SOD1 and amyotrophic lateral sclerosis: ALS can be classified into sporadic ALS, caused by unknown pathogenesis, and familial ALS, caused by genetic defects directly linked to pathogenesis, including superoxide dismutase 1 (SOD1), transactive response DNA-binding protein (TDP-43), fused in sarcoma/translocated in liposarcoma protein (FUS/TLS), and TATA-box binding protein-associated factor 15 (TAF15).