Mutations in most of these genes are very infrequent and most Mendelian ALS cases are due to mutations in chromosome 9 open reading frame 72 (C9orf72), superoxide dismutase 1 (SOD1), fused-in sarcoma (FUS) and TAR DNA binding protein (TARDBP). Here, TARDBP is linked to amyotrophic lateral sclerosis.