Application of new technologies to studies of neural crest migration and differentiation

This review describes the application of new techniques for examining some longstanding questions in the neural crest system concerning pathways of migration, cell lineage decisions, and importance of the extracellular matrix. The first issue examined involves the migratory pathways followed by neural crest cells. In birds, it has been possible to map crest migratory routes accurately using antibodies that selectively recognize neural crest cells. These antibodies permit the identification of migrating cells in the absence of the surgical trauma incurred by neural tube transplantations. In amphibian embryos, which are more readily accessible to embryological manipulation than are birds, neural fold grafts using two new cell markers have made it possible to map the early stages of neural crest migration using both interspecific and intraspecific chimerae. In both birds and amphibians, a metameric pattern of neural crest migration was observed; this presumably results from interactions with the adjacent somites. A second novel experimental paradigm tests the role of cell surface-extracellular matrix interactions in neural crest migration. Using antibodies to perturb interactions between the cell surface and the extracellular matrix selectively, it has been possible to identify some molecular interactions that are important for aspects of neural crest migration in situ. New techniques have also made it possible to examine the cell lineage decisions of neural crest cells. Using a retrograde labeling technique and a method of microinjecting cells into embryos, we have found that neural crest-derived cholinergic neurons remain plastic with respect to their neurotransmitter expression even after overt differentiation. New cell-marking techniques have made it possible to study neural crest cell lineage by means of clonal analysis. Individual neural crest precursors can be injected with a cell lineage tracer that is passed to all of its progeny. Thus, we can examine the developmental potential of individual neural crest cells. The various experimental paradigms presented in this review illustrate the utility of recent technological advances to study embryological questions that have long concerned investigators interested in the neural crest and in other developmental systems.