Project description:Mutation in the huntingtin (HTT) gene causes Huntington’s disease. Wild type Htt is essential for development as Htt knockout mice die at day E7.5. Increasing evidence suggests mutant Htt may alter neurogenesis and development of striatal neurons resulting in neuronal loss. Using mouse embryonic stem cells (mESCs), we examined the role of Htt in neural differentiation. We found Htt-null (HN) mESCs inefficient in generating neural stem cells. In contrast differentiation into progenitors of mesoderm and endoderm lineages was not affected. To investigate the basis for the lack of neural differentiation, we carried out gene expression profiling by RNA-seq to examine if genes involved in neural differentiation were dysregulated in HN mESCs.
Project description:The HTT gene mutated in Huntington’s Disease (HD) has essential roles during normal development. However, still not fully understood are the functional consequences of its partial inactivation. Our genetic study provides a comprehensive description of the effects of progressively more severe decreases in expression of Htt, the murine HTT counterpart. The most severe Htt decrease leads to lethality of early embryos, while intermediate but still severely reduced Htt dosages yield a variety of recessively inherited developmental abnormalities affecting body size, skin, skeletal and ear formation, and hematopoiesis. Comparative molecular analysis of differentiating wild-type cells and cells lacking Htt function further elucidate genes networks dysregulated during organ development. These nominate chromatin regulators and short non-coding RNAs as key molecular mediators. Together these findings demonstrate that Htt is required from conception to support normal embryonic and fetal development. Keywords: Huntingtin, Htt, Hypomorphic mice, Pleiotropy, Mouse Embryo Development, Hematopoiesis, Skeletal - Skin - Ear Development, embryonic stem cells, neuronal progenitors, RNA and miRNA sequencing, transcriptome profiling, RNA-Seq, small RNA-Seq
Project description:We used microarrays to investigate whether transcriptional dysregulation in hypothalamus is caused by expression of the huntingtin (HTT) protein We used two different Huntington's disease mouse models: BACHD mice with ubiquitous full-length mutant HTT expression (97 CAG repeats) and wild-type mice with targeted bilateral injections of wild-type or mutant HTT (853 amino acids length, wild-type HTT: 18 CAG repeats, mutant HTT: 79 CAG repeats) in hypothalamus.
Project description:Transcriptional changes are an early feature of Huntington's disease (HD). We profiled genome-wide interaction sites for the huntingtin protein (HTT) using ChIP-sequencing from mouse striatal tissue at 4 months of age. We include replicate samples from CAG-expanded murine Htt (heterozygous Q111/+) and wildtype littermate controls.
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
