Podcasts about huntingtin

Link to bioRxiv paper: http://biorxiv.org/cgi/content/short/2023.07.31.551324v1?rss=1 Authors: Lottes, E. N., Ciger, F. H., Bhattacharjee, S., Timmins-Wilde, E. A., Tete, B., Tran, T., Matta, J., Patel, A. A., Cox, D. N. Abstract: The development of cell-type-specific dendritic arbors is integral to the proper functioning of neurons within their circuit networks. In this study, we examine the regulatory relationship between the cytosolic chaperonin CCT, key insulin pathway genes, and an E3 ubiquitin ligase (Cullin1) in homeostatic dendritic development. CCT loss of function (LOF) results in dendritic hypotrophy in Drosophila Class IV (CIV) multidendritic larval sensory neurons, and CCT has recently been shown to fold components of the TOR (Target of Rapamycin) complex 1 (TORC1), in vitro. Through targeted genetic manipulations, we have confirmed that LOF of CCT and the TORC1 pathway reduces dendritic complexity, while overexpression of key TORC1 pathway genes increases dendritic complexity in CIV neurons. Both CCT and TORC1 LOF significantly reduce microtubule (MT) stability. CCT has been previously implicated in regulating proteinopathic aggregation, thus we examined CIV dendritic development in disease conditions as well. Expression of mutant Huntingtin leads to dendritic hypotrophy in a repeat-length-dependent manner, which can be rescued by TORC1 disinhibition via Cullin1 LOF. Together, our data suggest that Cullin1 and CCT influence dendritic arborization through regulation of TORC1 in both health and disease. 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/2023.07.10.548473v1?rss=1 Authors: Singh, S. B., Rajput, S. S., Sharma, A., Ananthanarayanan, V., Nandi, A., Patil, S. P. V., majumdar, a., Subramanyam, D. Abstract: Protein aggregation is a common underlying feature of neurodegenerative disorders. Cells expressing neurodegeneration associated mutant proteins show altered uptake of ligands, suggestive of impaired endocytosis, in a manner as yet unknown. Using live cell imaging, we show that clathrin mediated endocytosis (CME) is affected due to altered actin cytoskeletal organization in the presence of Huntingtin aggregates. Additionally, we find that cells containing Huntingtin aggregates are stiffer and less viscous than their wild type counterparts due to altered actin conformation, and not merely due to the physical presence of aggregate(s). We further demonstrate that CME and cellular viscosity can be rescued by overexpressing Hip1, Arp2/3 or transient LatrunculinA treatment. Examination of other pathogenic aggregates revealed that only a subset of these display defective CME, along with altered actin organization and increased stiffness. Together, our results point to an intimate connection between functional CME, actin organization and cellular stiffness in the context of neurodegeneration. 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/2023.06.24.546334v1?rss=1 Authors: Bragg, R. M., Coffey, S. R., Cantle, J. P., Hu, S., Singh, S., Legg, S. R. W., McHugh, C. A., Toor, A., Zeitlin, S. O., Kwak, S., Howland, D., Vogt, T. F., Monga, S. P., Carroll, J. B. Abstract: Huntington's disease arises from a toxic gain of function in the huntingtin (HTT) gene. As a result, many HTT-lowering therapies are being pursued in clinical studies, including those that reduce HTT RNA and protein expression in the liver. To investigate potential impacts, we characterized molecular, cellular, and metabolic impacts of chronic HTT lowering in mouse hepatocytes. Lifelong hepatocyte HTT loss is associated with multiple physiological changes, including increased circulating bile acids, cholesterol and urea, hypoglycemia, and impaired adhesion. HTT loss causes a clear shift in the normal zonal patterns of liver gene expression, such that pericentral gene expression is reduced. These alterations in liver zonation in livers lacking HTT are observed at the transcriptional, histological and plasma metabolite level. We have extended these phenotypes physiologically with a metabolic challenge of acetaminophen, for which the HTT loss results in toxicity resistance. Our data reveal an unexpected role for HTT in regulating hepatic zonation, and we find that loss of HTT in hepatocytes mimics the phenotypes caused by impaired hepatic {beta}-catenin 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/2023.04.24.538082v1?rss=1 Authors: Mätlik, K., Baffuto, M., Kus, L., Davis, D. A., Paul, M. R., Carroll, T. S., Heintz, N. Abstract: Tissue-specific somatic expansion of the mutant Huntingtin (mHTT) CAG tract and regional degeneration of the brain are key features of Huntington's disease (HD). However, the relationships between somatic CAG expansion, death of specific cell types, and molecular events associated with these processes have not been established. Here we employed fluorescence-activated nuclear sorting (FANS) and deep molecular profiling to gain insight into the properties of cell types of the human striatum and cerebellum in HD and control donors. Expansion of the mHTT CAG tract occurs in striatal MSNs and cholinergic interneurons, in cerebellar Purkinje cells, and at the mutant ATXN3 locus in MSN nuclei from SCA3 donors. Somatic CAG tract instability in MSNs is associated with higher levels of MSH2 and MSH3. Our data indicate that somatic CAG tract expansion is not sufficient for cell death, and identify transcriptional changes associated with somatic CAG expansion and toxicity in the human striatum. 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/2023.03.04.530949v1?rss=1 Authors: Soylu-Kucharz, R., Adlesic, N., Davidsson, M., Bjorklund, T., Bjorkqvist, M., Petersen, A. Abstract: Huntington's disease is a fatal neurodegenerative disorder caused by an expanded CAG triplet repeat in the huntingtin (HTT) gene. Previous research focused on neuropathology in the striatum and its association with a typical movement disorder. Direct effects of mutant HTT (mHTT) in the striatum may cause neuropathology, although non-cell autonomous effects have also been suggested. Important non-motor features of HD include psychiatric symptoms and metabolic dysfunction, which may be linked to hypothalamic neuropathology. As hypothalamic neurons project to the ventral striatum, we hypothesized that expression of mHTT in the hypothalamus leads to disrupted neurotransmission in the ventral striatum and causes pathology. The overall aim of this study was to investigate the impact of mHTT expression in the hypothalamus on ventral striatal neuropathology and its contribution to non-HD motor symptoms. We demonstrate that selective expression of mHTT in the hypothalamus leads to the loss of dopamine and cAMP-regulated phosphoprotein (DARPP-32) immunopositive neurons in the ventral striatum in mice. Contrary to the effects of direct expression of mHTT in the hypothalamus, selective overexpression of mHTT in the ventral striatum does not affect body weight. Selective expression of mHTT in the ventral striatum leads to mHTT inclusion formation and loss of DARPP-32 neurons without affecting motor activity or anxiety-like behavior. We show that DARPP-32 neuron loss in the ventral striatum is recapitulated in the R6/2 mouse model of HD. Chemogenetic activation of hypothalamic neurons projecting to the ventral striatum had a blunted response in the R6/2 mice compared to wild-type mice, indicating a disrupted hypothalamus-ventral striatal circuitry. In summary, the expression of mHTT in the hypothalamus may impact the development of ventral striatal pathology in mice. This opens the possibility that non-cell-autonomous effects in the reward circuitry play a role in HD. 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/2023.02.23.529222v1?rss=1 Authors: Voelkl, K., Gutierrez-Angel, S., Keeling, S., Koyuncu, S., Arzberger, T., Vilchez, D., Klein, R., Dudanova, I. Abstract: Huntington's disease (HD) is a movement disorder caused by a mutation in the Huntingtin gene, that leads to severe neurodegeneration and inevitable death of the patients. Molecular mechanisms of HD are still not sufficiently understood, and no cure is currently available. Here, we demonstrate neuroprotective effects of hepatoma-derived growth factor (HDGF) in cellular and mouse models of HD. We show that HDGF expression levels inversely correlate with cellular and regional vulnerability to HD. Moreover, lack of endogenous HDGF exacerbated motor impairments and reduced life span of R6/2 Huntington's disease mice. AAV-mediated delivery of HDGF into the brain reduced mutant Huntingtin inclusion body load, but had no significant effect on motor behavior or life span. Interestingly, both nuclear and cytoplasmic versions of HDGF were equally efficient in rescuing mutant Huntingtin toxicity in cell culture models of HD. Moreover, extracellular application of a recombinant HDGF protein improved viability of mutant Huntingtin-expressing primary neurons and reduced mutant Huntingtin aggregation in neural progenitor cells differentiated from human patient-derived induced pluripotent stem cells (iPSCs). Our findings provide new insights into the pathomechanisms of HD and demonstrate neuroprotective potential of HDGF in neurodegeneration. 