Parkin expression in the adult mouse brain

Mutations in a protein designated Parkin were shown to be involved in the p athogenesis of autosomal recessive juvenile parkinsonism. Nothing is known about its regional and subcellular distribution in the mouse. In order to e lucidate the Parkin mRNA and protein distribution in the adult mouse, the m ouse cDNA was cloned and polyclonal antisera were generated against the N-t erminal part of mouse Parkin. The antibodies were shown to be specific usin g Western blot analysis, immunostaining of cells transfected with mouse Par kin and pre-absorption tests. The Parkin protein expression profile was stu died using immunohistochemistry and Western blot analysis and was compared with that of the mRNA yielded by in situ hybridization and PT-POP analysis. Parkin protein was widely distributed in all subdivisions of the mouse bra in. Low levels were found in the telencephalon and diencephalon, while the brainstem contained a large number of cells heavily expressing Parkin. Ultr astructural analysis and double immunohistochemistry revealed that the majo rity of Parkin-expressing cells were neurons, while only single glial cells exhibited immunostaining. The protein was distributed nonhomogeneously thr oughout the entire cytoplasm. A subpopulation of Parkin-immunopositive cell s displayed speckled immunodeposits in the nucleus. Dopaminergic cells of t he substantia nigra pars compacta exhibited high levels of Parkin mRNA but no Parkin protein, while the striatum contained immunopositive profiles but no mRNA signals. Our data indicate that Parkin is neither restricted to a single functional system nor associated with a particular transmitter syste m. The speckled nuclear distribution of Parkin immunoreactivity strongly su ggests a role for Parkin in gene expression.