Figure 6.

Ultrastructure of wild-type and Has2^–/– E9.5 mouse hearts. Scanning electron micrograph of the external structure of the heart from a wild-type (a–c) and an Has2^–/– embryo (d–f). Specimens were viewed from the left side (a and d), the front (b and e), and the right side (c and f). Note the apparent absence of the presumptive right ventricle and outflow tract in the Has2^–/– embryo compared with the wild type. Scanning electron microscopy of cross-sections of hearts from wild-type (g and h) and Has2^–/– embryos (i and j) reveal a lack of AV cushions and a compacted ventricle wall lacking trabeculations (arrowheads). There is a constriction at the site of the AV canal in the Has2^–/– embryo. LV, left ventricle; RV, right ventricle; AoP septum, aortic pulmonary septum. Asterisks indicate left posterior atrial wall. h and j are higher magnifications of g and i, respectively.