Microtubules and actin crosstalk in cell migration and division.

Crosstalk between the actin cytoskeleton and microtubules promotes symmetry break to polarize cells for division, shape changes, and migration. These cellular events are crucial for forming tissues, and drive the metastasis of cancer cells. Rho GTPases mediate the formation of different types of F-actin that confer changes in cortical tension and contraction, and can be regulated by microtubules. For example, central spindle microtubules of the mitotic spindle stimulate RhoA activity to form long, unbranched F-actin that is crosslinked by nonmuscle myosin to form the contractile ring in the equatorial plane of the cell. There is greater cortical tension in this area of the cell in comparison to the poles, where the formation of short, branched F-actin is favored. In migrating cells, growing microtubules that reach into the leading edge promote Rac activation and the formation of short, branched F-actin for lamellipodia formation. A common theme that is emerging in many fields is that feedback can also occur from the cortex to alter microtubule stability. In this manner, cells can dynamically respond to intrinsic or extrinsic cues to ensure that their division plane is always coupled with the segregation of DNA and cell fate determinants, or that they migrate properly to form a tissue.