Fig. 7

Expression of Venus yellow fluorescence at allantoic bud and headfold stages. a Wholemount immunofluorescence for GATA6 on Gata6 ^H2B-Venus/+ embryos at late bud (LB, E7.5) and early headfold (EHF, E7.75) stages. Venus is expressed in the surface endoderm and headfold. Dashed lines demarcate the border between exVE and emVE. Higher magnification views show low-level mosaic Venus expression in the exVE in the boxed regions. b Immunofluorescence for BRACHYURY (red) on Gata6 ^H2B-Venus/+ embryos at early bud (EB, E7.5) stage. Expression of Venus is observed in lateral and anterior mesoderm and endoderm and is distinct from expression of BRACHYURY. Sections through the extraembryonic region (B’, top row) and embryonic region (B”, bottom row) are indicated by dashed lines on the schematic diagram to the right. A close-up of the region within the dashed white box shows expression of Venus in the emVE and nascent mesoderm (meso), but not in the Epi. Three embryonic tissue layers (emVE, meso, epi) are delineated by dashed yellow lines. Non-nuclear red fluorescent signal that appears apically on the VE is thought to be non-specific binding of the GATA6 antibody to the surface of the extraembyonic tissue