Connexin43 gap junction protein plays an essential role in morphogenesis of the embryonic chick face

Normal outgrowth and fusion of facial primordia during vertebrate developme nt require interaction of diverse tissues and co-ordination of many differe nt signalling pathways. Gap junction channels, made up of subunits consisti ng of connexin proteins, facilitate communication between cells and are imp licated in embryonic development. Here we describe the distribution of conn exin43 and connexin32 gap junction proteins in the developing chick face. T o test the function of connexin43 protein, we applied antisense oligodeoxyn ucleotides that specifically reduced levels of connexin43 protein in cells of early chick facial primordia. This resulted in stunting of primordia out growth and led to facial defects. Furthermore, cell proliferation in region s of facial primordia that normally express high levels of connexin43 prote in was reduced and this was associated with lower levels of Msx-1 expressio n. Facial defects arise when retinoic acid is applied to the face of chick embryos at later stages. This treatment also resulted in significant reduct ion in connexin43 protein, while connexin32 protein expression was unaffect ed. Taken together, these results indicate that connexin43 plays an essenti al role during early morphogenesis and subsequent outgrowth of the developi ng chick face. (C) 2001 Wiley-Liss, Inc.