Pathogenic Mechanism of Spinocerebellar Ataxia Type 10

描述（由申请人提供）：脊髓小脑性共济失调10型（SCA10）是一种常染色体显性遗传病，以共济失调、癫痫和预期为特征。编码E46L蛋白的SCA10基因的内含子9中ATTCT重复的大量扩增是导致这种疾病的突变。扩增突变导致疾病表型的机制尚不清楚。本课题的目的是阐明SCA10的致病机制。长期目标是基于致病机制开发合理的治疗SCA10的方法。核心假设是，SCA10的主要致病机制是由于E46L RNA中大量扩增的AUUCU重复序列破坏了多primidine tract binding protein （ppts）的正常细胞功能。这个假设是基于初步数据,(我)SCA10细胞不会显示改变E46L信使rna和蛋白质的水平,(2)损失函数的E46L蛋白质不会导致SCA10-like小鼠的表型,(iii),扩大ATTCT重复是积累在核转录和焦点,和(iv) 3种肺结核(PTB, nPTB和hnRNP K)绑定到AUUCU重复体外和至少1 (hnRNP K)硝唑核病灶细胞来自一个SCA10病人。以下2个具体目标将用于检验我们的假设。特异性目的1是证明具有扩展AUUCU重复序列的转录物通过结合和干扰SCA10细胞中PTBs的功能而获得毒性功能。预计(a)在SCA10细胞中存在可检测水平的扩展AUUCU重复序列，(b) SCA10细胞中扩展的AUUCU重复序列与ptb结合并改变ptb的细胞功能。特异性目的2是建立小鼠SCA10基因模型。目的2将通过(a)在表达扩增AUUCU重复序列的转基因小鼠中鉴定SCA10样表型，以及(b)建立缺乏编码hnRNP K的Hnrpk基因和编码脑特异性nPTB的Ptbp2基因的SCA10遗传小鼠模型来实现。表达扩增的AUUCU重复序列的转基因小鼠有望通过缺乏这些ptb而通过rna介导的功能获得，表现出sca10样表型。阐明SCA10的发病机制是一项创新，因为SCA10是已知的唯一由五核苷酸重复扩增引起的人类疾病。在SCA10中建立机制将填补目前的知识空白，促进合理治疗的发展。

DESCRIPTION (provided by applicant): Spinocerebellar ataxia type 10 (SCA10) is an autosomal dominant disorder characterized by ataxia, epilepsy and anticipation. A large expansion of the ATTCT repeat in intron 9 of the SCA10 gene encoding the E46L protein is the mutation responsible for this disease. The mechanism by which the expansion mutation leads to the disease phenotype is unknown. The goal of this project is to elucidate the pathogenic mechanism of SCA10. The long-term goal is to develop a rational therapy for SCA10 based on the pathogenic mechanism. The central hypothesis is that the major pathogenic mechanism of SCA10 is due to the disruption of the normal cellular function of polyprimidine tract binding proteins (PTBs) by the large expanded AUUCU repeat in the E46L RNA. This hypothesis is based on preliminary data that (i) SCA10 cells do not show altered levels of E46L mRNA and protein, (ii) loss of function of the E46L protein does not lead to a SCA10-like phenotype in mice, (iii), expanded ATTCT repeats are transcribed and accumulated in nuclear foci, and (iv) 3 species of PTBs (PTB, nPTB and hnRNP K) bind to AUUCU repeats in vitro and at least 1 (hnRNP K) co-localizes in the nuclear foci in cells derived from an SCA10 patient. The following 2 Specific Aims will be used to test our hypothesis. Specific Aim 1 is to demonstrate that the transcript with an expanded AUUCU repeat gains toxic functions by binding and perturbing the function of PTBs in SCA10 cells. It is expected that (a) there is a detectable level of the expanded AUUCU repeat in SCA10 cells, and (b) expanded AUUCU repeats in SCA10 cells bind to PTBs and alter the cellular functions of PTBs. Specific Aim 2 is to establish genetic mouse models of SCA10. Aim 2 will be accomplished by (a) identifying the SCA10-like phenotype in the transgenic mice that express expanded AUUCU repeats, and (b) establishing genetic mouse models of SCA10 that lack the Hnrpk gene encoding hnRNP K and the Ptbp2 gene encoding the brain-specific nPTB. Transgenic mice expressing expanded AUUCU repeats are expected to exhibit an SCA10-like phenotype by the RNA-mediated gain of function through deficiency of these PTBs. Elucidating the disease mechanism of SCA10 is innovative because SCA10 is the only human disease known to be caused by an expansion of a pentanucleotide repeat. Establishing the mechanism in SCA10 will fill the current gap of knowledge and facilitate the development of rational therapy.