Several groups have found that C9orf72 mRNA levels are reduced in C9ALS/FTD (DeJesus‐Hernandez et al, 2011; Cooper‐Knock et al, 2012; Gijselinck et al, 2012, 2015; Belzil et al, 2013; Ciura et al, 2013; Donnelly et al, 2013; Mori et al, 2013b; Xi et al, 2013) and reduced C9orf72 protein levels have been detected in the frontal cortex of ALS and FTD cases (Waite et al, 2014; Xiao et al, 2015). Here, C9orf72 is linked to frontotemporal dementia.