TY  - JOUR
A1  - Beta, Carsten
A1  - Bodenschatz, Eberhard
T1  - Microfluidic tools for quantitative studies of eukaryotic chemotaxis
JF  - European journal of cell biology
N2  - Over the past decade, microfluidic techniques have been established as a versatile platform to perform live cell experiments under well-controlled conditions. To investigate the directional responses of cells, stable concentration profiles of chemotactic factors can be generated in microfluidic gradient mixers that provide a high degree of spatial control. However, the times for built-up and switching of gradient profiles are in general too slow to resolve the intracellular protein translocation events of directional sensing of eukaryotes. Here, we review an example of a conventional microfluidic gradient mixer as well as the novel flow photolysis technique that achieves an increased temporal resolution by combining the photo-activation of caged compounds with the advantages of microfluidic chambers.
KW  - Eukaryotic chemotaxis
KW  - Dictyostelium discoideum
KW  - Microfluidics
KW  - Caged compounds
KW  - Numerical simulations
Y1  - 2011
U6  - https://doi.org/10.1016/j.ejcb.2011.05.006
SN  - 0171-9335
VL  - 90
IS  - 10
SP  - 811
EP  - 816
PB  - Elsevier
CY  - Jena
ER  - 
TY  - JOUR
A1  - Westendorf, Christian
A1  - Negrete, Jose
A1  - Bae, Albert J.
A1  - Sandmann, Rabea
A1  - Bodenschatz, Eberhard
A1  - Beta, Carsten
T1  - Actin cytoskeleton of chemotactic amoebae operates close to the onset of oscillations
JF  - Proceedings of the National Academy of Sciences of the United States of America
N2  - The rapid reorganization of the actin cytoskeleton in response to external stimuli is an essential property of many motile eukaryotic cells. Here, we report evidence that the actin machinery of chemotactic Dictyostelium cells operates close to an oscillatory instability. When averaging the actin response of many cells to a short pulse of the chemoattractant cAMP, we observed a transient accumulation of cortical actin reminiscent of a damped oscillation. At the single-cell level, however, the response dynamics ranged from short, strongly damped responses to slowly decaying, weakly damped oscillations. Furthermore, in a small subpopulation, we observed self-sustained oscillations in the cortical F-actin concentration. To substantiate that an oscillatory mechanism governs the actin dynamics in these cells, we systematically exposed a large number of cells to periodic pulse trains of different frequencies. Our results indicate a resonance peak at a stimulation period of around 20 s. We propose a delayed feedback model that explains our experimental findings based on a time-delay in the regulatory network of the actin system. To test the model, we performed stimulation experiments with cells that express GFP-tagged fusion proteins of Coronin and actin-interacting protein 1, as well as knockout mutants that lack Coronin and actin-interacting protein 1. These actin-binding proteins enhance the disassembly of actin filaments and thus allow us to estimate the delay time in the regulatory feedback loop. Based on this independent estimate, our model predicts an intrinsic period of 20 s, which agrees with the resonance observed in our periodic stimulation experiments.
KW  - Dictyostelium discoideum
KW  - microfluidics
KW  - caged cAMP
KW  - delay-differential equation
Y1  - 2013
U6  - https://doi.org/10.1073/pnas.1216629110
SN  - 0027-8424
VL  - 110
IS  - 10
SP  - 3853
EP  - 3858
PB  - National Acad. of Sciences
CY  - Washington
ER  -