Biology subjects

Balland, M.

Publications and source records attributed to Balland, M..

16 recordsLinked to original sources

bioRxiv2026

Mechanochemical synchronization of force oscillations in connective tissue models

Cells in a tissue coordinate their behavior collectively by mechanical and chemical feedback with their surroundings. To study how such feedback mechanisms interact, we embed multicellular spheroids from mouse and primary human fibroblasts of different origin in 3D collagen matrices. Immediately after embedding, spheroids apply steadily increasing, radially symmetric, inward-directed forces to the surrounding matrix. Typically, within a few hours, collective force oscillations emerge with an average time interval of {approx}30 min. Similar force oscillations also arise in engineered, parallel-aligned microtissues attached to flexible pillars. Force oscillations propagate between neighboring cells as a mechanical wave, accompanied by calcium waves that travel at comparable speeds of several hundred m/min. Blocking gap junctions or mechanosensitive Piezo1 channels impairs these oscillations, indicating that calcium signaling contributes to their propagation. Their amplitude and frequency are regulated by integrin-mediated feedback in actin-rich protrusions and by ERK signaling, which also controls collective invasion into the surrounding matrix. Neighboring spheroids mechanically synchronize their force oscillations in phase and frequency over distances of up to {approx}2 mm without direct contact. Together, our results show that oscillatory mechanochemical feedback enables multicellular systems to coordinate force generation and invasive migration across cellular and millimeter length scales in 3D matrices.

biophysics↗

bioRxiv2025

Electric field intensity modulates keratocyte migration without altering turning dynamics

Cell migration is a cornerstone of biological systems, enabling organisms to adapt to environmental stimuli and maintain homeostasis. Disruptions in this process can lead to functional impairment or system failure. In many cases, cells do not move randomly; instead, they migrate directionally in response to external cues, allowing them to perform essential biological functions. This directed movement is especially important in processes such as morphogenesis, cancer invasion, and wound healing. To unravel the complexities of directional cell migration, investigating natural guiding stimuli is crucial. Among these, electrical fields stand out as precise and physiologically relevant stimulus. Using a platform designed to apply programmable electric fields, the SCHEEPDOG device; we applied controlled electric field of varying intensities to keratocytes and quantitatively analyzed their migratory behavior. Our findings reveal that electric field stimulation not only induces robust directional migration but also enhances migration speed in an intensity-dependent manner. Additionally, cells initially moving in random directions gradually align with the field vector, with higher intensities accelerating the alignment. Intriguingly, while both speed and alignment time can be modulated through stimulation, the overall shape of migration trajectories remains unchanged. In other terms, for cells initially moving to the opposite direction of the field, the alignment is accompanied by making a turn and the size and shape of this turn is not affected by the magnitude of the electrical stimulation. Together, these results demonstrate that electrical stimulation can tune the speed and directional alignment of keratocyte migration without altering turning dynamics. These findings contribute to a deeper understanding of electrotaxis and offers new insights into how biophysical cues regulate cell migration in both physiological and pathological contexts.

biophysics↗

bioRxiv2025

Morphogenesis-on-chip: A minimal in vitro assay for cell intercalation highlights the importance of interfacial tension and migratory forces

Cell intercalation, the dynamic exchange of cellular neighbors, is fundamental to embryonic morphogenesis, tissue homeostasis, and wound healing. Despite extensive study in complex tissues, the minimal mechanical requirements driving intercalation remain poorly understood due to confounding tissue level interactions. Here, we present a novel morphogenesis-on-chip assay utilizing micropatterned cell quadruplets. This system isolates the elementary unit of intercalation while enabling quantitative force and shape measurements. Cross-shaped micropatterns generate stable four cell configurations in MDCK epithelial cells. Surprisingly, these cells spontaneously undergo T1 transitions autonomously. We combined live imaging with force inference and traction force microscopy, which revealed that intercalation emerges from two distinct mechanisms: interfacial tension dynamics and differential cell migration. Specifically, we show a correlation between central junction shrinkage and increased relative tension. Similarly, we show a correlation between central junction shrinkage and migratory forces. We successfully adapted the assay to Xenopus mesoderm cells, revealing conserved mechanical principles across cell types. Furthermore, experimentally derived effective energy landscapes closely match theoretical vertex model predictions, and suggest a dominant role for migratory forces in driving intercalation. This confirms that our minimal system recapitulates the fundamental physics of intercalation. This approach provides the first quantitative framework for studying intercalation mechanics in isolation and establishes a versatile platform for investigating morphogenetic processes. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=73 SRC="FIGDIR/small/662274v2_ufig1.gif" ALT="Figure 1"> View larger version (25K): org.highwire.dtl.DTLVardef@41db6aorg.highwire.dtl.DTLVardef@1ac1cb1org.highwire.dtl.DTLVardef@8fcb2corg.highwire.dtl.DTLVardef@63e320_HPS_FORMAT_FIGEXP M_FIG C_FIG

