Fig. 1

The GFP reporter protein faithfully recapitulates the transcriptional activation of the BRE::gfp transgene. In situ hybridisation for gfp mRNA (red) and direct GFP fluorescence (green) on cryosections through the cardinal vein (a–d) and the ventricular trabeculae (e–g) at E11.5. DAPI is used to stain nuclei. The boxed area in (a) is enlarged in panels (b–d). The corresponding low magnification view of the trabeculae in the ventricle is not provided because of insufficient intensity of the ISH signal. White arrowheads indicate ECs double positive for gfp mRNA and direct GFP fluorescence. The red and green arrows depict ECs only positive for gfp mRNA or GFP fluorescence respectively. Scale bars: 100 μm (a); 50 μm (b–d); 10 μm (e–g)