Figure 10

Modes of state transitions in the actin-phosphoinositide system of the cell cortex. A, growth and coalescence of patches. This mechanism has been proposed by Gamba et al. [29] for the accumulation of PIP3 at the front of chemotaxing cells. (Adopted from [30]). B, state transition initiated as a rare event in a field of damped fluctuations. Once initiated, the state transition progresses as a wave, as demonstrated for the transition of actin organization (Figure 5). C, extension of a gradient linked to the border of a persisting area. This mode of expansion of a coherent area applies to the formation of PTEN gradients (Figure 6). D, transformation of the pattern in (C) to proposed PTEN oscillations in a chemotaxing cell. The border of the PTEN-rich membrane area (dark) is supposed to be asymmetric and to suppress actin polymerization and pseudopod protrusion alternately at the right (1, 2) or left (3, 4) side of the front region.