biophysics↗

bioRxiv2025

Osmotic pressure induces unexpected relaxation of contractile 3D microtissue

Cell contraction and proliferation, matrix secretion and external mechanical forces induce compression during embryogenesis and tumor growth, which in turn regulate cell proliferation, metabolism or differentiation. How compression affects tissue contractility, a hallmark of tissue function, is however unknown. Here we apply osmotic compression to microtissues of either mouse colon adenocarcinoma CT26 cells, mouse NIH 3T3 fibroblasts, or human primary colon cancer-associated fibroblasts. Microtissues are anchored to flexible pillars that serve as force transducers. We observe that low-amplitude osmotic compression induces a rapid relaxation of tissue contractility, primed by the deformation of the extracellular matrix. Furthermore, we show that this compression-induced relaxation is independent of the cell type, proportional to the initial tissue contractility, and depends on RhoA-mediated myosin activity. Together, our results demonstrate that compressive stress can relax active tissue force, and points to a potential role of this feedback mechanism during morphogenetic events such as onco- or embryogenesis.

biophysics↗

bioRxiv2023

Dual-topology of collagen XV and tenascin C acts in concert to guide and shape developing motor axons

During development, motor axons are guided towards their muscle target by various extrinsic cues including extracellular matrix (ECM) proteins those identities remain poorly documented. Using single-cell RNA-sequencing of differentiating slow muscle progenitors (SMP) in zebrafish, we charaterized the SMP as a major source of ECM proteins that were computationally predicted to form a basement membrane-like structure tailored for motor axon guidance. Multiple in vivo and in vitro approaches further revealed that motor axon shape and growth relies on the timely expression of the attractive cue Collagen XV-B (ColXV-B) that locally provides motor axons with a permissive soft microenvironment and separately organizes the repulsive cue Tenascin C into a unique functional dual topology. Bioprinted micropatterns mimicking their unique topology provide compelling evidence that it represents a sufficient condition to elicit directional motor axon growth. Our study provides the first evidence that ECM topology and stiffness critically influence motor axon navigation in vertebrates with potential applications in regenerative medicine for peripheral nerve injury.

developmental biology↗

bioRxiv2022

An EpCAM/Trop2 mechanostat differentially regulates individual and collective migration of human carcinoma cells

EpCAM and its close relative Trop2 are well-known markers of carcinoma, but the potential role of these cell surface proteins in cancer metastasis remains unclear. They are known, however, to downregulate myosin-dependent contractility, a key parameter involved in cell adhesion and migration. We investigate here the morphogenetic impact of the high EpCAM and Trop2 levels typically found in epithelial breast cancer cells, using spheroids of MCF7 cells as an in vitro model. Intriguingly, EpCAM depletion stimulated spheroid cohesive spreading, while Trop2 depletion had the opposite effect. Combining cell biological and biophysical approaches, we demonstrate that while EpCAM and Trop2 both contribute to moderate cell contractility, their depletions differentially impact on the process of "wetting" a substrate, here both matrix and neighboring cells, by affecting the balance of cortical tension at cell and tissue interfaces. These distinct phenotypes can be explained by partial enrichment at specific interfaces. Differential distribution and antagonistic loss-of-function phenotypes are also observed in two other breast cancer cell lines with very different characteristics, suggesting that these are general properties of these two regulators. Our data are consistent with a simple model in which the EpCAM-Trop2 pair acts as a mechanostat that tunes local cortical tension, thus influencing a spectrum of adhesive and migratory behaviours.

cell biology↗

bioRxiv2022

Force propagation between epithelial cells depends on active coupling and mechano-structural polarization

Cell-generated forces play a major role in coordinating the large-scale behavior of cell assemblies, in particular during development, wound healing and cancer. Mechanical signals propagate faster than biochemical signals, but can have similar effects, especially in epithelial tissues with strong cell-cell adhesion. However, a quantitative description of the transmission chain from force generation in a sender cell, force propagation across cell-cell boundaries, and the concomitant response of receiver cells is missing. For a quantitative analysis of this important situation, here we propose a minimal model system of two epithelial cells on an H-pattern ("cell doublet"). After optogenetically activating RhoA, a major regulator of cell contractility, in the sender cell, we measure the mechanical response of the receiver cell by traction force and monolayer stress microscopies. In general, we find that the receiver cells shows an active response so that the cell doublet forms a coherent unit. However, force propagation and response of the receiver cell also strongly depends on the mechano-structural polarization in the cell assembly, which is controlled by cell-matrix adhesion to the adhesive micropattern. We find that the response of the receiver cell is stronger when the mechano-structural polarization axis is oriented perpendicular to the direction of force propagation, reminiscent of the Poisson effect in passive materials. We finally show that the same effects are at work in small tissues. Our work demonstrates that cellular organization and active mechanical response of a tissue is key to maintain signal strength and leads to the emergence of elasticity, which means that signals are not dissipated like in a viscous system, but can propagate over large distances.

