MCBRATNEY, Brandeis M. ; MORRISS-KAY, Gillian M.; Harvard University, Cambridge, MA; University of Oxford, Oxford, UK: Neural Crest and Mesoderm Contributions to the Mammalian Cranial Base

The cranial base is the oldest part of the vertebrate skull, thus understanding variations in tissue origins among vertebrate basicrania may clarify the developmental basis of variations in craniofacial form. We examined the contribution of neural crest cells to the mouse cranial base using a permanent neural crest cell lineage marker, Wnt1-Cre/R26R. X-gal staining of E10.5 to E17.5 transgenic mouse embryos showed neural crest cells contribute to the cranial base components of the frontal, ethmoid, presphenoid, and basisphenoid bones. The basioccipital bone and otic capsules are mesoderm derived. Observations of quail-chick chimeras have demonstrated the neural crest-mesoderm boundary is between the presphenoid and basisphenoid. Le Douarin et al. (Dev Biol 1993, 159: 24-49) note that this boundary is coincident with the division between the prechordal and chordal skull. In mice, however, the neural crest-mesoderm boundary is between the body of the basisphenoid and basioccipital bones. Therefore, the boundary between the prechordal and chordal skull in mice is not coincident with the neural crest-mesoderm boundary.