Expression and localization of the Parkin co-regulated gene in mouse CNS suggests a role in ependymal cilia function

Parkin Co-Regulated Gene (PACRG) is a gene that shares a bi-directional promoter with the Parkinson's disease associated gene parkin. The functional role of PACRG is not well understood, although the gene has been associated with parkinsonian syndromes and more recently with eukaryotic cilia and flagella. We investigated the expression of Pacrg in the mouse brain by in situ hybridization and observed robust expression of Pacrg in the cells associated with the lateral, third and fourth ventricle, in addition to the aqueduct of Sylvius and choroid plexus. For all regions of Pacrg expression identified, strong expression was observed in the newborn period and this was maintained into adulthood. Immunohistochemical analysis showed that Pacrg was a component of the ependymal cells and cilia lining the ventricles. Based on our results and the previous association of PACRG homologues with cilia and flagella, we propose that Pacrg is a component of the ependymal cilia and may play an important role in motile cilia development and/or function in the CNS.