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/2023.02.13.528394v1?rss=1 Authors: Asgarkhani, L., Khandakar, I., Pakan, R., Swayne, T. C., Emtage, L. Abstract: Aggregation of mutant Huntingtin protein (mHtt) leads to neuronal cell death and human disease. We investigated the effect of inclusion formation on yeast cells. Previous work indicates that mHtt protein moves both in and out of inclusions, potentially undergoing refolding in the inclusion. However, the sustained influx of unfolded protein into an inclusion leads to a dramatic change from a phase-separated body to an irregular, less soluble form at a threshold inclusion size. Altered morphology was associated with a prion-like seeding that accelerated inclusion growth despite loss of soluble cytoplasmic protein. The structural change abolished exchange of material between the inclusion and the cytosol and resulted in early cell death. Affected cells continued to divide occasionally, giving rise to daughters with a similar phenotype. Most newly born cells were able to reverse the prion-like aggregation, restoring both soluble cytoplasmic protein and a normal inclusion structure. 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/2023.01.28.526012v1?rss=1 Authors: YIGIT, E. N., AYDIN, M. S., AKSAN KURNAZ, I., EROGLU, E., Ozturk, G. Abstract: Huntington's disease is a neurodegenerative disease caused by expansion of CAG repeats in exon-1 of Huntingtin (HTT) gene leading to production of mutant Huntingtin (mHtt) protein. Htt protein is known to play crucial roles in regulation of cytoskeletal dynamics and vesicular transport in physiological conditions. By combining in vitro time-lapse imaging and correlative light and electron microscopy (CLEM), we investigated the subcellular dynamics of mHtt during the process aggregate formation. Here we show that distribution of F-actin is affected by mHtt aggregation. F-actin tends to relocate from the peripheral to perinuclear area in cells with mHtt aggregates, possibly caused by sequestration of F-actin from cell membrane to aggregation zones. In accordance with this, mHtt in hippocampal neurons were aggregated into axonal varicosities together with F-actin as they have higher F-actin expression in their neurites compared to their soma. Additionally, correlative light and electron microscopy (CLEM) revealed increased mitochondrial accumulation at the periphery of mHtt aggregates which is surrounded by a F-actin mesh. Mitochondria targeted HyPerRed, a genetically encoded hydrogen peroxide sensor, revealed that oxidative stress in mHtt expressing cells increased. Thus, our findings give new insights about the pathology caused by mHtt through interplay of aggregates with F-actin cytoskeleton and mitochondrial oxidative stress. 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/2023.01.26.525697v1?rss=1 Authors: Sapp, E., Shing, K., Boudi, A., Liu, S., Seeley, C., Marchionini, D., DiFiglia, M., Kegel-Gleason, K. B. Abstract: Lowering mutant huntingtin (mHTT) transcription is a promising approach to treat Huntington's disease (HD). Using a mHtt-inducible mouse model we analyzed mHtt lowering initiated at different ages and sustained for different time-periods. mHTT protein in cytoplasmic and synaptic compartments of the caudate putamen, which is most affected in HD, was reduced 38-52%. Little or no lowering of mHTT occurred in nuclear and perinuclear regions where aggregates formed at 12 months of age. mHtt transcript repression partially or fully preserved select striatal proteins (SCN4B, PDE10A). Total lipids in striatum were reduced in LacQ140 mice at 9 months and preserved by early partial mHtt lowering. The reduction in total lipids was due in part to reductions in subclasses of ceramide (Cer), sphingomyelin (SM), and monogalactosyl diglyceride (MGDG), which are known to be important for white matter structure and function. Lipid subclasses- phosphatidylinositol (PI), phosphatidylserine (PS), and bismethyl phosphatidic acid (BisMePA)- were also changed in LacQ140 mice. Levels of all subclasses other than ceramide were preserved by early mHtt lowering. Our findings suggest that early and sustained reduction in mHtt can prevent changes in levels of select striatal proteins and most lipids but a misfolded, degradation-resistant form of mHTT hampers some benefits in the long term. 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/2022.12.05.519070v1?rss=1 Authors: Cariulo, C., Martufi, P., Verani, M., Toledo, L. S., Lee, R., Dominguez, C., Petricca, L., Caricasole, A. Abstract: N-terminal phosphorylation at residues T3 and S13 is believed to have important beneficial implications for the biological and pathological properties of mutant huntingtin, where IKBKB was identified as a candidate regulator of huntingtin N-terminal phosphorylation. The paucity of mechanistic information on IKK pathways, together with the lack of sensitive methods to quantify endogenous huntingtin phosphorylation, prevented detailed study of the role of IKBKB in Huntington's disease. Using novel ultrasensitive assays, we demonstrate that IKBKB can regulate endogenous S13 huntingtin phosphorylation in a manner dependent on its kinase activity and known regulators. We found that the ability of IKBKB to phosphorylate endogenous huntingtin S13 is mediated through a non-canonical IRF3-mediated IKK-pathway, distinct from the established involvement of IKBKB in mutant huntingtin's pathological mechanisms mediated via the canonical pathway. Furthermore, increased huntingtin S13 phosphorylation by IKBKB resulted in decreased aggregation of mutant huntingtin in cells, again dependent on its kinase activity. These findings point to a non-canonical IKK-pathway linking S13 huntingtin phosphorylation to the pathological properties of mutant huntingtin aggregation, thought to be significant to Huntington's disease. 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/2022.10.16.512122v1?rss=1 Authors: Desai, M., Singh, H., Deo, A., Naik, J., Bose, T., Majumdar, A. Abstract: Orb2 the Drosophila homolog of Cytoplasmic polyadenylation element binding protein (CPEB) forms prion-like oligomers. These oligomers consist of Orb2A and Orb2B isoforms and their formation are dependent on the oligomerization of the Orb2A isoform. Drosophila with a mutation diminishing Orb2A's prion-like oligomerization forms long-term memory but fails to maintain it over time. Since, this prion-like oligomerization of Orb2A plays a crucial role in the maintenance of memory, here we aim to find what regulates this oligomerization. In an immunoprecipitation-based screen, we identify interactors of Orb2A in the Hsp40 and Hsp70 families of proteins. Amongst these, we find an Hsp40 family protein Mrj as a regulator of the conversion of Orb2A to its prion-like form. Mrj interacts with Hsp70 proteins and acts as a chaperone by interfering with the aggregation of pathogenic Huntingtin. Unlike its mammalian homolog, we find Drosophila Mrj is neither an essential gene nor causes any gross neurodevelopmental defect. We observe a loss of Mrj results in a reduction in Orb2 oligomers. Further, the knockdown of Mrj in the mushroom body neurons results in a deficit in long-term memory. Our work implicates a chaperone Mrj in mechanisms of memory regulation through controlling the oligomerization of Orb2A and its association with the translating polysomes. 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/2022.10.05.510980v1?rss=1 Authors: Barron, J. C., Nafar, F., Parsons, M. P. Abstract: Huntingtin (HTT), an exceptionally large protein with hundreds of interacting partners within the central nervous system, has been extensively studied due to its role in Huntington's disease (HD) pathology. HD is a monogenic disorder caused by a polyglutamine repeat expansion in the HTT gene, which results in the production of a pathogenic mutant huntingtin (mHTT) protein, and toxic effects of this mutant protein in the context of HD have been well-established. Less-established, however, is the role of wild type HTT (wtHTT) in the adult brain, particularly in areas outside the corticostriatal pathway. wtHTT has previously been suggested to play a vital role in cellular functions that promote synapse homeostasis, such as fast axonal transport of synaptic cargo, vesicle replenishment and receptor localization and stability. Synaptic dysfunction precedes and predicts cell death in many neurodegenerative diseases including HD (termed synaptopathies) and whether proper synaptic transmission can be maintained without wtHTT in extrastriatal brain areas such as the hippocampus remains unknown. Consequences of wtHTT reduction in the adult brain are of particular importance as clinical trials for many non-selective HTT-lowering therapies for HD are underway, which are unable to distinguish between mHTT and wtHTT, and therefore reduce levels of both proteins. We investigated the consequences of wtHTT loss of function in the CA3-CA1 pathway of the adult hippocampus using a conditional knockout mouse model and found that 1-2 month deletion of wtHTT in excitatory hippocampal neurons inhibits post-tetanic potentiation and completely abolishes NMDA receptor-dependent long-term potentiation in these animals. These data reveal a novel role of wtHTT as an essential regulator of short- and long-term plasticity in the adult hippocampus. Copy rights belong to original authors. Visit the link for more info Podcast created by PaperPlayer

