Hexanucleotide repeat translation in ALS and Frontotemporal Dementia

肌萎缩侧索硬化症（ALS）和额颞叶痴呆（FTD）是常见的神经退行性疾病， 进行性、致死性和无有效治疗的疾病。最近，最常见的 ALS和FTD的原因被确定为基因中的内含子GGGGCC六核苷酸重复扩增 C9orf72（C9FTD/ALS）。这种重复通过一种称为重复的过程触发有毒蛋白质的合成 相关非AUG（RAN）翻译。这些RAN肽杀死神经元，并足以引起 模型系统中的神经变性。我们对C9处的RAN翻译如何重复（C9 事实上，确实发生了。该提案的目的是确定C9 RAN的基础机制， 以确定阻断它的方法，作为开发新治疗方法的第一步。我们的核心假设 C9 RAN利用可被选择性阻断的非经典翻译起始途径。 此外，我们预测阻止C9 RAN将阻止GGGGCC重复引起的神经变性。到 为了验证这些假设，我们开发了C9 RANT的体外和基于细胞的稳健定量测定， 以及来自患者诱导的多能干细胞、啮齿动物神经元和 果蝇使用这些工具，我们将定义经历C9 RANT的mRNA种类，确定关键的 基于RNA和蛋白质的因子，允许C9 RANT，并测试是否通过调节 周围的序列或蛋白质因子可以阻断模型系统中的毒性。这些研究一起 应该为我们提供C9 RAN如何发生以及可以采取哪些步骤来防止它的工作图。这 该项目具有广泛的深远影响，既为我们了解如何RAN翻译有助于 疾病，并为C9 FTD/ALS和其他疾病的治疗开发提供了合理的途径。 神经退行性核苷酸重复序列疾病

Amyotrophic Lateral Sclerosis (ALS) and Frontotemporal dementia (FTD) are common neurodegenerative disorders that are progressive, fatal, and without effective treatment. Recently, the most common known cause of ALS and FTD was identified as an intronic GGGGCC hexanucleotide repeat expansion in the gene C9orf72 (C9FTD/ALS). This repeat triggers synthesis of toxic proteins via a process known as Repeat Associated Non-AUG (RAN) Translation. These RAN peptides kill neurons and are sufficient to cause neurodegeneration in model systems. We know very little about how RAN translation at C9 repeats (C9 RANT) actually occurs. The objective of this proposal is to determine the mechanisms underlying C9 RAN and to identify methods of blocking it as a first step towards novel therapeutic development. Our central hypothesis is that C9 RAN utilizes a non-canonical translational initiation pathway that can be selectively blocked. Moreover, we predict that preventing C9 RAN will stop neurodegeneration elicited by GGGGCC repeats. To test these hypotheses, we developed robust and quantitative in vitro and cell based assays of C9 RANT, as well as a collection of models derived from patient induced pluripotent stem cells, rodent neurons, and Drosophila. Using these tools, we will define the mRNA species that undergo C9 RANT, identify the critical RNA and protein based factors that allow for C9 RANT and test whether suppressing C9 RANT by modulating the surrounding sequence or protein factors can block toxicity in model systems. Together, these studies should provide us with a working map of how C9 RAN occurs and what steps can be taken to prevent it. This project has broad reaching implications both for our understanding of how RAN translation contributes to disease as well as providing a logical path towards therapeutic development in C9FTD/ALS and other neurodegenerative nucleotide repeat disorders.