Fig. 6

Section images showing HCR staining results of hapln1a (green) and ptx3a (magenta) at 3 (a), 7 (b), and 14 dpa (c). Epicardial cells are labeled with tcf21:nucEGFP (blue). Arrows in a–c indicate representative hapln1a⁺ cells. The brackets in b outline the regenerated regions that express hapln1a. White dashed lines indicate the injury sites. Scale bars, 50 μm. d Schematic of transgenic lines and experimental design to define the fate of aEPCs. 4HT was used at 5 μM. e Orthogonal view of a z-stack image showing the ventricular surface layers from hearts carrying the ubi:Switch;ptx3a:CreER^t2 reporters. A maximum projection image of the x-y plane is shown with hapln1a expression (HCR staining) in green and mCherry in magenta. White dashed lines and numbers indicate positions for views of the y-z planes (right) and the x-z planes (top), respectively. Nuclei were stained with DAPI (blue) and was omitted from the maximum projection image to keep image clarity. Arrows indicate representative hapln1a⁺mCherry⁺ cells. Arrowheads indicate mCherry⁺ cells in the epithelial layer. Scale bar, 50 μm. The framed regions are enlarged to show details in f. f Optical section (z-stack) images of the framed regions in e. Arrows indicate hapln1a⁺mCherry⁺ cells. Scale bar, 20 μm. g Orthogonal view of a z-stack image showing the ventricular surface layers from hearts carrying the ubi:Switch;ptx3a:CreER^t2 reporters. An optical section image (x-y plane) is shown at the bottom, and the x-z plane of z-stacks in shown on top. mCherry and HCR staining signals of podxl are shown in magenta and green, respectively. The white dashed line indicates position for the view of the x-z plane. Arrowheads indicate podxl⁺mCherry⁺ epithelial epicardial cells. h A UMAP highlights pseudotime trajectories a and c.