[Embryological and genetic mechanisms of cardiac great arteries malformations]

Developmental genetics of congenital heart diseases have evolved from analysis of embryonic hearts towards molecular genetics of cardiac morphogenesis with a dynamic view of cardiac development. Ablation techniques, transgenic animal models and clonal analysis of the developing heart led to identification of different cardiac lineages and their respective roles. The mechanistic approach for great arteries anomalies has led to emerging concepts such as common embryological origin of anatomically different cardiac defects, phenotypic continuum of left heart obstructive defects, or developmental algorithms for cardiac isomerisms. Recent experiments that demonstrated the myocardial rotation of the outflow tract in mouse embryos led to a better understanding of the origin of transposition of the large arteries. This has also raised the hypothesis of a new group of congenital heart anomalies defined as laterality defects limited to a segment of the embryonic heart. These results confirm that genetic heterogeneity of congenital heart defects is related to the heterogeneity of the mechanisms that finally produce the same phenotype.