Fig. 7

Cell fusion deficiency negatively affects cardiomyocyte proliferation and cardiac function. a–d jam3b mutants show a reduction in the number of LIFEACT-GFP⁺ skeletal and cardiac myocytes. Embryos from a cross of jam3b ^+/− ;Tg(ubb:FATC) and jam3b ⁺⁻ ;Tg(hsp:cre) fish were heat-shocked at 24 hpf. LIFEACT-GFP⁺ (green) skeletal (a) and cardiac (b) muscles were detectable at 48–52 hpf. DAPI-stained nuclei are shown in blue. c, d LIFEACT-GFP⁺ skeletal myocytes per 10,000 μm² of trunk surface area (c) and LIFEACT-GFP⁺ ventricular cardiomyocytes (d) in jam3b ^−/− embryos and jam3b ^+/? siblings. e–g Jam3b deficiency reduces cardiomyocyte proliferation. A 16 h EdU pulse (green) labeled mitotic cardiomyocytes (nDsRed⁺, red) (e) shown as percentage of total cardiomyocytes (f); total cardiomyocyte numbers (g) in ventricles of 6 dpf jam3b ^−/− ;Tg(myl7:nDsRed2) and jam3b ^+/? ;Tg(myl7:nDsRed2) siblings. h–j jam3b deficiency impairs cardiac function. h The 5 dpf jam3b mutants exhibit pericardial edema (28 out of 36 fish with edema were jam3b^−/−). i, j The 5 dpf jam3b mutants also display decreased fractional shortening (i) and blood flow velocity (j) compared to control siblings, as evidenced by a significant difference in average maximum flow velocity (k). a, b, e are maximum or average intensity projections of 20–65 μm thick confocal stacks. h are single focal planes of confocal images showing larvae in lateral views, anterior up and dorsal to the left. In all plots, bars and error bars represent means ± S.E.M. Each circle and triangle represents an embryo (c) or a heart (d, f, g, k, j). *p ≤ 0.05, **p ≤ 0.01, ***p ≤ 0.001 (two-tailed student’s t-test); 10–12 (a–d), 16 (e–g), 36 (h), and 11–25 (i–k) −/− and +/? sibling animals were examined. Scale bars: 20 μm (a, b, e), 40 μm (h)