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Fig. 2 Knockdown of stap2b causes vascular defects in zebrafish development. (A and B) Bright field images of wild-type and stap2bATG morpholino (1.28 ng)-injected embryos. (C?F) At 30 hpf, ISVs reached DLAV and formed a honeycomb-like structure in the caudal vein plexus (CVP) in wild-type controls and Tg (flk:eGFP) zebrafish (C and E). Compared with the wild-type control (arrowhead in C, arrow in E and G), loss of stap2b caused ISV growth defects (hollow arrowheads in D) and reduced honeycomb-like structure formation in the CVP (arrows in F and H) at 30 hpf and 48 hpf. (I and J) The injection of stap2bATG MO into Tg (fli:eGFPy1;gata1:dsRed) embryos revealed that loss of stap2b caused circulation defects in ISVs at 48 hpf. (K and L) At 72 hpf, stap2bATG morphants exhibited pericardial edema (arrow in L), causing circulation defects. (M) The percentage of completed ISVs decreased by approximately 50% in the stap2bATG morphants (n = 18 in controls and n = 24 in stap2bATG morphants) at 30 hpf. (N) The average length of ISVs in stap2bATG morphants (n = 30, 69.8 ± 6.1 ?m) was shorter than the length in controls (n = 30, 115.9 ± 8.9 ?m) at 24 hpf. (O) Loop formation in CVP was decreased in the stap2bATG morphants (n = 25 in controls and n = 33 in stap2bATG morphants) at 30 hpf. (P) Quantification data revealed that compared with the controls with defects, the stap2b morphants showed 75% more defects in the ISV-DLAV circulation and 18% more defects in aorta-vein circulation (n = 12 in controls and n = 33 in stap2bATG morphants) at 48 hpf. (Q) The percentage of stap2b morphants with pericardial edema was 65% greater than that was 15% in the controls (n = 29 in controls and n = 34 in stap2bATG morphants) at 72 hpf. Data are represented as means ± S.D. ***Refers to p < .001 by an unpaired Student's t-test. Scale bar are 200 ?m for A, B, K, L and 100 ?m for C?J.