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Truncation of mutant huntingtin in knock-in mice via CRISPR-Cas9 uncovers exon1 huntingtin as a key pathogenic form

ABSTRACT: It remains unknown how polyglutamine expansion in widely expressed proteins can cause selective neurodegeneration. In Huntington’s disease (HD), proteolytic processing generates toxic N-terminal huntingtin (HTT) fragments that preferentially kill striatal neurons. Considerable efforts have been devoted to investigating how HTT is cleaved and whether blocking its cleavage is therapeutically beneficial. However, using CRISPR-Cas9 to truncate full-length mutant Htt in HD140Q knock-in (KI) mice, we found that exon1 Htt is stably present in the brain, regardless of truncation sites in full-length Htt. This N-terminal Htt led to similar HD phenotypes and age-dependent Htt accumulation in striatum in different KI mice. Exon1 Htt is constantly generated but its selective accumulation in the striatum is caused by the age-dependent expression of striatum-enriched HspBP1, a chaperone inhibitory protein. Our findings suggest that tissue-specific chaperone function accounts for the selective neuropathology in HD and highlight therapeutic importance in regulating this function.

ORGANISM(S): Mus musculus

PROVIDER: GSE145879 | GEO | 2020/04/21

REPOSITORIES: GEO

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Identification of full length wild-type and mutant huntingtin interacting proteins by crosslinking immunoprecipitation in mice brain cortex

Project description:Huntington’s Disease is a neurodegenerative disorder caused by a CAG expansion in exon1 of the huntingtin (Htt) gene. The resulting polyglutamine expansion in the ubiquitously expressed mutant Htt (mHtt) protein leads to selective neurodegeneration. In this study we set out to identify interacting proteins of full length wild-type and mHtt protein in the mice cortex brain region in order to get a better understanding of the processes involved in HD pathology.

2021-06-21 | PXD024254 | Pride

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2022-07-29 | GSE209893 | GEO

Uninterrupted Mutant Huntingtin CAG-repeat but Not Polyglutamine Length Predicts Striatal Nuclear Pathogenesis and Transcriptionopathy in HD Mice

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HTT-OMNI: A Web-based Platform for Huntingtin Interaction Exploration and Multi-omics Data Integration

Project description:We have developed a web-based platform for HTT PPI visualization, exploration, and multi-omic integration called HTT-OMNI. We demonstrate the utility of this platform not only for exploring and filtering existing huntingtin (HTT) PPIs, but also for investigating user-generated omics datasets. For example, we demonstrate the comparison of a published HTT IP-MS experiment, performed in the striatum brain region of a mouse HD model, to unpublished HTT IP-MS experiments in the cortex brain region. Overall, HTT-OMNI summarizes and integrates known HTT PPIs with polyQ-dependent transcriptome and proteome measurements, providing an all-in-one exploratory platform that facilitates the prioritization of target genes that may contribute to HD pathogenesis.

2022-08-15 | PXD034158 | Pride

PolyQ-expansion does not alter the huntingtin-HAP40 complex

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2021-03-19 | PXD018451 | Pride

PTMs of HTT protein - Post-translational modifications (PTMs), identified on endogenous huntingtin, cluster within proteolytic domains between HEAT repeats

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2017-06-29 | PXD005753 | Pride

Small molecule activation of a pseudoexon triggers huntingtin-lowering (AmpliSeq)

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.

2021-07-01 | GSE162812 | GEO

Small molecule activation of a pseudoexon triggers huntingtin-lowering (RNA-Seq)

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In vivo cell-autonomous transcriptional abnormalities revealed in mice expressing mutant huntingtin in striatal but not cortical neurons

Project description:Huntington’s disease (HD), caused by a CAG repeat expansion in the huntingtin (HTT) gene, is characterized by abnormal protein aggregates and motor and cognitive dysfunction. Htt protein is ubiquitously expressed, but the striatal medium spiny neuron (MSN) is most susceptible to neuronal dysfunction and death. Abnormal gene expression represents a core pathogenic feature of HD, but the relative roles of cell-autonomous and non-cell-autonomous effects on transcription remain unclear. To determine the extent of cell-autonomous dysregulation in the striatum in vivo, we examined genome-wide RNA expression in symptomatic D9-N171-98Q (a.k.a. DE5) transgenic mice in which the forebrain expression of the first 171 amino acids of human Htt with a 98Q repeat expansion is limited to MSNs. Microarray data generated from these mice were compared to those generated on the identical array platform from a pan-neuronal HD mouse model, R6/2, carrying two different CAG repeat lengths, and a relatively high degree of overlap of changes in gene expression was revealed. We further focused on known canonical pathways associated with excitotoxicity, oxidative stress, mitochondrial dysfunction, dopamine signaling and trophic support, among others. While genes related to excitotoxicity, dopamine signaling and trophic support, were altered in both DE5 and R6/2 transgenic mice, which may be either cell-autonomous or non-cell-autonomous,, genes related to mitochondrial dysfunction, oxidative stress and the peroxisome proliferator-activated receptor are primarily affected in DE5 transgenic mice, indicating cell autonomous mechanisms Overall, our results demonstrate that HD-induced dysregulation of the striatal transcriptome can be largely attributed to intrinsic effects of mutant Htt,,such that mutant Htt-induced effects in cortical neurons is not necessary for striatal dysfunction/degeneration. Striatum from DE5 transgenic mice vs. wt littermate controls

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Analysis of striatal zinc finger protein (ZFP) repression of mutant Huntingtin (HTT) in the zQ175DN knock-in mouse model of Huntington's disease (snRNA-seq)

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