Biology subjects

Plancke, C.

Publications and source records attributed to Plancke, C..

7 recordsLinked to original sources

bioRxiv2026

Persistent and recyclable myosin II minifilaments drive cortical contractility in the early C. elegans embryo

Non-muscle myosin II is a key regulator of cell and tissue morphogenesis, yet the cortical dynamics of myosin minifilaments in vivo remain poorly understood. Here, we combine SIM-TIRF and single-molecule TIRF microscopy to characterize the structure and dynamics of myosin minifilaments in an early developing embryo. High-temporal-resolution SIM-TIRF imaging revealed diverse minifilament behaviors, including partition-like events, long-range alignment of multiple minifilaments into collective structures we called proto-stress fibers, partial unbinding, and sequential unbinding and rebinding to the cortex. Photoconversion experiments showed that minifilaments persist as intact units after cortical unbinding, diffuse through the cytoplasm, and can be recycled over long distances rather than disassembling upon detachment. Despite these dynamic behaviors, minifilaments are predominantly stationary when bound to actin. Numerical simulations demonstrated that this static behavior is essential to sustain cortical stress within a continuously remodeling actin network. Using myosin motor-domain mutants, we further investigated the contribution of motor activity to these behaviors. Together, our results reveal that myosin minifilaments can persist as stable units while cycling between the cortex and cytoplasm, and that their predominantly static behavior when bound to actin enables sustained force generation in a continuously renewing cortical network. These findings provide new insights into myosin organization, recycling, and force generation during early embryonic development.

cell biology↗

bioRxiv2026

Softer when Thicker: a Conserved Scaling Law Governs Actin Cortex Mechanics

Scaling laws are powerful tools in material science to relate geometric and mechanical properties of materials. The actin cortex, a dynamic network beneath the plasma membrane, is essential for cellular morphogenesis, force generation, and tissue organization. Despite its critical role, the mechanical properties of the cortex itself remain poorly understood. Using the magnetic pincher, a new technique we recently developed, we directly measure the thickness (h) and elastic modulus (E) of the actin cortex in live cells, uncovering a universal scaling (E ~ h-2) across multiple cell types. Drawing an analogy to cellular solids, common in nature and material science, we identified an origin for this scaling: the volume fraction of actin filaments varies concomitantly with the cortex thickness, due to a conservation of filamentous actin quantity. Thus thinner cortices exhibit higher actin density and stiffness, while thicker cortices are sparser and softer. The relationship holds under diverse perturbations targeting myosin contractility, actin nucleation, and turnover, but is lost upon actin disassembly, highlighting its dependence on the intact actin network. Our results establish that cells, across cell types, function within a rather limited range of quantity of cortical actin filaments and primarily modulate cortex thickness to tune mechanical properties, with profound implications for cell shape regulation, tissue mechanics, and the interpretation of indentation-based mechanical measurements.

biophysics↗

bioRxiv2026

Spatiotemporal dynamics of hydrogen peroxide during neutrophil swarming in 3D

Neutrophil swarming enables the coordinated recruitment of large numbers of cells to sites of infection. Although reactive oxygen species (ROS) are key mediators of neutrophil function, their dynamics during collective behavior remain poorly defined. Here, we developed a 3D ex vivo swarming system combined with HyPer7-expressing dHL-60 cells to visualize intracellular hydrogen peroxide (H2O2) dynamics in real time at single-cell resolution. This approach enabled us to reliably measure NADPH oxidase 2 (NOX2) activity during neutrophil swarming, revealing dynamic H2O2 production. We show that H2O2 production is spatially confined to cells at the stimulation site and temporally coupled to swarming initiation and distal cell recruitment. ROS production depends on NOX2 activity and calcium signaling but is not required for swarm formation or amplification. Notably, H2O2 accumulation was detected throughout activated cells rather than being restricted to phagosomes, suggesting a broader intracellular oxidative response. Together, these findings reveal a coordinated oxidative program associated with neutrophil swarm initiation and raise the possibility that ROS contribute to signaling functions beyond their established role in phagocytosis.

