Investigating the role of TMEM106b genetics and pathology in Alzheimer’s disease, LATE and FTLD

项目概要/摘要 来自跨膜蛋白106 B（TMEM 106 B）的纤维最近被发现代表了一种新的蛋白质。 一系列神经退行性疾病中的新病理学标志，包括TDP-43蛋白病， 共核蛋白病和tau蛋白病。值得注意的是，TMEM 106 B遗传变异与额颞叶疾病的风险有关。 伴有TDP-43包涵体的肺叶变性（FTLD-TDP），特别是伴有颗粒蛋白前体（GRN）的病例， 9号染色体开放阅读框72（C9 ORF 72）突变和边缘优势年龄相关TDP-43 脑病（LATE）神经病理改变。TMEM 106 B变异也与认知能力下降有关， 肌萎缩侧索硬化症患者。虽然在一些单核苷酸多态性（SNP）， 已确定TMEM 106 B并与疾病风险相关，只有一个（rs3173615）引入了编码变更 （p.T185S），与其他危险SNPs高度连锁不平衡。为了研究一个有趣的想法， rs3173615可以通过调节TMEM 106 B沉积来调节疾病风险，我们开发了一种 针对TMEM 106 B丝核心序列的抗体。与最近的报告一致，我们检测到 来自FTLD-TDP和LATE患者的肌氨酰不溶性部分中的TMEM 106 B阳性细丝。 值得注意的是，我们还观察到FTLD-TDP患者中不溶性TMEM 106 B的积累增加， rs3173615风险等位基因纯合（在残基185处编码苏氨酸而不是丝氨酸）。总的来说， 这些发现支持了TMEM 106 B聚集解释了遗传变异之间联系的假设， 在TMEM 106 B位点和疾病风险之间存在联系-我们怀疑它也可以解释TMEM 106 B位点和疾病风险之间的潜在联系。 rs3173615、TDP-43蛋白质病和认知能力下降。我们还推测TMEM 106 B中的差异 蓄积导致FTLD和LATE临床和病理异质性。此外，鉴于 LATE与额叶[18 F]氟脱氧葡萄糖PET（FDG-PET）的代谢降低相关 叶，一个由TMEM 106 B原纤维占据的区域，我们预测rs3173615基因型也将与TMEM 106 B原纤维相关。 神经退行性变的神经成像测量。在这个项目中，我们将调查rs3173615的影响， 基因型对TMEM 106 B聚集的影响，并评估其是否与TDP-43蛋白质病和临床 成果。我们还将探讨rs3173615编码变体影响TMEM 106 B原纤维的机制 形成，以及TMEM 106 B遗传变异和原纤维的潜在功能后果 积累我们对后者的做法将是双重的：作为一种以候选人为基础的做法，我们将确定 TMEM 106 B遗传变异是否影响神经元中的溶酶体功能，作为一种无偏的方法，我们 将使用蛋白质组学分析来建立蛋白质-蛋白质相互作用和共聚集网络， 和不溶性部分的患者大脑，重点是在T185等位基因携带者与 S185保护基因型携带者。

PROJECT SUMMARY/ABSTRACT Filaments derived from transmembrane protein 106B (TMEM106B) were recently discovered to represent a novel pathological hallmark in a range of neurodegenerative disorders, including TDP-43 proteinopathies, synucleinopathies, and tauopathies. Notably, TMEM106B genetic variants are linked to risk of frontotemporal lobar degeneration with TDP-43 inclusions (FTLD-TDP), particularly cases with progranulin (GRN) and chromosome 9 open reading frame 72 (C9ORF72) mutations, and limbic-predominant age-related TDP-43 encephalopathy (LATE) neuropathologic change. TMEM106B variants also associate with cognitive decline in patients with amyotrophic lateral sclerosis. While several single nucleotide polymorphisms (SNPs) in TMEM106B have been identified and linked to disease risk, only one (rs3173615) introduces a coding change (p.T185S) and it is in high linkage disequilibrium with other risk SNPs. To investigate the intriguing idea that rs3173615 could modulate disease risk through regulation of TMEM106B deposition, we developed an antibody against the TMEM106B filament core sequence. Consistent with recent reports, we detected TMEM106B-positive filaments in the sarkosyl-insoluble fraction from FTLD-TDP and LATE patients. Remarkably, we also observed increased accumulation of insoluble TMEM106B in FTLD-TDP patients homozygous for the rs3173615 risk allele (encoding threonine at residue 185 instead of serine). Collectively, these findings support the hypothesis that TMEM106B aggregation explains the link between genetic variation at the TMEM106B locus and disease risk – and we suspect that it could also explain potential links between rs3173615, TDP-43 proteinopathy, and cognitive decline. We also speculate that differences in TMEM106B accumulation contribute to clinical and pathologic heterogeneity in both FTLD and LATE. Moreover, given that LATE is associated with greater hypometabolism on [18F] fluorodeoxyglucose PET (FDG-PET) in the frontal lobe, a region populated by TMEM106B fibrils, we predict that rs3173615 genotype will also associate with neuroimaging measures of neurodegeneration. In this project, we will investigate the impact of rs3173615 genotype on TMEM106B aggregation and assess whether it associates with TDP-43 proteinopathy and clinical outcomes. We will also explore the mechanism by which the rs3173615 coding variant affects TMEM106B fibril formation, as well as the potential functional consequences of TMEM106B genetic variation and fibril accumulation. Our approach to the latter will be two-fold: as a candidate-based approach, we will determine whether TMEM106B genetic variants impact lysosomal function in neurons, and as an unbiased approach, we will use proteomic analyses to build protein-protein interaction and co-aggregation networks from the soluble and insoluble fractions of patient brains, focusing on differences observed in carriers of the T185 allele versus carriers of the S185 protective genotype.