Canonical Wnt signaling is required endothelial cell-autonomously for angiogenesis. (A) Diagram of a zebrafish embryo with the red box highlighting the region shown in B-F,H-J. (B) In situ hybridization of the trunk of a 26 hpf wild-type zebrafish embryo probed for wnt2bb, showing expression in the axial vessels (dorsal aorta, arrow; posterior cardinal vein, arrowhead). Lateral view, anterior towards the left. (C-F) Confocal images of trunk vessels in 26 hpf Tg(fli-EGFP)y1 wild-type zebrafish injected with either 5 ng control MO (C), 5 ng wnt2bb MO (D), 5 ng rspo1 MO (E) or 2.5 ng wnt2bb MO + 2.5 ng rspo1 MO (F). (G) Quantitation of the intersegmental vessel (ISV) phenotypes of morpholino-injected wild-type 26 hpf Tg(fli-EGFP)y1 zebrafish. (H-J) Confocal images of trunk vessels in 26 hpf wild-type Tg(flk-mCherry) zebrafish (red) injected with DNA for either control flk:EGFP (H) or flk:axin-EGFP (I,J) expression constructs (green), showing defects in sprouting (J) or growth (I) of ISV expressing the axin-EGFP fusion protein. (K) Quantitation of the intersegmental vessel (ISV) phenotypes of endothelium expressing flk:axin-EGFP or control flk:EGFP expression constructs. In G and K bars show the percentages of ISV that have failed to sprout (blue), ISV that have grown only up to the horizontal myoseptum half-way up the trunk (red) and ISV that have grown all the way to the dorsal trunk to form the DLAV (yellow). The number of segments counted is shown above each bar. Scale bars: 50 μm in B-F,H-J.