Reduced survival of lens epithelial cells in the α A - crystallin - knockout mouse

α-Crystallin is the major component of vertebrate eye lenses and constitutes approximately a third of the lens fiber cell proteins (Horwitz, 2000). It is also expressed at lower levels in lens epithelial cells. α-Crystallin is a hetero-oligomeric complex of two closely related polypeptides, αA and αB, present in 3:1 stoichiometry in lens fibers. The two subunits have chaperone activity, and are members of the small heat shock protein (HSP) αA and αB transcripts are detected during the early stages of lens development (Robinson and Overbeek, 1996), and a marked increase in expression of the proteins accompanies differentiation. Both have been detected in tissues outside the lens, but αA is more lens-specific than αB αA and αB are important for lens transparency and refraction. However, their ability to prevent the aggregation of denaturing proteins in vitro suggests that they may act as a 'sink' for age-related denatured proteins in the lens (Horwitz, 2000). The enhanced resistance of cells expressing these proteins to stress conditions suggests that αA and αB have