GRN and amyotrophic lateral sclerosis: Specifically in FTLD, aberrant DNA methylation patterns were reported in causal genes such as C9orf72 for which several studies have shown hypermethylation of a CGI located in the promoter region, as well as at the repeat expansion itself, in blood and brain tissue from FTLD and FTLD patients with concomitant ALS (FTLD-ALS) [24–26], and also in GRN, where promoter hypermethylation was reported in peripheral blood mononuclear cells (PBMCs), lymphoblasts and brain tissue from FTLD patients, and shown to negatively correlate with GRN expression [27, 28].