Fragile X-associated Tremor/Ataxia Syndrome

描述（由申请人提供）： 拟议研究的主要目的是确定进行性神经系统疾病脆性X相关震颤/共济失调综合征（FXTAS）的机制基础，该综合征涉及意向性震颤、步态共济失调和痴呆，并影响至少1/3的50岁以上男性，这些男性携带脆性X智力低下1（FMR 1）基因的小（前突变，CGGrepeat）扩增。FXTAS的神经病理学标志是核内神经元和星形胶质细胞包涵体的存在，在迄今为止检查的患有神经退行性疾病的所有个体的大脑中发现。包涵体是泛素阳性的，并且具有与多聚谷氨酰胺（GAG重复）疾病一起发现的形状和大小范围。然而，没有已知的蛋白质异常与前突变等位基因携带者相关。在具有完全突变等位基因（> 200个重复）的男性中明显不存在这种疾病，其FMR 1基因通常是沉默的，再加上前突变携带者中FMR 1 mRNA的水平显著升高，导致了该提议的中心假设，即神经系统疾病是FMR 1 mRNA的“毒性”功能获得的结果。 该项目的前两个目标是鉴定纯化的包涵体群体中所含的蛋白质和RNA种类。这些目标将通过结合最先进的质谱分析蛋白质/肽的身份，并详细探测RNA物种，现在已知存在的夹杂物。本项目的第三个目标是确定前两个目标下鉴定的蛋白质/RNA种类的潜在功能意义。目标4是拟议研究的一个主要组成部分，将进一步确定导致包涵体形成和FXTAS的分子失调的性质，使用来自正常个体和前突变携带者的原代培养星形胶质细胞（已经在实验室中建立）。该神经细胞系统将用于定义导致包涵体形成的因素和事件的时间顺序。 与FXTAS相关的核内包涵体的几个特征与帕金森病和路易体痴呆中发现的细胞质包涵体以及多系统萎缩中发现的胶质细胞质包涵体共有。因此，FXTAS作为一种单基因疾病，了解导致包涵体形成的机制，应有助于更广泛地了解导致其他神经退行性疾病中包涵体形成的事件。

DESCRIPTION (provided by applicant): The principal objective of the proposed research is the identification of the mechanistic basis for a progressive neurological disorder, fragile X-associated tremor/ataxia syndrome (FXTAS), which involves intention tremor, gait ataxia, and dementia, and affects at least 1/3 of males over 50 years of age who carry small (premutation, CGGrepeat) expansions of the fragile X mental retardation 1 (FMR1) gene. The neuropathological hallmark of FXTAS is the presence of intranuclear neuronal and astrocytic inclusions, found in the brains of all individuals examined to date who had suffered from the neurodegenerative disorder. The inclusions are ubiquitin-positive, and possess the shape and range of sizes found with the polyglutamine (GAG repeat) disorders. However, there is no known protein abnormality associated with carriers of premutation alleles. The apparent absence of this disorder among males with full mutation alleles (> 200 repeats), whose FMR1 gene is generally silenced, coupled with substantially elevated levels of FMR1 mRNA among the premutation carriers, has led to the central hypothesis of this proposal, namely, that the neurological disorder is the consequence of a "toxic" gain-of-function of the FMR1 mRNA. The first 2 aims of this project are to identify the proteins and RNA species that are contained within purified populations of inclusions. These aims will be met through a combination of state-of-the-art mass spectroscopic analysis of protein/peptide identities, and detailed probing of RNA species now known to exist within the inclusions. The third aim of this project will be to determine the potential functional significance of the proteins/RNA species identified under the first 2 aims. Aim 4, a major component of the proposed research, will be to further define the nature of the molecular dysregulation that leads to both inclusion formation and FXTAS, using primary, cultured astrocytes (already established in the laboratory) from both normal individuals and premutation carriers. This neural cell system will be used to define the factors and temporal sequence of events leading to inclusion formation. Several features of the intranuclear inclusions associated with FXTAS are shared with the cytoplasmic inclusions found in Parkinson's disease and the Lewy body dementias, and the glial cytoplasmic inclusions found in multiple system atrophy. Thus, knowledge of the mechanisms leading to the inclusions in FXTAS, as a single-gene disorder, should lead to a broader understanding of the events leading to inclusion formation in other neurodegenerative disorders.