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M. E. Rayborn, V. L. Bonilha, Y. Li, G. H. Grossman, J. G. Hollyfield, E. L. Berson; Histopathology of the Retina in an Eye Donation From a Patient With an RPE65 Mutation. Invest. Ophthalmol. Vis. Sci. 2010;51(13):4029.
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RPE65 is an enzyme exclusively expressed in the retinal pigment epithelium (RPE) that converts all-trans retinol to the 11-cis form. Mutations in the RPE65 gene are found in some patients with Leber congenital amaurosis. We evaluated the histopathology of a donor eye from a patient with a homozygous missense change Ala132Thr in the RPE65 gene.
Autopsy eyes were obtained from a 56 year old woman who died from metastatic breast cancer. The eyes were fixed in 4% paraformaldehyde and 0.5% glutaraldehyde in phosphate buffer within 13.5 hours postmortem. Small areas from the fundus periphery were processed for electron microscopy and indirect immunofluorescence, using monoclonal antibodies to rhodopsin (mAB B630N) and cone arrestin (mAB 7G6). The content of autofluorescent material was analyzed. The donor eye was compared to a matched normal eye.
The patient had night deficiency and decreased side vision since childhood. At age 51 she had hand motions OD and 20/200 OS, a central island of vision with far peripheral crescents OU, and peripheral bone spicule pigmentation OU. Cone ERGs were barely detectable. Histologic findings revealed a highly disorganized retina with indistinct layers in each quadrant. The RPE layer displayed thinning in some regions of the periphery. Rods were virtually absent in the affected retina. Cones were present in the macula, but were mostly absent from the retinal periphery. Cone synapses were not observed. Autofluorescent material was greatly reduced in the RPE in all areas studied.
This patient with an RPE65 mutation showed an absence of rods and cones in the periphery. In the macula, cone photoreceptors were present, albeit highly disorganized. The lack of autofluorescent material in the RPE suggested that these cells had not been functional in the photoreceptor outer segment renewal process for an extended period of time.
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