Fgfr1regulates patterning of the pharyngeal region

Abstract

Development of the pharyngeal region depends on the interaction and integration of different cell populations, including surface ectoderm, foregut endoderm, paraxial mesoderm, and neural crest. Mice homozygous for a hypomorphic allele ofFgfr1have craniofacial defects, some of which appeared to result from a failure in the early development of the second branchial arch. A stream of neural crest cells was found to originate from the rhombomere 4 region and migrate toward the second branchial arch in the mutants. Neural crest cells mostly failed to enter the second arch, however, but accumulated in a region proximal to it. Both rescue of the hypomorphicFgfr1allele and inactivation of a conditionalFgfr1allele specifically in neural crest cells indicated thatFgfr1regulates the entry of neural crest cells into the second branchial arch non-cell-autonomously. Gene expression in the pharyngeal ectoderm overlying the developing second branchial arch was affected in the hypomorphicFgfr1mutants at a stage prior to neural crest entry. Our results indicate thatFgfr1patterns the pharyngeal region to create a permissive environment for neural crest cell migration.