Molecular Mechanisms of Development and Differentiation
of the Eye of Drosophila and Vertebrates

V. I. Mitashov¹ and S. Koussalokos²

¹Kol’tsov Institute of Developmental Biology, Russian Academy of Sciences, ul. Vavilova 26, Moscow, 117808 Russia
² University of Athens, Athens, Penepistimopolis, 15784 Greece

Received April 20, 2000

Abstract—The development of the eye is compared in Drosophila and vertebrates. Although the structure of
the compound eye of invertebrates and of the cameral eye of vertebrates differs morphologically, there are strik-
ing similarities at the molecular level. Three groups of genes control the morphogenesis of the eye: the genes
responsible for eye rudiment formation, neurogenic genes, and proneural genes. In the eye rudiments of Droso-
phila and vertebrates, the homologous regulatory homeobox-containing genes ey/Pax6, so/Six3, rx/Rx, and
optix/Optx2 are expressed. Transcription factors encoded by these conservative genes are involved in specific
interactions with DNA. Another set of homologous genes, eya/Eya and dac/DACH/Dac, is also expressed dur-
ing this developmental period. These genes encode nuclear transcription factors that are devoid of DNA-binding
domains but are involved in the protein–protein interactions that control gene expression. Transcriptional com-
plexes, which are products of homeobox-containing genes and nuclear factors, control morphogenesis of the
eye in Drosophila and vertebrates. A similar set of homologous regulatory and nuclear genes controls morpho-
genesis during formation of the ectopic eyes in Drosophila and vertebrates. Molecular biology approaches have
allowed eye development to be examined at the level of developmental mechanisms. It has become evident that
progress in understanding the mechanisms of eye development is due to studies carried out on Drosophila. Sup-
porters of the idea of the polyphyletic origin of the compound and cameral eyes have noted significant differ-
ences in their structure and have failed to find distinct common features in their development. The hypothesis
of the monophyletic origin of eyes has been substantiated by the results of molecular investigations.

Key words: development, eye, Drosophila, vertebrates, gene expression.

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