Familial ALS has also been linked to mutations in more than 50 separate genes that are known as disease-modifying or causative of ALS, of which TAR DNA-binding protein 43 kDa (TDP-43, encoded by TARDBP) fused in sarcoma (FUS) and C9ORF72, as described above, have been most extensively characterized. This evidence concerns the gene TARDBP and amyotrophic lateral sclerosis.