Fig. 3. A typical movement of beads around a migrating wild-type cell. The gray and black lines represent a superimposed image of two cell contours at 0 seconds and 21 seconds in a, at 21 seconds and 42 seconds in b, at 42 seconds and 63 seconds in c, at 63 seconds and 84 seconds in d, respectively. Large closed arrows represent the direction of cell migration. The gray and black dots represent positions of the beads at 0 seconds and 21 seconds in a, at 21 seconds and 42 seconds in b, at 42 seconds and 63 seconds in c, at 63 seconds and 84 seconds in d, respectively. The crosses represent the original position of beads before the cells were placed on the silicone substrate. Small open arrows of red, green and blue represent the vectors of bead movements around anterior, side and posterior regions, respectively. Black open arrows represent the bead movement underneath the cell body. The length of the open arrows is twice as long as the displacement of the beads. Between 0 and 42 seconds (a,b), the beads around the anterior and posterior regions moved toward the cell body, and those around the side region moved away from the cell. Subsequently, between 42 and 84 seconds (c,d), the bead movements were reversed. Insets in b and d, schematic representations of the directions of the movement of beads surrounding the cell are shown. Large black arrows represent the direction of the cell migration. Closed arrows of red, green and blue represent the directions of bead movements around anterior, side and posterior regions, respectively. The pattern of bead movement between 0 and 42 seconds is referred to as pattern 1 (inset of 3b) and the pattern between 42 and 84 seconds as pattern 2 (inset of 3d). The beads underneath the cell body occasionally moved in a different manner and direction. In many cases, this feature could not be expressed in these figures because the directional change occurred in a short time. The stiffness of this silicone substrate is 5.97 nN/µm. Bar, 5 µm.