The mouse prion promoter (containing 1140 bp of the prion protein gene upstream of exon 1, the complete exon 1, intron 1, and the first 52 bp of exon 2) drives the expression of the full-length human ATAXIN-3 (ATAXIN-3c isoform that contains an additional ubiquitin-interacting motif at its C terminus) containing 70 CAG repeats. Four lines were created: 70.42, 70.48, 70.61, and 70.66.