Cell locomotion and contact guidance in amphibian gastrulation

Abstract

Presumptive mesodermal cells in amphibian gastrulae migrate from the blastopore toward the animal pole by using the inner surface of the ectodermal layer as their substratum. During migration, the mesodermal cells form lamellipodia and filopodia predominantly in a direction toward the animal pole. There is a network of the extracellular fibrils on the inner surface of the ectodermal layer. The fibrils seem to serve as an adequate substratum for attachment of the filopodia and locomotion of the mesodermal cells. A significant alignment of the fibril network along the blastopore-animal pole axis suggests a hypothesis that it directs morphogenetic cell movements by contact guidance in combination with contact inhibition of movement. New culture conditions allow the gastrula mesodermal cells to move actively in vitro with a similar cell shape and at a similar rate as in vivo. Such culture conditions enabled an in vitro experiment to test the hypothesis of contact guidance. Explanted ectodermal layers deposit the fibril network on the surface of a cover slip. Dissociated gastrula mesodermal cells seeded on such a conditioned surface attach to the surface and move about actively. A computer analysis of the time-lapse films shows that the cell trails are significantly aligned along the blastopore-animal pole axis of the ectodermal layer that conditioned the surface. The deposited fibril network shows the alignment along the same axis. There is also a tendency of the mesodermal cells to move in a polarized fashion preferentially toward the animal pole. These results support the hypothesis of contact guidance of mesodermal cell migration in vivo by oriented extracellular fibrils © 1984 by the American Society of Zoologists.