title: Balance of microtubule stiffness and cortical tension determines the size of blood cells with marginal band across species.
abstract: The fast bloodstream of animals is associated with large shear stresses. To withstand these conditions, blood cells have evolved a special morphology and a specific internal architecture to maintain their integrity over several weeks. For instance, nonmammalian red blood cells, mammalian erythroblasts, and platelets have a peripheral ring of microtubules, called the marginal band, that flattens the overall cell morphology by pushing on the cell cortex. In this work, we model how the shape of these cells stems from the balance between marginal band rigidity 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. Finally, we model the marginal band coiling that occurs during the disk-to-sphere transition observed, for instance, at the onset of blood platelet activation. We show that when cortical tension increases faster than cross-linkers can unbind, the marginal band will coil, whereas if the tension increases more slowly, the marginal band may shorten as microtubules slide relative to each other.
authors.affiliation: Cell Biology and Biophysics Unit, European Molecular Biology Laboratory, 69117 Heidelberg, Germany.
authors.forename: Serge
authors.initials: S
authors.lastname: Dmitrieff
authors.affiliation: Cell Biology and Biophysics Unit, European Molecular Biology Laboratory, 69117 Heidelberg, Germany.
authors.forename: Adolfo
authors.initials: A
authors.lastname: Alsina
authors.affiliation: Cell Biology and Biophysics Unit, European Molecular Biology Laboratory, 69117 Heidelberg, Germany.
authors.forename: Aastha
authors.initials: A
authors.lastname: Mathur
authors.affiliation: Cell Biology and Biophysics Unit, European Molecular Biology Laboratory, 69117 Heidelberg, Germany nedelec@embl.de.
authors.forename: François J
authors.initials: FJ
authors.lastname: Nédélec
mesh_terms: D000818:Animals; D001696:Biomechanical Phenomena; D001792:Blood Platelets / Q000166:cytology* / Q000502:physiology; D003198:Computer Simulation; D004912:Erythrocytes / Q000166:cytology* / Q000502:physiology; D008870:Microtubules / Q000502:physiology*; D008954:Models, Biological; D013045:Species Specificity
keywords: blood platelet; cytoskeleton; mechanics; scaling; theory