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L. Fu, E. Stone, E. Pierce; Efemp1/fibulin 3 R345W Point Mutation Knockin Mice Develop RPE Vacuoles and AMD–Like Deposits . Invest. Ophthalmol. Vis. Sci. 2006;47(13):5918.
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© ARVO (1962-2015); The Authors (2016-present)
The dominantly inherited macular degenerations Doyne honeycomb retinal dystrophy (DHRD)/Malattia Leventinese (ML) are caused by a single mutation, Arg–345 to Trp (R345W), in the EFEMP1 (also called Fibulin 3) gene. These conditions are characterized by extensive drusen formation and progressive visual loss, with similarities to age–related macular degeneration (AMD). The similarity in clinical appearance between DHRD/ML and AMD has lead to the suggestion that DHRD/ML could be a good model system for studying AMD. To create a mouse model of DHRD/ML we used gene targeting techniques to create Efemp1–R345W knockin mice.
Efemp1–Neo–R345W mice were generated using standard gene targeting techniques. The floxed neomycin selection cassette was removed by crossing the Efemp1–Neo–R345W mice with universal Cre deleter mice. Heterozygous Efemp1–R345W were intercrossed to generate homozygous (ki/ki) mice. The levels of Efemp1 mRNA and protein were measured by Northern and Western blot analyses. The location of the wild–type and mutant Efemp1 proteins in the retina was evaluated using immunofluorescence techniques. The retina, RPE and Bruch’s membrane were evaluated using light and electron microscopy.
Northern and Western blot analyses demonstrate that the levels of mutant Efemp1–R345W mRNA and protein in homozygous knockin mice are comparable to that of the wild–type protein observed in control animals. The histology and ultrastructure of retinas from homozygous Efemp1–R345W knockin mice were evaluated at 2,6,9 and 12 months of age. Wild–type littermates were used as controls. Vacuoles begin to appear in the RPE cells of the mutant mice at 6 months of age, and increase both in size and extent with age. Homozygous knockin mice develop deposits of wide–spaced collagen within Bruch’s membrane by 2 months of age. By 9 months of age, small deposits of amorphous material were present between Bruch’s membrane and the RPE. By 1 year of age, these deposits had become much larger, and quite extensive, filling large spaces between the basement membrane of the RPE and Bruch’s membrane.
The deposits of wide–spaced collagen and amorphous material detected in the Efemp1–R345W knockin mice are similar in appearance and location to the basal deposits associated with early AMD. These Efemp1–R345W knockin mice may thus be a useful model for investigating the pathogenesis of early macular degeneration.
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