PPARGC1A and Parkinson disease: Among the genes involved in the selected four functional terms, 10 were previously reported in PD studies, including RAC1, IRS2, LEPR, PPARGC1A, CAMKK2, RAB10, RAB13, RAB27B, RAB11A, and JAK2. To confirm their functional roles in PD, we employed the CTD database to confirm their correlation with nervous system diseases via evaluating the disease score.