Previous RNA profiling studies using human and mouse HD brains found a number of critical genes are dysregulated, including downregulation of brain-derived neurotrophic factor (Bdnf), dopamine D2 (Drd2) receptor, and protein phosphatase 1 regulatory inhibitor subunit 1B (Ppp1r1b or Darpp-32)7, 8, 9, 10, 11, 12. Here, PPP1R1B is linked to Huntington disease.