SOD1 and amyotrophic lateral sclerosis: Altogether 20 genes are linked to familial ALS, most of which are related to 4 genes: mutations in chromosome 9 open reading frame 72 (C9ORF72) which account for about 35% of hereditary ALS, superoxide dismutase 1 (SOD1) mutations which cover about 20%, RNA binding protein FUS/TLS (FUS) mutations which occupy about (1–5%), and TAR DNA binding protein 43 (TDP) -43) taking up approximately (1–5%) [69, 70].