Dysregulation of inhibitory synapse by poly-GR in C9ORF72-ALS/FTD

该项目的目标是了解抑制性突触的失调引起的 C9 ORF 72相关肌萎缩侧索硬化症（ALS）和额颞叶变性中的聚糖皮质激素受体 （FTD）。C9 ORF 72基因中的六核苷酸重复扩增是最常见的遗传性 ALS和FTD的病因一个潜在的致病机制是异常积累 重复相关非AUG（RAN）翻译产生的二肽重复（DPR）蛋白， 有义链和寡核苷酸链的所有六个阅读框架（poly-GA、poly-GR、poly-PA、poly-PR和poly-PG） 反义RNA。一系列证据表明，某些形式的DPR蛋白，特别是GR， 和PR，可以诱导包括应激颗粒在内的多种分子途径的失调， 功能障碍，核质转运缺陷，改变ER稳态，等。 分子缺陷对神经元功能的影响仍然研究不足。 越来越多的证据表明，突触的密度和功能发生了变化， 在神经退行性疾病中显著的神经元死亡之前。的发展 超兴奋性是众所周知的现象。一种可能的机制是， 兴奋性与抑制性活性之比（E/I失衡）。我们的初步数据确定了 减少桥蛋白聚集，桥蛋白是抑制突触形成所必需的支架蛋白， 在C9 ORF 72-ALS/FTD患者iPSC-神经元和具有聚-GR的原代神经元中的功能 表情我们现在提出表征结构和电生理功能障碍 的抑制性突触，并破译分子机制如何聚GR导致这种 通过将不同的组学技术与分子和细胞方法相结合来消除缺陷。我们 目的是使用邻近标记蛋白质组学鉴定神经元中的GR相互作用蛋白， 通过高通量测序发现GR诱导的转录组变化，这将揭示候选的 基因/通路，以进一步研究它们对GR介导的突触 失调该项目是了解分子的重要的第一步。 ALS和FTD患者的神经元功能障碍机制。分子学的见解 从这项研究将有助于了解疾病的病因和开发新的 治疗目标

The goal of the project is to understand the dysregulation of inhibitory synapse caused by poly-GR in C9ORF72-linked amyotrophic lateral sclerosis (ALS) and frontotemporal degeneration (FTD). Hexanucleotide repeat expansion in the C9ORF72 gene is the most common genetic cause of both ALS and FTD. One potential pathogenic mechanism is the aberrant accumulation of dipeptide repeat (DPR) proteins produced by repeat-associated non-AUG (RAN) translation in all six reading frames (poly-GA, poly-GR, poly-PA, poly-PR and poly-PG) of both sense and antisense RNAs. Lines of evidence indicate that some forms of the DPR proteins, particularly GR and PR, can induce dysregulation of several molecular pathways, including stress granule dysfunction, nucleocytoplasmic transport defects, altered ER homeostasis, et al. How these molecular deficits influence neuronal functions remains understudied. Accumulating evidence indicated that changes of synapse density and function occurs prior to significant neuronal death in neurodegenerative diseases. The development of hyperexcitability is a well-known phenomenon. One plausible mechanism is the alterations in the ratio of excitatory to inhibitory activity (E/I imbalance). Our preliminary data identified specific reduction of gephyrin clustering, a scaffold protein essential for inhibitory synapse formation and function, in C9ORF72-ALS/FTD patient iPSC-neurons and in primary neurons with poly-GR expression. We now propose to characterize the structure and electrophysiological dysfunction of the inhibitory synapse, and to decipher the molecular mechanism how poly-GR causes such defects by combining different –omics techniques with molecular and cellular approaches. We aim to identify GR-interacting proteins in neurons using the proximity-labeling proteomics and GR-induced transcriptomic changes by high-throughput sequencing, which will reveal candidate genes/pathways for further mechanistic study of their contribution to GR-mediated synaptic dysregulation. This project makes an important first step toward understanding the molecular mechanisms of neuronal dysfunction in ALS and FTD patients. The molecular insights resulting from this study will help understanding the etiology of the disease and developing novel therapeutic targets.