In the vertebrate embryo, Schwann cells lining the peripheral nerves originate 
from the neural crest (NC), a structure that also gives rise to ganglion 
satellite cells, most of the neurons of the peripheral nervous system, 
melanocytes, and part of the cranial mesenchyme. We have studied the emergence 
of the Schwann cell lineage in vitro in clonal cultures of quail mesencephalic 
NC cells by using the Schwann cell myelin protein antigen as an early and 
specific marker for myelinating and nonmyelinating cells. After 13-16 days in 
culture, numerous clones contained Schwann cell myelin protein-positive cells, 
sometimes isolated and sometimes associated with other NC-derived cell types. 
Detailed phenotypic analysis of the clones allowed us to infer the presence of 
differently committed Schwann-cell ancestors in the NC during the migration 
stage. In particular, we found evidence for the existence of a bipotent 
precursor of Schwann cells and nonneuronal satellite cells; a common precursor 
of neurons, satellite cells, and Schwann cells; and a pluripotent precursor of 
Schwann cells, satellite cells, neurons, and melanocytes. These founder cell 
types coexist in the NC with a committed Schwann cell progenitor of 
high-proliferative potential that differentiates in vitro in the absence of 
other peripheral cells and axons.