The development of appropriate animal models of glaucoma is a critical step for understanding the molecular mechanisms of this blinding disease. We are developing a novel mouse model of glaucoma using a transgenic approach. It is now well established that mutations in the myocilin gene may lead to juvenile open-angle glaucoma and in some cases to adult onset glaucoma. The most severe mutations in this gene interfere with secretion of the encoded protein, and may compromise a secretory pathway in the tissues of the eye angle. Our experiments indicate that the presence of severe myocilin mutants prevents the secretion of some proteins (optimedin) but does not significantly effect the secretion of other proteins (alkaline phosphatase). We introduced point mutations in BAC DNA containing full size mouse or human myocilin genes (in collaboration with Dr. S. Sharan, NCI). Four lines of transgenic animals containing the mutated mouse myocilin gene were created. Preliminary results indicate that expression of a mutated mouse protein resulted in a reduced amount of cells in the retinal ganglion cell layer. We continue to study properties of a novel olfactomedin-containing protein, optimedin, which we previously identified. We have shown that optimedin may interact with thioredoxin 2, Hps60, Hsp40 and PIASY as judged by a yeast two-hybrid screen (in collaboration with Dr. K. Mitton, Oakland University). A proximal optimedin gene promoter contains a binding site for the transcription factor Pax6. Pax6 stimulates activity of the optimedin promoter in vitro. Mutations in the Pax6 binding site in the optimedin proximal promoter eliminate stimulatory activity of Pax6. The chicken optimedin gene was characterized and its function in the course of the chicken retina development is under investigation (in collaboration with Dr. R. Adler, John Hopkins University). We demonstrated that several other olfactomedin-containing genes are also expressed in different eye tissues. Possible role of these genes in normal eye development and pathology is under consideration. A novel gene encoding a protein containing PDZ and Lim domains has been identified in the rat eye angle library. This gene is specifically expressed in the corneal epithelial cells as demonstrated by in situ hybridization. The encoded PDZ-Lim protein is associated with stress fibers. Possible interaction of this protein with actinins is under investigation.
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