Cell-autonomous and inductive processes among three embryonic domains control dorsal-ventral and anterior-posterior development of Xenopus laevis
This review aims to propose an integrated model for dorsal-ventral and anterior-posterior development of Xenopus. Fertilized Xenopus eggs contain two determinants, a vegetal half endomesodermal determinant and a vegetal pole dorsal determinant (DD). The organizer forms in the specific intersection of the determinants, in a cell-autonomous manner. At late blastula, different combinations of the determinants form three embryonic domains, the competent animal domain, the organizer domain, and the entire vegetal half domain. These three domains cooperatively form dorsal-ventral and anterior-posterior axes: the organizer domain secrets dorsal inducing signals which induce or ‘activate’ the competent animal domain to form anterior-most neural tissues. The vegetal non-dorsal-marginal domain secrets posteriorizing signals, which ‘transform’ the anterior properties of the neural tissue to posterior properties.