A Model for a Correlated Random Walk Based on the Ordered Extension of Pseudopodia
Figure 7
Movement of a mutant with irregular shape.
Pseudopod formation and trajectories were recorded for 5h starved wild type and mutant ddia2-null cells. For the next pseudopod we measured the angle φ and distance d relative to the current pseudopod, the angle αt of the tangent relative to the current pseudopod and the angle β of the pseudopod relative to the tangent. A. The data show the means and SD measured for 312 and 289 pseudopodia from wild type and ddia2-null cells, respectively. The means are not significantly different between wild type and ddia2-null cells, but the SD σφ and σt are significantly larger for ddia2-null compared to wild type (Chi-square, P<0.0001); the SD σd and σβ are not significantly different. B. The shape parameter Ψ was determined at the moment of pseudopod extension. Bars show the frequency distributions for 312 wild type and 289 ddia2-null cells. Data points show σφ, the SD of φ. Linear regression analysis of all data point yields σφ. = 37.6Ψ+22.8; R2 = 0.965. C. Pictures showing three representative cells; numbers indicate the measured values of Ψ. Mutant ddia2-null has an irregular star-like shape, while wild-type cells are smoother and more spherical. Each diagram shows a cell with a pseudopod (dark grey area); the small lines indicate the direction of pseudopodia that emerge by pseudopod splitting perpendicular to the surface. Due to the irregular shape, pseudopodia extending by ddia2-null cells exhibit more angular variation. D. Displacement of wild type and ddia2-null cells during 15 minutes.