Abstract
In developing amniote embryos, the first epithelialto- mesenchymal transition (EMT) occurs at gastrulation, when a subset of epiblast cells moves to the primitive streak and undergoes EMT to internalize and generate the mesoderm and the endoderm. We show that in the chick embryo this decision to internalize is mediated by reciprocal transcriptional repression of Snail2 and Sox3 factors. We also show that the relationship between Sox3 and Snail is conserved in the mouse embryo and in human cancer cells. In the embryo, Snail-expressing cells ingress at the primitive streak, whereas Sox3-positive cells, which are unable to ingress, ensure the formation of ectodermal derivatives. Thus, the subdivision of the early embryo into the two main territories, ectodermal and mesendodermal, is regulated by changes in cell behavior mediated by the antagonistic relationship between Sox3 and Snail transcription factors
Contents
1. INTRODUCTION
2. RESULTS
2.1. Snail2 Induces Ectopic Cell Delamination in the Ectoderm of the Early Chick Gastrula
2.2. Snail2 and Sox3 Expression Domains Delineate Ingressing versus Noningressing Embryonic Cell Populations
2.3. Snail2 and Sox3 Are Reciprocal Direct Transcriptional Repressors
2.4. Snail2 Represses Ectodermal Markers without Inducing Mesodermal Fate
2.5. Conservation of the Sox3/Snail Antagonistic Relationship in Mouse Embryos
2.6. Conservation of the Sox3/Snail Antagonistic Relationship in Human Cancer Cells
3. DISCUSSION
4. EXPERIMENTAL PROCEDURES