Differential expression of CPD1 during postnatal development in the mouse cerebellum

Several regulated mRNAs were detected by applying differential display to t he mouse cerebellum during postnatal development. One cDNA fragment, referr ed to as CPD1 (GenBank U89345), was characterized and cloned. Northern blot s showed maximum mRNA expression at postnatal day seven (P7). The mRNA enco des a protein of 260 amino acids. In situ RT-PCR showed that CPD1 is expres sed mainly in granule cells and faintly in Purkinje cells. Polyclonal rabbi t antibodies and oligobodies (oligonucleotide-based synthetic antibodies) r evealed a protein of 34 kDa in Western blots. Immunohistochemistry showed n ot only marked nuclear staining but also mild cytoplasmic localization. Gra nule cells undergoing active division (P4) showed very little expression of CPD1 protein, which increases from P7 to P17. CPD1. affinity-purified usin g a chemically synthesized oligobody inhibits the activity of protein phosp hatase PP2A but not protein phosphatase PP1. Differentiated PC12 cells also showed nuclear and cytoplasmic localization. interestingly, maximal cytopl asmic CPD1/PP2A colocalization was observed near cell membrane regions that are far from growing neurites, and on growing cones. These results suggest that CPD1 might have an important role in cerebellar development. (C) 2001 Elsevier Science B.V. All rights reserved.