['To determine if distinct populations of cranial neural crest cells (CNCC) exist by characterization of their divergent gene expression patterns.', 'Identification of unique populations of CNCC was determined by a combination of lineage and immunohistochemical analyses.', "Department of Pathology, Children's Hospital of Philadelphia and the University of Pennsylvania School of Medicine, Philadelphia, PA 19104.", 'We found antibodies of two proteins previously described as identifying all CNCC, label three populations of CNCC at specific time-points. Furthermore, the activating protein 2 (AP-2) expressing CNCC become neural or mesenchymal NCC derivatives whereas the HNK-1 labeled cells do not participate in the mesenchymal lineage.'] Do aP-2 and HNK-1 define distinct populations of cranial neural crest cells?