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Max Planck Researchers reveal the physical basis of polarizing cortical flows

The cell cortex is a highly dynamic structure beneath the plasma membrane, which gives cells their shape and provides stability. The actin microfilaments building up that structure can shrink or grow- this makes the cell flexible, able to ingress for instance, which is needed for cell division. Forces drive these movements.

During asymmetric cell division, the cell has to polarize, which means that it builds up two different domains at each of its poles, which differ in their molecular composition – otherwise it could not produce two daughter cells with different cellular fates. Polarization requires the cell cortex to move toward one cell pole in a cohesive flow. This flow carries cellular cargo, which specify the different fates of the two domains. Researchers at two Dresden-based Max Planck Institutes now report for the very first time a method to demonstrate that the cortical flow is associated with anisotropies: Movements show that the forces differ according to the direction of the single-cell embryo.

Using laser ablation, the forces underlying cortical flows were measured and complemented by a theoretical model. The project worked at the interface of biology and physics, it involved scientists of the Max Planck Institute if Molecular Cell Biology (MPI-CBG) and the Max Planck Institute of the Physics of Complex (MPI-PKS).

original paper:
Mirjam Mayer, Martin Depken, Justin S. Bois, Frank Jülicher, Stephan W. Grill: Anisotropies in cortical tension reveal the physical basis of polarising cortical flows. Nature, Advance Online Publication, 19 September, 2010
doi: 10.1038/nature09376

Caption:
Cortical laser ablation along the cyan line: The displacement of the tissue is marked by the black arrows and the overlay. Movements show properties that differ according to the direction: magenta (pre-cut), or green (post-cut).