Fig. 6

Overexpression of Fosl2 compromises SHF-mediated ventricular growth. (A,B) Confocal images of hearts in 48hpf control sibling (CTRL; A; n=11) and Fosl2-overexpressing (B; n=5) Tg(myl7:nlsDsRed-Express) embryos. (C) Bar graph showing the mean numbers of total, atrial and ventricular cardiomyocytes in both experimental groups. n.s., not significant, ***P<0.001. (D-I) Cardiomyocyte conversion assay. Control (n=7) and Fosl2-overexpressing (n=5) Tg(myl7:nlsKiKGR) embryos were photoconverted at 24hpf and imaged by confocal microscopy at 48hpf in the red (D,G) and green (E,H) channels. Merged images are shown in (F,I). Dashed lines highlight boundaries between cardiomyocytes that differentiated before (bottom) or after (top) photoconversion. Arrowheads identify SHF-derived green-only cardiomyocytes. (J) Bar graph showing the mean numbers of total ventricular cardiomyocytes, green and red positive cardiomyocytes, and green-only cardiomyocytes. Error bars represent s.d. ****P<0.0001, n.s., not significant. (K,L) Ventral images of control (n=30) and Fosl2 (n=35) overexpressing 48hpf embryos stained with a riboprobe for the SHF marker ltbp3. (M) Bar graph showing the relative levels of ltbp3 mRNA at 48hpf in both experimental groups as measured by quantitative PCR (n=3 biological replicates per group). **P<0.01. (N-O) Confocal images of the arterial poles in control (N; n=7) and Fosl2-overexpressing (N; n=6) embryos carrying the Tg(nkx2.5:nZsYellow) and Tg(cmlc2:AmCyan) transgenes co-stained with antibodies recognizing ZsYellow (red) or AmCyan (green). (P) Bar graph showing the mean numbers of extra cardiac SHF progenitor cells (red nuclei without yellow cytoplasm) in both experimental groups at 48hpf. Error bars represent s.d. ****P<0.0001. Scale bars: 50µm.