Expression of Anxa3 in the endothelial lineage is conserved across multiple species.(A,B) Whole-mount in situ hybridization analysis for vascular endothelial growth factor receptor 2 (VegfR2) and Anxa3b expression in Danio rerio embryos, 24 hours post fertilization (hpf). Close-up, lateral views of the tail regions are shown. Anxa3b transcripts are restricted to the developing dorsal aorta (DA), whereas VegfR2 is also expressed in the intersomitic vessels (isv). (C-F) Embryonic (E) day 8.25 mouse embryos were assayed for Anxa3 and the vascular marker PlexinD1 by whole-mount in situ hybridization (anterior views). Similar to PlexinD1, Anxa3 is observed in the paired dorsal aortae (da, arrows) and heart (h) region of the embryo. Anxa3 is absent in the extra-embryonic vessels of the yolk sac (ys) that are marked by PlexinD1 expression. This is highlighted in close-up views of ys from PlexinD1 and Anxa3 stained E8.25 embryos (D,F). (G,H) E9.25 heterozygous (^+/-) and homozygous (^-/-) VegfR2 embryos analyzed for Anxa3 expression by in situ hybridization (lateral views). Anxa3 is detected in the dorsal aorta (DA), intersomitic vessels (isv) and heart (h) region of VegfR2^+/- embryos, while VegfR2^-/- null embryos, which lack all blood vessels, displayed no observable vascular staining of Anxa3 (background staining is detected in the head and just outside the heart region).