Alterations of heart development in Xenopus laevis by galactoside-binding lectin or its sugar hapten inhibitor.

The early heart anlagen of Xenopus laevis embryos were exposed to purified embryonic galactoside-binding lectin or its potent hapten inhibitor thiodigalactoside (TDG). Heart development was then studied using a variety of microscopical techniques. Conotruncal morphology and positioning with respect to the ventricle are altered in treated animals. In 34% of animals treated with lectin and 35% treated with TDG, the conotruncus leaves the ventricle from an abnormal location. Lectin or TDG treatments are also correlated with altered conotruncal shape, with the conotruncal regions showing greater radii of curvature compared to controls. Conotruncal myocyte differentiation is altered by the test treatments, with lack of development of organized myofibrillar arrays. Conotruncal cushion development is also affected. Changes occur in the shape and size of the primary conotruncal cushion, and alterations of outflow tract septation develop. Less maturation of ventricular myocytes is also observed in test animals. The results suggest that galactose-lectin interactions are important in heart development.