Neural crest cell migration: requirements for exogenous fibronectin and high cell density

Cells of the neural crest participate in a major class of cell migratory events during embryonic development. From indirect evidence, it has been suggested that fibronectin (FN) might be involved in these events. We have directly tested the role of FN in neural crest cell adhesion and migration using several in vitro model systems. Avian trunk neural crest cells adhered readily to purified plasma FN substrates and to extracellular matrices containing cellular FN. Their adhesion was inhibited by antibodies to a cell-binding fragment of FN. In contrast, these cells did not adhere to glass, type I collagen, or to bovine serum albumin in the absence of FN. Neural crest cell adhesion to laminin (LN) was significantly less than to FN; however, culturing of crest cells under conditions producing an epithelioid phenotype resulted in cells that could bind equally as well to LN as to FN. The migration of neural crest cells appeared to depend on both the substrate and the extent of cell interactions. Cells migrated substantially more rapidly on FN than on LN or type I collagen substrates; if provided a choice between stripes of FN and glass or LN, cells migrated preferentially on the FN. Migration was inhibited by antibodies against the cell-binding region of FN, and the inhibition could be reversed by a subsequent addition of exogenous FN. However, the migration on FN was random and displayed little persistence of direction unless cells were at high densities that permitted frequent contacts. The in vitro rate of migration of cells on FN-containing matrices was 50 microns/h, similar to their migration rates along the narrow regions of FN-containing extracellular matrix in migratory pathways in vivo. These results indicate that FN is important for neural crest cell adhesion and migration and that the high cell densities of neural crest cells in the transient, narrow migratory pathways found in the embryo are necessary for effective directional migration.