A Cascade of Gene Action Controlling Heart Asymmetry and Torsion in Embryonic Development

Abstract Lateralized looping of the heart tube, with associated torsion of the embryo axis, is the first structural sign of the consistent left–right asymmetrical organization that characterizes all vertebrate embryos. Rare failures or reversals of this asymmetry in humans lead to clinically important syndromes of malformation in heart and great blood vessels. Recently, elements of the genetic control sequence underlying this left–right aspect of development have been uncovered. The normal sequence of transmission for asymmetry information can now be traced to a point close to the actual execution of right-hand looping in the heart tube, with the hope that the further sequence of gene activity, within the heart itself and directing these events, may soon be uncovered.