Micropipette aspiration (MPA) is a widely applied method for studying cortical tension and deformability. Based on simple hydrostatic principles, this assay allows the application of a speci fi c magnitude of mechanical stress on cells. This powerful method has revealed insights about cell mechanics and mechanosensing, not only in Dictyostelium discoideum but also in other cell types. In this chapter, we present how to set up a micropipette aspiration system and the experimental procedures for

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... etermining cortical tension and mechanosensory responses. It is well recognized that mechanical forces impact the behavior of biological systems, ranging from molecular (e.g., force-induced focal adhesion complex formation) to tissue levels (e.g., blood pressure in the vasculature) ( 1, 2 ) . Methods such as atomic force microscopy (AFM) and optical traps have been utilized to study cell behavior in response to forces ( 3, 4 ) . These methods, although powerful, primarily exert forces in the sub-nN range over sub-μ m 2 surface areas of the cell. Compression is another form of cell deformation, and compressive stress may be applied using agarose overlay with a thin agarose sheet ( 5 ) . Although a straightforward method to use, the speci fi c amount of mechanical stress applied by agarose overlay can be tricky to estimate. In contrast, micropipette aspiration (MPA) can apply a speci fi c amount of pressure to cells (ranging from pN/ μ m 2 to nN/ μ m 2 ) over several tens of μ m 2 , allowing total forces of up to a few tens of nN to be applied to cells.