In the vertebrate embryo, multiple cell types originate from a common structure, 
the neural crest (NC), which forms at the dorsal tips of the neural epithelium. 
The NC gives rise to migratory cells that colonise a wide range of embryonic 
tissues and later differentiate into neurones and glial cells of the peripheral 
nervous system (PNS), pigment cells (melanocytes) in the skin and endocrine 
cells in the adrenal and thyroid glands. In the head and the neck, the NC also 
yields mesenchymal cells that form craniofacial cartilages, bones, dermis, 
adipose tissue, and vascular smooth muscle cells. The NC is therefore a model 
system to study cell diversification during embryogenesis and phenotype 
maintenance in the adult. By analysing the developmental potentials of quail NC 
cells in clonal cultures, we have shown that the migratory NC is a collection of 
heterogeneous progenitors, including various types of intermediate precursors 
and highly multipotent cells, some of which being endowed of self-renewal 
capacity. We also have identified common progenitors for mesenchymal derivatives 
and neural/melanocytic cells in the cephalic NC. These results are consistent 
with a hierarchical model of lineage segregation wherein environmental cytokines 
control the fate of progenitors and stem cells. One of these cytokines, the 
endothelin3 peptide, promotes the survival, proliferation, and self-renewal 
capacity of common progenitors for glial cells and melanocytes. At 
post-migratory stages, when they have already differentiated, NC-derived cells 
exhibit phenotypic plasticity. Epidermal pigment cells and Schwann cells from 
peripheral nerves in single-cell culture are able to reverse into multipotent 
NC-like progenitors endowed with self-renewal. Therefore, stem cell properties 
are expressed by a variety of NC progenitors and can be re-acquired by 
differentiated cells of NC origin, suggesting potential function for repair.