The 240 kb human bacterial artificial chromosome (BAC RP11-866L6), containing the entire 170 kb human Huntingtin genomic locus and approximately 20 kbp of 5' and 50 kbp of 3' flanking sequences and modified to replace the human HTT exon 1 with a loxP-flanked human mutant HTT exon 1 sequence containing 97 mixed CAA-CAG repeats encoding a continuous polyglutamine stretch was further modified to delete the first 17-amino-acid domain (N17; residues 2-16). This modified BAC containing both the 97Q and the deleted N17 domain was microinjected into FVB/NJ fertilized eggs. Three founders were established; N, L, and A. Line N and L show a similar level of expression.