Link to bioRxiv paper: http://biorxiv.org/cgi/content/short/2022.08.26.505426v1?rss=1 Authors: Birolini, G., Valenza, M., Ottonelli, I., Talpo, F., Minoli, L., Cappelleri, A., Bombaci, M., Caccia, C., Leoni, V., Passoni, A., Favagrossa, M., Nucera, M. R., Colombo, L., Paltrinieri, S., Bagnati, R., Duskey, J. T., Caraffi, R., Vandelli, M. A., Taroni, F., Salmona, M., Scanziani, E., Biella, G., Ruozi, B., Tosi, G., Cattaneo, E. Abstract: Huntingtons disease (HD) has been linked to reduced synthesis of cholesterol in the brain. Its exogenous delivery to the brain has been shown to be beneficial in the rapidly progressing R6/2 mouse model. Here we used an advanced formulation of brain-permeable nanoparticles (NPs) loaded with cholesterol and called hybrid-g7-NPs-chol, to explore the long-term therapeutical potential of cholesterol administration to the brain of the slow-progressing zQ175DN knock-in HD mouse model. We show that one cycle treatment with hybrid-g7-NPs-chol, administered in the pre-symptomatic or symptomatic phases, is sufficient to completely normalize cognitive defects up to 5 months, as well as to improve other behavioral and neuropathological parameters. Instead, two cycles of hybrid-g7-NPs-chol are needed to achieve long-lasting therapeutic benefits for 12 months without severe inflammatory side-effects. Sustained cholesterol delivery to the brain of zQ175DN mice also reduces mutant Huntingtin aggregates both in striatum and cortex and completely normalizes glutamatergic communication in the striatal medium spiny neurons compared to saline-treated HD mice. These results show that cholesterol delivery via brain-permeable NPs is a safe and versatile therapeutic option for lastingly reversing HD-related behavioral decline and neuropathological signs, highlighting the translational potential of cholesterol-based strategies in HD patients. Copy rights belong to original authors. Visit the link for more info Podcast created by PaperPlayer

