Regulation of eye formation by the Rx and pax6 homeobox genes

The Rs and pax6 homeobox genes are among the earliest genes expressed in th e eye primordia and play crucial roles in the specification of ocular fate. These genes exhibit strong conservation of sequence and expression pattern s among vertebrates. As transcription factors, Rx and Pax6 exert their effe cts through the activation and repression of downstream targets. Overexpres sion of each protein induces ectopic retinal tissue formation, as well as i nduction of the other. pax6 gene mutations have been correlated with an arr ay of human diseases, and a similar array of mutations potentially exists f or the human Rs gene. Based on Functional studies, the vertebrate Rs and pa x6 genes are likely to regulate cell proliferation and are required for the initial commitment to retinal and lens cell fate, respectively, while pax6 appears to play additional roles in the formation of the retina and cornea .