C9orf72 and amyotrophic lateral sclerosis: It is not known whether the C9ORF72 functions are the same as those of other ALS-related genes such as TDP-43 and FUS. It is important to note that C9ORF72 expression is also reduced in many ALS cases with the negative pathogenic G4P2 repeat, suggesting that C9ORF72 may exert synergistic effects with other ALS-related genes.