Fig. 1

A. Schematic illustration of major cytoskeletal components in motile cells. Lamellipodia and focal adhesions are located in the front of motile cells. The cross-hatched region represents the actin framework in lamellipodia. F-actin is present throughout the cell body, which interacts with myosin to generate traction force. Aging focal adhesions in the rear are disassembled to allow for cell retraction. Intermediate filaments surround the nucleus (N), some of which associate with focal adhesions in lamellipodia. Intermediate filaments modulate focal adhesion dynamics and cell contraction. Microtubules are polarized along the direction of migration and accumulate toward the front of the cell. Microtubule organizing centers (MOTCs) are localized in the front of the nucleus. Through their roles in mechanics, trafficking and signaling, polarized microtubules facilitate all important events leading to cell migration