Huntington's Disease Repeat Instability and Pathogenesis

描述（由申请人提供）：亨廷顿病（HD）是一种毁灭性的致命性神经退行性疾病，由HD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。尽管潜在的基因突变在15年前就被发现了，但尽管人们做出了广泛的努力来了解导致神经变性的分子途径，但仍然没有治愈或有效的治疗方法。近年来，很明显，HD CAG重复突变经历了显着的组织特异性体细胞扩增，特别是在受疾病影响的大脑区域。这提出了这样的假设，即靶组织中的体细胞HD CAG长度增加有助于HD发病机制。我们在过去的资助周期中在HD的精确遗传Hdh CAG敲入小鼠模型和HD个体的死后大脑中产生的数据强烈支持这一假设，这意味着改变体细胞不稳定性的因素也可能是疾病的修饰剂。在这里，我们提出的实验，以进一步阐明a）的因素，有助于体细胞不稳定性和HD的发病机制，和B）体细胞不稳定性的疾病表型的关系。在目标1中，我们将确定和表征的遗传变异体的差异体细胞不稳定性和差异的早期表型之间的同源Hdh CAG基因敲入小鼠品系的两个近交遗传背景。在目标2中，我们将Hdh CAG敲入小鼠与不显示体细胞不稳定性的小鼠背景（Msh 3-/-）杂交，并确定对行为表型和晚期病理学的影响。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患者中躯体不稳定性的修饰因子进行全基因组关联研究。我们还将研究来自HD患者的诱导多能干细胞（iPS）细胞的神经元的不稳定性，目的是生成不稳定的细胞培养模型，作为筛选人类不稳定修饰剂的替代方法。总之，这些研究将提供深入了解的因素，有助于体细胞不稳定性和HD的致病过程。基于攻击DNA突变本身的策略，这将为HD和其他三核苷酸重复疾病带来新的治疗靶点。 公共卫生相关性：亨廷顿氏病是一种毁灭性的、致命的神经退行性疾病，目前尚无治愈或有效的治疗方法。情感、认知和运动症状的结合，导致长期护理需求，导致极高的医疗保健成本，估计每年250亿美元。这项研究旨在确定疾病的早期修饰物，并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.