PPP1R1B and Huntington disease: In addition, we confirmed the expression of genes which expressed in medium spiny neurons such as Ppp1r1b, Drd1, and Drd2. We found that the Ppp1r1b gene, encoding the dopamine- and cAMP-regulated neuronal phosphoprotein (DARPP-32), a GABAergic neuronal marker, was significantly increased in dCas9-sgRNA-treated HD mice compared to Cas9-sgRNA-treated mice.