The transgenic construct contains an N-terminal FLAG-tagged, human fused in sarcoma R521C autosomal dominant mutant isoform (hFUS*R521C) that is associated with familial amyotrophic lateral sclerosis (FALS). The isoform encodes an autosomal dominant missense mutation in the nuclear localization signal at the C-terminus of FUS. The FLAG-tagged hFUS*R521C cDNA sequence (~1.5 kbp) was positioned downstream of the Syrian (golden) hamster prion protein (SHaPrP or Prnp) promoter sequences by insertion into SHaPrP exon 3.