“…b Because Cdx2-null mutants die prior to gastrulation due to defects in trophoblast development(Chawengsaksophak et al, 2004), analysis of PGCs, anteroposterior axis, hindgut, and allantois occurred in tetraploid-rescued mutants with wild-type trophectoderm and Cdx2-null inner cell mass, which contributes to future epiblast,(Chawengsaksophak et al, 2004) or in Sox2-Cre transgenic mice that conditionally knock out Cdx2 in the epiblast only(Bialecka et al, 2012). Abbreviations: Al, allantois; A-P, anteroposterior; AP, alkaline phosphatase; EB, early (allantoic) bud; HF, headfold; Hg, hindgut; IF, immunofluorescence; LB, late (allantoic) bud; LS, late streak; NP, neural plate; OB, no (allantoic) bud; s, somites.…”