C9orf72 and frontotemporal dementia: About one-third of FTD patients have an autosomal dominant family history (Rohrer et al., 2009), typified by mutations in three genes: granulin (GRN; Baker et al., 2006; Cruts et al., 2006), chromosome 9 open reading frame 72 (C9orf72) (DeJesus-Hernandez et al., 2011; Renton et al., 2011) and microtubule-associated protein tau (MAPT; Hutton et al., 1998).