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The mechanical and rheological description of the cytoplasm has been the subject of recent interest because intracellular pressure can drive leading edge protrusion in migrating cells, particularly in 3D and in confined environments. Blebs are one type of a pressure-driven protrusion that cells use when migrating on flat substrates as well as confined and 3D environments, and provide a good experimental system for probing mechanics of the cytoplasm. Blebbing occurs when the cytoskeleton detaches from the cell membrane, resulting in the pressure-driven flow of cytosol towards the area of detachment and the local expansion of the cell membrane. Recent experiments involving blebbing cells have led to conflicting hypotheses regarding the time scale of intracellular pressure propagation. To address this discrepancy, we develop a dynamic computational model of the cell that includes mechanics of and the interactions between the intracellular fluid, the actin cortex, the cell membrane, and the cytoskeleton. We show that the multiphase poroelastic rheology of cytoplasm is essential to explain experimental observations. Further our model reveals multiple timescales in bleb expansion, and both time scales are needed to explain the apparently conflicting experimental results.

Please let Mariel (mariel@math.ucdavis.edu) know if you would like to meet with the speaker and/or join the dinner.