The transgene comprises a cDNA encoding full length human atrophin 1 containing a 65 residue polyglutamine tract, encoded by 65 CAG repeats, inserted into an expression cassette containing the promoter, 5' intronic and 5' and 3' untranslated region sequences of the mouse prion protein gene. This transgenic line carries more than ten copies of the construct and, as shown by northern and western blot analysis, expresses human atrophin 1 mRNA and protein in the brain.