(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.