FIG. 4.

Single-cell RNA-seq profiles from hiPSC-CMs do not demonstrate distinct cardiomyocyte subtype commitment. (A) Heatmap of expression patterns for cardiomyocyte genes across all 85 cells on days 12 and 40 (each column representing one cell). Blue and yellow represent low and high expression, respectively. MYL2 transcripts were detected in >25% of D12 and 100% of D40 cells, NKX2.5 transcripts were detected in >75% of all cells, and all other transcripts were detected in every cell. (B) Boxed D12 and D40 cells were selected as cardiomyocytes for further analysis, according to unsupervised hierarchical clustering, robust expression of cardiomyocyte genes, and low expression of cardiac fibroblast genes. (C) Heatmap of expression patterns for atrial-, nodal-, and ventricular-associated genes in cardiomyocytes. Genes with significantly different expression (log₂FC >2 and P < 0.05) between D12 and D40 are marked with an asterisk. (D) Heatmap representation of a correlation matrix for expression of atrial- and ventricular-associated genes, labeled in green (atrial) or red (ventricular). Positive and negative correlations are labeled as orange and blue, respectively.