STUDY OF THE REGULATION OF SIX3 AND SIX6 EXPRESSION: AN APPROACH FOR THE IDENTIFICATION OF POTENTIAL CANDIDATE GENES FOR ANOPHTHALMIA MICROPHTHALMIA AND COLOBOMA.

Microphthalmia, Anopthalmia and Coloboma (MAC) are inherited eye diseases that arise in the embryos during pregnancy and are characterised by variable phenotypes as the nearly complete absence or the reduction of the eye size. Although the molecular bases of these defects in humans are largely unknown, surprising advances have been made in recent years with the discovery that some MAC patients have genetic code alterations in two genes, Six3 and Six6, considered as key elements in eye and brain development. Nevertheless, the heterogeneity of these pathologies predicts that several additional unknown genes might be responsible for the MAC phenotypes. Based on the hypothesis that the proteins that regulate (transcriptional factors) Six3 and Six6 expression are directly involved in the eye development, we plan to identify and characterize these proteins and study their possible relationship with MAC diseases. To achieve this goal we will first characterize the genomic regulatory sequence of six3 and six6 in distinct vertebrate species by combing bioinformatic analysis with genetic manipulations in simple vertebrate model systems (i.e. chick and fish), where eye development is comparable to that of human. These sequences will allow us to isolate the binding transcription factors, using experimental approaches based on DNA-protein interactions. The manipulations of the expression of these identified transcription factors in chick and fish embryos will allow us to study their relationship with Six3 and Six6 activities. At the same time, they may lead to phenotypic consequences similar or more severe than those proposed for Six3 and Six6, allowing us to identify several additional genes as molecular causes of the MAC diseases.