Drosophila models of C9ALS/FTD (C9 models) are well characterised; accumulating evidence suggests that arginine-rich (GR) toxic dipeptide repeats (DPRs), produced via the non-ATG (RAN) translation of hexanucleotide GGGGCC (G4C2) repeats in both the sense and antisense directions and in all reading frames, drive C9ALS/FTD pathogenicity [30,31,32,33,34,35]. The gene discussed is C9; the disease is frontotemporal dementia.