Biology subjects

Poenisch, W.

Publications and source records attributed to Poenisch, W..

4 recordsLinked to original sources

bioRxiv2024

Cell shape noise strength regulates shape dynamics during EMT-associated cell spreading

Cellular shape is intimately linked to cell function and state, and transitions between cell states are tightly coupled to shape changes. Yet, shape has been largely overlooked in state transitions studies. Here, we combine morphometric analysis with theoretical modeling and molecular perturbations to interrogate cell shape dynamics during epithelial-to-mesenchymal transition (EMT). Using stochastic inference, we extract the morphogenetic landscape underlying EMT. We show that within this landscape, EMT-associated cell spreading reflects a transition between shape attractors. Strikingly, we observe a peak in cell shape noise strength concomitant with spreading, and show that higher shape noise accelerates transitions between shape attractors. Our morphometric analysis framework will be widely applicable to quantitative cell shape investigations in physiology and disease. Together, our results identify a key role for cellular stochasticity as a regulator of shape change rate, and highlight that shape dynamics yield rich phenotypic information that enhances our understanding of cellular states.

biophysics↗

bioRxiv2022

A pili-driven bacterial turbine

Work generated by self-propelled bacteria can be harnessed with the help of microdevices. Such nanofabricated microdevices, immersed in a bacterial bath, may exhibit unidirectional rotational or translational motion. Swimming bacteria that propel with the help of actively rotating flagella are a prototypical example of active agents that can power such microdevices. In this work, we propose a computational model of a micron-sized turbine powered by bacteria that rely on active type IV pili appendages for surface-associated motility. We find that the turbine can rotate persistently over a time scale that significantly exceeds the characteristic times of the single cell motility. The persistent rotation is explained by the collective dynamics of multiple pili of groups of cells attaching to and pulling on turbine. Furthermore, we show that the turbine can rotate permanently in the same direction by altering the pili binding to the turbine surface in an asymmetric fashion. We thus can show that by changing the adhesive properties of the turbine while keeping its symmetric geometry, we can still break the symmetry of its rotation. Altogether, this study widely expands the range of bacteria that can be used to power nanofabricated microdevices, and, due to high pili forces generated by pili retraction, promises to push the harnessed work by several orders of magnitude.

biophysics↗

bioRxiv2021

Aggregation controlled by condensate rheology

Biomolecular condensates in living cells can exhibit a complex rheology including viscoelastic and glassy behaviour. This rheological behavior of condensates was suggested to regulate polymerisation of cytoskeletal filaments and aggregation of amyloid fibrils. Here, we theoretically investigate how the rheological properties of condensates can control the formation of linear aggregates. To this end, we propose a kinetic theory for linear aggregation in coexisting phases, which accounts for the aggregate size distribution and the exchange of aggregates between inside and outside of condensates. The rheology of condensates is accounted in our model via aggregate mobilities that depend on aggregate size. We show that condensate rheology determines whether aggregates of all sizes or dominantly small aggregates are exchanged between condensate inside and outside on the time-scale of aggregation. As a result, the ratio of aggregate numbers inside to outside of condensates differs significantly. Strikingly, we also find that weak variations in the rheological properties of condensates can lead to a switch-like change of the number of aggregates. These results suggest a possible physical mechanism for how living cells could control linear aggregation in a switch-like fashion through variations in condensate rheology. SIGNIFICANCEThe intracellular space can be organized through phase-separated condensates that often exhibit rheological properties reminiscent of complex fluids. These condensates can affect biochemical processes such as the formation of linear aggregates, in particular biofilaments or amyloids. Here, we propose a theoretical model for how condensate rheology can control the irreversible formation of linear aggregates. A key finding is that size and number of aggregates change in a switch-like fashion upon weak changes in condensate rheology. Our model paves the way to unravel the physiochemical mechanisms of how the rheology of condensates can control aberrant protein aggregation. Such mechanisms may explain how rheological changes, such as ageing or the transition to dormancy, give rise to diseases related to protein aggregation.

biophysics↗

bioRxiv2020

Mouse embryonic stem cells switch migratory behaviour during early differentiation

Development relies on a series of precisely orchestrated cell fate changes. While studies of fate transitions often focus on changes in gene regulatory networks, most transitions are also associated with changes in cell shape and cell behaviour. Here, we investigate changes in migratory behaviour in mouse embryonic stem (ES) cells during their first developmental fate transition, exit from ES cell state. We show that naive pluripotent ES cells cannot efficiently migrate on 2-dimensional substrates but are able to migrate in an amoeboid fashion when placed in confinement. Exit from ES cell state, typically characterised by enhanced cell spreading, is associated with decreased migration in confinement and acquisition of mesenchymal-like migration on 2D substrates. Interestingly, confined, amoeboid-like migration of ES cells strongly depends on Myosin IIA, but not Myosin IIB. In contrast mesenchymal-like migration of cells exiting the ES cell state does not depend on Myosin motor activity but relies on the activity of the Arp2/3 complex. Together, our data suggest that during early differentiation, cells undergo a switch in the regulation of the actin cytoskeleton, leading to a transition from amoeboid-to mesenchymal-like migration. Summary statementNaive mouse embryonic stem cells display amoeboid-like migration in confinement, but switch to mesenchymal-like migration as they exit the ES cell state.

cell biology↗