Fig. 4

In vivo enhancer activity of differentially accessible chromatin regions in the mdka locus (A) Accessibility of peaks close to mdka. Red frames indicate peaks analyzed further in (B), (C), and (G) (e1) and (D), (E), and (H) (e2). (B) Stable mdka_e1-driven mCherry expression (magenta) at 5 dpf. Expression of tcf21 is indicated by myr-eGFP fluorescence (green membranes). (B′) Single optical section from (B). (B′′) mCherry fluorescence in the epicardium (asterisk). (C) Stable mdka_e1-driven mCherry expression in the adult cryoinjured heart at 3 dpi. (C′) High magnification image of a part of the injury area (ia) in (C). (D) Stable mdka_e2-driven mCherry expression (magenta) at 5 dpf. (D′) Single optical section from (D). (D′′) mCherry fluorescence in the epicardium (asterisk) is absent. (E) Stable mdka_e2-driven mCherry expression in the adult cryoinjured heart at 3 dpi. (E′) High magnification image of a part of the injury area in (E). An epicardial cell showing mdka_e2 activity is denoted by an asterisk. (F) Workflow of adult zebrafish heart injury followed by electroporation of enhancer activity reporter constructs. (G and H) Transient mCherry expression driven by mdka_e1 (G) or mdka_e2 (H) following electroporation into the cryoinjured adult heart. (G′, H′, and H′′) High magnification images of (G) and (H). In (H′) and (H′′), epicardial cells showing mdka_e2 activity are denoted by asterisks. Scale bars: 100 μm in (C), (E), (G), and (H); 50 μm in (B), (B′), (D), and (D′); and 20 μm in (B′′), (C′), (D′′), (E′), (G′), (H′), and (H′′). In (A), yellow: enrichment tcf21 larval epi, green: enrichment tcf21 cryo. (B) and (D) show endogenous fluorescence, (C), (E), (G), and (H) show immunefluorescence. V, ventricle; A, atrium; BA, bulbus arteriosus. See also Figure S2.