Laterality, heterotaxy, and isolated congenital heart defects : The genetic basis of the segmental nature of the heart.

To date, the role of NODAL in normal and abnormal L-R asymmetry has been well established. In a recent paper, mutations of this gene have been reported in heterotaxy but also in transposition with D- or L-ventricular loop. The effects of NODAL and other laterality genes can be recognized separately in all three cardiac segments: for topology and septation of the atria, for ventricular looping, and for spiralization and alignment of the great arteries.