Huntington's Disease Repeat Instability and Pathogenesis

描述(申请人提供)：亨廷顿病(HD)是一种毁灭性的致命神经退行性疾病，由HD基因中一个多态CAG重复序列的扩大引起，该重复序列触发细胞死亡，并具有纹状体和皮质神经元的特异性。尽管潜在的基因突变是在15年前发现的，但尽管人们做出了广泛的努力来了解导致神经退化的分子途径，但仍然没有治愈或有效的治疗方法。近年来，很明显，HD CAG重复突变经历了戏剧性的组织特异性躯体扩张，特别是在受这种疾病影响的大脑区域。这提出了一种假设，即靶组织中体细胞HD CAG长度的增加参与了HD的发病。我们在过去的资金周期中产生的数据，无论是在HD的准确遗传HDH CAG敲入小鼠模型中，还是在HD患者的死后大脑中，我们都强烈支持这一假说，这意味着修改躯体不稳定的因素也可能是疾病的修饰者。在这里，我们建议进行实验，以进一步阐明a)躯体不稳定性和HD发病机制的因素，以及b)躯体不稳定性与疾病表型的关系。在目标1中，我们将识别和表征在两个近交遗传背景上的同源HDH CAG敲入小鼠品系之间躯体不稳定性和早期表型差异的遗传变异。在目标2中，我们将HDH CAG敲入小鼠置于没有显示出躯体不稳定的小鼠背景(Msh3-/-)上，并确定其对行为表型和后期病理的影响。在目标3中，我们将量化大量HD死后大脑中的躯体不稳定性，并对HD患者的躯体不稳定性修饰物进行全基因组关联研究。我们还将研究HD患者诱导多能干细胞(IPS)来源的神经元的不稳定性，目的是建立不稳定性的细胞培养模型，作为筛选人类不稳定性修饰物的替代方案。总之，这些研究将为深入了解导致躯体不稳定和HD致病过程的因素提供依据。这将基于攻击DNA突变本身的策略，为HD和其他三核苷酸重复疾病带来新的治疗靶点。 公共卫生意义：亨廷顿氏病是一种毁灭性的、致命的神经退行性疾病，目前还没有治愈或有效治疗的方法。情绪、认知和运动症状的结合导致了长期护理需求，导致了极高的医疗费用，估计每年高达250亿美元。这项研究的目的是确定疾病的早期修饰物，有可能发现早期治疗干预的新靶点。

DESCRIPTION (provided by applicant): Huntington's disease (HD) is a devastating fatal neurodegenerative disorder caused by the expansion of a polymorphic CAG repeat in the HD gene that triggers cell death with a specificity towards neurons in the striatum and cortex. Although the underlying genetic mutation was discovered over 15 years ago, there is still no cure or effective treatment despite extensive efforts to understand the molecular pathways that lead to neurodegeneration. In recent years it has become apparent that the HD CAG repeat mutation undergoes dramatic tissue-specific somatic expansion, particularly in the brain regions affected in the disorder. This raises the hypothesis that somatic HD CAG length increases in target tissues contribute to HD pathogenesis. Data that we have generated during the past funding cycle both in accurate genetic Hdh CAG knock-in mouse models of HD and in postmortem brain from HD individuals strongly support this hypothesis, implying that factors that modify somatic instability may also be modifiers of disease. Here we propose experiments to elucidate further a) the factors that contribute to somatic instability and HD pathogenesis, and b) the relationship of somatic instability to disease phenotypes. In Aim 1 we will identify and characterize the genetic variants that underlie the difference in somatic instability and the difference in an early phenotype between congenic Hdh CAG knock-in mouse strains on two inbred genetic backgrounds. In Aim 2 we will cross Hdh CAG knock-in mice onto a mouse background (Msh3-/-) that displays no somatic instability and determine the effect on behavioral phenotypes and late-stage pathology. In Aim 3 we will quantify somatic instability in a large collection of HD postmortem brains and perform a genome-wide association study for modifiers of somatic instability in HD patients. We will also investigate instability in neurons derived from induced pluripotent stem (iPS) cells from HD patients with the aim of generating a cell culture model of instability as an alternative to screen for modifiers of instability in humans. Together, these studies will provide insight into the factors that contribute to somatic instability and the HD pathogenic process. This will lead to novel therapeutic targets both for HD and other trinucleotide repeat diseases based upon a strategy of attacking the DNA mutation itself. PUBLIC HEALTH RELEVANCE: Huntington's disease is a devastating, fatal neurodegenerative disorder for which there is no cure or effective treatment. The combination of emotional, cognitive and motor symptoms, leading to long-term care needs results in an extremely high healthcare cost, estimated at 25 billion dollars a year. This study is aimed at identifying early modifiers of disease with the potential of discovering novel targets for early therapeutic intervention.