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J.G. Hollyfield, V.L. Bonilha; Polarized Distribution of RPE Membrane Markers in Bone Spicules Pigment Present in RP Donor Eyes . Invest. Ophthalmol. Vis. Sci. 2005;46(13):3050.
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Purpose:A fundus hallmark in retinitis pigmentosa (RP) is the presence of bone spicule pigment. These structures are formed by the migration of retinal pigment epithelium (RPE) cells to perivascular sites in the inner retina. Very little is available in the literature about the maintenance of polarity markers in these RPE cells that have withdrawn from the from the RPE monolayer. The present study analyzes the distribution of several well–known plasma membrane RPE proteins. Methods: The tissues used are from the FFB Eye Donor Collection maintained in the Cole Eye Institute. Tissues were fixed in 4% paraformaldehyde and 0.5% glutaraldehyde in phosphate buffer. The globes were slit through the pars plana; after removal of the anterior segments the fundus was photographed and the tissue transferred to 2% paraformaldehyde prepared in PBS. The postmortem time varied between 7.5 to 21.5 hours. Cryostat tissue sections were studied by indirect immunofluorescence and confocal microscopy, using well–characterized antibodies to several established apical (ezrin, vitronectin receptor) and basolateral RPE markers (ß–catenin, Glut–1 transporter and laminin, among others). The RP eyes were compared to compatible normal donor eye. Results: Ezrin, an actin binding protein, was present on the apical surface of the translocated RPE cells, opposite to the laminin basal marker in the bone spicules. On the other hand, the vitronectin receptor co–distributed along the basal surface of the translocated RPE cells. Glut–1 and &ß–catenin were both localized to the lateral membrane of the translocated RPE cells. Conclusions: The immunocytochemical data obtained suggests that translocated RPE cells keep the polarized distribution of their plasma membrane proteins. However, the re–distribution of some proteins such as the vitronectin receptor to the basal surface is observed. This re–distribution of some of the plasma membrane proteins must be correlated to their function in the bone spicules in retina.
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