... ectoderm and the embryonic epiblast that plays a role in embryo polarity but without contributing cells to the primitive streak (like the chick MZ), and is this region also defined and maintained by Wnt activity from more remote extra-embryonic tissues? In the chick embryo, an amniote, a region...

...Claudio D. Stern; Karen M. Downs When amniotes appeared during evolution, embryos freed themselves from intracellular nutrition; development slowed, the mid-blastula transition was lost and maternal components became less important for polarity. Extra-embryonic tissues emerged to provide nutrition...

... interaction with factors that determine its DNA target specificity. However, functional evidence linking TRIM28 to specific co-factors is scarce. chatwo , a hypomorphic allele of Trim28 , causes embryonic lethality and defects in convergent extension and morphogenesis of extra-embryonic tissues...

... to a characteristic localized outpocketing of the visceral endoderm at the posterior embryonic/extra-embryonic junction, accompanied by a dramatic twisting of the epiblast and nascent mesoderm. Chimera analysis reveals that these two defects are attributable to a requirement for Smad1 in the extra-embryonic tissues...