FIGURE 2.

Genes that contribute to cell-cycle activity and muscle growth tended to be more highly expressed in clusters associated with regenerating hearts than in CTL hearts at P28 and afterward. Sparse analysis was conducted for the expression of genes associated with (A) the cell-cycle, (B) adrenergic signaling, (C) the contractile activity and development of cardiac muscle, and (D) cardiac-muscle cell proliferation and muscular growth; then, the proportion of cardiomyocytes with high, medium, or low levels of expression was calculated for each cluster.