FIGURE 2

The hos mutation leads to not cardiac hypertrophy but hyperplasia due to increased proliferation of embryonic ventricular CMs. (A) Confocal projections of fluorescent CM nuclei (myl7.nls) and membrane (minUnc45b.CAAX) in embryonic hearts of wt and hos embryos at 96 hpf (scale bar: 50 µm). (B) Analyzed CM sizes of wt and hos ventricles (n = 102). (C) Dissected hearts of hos (myl7:mcherry.nls) incorporated with EdU visualizing DNA synthesis of cells at 96 hpf (scale bar: 50 µm). (D,E) Quantification of EdU-positive (EdU⁺) CMs indicating the S-phase of cell cycle (D) and the mitotic index of wt and hos(E) (n = 5). The hos mutation induces CM proliferative potential. (F) IF staining of pH3 visualizing the M-phase of cell proliferation in embryonic zebrafish hearts of wt and hos embryos at 96 hpf (scale bar: 50 µm). (G,H) Quantification of pH3-positive (pH3⁺) CMs and the mitotic index (pH3⁺ CMs/total ventr. CMs) in wt and hos ventricles at 96 hpf (n = 10). v, ventricle; a, atrium; ventr., ventricular.