PRKN and Parkinson disease: Because the pathological hallmark of PD is the progressive loss of dopamine neurons in the substantia nigra and previously published data indicate that Parkin-/- and DJ-1-/- mice do not have changes in numbers of nigral dopaminergic neurons [14,16,18-24,28,33], we postulated that mice with a deficiency for major antioxidant proteins in addition to Parkin and DJ-1 would show an age-dependent loss of dopamine neurons in the substantia nigra and thereby model human PD neuropathology.