Finally, although protein phosphatase one regulatory inhibitor subunit 1A Ppp1r1a (down-regulation assigned to Drd1-MSNs: pathogenic response that is mitigated) is not formally linked to neurobehavioral phenotypes in HD models, protein phosphatase inhibition may be relevant to several diseases, including NDs (Vintonyak et al., 2011). Here, PPP1R1A is linked to Huntington disease.