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 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. Analysis of gene expression in the cell model has led to the discovery of unexpected genes that are implicated in the hydroxyapatite mineralization that occurs at an around Bruch's membrane in AMD. We have shown that siRNA knockdown of target genes inhibits calcification. This has therapeutic potential. 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. 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.