Snail2 and Zeb2 repress P-cadherin to define embryonic territories in the chick embryo.

Hervé Acloque,Claudio D Stern,M Angela Nieto,Diana Abad,Oscar H Ocaña

doi:10.1242/dev.142562

Abstract

Snail and Zeb transcription factors induce epithelial-to-mesenchymal transition (EMT) in embryonic and adult tissues by direct repression of E-cadherin transcription. The repression of E-cadherin transcription by the EMT inducers Snail1 and Zeb2 plays a fundamental role in defining embryonic territories in the mouse, as E-cadherin needs to be downregulated in the primitive streak and in the epiblast, concomitant with the formation of mesendodermal precursors and the neural plate, respectively. Here, we show that in the chick embryo, E-cadherin is weakly expressed in the epiblast at pre-primitive streak stages where it is substituted for by P-cadherin We also show that Snail2 and Zeb2 repress P-cadherin transcription in the primitive streak and the neural plate, respectively. This indicates that E- and P-cadherin expression patterns evolved differently between chick and mouse. As such, the Snail1/E-cadherin axis described in the early mouse embryo corresponds to Snail2/P-cadherin in the chick, but both Snail factors and Zeb2 fulfil a similar role in chick and mouse in directly repressing ectodermal cadherin genes to contribute to the delamination of mesendodermal precursors at gastrulation and the proper specification of the neural ectoderm during neural induction.

Highlights

During early embryonic development, the embryo progresses from a single layer of epithelial cells to a three-dimensional structure composed of several layers and territories
We show that the chick embryo mostly expresses P-cadherin instead of E-cadherin in the epiblast and that, like E-cadherin in the mouse, P-cadherin is downregulated in the mesoderm and in the induced neural plate while it is maintained in non-neural ectoderm
As Pcadherin expression is complementary to that of Snail and Zeb genes, we performed gain- and loss-of-function experiments to evaluate whether these epithelial repressors are responsible for the downregulation of P-cadherin during primitive streak stages, when Snail2 is expressed in the streak and in the ingressing mesendoderm, and at neurulation stages, when Zeb2/Sip1 is expressed in the early neural plate

Summary

Introduction

The embryo progresses from a single layer of epithelial cells (the epiblast) to a three-dimensional structure composed of several layers and territories. Like Snail mutants, Zeb2 mutant embryos maintain E-cadherin expression in the corresponding territories: the neural plate and the presumptive neural crest.

Results

Conclusion