Hes1 in Heart Development Figure 5. Congenital heart defects in Hes1 mutant mice. (A) E15.5 hearts in ventral wholemount views (left) and cryostat sections at the levels indicated showing a normal configuration of the ascending aorta (ao) and pulmonary trunk (pt) in Hes1+/2 hearts (top) and a dextraposed aorta overriding a ventricular septal defect (arrowhead) in Hes12/2 hearts (middle (mild) and bottom (severe)). Note that the aorta in the bottom heart symmetrically overrides the ventricular septal defect. (B) Paraffin sections of E18.5 hearts in a frontal plane showing a ventricular septal defect (arrowhead) in a Hes12/2 (middle and bottom) but not Hes1+/+ heart (top). lv, left ventricle; rv, right ventricle. Scale bar: (A) 200 mm; (B) 500 mm. doi:10.1371/journal.pone.0006267.g005 Figure 6. Outflow tract morphogenesis in Hes12/2 embryos. (A) Ventral whole mount views of X-Gal stained hearts from E9.5 and E10.5 Hes1+/+, Hes1+/2 and Hes12/2 embryos carrying the Mlc1v-nlacZ-24 transgene. (B) Histograms showing OFT length measurements and the angle between the proximal and distal region of the OFT from Hes1+/+, Hes1+/2 and Hes12/2 hearts at E9.5 and E10.5. At E10.5, but not E9.5, Hes12/2 embryos display a shorter, straighter OFT (*, p,0.05; ***, p,0.001, Student’s t-test). doi:10.1371/journal.pone.0006267.g006 PLoS ONE | www.plosone.org 6 July 2009 | Volume 4 | Issue 7 | e6267