A, Cell lineages targeted by Tie2-Dre and Wt1-CreER. B, Schematic showing the working principle for sequential Dre and Cre recombination. The final readout is Cre-loxP recombination. C, Whole-mount fluorescent images of Tie2-Dre;Wt1-CrexER;R26-tdTomato heart from 6 week old mice. Insert indicates bright-field image of the same heart. D, Immunostaining for tdTomato and CDH5 on heart section shows CDH5+tdTomato+ coronary vessels. LV, left ventricle. E, Immunostaining for tdTomato and CDH5 on sections from organs of 6 week old Tie2-Dre;Wt1-CrexER;R26-tdTomato mice. Scale bars, 1 mm in C,E; 100 µm in D. Each image is representative of 5 individual samples.