Fig. 9. Model of myosin II function in cortical stability. Cross hatching indicates cross-linking function of myosin II in a cortical acto-myosin complex. Arrows indicate direction of cell movement and downward pressure resultant from resistance to deformation of agarose. (A,B) Deformation of agarose and flattening of cell that occurs during wild-type cell migration under agarose. (C,D) Lack of cross-linking occurring as a result of loss of myosin heavy chain function. (C) The ability of the cell to extend a protrusion under the agarose similar to wild-type cells. In D, although the cell was able to retract its midbody and subsequently migrate; downward pressure imposed upon the cell by the agarose results in the uropods not being withdrawn.