Dynein drives nuclear rotation during forward progression of motile fibroblasts.

During directed cell migration, the movement of the nucleus is coupled to the forward progression of the cell. The microtubule motor cytoplasmic dynein is required for both cell polarization and cell motility. Here, we investigate the mechanism by which dynein contributes to directed migration. Knockdown of dynein slows protrusion of the leading edge and causes defects in nuclear movements. The velocity of nuclear migration was decreased in dynein knockdown cells, and nuclei were mislocalized to the rear of motile cells. In control cells, we observed that wounding the monolayer stimulated a dramatic induction of nuclear rotations at the wound edge, reaching velocities up to 8.5 degrees/minute. These nuclear rotations were significantly inhibited in dynein knockdown cells. Surprisingly, centrosomes do not rotate in concert with the nucleus; instead, the centrosome remains stably positioned between the nucleus and the leading edge. Together, these results suggest that dynein contributes to migration in two ways: (1) maintaining centrosome centrality by tethering microtubule plus ends at the cortex; and (2) maintaining nuclear centrality by asserting force directly on the nucleus.