Notable examples are HD, caused by an expansion in the huntingtin gene (HTT), and certain familial forms of amyotrophic lateral sclerosis (ALS) that are considered monogenic, associated with mutations in SOD1 (superoxide dismutase), TARDBP (Transactive response DNA-binding protein), or FUS [18]. The gene discussed is TARDBP; the disease is amyotrophic lateral sclerosis.