TH and Parkinson disease: Though the most prominent neuropathological feature of PD is the selective loss of DA neurons in the substantia nigra (SN), immunohistochemical analysis of aged DJ-1-/- mice using an antibody specific for tyrosine hydroxylase (TH) revealed normal TH staining in the SN and normal morphology of DA neurons at the age of 24–27 months (Fig. 2C–F).