Fig. 4

Dynamic BRE::gfp transcriptional activity in the developing heart. Paraffin embedded hearts are sectioned transversally, unless otherwise specified, and (immuno) stained for the endothelial marker IsolectinB4 and GFP. DAPI is used to stain nuclei. a Overview of an E11.5 heart. b Section of the superior and inferior atrioventricular canal cushions at E11.5. c E11.5 sagittal section of AVC (arrow) and OFT cushions (arrowhead). d E11.5 lateral cushion with GFP-positive endocardial cells (arrow) and myocardium (arrowhead). e At E11.5 the septum primum displays GFP-positive ECs on the endothelial cap (bracket). The atrium is GFP-negative at E11.5 (f) while the ventricular trabeculae (g) have GFP-positive ECs (arrows). h Overview of an E14.5 heart. The tricuspid valve shows GFP-positive cells at the atrial side (arrows) at E14.5 (i) and E16.5 (j). GFP signals (arrows) in the intra-atrial septum at E14.5 (k) and E16.5 (l). Some endocardial cells covering the atrial (m) and ventricular trabeculae (n) are GFP-positive (arrows) at E14.5. Ao: aorta; AVC: atrioventricular canal; iAVC: inferior AVC cushion; sAVC: superior AVC cushion; BV: bicuspid valve; CV: cardinal vein; dOFT: distal outflow tract; IVS: inter-ventricular septum; LA: left atrium; LV: left ventricle; pOFT: proximal outflow tract; RA: right atrium; RV: right ventricle; SP: septum primum; TV: tricuspid valve. Scale bars: 200 μm (a;h); 100 μm (c, i-j); 50 μm (b, d-g, k-n)