Figure 7.
Hypothetical model for organization of cortical MT arrays. Top panel, a strongly anchored MT, and middle panel, a partially detached MT (gray region). Yellow shading indicates the area of exploration, which is increased by the partial detachment. Blue outline denotes the surface area available for bundle formation. Red asterisk indicates initial contact points. Partial detachment allows exploration of a larger volume with a greater surface area, and the MT therefore captures and bundles with another MT. Bottom panel, an example of zippering from an initial contact point. Cortical detachment permits initial MT–MT contact points to propagate as MTs zipper together in a polymerization-independent manner. We propose that these processes occur in all cells, but are enhanced in the absence of CLASP. In this way, CLASP indirectly affects MT–MT interactions via maintaining strong association of MTs along their length with the cell cortex. The fact that MTs remain partially attached in the absence of CLASP indicates the presence of other cortical anchoring factors.