Adenosine signaling is required for EHT in zebrafish. (A and B) Still images from in vivo time-lapse confocal imaging of Tg(flk1:GFP) embryos between 32 and 48 hpf. Embryos are either uninjected (A) or injected with A_2b MO (B). Numbers indicate recording time in hours and minutes. Arrows in A point to three aorta cells undergoing successful EHT. Cells 2a and 2b are the daughter cells of cell 2. The two dorsal aorta cells 1′ and 2′ in B initiate EHT and burst into pieces (marked by circles). (C) Quantification of the number of flk1:GFP⁺ cells per somite undergoing burst during the 16-h time-lapse period. The results are presented as mean ± SE (Student’s t test: **, P < 0.01; n = 6–8 embryos per group). (D) Tg(hsp70:runx1) embryos stained for runx1 without heat shock (HS) induction or after heat shock induction. (E–H) Expression of cmyb at 36 hpf in Tg(hsp70:runx1) embryos. Embryos were either uninjected (E and F) or injected with A_2b MO (G and H). Embryos either received no heat shock treatment (E and G) or received heat shock induction (F and H). The numbers are combined from multiple experiments. (I) Quantification of the experiments in G and H. The results are presented as the mean percentage of embryos with rescued cmyb staining as in H ± SE (Student’s t test: *, P < 0.05; n = 3 experiments, around 20 embryos per experiment). Bars: (A and B) 50 µm; (D) 250 µm; (E–H) 100 µm.