Although mutations in the SOD1 gene have been found in approximately 15% of familial ALS patients, and about 1% of sporadic ALS patients, the model used in this study-the transgenic SOD1-G93A mouse-represents the one most extensively characterized, because it recapitulates many features of the sporadic ALS phenotype. The gene discussed is SOD1; the disease is amyotrophic lateral sclerosis.