During amphibian gastrulation, presumptive mesoderm cells migrate from the blastopore towards the animal pole along the inner surface of the ectodermal layer. Their natural substratum is a network of anastomosing extracellular matrix fibrils, which contains fibronectin and laminin, as shown by immunostaining. If the fibril network is transferred onto a coverslip from the ectodermal layer, dissociated mesodermal cells readily attach to such conditioned surfaces and show active migration in a medium of high pH and low calcium ion concentration. In the present study, the surface of tissue culture dishes was coated with fibronectin, laminin, collagen type IV or heparan sulphate, to examine the effects on cell attachment and movement. The presumptive mesoderm cells from Xenopus laevis gastrulae showed rapid adhesion and active movement on the fibronectin- or laminin-coated surfaces. Cell adhesion was stronger and the mean rate of movement was higher on the fibronectin-coated surface than on the laminin-coated surface. The dissociated ectodermal cells did not attach to the fibronectin- or laminin-coated surfaces. The mesodermal cells did not attach to the collagen-, or heparan sulphate-coated surfaces, showing that these components of the basement membrane cannot serve as an adequate substratum for the mesoderm cells, at least by themselves.

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