Trophectoderm Defect in Atrxnull Embryos
(A) 8.5 dpc embryos were dissected from surrounding decidual tissue and observed in whole mount. The genotype of each (indicated above) was determined by PCR using DNA extracted from whole embryos after photography. In the left image, the wild-type female (three-somite stage, left) is surrounded by trophoblast (t) while the trophoblast component surrounding the Atrxnull males (at headfold/presomite [middle] and two-somite stages [right], respectively) is severely depleted. In the right image, the trophoblast has been dissected away from the embryonic region of the wild-type embryo, to reveal the small, abnormally shaped ectoplacental cone (epc) of the mutant littermates.
(B) WMISH to detect expression of Pl-1 (a marker of TGCs) at the implantation sites in vacated deciduas that had contained 8.5 dpc wild-type (Atrx WT/WT) or Atrxnull (Atrx Δ18Δneo/Y) embryos. The genotype was determined by PCR using DNA extracted from whole embryos. TGCs are stained with Pl-1.
(C) Paraffin sections of wild-type or Atrxnull 7.5 dpc embryos (dissected in their deciduas) were stained with an anti-Pl-1 antibody. The presence or absence of Atrx in each embryo was determined by staining adjacent sections with the anti-ATRX antibody (H-300) as in Figure 5 (unpublished data).
(D) Examples of 5-d blastocyst outgrowth cultures. Extensive trophoblast outgrowing from the inner cell mass (icm) was observed in all genotypes. The Atrx genotype and sex of the blastocyst indicated were determined by PCR.