Soft Matter Seminar: Forward Forces of Motile Cells Measured with an Atomic Force Microscope

Tuesday, April 9, 2013 – 11:00am
Regents 351
Thomas Fuhs
University of Leipzig, Soft Matter Physics Division

Confronting motile fish keratocytes with obstacles doubling as force sensors we tested the limits of the driving actin-and-myosin-machinery. We could directly measure the force necessary to stop actin polymerization as well as the force present in the retrograde actin flow. Combined with detailed measurements of the retrograde flow velocity and specific manipulation of actin and myosin we found that actin polymerization and myosin contractility are not enough to explain the cells behavior. We show that ever-present depolymerization forces, a direct entropic consequence of actin filament recycling, are sufficient to fill this gap.

We investigated the mechanical properties and force generation of extending mouse retinal ganglion cells and NG108-15 growth cones (GCs) using different AFM-based methods. For the first time, to our knowledge, we were able to measure the forward pushing forces at the leading edge of outgrowing neuronal GCs with our drift-stabilized AFM. Our results demonstrate that these GCs have neither the required stability nor the ability to produce forces necessary to penetrate non-CNS-tissues as these are at least an order of magnitude stiffer.

Host: Jeff Urbach