Biology subjects

Suzanne, M.

Publications and source records attributed to Suzanne, M..

11 recordsLinked to original sources

bioRxiv2026

Deep-tissue absolute force spectroscopy with sub-piconewton precision

Quantitative measurements performed directly in vivo are necessary to understand how forces shape living tissues, yet this remains challenging due to optical scattering and mechanical complexity. Here, we present a method for making absolute force measurements using nanoscopic optical tweezers with a sensitivity of 300 fN in optically turbid biological media. Our approach combines back focal plane interferometry operating within the optical memory effect regime with a global fluctuation-dissipation fitting framework that simultaneously calibrates position detection, trap stiffness, and viscoelastic response. This method overcomes aberration-induced biases by jointly fitting passive fluctuations and driven harmonic responses, enabling robust force reconstruction in thick, scattering tissues within the mechanically relevant frequency range below 300 Hz. We validate our approach using highly scattering Drosophila pupae and embryos, demonstrating reliable in vivo measurements of forces and mechanical properties. Operating at a 1 kHz acquisition bandwidth, the system captures relevant mechanical dynamics without requiring extended high-frequency detection. Using this framework, we quantify the increase in cortical tension during pupal morphogenesis, characterize tissue viscoelasticity, and reveal stage-dependent variations in nuclear membrane tension during embryogenesis, even in the presence of strong ATP-driven fluctuations. Beyond bulk measurements, our method enables the quantitative mechanical characterization of single cells within mechanically coupled tissues.

bioengineering↗

bioRxiv2025

Cell exit during EMT is mechanically triggered independently of E-Cadherin loss

Epithelial-to-mesenchymal transition (EMT) is a fundamental cell process with essential functions in tissue and organ formation during development but also metastasis during cancer progression. The shift between these two states is driven by evolutionary conserved transcription factors. Cell exit from the epithelium of origin is considered to be a mere consequence of progressive adhesion loss due to transcriptional repression of genes encoding molecules such as E-Cadherin or cell polarity regulators. Here we show in the Drosophila leg that, counterintuitively, adhesions (as well as cell polarity) are maintained during cell exit, while an apico-basal force is applied on E-Cadherin complexes in vivo. By combining a genetic screen, optogenetics and laser ablation experiments, we found that this pulling force originates from transient basal filopodia-like protrusions, formed as soon as cells start to exit. Finally, apical cell detachment requires -Spectrin activity, suggesting that the lateral cortex is required to efficiently transmit basal forces up to the apical cell pole. Our results indicate that, in a mature tissue, cell exit during EMT is a mechanically controlled process. Such a mechanism driving EMT without of E-Cadherin loss could fuel metastatic dissemination of collectively migrating cancer cells.

developmental biology↗

bioRxiv2025

Spatio-temporal control of nuclear mechanotransduction during EMT

During epithelial-to-mesenchymal transition (EMT), cells generate mechanical forces. How the nucleus reacts to these mechanical cues, ensuring a tight balance between mechano-protection and mechanotransduction, is a key yet unresolved question. Here we dissect the spatio-temporal control of nuclear mechanostransduction during EMT, using Drosophila mesoderm invagination as a model. We found that two conserved pro-EMT genes respond differently to compressive forces: while snail transcription remains unaffected, compression is sufficient to activate twist transcription within seconds. We further revealed a spatially patterned genome-wide transcriptional response to EMT forces, with an apical mechanoprotection contrasting with a permissive basal nuclear environment. The direct recording of nascent transcription in response to a controlled nuclear micromanipulation provides compelling evidence of nuclear heterogeneity in the transcriptional response to forces. Overall, these results reveal that EMT nuclei respond directly and rapidly to mechanical forces, in a spatially defined pattern.

cell biology↗

bioRxiv2024

Mechanical state of pre-tumoral epithelia dictates subsequent tumour aggressiveness

