C9orf72 and amyotrophic lateral sclerosis: While several C9orf72 ALS/FTD mouse models exhibit gliosis and inflammation (Liu et al., 2016; O'Rourke et al., 2016; Schludi et al., 2017; Zhang et al., 2018), mouse models of C9orf72 deficiency show a more defined contribution of microglia to disease phenotypes.