(428f) The Role of Microtubules in Epithelial Cell Rheology

The importance of mechanics and force to biological processes is increasingly appreciated and affects behaviors as distinct as cell motility, morphogenesis, and differentiation. In this work we begin to isolate the mechanical roles of the different cytoskeletal proteins. Specifically, we assess the effects of microtubule disruption on cellular rheology. We use four complementary microrheological techniques (magnetic twisting cytometry, two point microrheology, and two other techniques involving laser tracking of large, colloidal particles) to measure cellular mechanical properties in epithelial cells. In combination, these techniques have the novel ability of probing cell mechanics over a wide range of frequency, varying geometry and different driving (applied torques or innate thermal driving) in single cells. Previously, in untreated cells, we found a remarkably simple, but rich, consensus behaviour and evidence for two mechanically distinct sub-cellular networks: a cortical response and peri-nuclear response. Here, we apply the same suite of techniques to cells with de-polymerized microtubule networks. There was no observable change in the mechanics of the cortical mechanical response, as measured with MTC. However the techniques that measure the peri-nuclear region showed a small change in amplitude and drastically different functional form as the cells become softer and more liquid-like. This may be due to a response by the cell, such as increased myosin motor activity, or an indication that the microtubule network is mechanically dominat in the perinuclear region.