Disruption of lens fiber cell architecture in mice expressing a chimeric AQP0-LTR protein

Aquaporin-0 (AQP0) is the major intrinsic protein of lens fiber cells and the founder member of the water channel gene family. Here we show that disruption of the AQP0 gene by an early transposon (ETn) element results in expression of a chimeric protein, comprised of ~75% AQP0 and ~25% ETn long terminal repeat (LTR) sequence, in the cataract Fraser (Cat(Fr)) mouse lens. Immunoblot analysis showed that mutant AQP0-LTR was similar in mass to wild-type AQP0. However, immunofluorescence microscopy revealed that AQP0-LTR was localized to intracellular membranes rather than to plasma membranes of lens fiber cells. Heterozygous Cat(Fr) lenses were similar in size to wild-type but displayed abnormal regions of translucence and light scattering. Scanning electron microscopy further revealed that mature fiber cells within the core of the heterozygous Cat(Fr) lens failed to stratify into uniform, concentric growth shells, suggesting that the AQP0 water channel facilitates the development of the unique cellular architecture of the crystalline lens.