The coding for the mostly cytosolic form of the Cu–Zn superoxide dismutase, was one of the first genetic causes of familial ALS to be discovered, thus the effects of the deletion and overexpression of the SOD1 protein and SOD1 mutants have been a general research focus and have also been studied using the CLS assay. The gene discussed is SOD1; the disease is amyotrophic lateral sclerosis.