C9orf72 and frontotemporal dementia: We searched for known PPIs of MAPT, GRN, HLA-DRA, CTSC, TMEM106B, C9orf72, VCP, UBQLN2 and OPTN (Additional file 2: Table S21a and b), and assessed any nominal overlap with genes co-clustering in modules containing the FTD-genes in the frontal and temporal cortices.