C9orf72 and frontotemporal dementia: Hexanucleotide GGGGCC repeat expansions in C9orf72 (C9ALS) are causative of familial and sporadic ALS and ALS/FTD (Taylor et al, 2016), and patients with C9ALS show TDP-43 pathologies that include TDP-43 nuclear exclusion and splicing abnormalities (Ma et al, 2022; Tziortzouda et al, 2021; Vanden Broeck et al, 2014).