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

项目摘要/摘要 C9orf72基因扩增的GGGGCC六核苷酸重复序列是最近发现的最多的 额颞部痴呆(FTD)和肌萎缩侧索硬化症(ALS)的常见遗传原因 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C9orf72蛋白功能的丧失和从双向转录的正义或 通过将RNA结合蛋白隔离到RNA焦点或通过 至少5种不同的异常二肽重复(DPR)蛋白[GA、GP、GR、PR和PA]的生产 内含子序列通过一种非传统的翻译机制，称为重复相关的非8月- 依赖(RAN)转换。多项研究表明，C9orf72重复序列包含 RNAs在疾病的发病机制中起着核心作用。目前尚不清楚哪些特定的细胞类型在中央 神经系统从毒性的获得上负责疾病的发病机制。C9ORF72功能丧失 单独使用不足以在小鼠中引起FTD/ALS，但我们的初步数据显示，它会加剧疾病 再加上毒性的增加。C9ORF72在C9orf72缺失小鼠发育过程中在免疫细胞中发挥重要作用 脾肿大，颈部淋巴结肿大。然而，C9orf72在小胶质细胞中的作用及其机制 对FTD/ALS的贡献尚未确定。在这项提案中，将确定1)由 用全基因组RNA测序研究C9ORF72在小胶质细胞中的功能丧失以及这种变化是否在 小胶质细胞将导致神经元毒性(目标1)；2)小胶质细胞C9orf72功能丧失是否有助于 FTD/ALS的发病机制是由于含有重复序列的RNAs对小鼠产生毒性(目标2)； 含有RNA的C9orf72重复序列的细胞类型特异性毒性(目标3)。如果成功，拟议的研究将 进一步了解C9orf72重复扩增在FTD和ALS中的发病机制 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.