DIFFERENTIAL EXPRESSION OF D-TYPE CYCLINS DURING NEURONAL MATURATION

The multiple cyclins play essential roles in eucaryotic cell cycle. We previously reported that the expression of a D type G1 cyclin (p36(cy clinD1)) in neurons was increased at the onset of brain maturation. Du ring neuronal differentiation of PC12h cells induced by nerve growth f actor (NGF), expression of p36(cyclinD1) and p46(cyclinX) was enhanced concomitant with neuronal maturation. In contrast, p34(cyclinD2), whi ch was highly expressed in undifferentiated cells, decreased as the ce lls matured. In situ hybridization and Western blot analyses demonstra ted that embryonic rat brain strongly expressed cyclin D2 gene, but it s expression was dramatically repressed in matured brain. These data s uggest differential roles of the D type cyclins in the process of neur onal differentiation and/or function.