Chemotaxis or adhesion gradient? Pronephric duct elongation does not depend on distant sources of guidance information.

Previously published experimental studies have led to conflicting interpretations concerning the mechanism guiding pronephric duct elongation in the urodele embryo. Although most studies have led to the conclusion that duct migration is directed by an adhesion gradient (haptotaxis), one set of experiments has been interpreted as supporting chemotactic guidance. We have resolved this conflict by conducting grafting experiments in Ambystoma embryos which distinguish between these two possible mechanisms of cell guidance. Our results provide an alternative explanation for the observations originally interpreted as supporting chemotaxis and add further evidence for adhesive guidance.