Fig 1: Endothelial Cell Heterogeneity in Neonatal Hearts(A) UMAP representation of different EC sub-populations analyzed.(B) Heatmap showing expression of top enriched genes for each EC sub-population.(C–F) UMAP plots showing expression of Art.EC marker gene Fbln5 (C), endocardial marker gene Npr3 (D), cell-cycle-related gene Mki67 (E), and capillary EC marker gene Gpihbp1 (F) in ECs.(G) UMAP plot showing expression of Rspo1 among all cells analyzed, which is restricted to the epicardial cell population.(H) Heatmap showing fold induction of Rspo1 expression at various time points after P1 or P8 MI detected by bulk RNA-seq.(I) scATAC-seq tracks showing open chromatin landscape of Rspo1 genomic region across various cell types. Positions of predicted KLF14 (blue), TFAP2A (orange), EGR1 (green), and E2F4 (red) binding sites from previous analysis (Figure 4D) are also shown.(J) Representative images showing in vitro human umbilical cord VEC (HUVEC) tube formation after 8 h of 200 ng/mL bovine serum albumin (BSA) (negative control), 10 or 100 ng/mL recombinant RSPO1, or 10 or 100 ng/mL recombinant VEGF treatment, cultured in Matrigel, with quantifications showing the number of branching points per field under each treatment (n = 15 per each group; ****p < 0.0001). Scale bar, 500 µm.See also Figure S5.