Functional Analysis of Novel Genes in Eye Development and Vision

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Age-related macular degeneration (AMD) is a major cause of vision loss. We have shown that dry AMD is associated with specific deposits of complement factor H and fibulin 3 within domains rich in cholesterol basal to the RPE. Mass spectroscopy has been used to identify further components of complexes that are implicated in formation of protein depositions in AMD. We have developed a cell-culture model for serum-deprivation AMD using RPE-derived cells. In AMD, changes at Bruch's membrane and in the capillary bed are likely to restrict access of serum components to the RPE. We have shown that serum deprivation of RPE cells leads to a marked upregulation of cholesterol synthesis and transport and the accumulation of cholesterol in the RPE. This is strongly reminiscent of the accumulation of cholesterol RPE that we and others have seen in human AMD. Furthermore, serum-deprivation leads to depletion of intracellular zinc, while many zinc-binding proteins are induced. AREDS studies have shown that zinc is protective against AMD. We have extended this work to further define the process in the starved cells and have identified other pathways relevant to AMD. This work has used cell biology and RNAsed methods. Retbindin is a novel protein of retinal photoreceptors. A knockout mouse model shows progressive deficits in visual response and age-related defects in the outer retina that have some striking similarities to some forms of age-related macular degeneration and to glaucoma. Characterization of this model shows many marked similarities to AMD, including deposition of key proteins that are markers for human AMD. In the lens, we have two mouse models for age-related cortical cataract in knockouts for the lens-specific proteins KLPH and Lengsin. We show that KLPH is specific to lens epithelium and is required for normal lens suture formation. Deletion of KLPH leads to complete loss of expression of Clic5 in the lens. In normal lens, Clic5 is localized to the cilium/centrosome complex at the apical tip of the lens fibers. Clic5 is known to be associated with a ciliopathy in the inner ear. We have now published the results of an extensive collaborative study of a targeted deletion model for the miR183C miRNA cluster that has an important role in maturation of sensory neurons, including photoreceptors and auditory hair cells. The deletion has aspects of ciliopathies and provides a possible mouse model for Ushers-like disease.