6th Annual Symposium
Physics of Cancer
Leipzig, Germany
September 7-9, 2015
Invited Talk
Chemotaxis and Actin Oscillations
Eberhard Bodenschatz
Max Planck Institute for Dynamics and Self-Organization, Am Fassberg 17 Göttingen 37077
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Recently, self-oscillations of the cytoskeletal actin have been observed in Dictyostelium, a model system for studying chemotaxis. Here we report experimental results on the self-oscillation mechanism and the role of capping proteins and myosin II. We stimulate cells rapidly and periodically by using photo un-caging of the chemoattractant in a micro-fluidic device and measured the cellular responses. We found that the response amplitude grows with stimulation strength only in a very narrow region of stimulation, after which the response amplitude reaches a plateau. Moreover, the frequency-response is not constant but rather varies with the strength of external stimuli. To understand the underlying mechanism, we analyzed the polymerization and de-polymerization time in the single cell level. Despite of the large cell-to-cell variability, we found that the polymerization time is independent of external stimuli and the de-polymerization time is prolonged as the stimulation strength increases. Our observations explain the underlying machinery of self-oscillations, implying that the oscillation frequency of self-oscillations is determined by the binding time of capping protein. We shall also present the role of noise on the self-oscillatory behavior of cells.

This work is conducted with C. Beta, H. Hsu, J. Negrete, A. Pumir, M.Tarantola, C. Westendorf, V. Zykov and is supported by SFB 937 "Collective behavior of soft and biological matter” and the Max Planck Society.
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