Cell lineage analysis in neural crest ontogeny.

The neural crest is a transitory and pluripotent structure of the vertebrate embryo composed of cells endowed with developmentally regulated migratory properties. We review here a series of studies carried out both in vivo and in vitro on the ontogeny of the neural crest in the avian embryo. Through in vivo studies we established the fate map of the neural crest along the neuraxis prior to the onset of the migration and we demonstrated the crucial role played by the tissue environment in which the crest cells migrate in determining their fate. Moreover, the pathways of neural crest cell migration could also be traced by the quail-chick marker system and the use of the HNK1/NC1 monoclonal antibody (Mab). A large series of clonal cultures of isolated neural crest cells showed that, at migration time, most crest cells are pluripotent. Some, however, are already committed to a particular pathway of differentiation. The differentiation capacities of the pluripotent progenitors are highly variable from one to the other cell. Rare totipotent progenitors able to give rise to representatives of all the phenotypes (neuronal, glial, melanocytic, and mesectodermal) encountered in neural crest derivatives were also found. As a whole we propose a model according to which totipotent neural crest cells become progressively restricted (according to a stochastic rather than a sequentially ordered mechanism) in their potentialities, while they actively divide during the migration process. At the sites of gangliogenesis, selective forces allow only certain crest cells potentialities to be expressed in each type of peripheral nervous system (PNS) ganglia.