Genetic Analysis of Left-Right Axis Formations

Study Summary

The objective of these studies is to identify genetic factors that contribute to the pathogenesis of complex congenital heart disease and other more rare conditions resulting from disturbances in organ positioning. These are a group of medical conditions that are thought to stem from a poorly understood disturbance in the establishment of the basic body plan in the embryo. While the outside of the human body is generally symmetric with mirror image left and right sides, the positions of some internal organs are distinctly asymmetric. For example, the heart could not function properly as a mechanical pump if its connections to major blood vessels retained their initial symmetry. The left ventricle of the heart normally pumps blood to the body, while the right ventricle normally pumps blood to the lungs. Reversals in these blood vessel connections can be fatal. Similarly, the gut characteristically loops in a counterclockwise direction placing the stomach on the left side in most cases. Rare laterality anomalies can occur if this looping is in the other direction, or randomized (equally likely to loop in either direction). Serious medical problems can be caused by disturbances in the establishment, or maintenance of left-right (L-R) differences as key organs are developing in the embryo. We have established formal collaborative agreements with three major centers who have collected a large number of coded cases of congenital cardiac disease. Our research objective is to try to understand if specific genetic changes can contribute to a range of cardiac malformations. We utilize mutational analysis of candidate genes as our principal tool to study the genetics of L-R axis malformations. This protocol is also open to other conditions whose basis is also thought to result from L-R problems. In all cases, the patients continue under the care of the referring physician. We anticipate a minor role of NIH researchers and genetic counseling services if subjects either do not