Microglial Lysosomal Dysfunction Following Head Trauma Contributes to Tau Pathology in Chronic Traumatic Encephalopathy

翻译后摘要：每年有超过2亿人处于慢性创伤性脑病（CTE）的风险。 CTE与暴露于重复头部撞击（RHI）密切相关，例如通过以下方式接收的撞击： 接触体育和军事活动。在神经病理学上，CTE定义为： 过度磷酸化的tau（p-tau），其通过小胶质细胞神经炎症而增强。RHI暴露可诱导 小胶质细胞炎症甚至在tau病理学发作之前，但是连接RHI的机制， 炎症和CTE中的tau蛋白是未知的，这代表了一个主要的知识空白。正常的溶酶体功能 小神经胶质细胞是p-tau清除的关键机制，其在受损时有助于p-tau沉积。最近， 发现CTE中更严重的tau病理学的遗传风险因子TMEM106b影响小胶质细胞 炎症、tau病理学和CTE严重性。TMEM106 b是一种溶酶体相关蛋白， 产生更大的，酸化不良的溶酶体，指出溶酶体加工在CTE中的潜在作用 发病机制此外，来自CTE组织的初步单核RNA测序（snRNAseq）数据也 提示小胶质细胞中溶酶体功能改变。这些数据使我们假设暴露于RHI 触发持续性小胶质细胞溶酶体功能障碍，其由TMEM106b遗传风险等位基因加重， 驱动CTE中的p-tau沉积。为了解决这个假设，我们将利用snRNAseq，空间转录组学， 和多重免疫荧光来梳理RHI诱导的小胶质细胞溶酶体的遗传基础 功能障碍，并了解其作为赋予TMEM106b遗传风险的潜在机制的作用， CTE中的p-tau病理学。在目标1中，我们将评估小胶质细胞的细胞和空间分辨的基因组变化， 在CTE患者中的转录。这将揭示溶酶体功能障碍的基因组基础， RHI和允许我们将这些变化定位于p-tau沉积区域。在目标2中，我们将研究小胶质细胞 溶酶体结构和含量、溶酶体功能标志物、应激和蛋白酶表达。然后我们将 分析这些变化与TMEM106b等位基因状态、RHI暴露年数以及 CTE病理学的严重程度。以前在McKee和Cherry实验室（申办者和共同申办者）的工作， 初步数据已经验证了所提出的技术。这项工作将是第一个研究小胶质细胞溶酶体 功能障碍作为CTE病理和遗传风险的机制，这将显著促进或理解 早期疾病过程和指导未来发现新的生物标志物和治疗靶向 机制等

Abstract: More than 200 million individuals are at risk for chronic traumatic encephalopathy (CTE) each year. CTE is strongly associated with exposure to repetitive head impacts (RHI) such as those received through contact sports and military activities. Neuropathologically, CTE is defined by progressive accumulation of hyperphosphorylated tau (p-tau) which is potentiated by microglial neuroinflammation. RHI exposure can induce microglial inflammation even before the onset of tau pathology, but the mechanisms connecting RHI, inflammation, and tau in CTE are unknown, representing a major knowledge gap. Proper lysosomal function in microglia is a key mechanism of p-tau clearance that, when impaired, contributes to p-tau deposition. Recently, a genetic risk factor for more severe tau pathology in CTE, TMEM106b, was found to influence microglial inflammation, tau pathology, and CTE severity. TMEM106b is a lysosome-associated protein and the risk allele produces larger, poorly acidifying lysosomes, pointing to a potential role for lysosomal processing in CTE pathogenesis. Furthermore, preliminary single nucleus RNA sequencing (snRNAseq) data from CTE tissue also suggest an alteration to lysosomal functions in microglia. These data led us to hypothesize that exposure to RHI triggers persistent microglial lysosomal dysfunction which is exacerbated by TMEM106b genetic risk allele and drives p-tau deposition in CTE. To address this hypothesis, we will utilize snRNAseq, spatial transcriptomics, and multiplex immunofluorescence to tease apart the genetic underpinnings of RHI-induced microglial lysosomal dysfunction and understand its role as a potential mechanism conferring TMEM106b genetic risk for more severe p-tau pathology in CTE. In Aim 1 we will assess cellularly and spatially resolved genomic changes to microglial transcripts in individuals with CTE. This will reveal the genomic underpinnings of lysosomal dysfunction following RHI and allow us to localize these changes to regions of p-tau deposition. In Aim 2 we will examine microglial lysosomal structure and content, markers of lysosomal function, stress, and protease expression. We will then analyze the relationship of these changes to TMEM106b allele status, years of RHI exposure, and presence and severity of CTE pathology. Previous work in the McKee and Cherry Labs (Sponsor and co-sponsor) and preliminary data have validated the proposed techniques. This work will be the first to study microglial lysosomal dysfunction as a mechanism of CTE pathology and genetic risk which will significantly advance or understanding of an early disease process and direct future discovery of novel biomarkers and therapeutically targetable mechanisms.