Figure 2. Actin cytoskeletal organization in lens fiber cells.

A) Diagram of a lens showing orientation of a cross section through the lens equator. B) Cut-away diagram of cross-sections of organized hexagonally packed fiber cells, rotated 90° with respect to A. An individual fiber cell is outlined with a red box. C) Diagram showing the broad sides (blue), short sides (red) and vertices (yellow) of an individual hexagonal fiber cell in cross sectional orientation as in B, red box. D) Diagram of a lens equatorial cross-section. Epithelial cells (Epi) are on the periphery. Each hexagonal fiber cell (red asterisk) has 6 neighboring cells, colored orange, yellow or blue. There is a neighboring cell on each of the 4 short sides (1, 3, 4 and 6) and 2 broad sides (2 and 5). The orange cell (2) is a less mature cell (started elongating after the cell with the asterisk). The yellow cells (1, 3, 4 and 6) are about the same age, and the blue cell (5) is more mature (started elongating before the cell with asterisk). E–I) Phalloidin-stained cross-section showing hexagonal packing of cells as they mature. Red boxed regions in E indicate the approximate locations where (F–I) higher magnification images were obtained. F-actin surrounds the entire fiber cell membrane and is enriched at the vertices and short sides. In cortical fiber cells (F), F-actin staining appears discontinuous, but, as fiber cells mature (G–I), F-actin staining becomes smooth and continuous.