Mechanisms of cranial neural crest‐mesoderm interactions

Head development is accomplished by two robust craniofacial mesenchymal populations, paraxial mesoderm (PM) and neural crest (NC). Recent descriptive and experimental analyses are defining a continuum from highly conserved to species‐unique developmental events within these mesenchymes. Subsets of cells within both PM and NC undergo extensive translocations, and the cellular processes that promote as well as constrain these movements will be documented. Within each population are situations where cell:cell relations remain constant during development, and other circumstances where considerable rearrangements occur. Most skeletal progenitors fall into the former category, while muscles and vascular tissues are typically in the latter. An especially cryptic feature of craniofacial development is the interface between PM and NC. Changes in its location during development can profoundly alter patterns of cell differentiation and morphogenesis. This interface acts as a constraint for the movements of some but not all cell types. Defining these dynamic relations both within and between PM and NC populations is a necessary prerequisite to dissecting the molecular events that initiate then sustain the differentiation, growth, and morphogenesis of craniofacial mesenchymal cell populations. Supported by grants from NIDCR and NEI.