The TMEM106B locus and TDP-43 pathology in older persons without FTLD

Objective: To determine the independent association of the TMEM106B variants with transactive response DNA binding protein 43 (TDP-43) pathology in older persons without frontotemporal lobar degeneration (FTLD) and to explore functional pathways that link the risk variants to the pathology, including a GRN mRNA pathway.

Methods: Data came from 544 autopsied participants without FTLD in 2 community-based studies of aging. Participants underwent uniform neuropathologic evaluations, including TDP-43 cytoplasmic inclusions. We examined the association of TMEM106B variants with a semiquantitative measure of TDP-43 pathology in a series of regression analysis. We explored potential pathways by leveraging genetic, brain DNA methylation, miRNA, and transcriptomic data collected from this same group of participants.

Results: TDP-43 pathology was identified in 51.7% of the participants. The index single-nucleotide polymorphism (SNP), rs1990622^A, was associated with more advanced TDP-43 pathology. Top hits from fine mapping of the locus were in linkage disequilibrium of the index SNP. The association remained significant after adjustment for other neuropathologies including Alzheimer disease and hippocampal sclerosis (odds ratio = 1.351, 95% confidence interval = 1.068–1.709, p = 0.012). GRN expression was upregulated in rs1990622^AA/AG carriers, and was associated with more advanced TDP-43 pathology. The TMEM106B variants were associated with lower level of DNA methylation in an active enhancer in GRN.

Conclusions: Common variants in TMEM106B serve as a distinct risk factor for TDP-43 pathology in older persons without FTLD. The role of GRN expression and epigenetic mechanisms associating TMEM106B in the accumulation of TDP-43 in older persons require further study.