Adenosine mediates HSPC development by regulating CXCL8. (A) BAY 60-6583 induces CXCL8 secretion in HAECs (Student’s t test: *, P < 0.05; n = 3). (B) Relative mRNA expression of cxcl8, runx1, and fli1 in FACS-sorted flk1:GFP⁺ cells in A_2b MO–injected compared with control MO–injected embryos (Student’s t test: **, P < 0.01; n = 3). (C–H) Expression of runx1/cmyb at 36 hpf. Control embryos (C) and embryos injected with cxcl8 MO (D), injected with cxcl8 mRNA (E), co-injected with cxcl8 MO and cxcl8 mRNA (F), injected with A_2b MO (G), and co-injected with A_2b MO and cxcl8 mRNA (H) are shown. (I and J) Expression of runx1/cmyb in the CHT of control embryos or embryos injected with cxcl8 MO. (K and L) Control or cxcl8 MO–injected embryos stained for dorsal aorta (ephrinB2). (M) A CXCL8 TALEN mutation leads to the deletion of two amino acids (in yellow) in the conserved CXC domain. (N and O) Expression of cmyb at 36 hpf in control sibling embryos and CXCL8 mutant embryos. htz, heterozygous; hom, homozygous. (P–Q′) Confocal imaging of Tg(sclβ:d2eGFP; flk1:mcherry) embryos at 30 hpf. Control embryos (P and P′) and embryos injected with cxcl8 MO (Q and Q′) are shown. Arrowheads indicate the hemogenic endothelial cells marked by sclβ:GFP⁺. Dashed lines mark the somite boundaries. (R) Summary of the number of sclβ:GFP⁺ hemogenic endothelial cells per somite (Student’s t test: **, P < 0.01; n = 5 per group). The results are presented as mean ± SE. Bars, 100 µm.