Although reducing C9ORF72 in zebrafish or Caenorhabditis elegans can cause motor deficits (Swinnen et al., 2018; Therrien et al., 2013), reduced or even complete deletion of C9ORF72 in mice does not lead to FTD/ALS-like abnormalities, suggesting that loss of C9ORF72 is not the main disease driver (Atanasio et al., 2016; Burberry et al., 2016; Koppers et al., 2015; O’Rourke et al., 2016; Sudria-Lopez et al., 2016; Sullivan et al., 2016; Ugolino et al., 2016). Here, C9orf72 is linked to frontotemporal dementia.