[Cell communication in the development of the oral cavity]

The cadherins are a family of a calcium-dependent cell adhesion molecules that are regulated both spatially and temporally during development. Epithelial cadherin (E-cadherin) is present in the epithelial cells in both the embryo and yolk sac during organogenesis. In many studies, the presence of E-cadherin was analyzed during normal and disturbed craniofacial development with respect to palate and tooth formation. E-cadherin was present in epithelia of both ectodermal and endodermal origin. The expression level of E-cadherin increased with age and differentiation. The expression pattern of E-cadherin implies that this molecule has a role during normal development of the epithelia of the cranio-facial complex. Morphogenesis and cell differentiation in the developing tooth are controlled by a series of reciprocal interactions between the epithelial and mesenchymal tissues. The exact molecular mechanisms operating in these interactions are unknown at present, but both structural components of the extracellular matrix (ECM) and diffusible growth factors have been suggested to be involved. In this review article we summarize our findings on the distribution patterns of three ECM molecules and two cell surface receptors during tooth morphogenesis through bud, cap, and bell stages of development. The examined molecules include fibronectina and tenascin, which all represent components of the mesenchymal ECM, the cell surface proteoglycan, syndecan, which functions as a receptor for interstitial matrix. Based on the observed changes in distribution patterns and on experimental evidence, roles are suggested for these molecules in epithelial-mesenchymal interactions during tooth development. C-Cam is a cell surface glycoprotein that is involved in cell adhesion and may play a role in histogenesis and organogenesis. It is a member of the carcinoembryonic antigen (CEA) gene family, which is a subfamily of the immunoglobulin gene superfamily. The presence of C-CAM in all proliferating craniofacial epithelia indicates that this molecule may play an important role in development.