Development of a Knock-in Mouse Model for Spinocerebellar Ataxia Type 3

描述（由申请人提供）：本R03提案旨在开发聚谷氨酰胺（polyQ）神经退行性疾病脊髓小脑性共济失调3型（SCA3）的首个敲入小鼠模型。SCA3是美国和世界许多地区最常见的显性遗传性共济失调，是由多聚谷氨酰胺编码CAG重复扩增引起的第二常见神经退行性疾病。在SCA3中，这种扩展编码了疾病蛋白中异常长的氨基酸谷氨酰胺，即去泛素化酶（DUB） ataxin-3。值得注意的是，虽然对SCA3的发病机制已经了解了很多，但还没有人开发出SCA3的敲入小鼠模型。在其他多聚谷氨酰胺疾病中，敲入模型已经导致对疾病机制的基本见解，并已开始确定针对特定多聚谷氨酰胺疾病的潜在药物治疗。目前的研究将建立在我们最近成功的人类CAG重复扩增到小鼠Atxn3位点的基础上，导致小鼠表达polyq扩增（致病性）ataxin-3。总的假设是，由此产生的Atxn3 （Q82）敲入小鼠将成功地模拟SCA3的分子特征，并阐明疾病机制。我们的主要目标是充分发展和表征这一模型，以便它可以尽快提供给更广泛的研究界，尽管我们也期望发现有助于更好地了解这种多谷氨酰胺疾病的疾病机制。这项为期两年的R03提案只有一个目标：完成SCA3敲入小鼠模型的开发和表征。我们将对SCA3敲入小鼠进行一系列行为学、免疫组织化学、分子和神经病理学分析。这些研究将辅以创新的分析方法，利用我们实验室在ataxin-3和泛素生物化学、聚谷氨酰胺特异性方法和电生理学方面的专业知识。影响：目前还没有针对SCA3的治疗方法，这是一种毁灭性的致命疾病，基本的疾病机制仍然知之甚少。作为最常见的显性遗传性共济失调和第二常见的多聚谷氨酰胺疾病，SCA3在没有敲入模型方面落后于其他多聚q疾病。本文所描述的敲入模型将为研究人员提供第一个基因精确的SCA3模型，这将极大地促进分子机制和潜在治疗策略的研究。我们实验室在广泛的技术方面的专业知识，以及我们对SCA3疾病蛋白ataxin-3新认识的特性的了解，也使我们处于一个很好的位置，可以挖掘这个新的模型，为SCA3疾病的发病机制提供重要线索。

DESCRIPTION (provided by applicant): This R03 proposal seeks to develop and the first knock-in mouse model of the polyglutamine (polyQ) neurodegenerative disease, Spinocerebellar Ataxia type 3 (SCA3). SCA3 is the most common dominantly inherited ataxia in the United States and many regions of the world, and is the second most common neurodegenerative disease caused by a polyglutamine-encoding CAG repeat expansion. In SCA3 this expansion encodes an abnormally long stretch of the amino acid glutamine in the disease protein, the de- ubiquitinating enzyme (DUB) ataxin-3. Remarkably, while much has been learned about SCA3 pathogenesis, no one has yet developed a knock-in mouse model of SCA3. In other polyglutamine diseases, knock-in models have led to fundamental insights into disease mechanisms and have begun to identify potential drug therapies for specific polyglutamine diseases. The current studies will build on our recent success targeting a human CAG repeat expansion into the murine Atxn3 locus, resulting in mice that express polyQ-expanded (pathogenic) ataxin-3. The overall hypothesis is that the resultant Atxn3 (Q82) knock-in mouse will successfully model molecular features of SCA3 and shed light on disease mechanisms. Our primary goal is to fully develop and characterize this model so that it can be made available as quickly as possible to the broader research community, though we also anticipate making discoveries that contribute to a better understanding of disease mechanisms in this polyglutamine disease. This two year R03 proposal has a single aim: to complete the development and characterization of a knock-in mouse model of SCA3. A series of behavioral, immunohistochemical, molecular and neuropathological analyses will be performed in SCA3 knock-in mice. These studies will be complemented by innovative methods of analysis that take advantage of our lab's expertise in ataxin-3 and ubiquitin biochemistry, polyglutamine-specific methods, and electrophysiology. Impact: No therapies exist for SCA3, a devastating and fatal disease, and the basic disease mechanism remains poorly understood. As the most common dominantly inherited ataxia and the second most common polyglutamine disease, SCA3 lags behind other polyQ diseases in not having a knock-in model. The knock-in model characterized here will provide researchers with the first genetically precise SCA3 model, which will greatly facilitate the study of molecular mechanisms and potential therapeutic strategies. Our laboratory's expertise in the wide range of techniques employed to characterize this line, together with our knowledge of newly recognized properties of the SCA3 disease protein, ataxin-3, also place us in an excellent position to mine this novel model for significant clues to SCA3 disease pathogenesis. PUBLIC HEALTH RELEVANCE: The studies proposed here will generate and characterize the first knock-in mouse model of the polyglutamine (polyQ) neurodegenerative disease, Spinocerebellar ataxia (SCA3). They will provide researchers with a genetically and physiologically precise SCA3 model in which to investigate disease mechanisms and test therapeutic strategies.