DJ-1 mutations cause autosomal recessive early-onset Parkinson disease (PD). We report a model of PD pathology: the DJ1-C57 mouse. A subset of DJ-1-nullizygous mice, when fully backcrossed to a C57BL/6 [corrected] background, display dramatic early-onset unilateral loss of dopaminergic (DA) neurons in their substantia nigra pars compacta, progressing to bilateral degeneration of the nigrostriatal axis with aging. In addition, these mice exhibit age-dependent bilateral degeneration at the locus ceruleus nucleus and display mild motor behavior deficits at aged time points. These findings effectively recapitulate the early stages of PD. Therefore, the DJ1-C57 mouse provides a tool to study the preclinical aspects of neurodegeneration. Importantly, by exome sequencing, we identify candidate modifying genes that segregate with the phenotype, providing potentially critical clues into how certain genes may influence the penetrance of DJ-1-related degeneration in mice.