Transdifferentiation of eye tissues in anuran amphibians: Analysis of the transdifferentiation capacity of the iris of Xenopus laevis larvae

Abstract. Lensectomized Xenopus laevis larvae are capable of regenerating a lens from the cells of the outer cornea. Unlike the outer cornea, the iris of larval Xenopus exhibits a high degree of phenotypic stability, even when it has been damaged to various degrees in order to stimulate its latent transdifferentiative competence. However, when isolated from its surrounding tissues and implanted in an appropriate site, the dorsal iris of larval Xenopus is capable of following a differentiative pathway different to that normally followed in situ. Our results show that, when such an implant is placed in the vitreous chamber of a lensectomized eye, the pigmented epithelial cells of the iris transdifferentiate into neural retina regardless of whether the iris stroma is present or not. Unlike the vitreous chamber, the environment of the anterior chamber of a lensectomized eye does not promote the transdifferentiative process of the iris. We suggest the existence of eye factors that promote retina-forming transformation of the iris and that are distributed in a gradient in lensectomized eyes.