In PD patients and PD models triggered by 6-hydroxydopamine (6-OHDA) and 1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), DMT1, which is responsible for transporting ferrous iron, is upregulated in the substantia nigra, which in turn leads to the degeneration of dopaminergic neurons. The gene discussed is SLC11A2; the disease is Parkinson disease.