iPS Cells for Investigation of HDL2 and HD Pathogenesis

亨廷顿病(HD)是一种常染色体显性遗传性神经退行性疾病，其特征是 运动、认知和情绪的异常，持续发展，直到20年后死亡 疾病发作。HD是由亨廷顿蛋白(Huntingtin，HTT)基因外显子1的CAG重复序列扩大引起的。 HD的神经生物学研究已取得实质性进展。尽管如此，截至 然而，目前还没有任何治疗方法可以阻止或显著减缓疾病的进展，而且事实证明，很难做到 在提出的100种致病机制中，优先考虑最有可能导致 治疗方面的进展。HDL2由马戈利斯小组发现并在基因上定义，是一种罕见的， 常染色体显性遗传性神经退行性疾病，临床和神经病理与HD非常相似。 与HD一样，HDL2的神经病理以皮质和纹状体神经变性为特征， 神经细胞蛋白聚集体的存在。HDL2是由染色体上的CTG/CAG扩增引起的 16q24。正常等位基因包含6-28个三联体，而致病重复序列的范围也在40-59个三联体之间 与高清非常相似。在CTG定位中，重复序列落在JPH3基因上。我们 假设HDL2突变通过丢失JPH3导致神经退行性变 含有扩展的CUG重复序列的正义链转录本的表达、毒性和表达 多聚谷氨酰胺来自反义链上的一个隐蔽基因。的相对贡献和相互作用 这些机制尚不清楚，对HDL2进行建模已被证明具有挑战性。我们现在提议 (目的1)从HDL2携带者的成纤维细胞中培养出诱导的多能细胞并对其进行鉴定。 将对细胞的多能性进行系统的研究。在目标2中，我们将区分 IPS细胞分化为神经元，包括具有纹状体表型的亚群。单元格将被描述为 用神经元和纹状体特异性标记物来确定分化模式，我们将确定 这些细胞在多大程度上概括了在HDL2脑和模型系统中观察到的结果。我们会 确定存活率、电生理特征、对谷氨酸毒性的易感性以及对 与对照组相比，脑源性神经营养因子撤除这些细胞。开发HDL2对公共卫生的影响 IPS细胞作为研究HDL2的工具有几个方面：提高了对HDL2本身的理解，新的 对与其他重复扩张性疾病相关的基本致病过程的洞察，以及 找到HD和HDL2之间的致病汇合点的机会，这将导致对 这两种疾病最有希望的治疗目标。

Huntington's disease (HD) is an autosomal dominant neurodegenerative disease, characterized by abnormalities of movement, cognition and emotion, with relentless progression until death ~20 years after disease onset. HD is caused by expanded CAG repeats in exon 1 of the Huntingtin (HTT) gene. Substantial advances have been made into understanding the neurobiology of HD. Nonetheless, as of yet no treatment exists that stops or substantially slows disease progression, and it has proven difficult to prioritize among the >100 proposed pathogenic mechanisms to focus on those most likely to lead to therapeutic advances. HDL2, discovered and genetically defined by the Margolis group, is a rare, autosomal dominant neurodegenerative disorder, clinically and neuropathologically very similar from HD. Like HD, the neuropathology of HDL2 is characterized by cortical and striatal neurodegeneration and the presence of neuronal protein aggregates. HDL2 is caused by a CTG/CAG expansion on chromosome 16q24. Normal alleles contain 6-28 triplets, while pathogenic repeats range from 40-59 triplets, again remarkably similar to HD. In the CTG orientation, the repeat falls in the gene junctophilin-3 (JPH3). We have hypothesized that the HDL2 mutation leads to neurodegeneration via a combination of loss of JPH3 expression, toxicity of the sense strand transcript containing an expanded CUG repeat, and expression of polyglutamine from a cryptic gene on the antisense strand. The relative contribution and interactions of these mechanisms remains unknown, and modeling HDL2 has proven challenging. We now propose (Aim 1) to generate and characterize induced pluripotent cells from fibroblasts of individuals with HDL2. The pluripotency of the cells will be systematically investigated. In aim 2, we will then differentiate the iPS cells into neurons, including a subpopulation with a striatal phenotype. Cells will be characterized with neuronal and striatal-specific markers to determine the differentiation pattern, and we will determine the extent to which these cells recapitulate findings observed in HDL2 brain and model systems. We will determine the survival, electrophysiological profiles, vulnerability to glutamate toxicity, and vulnerability to BDNF withdrawal of these cells compared to controls. The public health implications of developing HDL2 iPS cells as a tool for studying HDL2 are several fold: improved understanding of HDL2 itself, new insights into fundamental pathogenic processes relevant to other repeat expansion diseases, and the opportunity to find pathogenic points of convergence between HD and HDL2 that will lead to a focus on therapeutic targets of most promise for both diseases.