Knockdown of ECSCR2 results in aberrant positioning of migrating angioblasts. (A-G) Dorsal views of the posterior of control MO (cMO)–injected or ecscr morpholino (MO1, MO2) zebrafish embryos of the indicate stages subjected to whole-mount ISH for etsrp. (A-C) 8 som. Angioblasts are detected in apparently normal numbers and position in morpholino-injected embryos. Scale bar represents 200 μm. (D-G) 14 som. cMO-injected embryos show etsrp⁺ angioblasts arriving at the midline () and convergence of the premigratory rows toward the midline, whereas anti-ecscr morphants show a greater gap between angioblast rows and few midline angioblasts. MO2 morphants showed a greater range of morpholino phenotypes, with more severely affected morphants (G) showing an irregular row of angioblasts with occasional angioblasts positioned away from the midline ( in panel G). (H-J) Lateral view of 16-som embryos. cMO-injected embryos and the bulk of MO1- and MO2-injected embryos show a consolidated midline vascular cord³  (H), whereas approximately 20% of MO1 and MO2 morphants (I-J) show increased numbers of premigratory angioblasts lateral and dorsal to the consolidating vascular cord. Results at each embryonic stage are representative of at least 20 embryos from 2 independent injections.