PD-related neuropathology was observed in PD olfactory bulbs including increased α-synuclein (P = 0.03) and DJ1 (P = 0.0004) protein levels, elevated iron (a key regulator of tyrosine hydroxylase function [26]) (P = 0.07) as determined by ICP-MS, as well as the presence of α-synuclein inclusions (Supplementary Fig. 1). Here, PARK7 is linked to Parkinson disease.