biophysics↗

bioRxiv2022

Light-driven biological actuators to probe the rheology of 3D microtissues

The mechanical properties of biological tissues are key to the regulation of their physical integrity and function. Although the application of external loading or biochemical treatments allows to estimate these properties globally, it remains problematic to assess how such external stimuli compare with internal, cell-generated contractions. Here we engineered 3D microtissues composed of optogenetically-modified fibroblasts encapsulated within collagen. Using light to control the activity of RhoA, a major regulator of cellular contractility, we induced local mechanical perturbation within 3D fibrous microtissues, while tracking in real time microtissue stress and strain. We thus investigated the dynamic regulation of light-induced, local contractions and their spatio-temporal propagation in microtissues. By comparing the evolution of stresses and strains upon stimulation, we demonstrated the potential of our technique for quantifying tissue elasticity and strain propagation, before examining the possibility of using light to create and map local anisotropies in mechanically heterogeneous microtissues. Altogether, our results open an avenue to guide the formation of 3D tissues while non-destructively charting their rheology of 3D tissues in real time, using their own constituting cells as internal actuators.

biophysics↗

bioRxiv2021

The Amot/Integrin protein complex transmits mechanical forces required for vascular expansion

Vascular development is a complex multistep process involving the coordination of cellular functions such as migration, proliferation and differentiation. Understanding the underlying mechanisms of these processes is of importance due to involvement of vessel expansion in various pathologies. How mechanical forces generated by cells and transmission of these physical forces control vascular development is poorly understood. Using an endothelial-specific genetic model in mice, we show that deletion of the scaffold protein, Angiomotin (Amot), inhibits migration and expansion of physical and pathological vascular network. We further show that Amot is required for tip cell migration and the extension of cellular filopodia. Exploiting in vivo and in vitro molecular approaches, we show that Amot binds talin and is essential for relaying forces between fibronectin and the cytoskeleton. Finally, we provide evidence that Amot is a novel component of the endothelial integrin adhesome and propose that Amot integrates spatial cues from the extra-cellular matrix in order to form a functional vascular network.

cell biology↗

bioRxiv2020

Adaptive mechanoproperties characterize glioblastoma fitness for invasion

Glioblastoma are heterogeneous tumors composed of highly invasive and highly proliferative clones. Heterogeneity in invasiveness could emerge from discrete biophysical properties linked to specific molecular expression. We identified clones of patient-derived glioma propagating cells that were either highly proliferative or highly invasive and compared their cellular architecture, migratory and biophysical properties. We discovered that invasiveness was linked to cellular fitness. The most invasive cells were stiffer, developed higher mechanical forces on the substrate and moved stochastically. The mechanochemical-induced expression of the formin FMN1 conferred invasive strength that was confirmed in patient samples. Moreover, FMN1 ectopic expression in less invasive clones increased fitness parameters. Mechanistically, FMN1 acts from the microtubule lattice, counteracting microtubule bundling and promoting a robust cell-body cohesion leading to highly invasive hurdling motility. One Sentence SummaryFMN1 increases cell mechanics and invasiveness.

cell biology↗

bioRxiv2019

Molecular flux control encodes distinct cytoskeletal responses by specifying SRC signaling pathway usage.

Multi-domain signaling proteins sample numerous stimuli to coordinate distinct cellular responses. Understanding the mechanisms of their pleiotropic signaling activity requires to directly manipulate their activity of decision leading to distinct cellular responses. We developed an optogenetic probe, optoSRC, to control spatio-temporally the SRC kinase, a representative example of versatile signaling node, and challenge its ability to generate different cellular responses. Genesis of different local molecular fluxes of the same optoSRC to adhesion sites, was sufficient to trigger distinct and specific acto-adhesive responses. Collectively, this study reveals how hijacking the pleiotropy of SRC signaling by modulating in space and time subcellular molecular fluxes of active SRC kinases.

cell biology↗

bioRxiv2019

Spatial Asymmetries of the Prophase Nucleus Regulate Dynein Recruitment to Ensure Mitotic Fidelity

