Purpose: Heterozygous defects in the highly conserved PAX6 homeobox gene are associated with aniridia, an inherited human disorder affecting several ocular structures, including the adult cornea. This work establishes the pattern of Pax-6 gene expression in the surface epithelia of the late embryonic and adult eye.
Methods: Chick embryo sections and wholemounts, as well as adult mouse and monkey tissues, were analyzed by in situ hybridization and immunohistochemistry with probes specific to Pax-6. Western immunoblots were used to detect Pax-6 protein, and mRNA expression was analyzed by quantitative reverse transcription-polymerase chain reaction.
Results: In days 5 and 6 chick embryos, Pax-6 protein is found in the nuclei of all cells within the corneal epithelium and in the future conjunctiva. Although not detected in the cornea by in situ hybridization, Pax-6 mRNA is, in fact, present at levels comparable to those observed in the retina. In the mature mouse, Pax-6 protein was expressed in all cells of the corneal epithelium, the limbus, and the entire conjunctiva. Similar results were obtained for the monkey cornea.
Conclusions: These data indicate that in addition to its role in the embryo, Pax-6 is expressed strongly in surface epithelia of the adult cornea and conjunctiva. In cells of these tissues, the gene may function by regulating structural or secretory specializations. Pax-6 might play a direct role in the maintenance and proliferation of corneal stem cells, a vital process that appears to be defective in aniridia.