Fig. 3. Mbd3 is required for epiblast maturation and extra-embryonic development. (A) Wild-type (top panels) and homozygous null (bottom panels) embryos at 5.5 dpc were stained for Oct4 (green) and 7 integrin (red). (B) Whole-mount in situ hybridisation of heterozygous (top) and homozygous null (bottom) embryos at 5.5 dpc for Cdx2 (left-hand panels), and Mash2 (right-hand panels). (C) Heterozygous (top panels) and homozygous null (bottom panels) embryos at 5.5 dpc were stained for Gata4 (red) and Oct4 (green). A close-up of the homozygous null embryo is shown in the inset at the bottom of each panel to illustrate co-expression of Oct4 and Gata4 in a subset of cells (arrow), in addition to Oct4 or Gata4 single-positive cells (asterisk and arrowhead, respectively). (D) Chimeric embryos made with wild-type ES cells expressing GFP (green) and embryos obtained from Mbd3 heterozygote intercrosses. The genotype of the embryo used for each chimera was determined by Mbd3 staining (red) in GFP-negative (i.e. host-derived) cells.