In this week's tea-riffic episode, researchers test the effects of green tea on Huntington's disease! Papers referenced: "Green tea and cancer and cardiometabolic diseases: a review of the current epidemiological evidence" "Green tea infusion alleviates neurodegeneration induced by mutant Huntingtin in Drosophila"

Link to bioRxiv paper: http://biorxiv.org/cgi/content/short/2020.10.13.337154v1?rss=1 Authors: Hecklau, K., Mueller, S., Koch, S., Mehkary, M. H., Kilic, B., Harms, C., Boehm-Sturm, P., Yildirim, F. Abstract: Huntington's disease (HD) is an autosomal dominant neurodegenerative disease characterized by a late clinical onset of psychiatric, cognitive, and motor symptoms. Transcriptional dysregulation is an early and central disease mechanism which is accompanied by epigenetic alterations in HD. Previous studies demonstrated that targeting transcriptional changes by inhibition of histone deacetylases (HDACs), especially the class I HDACs, provides therapeutic effects. Yet, their exact mechanisms of action and the features of HD pathology, on which these inhibitors act remain to be elucidated. Here, using transcriptional profiling, we found that selective inhibition of HDAC1 and HDAC3 by RGFP109 repaired the expression of a number of genes, including the transcription factor genes Neurod2 and Nr4a2, and 43% of the gene sets that were dysregulated by mutant Huntingtin expression in the striatum and improved motor skill learning deficit in the R6/1 mouse model of HD. RGFP109-treated R6/1 mice showed improved coordination on the RotaRod over four consecutive trials, while vehicle-treated R6/1 animals displayed no improvement in coordination skills and fell 50 seconds earlier off the rod in the fourth trial. We also found, by volumetric MRI, a widespread brain atrophy in the R6/1 mice at the symptomatic disease stage, on which RGFP109 showed a modest effect. Collectively, our combined work presents new evidence for specific HDAC1 and HDAC3 inhibition as a therapeutic strategy for alleviating the phenotypic and molecular features of HD. Copy rights belong to original authors. Visit the link for more info

Link to bioRxiv paper: http://biorxiv.org/cgi/content/short/2020.08.13.249201v1?rss=1 Authors: Moharir, S. C., Raghawan, A. K., Swarup, G. Abstract: Optineurin (OPTN), a cytoplasmic adaptor protein involved in cargo selective autophagy of bacteria, damaged mitochondria and mutant protein aggregates, is frequently seen in pathological structures containing protein aggregates, associated with several neurodegenerative diseases. However, the function of OPTN in these protein aggregates is not known. Here, we have explored the role of OPTN in mutant protein aggregation and in cytoprotection from toxicity of mutant proteins. Mutant huntingtin (mHtt) and mutant ataxin-3 (mAtax-3) showed reduced formation of aggregates in Optn-/- mouse embryonic fibroblasts as compared with wild type cells. Co-expression of OPTN enhanced aggregate formation by mHtt and mAtax-3 in Optn-/- cells. C-terminal domain of OPTN (412-577 amino acids) was necessary and sufficient to promote aggregate formation by these mutant proteins. The E478G mutant of OPTN, defective in ubiquitin-binding and autophagy, was also able to promote aggregation of mHtt and mAtax-3. OPTN and its C-terminal domain form a complex with the chaperone HSP70 known to promote mutant protein aggregation. Overexpression of mHtt or mAtax-3 induced more cell death in Optn-/- cells compared with wild type cells. Importantly, compared to wild type cells, Optn-deficient cells having mHtt or mAtax-3 aggregates showed higher level of cell death in neuronal (N2A) and non-neuronal cells. Our results show that OPTN promotes formation of mutant huntingtin and mutant ataxin-3 aggregates, and this function of OPTN might be mediated through interaction with HSP70 chaperones. Our results also show that OPTN reduces cytotoxicity caused by these mutant protein aggregates. Copy rights belong to original authors. Visit the link for more info

