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JR Kuszak, KJ Al-Ghoul, RK Zoltoski, A Shiels; Aquaporin-0 Deficiency Impairs the Optical Quality of the Mouse Crystalline Lens . Invest. Ophthalmol. Vis. Sci. 2002;43(13):1918.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: Aquaporin-0 (AQP0), a water transport channel protein, is the major intrinsic protein of lens fiber cells. The purpose of this study was to quantify the optical quality (sharpness of focus) of lenses from mice deficient in the gene for AQP0 (Aqp0+/-, Aqp0-/-). Methods: Aqp0+/- and Aqp0-/- knockout mice were generated from a library of gene-trap embryo stem cells. Sequence analysis showed that the gene-trap vector had inserted into the first exon of Aqp0 causing a null mutation as determined by RNA blotting and immunochemistry. Within five minutes of sacrifice, the average back focal length (BFL in millimeters [mm]), a measure of longitudinal spherical aberration, and back focal length variability (BFLV in mm), a measure of focusing power as a function of internal structure, were quantified in lenses from 5-6 month old wild type (WT, n = 11) and Aqp0+/- (n = 7) mice using a ScantoxTM In Vitro Assay System generously provided by Harvard Apparatus Inc. (Holliston, MA). Comparable analysis of age-matched Aqp0-/- lenses, were not conducted as they were almost totally opaque. The structure of laser scanned lenses were subsequently assessed by light, transmission and scanning electron microscopy. Results: The average BFL and BFLV of WT lenses was respectively, 1.1395±0.058 and 0.1748±0.08. In contrast, the average BFL and BFLV of Aqp0+/- lenses was respectively, 1.8320±0.148 and 0.2330±0.017. Results of statistical analysis (t-tests for independent groups of samples) confirmed that the sharpness of focus was significantly degraded (p ≤ 0.05) in Aqp0+/-lenses. WT lenses had crescent and hexagonally shaped fibers arranged in concentric growth shells (GSs), ordered radial cell columns (RCCs), and fiber ends that formed normal Y sutures. Aqp0+/- lenses had non-crescent and variably polygonal shaped fibers arranged in non-concentric GSs, disordered RCCs, and with fiber ends that failed to form sutures. Aqp0-/- lenses were composed of cells lacking any semblance of normal fiber shape, arrangement into GSs, RCCs or sutures. Conclusion: These findings show that heterozygous loss of Aqp0 is sufficient to cause malformation of a mouse lens that renders it translucent and eventually triggers cataractogenesis.
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