During prophase, centrosomes need to separate and position to correctly assemble the mitotic spindle. This process occurs through the action of molecular motors, cytoskeletal networks and the nucleus. How the combined activity of these different components is spatiotemporally regulated to ensure efficient spindle assembly remains unclear. Here we show that during prophase the centrosomes-nucleus axis reorients, so that centrosomes are positioned on the shortest nuclear axis at nuclear envelope (NE) breakdown. This centrosomes-nucleus configuration depends on mechanical cues generated by mitotic chromosome condensation on the prophase nucleus. We further show these mechanosensitive cues act through SUN1/2 and NudE+NudEL to enable the polarized loading of Dynein on the NE. Finally, we observe this centrosome configuration favors the establishment of an initial bipolar spindle scaffold, facilitating chromosome capture and accurate segregation, without compromising division plane orientation. We propose that chromosome segregation fidelity depends on the mechanical properties of the prophase nucleus that facilitate spindle assembly by regulating NE-Dynein localization.

cell biology↗

bioRxiv2018

Confinement-induced transition between wave-like collective cell migration modes

The structural and functional organization of biological tissues relies on the intricate interplay between chemical and mechanical signaling. Whereas the role of constant and transient mechanical perturbations is generally accepted, several studies recently highlighted the existence of long-range mechanical excitations (i.e., waves) at the supracellular level. Here, we confine epithelial cell mono-layers to quasi-one dimensional geometries, to force the establishment of tissue-level waves of well-defined wavelength and period. Numerical simulations based on a self-propelled Voronoi model reproduce the observed waves and exhibit a phase transition between a global and a multi-nodal wave, controlled by the confinement size. We confirm experimentally the existence of such a phase transition, and show that wavelength and period are independent of the confinement length. Together, these results demonstrate the intrinsic origin of tissue oscillations, which could provide cells with a mechanism to accurately measure distances at the supracellular level.

biophysics↗

bioRxiv2018

Actomyosin-driven force patterning controls endocytosis at the immune synapse

An important channel of cell-to-cell communication is direct contact. The immune synapse is a paradigmatic example of such type of interaction: it forms upon engagement of antigen receptors in lymphocytes by antigen-presenting cells and allows the local exchange of molecules [1]. Although [2], how forces organize and mechanics has been shown to play an important role in this process impact on synapse function is unknown. We found that mechanical forces are spatio-temporally patterned at the immune synapse: global contractile forces are observed at the synapse periphery and local point-like forces are detected at its centre. The global contractile forces result from a pulsatile centripetal actomyosin flow that leads to formation of F-actin protrusions from which the central point like forces emerge. Noticeably, these force-producing actin protrusions constitute the main site of antigen extraction and endocytosis. Accordingly, deletion of the myosin IIA gene leads to impaired B cell responses. The interplay between global and local forces governed by the actomyosin cytoskeleton therefore controls the endocytic function of the immune synapse and might constitute a more general mechanism in the physical regulation of cell-cell interactions.

cell biology↗

bioRxiv2017

Magneto-active substrates for local mechanical stimulation of living cells

Cells are able to sense and react to their physical environment by translating a mechanical cue into an intracellular biochemical signal that triggers biological and mechanical responses. This process, called mechanotransduction, controls essential cellular functions such as proliferation and migration. The cellular response to an external mechanical stimulation has been investigated with various static and dynamic systems, so far limited to global deformations or to local stimulation through discrete substrates. To apply local and dynamic mechanical constraints at the single cell scale through a continuous surface, we have developed and modelled magneto-active substrates made of magnetic micro-pillars embedded in an elastomer. Constrained and unconstrained substrates are analysed to map surface stress resulting from the magnetic actuation of the micro-pillars and the adherent cells. These substrates have a rigidity in the range of cell matrices, and the magnetic micro-pillars generate local forces in the range of cellular forces, both in traction and compression. As an application, we followed the protrusive activity of cells subjected to dynamic stimulations. Our magneto-active substrates thus represent a new tool to study mechanotransduction in single cells, and complement existing techniques by exerting a local and dynamic stimulation, traction and compression, through a continuous soft substrate.

biophysics↗

bioRxiv2017

Asymmetric adhesion of rod-shaped bacteria controls microcolony morphogenesis

Bacterial biofilms are spatially structured communities, within which bacteria can differentiate depending on environmental conditions. During biofilm formation, bacteria attach to a surface and use cell-cell contacts to convey the signals required for the coordination of biofilm morphogenesis. How bacteria can maintain both substrate adhesions and cell-cell contacts during the expansion of a microcolony is still a critical yet poorly understood phenomenon. Here, we describe the development of time-resolved methods to measure substrate adhesion at the single cell level during the formation of E. coli and P. aeruginosa microcolonies. We show that bacterial adhesion is asymmetrically distributed along the cell body. Higher adhesion forces at old poles put the daughter cells under tension and force them to slide along each other. These rearrangements increase cell-cell contacts and the circularity of the colony. We propose a mechanical model based on the microscopic details of adhesive links, which recapitulates microcolony morphogenesis and quantitatively predicts bacterial adhesion from simple time lapse movies. These results explain how the distribution of adhesion forces at the subcellular level directs the shape of bacterial colonies, which ultimately dictates the circulation of secreted signals.

biophysics↗