Adenosine signaling regulates hemogenic vascular endothelium. (A–C′) Confocal imaging of Tg(sclβ:d2eGFP; flk1:mcherry) embryos at 30 hpf. Control embryos (A and A′), embryos injected with A_2b MO (B and B′), and embryos treated with 10 µM BAY 60-6583 (C and C′) are shown. Arrowheads indicate the hemogenic endothelial cells marked by sclβ:GFP⁺. Dashed lines mark the somite boundaries. (D–G) Expression of runx1/cmyb in the AGM of control embryos (D), embryos injected with A_2b MO (E), and scl mRNA–injected (F) and A_2b MO– and scl mRNA–co-injected embryos (G). The numbers are combined from multiple experiments. (H) Summary of the number of sclβ:GFP⁺ hemogenic endothelial cells per somite. The results are presented as mean ± SE (Student’s t test: *, P < 0.05; **, P < 0.01; n = 5–8 per group). (I) Quantification of the experiments in E and G. The results are presented as the mean percentage of embryos with runx1/cmyb staining as in G ± SE (Student’s t test: *, P < 0.05; n = 3 experiments, around 20 embryos per experiment). Bars, 100 µm.