Pathogenic Mechanism of Spinocerebellar Ataxia Type 10

脊髓小脑型共济失调10(SCA10)是一种常染色体显性遗传性疾病，以共济失调、癫痫为特征 和期待。编码E46L的SCA10基因第9内含子ATTCT重复序列的大量扩增 蛋白质是导致这种疾病的突变。扩张突变导致的机制 对该病的表型尚不清楚。本项目的目的是阐明黄斑狼疮的发病机制。 SCA10.长期目标是根据SCA10的发病机制开发合理的治疗方法。 中心假说是SCA10的主要致病机制是由于 扩增的AUUCU重复序列对多普胺束结合蛋白(PTB)正常细胞功能的影响 在E46L RNA中。这一假设是基于以下初步数据：(1)SCA10细胞没有表现出改变 E46L的mRNA和蛋白水平，(Ii)E46L蛋白的功能丧失不会导致SCA10样蛋白 小鼠的表型，(Iii)扩增的ATTCT重复序列被转录并在核内积累，以及(Iv) 三种PTB(PTB、nPTB和hnRNP K)在体外与AUUCU重复序列结合，至少一种(HnRNP) K)共定位于来自SCA10患者的细胞的核内。以下两个具体目标将 被用来检验我们的假设。具体目标1是证明带有扩展的AUUCU的成绩单 Repeat通过结合和干扰SCA10细胞中PTB的功能而获得毒性功能。预计 (A)在SCA10细胞中存在可检测到的扩展的AUUCU重复水平，以及(B)扩展的AUUCU SCA10细胞中的重复序列与PTB结合并改变PTB的细胞功能。具体目标2是建立 SCA10基因小鼠模型的建立。目标2将通过(A)鉴定SCA10样表型在 表达扩增的AUUCU重复序列的转基因小鼠，以及(B)建立小鼠遗传模型 缺乏编码hnRNP K的Hnrpk基因和编码大脑特异性nPTB的Ptbp2基因的SCA10。 表达扩展的AUUCU重复序列的转基因小鼠有望通过以下方式表现出类似SCA10的表型 通过这些PTB的缺失，RNA介导的功能的获得。 阐明SCA10的致病机制具有创新性，因为SCA10是人类唯一的疾病 已知是由五核苷酸重复序列的扩展引起的。在SCA10中建立该机制将 填补目前的知识空白，促进理性治疗的发展。

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) three species of PTBs (PTB, nPTB and hnRNP K) bind to AUUCU repeats in vitro and at least one (hnRNP K) co-localizes in the nuclear foci in cells derived from an SCA10 patient. The following two 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.