1. Epiblast-specific Eomes deletion blocks gastrulation at the primitive streak stage.
Epiblast-specific Eomes deletion blocks gastrulation at the primitive streak stage. (A-F) Whole-mount in situ hybridisation with molecular markers for the AVE (Hex and Cer1) and posterior epiblast (Wnt3) at E6.5 reveal correct AP axis specification in EomesN/CA; Sox2.Cre mutant embryos. (G-H') At E7.5, Eomes epiblast mutants show a distinct posterior thickening of the epiblast and lack the mesodermal tissue layer as seen in histological sections. (I,J) Posterior (brachyury/Bra) and (K-N) intermediate (Mixl1, Tbx6) streak markers are expressed in Eomes epiblast mutants, but the node fails to form, as revealed by the lack of Shh expression (O,P). (Q,R) Consistent with this, scanning electron microscopy shows lack of a morphological node at the distal tip of mutant embryos (boxed areas indicate the node forming region). (S,T) Instead, the Otx2 expression domain is expanded in Eomes mutants. (U-X) At E7.5 expression of the DE marker Cer1 and the AME marker Foxa2 are lost and (Y,Z) expression of the VE marker AFP fails to become localized to the extra-embryonic region.
Sebastian J. Arnold et al. Development 2008;135:
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