Link to bioRxiv paper: http://biorxiv.org/cgi/content/short/2020.07.29.226977v1?rss=1 Authors: Riguet, N., Mahul-Mellier, A.-L., Maharjan, N., Burtscher, J., Patin, A., Croisier, M., Knott, G. W., Reiterer, V., Farhan, H., Lashuel, H. Abstract: Despite the strong evidence linking the aggregation of the Huntingtin protein (Htt) to the pathogenesis of Huntington's disease (HD), the mechanisms underlying Htt aggregation and neurodegeneration remain poorly understood. Herein, we investigated the ultrastructural properties and protein composition of Htt inclusions in cells overexpressing mutant exon1 of the Htt protein. Our findings provide novel insight into the ultrastructural properties of cytoplasmic and nuclear Htt inclusions and their mechanisms of formation. We show that Htt inclusion formation and maturation are complex processes that, although initially driven by polyQ-dependent Htt aggregation, also involve 1) polyQ and PRD domain-dependent sequestration of lipids and cytoplasmic and cytoskeletal proteins related to HD dysregulated pathways; 2) recruitment and accumulation of remodeled or dysfunctional membranous organelles; and 3) impairement of the protein quality control and degradation machineries. Interestingly, nuclear and cytoplasmic Htt inclusions exhibited distinct biochemical composition and ultrastructural properties, suggesting different formation mechanisms and toxicity. Copy rights belong to original authors. Visit the link for more info

Link to bioRxiv paper: http://biorxiv.org/cgi/content/short/2020.07.23.218347v1?rss=1 Authors: Coffey, S. R., Andrew, M., Ging, H., Hamilton, J., Flower, M., Kovalenko, M., Bragg, R. M., Cantle, J. P., McHugh, C. A., Carrillo, J. M., Rodier, J.-A., Marchionini, D. M., Wilkinson, H. A., Kwak, S., Howland, D. S., Bennett, C. F., Mouro Pinto, R., Auburger, G., Zeitlin, S. O., Kordasiewicz, H. B., Tabrizi, S. J., Wheeler, V. C., Carroll, J. B. Abstract: Expanded trinucleotide repeats cause many human diseases, including Huntington's disease (HD). Recent studies indicate that somatic instability of these repeats contributes to pathogenesis in several expansion disorders. We find that lowering huntingtin protein (HTT) levels reduces somatic instability of both the Htt and Atxn2 CAG tracts in knockin mouse models, and the HTT CAG tract in human iPSC-derived neurons, revealing an unexpected role for HTT in regulating somatic instability. Copy rights belong to original authors. Visit the link for more info

Link to bioRxiv paper: http://biorxiv.org/cgi/content/short/2020.07.23.217968v1?rss=1 Authors: Chiki, A., Ricci, J., Hegde, R. N., Abriata, L. A., Reif, A., Lashuel, H. A. Abstract: Posttranslational modifications (PTMs) within the first 17 amino acids (Nt17) of exon1 of the Huntingtin protein (Httex1) play important roles in modulating its cellular properties and functions in health and disease. In particular, phosphorylation of threonine and serine residues (T3, S13, and/or S16) has been shown to inhibit Htt aggregation in vitro and inclusion formation in cellular and animal models of Huntingtons disease (HD). In this manuscript, we describe a new and simple methodology for producing milligram quantities of highly pure wild type or mutant Httex1 proteins that are site-specifically phosphorylated at T3 or at both S13 and S16. This advance was enabled by 1) the discovery and validation of novel kinases that efficiently phosphorylate Httex1 at S13 and S16 (TBK1), at T3 (GCK) or T3 and S13 (TNIK and HGK); and, 2) the development of an efficient methodology for producing recombinant native Httex1 proteins using a SUMO-fusion expression and purification strategy. As proof of concept, we demonstrate how this method can be applied to produce Httex1 proteins that are both site- specifically phosphorylated and fluorescently labeled or isotopically labeled. Together, these advances should increase access to these valuable tools and expand the range of methods and experimental approaches that can be used to elucidate the mechanisms by which phosphorylation influences Httex1 structure, aggregation, interactome and function(s) in health and disease. Copy rights belong to original authors. Visit the link for more info

Link to bioRxiv paper: http://biorxiv.org/cgi/content/short/2020.06.04.132571v1?rss=1 Authors: Pearl, J. R., Shetty, A. C., Cantle, J. P., Bergey, D. E., Bragg, R. M., Coffey, S. R., Kordasiewicz, H. B., Hood, L. E., Price, N. D., Ament, S. A., Carroll, J. B. Abstract: Progressive striatal gene expression changes and epigenetic alterations are a prominent feature of Huntingtons disease (HD), but direct relationships between the huntingtin (HTT) protein and chromatin remain poorly described. Here, using chromatin immunoprecipitation and sequencing (ChIP-seq), we show that HTT reproducibly occupies specific locations in the mouse genome, including thousands of genomic loci that are differentially occupied in striatal tissue from a knock-in mouse model of HD (B6.HttQ111/+) versus wildtype controls. ChIP-seq of histone modifications, generated in parallel, revealed genotype-specific colocalization of HTT with trimethylation of histone 3 lysine 27 (H3K27me3), a repressive chromatin mark. Close to genes that are differentially regulated in HD, greater HTT occupancy in HttQ111/+ vs. wildtype mice predicted increased H3K27me3, reduced histone 3 lysine 4 (H3K4me3, a marker of poised and active promoters), and down-regulated gene expression. Altered huntingtin-chromatin interactions may therefore play a direct role in driving transcriptional dysregulation in HD. Copy rights belong to original authors. Visit the link for more info

