Fig. 1

Gata6 ^H2B-Venus targeting strategy and reporter expression during endoderm differentiation of ES cells. a The wild-type Gata6 and targeted Gata6 ^H2B-Venus alleles. Exon 1–7 (E1-7), non-coding regions (white boxes), open reading frame (black boxes), Engrailed 2 (En2), Neomycin cassette (NEO), single polyadenylation sequences (pA), rox sites (grey triangles), loxP sites (black triangles), FRT site (white triangle), start codon (ATG), stop codon (TAG). Asterisk indicates that the ATG is one of two translational start sites located within Exon 2. b Gata6 ^H2B-Venus/+ ES cells do not express Venus while maintained in the pluripotent state in media containing serum and LIF. c Embryoid body formation from Gata6 ^H2B-Venus/+ ES cells. Expression of Venus occurs on the surface of embryoid bodies by Day 8. Cryosections stained with Phalloidin showed expression of Venus both on the surface and inside the embryoid bodies. Scale bar is 100 μm. d Growth factor treatment using Activin A directed Gata6 ^H2B-Venus/+ ES cell differentiation into the endoderm lineage resulting in upregulation of Venus by Day 5. e Overexpression of a single copy of GATA4-mCherry using the Tet-ON system in Gata6 ^H2B-Venus/+ ;ColA1 ^{TetO-Gata4-mCherry/+} ;R26 ^M2rtTA/+ ES cells. Upon treatment with Doxycycline (DOX) for 48 h, cells were driven to differentiate towards the extraembryonic endoderm lineage resulting in activation of Venus expression. Differential interference contrast (DIC)