Project description:Huntington’s disease (HD) is a dominantly inherited genetic disease caused by mutant huntingtin (htt) protein with expanded polyglutamine tracts. A neuropathological hallmark of HD is the presence of neuronal inclusions of mutant htt. p62 is an important regulatory protein in selective autophagy, a process by which aggregated proteins are degraded, and it is associated with several neurodegenerative disorders including HD. Here we investigated the effect of p62 depletion in three HD model mice: R6/2, HD190QG and HD120QG mice. We found that loss of p62 in these models led to longer lifespans and reduced nuclear inclusions, although cytoplasmic inclusions increased with polyglutamine length. In mouse embryonic fibroblasts (MEFs) with or without p62, mutant htt with a nuclear localization signal (NLS) showed no difference in nuclear inclusion between the two MEF types. In the case of mutant htt without NLS, however, p62 depletion increased cytoplasmic inclusions. Furthermore, to examine the effect of impaired autophagy in HD model mice, we crossed R6/2 mice with Atg5 conditional knockout mice. These mice also showed decreased nuclear inclusions and increased cytoplasmic inclusions, similar to HD mice lacking p62. These data suggest that the genetic ablation of p62 in HD model mice enhances cytoplasmic inclusion formation by interrupting autophagic clearance of polyQ inclusions. This reduces polyQ nuclear influx and paradoxically ameliorates disease phenotypes by decreasing toxic nuclear inclusions. Gene expression profiles were analyzed to examine the effects of p62 depletion in mouse with or without mutant huntingtin exon 1
Project description:To dissect the impact of nuclear and extranuclear mutant htt on the initiation and progression of disease, we generated a series of transgenic mouse lines in which nuclear localization (NLS) or nuclear export sequences (NES) have been placed N-terminal to the htt exon 1 protein carrying 144 glutamines. Our data indicate that the exon 1 mutant protein is present in the nucleus as part of an oligomeric or aggregation complex. Increasing the concentration of the mutant transprotein in the nucleus is sufficient for, and dramatically accelerates the onset and progression of behavioral phenotypes. Furthermore, nuclear exon 1 mutant protein is sufficient to induce cytoplasmic neurodegeneration and transcriptional dysregulation. However, our data suggests that cytoplasmic mutant exon 1 htt, if present, contributes to disease progression.<br><br>Five lines of transgenic mice and normal littermate controls were compared using Affymetrix MG-U74Av2 A arrays to examine gene expression in cerebellum. Each line had 3 or 4 replicates. Profiles were made at the first age that rotorod deficits could be detected. Some lines were also profiled at a later age when neurological impairment was more pronounced.
Project description:Huntington’s disease (HD) is a monogenetic neurodegenerative disorder caused by the expansion of a polyglutamine (polyQ) stretch in huntingtin (htt). Here we show that mutant htt reduces the transcription of insulin-like growth factor 1 (IGF-1) and leads to loss of IGF-1 in HD brains, HD mouse models and mutant htt-transgenic microglial cells. IGF-1 replacement therapy by transplantation of genetically engineered mouse neuronal precursor cells (mNPCs) in a mouse model of HD reverted the motor phenotype and countered striatal neuronal loss.
Project description:Huntington's disease (HD) is a dominantly inherited genetic disease caused by mutant huntingtin (htt) protein with expanded polyglutamine tracts. A neuropathological hallmark of HD is the presence of neuronal inclusions of mutant htt. p62 is an important regulatory protein in selective autophagy, a process by which aggregated proteins are degraded, and it is associated with several neurodegenerative disorders including HD. Here we investigated the effect of p62 depletion in three HD model mice: R6/2, HD190QG and HD120QG mice. We found that loss of p62 in these models led to longer lifespans and reduced nuclear inclusions, although cytoplasmic inclusions increased with polyglutamine length. In mouse embryonic fibroblasts (MEFs) with or without p62, mutant htt with a nuclear localization signal (NLS) showed no difference in nuclear inclusion between the two MEF types. In the case of mutant htt without NLS, however, p62 depletion increased cytoplasmic inclusions. Furthermore, to examine the effect of impaired autophagy in HD model mice, we crossed R6/2 mice with Atg5 conditional knockout mice. These mice also showed decreased nuclear inclusions and increased cytoplasmic inclusions, similar to HD mice lacking p62. These data suggest that the genetic ablation of p62 in HD model mice enhances cytoplasmic inclusion formation by interrupting autophagic clearance of polyQ inclusions. This reduces polyQ nuclear influx and paradoxically ameliorates disease phenotypes by decreasing toxic nuclear inclusions. Gene expression profiles were analyzed to examine the effects of p62 depletion in mouse with or without mutant huntingtin exon 1 To examine the effect of p62 depletion on the transcriptome of Huntington's disease model mice, we crossed p62 knockout mice with HD model mice. We extracted total RNA from the striatum of these mice at 8 weeks and used for a microaaray analysis. The samples are HD transgenic mice with p62 knockout (HD_p62KO), HD mice with normal p62 (HD_p62WT), non-HD-transgenic mice with p62 knockout (NT_p62KO), and non-HD-transgenic mice with normal p62 (NT_p62WT).
