RARB and Huntington disease: Of note, in line with previous studies (Seredenina and Luthi-Carter, 2012; Vashishtha et al., 2013), some of the key HD genes including PCP4, RARB, NGEF, ADCY5, CAMKV, GRM3, BCL11B, CNR1, RGS9, DRD2 and CAMKK2 were downregulated in postmortem neuronal cells but upregulated in some of the cell culture models (Supplementary Figure S4), indicating the distinct differential gene expression patterns in the postmortem primary tissues and cellular models in HD.