Fig. 2.

Identification of stem cells in the SHF. (A) Cells doubly positive for Isl1 and Nkx2.5 (white arrowhead) represent a myocardial and smooth muscle lineage. (B) Cells doubly positive for Isl1 and Flk1 (white arrowhead) represent a smooth muscle and endothelial cell lineage. Cultures are a mixed population, with some cells expressing only one marker (green arrowhead) or no marker (blue asterisk). (C-E) Asymmetrical localization of Numb (green, white arrows) in SHF cells suggests existence of a stem cell population [C,D are also stained for transitin, a type IV intermediate filament protein that has been shown to co-localize with Numb (Wakamatsu et al., 2007)]. (D) Cell with condensed chromatin and asymmetric localization of Numb. (E) Asymmetric localization of Numb in Isl1-expressing cells.