Snrk-1 gene knockdown analysis in vivo. (A-D) Endothelial cells at 18 hpf and 28 hpf in wild-type (WT) and MO1-injected embryos are visualized by in situ hybridization using a fli antisense RNA probe. (C,D) High-magnification images of the trunk and head, respectively, of WT and MO1-injected embryos from panel B. Reduction of ECs is observed at (A) 18 hpf and (B) 28 hpf in MO1-injected embryos. Red bracket in panel C shows reduction of fli⁺ region composed of DA and PCV, and black asterisk shows that intersomitic vessels (ISVs) are missing at 28 hpf in MO1-injected embryos. (A-C) Lateral views. (D) Dorsal view. etsrp⁺ angioblasts in the head, trunk, and tail at (E-G) 6 som and (H-M) 17 hpf in WT, MO1-, and MO2-injected embryos. White asterisks in panels E through G are included for etsrp⁺ cell comparison across comparable regions in the 3 samples. At 17 hpf, in the head, compare 4 populations of etsrp⁺ angioblasts—of which the most anterior are enclosed in red box. In the trunk, 2 bilateral stripes of etsrp⁺ angioblasts are noticed, of which one stripe is missing in MO1-injected embryo (I, trunk). In the tail, 2 distinct etsrp⁺ angioblast populations merge at the tail tip indicated by the black box, and differences are noticed in their intensities and patterning in MO-injected embryos compared with WT. (K-M) Embryos overstained with etsrp probe. (L,M) Overstained embryos in which etsrp⁺ angioblasts are mispatterned. (N) The percentage of MO1- and MO2-injected embryos with mislocalized angioblasts at 17 hpf; *P < .001 between MO1- or MO2-injected groups compared with UI. (O) The fold change of etsrp transcript levels at 6 som in MO1- and MO2-injected embryos as analyzed by QPCR. Error bars represent SEM.