Biophysical Society Thematic Meeting | Singapore

Mechanobiology of Disease

Poster Abstracts

36-POS Board 36 Force Transmission through the Microtubule Cytoskeleton Matthias D. Koch 1,2 , Alexander Rohrbach 1 .

1 University of Freiburg, Freiburg, Germany, 2 Princeton University, Princeton, NJ, USA. The eukaryotic cytoskeleton is a complex and dynamic network that regulates important cellular functions and is driven by a large variety of forces or mechanical stimuli. Due to their mechanical rigidity, microtubules are able to transport such stimuli, which allows integrating distant regions of a cell nearly instantaneously. This is relevant for the response to pressure, gravity, or osmotic changes and during mechanotransduction, a critical process during many severe diseases such as deafness or cancer. So far, only equilibrium mechanical properties of single microtubules have been characterized. Since intra- and extracellular forces occur on a brought range of time scales, we fill this void by using an in vitro bottom-up approach to determine the frequency response of single microtubules and small networks thereof that mimic the basic cytoskeletal structure. We combine a label-free darkfield imaging technique with multiple time-shared optical tweezers to flexibly construct and force-probe such networks with a well-defined, user-selected geometry over a broad frequency range. We report on a length dependent stiffening of individual microtubules above a physiologically relevant transition frequency between 1–30Hz due to the excitation of higher order bending modes. This increased transport efficiency for high frequencies can be regarded as a mechanical high-pass filter with a tunable cutoff frequency, e.g., allowing the cell to react to rapid fluctuations at distant sites. Furthermore, we identify and relate different mechanical responses for different network geometries to different functions inside the cell. Triangular networks, for example, display a comparatively high stiffness even for low frequencies and resemble a load bearing scaffold protecting the nucleus. The mechanistic comparison between basic network geometries, the known cytoskeletal topologies and the general function of different cell lines will substantially strengthen our understanding of the function and structure of the cytoskeleton, both during health and disease.

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