Adhesion and migration of avian neural crest cells on fibronectin require the cooperating activities of multiple integrins of the (beta)1 and (beta)3 families

Based on genetic, functional and histological studies, the extracellular matrix molecule fibronectin has been proposed to play a key role in the migration of neural crest cells in the vertebrate embryo. In the present study, we have analyzed in vitro the repertoire and function of integrin receptors involved in the adhesive and locomotory responses of avian truncal neural crest cells to fibronectin. Immunoprecipitation experiments showed that neural crest cells express multiple integrins, namely (alpha)3(beta)1, (alpha)4(beta)1, (alpha)5(beta)1, (alpha)8(beta)1, (alpha)v(beta)1, (alpha)v(beta)3 and a (beta)8 integrin, as potential fibronectin receptors, and flow cytometry analyses revealed no major heterogeneity among the cell population for expression of integrin subunits. In addition, the integrin repertoire expressed by neural crest cells was found not to change dramatically during migration. At the cellular level, only (alpha)v(beta)1 and (alpha)v(beta)3 were concentrated in focal adhesion sites in connection with the actin microfilaments, whereas the other integrins were predominantly diffuse over the cell surface. In inhibition assays with function-perturbing antibodies, it appeared that complete abolition of cell spreading and migration could be achieved only by blocking multiple integrins of the (beta)1 and (beta)3 families, suggesting possible functional compensations between different integrins. In addition, these studies provided evidence for functional partitioning of integrins in cell adhesion and migration. While spreading was essentially mediated by (alpha)v(beta)1 and (alpha)8(beta)1, migration involved primarily (alpha)4(beta)1, (alpha)v(beta)3 and (alpha)8(beta)1 and, more indirectly, (alpha)3(beta)1. (alpha)5(beta)1 and the (beta)8 integrin were not found to play any major role in either adhesion or migration. Finally, consistent with the results of inhibition experiments, recruitment of (alpha)4(beta)1 and (alpha)v(beta)3, individually or in combination using antibodies or recombinant VCAM-1 and PECAM-1 molecules as a substratum, was required for migration but was not sufficient to produce migration of the cell population as efficiently as with fibronectin. In conclusion, our study indicates that neural crest cells express a multiplicity of fibronectin-binding integrins and suggests that dispersion of the cell population requires cooperation between distinct integrins regulating different events of cell adhesion, locomotion and, possibly, proliferation and survival.