FIGURE 1

FIGURE 1

Heart of stone (hos) exhibits thickened myocardium accompanied with increased ventricular CMs. (A,B) Lateral view of wt clutch mates and hos mutant embryos at 96 hours post fertilization (hpf). (A′,B′) Hematoxylin/eosin staining of sagittal histological sections of wt and hos mutant ventricles at 96 hpf. In contrast to the wt ventricle, the hos mutant ventricular wall is thick and multilayered. (A″,B″) Confocal projections of wt and hos hearts dissected from Tg (myl7:mcherry.nls) and hos (myl7:mcherry.nls) at 96 hpf. (A‴,B‴) IF staining images of wt and hos hearts at 96 hpf. MF20 staining against meromyosin (red), which labels both cardiac chambers, the ventricle and atrium, and S46 staining against atrial-specific myosin (green) show normal cardiac chamber specification in both wt and hos embryos (scale bar: 50 µm). (C,D) Quantitative analyses of ventricular CMs at different developmental stages reveal significant increase in hos compared to that in wt at 96 hpf, while the hos mutation has no effect on the number of atrial CMs (n = 5). (E) Confocal images of dissected hearts from wt or hos crossed with Tg (myl7:cherry.nls;fli1:EGFP) at 96 hpf (scale bar: 50 µm). (F,G) Quantification of ventricular CMs and EGFP-positive (fli1-positive) cells in embryonic hearts of wt and hos at 96 hpf (n = 10). The number of endocardial cells in the ventricle is not altered in hos. v, ventricle; a, atrium; ventr., ventricular; atr., atrial.