BONE MORPHOGENETIC PROTEIN-2 AND PROTEIN-4 EXPRESSION DURING MURINE OROFACIAL DEVELOPMENT

In the developing orofacial region, epithelial-mesenchymal interaction s induce a differentiation cascade leading to bone and cartilage forma tion. Although the nature of this interaction is unknown, bone morphog enetic proteins (BMP)-2 and -4 have been suggested as putative signall ing molecules. Using S-35-labelled cDNA probes, the expression pattern s of BMP-2 and -4 mRNA were examined in murine perioral tissues preced ing, during and following the time of the epithelial-mesenchymal inter action leading to mandibular formation. At embryonic age (E) 9.5 days, a restricted pattern of BMP-4 mRNA was expressed in the epithelium of the developing facial processes. This decreased rapidly, with little or no signal on E10.5 or E11.5. By E13.5, BMP-4 signal was restricted to the dental lamina, follicle and papilla. BMP-2 expression was not p rominent in the developing face until E13.5. At this stage, signal was widespread throughout mesenchyme of neural-crest, but not somatic ori gin. Different domains of expression were present in the developing ep ithelium: for example, there was strong signal in the floor of the mou th and the ventral tongue, in contrast to that of the dorsum of the to ngue and primary palate, which were negative. These results support th e role of BMP-2 and -4 as regulators of orofacial development and demo nstrates different fields of BMP-2 expression in developing oral mucos al epithelium.