The lens, like any other tissue, is dependent upon the cytoskeleton for its function. There are now a number of examples of mutated or overexpressed cytoskeletal proteins that have been shown to be the genetic basis of cataract, underlining the importance of the cytoskeleton to cell shape, intracellular organisation, and compartmentalisation in the lens. In other cell systems, the cytoskeleton enables the cell to maintain and diversify the internal complexities required for specialised cellular functions. In the lens, this requires specialised cell-cell interactions that allow adjacent plasma membranes to be closely apposed or interdigitated over most of their surface. Differentiation requires the programmed elongation of lens fiber cells and, by inference, the directed traffic of organelles, vesicles, and other cargoes in the highly elongated fiber cell. Finally, the lens is highly specialised in the maintenance and use of stable proteins, of which the cytoskeleton is but one example. Evolution has dictated the choice of the proteins and their structures to ensure that the lens efficiently refracts light onto the retina, and our task as cell biologists is to unravel this rich tapestry and to discover the contribution of the cytoskeleton to the function of this highly specialised tissue.
Major Components of the Lenticular Cytoskeleton
The lens, like all other tissues, possesses microtubules, microfilaments, and intermediate filaments, the three main cytoskeletal elements of most eukaryotic cells. These structural filaments in isolation are ineffective, as it is the linking, the attachment, and the transiently associating proteins that give the cytoskeleton functionality.