Function of Rx, but not Pax6, is essential for the formation of retinal progenitor cells in mice

Rx plays a critical role in eye formation. Targeted elimination of Rx resul ts in embryos that do not develop eyes, In this study, we have investigated the expression of Otx2, Six3, and Pax6 in Rx deficient embryos. We find th at these genes show normal activation in the anterior neural plate in Rx-/- embryos, but they are not upregulated in the area of the neural plate that would form the primordium of the optic vesicle. In contrast, in homozygous Small eye embryos that lack Pax6 function, Rx shows normal activation in t he anterior neural plate and normal upregulation in the optic vesicle/retin al progenitor cells, This suggests that neither Rx expression nor the forma tion of retinal progenitor cells is dependent on a functional copy of the P ax6 gene, but that Pax6 expression and the formation of the progenitor cell s of the optic cup is dependent on a functional copy of the Ru gene, (C) 20 00 Wiley-Liss, Inc.