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K. Varadaraj, S.S. Kumari, A. Shiels, R.T. Mathias; Aquaporin 1 Rescue Aquaporin 0 Function in the Aquaporin 0 Knockout Mouse and Restore Lens Transparency and Homeostasis . Invest. Ophthalmol. Vis. Sci. 2004;45(13):3992.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: We have previously shown that AQP0 is the main source of membrane water permeability in lens fiber cells. Natural mutations in AQP0 as well as knockout of AQP0 resulted in lens cataract. The purpose of this investigation was to determine whether lens–specific expression of a closely related aquaporin, namely AQP1, can restore homeostasis and improve transparency in AQP0 heterozygous knockout (AQP0+/–) mouse lenses. Methods: . Transgenic mice that express AQP1 in lens fiber cells were generated as follows. Human AQP1 cDNA was subcloned into an EGFP expression vector. A 2.2 kb fragment containing alpha–A–crystallin promoter–AQP1–EGFP–SV40pA region was microinjected into the male pronucleus of single–cell embryos derived from inbred FVB mice. The embryos were implanted into pseudopregnant CD1 females and pups were born. To identify the heterozygous transgenic founder mice, these pups were genotyped. Positive AQP1 expression in the lenses of potential founders was confirmed using the Dark Reader special light and filter sets, immunostaining, and Western blotting. The founders were bred to generate homozygous transgenic (Tg–AQP1+/+) mice. 2. To generate the double heterozygous transgenic model (Tg–AQP1+/– /AQP0+/–), Tg–AQP1+/+ mice were crossed with AQP0–/– mice. Results: Transgenic mice expressing AQP1 in the fiber cells appeared normal. AQP0+/– mouse lenses had compromised homeostasis as demonstrated by loss of transparency. A considerable improvement in transparency was observed in Tg–AQP1+/–/AQP0+/– over the AQP0+/– lenses. Conclusions: These results suggest that a critical role of AQP0 is to provide a high level of membrane water permeability in fiber cells, and this role can be subsumed by AQP1. However, the AQP0+/– lenses still express a considerable amount of AQP0 protein, so there may be other roles for AQP0 that do not depend so critically on the amount of protein.
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