Link to bioRxiv paper: http://biorxiv.org/cgi/content/short/2020.05.27.119552v1?rss=1 Authors: Xu, S., Li, G., Ye, X., Chen, D., Chen, Z., Xu, Z., Ye, L., Stimming, E. F., Marchionini, D., Zhang, S. Abstract: Perturbation of Huntingtin (HTT)s physiological function is one postulated pathogenic factor in Huntingtons disease (HD). However, little is known how HTT is regulated in vivo. In a proteomic study, we isolated a novel [~]40kDa protein as a strong binding partner of Drosophila HTT and demonstrated it was the functional ortholog of HAP40, an HTT associated protein shown recently to modulate HTTs conformation but with unclear physiological and pathologic roles. We showed that in both flies and human cells, HAP40 maintained conserved physical and functional interactions with HTT, loss of HAP40 resulted in similar phenotypes as HTT knockout, including animal viability and autophagy, and more strikingly, HAP40 depletion significantly reduced the levels of endogenous HTT, while HAP40 was mostly degraded via the proteasome in the absence of HTT. Interestingly, polyglutamine expansion in HTT did not affect its affinity for HAP40. However, HAP40 modulated HD pathogenesis in Drosophila model by regulating the overall protein levels and the toxicity of full-length mutant HTT. Together, our study uncovers a conserved mechanism governing the stability and in vivo functions of HTT, and demonstrates that HAP40 is a central and positive regulator of HTT, a potential modulator of HD pathogenesis and a promising candidate for "HTT-lowering" strategy against HD. Copy rights belong to original authors. Visit the link for more info

Link to bioRxiv paper: http://biorxiv.org/cgi/content/short/2020.05.13.092742v1?rss=1 Authors: Birolini, G., Valenza, M., DiPaolo, E., Vezzoli, E., Talpo, F., Maniezzi, C., Caccia, C., Leoni, V., Bocchi, V. D., Conforti, P., Sogne, E., Petricca, L., Cariulo, C., Verani, M., Caricasole, A., Falqui, A., Biella, G., Cattaneo, E. Abstract: A variety of pathophysiological mechanisms are implicated in Huntington's disease (HD). Among them, reduced cholesterol biosynthesis has been detected in the HD mouse brain from pre-symptomatic stages, leading to diminished cholesterol synthesis, particularly in the striatum. In addition, systemic injection of cholesterol-loaded brain-permeable nanoparticles ameliorates synaptic and cognitive function in a transgenic mouse model of HD. To identify an appropriate treatment regimen and gain mechanistic insights into the beneficial activity of exogenous cholesterol in the HD brain, we employed osmotic mini-pumps to infuse three escalating doses of cholesterol directly into the striatum of HD mice in a continuous and rate- controlled manner. All tested doses prevented cognitive decline, while amelioration of disease-related motor defects was dose-dependent. In parallel, we found morphological and functional recovery of synaptic transmission involving both excitatory and inhibitory synapses of striatal medium spiny neurons. The treatment also enhanced endogenous cholesterol biosynthesis and clearance of mutant Huntingtin aggregates. These results indicate that cholesterol infusion to the striatum can exert a dose-dependent, disease-modifying effect and may be therapeutically relevant in HD. Copy rights belong to original authors. Visit the link for more info

In our second episode, the HOPES podcast follows Nancy Wexler's hunt to discover the Huntingtin gene. We used music from freesound.org and freemusic archives. Today you heard: "Slow Sad Tones" by TJ Mothy "Treasure Hunt (Instrumental)" by Simon Panrucker

After having a family history of Huntington's Disease, Antonio Maltese was pre-symptomatically genetically diagnosed with the disease himself. This diagnosis has motivated Antonio to become a fierce patient advocate with big plans to change the future of people with Huntington’s disease. Huntington’s Disease is progressive brain disorder that causes uncontrolled movements, emotional problems, and loss of thinking ability. This neurodegenerative disease is caused by an excess of CAG repeats in the Huntingtin gene (HTT). Unaffected people have this DNA sequence repeated 10 to 35 times. Those that may be affected have 35-39 repeats and those with over 40 repeats will develop Huntington’s Disease. This disease is inherited in an autosomal dominant pattern, meaning if a parent has Huntington’s Disease their child has a 50% chance of inheriting the disease. Antonio shares about his paternal grandmother who had Huntington's Disease and why he decided to pursue genetic testing. The biggest breakthrough in neurodegenerative diseases for 50 years recently occurred, 46 patients had their Huntington genes silenced at the University College London as part of a research study. Antonio I and discuss the impact this could have on Huntington's Disease and other neurodegenerative diseases. Antonio shares the resources he has benefited from including HDBuzz and the blogs where he has collected his research for others: huntingtonsinitiative.blogspot.com and chuffed.org. Don't forget to follow the show on Instagram, Twitter, and Facebook!

Wed, 5 Aug 2015 12:00:00 +0100 https://edoc.ub.uni-muenchen.de/18537/ https://edoc.ub.uni-muenchen.de/18537/1/Kukushkin_Yury.pdf Kukushkin, Yury

William Pryor and Srinivasa Subramaniam report that a mutant form of huntingtin that is associated with early-onset Huntington's disease promotes anabolic signaling that contributes to disease symptoms in mice.

