Cell-type-specific toxicity of C9orf72 repeat expansions in FTD and ALS

项目总结/摘要 C9 orf 72基因中的扩展GGGGCC六核苷酸重复序列最近被鉴定为最常见的。 额颞叶痴呆症（FTD）和肌萎缩侧索硬化症（ALS）的共同遗传原因， 具有临床、病理和遗传重叠的神经退行性疾病。提出的疾病机制 包括C9 orf 72蛋白功能的丧失和来自双向转录的有义链的毒性的获得，或 通过将RNA结合蛋白隔离到RNA灶中或通过 从来自以下的人产生至少五种不同的异常二肽重复（DPR）蛋白[GA、GP、GR、PR和PA]： 内含子序列通过一种称为重复相关非AUG- 依赖（RAN）翻译。几项研究表明，从含有C9 orf 72重复序列的细胞中获得毒性， RNA在疾病发病机制中起着核心作用。目前尚不清楚中央神经系统中哪些特定的细胞类型 神经系统负责从毒性获得的疾病发病机制。C9 orf 72功能丧失 单独使用不足以引起小鼠的FTD/ALS，但我们的初步数据显示，它会加重疾病 并伴随毒性的增加。随着C9 orf 72缺失小鼠的发育，C9 orf 72在免疫细胞中起重要作用 脾肿大和颈淋巴结肿大。然而，C9 orf 72在小胶质细胞中的功能及其 未确定对FTD/ALS的贡献。在这项提案中，将确定1）改变的分子途径， 使用全基因组RNA测序研究小胶质细胞中C9 orf 72功能的丧失，以及这种变化是否会影响 小胶质细胞中的C9 orf 72功能丧失是否有助于神经元毒性（目的1）; 2）小胶质细胞中的C9 orf 72功能丧失是否有助于神经元毒性（目的2）。 小鼠中含重复序列的RNA毒性增加引起的FTD/ALS发病机制（目的2）;和3） 来自含C9 orf 72重复的RNA的细胞类型特异性毒性（目的3）。如果成功，拟议的研究将 进一步帮助我们理解C9 orf 72重复扩增在FTD和ALS中的疾病机制， 确定潜在的治疗干预措施。

PROJECT SUMMARY/ABSTRACT Expanded GGGGCC hexanucleotide repeats in the C9orf72 gene were recently identified as the most common genetic cause of Frontotemporal Dementia (FTD) and Amyotrophic Lateral Sclerosis (ALS), two neurodegenerative disorders with clinical, pathological and genetic overlaps. Proposed disease mechanisms include loss of C9orf72 protein function and gain of toxicity from the bidirectionally transcribed sense or antisense repeat-containing RNAs, mediated by sequestration of RNA binding proteins into RNA foci or by production of at least five different aberrant dipeptide repeat (DPR) proteins [GA, GP, GR, PR, and PA] from the intronic sequence through a nonconventional translation mechanism called repeat-associated non-AUG- dependent (RAN) translation. Several studies demonstrated that gain of toxicity from C9orf72 repeat containing RNAs plays a central role in disease pathogenesis. It is yet unknown which specific cell types in the central nervous system is responsible for the disease pathogenesis from gain of toxicity. C9orf72 loss of function alone is insufficient to cause FTD/ALS in mice, but our preliminary data showed it exacerbates diseases together with gain of toxicity. C9orf72 plays an important role in the immune cells as C9orf72 null mice develop splenomegaly and enlarged cervical lymph nodes. However, the function of C9orf72 in microglia and its contribution to FTD/ALS is not determined. In this proposal, will determine 1) molecular pathways altered by C9orf72 loss of function in microglia using genome-wide RNA sequencing and whether such changes in microglia will lead to neuronal toxicity (Aim 1); 2) Whether C9orf72 loss of function in microglia contributes to FTD/ALS pathogenesis caused by gain of toxicity from the repeat containing RNAs in mice (Aim 2); and 3) cell-type-specific toxicity from C9orf72 repeat containing RNAs (Aim 3). If successful, the proposed study will further help us understand the disease mechanisms of C9orf72 repeat expansions in FTD and ALS and identify potential therapeutic interventions.