Association of cell and substrate adhesion molecules with connexin43 during intramembranous bone formation

Prior studies in our laboratory have demonstrated an association of specifi c gap junction proteins with intramembranous bone formation in the avian ma ndible. The purpose of the present study tvas to extend these observations by determining if there was a relationship between the expression of one of the gap junction proteins examined previously (connexin43) and the express ion of specific cell adhesion (CAM) and/or substrate adhesion (SAM) molecul es [i.e. NCAM, A-CAM (N-cadherin) and tenascin (tenascin-C)] that have prev iously been shown to be associated with bone formation. Immunohistochemical localization of connexin43, tenascin, NCAM and N-cadherin was performed on serial sections of mandibles of chick embryos from 6 to 12 days of incubat ion. Analysis of adjacent serial sections revealed that the NCAM and tenasc in immunostaining that appeared initially on the lateral aspect of Meckel's cartilage preceded the overt expression of trabecular bone. At subsequent stages, NCAM and tenascin staining gradually overlapped the region of conne xin43 expression. In contrast, the expression of N-cadherin was found to co localize with that of connexin43 from the first appearance of connexin43 ex pression. Most significantly, although the domains of NCAM and tenascin exp ression were initially separate from that of connexin43, bone formation ori ginated only in the region where these domains intersected. These findings suggest that, of the CAMs and SAMs examined, N-cadherin appears to be assoc iated with the establishment of cell contacts responsible for the presence and/or maintenance of connexin43-mediated gap junctional communication, whi le tenascin and NCAM appear to be associated, in a more specific manner, wi th processes that accompany the overt expression of the osteogenic phenotyp e. (C) 1998 Chapman & Hall.