International Parkinson and Movement Disorder Society Movement Disorders Journal podcast September 2014

PRE-RECORDED: Our incredible special guest today is Stacy Brookhyser, mother of twins free of HD. She is a super duper proactive HD warrior who is spreading the word about a new procedure to stop HD in its tracks.   The Procedure: IVF/PGD Yes, you can stop Huntington's Disease in the future generations of your family! With the help of skilled medical professionals, YOU have the ability to prevent your children from inheriting HD. After in-vitro fertilization (IVF), embryos can be tested using pre-implantation genetic diagnosis (PGD) to determine their genetic makeup. When the embryos contain eight cells, they are tested for the HD mutation in the Huntingtin gene. Only embryos with the unaffected gene are transferred to the mother. These embryos will never get HD or transmit it to their children. The procedure essentially eliminates HD from that family line. Forever! Visit Stacy's website: www.hdfreewithpgd.com Contact: stacybrook@aol.com  

Monday, June 27, 2011 - Our incredible special guest is Stacy Brookhyser (CAG 42), mother of twins free of HD. She is a super duper proactive HD warrior who is spreading the word about a new procedure to stop HD in its tracks. Planning an HD-free family with IVF/PGD Yes, you can stop Huntington's Disease in the future generations of your family!  With the help of skilled medical professionals, YOU have the ability to prevent your children from inheriting HD. What is PGD After in-vitrofertilization (IVF), embryos can be tested using pre-implantation genetic diagnosis (PGD) to determine their genetic makeup.  When the embryos contain eight cells, they are tested for the HD mutation in the Huntingtin gene.  Only embryos with the unaffected gene are transferred to the mother.  These embryos will never get HD or transmit it to their children.  The procedure essentially eliminates HD from that family line.  Forever! Stacy's website: www.hdfreewithpgd.com

Professor Jenny Morton provides new insight into the cognitive abilities of the supposedly dim-witted sheep and explains how these quick learning animals can be used to model Huntington's Disease... Like this podcast? Please help us by supporting the Naked Scientists

Professor Jenny Morton provides new insight into the cognitive abilities of the supposedly dim-witted sheep and explains how these quick learning animals can be used to model Huntington's Disease... Like this podcast? Please help us by supporting the Naked Scientists

Ein lebender Organismus ist unter anderem durch seine Fähigkeit zum präzisen Auf- und Zusammenbau höherer molekularer Strukturen charakterisiert, wobei die Faltung und Assemblierung von Proteinen eine bedeutende Rolle spielt. Die Proteinfaltung wird durch molekulare Chaperone unterstützt und optimiert, bis ein Protein seine native, biologisch funktionelle Struktur eingenommen hat. Durch exogene Einflüsse oder endogene Veränderungen eines Proteins, z.B. bei neurodegenerativen Erkrankungen wie M. Alzheimer, M. Parkinson oder Chorea Huntington, oder des gesamten Proteinnetzwerkes, kann Proteinfehlfaltung, Aggregation und die Ausbildung amyloider Strukturen, verbunden mit Zytotoxizität, auftreten. Die zur Fehlfaltung und Bildung ähnlicher amyloider Aggregate führenden strukturellen Determinanten der Zytotoxizität, verursacht durch Proteine unterschiedlicher Primärstruktur und Länge, sind nur unzureichend erforscht. Eine Hypothese besagt, dass lösliche intermediäre Oligomere der aggregierenden Proteine die toxische Spezies in einem wahrscheinlich multifunktionellen pathogenen Geschehen darstellen. Es gibt Hinweise, dass eine zusammenbrechende Proteostase verbunden mit einer zu geringeren Kapazität molekularer Chaperone zu den deletären Effekten führt. Auch ist nicht abschließend geklärt, ob und zu welchem Anteil die Toxizität durch Aggregation des Proteins und damit verbundener erhöhter Pathogenität bedingt ist, oder inwieweit durch einen Funktionsverlust des fehlgefalteten Proteins selbst. Um zytotoxische Effekte in humanen Zellen zu analysieren, wurden de novo generierte beta-Faltblattproteine untersucht, welche durch Aggregation in der Zelle keine Autofunktionsstörung auslösen sollten. Es wurde gezeigt, dass diese artifiziellen Proteine in HEK293T-Zellen amyloide Aggregate bildeten und zytotoxisch wirkten, im Vergleich zu de novo generierten alpha-helikalen Proteinen, welche löslich und homogen in der Zelle verteilt vorlagen und nahezu keine Zytotoxizität aufwiesen. Drei aus einer kombinatorischen Bibliothek ausgewählte de novo amyloide Proteine, beta4, beta17 und beta23, waren zytotoxisch mit der Gradierung beta4 < beta17 < beta23, sie induzierten Apoptose und veränderten die Zellmorphologie. Die Zytotoxizität korrelierte mit vorhandenen präfibrillären, intermediären Oligomeren. Die Proteine beeinträchtigten die Rückfaltung von GFP-Luciferase in gleicher Abstufung, ebenso eine Induktion der Stressantwort und die Proteinbiogenese. Die Aggregate colokalisierten mit GFP-Luciferase, jedoch nicht mit GFP. Eine massenspektrometrische Untersuchung der Interaktionspartner der drei de novo amyloiden Proteine in Kombination mit SILAC und Co-IP wies Interaktionen mit metastabilen Proteinen essentieller zellulärer Funktionen nach, dabei wurde Hsp110 als stark angereichertes Chaperon unter den Interaktoren identifiziert. Eine Überexpression von Hsp110 verminderte die Zytotoxizität der de novo Proteine beta4 und beta17, jedoch nicht beta23. Hsp110 war ebenfalls in der Lage, Aggregate teilweise zu solubilisieren und eine normalisierte Zellmorphologie wieder herzustellen. Um einen beta-Strang verkürzte oder verlängerte Mutanten der semitoxischen beta-Faltblattproteine beta4 und beta17 wiesen eine erhöhte Zytotoxizität auf, so dass wahrscheinlich generell beta-Faltblattproteine mit einer ungeraden Anzahl an beta-Strängen toxischer sind als ihre Derivate mit gerader Anzahl an beta-Strängen, da ungepaarte reaktive beta-Stränge vorliegen dürften. Zusammenfassend stellen die de novo beta-Faltblattproteine ein attraktives Modell dar, um aggregierende, amyloide Proteine ohne biologische Funktion in vivo zu untersuchen. Inkubation humaner Zellen mit dem Prolin-Analogon Azetidin-2-carbonsäure führte in Anwesenheit eines proteasomalen Inhibitors zur Verstärkung der Zytotoxizität, es entstanden amyloide Aggregate und präfibrilläre Intermediate, so dass die Hypothese der Verstärkung von Funktion und Pathogenität durch Aggregation in diesem System weiter untermauert wurde. Expression von Huntingtin mit expandierter PolyQ-Sequenz und einem angefügten hydrophoben CL1-Degron führte zu einer Erhöhung der Löslichkeit, zu verstärkter Inhibition des Ubiquitin-Proteasom-Systems und zu erhöhter Zytotoxitzität im Vergleich zu expandiertem Huntingtin ohne CL1-Degron. Die Zytotoxizität des mit Degron versehenen Huntingtins konnte mittels Überexpression von expandiertem Huntingtin ohne Degron durch Coaggregation verringert werden. Die Ergebnisse sprechen für die Hypothesen, dass präfibrilläre Intermediate die maßgeblichen zytotoxischen Spezies darstellen, während große Aggregate eine protektive Funktion einnehmen können. Eine Überexpression fehlfaltender Proteine kann in multifaktorieller Weise zur Interaktion mit essentiellen zellulären Proteinen führen und die Funktion metastabiler Proteine beeinträchtigen, was u.a. im Falle der de novo amyloiden Proteine zur Inhibition der Proteinbiogenese und der HSR führt. Akkumulation endogener fehlgefalteter Proteine durch proteasomale Inhibition legt den Mechanismus einer Verstärkung der Zytotoxizität durch amyloide, aggregierende Proteine per se nahe.

