| Abstract: | ["The fast blood stream of animals is associated with large shear stresses. Consequently, blood cells have evolved a special morphology and internal architecture allowing them to maintain their integrity over several weeks. For instance, non-mammalian red blood cells, mammalian erythroblasts and platelets have a peripheral ring of microtubules, called the marginal band, that flattens the cell morphology by pushing on the cell cortex.\r\nUsing physical modeling, we showed that the shape of these cells stems from the balance between marginal band elasticity and cortical tension. We predict that the diameter of the cell scales with the total microtubule polymer, and verify the predicted law across a wide range of species. Our analysis also shows that the combination of the marginal band rigidity and cortical tension increases the ability of the cell to withstand forces without deformation.\r\nFinally, we study the marginal band coiling that occurs at the onset of blood platelet activation, i.e. when platelets react to extracellular signaling to perform wound healing. By a combination of theory and experiments, we show that the observed platelet rounding and coiling of the marginal band are due to the increase of the cortical tension."] |
