GSK3B and Huntington disease: Consistent with previous work31, we measured GSK3α/β protein levels in our HD cell culture and HD animal brains and observed a trend toward GSK3 downregulation (Supplementary Fig. 3a); levels of the GSK3 active forms (pY279-GSK3α and pY216-GSK3β) in HdhQ111 striatal cells and HD mouse brains were clearly lower than WT counterparts (Supplementary Fig. 3a).