The world is a complex and dynamic place. Earth takes part in an intricate dance with the moon, surrounding planets, our sun, other stars and entire galaxies. All interact with one another determining our position in the universe. On a much smaller scale, humans consist of trillions of cells that work together to let us walk, run, and think. Each such single living cell is driven by the interaction of about a trillion non-living molecules. Life at all scales is complex, dynamic, and difficult to understand. All these examples, however, have in common that they obey the basic laws of physics. Although we can apply those laws to understand a small part of each system, many interacting parts can behave wildly different and unpredictable. By combining theory and experiment, our lab aims at understanding such system dynamics, studying living (Dynamics in Biology) and non-living (Dynamics in Physics) systems.
Bistability of PP2A-B55 and APC/C activity
In a collaboration with Julia Kamenz in the lab of Jim Ferrell at Stanford Univ., we demonstrate biochemically using Xenopus laevis egg extracts that the Cdk1-counteracting phosphatase PP2A-B55 and the APC/C function as a bistable switch, even when the bistability of Cdk1 activation is suppressed. In addition, Cdk1 regulates PP2A-B55 in a biphasic manner and APC. Our findings, which are published in Current Biology, suggest that changes in Cdk1 activity are permissive for mitotic entry and exit but that the changes in PP2A-B55 activity are the ultimate trigger. Very impressive experiments by Julia, who just started her own lab at the university of Groningen in the Netherlands, check it out: https://www.rug.nl/staff/j.l.kamenz/.
Time-dependent bistable switches enhance robustness and accuracy of cell cycle transitions
Jan showed how a dynamically changing bistable switch can provide a cell with better control over the timing of cell cycle transitions. Moreover, cell cycle oscillations built on bistable switches are more robust when the bistability is modulated in time. These findings are not specific to cell cycle models and may apply to other bistable systems in which the bistable response curve is time-dependent. Read all about this work in PLoS Computational Biology. Well done Jan!
So happy to welcome Daniel to our lab! During his PhD at the Institute for Cross-Disciplinary Physics and Complex Systems (IFISC - Spain), he worked on vegetation models of pattern formation. He will use techniques from statistical physics and nonlinear dynamics to study pattern formation processes in the context of the cell cycle.
Jan analyzed how pacemaker-generated waves synchronize an oscillatory medium
Jan used numerical simulation to study the properties of waves in oscillatory media sent out by a pacemaker. By comparing different oscillator types and pacemaker properties, he quantified which factors determine the speed of these waves, which are often used by biological systems to transmit information and synchronize processes. The work is now out in Phys. Rev. Research, congratulations!
Talks at Dynamics Days Digital
Although the in-person conference of Dynamics Days was canceled due to the pandemic, an online version was organized (see the conference's website). Jan and Felix presented their work on pacemaker-driven mitotic waves in a minisymposium on “Nonlinear waves in biology” organized by Lendert and Carsten Beta (Univ. Potsdam). You can find their talks on Youtube: Felix' talk and Jan's talk.