Cardiac looping morphogenesis in 9.5-dpc embryos. (a and c) Right and (b and d) left frontal views of whole embryos are shown. Cardiac looping was morphologically affected in the 9.5-dpc Rae28–/– embryo (c and d). IVS, interventricular sulcus; BC, bulbus cordis; TA, truncus arteriosus; AVC, AV canal; LV, left ventricle; LA, left atrium; RV, right ventricle. +/+, a wild-type embryo; –/–, a Rae28–/– embryo. Scale bar: 500 μm.