Phosphotyrosine signalling as a regulator of neural crest cell adhesion and motility.

We demonstrate that neural crest cell-cell adhesion, cell-substrate adhesion, and ultimately cell motility, are highly dependent on the balanced action of tyrosine kinases and tyrosine phosphatases. Neural crest cell migration on fibronectin is diminished in the presence of the tyrosine phosphatase inhibitor vanadate or tyrosine kinase inhibitor herbimycin A, while cadherin-rich cell-cell adhesions are significantly increased. In contrast, cells treated with the kinase inhibitor genistein have decreased motility, rearrange rapidly and reversibly into a pavement-like monolayer, but have no increase in cadherin interactions. Genistein-sensitive tyrosine kinases may therefore abrogate a latent sensitivity of neural crest cells to contact-mediated inhibition of movement. Furthermore, we show that the activity of herbimycin A-sensitive kinases is necessary for focal adhesion formation in these cells. Moreover, the size and distribution of these adhesions are acutely sensitive to the actions of tyrosine phosphatases and genistein-sensitive kinases. We propose that in migrating neural crest cells there is a balance in phosphotyrosine signalling which minimises both cell-cell adhesion and contact inhibition of movement, while enhancing dynamic cell-substrate interactions and thus the conditions for motility.