Tumours evolve through the acquisition of increasingly aggressive traits associated with dysplasia. This progression is accompanied by the alteration of tumour mechanical properties, especially through extracellular matrix remodelling. However, the contribution of intrinsic tumour cells mechanics to tumour aggressiveness remains unknown in vivo. Here we show that adherens junction tension in pre-tumoral tissues dictates subsequent tumour evolution. Increased cell contractility, observed in aggressive tumours before any sign of tissue overgrowth, proved sufficient to trigger dysplasia in normally hyperplastic tumours. Unexpectedly, high contractility contributes to tumour evolution through cell death induction which favours cell-cell junctions weakening. Overall, our results highlight the need to re-evaluate the roles of tumoral cell death, and identify pre-tumour cell mechanics as an unsuspected early marker and key trigger of tumour aggressiveness. GRAPHICAL ABSTRACT O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=100 SRC="FIGDIR/small/594669v1_ufig1.gif" ALT="Figure 1"> View larger version (27K): org.highwire.dtl.DTLVardef@1a677edorg.highwire.dtl.DTLVardef@b8940org.highwire.dtl.DTLVardef@15feebaorg.highwire.dtl.DTLVardef@13213ca_HPS_FORMAT_FIGEXP M_FIG C_FIG

cancer biology↗

bioRxiv2024

Compressive stress drives morphogenetic apoptosis

Tissues and organs are constantly submitted to physical stress, including compression, stretching, shear stress. The impact of compression due to overcrowding on cell extrusion has been the focus of recent studies. However, how tissue compression impact cell death in the context of morphogenesis is mostly unexplored. Here, we showed that a natural compression is exerted on the Drosophila developing leg by the surrounding tissue (or envelope) that is required for correct leg morphogenesis. In this tissue, apoptosis, preferentially localized in the future fold region, contributes to drive tissue folding through the generation of a pulling force on the apical surface. However, only a subset of these cells are dying within the expression domain of proapoptotic genes and how this precise pattern of cell death is established is totally unknown. We found that the natural compression exerted by the envelope contributes to the regulation of apoptosis, revealing that compression constitutes an integral part of apoptosis regulation during leg morphogenesis. We further reveal that compression drives a significant increase in lateral tension and favors apoptosis through the mechanosensor Piezo. Finally, perturbing cell cortex anchoring or membrane stiffness prove sufficient to block this process. Altogether, these results open new perspectives in term of mechanotransduction during morphogenesis.

developmental biology↗

bioRxiv2023

An easy-to-use microfluidic mechano-chemostat for tissues and organisms reveals that confined growth is accompanied with increased macromolecular crowding

Conventional culture conditions are oftentimes insufficient to study tissues, organisms, or 3D multicellular assemblies. They lack both dynamic chemical and mechanical control over the microenvironment. While specific microfluidic devices have been developed to address chemical control, they are often hard to use and do not allow the control of compressive forces. Here, we present a set of microfluidic devices which all rely on the use of sliding elements consisting of microfabricated rods that can be inserted inside a microfluidic device. Sliding elements enable the creation of reconfigurable sealed culture chambers for the study of whole organisms or model micro-tissues. By confining the micro-tissues, we studied the biophysical impact of growth-induced pressure and showed that this mechanical stress is associated with an increase in macromolecular crowding, shedding light on this understudied type of mechanical stress. Our mechano-chemostat is an easy-to-use microfluidic device that allows the long-term culture of biological samples and can be used to study both the impact of specific conditions as well as the consequences of mechanical compression.

biophysics↗

bioRxiv2022

mBeRFP, a versatile fluorescent tool to enhance multichannel live imaging and its applications

Cell and developmental biology increasingly require live imaging of protein dynamics in cells, tissues or living organisms. Thanks to the discovery and the development of a panel of fluorescent proteins over the last decades, live imaging has become a powerful and commonly used approach. However, multicolor live imaging remains challenging. The generation of long Stokes shift red fluorescent proteins, such as mBeRFP, offers interesting new perspectives to bypass this limitation. Here, we constructed a set of mBeRFP-expressing vectors and provided a detailed characterization of this fluorescent protein for in vivo live imaging and its applications in Drosophila. Briefly, we showed that a single illumination source is sufficient to simultaneously stimulate mBeRFP and GFP. We demonstrated that mBeRFP can be easily combined with classical green and red fluorescent protein without any crosstalk. We also showed that the low photobleaching of mBeRFP is suitable for live imaging, and that this protein can be used for quantitative applications such as FRAP or laser ablation. Finally, we believe that this fluorescent protein, with the set of new possibilities it offers, constitutes an important tool for cell, developmental and mechano biologists in their current research.

