Zebrafish ptc1;ptc2 double mutants fail to establish circulation and exhibit multiple endothelial defects and defective angioblast migration. (A-B) ptc1;ptc2 mutant (B) embryos at 27 hpf showed somitic flattening (white arrowhead) and loss of lens (asterisk). ptc1;ptc2 embryos showed noncirculating primitive erythrocytes in the posterior intermediate cell mass (red arrowhead). (C-D) cdh5 expression in ptc1;ptc2 mutants (D) revealed defective formation of the common cardinal vein (CCV; black arrowheads) and PCV (white arrowheads) compared with wild-type (C). (E-F) Confocal image of trunk vasculature in Tg(fli1a:EGFP)y1;Tg(gata1:dsred)sd2/+ (E) and Tg(gata1:dsred)sd2/+;ptc1;ptc2 (F) embryos; anterior to the left, posterior right. The primary vasculature formed normally in Tg(fli1a:EGFP)y1;Tg(gata1:dsred)sd2/+ embryos, and circulation commenced normally (yellow arrowhead; supplemental Video 1), whereas Tg(fli1a:EGFP)y1;Tg(gata1:dsred)sd2/+;ptc1;ptc2 embryos had disorganized vasculature, axial vessels were noncontinuous along their anteroposterior axis (asterisks), and embryos lacked circulation (yellow arrowhead; supplemental Video 2). (G-L) Confocal images using a Tg(fli1a:EGFP)y1/+ background to visualize migrating angioblasts in indicated genetic backgrounds. Dorsal views are shown. (G-I) Normal angioblast migration in Tg(fli1a:EGFP)y1/+ embryos. (J-L) Fewer angioblasts migrated to the midline in Tg(fli1a:EGFP)y1/+;ptc1;ptc2 embryos and formed a discontinuous endothelial cord by 18 somites (supplemental Video 3; white arrowheads). Angioblasts were present in more lateral positions (supplemental Video 4; L yellow arrowheads) than in controls at the corresponding stage (I yellow arrowheads).