ZFIN Image: Kula-Alwar et al., 2020, Fig. 2

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Figure Caption

Fig. 2

CM addition, hypertrophy and proliferation are involved in ventricular growth between 3 and 5 dpf. (A) Three Optical sections of 5 dpf Tg(myl7:GAL4FF)^hu6531;Tg(5XUAS:RFP)^zf83;Tg(UAS:h2az2a-GFP)^hu6851 larval heart immunostained for GFP (green), RFP (red) and PH3 (magenta) to reveal the sole PH3⁺nucGFP⁺ CM detected in this heart (arrow). Note the additional PH3⁺nucGFP⁻ cells enclosed by the myocardial layer (arrowheads). (B) Number of PH3⁺ CMs/ventricle at 3 dpf, 4 dpf and 5 dpf. Mean ± SEM. Each dot represents an animal. (C,D)Tg(myl7:GAL4FF)^hu6531;Tg(UAS:h2az2a-GFP)^hu6851 embryos were exposed to EdU between 4 and 5 dpf. A short confocal stack reveals EdU-labelled CMs (arrowheads, C), which were quantified as the fraction of EdU⁺ nuclei in H2A-GFP-labelled CMs in ventricle, atrium and whole heart (D). (E,F) Confocal images of anterior ventricle and OFT region of a Tg(nkx2.5:galFF);Tg(UAS:h2a-gfp);Tg(myl7:nucDsRed) larva imaged at 3 and 5 dpf showing a nucGFP⁺;nucDsRed⁻ cell population (white bracket) adjacent to the OFT region (arrow) at each stage (E). nucGFP⁺ cells were counted in the bracketed areas (F). (G,H) Confocal stacks of embryos of 3.5 (G) and 6 dpf (H) carrying Tg(myl7:EGFP)^twu26 and Tg(–5.1myl7:DsRed2-NLS)^f2. G′ and H′ show in greater detail the boxed OFT region. EGFP⁺ dsRed⁻ cells are clearly present at 3.5 dpf indicating recently differentiated CMs (arrowheads), whereas by 6 dpf all cells seem to be positive for both EGFP and DsRed. (I) Schematic diagram of the Kaede conversion experiment. (J) Confocal stacks of hearts 5 dpf embryos carrying Tg(myl7:GAL4FF)^hu6531and Tg(UAS:Kaede)^rk8 in which Kaede was converted from green to red at 3 dpf. Transmitted light of the scanned area is shown in J’. Cells expressing green Kaede but no or little red Kaede are marked by white arrow (OFT and ventricle nearby), light blue arrow (AVC), and yellow arrow (ventricle apex). Note, atrial cell expressing green Kaede only (asterisk) was found only in this embryo. Scale bars = 50 μm, except A and E = 20 μm.

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Reprinted from Developmental Biology, 470, Kula-Alwar, D., Marber, M.S., Hughes, S.M., Hinits, Y., Mef2c factors are required for early but not late addition of cardiomyocytes to the ventricle, 95-107, Copyright (2020) with permission from Elsevier. Full text @ Dev. Biol.