SOD1 and amyotrophic lateral sclerosis: However, in the recent years, it has been recognized that about ten percent of ALS cases have a familial cause (fALS); of which about 20% are caused by a mutation in the gene-encoding Cu/Zn superoxide dismutase (SOD1) on chromosome 21q22 [4].This genetic information helped in the developmentof animal models for the study of ALS.