FIGURE 1

ruvbl2 ^lik mutant hearts show increased cardiomyocyte proliferation. Brightfield images of wild-type (A) and ruvbl2 ^lik/lik (B) embryos at 72 hpf. Anterior left, lateral view. (C,D) Confocal projections of fluorescent cardiomyocyte nuclei in hearts of 48 hpf control (CTRL) sibling (C; n = 6) and ruvbl2 ^lik/lik (D, n = 6) Tg (cmlc2:nucGFP) embryos V = ventricle; A = atrium. (E) Quantification of fold change in ventricular cardiomyocyte number in 48 hpf CTRL and ruvbl2 ^lik/lik hearts. Means ± s.d are shown. Not significant (ns); p > 0.05. (F,G) Confocal projections of fluorescent cardiomyocyte nuclei in hearts of 72 hpf CTRL (F; n = 6) and ruvbl2 ^lik/lik (G; n = 6) Tg (cmlc2:nucGFP) embryos. (H) Quantification of fold change in ventricular cardiomyocyte number in 72 hpf CTRL and ruvbl2 ^lik/lik hearts. Means ± s.d are shown. ***p < 0.0005. (I,J) Confocal projections of fluorescent endocardial nuclei in hearts of 72 hpf CTRL (I; n = 4) and ruvbl2 ^lik/lik (J; n = 4) Tg (fli1a:nucGFP) embryos. (K) Quantification of fold change in ventricular endocardial cell number in 72 hpf CTRL and ruvbl2 ^lik/lik hearts. Means ± s.d are shown. Not significant (ns); p > 0.05. (L) Schematic representing the myocardial proliferation assay by BrdU pulse between 48 and 72 hpf. (M–N′) Single plane confocal images of CTRL (M; n = 5) and ruvbl2 ^lik/lik (N; n = 5) hearts double immunostained to detect cycling (BrdU+) cardiomyocytes (MF20+) at 72 hpf. Boxed regions in (M,N) are magnified in (M′,N′) with white arrows highlighting double positive cells. (O) Quantification of cardiomyocyte proliferation indices in CTRL and ruvbl2 ^lik/lik ventricles. Means ± s.d are shown. *p < 0.05. Scale bars: 25 μm.