Regional and cellular expression of the parkin gene in the rat cerebral cortex

A mutation in the parkin gene has been identified as the cause for an autosomal recessively inherited form of early onset Parkinson's disease. We have recently isolated the mRNA coding for the rat homologue of parkin and showed its widespread expression in the central nervous system (CNS) by in situ hybridization. In the present study we investigated the distribution of parkin in the rat cerebral cortex with a polyclonal antibody that reacts with a single approximately 52-kDa protein, corresponding to the predicted molecular mass of parkin. Conventional light microscopic studies revealed intense parkin immunoreactivity (IR) throughout the cortex. Examination of mixed cortical neuro-glial cultures by indirect immunofluorescence technique coupled to traditional epifluorescence and confocal microscopy analysis demonstrated the expression of parkin in the cytoplasm and neurites of neurons, and its absence in glial fibrillary acidic protein (GFAP)-positive astrocytes. The predominant neuronal parkin-IR and -mRNA expression was confirmed by Western blot analysis and reverse transcription-polymerase chain reaction (RT-PCR), respectively, performed on highly enriched neuronal and type I astrocytes cultures. The information gathered in our study about the cellular and subcellular distribution of parkin should facilitate further research on its physiological role in the nervous system.