Figure 1

Increase in neonatal heart-body weight. Wild-type C57/BL6 neonatal mice (n = 3/time point) were sacrificed at the indicated time point and their body (A) and heart (B) weights were measured. The ratio of heart weight to body weight remained relatively constant during the first 3 weeks after birth (C). (D) Schematic diagram of flow cytometric analysis of eGFP + cells from developing and neonatal (P4) Nkx2.5 enh-eGFP hearts. (E) Quantification of the percentage of eGFP + cells in embryonic hearts and in the non-myocyte fraction of neonatal hearts (n = 5/time point). (F) Quantitative PCR analysis of gene expression in FACS-purified GFP + (green) and GFP- (grey) cell populations (n = 5). Note that CM-associated cells localized predominantly in the eGFP- population. (G-H) Identification of proliferating Nkx2.5 enh-eGFP + cells in the neonatal heart. (G) Cell cycle analysis of eGFP + cells from day 6, 10, and 22 neonatal hearts (n = 3/time point). Shown is a representative flow cytometry plot of BrdU and 7-AAD incorporation into eGFP + cells. (H) The proportion of eGFP + cells in G_0/1 (white), S (grey), and G₂ (black) phases of cell cycle. The % of cells that are in G_0/1 or S phases are indicated.