Fig. 3. Wild-type OFT myocardium rescues the endothelial-to-mesenchymal transformation defects of Fgf8;Isl1Cre mutants. (A) Explant (Ex) culture of mouse E9.5 control OFT. (A') Close-up of boxed region in A. Arrowhead demarcates a rare, rounded cell that migrated from the explant but failed to invade. (B) Explant culture of an E9.5 Fgf8;Isl1Cre mutant OFT reveals failure of endothelial EMT. (B') Close-up of boxed region in B. Arrows point to rare cells that underwent EMT. (C,C') Co-culture of E9.5 OFTs from Rosa26^lacZ;Isl1Cre (blue) and controls (white). (C') Enlargement of boxed area in C. (D,D') Co-culture of control and Fgf8;Rosa26^lacZ;Isl1Cre E9.5 OFTs shows rescue of mutant cells (blue, arrowheads). (D') Enlargement of boxed area in D. (E,E') Complementary experiment to D; control cells are β-galactosidase-positive (blue) and rescued Fgf8 mutant cells (arrowheads) are white. (E') Enlargement of boxed area in E. For quantitated data, see Fig. S2 in the supplementary material.