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C. Hsu, T. Griest, J. Petrash; Lens Defects in Transgenic Mice Expressing a Human R116C A-crystallin Mutant . Invest. Ophthalmol. Vis. Sci. 2003;44(13):2140.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: A previous study showed that an alpha-A crystallin R116C missense mutation was linked to autosomal dominant cataract in a family. Unfortunately, no morphological characteristics and biological mechanism for this mutation have yet been described. In our previous studies, we demonstrated that the R116C mutation is associated with relatively modest reductions in chaperone-like activity and subunit exchange but a much higher increase in membrane binding capacity compared to wild type. In order to explore the mechanism leading to lens defects associated with this mutation, we expressed the R116C αA-crystallin subunit in fiber cells of transgenic mouse lenses. Because the human R116C αA-crystallin mutation leads to an autosomal dominant phenotype, we hypothesize that expression of the mutant subunit on the background of wild type αA and αB crystallins will be a good model for the genetic disorder. Methods: A transgene composed of αA crystallin cDNA fused to the 409 bp αA crystallin promoter was constructed to generate transgenic mice. Founder mice were identified by PCR analysis of tail snip DNA and by RT-PCR of lens mRNA. Each line was further characterized with regard to transgene expression by real-time PCR analysis. By comparing transgene expression levels from five independent R116C mutant lines, an initial selection of low-expression against high-expression animals was carried out. Lens phenotypes were determined at ages up to 6 months. Results: Five founder lines designed for lens-directed expression of the mutant R116C αA-crystallin were generated. In all transgenic lines, a variety of lens defects were observed, including focal opacities localized in the region of the nucleus, subcapsular cataract, abnormal suture, and disruption of the normal alignment of fiber cells. One high-expression line (R116C 8166) had a marked number of transgenic lenses developing a focal opacity localized in the region of the nucleus along with sutural defect. The other high-expression line (R116C 8170) demonstrated a significant disruption of the normal alignment of fiber cells as well as a high incidence of subcapsular cataract. In contrast, both low-expression lines (R116C 8165, R116C 8168) revealed marked sutural defect and disruption of the normal alignment of fiber cells. Conclusions: Expression of the human R116C αA-crystallin transgene leads to a range of structural changes in the lens, including opacities, posterior suture defects and disorganized fiber cells. The transgenic mice expressing R116C αA-crystallin subunit on the background of wild type αA and αB crystallins provide a good model for this genetic mutation in humans.
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