DRD2 and Parkinson disease: Noteworthy, TH, dopamine receptor 2 (DRD2), SLC6A3/DAT, SLC18A2, tubulin beta 2A (TUBB2A), tubulin alpha 4A (TUBA4A), and tubulin beta 3 (TUBB3) were the 7 key genes enriched in the Parkinson disease pathway (Figure 3C).