developmental biology↗

bioRxiv2020

Super-resolved live-cell imaging using Random Illumination Microscopy

Super-resolution fluorescence microscopy has been instrumental to progress in biology. Yet, the photo-induced toxicity, the loss of resolution into scattering samples or the complexity of the experimental setups curtail its general use for functional cell imaging. Here, we describe a new technology for tissue imaging reaching a 114nm/8Hz resolution at 30 {micro}m depth. Random Illumination Microscopy (RIM) consists in shining the sample with uncontrolled speckles and extracting a high-fidelity super-resolved image from the variance of the data using a reconstruction scheme accounting for the spatial correlation of the illuminations. Super-resolution unaffected by optical aberrations, undetectable phototoxicity, fast image acquisition rate and ease of use, altogether, make RIM ideally suited for functional live cell imaging in situ. RIM ability to image molecular and cellular processes in three dimensions and at high resolution is demonstrated in a wide range of biological situations such as the motion of Myosin II minifilaments in Drosophila.

bioengineering↗

bioRxiv2020

Mechanical control of morphogenesis robustness

Epithelial sheets undergo highly reproducible remodeling to shape organs. This stereotyped morphogenesis depends on a well-defined sequence of events leading to the regionalized expression of developmental patterning genes that finally triggers downstream mechanical forces to drive tissue remodeling at a pre-defined position. However, how tissue mechanics controls morphogenetic robustness when challenged by intrinsic perturbations in close proximity has never been addressed. Here, we show that a bias in force propagation ensures stereotyped morphogenesis despite the presence of mechanical noise in the environment. We found that knockdown of the Arp2/3 complex member Arpc5 specifically affects fold directionality without altering neither the developmental nor the force generation patterns. By combining in silico modeling, biophysical and ad hoc genetic tools, our data reveal that junctional Myosin II planar polarity favors long-range force channeling and ensures folding robustness, avoiding force scattering and thus isolating the fold domain from surrounding mechanical perturbations.

developmental biology↗

bioRxiv2019

Curling of epithelial monolayers reveals coupling between active bending and tissue tension

Epithelial monolayers are two-dimensional cell sheets which compartmentalise the body and organs of multi-cellular organisms. Their morphogenesis during development or pathology results from patterned endogenous and exogenous forces and their interplay with tissue mechanical properties. In particular, bending of epithelia is thought to results from active torques generated by the polarization of myosin motors along their apico-basal axis. However, the contribution of these out-of-plane forces to morphogenesis remains challenging to evaluate because of the lack of direct mechanical measurement. Here, we use epithelial curling to characterize the out-of-plane mechan ics of epithelial monolayers. We find that curls of high curvature form spontaneously at the free edge of epithelial monolayers devoid of substrate in vivo and in vitro. Curling originates from an enrichment of myosin in the basal domain that generates an active spontaneous curvature. By measuring the force necessary to flatten curls, we can then estimate the active torques and the bending modulus of the tissue. Finally, we show that the extent of curling is controlled by the interplay between in-plane and out-of-plane stresses in the monolayer. Such mechanical coupling implies an unexpected role for in-plane stresses in shaping epithelia during morphogenesis.

biophysics↗

bioRxiv2018

Physical and functional cell-matrix uncoupling in a developing tissue under tension

Tissue mechanics play a crucial role in organ development. It relies on cells and extracellular matrix (ECM) mechanical properties, but also on their reciprocal interaction. The relative physical contribution of cells and ECM to morphogenesis is poorly understood. Here, we dissected the mechanics of the envelope of the Drosophila developing leg, an epithelium submitted to a number of mechanical stresses: first stretched, it is then torn apart and withdrawn to free the leg. During stretching, we found that mechanical tension is entirely borne by the ECM at first, then by the cellular monolayer as soon as they detach themselves from one another. Then, each envelope layer is removed by an independent mechanism: while ECM withdraws following local proteolysis, cellular monolayer withdrawal is independent of ECM degradation and driven by an autonomous myosin-II-dependent contraction. These results reveal a physical and functional cell-matrix uncoupling that could timely control tissue dynamics during development.

cell biology↗