Project description:Despite growing descriptions of wild-type Huntingtin's (wt-HTT) roles in both adult brain function and, more recently, development, several clinical trials are exploring HTT-lowering approaches that target both wt-HTT and the mutant isoforms (mut-HTT) responsible for Huntington's disease (HD). This non-selective targeting is based on the autosomal dominant inheritance of HD, supporting the idea that mutant HTT exerts its harmful effects through a toxic gain-of-function or a dominant-negative mechanism. However, the precise amount of wt-HTT needed for healthy neurons in adults and during development remains unclear. In this study, we address this question by examining how wt-HTT loss affects human neuronal network formation, synaptic maturation, and homeostasis in vitro. Our findings establish a role of wt-HTT in the maturation of dendritic arborization and the acquisition of network-wide synchronized activity by human cortical neuronal networks modeled in vitro. Interestingly, the network synchronization defects only became apparent when more than two-thirds of the wt-HTT protein was depleted. Our study underscores the critical need to precisely understand wt-HTT's role in neuronal health. It also emphasizes the potential risks of excessive wt-HTT loss associated with non-selective therapeutic approaches targeting both wt and mutant HTT isoforms in HD patients.
Project description:Huntington’s disease (HD) is a fatal neurodegenerative disorder that is caused by the expansion of CAG repeats in the HTT gene, which results in a long polyglutamine (polyQ) tract in the huntingtin protein (HTT). In this study, we searched for networks of deregulated RNAs that contribute to initial transcriptional changes in HD neuronal cells and HTT-deficient cells. We used RNA-seq (including small RNA sequencing) to analyze a set of isogenic, human induced pluripotent stem cell (iPSC)-derived neural stem cells (NSCs); and we observed numerous changes in gene expression and substantial dysregulation of miRNA expression in HD and HTT-knockout (HTT-KO) cell lines. The gene set that was upregulated in both HD and HTT-KO cells was enriched in genes that are associated with DNA binding and regulation of transcription. For both of these models, we confirmed the substantial upregulation of the transcription factors (TFs) TWIST1, SIX1, TBX1, TBX15, MSX2, MEOX2 and FOXD1 in NSCs and medium spiny neuron (MSN)-like cells. Moreover, we identified miRNAs that were consistently deregulated in HD and HTT-KO NSCs and MSN-like cells, including miR-214, miR-199, and miR-9. We suggest that these miRNAs function in the network that regulates TWIST1 and HTT expression via regulatory feed-forward loop (FFL) in HD. Additionally, we reported that the expression of selected TFs and miRNAs tended to progressively change during the neural differentiation of HD cells, what was not observed in HTT-KO model. Based on comparing the HD and HTT-KO cell lines, we propose that early transcriptional deregulation in HD is largely caused by loss of HTT function.
Project description:Understanding the normal function of the Huntingtin (HTT) protein is of significance in the design and implementation of therapeutic strategies for Huntington’s disease (HD). Expansion of the CAG repeat in the HTT gene, encoding an expanded polyglutamine (polyQ) repeat within the HTT protein, causes HD and may compromise HTT’s normal activity contributing to HD pathology. Here, we investigated the previously defined role of HTT in autophagy specifically through studying HTT’s association with ubiquitin. We find that HTT interacts directly with ubiquitin in vitro. Tandem affinity purification was used to identify ubiquitinated and ubiquitin-associated proteins that co-purify with a HTT N-terminal fragment under basal conditions. Co-purification is enhanced by HTT polyQ expansion and reduced by mimicking HTT serine 421 phosphorylation. The identified HTT-interacting proteins include RNA-binding proteins (RBPs) involved in mRNA translation, proteins enriched in stress granules, the nuclear proteome, the defective ribosomal products (DRiPs) proteome and the brain-derived autophagosomal proteome. To determine whether the proteins interacting with HTT are autophagic targets, HTT knockout (KO) cells and immunoprecipitation of lysosomes were used to investigate autophagy in the absence of HTT. HTT KO was associated with reduced abundance of mitochondrial proteins in the lysosome, indicating a potential compromise in basal mitophagy, and increased lysosomal abundance of RBPs which may result from compensatory upregulation of starvation-induced macroautophagy. We suggest HTT is critical for appropriate basal clearance of mitochondrial proteins and RBPs, hence reduced HTT proteostatic function with mutation may contribute to the neuropathology of HD.
