C9orf72 and amyotrophic lateral sclerosis: In FTD and ALS, two of the most commonly found mutant genes (GRN, C9orf72) encode proteins that have critical roles in phagocytosis and endocytosis which are important for microglial functions (Baker et al., 2006; Cruts et al., 2006; Shatunov et al., 2010; DeJesus-Hernandez et al., 2011; Mok et al., 2012).