Fig. 2

scube1 and scube3 morpholinos enhance the phenotype of you^ty97 mutant embryos. The wildtype pattern of slow MyHC (A) is disrupted in the posterior tail region of you^ty97 homozygotes (B) (arrow). The pattern of slow MyHC is not visibly affected when scube1MO (C) scube3MO (E) or both scube1MO+scube3MO (G) are injected into wildtype embryos. (D) scube1MO injected into you^ty97 homozygotes enhanced the you^ty97 phenotype. Slow MyHC expression is disrupted after you^ty97 homozygotes in this region (compare B to D). Bracket highlights the region in you^ty97+scube1MO embryos lacking slow MyHC fibers. An arrow indicates the somitic region where slow MyHC expression resembles you^ty97 mutants. (F) scube3MO injected into you^ty97 homozygotes also enhanced the you^ty97 mutant phenotype. Slow MyHC is disrupted after <8–10 somites, all remaining somites completely lack slow MyHC expression. Bracket highlights the somitic region in you^ty97+scube3MO embryos devoid of slow MyHC staining. (H) Injection of scube1MO+scube3MO together into you^ty97 mutant embryos essentially eliminates slow MyHC staining. Arrows highlight the few remaining slow MyHC positive fibers remaining in you^ty97+scube1MO+scube3MO embryos (H). Scube triple MO injection into wildtype embryos faithfully reproduces the phenotype seen in you^ty97+scube1MO+scube3MO (H and data not shown). All embryos<30 hpf. F59 monoclonal antibody labels slow MyHC positive muscle fibers, Alexa 488-conjugated donkey anti-mouse secondary. (I) Slow MyHC positive muscle fibers were counted in anterior (1–6 somites), middle (7–15 somites) and posterior (16–30) somites of wildtype, you^ty97 homozygous mutants, you^ty97+scube1MO embryos, you^ty97+scube3MO embryos, you^ty97+scube1MO+ scube3MO embryos, and scube triple MO embryos (scube1MO+scube2MO+scube3MO). Statistical analysis demonstrated the phenotypic enhancement of the you^ty97 mutant phenotype seen following MO injection is significant. The dramatic loss of slow MyHC positive muscle fibers seen following scube1MO+scube3MO injection into you^ty97 homozygotes was equivalent to the loss of slow MyHC positive muscle fibers seen following scube triple MO injection into wildtype embryos (l1-3). *ANOVA F(5,137)=200.11, p<0.001. **ANOVA F(5,137)=266.10, p<0.001. ***ANOVA F(5,137)=391.35, p<0.001. Within each somite region, bars with different letters are statistically significant from one another.