Cell Biology↗

bioRxiv2026

Coupled nucleoplasmic flows and envelope expansion govern the mechanical resistance of the nucleus

In recent year, it became clear that the cell nucleus can undergo large deformations, during immune cell migration and tumor growth. These deformations generate signals that allow cells to sense their environment and adapt to it. How cells cope with and respond to large deformations thus strongly depends on the nuclear mechanics, but our understanding of the physical properties of the nucleus remains incomplete. In particular, it is not clear how the nuclear volume responds to deformation. Here we combine controlled confinement assays, high-resolution imaging and atomic force microscopy with theoretical modelling to propose a physical model of the cell nucleus that accounts for its surface and bulk properties and addresses both steady-state and transient regimes. Our results establish the nucleus as a poroelastic body in which mechanics are dominated by the envelope and dynamics by the chromatin, and suggest that regulating water permeability may be as important as softening the envelope for cells migrating rapidly through dense tissues.

biophysics↗

bioRxiv2025

A Dual Homeostatic Regulation of Dry Mass and Volume Defines a Target Density in Proliferating Mammalian Cells

The concentration of macromolecules, especially proteins, is vital for cellular function and is influenced not only by synthesis and degradation but also by the total cell volume. While we understand various growth regulation mechanisms, the coupling of dry mass and volume in growing mammalian cells remains unclear. Here we show that two independent mechanisms acting in single cells --one regulating volume through biophysical modulation and the other controlling protein biosynthesis--work together to maintain macromolecular dry mass density and restore it following perturbations. These mechanisms ensure that proliferating cells remain within a specific range around a target density, providing density homeostasis at the population level. Although the target density appears consistent across different cell types, it is disrupted around cell division, upon perturbations of growth pathways and in senescent cells. It may represent an optimal value for cellular processes, ensuring the efficiency of essential intracellular functions.

cell biology↗

bioRxiv2024

Conditional nmy-1 and nmy-2 alleles establish that non-muscle myosins are required for late C. elegans embryonic elongation

The elongation of C. elegans embryos allows examination of mechanical interactions between adjacent tissues. Muscle contractions during late elongation induce the remodelling of epidermal circumferential actin filaments through mechanotransduction. We investigated the possible role of the non-muscle myosins NMY-1 and NMY-2 in this process using nmy-1 and nmy-2 thermosensitive alleles. Our findings suggest these myosins act redundantly in late elongation, and that they are involved in the multi-step process of epidermal remodeling. When inactivated, NMY-1 was seen to form protein aggregates.

developmental biology↗

bioRxiv2020

Rapid assembly of a polar network architecture by formins downstream of RhoA pulses drives efficient cortical actomyosin contractility

SO_SCPLOWUMMARYC_SCPLOWActin network architecture and dynamics play a central role in cell contractility and tissue morphogenesis. Pulsed contractions driven by RhoA represent a generic mode of actomyosin contractility, but the mechanisms underlying (1) how their specific architecture emerges, and (2) how this architecture supports the contractile function of the network, remain unclear. Here, we combine quantitative microscopy, single-molecule imaging, numerical simulations and simple mathematical modelling, to explore the dynamic network architecture underlying pulsed contraction. We show that during pulsed contractions, two subpopulations of formins are recruited by RhoA from the cytoplasm and bind to the cell surface in the early C. elegans embryo: recruited formins, a functionally inactive population, and elongating formins, which actively participate in actin filaments elongation. Focusing on formin dynamics during pulses, we show that minority elongating formins precede recruited formins, a kinetic dynamics compatible with formins capturing and rapidly saturating barbed ends available for filament elongation. We then show that these elongating formins assemble a polar network of actin, with barbed ends pointing out of the pulse, pointing to a kinetic rather than mechanical control of network architecture. Finally, our numerical simulations demonstrate that this geometry favors rapid network contraction. Our results thus show that formins saturate available actin filaments barbed ends and convert a local, biochemical gradient of RhoA activity into a polar network architecture, thereby driving rapid and efficient network contractility, an important evolutionary feature in a metazoan with a rapid embryonic cell cycles. HO_SCPLOWIGHLIGHTSC_SCPLOWO_LIThe formin CYK-1 drives actin network assembly during RhoA-driven pulses C_LIO_LIThe process is extremely rapid, with a formin-based actin elongation rate higher than 1.3 m{middle dot}s-1 C_LIO_LIA barbed-end saturation mechanism allows for responsive F-actin assembly C_LIO_LIRapid and responsive F-actin elongation results in the assembly of aster-like polar actin networks C_LIO_LINumerical simulations show network polarity drives very efficient network contractility C_LI

cell biology↗