Pax6 induces ectopic eyes in a vertebrate

We report here that misexpression of the transcription factor Pax6 in the v ertebrate Xenopus laevis leads to the formation of differentiated ectopic e yes, Multiple molecular markers indicated the presence of mature lens fiber cells, ganglion cells, Muller cells, photoreceptors and retinal pigment ep ithelial cells in a spatial arrangement similar to that of endogenous eyes. Lineage tracing experiments showed that lens, retina and retinal pigment e pithelium arose as a consequence of the cell-autonomous function of Pax6. T hese experiments also reveal that the cell autonomous activity of misexpres sed Pax6 causes the ectopic expression of a number of genes including Rx, O tx2, Six3 and endogenous Pax6, each of which has been implicated in eye dev elopment. The formation of ectopic and endogenous eyes could be suppressed by coexpression of a dominant-negative form of Pax6, These data show that i n vertebrates, as in the invertebrate Drosophila melanogaster, Pax6 is both necessary and sufficient to trigger the cascade of events required for eye formation.