Figure 7.

Schematic representation of the alignment between aortic (A) and pulmonary (P) outflows in a frontal section (upper panel), alignment of A and P valves in a transverse section (middle panel), and alignment between A and P vessels and right (R) and left (L) ventricles (lower panel). (a) In wild-type embryos, aortic and pulmonary outflow tracts spiral around each other. The pulmonary valve locates rostrally (above the plane of the drawing; indicated by dotted lines) and anteriorly to the aortic valve so that two valves do not appear in a same plane. (b) In ECE-1–/– mutant embryos, the alignment between A and P outflows remains in a spiral position, whereas the aortic valve and outflow shift rostrally and to the right so that two valves appear in the same plane. The aorta often overrides the interventricular septum. (c) In ECE-1–/–; ECE-2–/– double mutant embryos, the aortic and pulmonary outflows run side by side in a parallel position, often showing double outlet right ventricle (DORV).