J. Cell Set. 86, 109-118 (1986) 109 Printed in Great Britain © The Company of Biologists Limited 1986 PRESUMPTIVE MESODERM CELLS FROM XENOPUS LAEVIS GASTRULAE ATTACH TO AND MIGRATE ON SUBSTRATA COATED WITH FIBRONECTIN OR LAMININ NORIO NAKATSUJI Division ofDevelopmental Biology, Meiji Institute of Health Science, 540 Naruda, Odawara 250, Japan SUMMARY 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. INTRODUCTION During gastrulation movements in amphibian embryos the presumptive meso- dermal cells migrate from the blastopore towards the animal pole region along the inner surface of the ectodermal layer. Migrating cells extend lamellipodia and filopodia, and move preferentially towards the animal pole (Nakatsuji et al. 1982). The filopodia are very frequently attached to the extracellular fibrils that form an anastomosing network on the inner surface of the ectoderm layer. These fibrils appear in late blastulae and increase in number through gastrulation in all species of urodeles and anurans studied to date (Nakatsuji & Johnson, 19836; Darribere et al. 1985), but they are much reduced in number or absent altogether in hybrid embryos that cease to develop at early gastrula stages (Nakatsuji & Johnson, 19846; Delarue etal. 1985). Key words: gastrulation,fibronectin,laminin, cell adhesion, cell migration, amphibian, Xenopus.