Drusen and AMD: sub-type isolation and characterization

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DESCRIPTION (provided by applicant): The broad, long-term objective of this application is to define in molecular terms the linkage between the accumulation of soft drusen below the retinal pigment epithelium (RPE) in the macula and the increased risk of developing age-related macular degeneration (AMD). The presence of soft drusen in the macula is the hallmark risk factor for developing AMD. Surprisingly little is known of the composition or origin of drusen. To this end a novel method for drusen isolation has been developed that allows the collection of microgram quantities of drusen from donor eye tissue. At the time of isolation, different drusen sub-types can be identified and separated for use in studies that will characterize their molecular composition. The diagnostic utility of drusen in AMD can be likened to that of blood levels of cholesterol in atherosclerosis. The presence and abundance of drusen, like the level of cholesterol in the blood, indicates the degree to which a patient is at risk for developing the disease. Because of the relationship of drusen and AMD, understanding the composition of different drusen sub-types will provide important information on possible pathways that are causally involved in drusen development. Novel proteins or common modifications of proteins present in drusen, should provide insight as to potential drug targets of therapeutic agents to treat AMD. The current application is focused on exploiting this drusen isolation procedure to define the molecular composition, distribution and cellular origin of drusen sub-types in normal and AMD tissues. The three specific aims are: (1) To test the hypothesis that different sub-populations of drusen can be isolated from donor eye tissue. (hard vs. soft, foveal vs. peripheral, old vs. older, spherical vs. flat, amber vs. clear, opaque vs. granular, etc.). (2) To test the hypothesis that different structural features of drusen sub-populations reflect different molecular composition (light microscopy, histochemistry, electron microscopy, SDS/PAGE, Western blotting, mass spectrometry). (3) To test the hypothesis that some of the molecules present in drusen are novel and are not found in Bruch's membrane.