PRKN and Parkinson disease: In MPTP-induced PD mice, the expression levels of parkin, PTEN-inducible kinase 1 (PINK1), peroxisome proliferator-activated receptor γ coactivator 1-α, and mitochondrial fusion protein 2 (Mfn2) were significantly downregulated, whereas the expression level of dynamin-associated protein 1 (Drp-1) was significantly upregulated, resulting in a decrease in mitochondrial membrane potential.