Fig. 4

a–e HCR staining results of ptx3a (green) on heart sections collected at 1 (b), 3 (c), 7 (d), and 14 dpa (e) together with the uninjured control (Ctrl, a). tcf21:nucEGFP (magenta) labels the epicardial cells. Nuclei were stained with DAPI (blue). Single-channel images show signals of ptx3a or nucEGFP. White dashed lines indicate the injury sites. The framed regions are enlarged to show details on the right of each panel. Arrows denote representative ptx3a⁺EGFP⁺ cells. Scale bars, 100 μm. f Schematic for generating the knock-in alleles for ptx3a. The gRNA binding site is marked with a cyan arrow. g The ptx3a^RNTR reporter recapitulates expression of ptx3a in the injured heart (3 dpa). No conclusive epicardial expression was observed in the uninjured heart (Ctrl). tcf21:nucEGFP (magenta) labels the epicardial cells. Nuclei were stained with DAPI (blue). Single-channel images show signals of ptx3a^RNTR (with anti-DsRed antibody staining) at the bottom. White dashed lines indicate the injury sites. The framed regions are enlarged to show details on the right. Arrows denote representative RNTR⁺EGFP⁺ cells. Images of additional timepoints are in Supplementary Fig. 7. Scale bar, 100 μm. h Schematic for generating the knock-in alleles for col12a1b. The gRNA binding site is marked with a cyan arrow. i Section images showing col12a1b^EGFP reporter expression in green and ptx3a^RNTR expression in magenta (with anti-DsRed antibody staining). No epicardial EGFP expression was observed in the uninjured heart (left). Nuclei were stained with DAPI (blue). Single-channel images show signals of col12a1b^EGFP or ptx3a^RNTR. White dashed lines indicate the injury sites. The framed regions are enlarged to show details on the right. Arrows denote representative EGFP⁺mCherry⁺ cells. Scale bar, 100 μm.