Transdifferentiation in Xenopus laevis eye

the prospective neural retina (NR) in the distal layer and the retinal pigmented epithelium (RPE) proximally. Accordingly, molecular markers accompany morphogenesis by restricting their expression to definite compartments. For instance, in the optic cup, the prospective neural retina expresses Chx10, and the RPE,Mitf. However, to facilitate identification of definite events during oculogenesis, there remains a need to identify additional markers of optical development. Thus, we performed here a screen for Wnt ligands that are expressed during eye development. Specifically, we examined the expression of Wnt1, Wnt3, Wnt4-1 andWnt5A during chick optic vesicles stages up to optic cup formation. Of these four genes, only Wnt5A was consistently expressed in the dorsal optic cup. Although Wnt1, Wnt3 and Wnt4-1 were present in the developing nervous system, neither was found in the optic vesicle or cup. Wnt5A was first detected at the dorsal region of the RPE at stage HH14. In stages HH15 and HH16, its expression domain increased ventrally in the both nasal and temporal domains. Throughout all these stages, the labeling was restricted to the RPE only, and was completely absent in the neural retina. Based on these data, we would like to proposeWnt5A as a marker for early dorsal retinal pigmented epithelium. Corresponding author: reneyan@icb.usp.br.