Project description:Huntington’s disease (HD) is a hereditary neurodegenerative disorder caused by abnormal expansion of cytosine-adenine-guanine (CAG) trinucleotide repeats in the huntingtin gene (HTT). The resultant mutant protein is ubiquitously expressed and drives pathogenesis of HD through a toxic gain-of-function mechanism. Animal models of HD have demonstrated that reducing huntingtin protein (HTT) levels alleviates HD-associated motor and neuropathological abnormalities, confirming the importance of huntingtin-lowering as a therapeutic approach. Several therapies in development repress HTT transcription or translation, including antisense oligonucleotides, virally-delivered microRNAs, and zinc finger protein transcription factors. However, they all require invasive procedures to reach the central nervous system (CNS) and do not distribute evenly to target areas in the brain. Systemically distributed therapeutics are needed to address the CNS and peripheral dysfunctions associated with HD. Here we report the discovery of small molecule splicing modifiers that lower HTT expression by selective modulation of pre-mRNA splicing. These compounds promote the inclusion of a pseudoexon containing a premature termination codon triggering HTT mRNA degradation and a reduction of HTT protein levels in vitro and in vivo. These orally bioavailable small molecules represent a non-invasive treatment option for HD and our findings support their continued development for the treatment of HD.
Project description:Huntington’s disease (HD) is a hereditary neurodegenerative disorder caused by abnormal expansion of cytosine-adenine-guanine (CAG) trinucleotide repeats in the huntingtin gene (HTT). The resultant mutant protein is ubiquitously expressed and drives pathogenesis of HD through a toxic gain-of-function mechanism. Animal models of HD have demonstrated that reducing huntingtin protein (HTT) levels alleviates HD-associated motor and neuropathological abnormalities, confirming the importance of huntingtin-lowering as a therapeutic approach. Several therapies in development repress HTT transcription or translation, including antisense oligonucleotides, virally-delivered microRNAs, and zinc finger protein transcription factors. However, they all require invasive procedures to reach the central nervous system (CNS) and do not distribute evenly to target areas in the brain. Systemically distributed therapeutics are needed to address the CNS and peripheral dysfunctions associated with HD. Here we report the discovery of small molecule splicing modifiers that lower HTT expression by selective modulation of pre-mRNA splicing. These compounds promote the inclusion of a pseudoexon containing a premature termination codon triggering HTT mRNA degradation and a reduction of HTT protein levels in vitro and in vivo. These orally bioavailable small molecules represent a non-invasive treatment option for HD and our findings support their continued development for the treatment of HD.
Project description:The Norway rat has important impacts on our life. They are amongst the most used research subjects, resulting in ground-breaking advances. At the same time, wild rats live in close association with us, leading to various adverse interactions. In face of this relevance, it is surprising how little is known about their natural behaviour. While recent laboratory studies revealed their complex social skills, little is known about their social behaviour in the wild. An integration of these different scientific approaches is crucial to understand their social life, which will enable us to design more valid research paradigms, develop more effective management strategies, and to provide better welfare standards. Hence, I first summarise the literature on their natural social behaviour. Second, I provide an overview of recent developments concerning their social cognition. Third, I illustrate why an integration of these areas would be beneficial to optimise our interactions with them.
Project description:BackgroundMurine kobuviruses (MuKV) are newly recognized picornaviruses first detected in murine rodents in the USA in 2011. Little information on MuKV epidemiology in murine rodents is available. Therefore, we conducted a survey of the prevalence and genomic characteristics of rat kobuvirus in Guangdong, China.ResultsFecal samples from 223 rats (Rattus norvegicus) were collected from Guangdong and kobuviruses were detected in 12.6% (28) of samples. Phylogenetic analysis based on partial 3D and complete VP1 sequence regions showed that rat kobuvirus obtained in this study were genetically closely related to those of rat/mouse kobuvirus reported in other geographical areas. Two near full-length rat kobuvirus genomes (MM33, GZ85) were acquired and phylogenetic analysis of these revealed that they shared very high nucleotide/amino acids identity with one another (95.4%/99.4%) and a sewage-derived sequence (86.9%/93.5% and 87.5%/93.7%, respectively). Comparison with original Aichivirus A strains, such human kobuvirus, revealed amino acid identity values of approximately 80%.ConclusionOur findings indicate that rat kobuvirus have distinctive genetic characteristics from other Aichivirus A viruses. Additionally, rat kobuvirus may spread via sewage.
Project description:Huntington’s Disease (HD) is an autosomal dominant neurodegenerative disorder caused by a trinucleotide repeat in exon 1 of the Huntingtin (HTT) gene. We used dCas9 epigenetic editing to downregulate HTT as a therapeutic approach for HD. A screen of multiple dCas9 variants fused to KRAB and DNMT3A/L with increasingly expanded PAM targeting was conducted to assess the ability to downregulate total HTT. Surprisingly, only spdCas9 could significantly downregulate HTT, while expanded PAM site variants dxCas9 and dCas9-VQR were less efficient in reducing HTT expression due to decreased binding efficiency of dCas9 variants. We further investigated DNA methylation changes through reduced representation bisulfite sequencing, showing high on-target increases in DNA methylation and few off-targets. In addition, we demonstrate mitotically stable HTT silencing of up to 6 weeks in vitro in a rapidly dividing cell line. Finally, we showed significant downregulation of HTT in patient-derived neuronal stem cells, showing the applicability in a disease-relevant system. This approach holds great promise for those suffering from disorders caused by gain of function mutations like HD.