FUS, the most frequently mutated gene related to the pathogenesis of sporadic JALS, consists of 15 exons and encodes a multi-domain, dosage-sensitive protein that is associated with a variety of neurodegenerative diseases, including ALS, frontotemporal lobar degeneration (FTLD), and polyglutamine diseases. This evidence concerns the gene FUS and juvenile amyotrophic lateral sclerosis.