TY  - JOUR
A1  - Stange, Maike
A1  - Hintsche, Marius
A1  - Sachse, Kirsten
A1  - Gerhardt, Matthias
A1  - Valleriani, Angelo
A1  - Beta, Carsten
T1  - Analyzing the spatial positioning of nuclei in polynuclear giant cells
JF  - Journal of Physics D: Applied Physics
N2  - How cells establish and maintain a well-defined size is a fundamental question of cell biology. Here we investigated to what extent the microtubule cytoskeleton can set a predefined cell size, independent of an enclosing cell membrane. We used electropulse-induced cell fusion to form giant multinuclear cells of the social amoeba Dictyostelium discoideum. Based on dual-color confocal imaging of cells that expressed fluorescent markers for the cell nucleus and the microtubules, we determined the subcellular distributions of nuclei and centrosomes in the giant cells. Our two- and three-dimensional imaging results showed that the positions of nuclei in giant cells do not fall onto a regular lattice. However, a comparison with model predictions for random positioning showed that the subcellular arrangement of nuclei maintains a low but still detectable degree of ordering. This can be explained by the steric requirements of the microtubule cytoskeleton, as confirmed by the effect of a microtubule degrading drug.
KW  - Dictyostelium
KW  - cell nucleus
KW  - positioning
KW  - imaging
KW  - spatial poisson distribution
Y1  - 2017
U6  - https://doi.org/10.1088/1361-6463/aa8da0
SN  - 0022-3727
SN  - 1361-6463
VL  - 50
IS  - 46
PB  - IOP Publ. Ltd.
CY  - Bristol
ER  - 
TY  - JOUR
A1  - Gerhardt, Matthias
A1  - Walz, Michael
A1  - Beta, Carsten
T1  - Signaling in chemotactic amoebae remains spatially confined to stimulated membrane regions
JF  - Journal of cell science
N2  - Recent work has demonstrated that the receptor-mediated signaling system in chemotactic amoeboid cells shows typical properties of an excitable system. Here, we delivered spatially confined stimuli of the chemoattractant cAMP to the membrane of differentiated Dictyostelium discoideum cells to investigate whether localized receptor stimuli can induce the spreading of excitable waves in the G-protein-dependent signal transduction system. By imaging the spatiotemporal dynamics of fluorescent markers for phosphatidylinositol (3,4,5)-trisphosphate (PIP3), PTEN and filamentous actin, we observed that the activity of the signaling pathway remained spatially confined to the stimulated membrane region. Neighboring parts of the membrane were not excited and no receptor-initiated spatial spreading of excitation waves was observed. To generate localized cAMP stimuli, either particles that carried covalently bound cAMP molecules on their surface were brought into contact with the cell or a patch of the cell membrane was aspirated into a glass micropipette to shield this patch against freely diffusing cAMP molecules in the surrounding medium. Additionally, the binding site of the cAMP receptor was probed with different surface-immobilized cAMP molecules, confirming results from earlier ligand-binding studies.
KW  - Signal transduction
KW  - Excitable dynamics
KW  - Dictyostelium
KW  - cAMP
KW  - PIP3
KW  - PIP2
KW  - PI3K
KW  - PTEN
KW  - Micropipette aspiration
KW  - cAMP receptor
KW  - Patch clamp
Y1  - 2014
U6  - https://doi.org/10.1242/jcs.161133
SN  - 0021-9533
SN  - 1477-9137
VL  - 127
IS  - 23
SP  - 5115
EP  - 5125
PB  - Company of Biologists Limited
CY  - Cambridge
ER  -