CX43 GAP JUNCTION GENE-EXPRESSION AND GAP JUNCTIONAL COMMUNICATION INMOUSE NEURAL CREST CELLS

Although gap junctions are not known to be important in mediating cell -cell interactions amongst migratory cells, our studies showed that th e connexin 43 (Cx43) gap junction gene is widely expressed in mouse ne ural crest cell lineages. Using in situ hybridization analysis, Cx43 e xpression was detected in presumptive neural crest cells emerging from the neural folds of the early postimplantation embryo. Neural crest e xpression of the Cx43 gap junction gene was also indicated by the anal ysis of transgenic mice containing a lacZ reporter construct driven th e Cx43 promoter. In neural tube explant cultures these transgenic mice , lacZ expression was observed in the emerging neural crest outgrowths . Whole mount X-gal staining of these transgenic embryos at various st ages of development showed lacZ expression in neural crest cells distr ibuted along the entire craniocaudal axis, with expression found in bo th cranial and trunk neural crest cells contributing io a wide range o f embryonic tissues. This included presumptive cardiac neural crest ce lls localized in the heart. in light of the widespread expression of C x43 in neural crest cell lineages, dye injection studies were carried out to determine if neural crest cells are functionally coupled via ga p junctions. Such studies revealed extensive dye coupling among presum ptive neural crest cells, thus demonstrating that these migratory cell s are indeed gap junctional communication competent. In total, these o bservations suggest that gap junctions may play a role in mouse neural crest development. This possibility is particularly intriguing given the recent finding that the Cx43 knockout mice die of defects associat ed with the outflow tract [Reaume ei al., 1995], a region of the heart in which neural crest cells are required for normal development. Dev. Genet. 20:119-132, 1997. (C) 1997 Wiley-Liss, Inc.