C9orf72 and amyotrophic lateral sclerosis: Mutations in common ALS-related genes, including SOD1, TARDBP, C9ORF72, and FUS, were found in less than 50% fALS and about 5% sALS, and genetic factors were found in only two thirds of fALS and about 10% of sALS, indicating that genetic factors cannot fully explain the pathogenesis of ALS, especially the sporadic form of ALS (Renton et al., 2014; Zou et al., 2017).