Cartilage of the vertebrate jaw is derived from cranial neural crest cells that migrate to the first pharyngeal arch and form a dorsal "maxillary" and a ventral "mandibular" condensation. It has been assumed that the former gives rise to palatoquadrate and the latter to Meckel's (mandibular) cartilage. In anamniotes, these condensations were thought to form the framework for the bones of the adult jaw and, in amniotes, appear to prefigure the maxillary and mandibular facial prominences. Here, we directly test the contributions of these neural crest condensations in axolotl and chick embryos, as representatives of anamniote and amniote vertebrate groups, using molecular and morphological markers in combination with vital dye labeling of late-migrating cranial neural crest cells. Surprisingly, we find that both palatoquadrate and Meckel's cartilage derive solely from the ventral "mandibular" condensation. In contrast, the dorsal "maxillary" condensation contributes to trabecular cartilage of the neurocranium and forms part of the frontonasal process but does not contribute to jaw joints as previously assumed. These studies reveal the morphogenetic processes by which cranial neural crest cells within the first arch build the primordia for jaw cartilages and anterior cranium.

• Keywords
• NASA Discipline Evolutionary Biology, Non-NASA Center,
• MeSH
• Ambystoma embryology   MeSH
• Staining and Labeling MeSH
• Coloring Agents MeSH
• Biological Evolution * MeSH
• Models, Biological MeSH
• Cartilage embryology   ultrastructure   MeSH
• Neural Crest cytology   MeSH
• Embryo, Nonmammalian MeSH
• Fluorescein-5-isothiocyanate MeSH
• In Situ Hybridization MeSH
• Chick Embryo MeSH
• Mandible embryology   growth & development   MeSH
• Maxilla embryology   growth & development   MeSH
• Morphogenesis MeSH
• Body Patterning MeSH
• Green Fluorescent Proteins MeSH
• Animals MeSH
• Check Tag
• Chick Embryo MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Research Support, U.S. Gov't, Non-P.H.S. MeSH
• Research Support, U.S. Gov't, P.H.S. MeSH
• Names of Substances
• Coloring Agents MeSH
• Fluorescein-5-isothiocyanate MeSH
• Green Fluorescent Proteins MeSH