Fig. 1. Whole-mount in situ hybridization analysis showing Sox17 (left panels) and Sox18 (right panels) expression in developing blood vessels of mouse organogenic embryos. (A,B) Embryos at early somite stage [embryonic day 8.5 (E8.5)]; whole embryos (A) and histological sections (B). Arrowheads indicate small blood vessels around hindgut. (C-H) Embryos at early organogenic stage (E9.5); whole embryo (C,D) and histological sections (E-H). (I-K) Embryos at E11.5; whole embryo (I) and histological sections (J,K). Sox18-positive endothelial cells appear to be more widely distributed in the smaller microvasculatures (arrowheads in D,E,K). The red broken arrows (A,C,I) and boxed area (C,E,G,J) indicate the planes of sections and the magnified area in the designated panel, respectively. da, dorsal aorta; fg, foregut; gb, presumptive gallbladder; hg, hindgut; isv, intersomitic vessels; nt, neural tube. Bars, 50 µm.