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

项目摘要/摘要 来自跨膜蛋白106B(TMEM106B)的细丝最近被发现代表一种 一系列神经退行性疾病的新病理特征，包括TDP-43蛋白病， 联核病和变态核病。值得注意的是，TMEM106B基因变异与额颞部疾病的风险有关 伴有TDP-43包涵体的大叶变性(FTLD-TDP)，特别是伴有前颗粒蛋白(GRN)和 9号染色体开放阅读框72(C9ORF72)突变和边缘优势年龄相关的TDP-43 脑病(晚期)神经病理改变。TMEM106B变异也与认知能力下降有关 肌萎缩侧索硬化症患者。而一些单核苷酸多态(SNPs)在 TMEM106B已被识别并与疾病风险相关，只有一个(Rs3173615)引入了编码变化 (p.T185S)，与其他风险SNPs处于高度连锁不平衡状态。调查这个耐人寻味的想法 Rs3173615可以通过调节TMEM106B的沉积来调节疾病风险，我们开发了一种 针对TMEM106B细丝核心序列的抗体。与最近的报告一致，我们发现 FTLD-TDP患者和晚期患者肌糖不溶部分中TMEM106B阳性细丝。 值得注意的是，我们还观察到FTLD-TDP患者中不溶性TMEM106B的积累增加 Rs3173615风险等位基因纯合(编码185位苏氨酸，而不是丝氨酸)。总而言之， 这些发现支持这样的假设，即TMEM106B聚集解释了遗传变异之间的联系 TMEM106B基因座与疾病风险之间的关系--我们怀疑这也可以解释 Rs3173615、TDP-43蛋白病变和认知功能下降。我们还推测，TMEM106B的差异 积聚导致FTLD和晚期的临床和病理异质性。此外，鉴于 晚期与额叶[18F]氟脱氧葡萄糖PET(FDG-PET)的低代谢有关 叶，一个由TMEM106B纤维聚集的区域，我们预测rs3173615基因也将与 神经退行性变的神经成像测量。在这个项目中，我们将研究rs3173615的影响。 TMEM106B聚集性的基因分型及其与TDP-43蛋白病和临床的关系 结果。我们还将探索rs3173615编码变体影响TMEM106B原纤维的机制 TMEM106B基因变异和原纤维的形成以及潜在的功能后果 积累。我们对后者的方法将是双重的：作为一种基于候选人的方法，我们将确定 TMEM106B基因变异是否影响神经元的溶酶体功能，作为一种公正的方法，我们 将使用蛋白质组学分析来构建蛋白质-蛋白质相互作用和共聚集网络 和患者大脑的不溶性部分，重点观察T185等位基因携带者与 S185保护性基因携带者。

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.