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Three-Dimensional Organization of Actin Filaments During Cytokinesis

Fishkind and Wang, J. Cell Biol.123:837-848 (1993)

While it is known that actin-myosin interactions provide the contractile forces for cytokinesis, the exact mechanism remains poorly understood. Important clues may be obtained by examining the detailed organization of actin filaments in different types of a dividing cell, To this end Normal Rat Kidney cells were fixed and stained with fluorescent phalloidin and imaged with digital optical sectioning microscopy. Image stacks were then processed with nearest neighbor deconvolution and reconstructed into perspective views at different angles.

Reconstructed Views of Actin Filament Organization during Cytokinesis

Equatorial organization of actin filaments is found primarily on the bottom cortex, where ingression is constrained by cell-substrate adhesions. The top cortex, where ingression takes place actively, shows only a limited organization of actin filaments. No "purse string" around the equator can be found, while many actin filament bundles in the region flanking the equator are oriented along the long axis of the cell. This organization suggests that the purse string model of cleavage may not apply to cultured mammalian cells and that ripping forces along opposite directions of the long axis may play a role. The movies show rotating views of two different cells



Organization of Actin Filaments - Whole Cell View

To increase the clarity and facility the comparison, reconstructions were performed using the complete stack (top), the top half of the slices (middle), or the bottom half (bottom).

Organization of Actin Filaments - Top Half


Organization of Actin Filaments - Bottom Half