Taken together, the results of our present study showed that miR-199a-3p functions as a direct downstream molecule of XIST, and silencing XIST or miR-199a-3p overexpression attenuates MPP+/MPTP-induced cellular toxicity by downregulating Sp1 and LRRK2, suggesting that XIST and miR-199a-3p play important roles in the neurodegeneration induced by PD progression (Figure 10). The gene discussed is SP1; the disease is Parkinson disease.