Cell movement and shape are non-random and determined by intracellular, oscillatory rotating waves in Dictyostelium amoebae

Abstract

We present evidence for a mechanism of eukaryotic cell movement. The pseudopodial dynamics and shape of Dictyostelium discoideum amoebae were investigated using computer-supported video microscopy. An examination of the cell periphery by the novel method of serial circular maps revealed explicit, classical wave patterns, which indicate the existence of intrinsic intracellular oscillations. The patterns are generated by the transit of self-organized, super-positioned, harmonic modes of rotating oscillatory waves (ROWS). These waves are probably associated with the dynamics of intracellular actin polymerisation and depolymerisation. A Karhunen-Loève expansion was conducted on one cell during 10 min of locomotion using points each 10 degrees around the cell's boundary. The results show that only 2-3 modes are necessary to describe the most essential features of cell movement and shape. Based on this analysis, a wave model was developed, which accurately simulates the dynamics of cell movement and shape during this time. The model was tested by reconstructing the cell's dynamical form by means of the Karhunen-Loève transform. No difference was detected between this reconstruction and the actual cell outline. Although cell movement and shape have hitherto been viewed as random, our results demonstrate that ROWS determine the spatio-temporal expression of pseudopodia, and consequently govern cell shape and movement, non-randomly.