This project studies the regulation of expression of genes encoding lens fiber membrane channel proteins, which are essential for maintaining the transparency and correct refractive index of the lens. We are presently focusing on the regulation of expression of the gene encoding MIP, the major intrinsic protein of the lens fiber membrane, that is specifically expressed in the ocular lens fibers and belongs to an ancient family of transmembrane channel proteins. We have continued studying the transcriptional regulation of the MIP gene. The Sp family of transcription factors is involved in the regulation of transcription of the MIP gene. Sp3 interacts with a regulatory element of the MIP promoter, required for activation in the lens. We also studied the expression of the transcription factors AP2. We found that the gene encoding the transcription factor AP2 is expressed in the lens epithelia and that a novel splice variant, which lacks part of the activation domain, is present in the lens. In collaboration with Drs. Dwight Stambolian and Jack Favor we have characterized at the molecular level the Hfi mouse genetic cataract, which localizes to the MIP gene locus. We found that a deletion in the exon2/intron3 junction of the MIP gene results in deletion of exon 2 in the resultant transcript, produced by an exon skipping mechanism. MIP knock-out mouse experiments that we are conducting in collaboration with Dr. Anthony Wynshaw-Boris, will allow us to understand the role of MIP gene expression in lens transparency.
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