Purchase this article with an account.
G. A. Zampighi, L. M. Zampighi, C. Schietroma; The 3D-Structure of the Lens Fiber Cell Cytoplasm as Determined by Conical Tomography. Invest. Ophthalmol. Vis. Sci. 2009;50(13):5787.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
To analyze the structural organization of the fiber cell cytoplasm and determine how the "beaded" filaments of the cytoskeleton interact with soluble proteins and the plasma membrane.
We studied rat lens cortical fibers before and after the extraction of "soluble" crystallins ("ghosts"). Both unextracted lenses and ghosts where prepared for thin section electron microscopy and tomographic series in conical geometry were collected at 55° tilt and by 5° rotations. The projections were aligned using fiduciary points and 3D-maps were reconstructed with the weighted back projection algorithm and refined by projection matching. Semiautomatic density segmentation based on the 3D-watershed algorithm was used to analyze the maps.
In developing fibers, the cytoplasm was comprised of interacting networks of 10-nm diameter intermediate filaments and "beaded" filaments. These networks formed a "clustered matrix" that interacted with crystallins and the plasma membrane. In mature fibers, the clustered matrix was comprised of filaments measuring ~6 nm in diameter, bent at 110-120° angles and studded with cube-shaped particles ("beaded" filaments). The particles measured a=14±2, b=13±2, c=10±2.4 nm (mean ± SD, n=30) and were spaced 27.5±2.4 nm apart (n=8). The "beaded" filaments crossed at nearly perpendicular angles to form the clustered matrix, thus confining the soluble crystallins into separate clusters. The cube-shaped particles anchored the matrix to the plasma membrane.
In the lens fiber cytoplasm, a 3D-matrix comprised of different types of cytoskeleton filaments organizes the soluble crystallins in domains and associates with the plasma membrane. Loss of either function would likely play a role in cataract formation.
This PDF is available to Subscribers Only