Developmental Cardiology Comes of Age

Abstract

Over the last 10 years, significant progress has been made in the understanding of molecular and genetic determinants of heart formation. An ever growing number of genes have been identified that are required for cardiogenesis, as evidenced by severe abnormalities in cardiac development produced by inactivation in the mouse or inhibition of gene function in other model organisms.1 In general, scientists have identified these genes because of their expression in early cardiac tissues or because of the severe phenotype produced by mutation or inactivation. Gross abnormalities of cardiac development lead to embryonic demise either during midgestation or in the peripartum period, and the underlying severe defects in cardiac structure or function have been relatively easy to determine and describe.1 2 3 Similar defects in the human versions of these genes may account for embryonic lethal forms of human congenital heart disease. It has been hypothesized that hypomorphic mutations or reduction in gene dosage may result in less severe forms of congenital heart disease, such as those seen in surviving newborns and adults. Alternatively, clinically relevant cardiovascular developmental defects affecting infants and adults generally may result from mutations in genes entirely unrelated to those critical during early stages of cardiac specification and heart morphogenesis, making these factors less attractive for intensive study as disease-causing genes. Data to support the former hypothesis have recently come to light. Perhaps the most intriguing example comes from the study of a mammalian homologue of a gene first described in the fruit fly, Drosophila melanogaster . This organism has an open circulation in which hemolymph is distributed with the assistance of a contracting dorsal aorta. Although structurally dissimilar from the …