FGF2 promotes skeletogenic differentiation of cranial neural crest cells.
The cranial neural crest gives rise to most of the skeletal tissues of the skull. Matrix-mediated tissue interactions have been implicated in the skeletogenic differentiation of crest cells, but little is known of the role that growth factors might play in this process. The discovery that mutations in fibroblast growth factor receptors (FGFRs) cause the major craniosynostosis syndromes implicates FGF-mediated signalling in the skeletogenic differentiation of the cranial neural crest. We now show that, in vitro, mesencephalic neural crest cells respond to exogenous FGF2 in a dose-dependent manner, with 0.1 and 1 ng/ml causing enhanced proliferation, and 10 ng/ml inducing cartilage differentiation. In longer-term cultures, both endochondral and membrane bone are formed. FGFR1, FGFR2 and FGFR3 are all detectable by immunohistochemistry in the mesencephalic region, with particularly intense expression at the apices of the neural folds from which the neural crest arises. FGFRs are also expressed by subpopulations of neural crest cells in culture. Collectively, these findings suggest that FGFs are involved in the skeletogenic differentiation of the cranial neural crest.