(A) Dose–response curve of ccm2l MO-2 injected into embryos from WT. ***P < 0.005, ANOVA. (B) Representative pictures of WT embryos (Upper) with and without ccm2l MO-2 (Lower). The arrow indicates big heart. (C and D) Injection of MO-2 in vtn/ccm2 heterozygous crosses results in heart failure and severe tail/axis defects. Quantitation of phenotypes in C: WT, no phenotype; big heart; HF/axis, heart failure and axis/tail defects; dead, lack of survival. Representative images are shown in D. (E) Genotyping. Chromatograms representing sequence results from vtn heterozygous crosses injected with ccm2l MO-1 (Upper). vtn heterozygous embryos show a double peak (C and A, asterisks), inferring the presence of a vtn (A) and an ortholog WT (C) gene, whereas WT controls show a single peak (C). vtn homozygous embryos were not detected in the surviving embryos in this cross, which may reflect lower survival rates in this group after ccm2l MO injection (Fig. 2D). (F and G) Injections of a cardiac-specific MO (troponinT, tnnt2) in vtn mutants (F) and ccm2l MO-1 injections in silent heart mutant (G) did not phenocopy the ccm2l MO-1 axis defect results (ns, not significant, unpaired t test). Graphs represent data pooled from three independent experiments. The number of embryos scored is in parentheses. Error bars represent SEM. (H) Representative picture of mekk3 mRNA-injected vtn/ccm2 embryos showing more severe tail axis defects and cardiac failure.