Role of mechano-dependent cell movements in the establishment of spatial organization of axial rudiments in Xenopus laevis embryos

Trajectories of individual cell movements and patterns of differentiation in the axial rudiments in suprablastoporal areas (SBA) in whole embryos of Xenopus laevis artificially stretched in the transverse direction up to 120–200% from the initial length at the early gastrula stage were mapped. We observed the impairment of anisotropic cell movements of longitudinal stretching and latero-medial convergence inherent for SBA. Axial rudiments occurred in all cases, but their location was completely impaired and dramatically different from the normal topology for moderate (120–140%) stretching. Stronger stretching caused a partial ordering of the whole axial complex and its reorientation toward stretching. We concluded that induction factors determine short-range order in their arrangement in SBA, whereas anisotropic cell movements in any direction are needed for long-range order. Moderate transverse stretching destroys normally oriented anisotropy, but it is not enough for establishment of the anisotropy oriented perpendicular to the normal. This explains the disorder at light stretching. The main conclusion of this study is that anisotropic tensions of embryonic tissues play role of long-range order parameters of cell differentiation.