TY  - JOUR
A1  - Negrete, Jose
A1  - Pumir, Alain
A1  - Hsu, Hsin-Fang
A1  - Westendorf, Christian
A1  - Tarantola, Marco
A1  - Beta, Carsten
A1  - Bodenschatz, Eberhard
T1  - Noisy Oscillations in the Actin Cytoskeleton of Chemotactic Amoeba
JF  - Physical review letters
N2  - Biological systems with their complex biochemical networks are known to be intrinsically noisy. Here we investigate the dynamics of actin polymerization of amoeboid cells, which are close to the onset of oscillations. We show that the large phenotypic variability in the polymerization dynamics can be accurately captured by a generic nonlinear oscillator model in the presence of noise. We determine the relative role of the noise with a single dimensionless, experimentally accessible parameter, thus providing a quantitative description of the variability in a population of cells. Our approach, which rests on a generic description of a system close to a Hopf bifurcation and includes the effect of noise, can characterize the dynamics of a large class of noisy systems close to an oscillatory instability.
Y1  - 2016
U6  - https://doi.org/10.1103/PhysRevLett.117.148102
SN  - 0031-9007
SN  - 1079-7114
VL  - 117
PB  - American Physical Society
CY  - College Park
ER  - 
TY  - GEN
A1  - Westendorf, Christian
A1  - Bae, Albert J.
A1  - Erlenkamper, Christoph
A1  - Galland, Edouard
A1  - Franck, Carl
A1  - Bodenschatz, Eberhard
A1  - Beta, Carsten
T1  - Live cell flattening
BT  - traditional and novel approaches
T2  - Postprints der Universität Potsdam : Mathematisch Naturwissenschaftliche Reihe
N2  - Eukaryotic cell flattening is valuable for improving microscopic observations, ranging from bright field (BF) to total internal reflection fluorescence (TIRF) microscopy. Fundamental processes, such as mitosis and in vivo actin polymerization, have been investigated using these techniques. Here, we review the well known agar overlayer protocol and the oil overlay method. In addition, we present more elaborate microfluidics-based techniques that provide us with a greater level of control. We demonstrate these techniques on the social amoebae Dictyostelium discoideum, comparing the advantages and disadvantages of each method.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 835 
KW  - PDMS
KW  - microfluidic device
KW  - lower channel
KW  - total internal reflection fluorescence
KW  - total internal reflection fluorescence microscopy
Y1  - 2020
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-428311
SN  - 1866-8372
IS  - 835
ER  - 
TY  - JOUR
A1  - Schaefer, Edith
A1  - Westendorf, Christian
A1  - Bodenschatz, Eberhard
A1  - Beta, Carsten
A1  - Geil, Burkhard
A1  - Janshoff, Andreas
T1  - Shape oscillations of dictyostelium discoideum cells on ultramicroelectrodes monitored by impedance analysis
JF  - Small
Y1  - 2011
U6  - https://doi.org/10.1002/smll.201001955
SN  - 1613-6810
VL  - 7
IS  - 6
SP  - 723
EP  - 726
PB  - Wiley-Blackwell
CY  - Malden
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  -