Fig. 2: Prediction of cardiac fibroblasts as pro-maturation factor.

a–d Subtype distribution of EC (endothelial cell, a), FB (fibroblast, b), MP (macrophage, c) and SMC (smooth muscle cell, d) across different stages. The total number of cells at each time point was taken as 100%. Arrows indicate cell subtypes with significantly changed proportions in P1 versus P56 hearts (see “Methods”). Right: selected top genes in cell subtypes apparently changed in P56 vs. P1 hearts, respectively. Please see Supplementary Data 8–11 for the full lists of genes in each cell subtype. e Ratio changes of altered cell clusters in P56 vs. P1. Dash lines indicate 10% cutoff which was used to define significantly changed cell subtypes in subsequent analyses (Supplementary Data 12). f Correlation analysis to show potentially matched pairs between the significantly altered genes encoding secreted proteins in representative cell clusters and signaling pathways in CM maturation during P1–P56 heart development. Each pink diamond represents signaling pathway (Supplementary Data 13). Each circle/dot indicates a secretory protein from a given cell type. Each connecting line indicates the correlation between a given secretory protein and a specific pathway. g Heatmap displaying the expression of genes in the correlation analysis (f) across all representative cell clusters (Supplementary Data 14). h, i Sum of all matched ligands (f) expressed in increased (i) or decreased (h) cell subtypes, respectively. j Bubble chart to show putative ligand–receptor pairs between differentially expressed receptors in CM clusters and corresponding ligands in significantly changed cell types (g). k Quantification of ligand–receptor pair counts (j) in each cell type.