Depletion of LDB2 in endothelial cells results in abnormal endothelial sprouting. (A-C) HUVECs were transfected with control or LDB2 siRNA (80 nM) and 3-D fibrin gel assay was performed. (A) Representative images of sprouting from HUVECs transfected with indicating siRNA (80 nM). Sacale bars: 100 μm (B and C) Quantification of sprouts in a 3-D-fibrin gel assay. Beads coated with HUVECs were seeded and cultured in fibrin gel for 5 days. (n = 4; 15 beads were assayed in each experiment). (D-G) Control morpholino (D and F) or ldb2 morpholino (E and G) was microinjected at one cell stage of zebrafish and pictures were taken at 75 hpf to examine the vessel development. High magnification of control embryo's trunk region (F) showing no abnormality and ldb2 morpholino-injected embryo's trunk region (G) showing aberrant development of intersegmental vesseles. (H-K) Control or ldb2 morpholino of 1.5 ng, 4.5 ng and 5 ng was injected. ldb2 morpholino- injected embryos show disorganized and hyper-branched intersegmental vessels (I-K, red rounds and arrows). Error bars represent mean ± SD. ***P ＜ 0.001. Student’s t test.