A small G protein may limit the toxicity of mutant huntingtin to the brain.

Polyglutaminerkrankungen sind neurodegenerative Erkrankungen mit fatalem Verlauf, die sich durch selektive neuronale Degeneration und die Bildung intrazellulärer Aggregate auszeichnen. Verursacht werden sie durch eine Expansion einer Polyglutaminsequenz in einem für die Erkrankung spezifischen Protein, die Fehlfaltung und Aggregation des entsprechenden Proteins bewirkt. Die Aggregation wirkt dabei neurotoxisch, wobei Toxizität hauptsächlich durch lösliche Intermediate des Aggregationsprozesses vermittelt wird. Zur Untersuchung der frühen Aggregationsphase und der späteren Elongationsphase wurden in dieser Arbeit verschiedene fluoreszenzbasierte Methoden etabliert. Mit Hilfe dieser Methoden konnte gezeigt werden, dass nach proteolytischer Spaltung von GST-Htt-Exon1 das Monomer eine Konformationsumlagerung durchmacht, die von einer Dimerisierung oder Oligomerisierung gefolgt wird. Dimere oder Oligomere bilden dabei eine kompakte Struktur aus. Wachstum der Fibrillen erfolgt durch Anlagerung von Monomeren oder einer anderen bisher nicht identifizierten Spezies. Durch Distanzmessungen innerhalb verschiedener Spezies konnte gezeigt werden, dass unlösliche Spezies eine kompakte Struktur aufweisen, die spezifisch für unlösliche Spezies ist. Lösliche Spezies liegen dagegen in einer expandierteren Konformation vor. Molekulare Chaperone üben oftmals eine protektive Funktion auf Neuronen in neurodegenerativen Erkrankungen aus. In dieser Arbeit wurde untersucht, inwieweit das eukaryontische Chaperonin TRiC, das in einem RNA-interference screen als potentieller Suppressor der Huntingtin-Aggregation identifiziert wurde, Aggregation modulieren kann. Gereinigtes TRiC hat keinen Einfluss auf die frühe Phase der Htt-Exon1-Aggregation, vielmehr inhibiert es die Elongation von fibrillären Strukturen, indem es mit Htt-Exon1-Oligomeren interagiert. Diese Interaktion ist transient und ATP-unabhängig. Im Gegensatz dazu interagiert TRiC in Kooperation mit dem Hsp70/40-System mit Htt-Exon1-Monomeren und verhindert die Nukleation der Aggregation. Stattdessen wird ein „gefaltetes“ Htt-Exon1-Produkt mit einer neuartigen Konformation gebildet, das löslich, nicht-fibrillär und nicht-toxisch ist und ~500 kDa-Oligomere ausbildet. Diese Interaktion ist kooperativ, sequentiell und benötigt ATP, ähnelt also der kooperativen Interaktion von TRiC und Hsp70/40 in der de novo-Proteinfaltung und stellt möglicherweise einen natürlichen Faltungsweg für Huntingtin dar.

Link to bioRxiv paper: http://biorxiv.org/cgi/content/short/2020.04.21.052506v1?rss=1 Authors: Saudou, F., Bruyere, J., Abada, Y.-S., Vitet, H. M., Fontaine, G., Deloulme, J.-C., Cës, A., Denarier, E., Pernet-Gallay, K., Andrieux, A., Humbert, S., Potier, M.-C., Delatour, B. Abstract: Studies have suggested that amyloid precursor protein (APP) regulates synaptic homeostasis, but the evidence has not been consistent. In particular, signaling pathways controlling APP transport to the synapse in axons and dendrites remain to be identified. Having previously shown that Huntingtin (HTT), the scaffolding protein involved in Huntington's disease, regulates neuritic transport of APP, we used a microfluidic corticocortical neuronal network-on-a-chip to examine APP transport and localization to the pre- and post-synaptic compartments. We found that HTT, upon phosphorylation by the Ser/Thr kinase Akt, regulates APP transport in axons but not dendrites. Expression of an unphosphorylatable HTT decreased axonal anterograde transport of APP, reduced presynaptic APP levels, and increased synaptic density. Ablating in vivo HTT phosphorylation in APPPS1 mice, which overexpress APP, reduced presynaptic APP levels, restored synapse number and improved learning and memory. The Akt-HTT pathway and axonal transport of APP thus regulate APP presynaptic levels and synapse homeostasis. Copy rights belong to original authors. Visit the link for more info