Figure 9.

Hypothesized mechanism of spontaneous polarity change resulting in cell turning behavior. (a) Protrusion at the cell front. (b) Protrusion at the cell front together with retraction at the cell rear. A single ventral SF could be connected or fused from dorsal SFs and arc SFs in the intermediate region of the cell (green line). (c) End of retraction at the cell rear. The upper single ventral SF is the SF formed in (b), whereas the lower 2 ventral SFs are those in the rear region in (b), which could become a single ventral SF subsequently (dotted arrow). (d) End of the cyclic process of cell migration. Possible protrusion site of the cell is shown by the red winding lines, which is perpendicular to that in the initial direction of protrusion. This means that the cell could change its polarity, resulting in cell turning behavior.