BASIC FIBROBLAST GROWTH-FACTOR PROMOTES ADHESIVE INTERACTIONS OF NEUROEPITHELIAL CELLS FROM CHICK NEURAL-TUBE WITH EXTRACELLULAR-MATRIX PROTEINS IN CULTURE

Fibroblast growth factors have been increasingly assigned mitogenic an d trophic roles in embryonic and postnatal development of the nervous system. Little is known, however, of their functional roles in early e mbryonic neural development at the neural tube stage. We have examined the effect of basic fibroblast growth factor (bFGF) on the adhesive b ehavior in culture of dissociated brachio-thoracic neural tube cells f rom 26- to 30-somite stage chick embryos. Cells plated on collagen-coa ted substratum at a low density attach to the substratum but show poor cell spreading. Addition of bFGF markedly promotes cell spreading, yi elding an epithelial morphology. This effect becomes discernible 6-8 h ours after cell plating with bFGF and is completed by 24 hours, with h alf-maximal and maximal effects attained at around 0.4 and 10 ng/ml, r espectively. The number of cells remains largely constant up to 24 hou rs, and then cell survival and/or mitogenic effects of bFGF become app arent. The cell spreading effect is abolished by cycloheximide treatme nt, inhibited by the anti-beta(1)-integrin antibody CSAT, and accompan ied by about twofold increases in the expression of beta(1)-integrin a nd vinculin, components of focal adhesion complexes. Cells cultured wi th bFGF for 24 hours exhibit enhanced cell attachment and cell spreadi ng with little time lag following cell plating. In earlier embryonic s tages, developmentally less mature cells depend much more on bFGF for their cell spreading and survival, while in later stages the cell spre ading response to bFGF becomes undetectable as neural tube develops to spinal cord. The cell spreading effect of bFGF is realized on specifi c extracellular matrix proteins including laminin, fibronectin and col lagen, but not on vitronectin, arg-gly-asp peptide (PepTite-2000), pol y-L-ornithine or others. These results suggest that, in an early stage of neural tube development, bFGF is involved in the developmental reg ulation of adhesive interactions between neuroepithelial cells and the extracellular matrix, thereby controlling their proliferation, migrat ion and differentiation.