Role of Homeobox Gene Nkx2-5 in Heart Development and Congenital Heart Disease

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Congenital abnormalities of the heart occur in ~1 in 100 live births and 1 in 10 still births in Western populations. The genetic pathways underlying cardiac development are now being dissected with increasing vigour in an effort to understand both the morphological progressions and genetic basis of heart defects. Mutations in a cardiac gene called Nkx2-5, which encodes a transcriptional regulatory protein, can cause heart defects in human families and isolated individuals, most predominantly atrial septal defect (hole in the heart) associated with an abnormality in electrical activity of the heart. Nkx2-5 is expressed in the precursor cells of the muscle and other lineages that make up the heart in the embryo, then in the muscle layer of the heart throughout foetal and adult life. Mouse hearts that lack the Nkx2-5 gene altogether arrest at an early stage of heart development showing a complete block to ventricular chamber formation. Mice lacking only one copy of the Nkx2-5 gene have ASD and electrical defects, similar to the human disease. Building on these findings we have developed a suite of new genetic reagents with which to gain a deeper understanding of the role of Nkx-5 in development and disease. These include a mouse strain from which Nkx2-5-positive muscle cells can be purified away from other cell types in the heart, and another mouse strain that represents a good model for common congenital heart defects. We will further investigate the role of Nkx2-5 in allocation of cell types in the heart, chamber formation and birth defects using these reagents.