Regulates Expression in Pharyngeal Epithelium and Affects Interaction With Neural Crest Cells.

Craniofacial morphogenesis depends on proper migration of neural crest cells and their interactions with placodes and other cell types. genes provide positional information and are important in patterning the neural crest and pharyngeal arches (PAs) for coordinated formation of craniofacial structures. genes are expressed in the surface ectoderm and epibranchial placodes, their roles in the pharyngeal epithelium and their downstream targets in regulating PA morphogenesis have not been established. We altered the code in the pharyngeal region of the mutant, in which is driven to ectopically expressed in domain in the second pharyngeal arch (PA2). In the transgenic mutant, ectopic expression was restricted to the surface ectoderm, including the proximal epibranchial placodal region and the distal pharyngeal epithelium. The mutants displayed hypoplasia of PA2, multiple neural crest-derived facial skeletal and nerve defects. Interestingly, we found that in the mutant, expression of the Notch ligand was specifically up-regulated in the ectodermal pharyngeal epithelial cells of PA2. By molecular experiments, we demonstrated that Hoxb3 could bind to an upstream genomic site S2 and directly regulate expression. In the mutant, elevated expression of in the pharyngeal epithelium led to abnormal cellular interaction and deficiency of neural crest cells migrating into PA2. In summary, we showed that regulates Jag1 expression and proposed a model of pharyngeal epithelium and neural crest interaction during pharyngeal arch development.