Fig. 4. Expression of NRP1/TIE2 at later developmental stages. Sections through an E10 quail embryo. (A-C) Sections through connective tissue (A), skeletal muscle (B) and lung (C), double-labeled with NRP1 (brown) and TIE2 (blue) antisense riboprobes. Arteries (arrows), surrounded by a thick wall, are NRP1 positive but show weak TIE2 expression. Veins express TIE2 but not NRP1. Parallel-running streams of capillaries expressing NRP1 or TIE2 can be observed (A,B, arrowheads). (D-F) Triple-labeling of a section through the aorta (Ao) and lymphatic thoracic duct (Th) with the indicated markers. (D) Bright-field view, NRP1 is expressed in EC of the aorta and smaller vessel branching from it (arrow). (E) Dark-field view ; FITC-
-SMA staining shows a thick coat of positive cells surrounding the branching NRP1-positive vessel. (F) Dark-field view ; Texas Red-labeled QH1-positive EC of the lymphatic thoracic duct are NRP1 negative. (G-I) Section through the myocardium, treated with the same markers. All NRP1-positive arteries (arrows) are surrounded by -SMA+ cells, while NRP1-negative vessels (asterisks) are also -SMA negative. QH1 staining (I) shows the corresponding NRP1-positive arterial, and NRP1-negative venous, EC. Bars, (A) 90 µm; (B and C) 180 µm; (D-F) 95 µm; (G-I) 30 µm.
