Repeat Associated non-AUG translation in Myotonic Dystrophy Type 1

摘要 强直性肌营养不良1型（DM 1）是成人发病型肌营养不良的主要原因， 超过40+重复扩张疾病大家族的成员。2011年，Ranum实验室 发现这些扩增突变中的许多可以表达重复蛋白质， AUG起始密码子使用称为重复相关非AUG（RAN）的新过程 翻译.在该初步研究中，证明了DM 1反义CAG扩增 转录物表达RAN蛋白，反义RAN polyGln蛋白在转录物中积累。 DM 1患者和小鼠模型的疾病相关组织。虽然最初的数据表明， RAN蛋白可能有助于DM 1，即在细胞中检测RAN蛋白的工具和技术。 时间不够敏感，无法对RAN的作用进行彻底审查 DM 1蛋白质一个重要的未回答的问题是RAN蛋白在细胞凋亡中的潜在作用。 DM 1的CNS异常，已被证明会显著影响生活质量。小说 和Ranum集团新开发的特异性RAN蛋白免疫学检测工具 显示DM 1 RAN蛋白，聚Leu（有义转录物）和聚Ser（反义转录物）， 转录物）在DM 1额叶灰质和白色物质区的神经元和神经胶质细胞中积累 皮层Ranum实验室还表明，FDA批准的2型糖尿病药物二甲双胍 在C9 orf 72 ALS/FTD小鼠中抑制RAN翻译并改善疾病表型（参考文献）， 这表明类似的方法可能在DM 1中起作用。这一提议的核心假设是， RAN翻译有助于DM 1，调节RAN翻译将减轻疾病 功能.为了检验这一假设，我们将：（1）确定RAN蛋白聚集体是否在细胞中积累， 显示神经炎症和其他类型组织病理学的DM 1脑区;（2）检查 有义和反义RAN蛋白在骨骼肌中积累，如果RAN蛋白 积累随着年龄和肌肉病理学而增加;和（3）评估DM 1 RAN蛋白是否 是有毒的，如果用二甲双胍抑制RAN翻译将改善DM 1 iPSC的表型， 衍生的肌肉和脑类器官。这些研究将有助于改善我们 了解RAN翻译在DM 1中的作用，并提供强有力的机制原理 使用二甲双胍作为DM 1患者的治疗策略。

Abstract Myotonic dystrophy type 1 (DM1) is the leading cause of adult-onset muscular dystrophy and a member of the large family of over 40+ repeat expansions diseases. In 2011, the Ranum lab discovered that many of these expansion mutations can express repetitive proteins without an AUG initiation codon using a novel process called repeat associated non-AUG (RAN) translation. In this initial study, it was demonstrated that the DM1 antisense CAG expansion transcripts express RAN proteins with the antisense RAN polyGln proteins accumulating in disease relevant tissue of DM1 patient and mouse models. While this initial data suggested that RAN proteins might contribute to DM1, the tools and techniques to detect RAN proteins at the time were not sufficiently sensitive to allow for a thorough examination of the role of RAN proteins in DM1. One important unanswered question is the potential role of RAN proteins in the CNS abnormalities of DM1, which have been shown to significantly impact quality of life. Novel and specific RAN protein immunological detection tools newly developed by the Ranum group shows that frequent the DM1 RAN proteins, polyLeu (sense transcript) and polySer, (antisense transcript) accumulate in neurons and glial cells in grey and white matter regions of DM1 frontal cortex. The Ranum lab has also shown that the FDA-approved type 2 diabetes drug metformin inhibits RAN translation and improved disease phenotypes in C9orf72 ALS/FTD mice (ref), suggesting a similar approach may work in DM1. The central hypothesis of this proposal is that RAN translation contributes to DM1 and that modulating RAN translation will mitigate disease features. To test this hypothesis, we will: (1) determine if RAN protein aggregates accumulate in DM1 brain regions that show neuroinflammation and other types of histopathology; (2) examine sense and antisense RAN proteins accumulate in skeletal muscle and if RAN protein accumulation increases with age and muscle pathology; and (3) assess if DM1 RAN proteins are toxic and if inhibiting RAN translation with metformin will improve phenotypes in DM1 iPSC- derived muscle and brain organoids. Taken together these studies will improve our understanding of the role of RAN translation in DM1 and provide strong mechanistic rationale for the use of metformin as a therapeutic strategy for DM1 patients.