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B. L. Patek, R. Grebe, G. A. Lutty, J. S. Zigler, Jr., E. F. Wawrousek, D. Sinha; Transgenic Mice Overexpressing Mutant βA3/A1-Crystallin in Astrocytes Show Abnormalities in Retinal Pigment Epithelial (RPE) Cells With Increasing Age. Invest. Ophthalmol. Vis. Sci. 2010;51(13):5956.
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To better understand the function of βA3/A1-crystallin in astrocytes.
We have used both wildtype and Nuc1 mutant βA3/A1-crystallin cDNA constructs to generate transgenic mice. In these mice, the human GFAP promoter directs overexpression of either the mutant or wildtype protein, specifically in astrocytes. Confocal microscopy of retinal flatmounts, immunolabelled with GFAP and Isolectin-B4, were used to compare the patterning of astrocytes and blood vessels in the developing retina. Structural changes in the RPE were assessed using transmission electron microscopy.
We have established mutant and wild type βA3/A1-crystallin transgenic mouse lines. Western blot analysis clearly shows robust expression of thetransgene in mouse retina. Astrocytes expressing the mutant βA3/A1-crystallin protein show bundle-like structures with abnormal patterning and short, thickened processes compared to the compact stellate structure of astrocytes that are overexpressing the wildtype βA3/A1-crystallin protein. Astrocytes overexpressing the wildtype βA3/A1-crystallin protein continue to produce the typical honeycomb-like network in the retina. The patterning of the primary blood vessels of the retina in transgenic mice expressing the mutant βA3/A1-crystallin is also abnormal. In adult mice (one year old) expressing the mutant protein in astrocytes, Bruch’s membrane is thickened, with a more heterogeneous composition. Clearance of photoreceptor shed discs also appears to be abnormal.
Transgenic mice expressing the βA3/A1-crystallin mutant protein specifically in astrocytes, show changes in the vascular remodeling of the retina. Later in life, the RPE-Bruch’s complex is affected, perhaps resulting from an inflammatory response stimulated by the abnormal astrocytes in the neural retina. We provide novel evidence that abnormalities in retinal astrocytes may lead to pathological changes in RPE.
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