PATTERNS OF CYCLIC-AMP-DEPENDENT PROTEIN-KINASE GENE-EXPRESSION DURING ONTOGENY OF THE MURINE PALATE

Normal growth and differentiation of embryonic palatal tissue depends on regulated levels of intracellular cAMP. Cyclic AMP-dependent protei n kinases (PKA) act to mediate the biological activities of cAMP. PKA isozyme protein profiles demonstrate a clear pattern of temporal alter ations in embryonic palatal tissue during its development. In order to ascertain the molecular basis for changing PKA isozyme profiles durin g palatal ontogeny, the spatial and temporal expression of mRNAs for r egulatory (RI alpha, RII alpha, and RII beta) and catalytic (C alpha) subunits of PKA was examined. RNA extracted from murine embryonic pala tal tissue (days 12-14 of gestation) was examined by Northern blot ana lysis. Significant levels of constitutively expressed RI alpha and C a lpha mRNA were seen on all days of gestation examined. RI alpha transc ripts were substantially less abundant in palate mesenchymal cells in vitro than in palatal tissue in vivo. Levels of RII alpha and RII beta mRNA were highest on gestational day (CD) 12, a period characterized by pronounced palatal tissue growth. In addition, patterns of tissue d istribution of RII beta, not previously described, were examined in th e developing embryonic palate. A dramatic developmental shift in tissu e distribution of RII beta was seen. The isozyme was evenly distribute d between palatal epithelial and mesenchymal cells on GD 12 but by GD 14, RII beta was predominantly localized to palatal epithelial cells. Direct activation of adenylate cyclase with forskolin in murine embryo nic palate mesenchymal (MEPM) cells resulted in an increase in RII alp ha mRNA levels but had no effect on steady state levels of RII beta or C alpha mRNA. In addition, elevation of intracellular levels of cAMP resulted in a shift in the transcriptional profile of RI alpha mRNAs. Results of th is study document specific patterns of expression for th e genes encoding the various cAMP-dependent protein kinase regulatory and C alpha subunits in murine embryonic palatal tissue. In addition, we have demonstrated adaptational changes of this kinase in MEPM cells in response to conditions of increased intracellular levels of cAMP. (C) 1995 Wiley-Liss, Inc.