Cell proliferation and protooncogene induction in oligodendroglial progenitors.

Cell proliferation and the expression of the protooncogenes c-fos and c-jun have been examined in the primary cultures of oligodendroglial (OL) progenitor cells in response to phorbol 12-myristate 13-acetate (PMA), serum, insulin, insulin-like growth factor-I (IGF-I), platelet-derived growth factor (PDGF), and fibroblast growth factor (FGF). Combined [3H]thymidine autoradiography and immunocytochemistry was used to assess the mitogenic response of O4 (an oligodendrocyte-specific marker)-positive OL progenitors. In addition, the rate of DNA synthesis was measured by the incorporation of [3H]thymidine into acid-precipitable material. It was found that all of the agents tested stimulated DNA synthesis in OL progenitors and induced a rapid increase in c-fos and c-jun protooncogene expression. The induction of c-fos gene expression and DNA synthesis in response to PMA was completely blocked by 1-(5-isoquinolinyl-sulfonyl)-2-methylpiperazine (H-7), a potent inhibitor of protein kinase C (PKC), thereby suggesting a role for PKC in the control of c-fos expression and cell proliferation in OL progenitors.