Felix successfully defended his PhD
Felix convincingly presented his PhD work entitled “Mathematical modeling of nuclei as pacemakers of cell cycle oscillations”. It was a wonderful day and evening, celebrating Felix's achievements of the last few years. We wish Felix all the best in his new position teaching at the university in Antwerp. As he won't be far away, we hope to still see you regularly here. Congratulations Dr. Nolet!
Jolan successfully defended his PhD
In the context of a joint PhD with Prof. Verfaillie of the Stem Cell institute, Jolan presented his PhD work entitled “On the study of cellular proliferation and differentiation: From experiment to theory”. Many thanks to everyone in the jury, being Georg Halder, Hans Van Oosterwyck, Leo van Grunsven, and Julia Kamenz. Everyone agreed that Jolan did an excellent job and were particularly impressed with his to-the-point and in-depth knowledge of both experimental and theoretical work. Similarly impressed here Jolan!
A modular approach for modeling the cell cycle based on functional response curves
Bistability plays an important role in many biochemical processes and typically emerges from complex interaction patterns such as positive and double negative feedback loops. Jolan and Jan explicitly incorporated a functional expression describing an S-shaped input-output curve in the model equations, without the need for considering the underlying biochemical events. Using such approach, we then constructed a cell cycle model consisting of multiple bistable switches, accounting for a number of known properties of the cell cycle. Nice work Jolan and Jan! Read more here in our PLoS Comp. Biol. paper.
Analytical approximations for the speed of pacemaker-generated waves
In oscillatory media, waves can be generated by pacemaker regions which oscillate faster than their surroundings. Jan applied analytical tools (i.e. singular perturbation and phase reduction methods) to investigate the factors that determine the speed of these waves. These analytical estimates are compared to numerical simulations described in our previous work. Check out the paper in Phys. Rev. E. Good stuff Jan!
How do nuclei control mitotic waves in an import-diffusion model?
In this work, Felix extended the modeling work he did for our 2020 eLife paper in which we showed that nuclei control the spatial origin of mitotic waves. He analyzed a model where nuclei periodically import and export cell cycle regulators, leading to a redistribution of such regulator in the cytoplasm. We show that when the cell cycle period depends on the local concentration of regulators, the model exhibits mitotic waves. Congratulations Felix! Read more here.
Jan successfully defended his PhD
At the castle of Arenberg, Jan gave a wonderful presentation about his thesis work, entitled “The role of bistability and time delay in the coordination of the cell cycle”. Although many followed his PhD defense online, it was a pleasure to be able to have some family and friends present for this important occasion. Also a big thanks to all jury members: Jordi Garcia Ojalvo, Edda Klipp, Karel Talavera and Enrico Carlon!
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!