents the paper by von Dassow et al. from the December 14th, 2009 issue of the Journal of Cell Biology, and includes interviews with authors George von Dassow and Bill Bement. Produced by Eun Choi and Ben Short.   Subscribe to biosights via iTunes or RSS View biosights archive The Rockefeller University Press biosights@rockefeller.edu

Mon, 14 Dec 2009 12:00:00 +0100 https://edoc.ub.uni-muenchen.de/13811/ https://edoc.ub.uni-muenchen.de/13811/1/Huemmer_Stefan.pdf Hümmer, Stefan ddc:570, ddc:500, Fakultät für Biologie

This presentation discusses the kinesins involved in microtubule depolymerization and the factors that determine the depolymerization rate.

Fri, 16 Jan 2009 12:00:00 +0100 https://edoc.ub.uni-muenchen.de/12589/ https://edoc.ub.uni-muenchen.de/12589/1/Klein_Ulf.pdf Klein, Ulf ddc:570, ddc:500, Fakultät für Biologie

Wed, 23 Jan 2008 12:00:00 +0100 https://edoc.ub.uni-muenchen.de/7958/ https://edoc.ub.uni-muenchen.de/7958/1/Thein_Kerstin.pdf Thein, Kerstin ddc:500, ddc:570, Fa

Mitosis is the process by which sister chromatids are equally segregated into two daughter cells. Tight control in various events during mitotic progression is essential for maintaining chromosome stability. Mitotic kinases including Cyclin dependent kinase 1 (Cdk1) and Aurora family are required for regulating proper mitotic progression by phosphorylating mitotic substrates thereby, controlling their activities, localization or abundance. On the other hand, these mitotic kinases are modulated by de-novo synthesis, activators, phosphorylation and ubiquitin-dependent proteolysis. A thorough understanding of the function and regulation of mitotic kinases could further our knowledge on mitotic progression. In the first part of the thesis, we investigated the expression, localization and regulation of human Lats1 kinase, which is a close homologue of the yeast Dbf2 kinase family involved in the mitotic exit network (MEN). Despite the fact that Lats1 has been suggested to be a spindle protein that binds and inactivates Cdk1, we found that Lats1 is mainly cytoplasmic throughout the cell cycle by immunofluorescence microscopy. Both yeast two-hybrid and coimmunoprecipitation showed no significant interaction between Lats1 and Cdk1. Although Lats1 was highly phosphorylated during mitosis, no detectable kinase activity was observed. However, we identified Ste20 like kinase MST2 as the upstream regulator of human Lats1. Phosphorylation of Lats1 by Mst2 resulted in the activation of Lats1 kinase activity both in vivo and in vitro. This kinase-substrate relation was proven to be specific, as another distant Mst2 homolog, Mst4, did not possess this ability. Subsequent mass-spectrometry-based phosphosites analysis revealed that Mst2 phosphorylates Lats1 on more than five residues. Alanine mutations on Lats1T1079 and S909 impaired Lats1 kinase activity. Thus, we could not confirm the suggested role of Lat1 in mitosis. Instead, we show that similar to its Drosophila ortholog, Lats1 is involved in the Mst2 signaling pathway and might control developmentally regulated cell proliferation and apoptosis in mammals. In the second part of this thesis, we characterized hBora, a novel Aurora A interactor originally found in Drosophila. We show that hBora is upregulated and phosphorylated during mitosis. siRNA-mediated knockdown of hBora led to spindle formation defects and aneuploidy. hBora overexpression caused monoastral spindle formation and mislocalization not only of Aurora A but also Plk1. Further investigations showed that Cdk1 phosphorylation on hBoraSer252 leads to Plk1 binding and this may promote the SCF-mediated proteolysis of hBora. Indeed, Plk1 depletion led to an increase in hBora levels. Interestingly, the co-depletion of both hBora and Plk1 (to lower hBora levels in Plk1 depleted cells) rescued the localization of Aurora A to the centrosomes and bipolar spindle formation. Thus, we propose that hBora is a functional link between Plk1 and Aurora A and that by modulating the proteolysis of hBora, Plk1 could regulate Aurora A localization and activity. At the end, we also investigated the function of Aurora A and could show that Aurora A is required for centriole cohesion and centrosome separation.

