Abstract
SummaryIn developing amniote embryos, the first epithelial-to-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.
Highlights
The shaping of the early embryo involves the conversion of a single layer of ectodermal cells into a multilayered structure
This accumulation results in the formation of a midline linear structure called the primitive streak, from which the presumptive mesendodermal cells ingress upon undergoing an epithelial-to-mesenchymal transition (EMT)
We previously found that Snail2 (Slug) downregulation prevented migration from the primitive streak in the chick embryo (Nieto et al, 1994), and here we show that Snail2 is sufficient to induce ectopic delamination in otherwise noningressing epiblast cells, confirming that these cells need to be protected from Snail2 expression and subsequent ingression
Summary
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 Snail and Sox factors. We show that the relationship between Sox and Snail is conserved in the mouse embryo and in human cancer cells. Snail-expressing cells ingress at the primitive streak, whereas Sox3-positive cells, which are unable to ingress, ensure the formation of ectodermal derivatives. 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 Sox and Snail transcription factors
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