Huntington's disease repeat instability and pathogenesis

 描述（由申请人提供） 亨廷顿氏病（HD）是一种毁灭性和致命的神经退行性疾病，由HTT基因中多态性CAG重复序列的扩增引起，其触发细胞死亡，对纹状体和皮质中的神经元具有特异性。虽然潜在的基因突变在20多年前就被发现了，但尽管付出了广泛的努力，仍然没有治愈或有效的治疗方法。HTT CAG重复突变在传递给后代和体细胞方面都是高度不稳定的。值得注意的是，重复经历了显着的组织特异性体细胞扩张，特别是在受疾病影响的脑区域，强烈表明靶组织中的体细胞HTT CAG长度增加有助于HD发病机制。我们已经在精确的遗传HD基因敲入小鼠模型中表明，错配修复（MMR）途径中的基因（Msh 2、Msh 3、Mlh 1、Mlh 3）对于CAG扩增至关重要，并增强了致病过程。最近的一项全基因组关联研究表明这些发现与HD患者的相关性，其中MLH 1 SNP与运动发作相关，更普遍的是，其中DNA修复途径被强调为疾病修饰的来源。在本研究中，我们将：1）在HD基因敲入小鼠中进行遗传实验，以深入了解MMR依赖性不稳定性和发病机制; 2）测试HD患者中MLH 1 SNP对基因表达、细胞表型以及体细胞和代际重复不稳定性的影响; 3）使用基因敲除和基因编辑方法来测试额外的DNA修复基因的影响，这些基因被认为是患者的疾病修饰因子，作为HD基因敲入小鼠不稳定性和纹状体发病机制的调节剂。总之，这些实验将为MMR/DNA修复基因改变发病机制的途径和机制提供关键的见解，这将直接影响有望靶向疾病过程早期发生机制的治疗方法的发展。

 DESCRIPTION (provided by applicant) Huntington's disease (HD) is a devastating and fatal neurodegenerative disorder caused by the expansion of a polymorphic CAG repeat in the HTT gene that triggers cell death with a specificity towards neurons in the striatum and cortex. Although the underlying genetic mutation was discovered over 20 years ago, there is still no cure or effective treatment despite extensive efforts. The HTT CAG repeat mutation is highly unstable both in transmissions to subsequent generations and somatically. Notably the repeat undergoes dramatic tissue-specific somatic expansion, particularly in the brain regions affected in the disorder, strongly suggesting that somatic HTT CAG length increases in target tissues contribute to HD pathogenesis. We have shown in accurate genetic HD knock-in mouse models that genes in the mismatch repair (MMR) pathway (Msh2, Msh3, Mlh1, Mlh3) are critical for CAG expansion and enhance the pathogenic process. The relevance of these findings to HD patients is indicated by a recent genome-wide association study in which MLH1 SNPs were associated with motor onset, and more generally, in which DNA repair pathways were highlighted as a source of disease modification. In this study we will: 1) perform genetic experiments in HD knock-in mice that will provide insight into mechanism(s) of MMR-dependent instability and pathogenesis; 2) test the impact of MLH1 SNPs in HD patients on gene expression, cellular phenotypes and on somatic and intergenerational repeat instability; 3) Use gene knockdown and gene editing approaches to test the impact of additional DNA repair genes, implicated as disease modifiers in patients, as modifiers of instability and striatal pathogenesis in HD knock-in mice. Together, these experiments will provide critical insight into pathways and mechanisms by which MMR/DNA repair genes modify pathogenesis, which will directly impact on the development of therapeutics that promise to target mechanism(s) that occur very early in the disease process.