AN EYE OVER PAX-6

Pax-6 a member of the Pax gene family encoding phylogenetically conser ved transcription factors. Some of these genes, like Pax-6 bear two DN A-binding domains, namely the paired- and the homeodomains, the others bearing the paired domain only. In vertebrates, Pax-6 expressed in th e central nervous system and the endocrine pancreas. Pax-6 was recentl y shown to be a key regulator of eye development in both mammals and f lies, and to act as the master gene of drosophila eye development. In vertebrates Pax-G encodes four different proteins with distinct DNA,bi nding domains. Pax-6 is expressed through two promoters, PO ana P1. P1 is active first, PO being, activated at the onset of neuronal differe ntiation under the control of an intragenic sequence. Both promoters a re activated by the Pax-6 p46 product and the c-myb oncogene-product e xpressed in the neuroretina The multiplicity of the Pax-6 products and their probable involvement in distinct steps of the eye morphogenesis may explain why this gene is a master gene of eye development.