PPP1R1B and Huntington disease: Consistent with the findings in HD R6/2 mice, the immunodensity and protein levels of DARPP-32 were increased and mtHtt aggregate numbers were attenuated in the striatum of CHIR99021-treated YAC128 mice when compared with vehicle-treated HD counterparts (Fig. 2i, j and Supplementary Fig. 2b, f, g).