UASt regulatory sequences drive expression of a monocistronic transcript that encodes only the canonical Hsap\FUS coding sequence that is encoded in the +1 frame by the Hsap\FUS transcript represented by ENST00000254108 (GenBank:NM_004960); the sequence has been mutated so that this +1 frame coding sequence encodes a disease-related variant (it carries the R495X mutation that causes a premature stop codon and which is associated with severe familial and sporadic amyotrophic lateral sclerosis). The endogenous ENST00000254108 transcript can also encode an alternative 'altFUS' open reading frame (GenBank:BK012000) in the +2 frame; this transgene does not express the altFUS protein due to every Met residue (ATG) in the altFUS +2 frame having been mutated to Thr (ACG) (these mutations are synonymous in the +1 frame of the the canonical Hsap\FUS coding sequence, being TAT to TAC, which both encode Tyr).