The cytoskeletal network is of vital importance in proper cellular functions. Microtubules, one of the major cytoskeletal components, interact with various associated proteins and generate hierarchical network structures spanning tens of micrometers to millimeters. The network dynamically varies during a cell cycle according to physiological roles in the cell.

To gain the integrative perspectives of network formation and its dynamics, we have extensively surveyed the pattern formation of microtubule-motor mixtures in vitro and found the bundling and sliding of microtubules are the key to pattern formation.

This cover image, acquired with a confocal microscope, shows the network spontaneously formed in the mixture of microtubules (magenta) and a member of the kinesin-5 family, Eg5 (cyan). Radial microtubule structures (asters) are formed through the clustering of plus-ends of microtubules by Eg5, and these asters form a global network spanning up to several millimeters. The sliding activity of Eg5 finally induces the contraction of the network.

The experimental system exhibited various distinct spatiotemporal patterns according to mixing ratios of motors to microtubules. A coarse-grained numerical model we developed can explain these experimentally observed dynamics and demonstrate how bundling and sliding activities of motors determined these spatiotemporal dynamics. Now, together with the model, our system will provide a beneficial platform for the investigation of dynamics and mechanical properties of cytoskeletal architecture.

- Takayuki Torisawa, Daisuke Taniguchi, Shuji Ishihara and Kazuhiro Oiwa