INDUCTION OF THE NEURAL CREST

California Institute Of Technology, Pasadena CA

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Abstract

The neutral crest is a population of migratory cells that arise from the ectoderm of vertebrate embryos and give rise to a diverse range of cell types, including most of the peripheral nervous system, melanocytes and the craniofacial skeleton. It has been classically assumed that the neutral crest is a segregated population in the early ectoderm, lying between the neutral plate and presumptive epidermis. However, our recent studies on avian embryos show that individual precursor cells within the "neutral folds" can form neutral tube (central nervous system), neutral crest (peripheral nervous system) and epidermal derivatives. This led us to explore the interactions that impart the potential form the neural crest. Interestingly, we found that neural crest cells are generated when epidermis and neural plate are juxtaposed-a classic type of embryonic induction. The proposed experiments aim to characterize this inductive interaction that leads to neural crest formation and to examine the plasticity of early ectodermal derivatives. To continue our studies on the mechanisms responsible for genesis of the neural crest, we will further characterize the molecular nature of the inductive interaction and will test the function of some candidate inducers in vivo and in vitro. We will examine the ability of ventralizing signals to compete with induction of the neural crest, using both grafting and ectopic expression paradigms. Finally, we will examine the lineage relationships and plasticity between neural crest cells and other ectodermal derivatives by challenging their prospective fates via transplantation. Much of the experimental design will involve in vivo experimental manipulations coupled with cell marking techniques, molecular biological approaches, as well as in situ hybridization to examine patterns of gene expression. Specific experiments will: 1. Characterize the molecular nature of the inductive interaction underlying neural crest formation. 2. Determine the ability of ventralizing signals to repress neural crest formation. 3. Determine the competence of ectoderm and neural plate to assume a neural crest fate. 4. Determine the competence of neural crest cells to assume a neural tube fate after transplantation into the ventral neural tube.