Snrk-1 functions in A/V specification. (A,B) grl in situ hybridization of 18 hpf WT and MO2-injected embryos, respectively. ephrin-B2a in situ hybridization of 26 hpf (C) WT, (D) notch2-ICD–injected, or (E) notch2-ICD + snrk-1 MO1–injected embryos. flt-4 in situ hybridization of 30 hpf (F) WT, (G) notch2-ICD–injected, and (H) notch2-ICD + snrk-1 MO1–injected embryos. (F-H) White asterisks show flt-4 expression in intersomitic arteries. (C-E) The black brackets indicate the space between the most dorsal stained regions of the embryo to the yolk extension. (D) Note the shrinkage in space in notch2-ICD–injected embryo, indicating an expansion of ephrin-B2a–stained cells. fli in situ hybridization of 26 to 28 hpf (I) WT, (J) MO1-injected, and (K) MO1 + hsnrk-1 RNA–injected embryos. (J,M) MO1-injected embryos missing ISVs compared with (I,L) WT or (K,N) MO1 + hsnrk-1–coinjected embryos. (O) Graphic representation of the number of embryos displaying faint or absent ISVs in the trunk region of samples in panels I through K. *P < .001 across MO1 and MO1 + hsnrk-1 group. (P) A model placing Snrk-1 parallel to Notch in A/V specification. The dotted line indicates that definitive evidence is needed to show that snrk-1 is downstream of notch. Images in panels C through H were taken using an Observer Z1 inverted microscope (Carl Zeiss, Thornwood, NY) with 10× objective and 10× eyepiece. The image acquisition software used was AxioVision Rel4.6 (Carl Zeiss, Oberkochen, Germany); images were corrected for brightness and contrast in Photoshop 7.0.