An adenosine analogue regulates definitive hematopoiesis. (A–C′) In situ hybridization of runx1/cmyb at 36 hpf. Representative images of wild-type embryos treated with DMSO (A and A′), adenosine receptor agonist NECA (20 µM; B and B′), and antagonist (10 µM CGS15943; C and C′). Prime panels depict the AGM region of the embryos in A–C (red arrows). The numbers at the right corner (here and following) indicate embryos with altered HSPC staining over the total number of embryos examined. (D) Bright view of Tg(cmyb:GFP; flk1:mcherry) embryos. The square indicates the live-imaging position. (E–G′) Confocal images of double-transgenic embryos at 36 hpf. The embryos were treated with DMSO (E and E′), NECA (F and F′), or CGS15943 (G and G′). The white arrows point to the double-positive HSPCs in the aorta region. The blue arrowheads point to the multiciliate cells of the pronephros. Dashed lines indicate the somite boundaries. (H) Quantification of the number of HSPCs per somite in Tg(cmyb:GFP; flk1:mcherry) embryos at 36 hpf. The results are presented as mean ± SE (Student’s t test: *, P < 0.05; n = 5–8 per group). Bars, 100 µm.