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

标题：脆性X相关震颤/共济失调综合征的CGG重复相关翻译。 摘要： 显性遗传性核苷酸重复序列扩张性疾病被认为会导致一种 有两种方式：1)重复的AS RNA可以与特定的蛋白质结合并隔离，防止它们被 执行它们的正常功能；或2)如果重复被翻译成蛋白质，重复的氨基酸 膨胀可通过多种机制引发毒性，包括蛋白质的错误折叠和聚集。 传统上，每种致病机制的主要贡献都是由重复的 位于疾病基因内，外显子重复序列主要以蛋白质和非外显子形式发挥毒性 重复序列可能通过RNA介导的机制起作用。然而，最近的数据表明，这种情况在 转录本的非编码区可以通过重复相关的非编码区异常地翻译成蛋白质 8月启动(运行)翻译。根据这一新发现，定义了RNA-和 在每个重复扩增障碍中，蛋白质介导的毒性过程已经成为该领域的一个关键问题。 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，其结果是 从脆性X基因FMR1开始的CGG重复扩增。它的病理特征是 通过在病人的大脑中形成蛋白质包涵体。到目前为止的研究表明，这种重复是 与RNA一样有毒，但我们的团队最近发现CGG重复序列的扩张也会引起RAN翻译 (“CGG RAN翻译”)以产生一种易于聚集的、均聚的含有聚甘氨酸的蛋白质。这 蛋白质在模型系统中聚集，并存在于FXTAS病脑中的包裹体中。在这项提案中，我们 将决定FXTAS中的CGG重复是作为RNA还是作为有毒蛋白质引发神经退行性变，或者 两者，然后询问这个新发现的RAN翻译是如何机械地发生的。致信地址 这些问题，我们将利用FXTAS的新苍蝇模型来确定CGG重复序列的相对能力 RNA和AS RAN翻译的蛋白质可引起神经变性。然后，我们将把这些发现扩展到 两种FXTA敲入小鼠模型的病理学和行为学评价 支持CGG RAN翻译。同时，我们将采用一系列生化和基于细胞的方法来 探索CGG RAN翻译背后的机制。这些研究应该为以下方面提供重要的见解 FXTAS的发病机制，同时为其他重复扩张性疾病提供了相关的病例研究，并在 基于对疾病更好的理解，促进识别近端治疗靶点的过程 机械装置。

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.