DJ-1 mRNA anatomical localization and cell type identification in the mouse brain

Mutations in DJ-1 cause familial Parkinson's disease (PD). The expression pattern of DJ-1 in the brain remains controversial. In the present study, we used DJ-1 deficient mice as negative controls and examined DJ-1 mRNA expression in mouse brains. In sequential double labeling on the same sections, in situ hybridization of DJ-1 mRNA was followed by immunofluorescence detection of cell type markers. We found that DJ-1 mRNA was expressed in the majority of neurons in all brain areas examined. In particular, all dopamine neurons in the ventral midbrain expressed DJ-1 mRNA. In contrast, the choroid plexus and ependymal cells lining the ventricles were the only non-neuronal regions strongly expressing DJ-1 mRNA. DJ-1 mRNA was not detected in astrocytes. The fact that DJ-1 mRNA is expressed in all nigra dopamine neurons but not in astrocytes suggests that its potential neuroprotective role could be cell-autonomous. Moreover, that DJ-1 expression is not restricted to substantia nigra dopamine neurons suggests that PD-linked mutant DJ-1 may interact with other predisposing factors to cause the relatively selective dopamine neuron degeneration in Parkinson's disease.