Laterality disturbances

One of the earliest, and most crucial, steps in cardiac morphogenesis is looping of the primitive heart tube. This process provides the spatial context for all future steps in heart development, and defects in cardiac loop formation result in complex structural heart disease. Loop formation is also one of the first visible asymmetries along the left-right body axis, and as such is dependent upon the development of the entire embryonic left-right axis. Formation of the left-right body axis is a developmental process, that, like the formation of the anteroposterior and dorsoventral axes, is programmed by multiple genetic steps. It is also a process that is essential and unique to vertebrate development. Therefore, an understanding of the development of left-right asymmetry at the genetic and molecular level will greatly aid in the understanding of the etiology of this complex group of congenital heart defects.