Symposium Series Physics and Medicine (7)
Pressure, density, elasticity are classical physical properties, which are required to fully describe the processes in human cell assemblies – for example, to distinguish tumours from healthy tissue or to stimulate the regrowth of nerve cells. These examples illustrate how physics can provide new stimuli for basic medical research.
Today, modern physical methods and physical thinking are being transferred towards physiological application worldwide. In order to promote the exchange between different researchers and working groups, the Max Planck Zentrum für Physik und Medizin is starting a new series of public mini-symposia, in which two to three scientists from North America, Europe or Asia will present their work virtually. The series has been started in March and will be continued on the 6th, 8th und 9th April.
To take part in the symposia, please register for MPL's scientific lectures newsletter (please ensure that you tick the "scientific lecture" checkbox). We will send the Zoom links about one hour before the symposium starts.
The schedule for Friday, April 9th in detail:
15:00 - 15:05 Welcome
15:05 - 15:50 Meredith Betterton, University of Colorado Boulder: "Action at a distance in cells: motor guidance by long-range communication through the microtubule highway"
Collective behavior can arise when particles interact by coupling through a medium. Examples of coupling-driven interactions in physics include Cooper pairing in superconductors, atom diffusion coupled through a crystal lattice, and liquid-liquid phase separation in a gel. Recent work has hinted that motor proteins moving on microtubules may “talk” to each other over surprisingly long distances. Coupling between motor proteins is biologically important because motor arrays drive muscle contraction, flagellar beating, and chromosome segregation, among other processes. In the past, models of motor coupling have invoked either direct mechanical linkage or protein crowding, both of which rely on short-range motor-motor interactions. As a result, coupling mechanisms that act at longer length scales remain largely unexplored. We found that microtubules can physically couple motor movement in the absence of short-range interactions. The human kinesin-4 motor Kif4A changes the run-length and velocity of other motors on the same microtubule in the dilute binding limit, when 10-nm-sized motors are separated by microns. This effect does not depend on specific motor-motor interactions because similar changes in Kif4A motility are induced by kinesin-1 motors. A micron-scale attractive interaction potential between motors is sufficient to recreate the experimental results in a computational model. Unexpectedly, our theory suggests that long-range microtubule-mediated coupling not only affects binding kinetics but also motor stepping. Therefore, motors can sense and respond to motors bound several microns away on a microtubule. These results suggest a paradigm in which the microtubule lattice, rather than being merely a passive track, is a dynamic medium responsive to binding proteins to enable new forms of collective motor behavior.
— 10 min break —
16:00 - 16:45 Kevin Chalut, University of Cambridge: "Mechanobiology of cell fate choice"
The role of mechanics in cell fate choice has been largely overlooked; however, mechanics plays a significant role in getting the right cells to the right place at the right time in development. My lab is investigating the interplay between mechanics and signaling in cell fate decisions, both in stem cells and the embryo. I will present our work showing how cell surface mechanics influences early embryonic spatial patterning and fate transitions in the mouse embryo. I will further discuss a hypothetical feedback loop between mechanics and signaling that has significant impact on cellular plasticity both in development and stem cells.
— 10 min break —
16:55 - 17:40 Alexandra Zidovska, New York University: "The rich inner life of the cell nucleus: Dynamic organization, active flows and emergent rheology"
The nucleus is the control center of the cell, containing genetic material essential for life. Yet, the physical principles underlying its organization in space and time remain a mystery. In this talk, I will show work from my group revealing that the biophysical complexity of the nucleus can be organized around three inter-related and interactive facets: heterogeneity, activity and rheology. Most nuclear constituents are sites of active, ATP-dependent processes and are thus inherently dynamic: The genome undergoes constant rearrangement, the nuclear envelope flickers and fluctuates, nucleoli migrate and coalesce, and many of these events are mediated by nucleoplasmic flows and interactions. And yet there is spatiotemporal organization in terms of hierarchical structure of the genome, its coherently-moving regions and membrane-less compartmentalization via phase-separated nucleoplasmic constituents. Moreover, the non-equilibrium or activity-driven nature of the nucleus gives rise to emergent rheology and material properties that impact all cellular processes via the central dogma of molecular biology. New biophysical insights into the cell nucleus can come from appreciating this rich inner life.
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