The ventricular deficit resolves in fosl2 mutants through extension of the SHF-mediated cardiomyocyte accretion window. Cardiomyocyte photoconversion assay. Control sibling (CTRL; A-C; n=11) and fosl2-null (D-F; n=7) Tg(myl7:nlsKiKGR) embryos were photoconverted at 23hpf and imaged by confocal microscopy at 32hpf in the red (A,D) and green (B,E) channels. Merged images are shown in C and F. Dashed lines highlight boundaries between cardiomyocytes that differentiated before (bottom) or after (top) photoconversion. (G) Bar graph showing the mean numbers of total ventricular cardiomyocytes, green and red positive cardiomyocytes, and green-only cardiomyocytes. Error bars represent s.d. n.s., not significant. Control (H-J; n=19) and fosl2 mutant (K-M; n=5) Tg(myl7:nlsKiKGR) embryos were photoconverted at 48hpf and imaged by confocal microscopy at 60hpf in the red (H,K) and green (I,J) channels. Merged images are shown in J,M. Dashed lines highlight boundaries between cardiomyocytes that differentiated before (bottom) or after (top) photoconversion. Arrowheads identify SHF-derived green-only cardiomyocytes that differentiated after 48 hpf specifically in fosl2-null animals. (N) Bar graph showing the mean numbers of total ventricular cardiomyocytes, green and red positive cardiomyocytes and green-only cardiomyocytes. Error bars represent s.d. n.s., not significant, ****P<0.0001. Scale bars: 50µm.
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