CGG repeat associated translation in Fragile X-associated Tremor/Ataxia Syndrome

标题：脆性X相关震颤/共济失调综合征中CGG重复相关翻译。 摘要： 显性遗传的核苷酸重复序列扩增障碍被认为会引起一个人的神经变性。 两种方式：1）重复作为RNA可以结合并隔离特定的蛋白质，防止它们 2）如果重复序列被翻译成蛋白质，则重复氨基酸 扩增可通过包括蛋白质错误折叠和聚集在内的多种机制引发毒性。 传统上，每种致病机制的主要贡献都是由重复序列的 在疾病基因内的位置，外显子重复主要作为蛋白质和非外显子重复发挥毒性 重复可能通过RNA介导的机制起作用。然而，最近的数据表明， 转录本的“非编码”区域可以通过重复相关非编码区异常翻译成蛋白质。 AUG启动（RAN）翻译。根据这一新发现，定义RNA和RNA的相对贡献 每种重复扩增障碍中的蛋白质介导的毒性过程已经成为该领域的关键问题。 脆性X相关震颤/共济失调综合征（FXTAS）是一种遗传性神经退行性疾病， 来自脆性X基因FMR 1开始时的CGG重复扩增。它的病理特征是 通过病人大脑中蛋白质内含物的形成。迄今为止的工作表明， 但是我们的研究小组最近发现，CGG重复序列的扩增也会导致RNA的翻译 在一个实施方案中，所述方法包括将CGG RAN翻译（“CGG RAN翻译”）以产生易于聚集的含均聚甘氨酸的蛋白质。这 蛋白质聚集在模型系统中，并存在于FXTAS疾病脑中的内含物中。在本提案中，我们 将确定FXTAS中的CGG重复序列是否作为RNA、作为毒性蛋白或 然后询问这种新发现的RAN翻译是如何机械地发生的。解决 这些问题，我们将利用FXTAS的新苍蝇模型来确定CGG重复的相对能力， RNA和RAN翻译的蛋白质引起神经变性。然后，我们将这些发现扩展到 两种FXTAS基因敲入小鼠模型的病理和行为评估， 支持CGG RAN翻译。同时，我们将采用一系列生物化学和细胞为基础的方法， 探索CGG RAN翻译的潜在机制。这些研究应该提供关键的洞察力， FXTAS发病机制，同时为其他重复扩张性疾病提供相关病例研究， 该过程有助于基于对疾病的更好理解识别近端治疗靶点 机制等

Title: CGG repeat associated translation in Fragile X-associated Tremor/Ataxia Syndrome. Abstract: Dominantly inherited nucleotide repeat expansion disorders are thought to elicit neurodegeneration in one of two ways: 1) The repeat as RNA can bind to and sequester specific proteins, preventing them from performing their normal functions; or 2) If the repeat is translated into protein, the repetitive amino acid expansion can trigger toxicity through a variety of mechanisms including protein misfolding and aggregation. Traditionally, the dominant contribution of each pathogenic mechanism has been suggested by the repeat's location within the disease gene, with exonic repeats exerting toxicity primarily as protein and non-exonic repeats presumably acting via RNA-mediated mechanisms. Recent data, however, indicate that repeats in "non-coding" regions of transcripts can be aberrantly translated into proteins through Repeat Associated Non- AUG initiated (RAN) translation. In light of this new finding, defining the relative contributions of RNA- and protein-mediated toxic processes in each repeat expansion disorder has surfaced as a critical issue in the field. Fragile X-associated Tremor/Ataxia Syndrome (FXTAS) is an inherited neurodegenerative disorder that results from a CGG repeat expansion at the beginning of the fragile X gene, FMR1. It is characterized pathologically by the formation of proteinaceous inclusions in the brains of patients. Work to date suggests that the repeat is toxic as RNA, but our group recently showed that the CGG repeat expansion also elicits RAN translation ("CGG RAN translation") to produce an aggregation-prone, homopolymeric polyglycine containing protein. This protein aggregates in model systems and is present in inclusions in FXTAS disease brain. In this proposal, we will determine whether the CGG repeat in FXTAS triggers neurodegeneration as RNA, as a toxic protein, or both, and then interrogate how this newly discovered RAN translation occurs mechanistically. To address these questions, we will utilize new fly models of FXTAS to determine the relative abilities of CGG repeats as RNA and as RAN translated proteins to elicit neurodegeneration. We will then extend these findings to pathological and behavioral assessments of two knock-in mouse models of FXTAS that differ in their ability to support CGG RAN translation. In parallel, we will employ a series of biochemical and cell-based approaches to explore the mechanisms underlying CGG RAN translation. These studies should provide critical insight into FXTAS pathogenesis while offering a relevant case-study for other repeat expansion disorders, and in the process facilitate the identification of proximal therapeutic targets based on improved understanding of disease mechanisms.