A YAC containing a full-length human huntingtin gene was modified with a 133 CAG repeat expansion in exon 1 and a mutation in exon 13, at position 586, which encodes the caspase-6 cleavage site. Founder line W7 (C6R7) was subsequently established. Caspase-6 cleavage products are not detected in brain lysates by Western blot.