Functional Analysis of Novel Genes in Eye Development an

National Eye Institute

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Abstract

Through use of genomics and bioinformatics approaches we have identified many novel genes and alternative gene products that are expressed in human and animal model eye tissues. Several of these have been selected for functional analysis to determine their roles in the eye and their implications for normal vision and for disease. These include: 1: Platelet-derived growth factor D (PDGFD) belongs to the PDGF/VEGF family. In the anterior segment PDGFD, it is localized to iris and ciliary body, whereas in the retina, it is restricted to the outer plexiform layer. We have shown that PDGFD has a key role in control of lens growth and that anti-PDGFD strongly inhibits lens epithelial cell proliferation This finding suggests a major in vivo role for PDGFD in the mechanisms of coordinated growth of eye tissues. Intervention in the PDGFD pathway in the eye, perhaps by antibody or blocking peptide, could be useful in the treatment of certain cataracts, including post-operative secondary cataract. A functional promoter of the PDGFD gene has been identified and correctly directs expression of a GFP reporter to eye tissues. A conditional knock out of PDGFD in mouse is under construction. 2: Lengsin is a novel member of the glutamine synthetase (GS) superfamily that is specific for the vertebrate eye lens. It has ATP-binding activity but, so far, no demonstrable enzyme activity. Lengsin is expressed specifically in the layer of terminally differentiating secondary fiber cells in which nuclei and other organelles are lost and cytoskeleton and intracellular junctions are reorganized. Yeast 2-hybrid (Y2H) experiments show that lengsin self associates and also interacts with vimentin, a major component of lens cytoskeleton. This interaction is confirmed by studies with recombinant proteins. Furthermore the distribution of undergoes major changes at the same stage at which lengsin is expressed. Lengsin may be an ancient enzyme that (like some taxon-specific crystallins) has been recruited to a different, structural role in the maturation of lens fiber cells. A knock out model of lengsin is under construction. 3: Retbindin is a novel gene product expressed abundantly in human retina. It has a ligand binding pocket and is a candidate for carotenoid binding. Transgenic mice overexpressing the complete human retbindin gene are being studied using microarrays and spectroscopic techniques to determine the role of this protein.