Mechanodependent cell movements in the axial rudiments of Xenopus gastrulae

Sandwich explants of the suprablastoporal area of Xenopus early-mid gastrula and same stages of entire embryos were stretched with two needles perpendicular to the direction of natural elongation of the axial rudiments. The changes in the embryonic shape and histological structure were monitored as well as the arrangement of descendants of one of dorsal blastomers labeled with fluorescein-dextran at the 16-cell stage. A substantial fraction of stretched explants reoriented along the applied stretch direction. The arrangement dynamics of fluorescein-dextran-labeled cells and explant shape demonstrate that this is an active response based on convergent intercalation of cells induced by stretching. Stretched gastrulae demonstrated arrested gastrulation, dorsoventral extension of the blastopore, and ventral flow of labeled cells towards the lateral lips of the blastopore, which was also mediated by convergent intercalation and tensotaxis. The obtained data are discussed in terms of the hypothesis of mechanical stress hyper-restoration.