NEURAL CREST POTENTIAL FOR TOOTH DEVELOPMENT IN A URODELE AMPHIBIAN -DEVELOPMENTAL AND EVOLUTIONARY SIGNIFICANCE

Tooth development in urodele amphibians occurs from a restricted regio n of anterior cranial neural crest. An in vitro culture system was use d to test the odontogenic potential of more caudal regions of neural c rest, including an ''intermediate region'' of neural folds which has n ever previously been tested for either fate or potential. Explants of different axial levels of neural crest with stomodaeal ectoderm and en doderm demonstrated that odontogenic potential extends not only furthe r caudally than the axial level fated to produce teeth, but also beyon d that with potential to produce cartilage. Our results show that chon drogenic potential is found only within the most rostral portion of th e intermediate region, but that odontogenic potential extends to its m ost caudal limit. This separation of skeletogenic cell lineages in the neural crest necessitates a reevaluation of the designations of ''cra nial'' and ''trunk'' and a reconsideration of the evolutionary implica tions of developmentally distinct crest-derived mesenchyme populations . The proposal that odontogenic potential extends into the trunk neura l crest may be explained as conserved from a phylogenetically older, m ore extensive skeletogenic ability which produced the exoskeleton of m ore basal vertebrates. (C) 1997 Academic Press.