Endothelial development is severely disrupted in Scl-depleted embryos. (A-C) Flat-mount embryos; anterior, left (A-B, 18 × magnification; C, 21 × magnification). (D-H) Whole-mount embryos; lateral view; close-up of trunk/tail region; anterior, left. (I-M) Wholemount embryos (45 × magnification); lateral view; close-up of trunk region; anterior, left. Numbers of embryos represented in gray. At 10 somites (14 hpf), flk1 and flt4 expression in the ALM and PLM was severely reduced in morphant embryos (A, B). At 15 somites (16.5 hpf), fli1 expression was significantly reduced in morphants (C), and the line of DA precursors forming at the midline was not as distinct as in wt (C, arrows). In 26-hpf morphants, fli1 and tie1 expression was severely reduced in the trunk region and lost in ISVs (D, E, arrows). Flk1 expression in the DA was lost, with remaining expression ventrally and laterally (F). At 26 hpf, expression of flt4 and tie2, mainly restricted to the PCV, was not significantly down-regulated in morphant embryos (G, H). (I-M) DA-but not PCV-specific gene expression was lost in Scl-depleted embryos. Expression of artery-specific genes hrT (I), deltaC (J), notch5 (K), and ephrinB2a (L) was entirely lost in morphants. EphB4 expression in the PCV, however, was not depleted (M).