C9orf72 and frontotemporal dementia: Mutant genes causing both ALS and FTD include TARDBP encoding TDP43, FUS encoding fused in sarcoma and C9orf72; the disease causing mutations in C9orf72 involve expansion of an intronic hexanucleotide repeat which is translated into neurotoxic dipeptide repeat proteins (DPRs) (Ling et al., 2013; Robberecht and Philips, 2013; Abramzon et al., 2020).