Similar expression constructs encoding exon 1 of the Htt protein with an expanded polyglutamine tract have been previously used in cell culture models of polyglutamine toxicity [6], [40] and in the generation of the well characterized R6/2 transgenic mouse line [41]; R6/2 mice develop a progressive neurological phenotype with motor symptoms resembling those in HD [42]. Here, HTT is linked to Huntington disease.