Squid Pax-6 and eye development

Pax-6 in vertebrates and its homolog eyeless in Drosophila are known to be essential for eye development. Here we investigate the role of Pax-6 in eye development in another major systematic group, molluscs. We demonstrate that alternatively spliced RNAs derived from a single Pax-6 gene in the squid (Loligo opalescens) are expressed in the embryonic eye, olfactory organ, brain, and arms. Despite significant sequence differences between squid Pax-6 and Drosophila eyeless in the region outside the paired- and homeodomains, squid Pax-6 is able to induce the formation of ectopic eyes in Drosophila. Our results support the idea that Pax-6 related genes are necessary for eye and olfactory system formation throughout the animal kingdom.