Furthermore, MTH1-null mice, exhibiting an increased accumulation of 8-oxo-G in striatal mtDNA, displayed a more extreme neuronal dysfunction after 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine administration than wt mice; potentially indicating that oxidative DNA damage presents a major risk factor for PD. This evidence concerns the gene NUDT1 and Parkinson disease.