C9orf72 and frontotemporal dementia: Mutations in the genes that encode tau (MAPT), progranulin (GRN) and C9orf72 are the most common causes of FTD, while additional rare mutations have been identified in valosin-containing protein (VCP), TDP-43 (TARDBP), fused in sarcoma (FUS) (Rohrer and Warren, 2011) and TANK- binding kinase 1 (TBK1) (Gijselinck et al., 2015; Le Ber et al., 2015; Pottier et al., 2015; van der Zee et al., 2017).