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VI Shestopalov, S Bassnett; Development of the Lens Core Syncytium . Invest. Ophthalmol. Vis. Sci. 2002;43(13):4631.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: Fiber cells in the core region of the lens obtain nutrients via abundant gap junctions, coupling them to superficial cells in the cortex. Recently, however, we obtained evidence for the existence of an additional intercellular communication pathway in embryonic chicken lenses. This pathway is permeable to cytosolic proteins and is thus distinct from gap junctions. Here we present evidence for a similar syncytial organization in the mouse lens. Methods: We utilized GFP5Nagy, a transgenic mouse line in which expression of green fluorescent protein (GFP) is X-linked, to generate mice with GFP mosaic lenses. We used confocal microscopy and 3-D reconstructions of the lens tissue to visualize the cellular distribution of GFP during development. Results: In hemizygous female mice, GFP expression was observed in approximately 50% of lens cells. In embryonic lenses (<E15) GFP expressing fiber cells were scattered throughout the lens core, interspersed with non-expressing cells. However, at later embryonic stages, and in adult mice, this mosaic expression pattern was replaced in the lens core by a region of uniform fluorescence. Within this zone all fiber cells contained diffuse GFP fluorescence. In contrast, the mosaic expression pattern was sustained in newly differentiated fibers at the periphery. Once formed, the core syncytium persisted throughout embryonic development and into adulthood. We measured the diameter of the central uniform zone and determined that it increased in size as the lens grew. Conversely, the thickness of the mosaic layer of cells in the outer cortex decreased to 80-100 microns in adult mice. Conclusion: We hypothesize that on or about E15 the lens core becomes organized into a true syncytium, allowing GFP to diffuse between expressing and non-expressing cells. The syncytium continues to expand during adulthood indicating that it is not a purely embryonic phenomenon. Together with our previous observations on the chicken lens, the current experiments suggest that the syncytial organization of the lens core may be a universal feature of the vertebrate lens.
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