Figure 3. Asymmetric myosin activity drives persistent cell turning.

(A) A sample image of myosin regulatory light chain-YFP distribution in a turning cell with a counter-clockwise path (magenta line). Note that the myosin II density is higher on the outer side of the turning cell.

(B) Time series of the myosin density in the outer wing, m_o (green), and inner wing, m_i (orange), of the cell from panel A, showing consistently higher myosin on the outer side of this turning cell over time. Note that the vertical axis does not start at 0.

(C) The relative concentration of myosin II heavy chain as determined by immunofluorescence on the outer and inner sides of cells that were imaged live prior to fixation (vertical axis), plotted against the cell’s path curvature prior to fixation (horizontal axis). Note that cells with a greater degree of turning had an increase in the asymmetry of myosin II localization, correlation coefficient is 0.67 for 15 cells.

(D) The distribution of calculated auto-correlation of angular velocity with a lag of 10 minutes was calculated for control cells (left/blue) and cells treated with the myosin-II inhibitor blebbistatin (right/orange). Inhibition of myosin-II drastically reduced the number of cells exhibiting persistent turns.

(E) The trajectories of cells exposed to an electric field of 5 V/cm under control conditions (top) and with inhibition of myosin II (bottom). All cells migrate towards the cathode on the right, but only cells under control conditions have a periodic overshoot of a straight trajectory suggestive of persistence of a previous angular velocity.