Fig. 1.

Clonal analysis of the secondary heart field. (A-C) Secondary heart field progenitors differentiate into beating myocardium (red), smooth muscle (elongated green) and endothelial cells (rounded green) after 96 hours in culture. B and C are enlarged regions from A. (D-K) Clonal analysis shows the that SHF contains a multipotent progenitor cell that is capable of differentiating into myocardium (D,G,J,K), smooth muscle (E,H-K) and endothelial cells (F,I,K). Tripotency is demonstrated in K with a clone expressing multiple cardiac cell lineage markers. Blue labels the nuclei in all the cells and the nuclei plus the cytoplasm in the MF20-positive cell (blue arrowhead). Arrows indicate nuclei expressing no differentiation markers.