Cyclic AMP regulation of P0 glycoprotein and myelin basic protein gene expression in semi-differentiated peripheral neurinoma cell line D6P2T.

We have analyzed the effects of cAMP-elevating drugs (dibutyryl cAMP, forskolin, and isobutyl methylxanthine) on growth properties and myelin-specific gene expression in the peripheral neurinoma cell line D6P2T. The steady-state levels of RNA and polypeptide for the two major PNS myelin proteins, P0 glycoprotein (P0) and myelin basic protein (MBP), were measured by Northern blotting and immunoblotting, respectively. The levels of the two RNAs in individual cells were examined by in situ hybridization. The transcriptional activities of the P0 and MBP genes were analyzed by nuclear run-off experiments. Treatment with cAMP-elevating agents caused cell aggregation and dose-dependent increase in growth control. Expression of P0 RNA was constitutive in untreated cells and was repressed at high doses. Expression of MBP RNA was induced at low doses and repressed at higher doses. For both MBP and P0 the effects on gene expression were first detected after a lag of approximately 6 h, were manifested in all cells and were mediated, at least in part, at the transcriptional level. The level of P0 polypeptide was proportional to the level of P0 RNA, but MBP polypeptide was not detectable even under conditions where MBP RNA was induced. The results with this clonal model suggest that cAMP plays a pivotal role in regulation of growth and gene expression during Schwann cell differentiation.