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A. I. Son, M. Cooper, Y. Sun, R. Zhou; Temporal and Spatial Progression of Cataracts in the Ephrin-A5 Mutant Lens. Invest. Ophthalmol. Vis. Sci. 2010;51(13):4609.
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The crystalline lens requires careful co-ordination of multiple signaling molecules to ensure proper development and maintain transparency. Disruptions in the control of these factors may result in disturbances leading to cataracts. Recently, we and several other studies have shown that the Eph family of receptor tyrosine kinase EphA2 and its ligand ephrin-A5 play an important role in lens development and function. Mutations in both the receptor and the ligand result in cataract formation. To elucidate the cellular mechanisms underlying the development of cataracts, we have identified the timing and location of the lens deficits in ephrin-A5-null mice.
Wild-type and ephrin-A5-null eyes at various ages were fixed, sectioned, and examined using H&E staining. Protein expression and localization were determined using immunohistochemistry and western blot analysis.
Deficiencies in ephrin-A5-null lenses appear as early as P6, with 26% of the mutants developing large intercellular vacuoles in the fiber cell layer around the bow region. By P21, over 70% of ephrin-A5 mutants have developed large vacuoles between the fiber cells. The incidence rate increases to 86% by P180. Gross morphology of lenses during prenatal development appears normal. In contrast, no lens deformities are observed in the wild-type controls. Expression levels of several lens markers, including the crystallins and MIP-26, are also normal in ephrin-A5-null lenses.
These findings indicate that ephrin-A5 activity is indispensible in postnatal lens development. While the absence of ephrin-A5 does not impair initial lens formation, the regulation of fiber cell-cell interaction requires ephrin-A5 activity for maintaining proper lens structure.
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