HTT and Huntington disease: Additionally, two HD mice models, R6/2 (which expresses exon 1 of the human HTT gene with ~150 CAG repeats) and YAC128 (transgenic yeast artificial chromosome (YAC) mice expressing full-length human HTT gene with 128 CAG repeats) mice showed specifically increased levels of the autophagy markers p62 and LC3-II in the striatum at a later age (18 months) [270], suggesting deficit(s) in autophagy-mediated protein degradation.