American Journal of Medical Genetics Supplement 47-22 zy ED (1988) z K Molecular Determinants of Cranial Neural Crest-Derived Odontogenic Ectomesenchyme During Dentinogenesis Harold C. Slavkin, Mary MacDougall, Margarita Zeichner-David, Peter Oliver, Masanori Nakamura, and Malcolm L. Snead zy NM Laboratory for Developmental Biology, Department of Basic Sciences, School of Dentistry, University of Southern California, L 0s Angeles, California zyxwv KJIHG Positional information on tooth morphogenesis is investigated by the identification of whenand where phenotypic markers are expressed during odontogenesis. This temporal and positional information is correlated with the instructive and permissive signaling required for both dentinogenesis and amelogenesis. Of particular interest is the establishment of a map for the cranial neural crest-derived dental papilla ectomesenchyme and the odontoblast cell lineages. The expression of ectomesenchyme- derived cytotactin, dentin phosphoprotein, and epithelial-derived enamel proteins was studied in mice using embryonic, fetal, and postnatal mandibular first molar tooth organdevelopment. This review summarizes the observations in the context of instructive epithelial-mesenchymal interactions and suggests that amelogenesis imper- fecta and dentinogenesis imperfecta may in part be explained by alterations in these differentiation markers. Recombinant DNA methods should facilitate future investi- gations of these inherited dental disorders. Key words: cytotactin, dentin phosphoprotein, amelogenin, enamelins, inner enamel epitheli odontobhts, tooth morphogenesis, epithelial-mesenchyml interactions, extracell matrix INTRODUCTION One of the most cogent problems in developmental biology concerns how tissue- specific gene expression is regionally specified during embryonic, fetal, and morphogenesis. Cranial neural ixest cells produce embryonic progenitor lineag number of different neuronal and nonneuronal cell types, including chondroblasts, fibroblasts, osteoblasts, and odontoblasts during craniofacial morphogenesis [40,41,48,73]. During embryogenesis, caudal mesencephalic and rostra1 rhombenc cranial neural crest migrate through pathways along the epithelial basal lam extracellular matrix spaces, and other cues derived from other embryonic cell types en route to the forming maxillary and mandibular processes. How are cranial neural Received for publication June zyxwvutsr 2,1987; revision received June 26,1987. Address reprint requests to Dr. Harold C. Slavkin, Laboratory for Developmental Biology, Gerontology Center, Rm 314, University of Southern California, Los Angeles, CA 90089-0191. zyxw 0 1988 Alan R. Liss, Inc.