Project description:Although Huntington’s disease (HD) is a late onset neurological condition, studies suggest a developmental contribution to its adult manifestations. Imaging studies in presymptomatic HD gene carriers revealed early alterations in white matter tract with a marked defect in the corpus callosum. This tract is mainly formed by axons projecting from layer II/III neurons. HD leads to microtubule bundling defects in the growth cone, the cellular compartment that drives axonal growth. We performed a mass spectrometry-based proteomic analysis of growth cones from WT (HdhQ7/Q7) and HD (HdhQ7/Q111) mice to identify proteins involved in HD-induced phenotypes on axonal growth and on the growth cone microtubule cytoskeleton.
Project description:Emerging evidence implicates transcriptional dyseregulation within skeletal muscle in the pathogenesis of Kennedy disease/spinal bulbar muscular atrophy (KD/SBMA). We therefore broadly characterized gene expression in skeletal muscle of three independently generated mouse models of this disorder. The mouse models included a polyglutamine expanded (polyQ) AR knock-in model (AR113Q KI), a polyQ AR transgenic model (AR97Q Tg), and a transgenic mouse which overexpresses wild type AR solely in muscle (HSA-AR Tg). We performed microarray analysis of lower hindlimb muscles taken from these three models using high density oligonucleotide arrays. Changes in gene expression relative to wild type controls were evaluated separately in each strain. We validated our results using quantitative RT-PCR. Patterns of gene expression that are common to all lines and unique to each are described. When considered globally, the degree of overlap between the three models is approximately equivalent, and several patterns of gene expression relevant to the disease process were observed. Notably, patterns of gene expression typical of loss of AR function were observed in all three models, as were alterations in genes involved in cell adhesion, energy balance, Huntington’s disease, muscle atrophy and myogenesis. By comparing patterns of gene expression in three independent models of KD/SBMA, we have been able to identify candidate genes that might mediate the core myogenic features of KD/SBMA. Keywords: Gene expression in transgenic mice and disease state analysis
Project description:To dissect the impact of nuclear and extranuclear mutant htt on the initiation and progression of disease, we generated a series of transgenic mouse lines in which nuclear localization (NLS) or nuclear export sequences (NES) have been placed N-terminal to the htt exon 1 protein carrying 144 glutamines. Our data indicate that the exon 1 mutant protein is present in the nucleus as part of an oligomeric or aggregation complex. Increasing the concentration of the mutant transprotein in the nucleus is sufficient for, and dramatically accelerates the onset and progression of behavioral phenotypes. Furthermore, nuclear exon 1 mutant protein is sufficient to induce cytoplasmic neurodegeneration and transcriptional dysregulation. However, our data suggests that cytoplasmic mutant exon 1 htt, if present, contributes to disease progression. Keywords: Trangenic mouse brain gene expression
Project description:Histone deacetylase (HDAC) 4 is a transcriptional repressor that contains a glutamine rich domain. We hypothesised that it may be involved in the molecular pathogenesis of Huntington’s disease (HD), a protein folding neurodegenerative disorder caused by an aggregation-prone polyglutamine expansion and transcriptional dysregulation. We found that HDAC4 interacts with huntingtin in a polyglutamine-length dependent manner and co-localises with cytoplasmic inclusions. We show that HDAC4 reduction delayed cytoplasmic aggregate formation, restored Bdnf transcript levels and rescued neuronal and cortico-striatal synaptic function in HD mouse models. This was accompanied by an improvement in motor co-ordination, neurological phenotypes and increased lifespan. Surprisingly, HDAC4 reduction had no effect on global transcriptional dysfunction and did not modulate nuclear huntingtin aggregation. Our results define a crucial role for cytoplasmic aggregation in the molecular pathology of HD. HDAC4 reduction presents a novel strategy for targeting huntingtin aggregation which may be amenable to small molecule therapeutics.
Project description:Histone deacetylase (HDAC) 4 is a transcriptional repressor that contains a glutamine rich domain. We hypothesised that it may be involved in the molecular pathogenesis of Huntington’s disease (HD), a protein folding neurodegenerative disorder caused by an aggregation-prone polyglutamine expansion and transcriptional dysregulation. We found that HDAC4 interacts with huntingtin in a polyglutamine-length dependent manner and co-localises with cytoplasmic inclusions. We show that HDAC4 reduction delayed cytoplasmic aggregate formation, restored Bdnf transcript levels and rescued neuronal and cortico-striatal synaptic function in HD mouse models. This was accompanied by an improvement in motor co-ordination, neurological phenotypes and increased lifespan. Surprisingly, HDAC4 reduction had no effect on global transcriptional dysfunction and did not modulate nuclear huntingtin aggregation. Our results define a crucial role for cytoplasmic aggregation in the molecular pathology of HD. HDAC4 reduction presents a novel strategy for targeting huntingtin aggregation which may be amenable to small molecule therapeutics.