Transverse section of Postn-Cre(+) lacZ stained control AV cushion at E12.5 (A). Hand2 ISH of control (B) and H2CKO (C) AV cushion. Transverse section of Postn-Cre(+) β-galactosidase stained control OFT cushions at E12.5 (D). Hand2 ISH of control (E) and H2CKO (F) OFT cushion. Black arrows indicate cushion mesenchyme, brown arrows indicate the primitive tricuspid valve (TV), mitral valve (MV), and pulmonary valve (PV). Asterisks indicate deletion of Hand2, right ventricle, RV; left ventricle, LV.