Department of Neuroscience, Mayo Clinic College of Medicine, 4500 San Pablo Rd, Jacksonville, FL, 32224, USA.
Neurobiology of Disease Graduate Program, Mayo Clinic Graduate School of Biomedical Sciences, 4500 San Pablo Rd, Jacksonville, Florida, 32224, USA.
Mol Neurodegener. 2019 Feb 15;14(1):9. doi: 10.1186/s13024-019-0310-z.
A GC hexanucleotide repeat expansion in the noncoding region of C9orf72 is the major genetic cause of frontotemporal dementia and amyotrophic lateral sclerosis (c9FTD/ALS). Putative disease mechanisms underlying c9FTD/ALS include toxicity from sense GC and antisense GC repeat-containing RNA, and from dipeptide repeat (DPR) proteins unconventionally translated from these RNA products.
Intracerebroventricular injections with adeno-associated virus (AAV) encoding 2 or 149 GC repeats were performed on postnatal day 0, followed by assessment of behavioral and neuropathological phenotypes.
Relative to control mice, gliosis and neurodegeneration accompanied by cognitive and motor deficits were observed in (GC) mice by 6 months of age. Recapitulating key pathological hallmarks, we also demonstrate that sense and antisense RNA foci, inclusions of poly(GA), poly(GP), poly(GR), poly(PR), and poly(PA) DPR proteins, and inclusions of endogenous phosphorylated TDP-43 (pTDP-43) developed in (GC) mice but not control (GC) mice. Notably, proteins that play a role in the regulation of stress granules - RNA-protein assemblies that form in response to translational inhibition and that have been implicated in c9FTD/ALS pathogenesis - were mislocalized in (GC) mice as early as 3 months of age. Specifically, we observed the abnormal deposition of stress granule components within inclusions immunopositive for poly(GR) and pTDP-43, as well as evidence of nucleocytoplasmic transport defects.
Our in vivo model of c9FTD/ALS is the first to robustly recapitulate hallmark features derived from both sense and antisense C9orf72 repeat-associated transcripts complete with neurodegeneration and behavioral impairments. More importantly, the early appearance of persistent pathological stress granules prior to significant pTDP-43 deposition implicates an aberrant stress granule response as a key disease mechanism driving TDP-43 proteinopathy in c9FTD/ALS.
C9orf72 非编码区的 GC 六核苷酸重复扩增是额颞叶痴呆和肌萎缩侧索硬化症（c9FTD/ALS）的主要遗传原因。c9FTD/ALS 的潜在疾病机制包括来自 sense GC 和 antisense GC 重复 RNA 的毒性，以及这些 RNA 产物非常规翻译产生的二肽重复（DPR）蛋白的毒性。
在出生后第 0 天，通过腺相关病毒（AAV）进行脑室内注射，编码 2 或 149 个 GC 重复，然后评估行为和神经病理学表型。
与对照小鼠相比，（GC）小鼠在 6 个月时出现神经胶质增生和神经退行性变，伴有认知和运动功能障碍。我们还证实，（GC）小鼠中出现了 sense 和 antisense RNA 焦点、多（GA）、多（GP）、多（GR）、多（PR）和多（PA）DPR 蛋白包涵体、以及内源性磷酸化 TDP-43（pTDP-43）包涵体，这些包涵体是关键的病理标志，这些标志与 c9FTD/ALS 的发病机制有关，但在对照（GC）小鼠中没有发现这些包涵体。值得注意的是，在（GC）小鼠中，早在 3 个月大时，就有参与应激颗粒调节的蛋白质发生了错误定位，应激颗粒是一种在翻译抑制时形成的 RNA-蛋白复合物，与 c9FTD/ALS 的发病机制有关。具体来说，我们观察到在多（GR）和 pTDP-43 免疫阳性包涵体中，应激颗粒成分的异常沉积，以及核质转运缺陷的证据。
我们的 c9FTD/ALS 体内模型是第一个强有力地重现源自 sense 和 antisense C9orf72 重复相关转录物的标志性特征的模型，包括神经退行性变和行为损伤。更重要的是，在显著的 pTDP-43 沉积之前，持续存在的病理性应激颗粒的早期出现表明，异常的应激颗粒反应是导致 c9FTD/ALS 中 TDP-43 蛋白病的关键疾病机制。
