Fig. 8

Injection of smyd1b^wt but not myosin-interaction-site-absent smyd1b^278del mRNA restored fractional shortening, sarcomere organization and cardiomyocyte proliferation. Injection of smyd1b^wt or HMT-deficient smyd1b^Y247F mRNA but not smyd1b^278del or LacZ mRNA restored fractional shortening. (A) (n = 24 per condition, N = 4) and Z-disc length (C) (n = 200 per condition, N = 4) at 96 hpf. Data were analyzed by ANOVA with Bonferroni multiple comparisons (α = 0.05). The difference between groups a and b was significant (p < 0.001). Similar ventricular sarcomere lengths (D) were detected in all groups (n = 200 per condition, N = 4). ANOVA indicated no significant difference among treatments (p = 0.49). (B) Striated Z-discs were detected by α-actinin immunofluorescence on sarcomeres in the ventricle of WT (a), smyd1b^Y247F (e) or smyd1b^wt (f) mRNA-injected VCAP1X2 mutant hearts while a dotted pattern on Z-discs was observed in ventricles of VCAP1X2 mutant (b), LacZ (c) or smyd1b^278del mRNA (d)-injected mutant hearts. Enlarged areas are indicated by white dashed rectangles. Nuclei were stained by DAPI. Significantly reduced cardiomyocyte number (E) or percentage of PCNA⁺ cardiomyocytes (F) was detected in ventricles of smyd1b^278del mRNA-injected or un-injected (Un-inj) VCAP1X2 mutant hearts compared to smyd1b^wt mRNA-injected or WT embryos at 96 hpf (n = 15, N = 3). Data were analyzed by ANOVA with Bonferroni multiple comparisons. Treatments that are not statistically different (α = 0.05) from each other are labeled with the same letter. Error bars indicate standard error.