Crlr knockdown affects arterial gene expression. Std-MO–injected embryos (control) and crlr-MO1–injected embryos (morphant) were analyzed at 26 hpf for the expression of the indicated arterial and venous markers by ISH. Lateral view of the trunk region is shown (DA, red arrowheads; PCV, white arrowheads). Crlr morphants were characterized by lack of expression of ephrin-B2a (panel B; 13 of 17 embryos examined), DeltaC (panel D; 13 of 19 embryos examined), and notch5 (panel F; 10 of 13 embryos examined). In contrast, venous markers flt4 (H) and ephB4 (J) were expressed in 7 of 10 and in 11 of 12 crlr morphants, respectively. Arterial and venous markers were instead expressed in all the control embryos examined (ranging between 10 and 16 embryos per gene investigated).