The objective of this work was to examine follicular and oocyte growth in canine ovaries with light and electron microscopic techniques and to characterize canine oocytes during in vitro maturation. Ovaries of healthy bitches of different ages (4 months to 12.5 years)and breeds were used, which had undergone elective ovariohysterectomy at local veterinary clinics. The ovaries of 15 bitches were fixed in Bouin`s solution or paraformaldehyde (4%) for immunohistochemical studies and of three bitches in Karnovsky`s solution for electron microscopic evaluation. COCs and oocytes were recovered from 61 other bitches by slicing the ovaries. They were then examined before and after in vitro maturation (24 to 72 hours) in modified TCM-199 either by native evaluation or after fixation in paraformaldehyde (4%) and nuclear staining (propidium iodide/Hoechst 33342), immunofluorescence or glycohistochemistry. The evaluation of the fluorescence microscopic staining was performed by confocal laser scanning microscopy. Oocytes and COCs after 0, 24, 72 and 90 hours of in vitro maturation were also subjected to electron microscopic examination. The morphology of the canine ovary in light and electron microscopic aspects is comparable to that of other domestic animals. Primordial, primary, secondary and tertiary follicles were regularly seen. The diameter of the oocytes and of the germinal vesicle, as well as the thickness of the zona pellucida, clearly increases during oocyte development. Growing canine oocytes are characterized ultrastructurally by rapid growth in the number of cellular organelles, particularly mitochondria, smooth endoplasmatic reticulum and lipid droplets. Mitotic division starting at the primary follicle stage can be regularly observed by immunostaining with the proliferation marker Ki-67. Further immunohistochemical studies on ovaries indicate that estrogen receptors alpha and beta, as well as MMP-1, -2, -14 and TIMP-2 show a specific distribution in bitches. Canine oocytes could easily be isolated by slicing the ovaries. The number of recovered oocytes was clearly influenced by the age of the donor bitch but not by the breed, the reproductive status or the transportation time between time of surgery in the veterinary clinic and the recovery of the oocytes in the laboratory. 48% of all isolated oocytes had a dark homogenous ooplasm and multiple dense layers of cumulus cells. After in vitro maturation, morphological changes like the formation of vesicles and the loss of cumulus cells could be observed in most of the COCs. Immediately after recovery, the nuclei of all oocytes were at the germinal vesicle stage, although the chromatin showed different degrees of condensation. While first signs of the resumption of meiosis were seen after 24 hours of culture, only one oocyte in metaphase II could be seen after 72 hours. Nuclear and cytoplasmatic maturation could be detected by electron microscopy for up to 24 hours of in vitro culture, as well as signs of degeneration, which were even more prominent after longer culture periods. The immunoreaction of ZP3beta, alpha-Tubulin and Connexin 43 and the binding sites of the lectins WGA and SBA showed characteristic changes in canine oocytes and COCs before and after in vitro maturation.

Fri, 22 Oct 2004 12:00:00 +0100 https://edoc.ub.uni-muenchen.de/2794/ https://edoc.ub.uni-muenchen.de/2794/1/Schroeder_Reiter_Elizabeth.pdf Schroeder-Reiter, Elizabeth ddc:570, ddc:500, Fak

Structural investigation and morphometry of meiotic chromosomes by scanning electron microscopy (in comparison to light microscopy) of all stages of condensation of meiosis I + II show remarkable differences during chromosome condensation in mitosis and meiosis I of rye (Secale cereale) with respect to initiation, mode and degree of condensation. Mitotic chromosomes condense in a linear fashion, shorten in length and increase moderately in diameter. In contrast, in meiosis I, condensation of chromosomes in length and diameter is a sigmoidal process with a retardation in zygotene and pachytene and an acceleration from diplotene to diakinesis. The basic structural components of mitotic chromosomes of rye are ``parallel fibers{''} and ``chromomeres{''} which become highly compacted in metaphase. Although chromosome architecture in early prophase of meiosis seems similar to mitosis in principle, there is no equivalent stage during transition to metaphase I when chromosomes condense to a much higher degree and show a characteristic ``smooth{''} surface. No indication was found for helical winding of chromosomes either in mitosis or in meiosis. Based on measurements, we propose a mechanism for chromosome dynamics in mitosis and meiosis, which involves three individual processes: (i) aggregation of chromatin subdomains into a chromosome filament, (ii) condensation in length, which involves a progressive increase in diameter and (iii) separation of chromatids. Copyright (C) 2003 S. Karger AG, Basel.

Chromosomal in situ suppression (CISS) hybridization was performed with library DNA from sorted human chromosomes 8, 9, 15, 17, 21, and 22 on immunologically stained bone marrow cells of four patients with a hematologic neoplasm, including two patients with myelodysplastic syndrome and trisomy 8, one patient with promyelocytic leukemia bearing the translocation t(15;17)(q22;q11-12), and one patient with chronic myeloid leukemia and the translocation t(9;22)(q34;q11). In all patients, the results of conventional karyotype analysis could be confirmed by one- or two-color CISS hybridization using the appropriate chromosome-specific libraries. Our results show that CISS hybridization can detect both numerical and structural chromosome changes in immunologically classified cells with high specificity and reliability. The fact that chromosome spreads of very poor quality can now be included in such analyses is a decisive advantage of this approach. In addition, the suitability of this approach for interphase cytogenetics is discussed.

Tue, 1 Jan 1991 12:00:00 +0100 https://epub.ub.uni-muenchen.de/9352/1/9352.pdf Cremer, Christoph; Stelzer, Ernst; Wienberg, Johannes; Jauch, Anna; Kharboush, I.; Remm, B.; Cremer, Thomas

Sat, 1 Jan 1977 12:00:00 +0100 https://epub.ub.uni-muenchen.de/8387/1/8387.pdf Kellerer, Albrecht M.; Ford, D.; Al-Wiswasy, M.; Camplejohn, R. S.; Aherne, W. A.