EXPRESSION OF THE GAP JUNCTION PROTEINS CONNEXIN31 AND CONNEXIN43 CORRELATES WITH COMMUNICATION COMPARTMENTS IN EXTRAEMBRYONIC TISSUES AND IN THE GASTRULATING MOUSE EMBRYO, RESPECTIVELY

We have characterized the pattern of connexin expression in embryonic and extraembryonic tissues during early mouse development, In the prei mplantation blastocyst, at 3.5 days post coitum (dpc), immunofluoresce nt signals specific for connexin31 and connexin43 proteins were presen t in both the inner cell mass and the trophectoderm, as shown by confo cal laser scan microscopy, Immediately after implantation at 6.5 dpc, however, we find complete compartmentation of these two connexins: con nexin31 mRNA and protein are expressed exclusively in cells derived fr om the trophectoderm lineage, whereas connexin43 mRNA and protein are detected in cells derived from the inner cell mass. This expression pa ttern of connexin31 and connexin43 is maintained at 7.5 dpc when the a xial polarity of the mouse embryo is established. It correlates with t he communication compartments in extraembryonic tissues and the gastru lating mouse embryo, respectively, The communication boundary between those compartments may be due to incompatibility of connexin31 and con nexin43 hemichannels, which do not communicate with each other in cell culture.