Biology subjects

Fagotto, F.

Publications and source records attributed to Fagotto, F..

7 recordsLinked to original sources

bioRxiv2026

A microfluidic approach to explore mesoderm tissue dynamics and its natural variability

Vertebrate gastrulating mesoderm is a prototypic example of a mesenchymal-like tissue undergoing extensive remodelling. While the tissue may be globally represented as a viscoelastic material, the actual biological material is intrinsically complex. To get to a real understanding of its properties, one needs to move to the mesoscale, linking cellular properties to collective phenomena. Vertebrate embryos also display a remarkable variability in mechanical properties, despite which they robustly complete gastrulation. This study attempts to explore these aspects by dissecting Xenopus mesoderm cell behaviour in a minimal system, using aspiration through a microfluidic system to impose controlled stress to a mesoderm aggregate. We show that beyond estimating global rheology at the tissue scale, it is possible to infer a wealth of information based on cell morphology and dynamics. Our data are consistent with collective behaviour being mostly dictated by the balance between the capacity of cells to stretch and the resistance to cell-cell contacts, which limits cell-cell intercalation and thus tissue remodelling. Importantly, tissues are not only able to transmit stress over a distance, they also clearly react to it through actively reinforcing cell-cell mechanical coupling. This adaptative property is found through a broad range of tissue stiffness, and adhesion strength appears to scale with the elastic modulus, suggesting that cell stiffness may ultimately be the key parameter setting mesoderm rheology and accounting for the large differences observed between embryo batches.

developmental biology↗

bioRxiv2025

napariTFM: An Open-Source Tool for Traction ForceMicroscopy and Monolayer Stress Microscopy

Cellular force generation and transmission are fundamental processes driving cell migration, division, tissue morphogenesis, and disease progression. Traction Force Microscopy (TFM) and Monolayer Stress Microscopy (MSM) have emerged as essential techniques for quantifying these mechanical processes, but current software solutions are fragmented across multiple platforms with varying degrees of usability and accessibility. Here, we present napariTFM, a comprehensive open-source plugin for the napari image viewer that integrates state-of-the-art algorithms for both TFM and MSM analysis within an intuitive graphical user interface. The software implements TV-L1 optical flow for displacement analysis, Fourier Transform Traction Cytometry (FTTC) for force reconstruction, and finite element methods for stress calculation, supporting both single-frame and time-series analysis of 2D microscopy data. Systematic validation using synthetic datasets with known ground truth values demonstrated excellent accuracy, with correlation coefficients above 0.9 for most situations. Real-time parameter adjustment and immediate visualization capabilities enable interactive optimization of analysis parameters and quality assessment during processing. Finally, we demonstrate the softwares capabilities through analysis of optogenetic contractility experiments in cell doublets. napariTFM addresses critical gaps in the cellular mechanics software ecosystem by combining algorithmic rigor with practical usability, providing the research community with an accessible platform for quantitative studies of cellular force generation and transmission.

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↗

bioRxiv2023

Dynamic remodelling of cadherin contacts in embryonic mesenchymal cells during differential cell migration

A fundamental aspect of morphogenesis is the capacity of cells to actively exchange neighbours while maintaining the overall cohesion of the tissue. These cell rearrangements require the dynamic remodelling of cadherin cell adhesions. Many studies have examined this process in tissues where it is driven by the joint action of cell protrusions and actomyosin contraction along the shrinking junction. However, cell rearrangements can also occur through differential migration. This mode of cell rearrangement, characteristic of mesenchymal tissues, is much less well understood. Here, we explore the prototypical case of the gastrulating Xenopus prechordal mesoderm, and provide the first detailed analysis at how cadherin contacts are remodelled and eventually disrupted in this type of tissue. Using a reductionist approach, including analysis of single contacts using a dual pipette aspiration setup, we unveil two concurrent mechanisms. Most cadherins are removed via "peeling", i.e. disruption of the trans bonds and lateral diffusion out of the contact. In parallel, a remnant of cadherins concentrates at the shrinking contact, which is ultimately resolved by breakage of the link with the actin cytoskeleton, showing that the weakest link shifts at different stages of contact remodelling. Additionally, we observe recruitment of myosin peripheral to the shrinking contact, which influences the efficiency of the final detachment. Finally, manipulation of cortical tension indicates that the process is sensitive to the magnitude and orientation of the forces applied on the contact, revealing another key relationship between cell-cell adhesion and the cortical cytoskeleton. This study unravels a new modality of cell contact dynamics, which is likely to be widely relevant for highly migratory mesenchymal tissues.

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↗

bioRxiv2019

Ectoderm to mesoderm transition by downregulation of actomyosin contractility

Collective migration of cohesive tissues is a fundamental process in morphogenesis, and is particularly well illustrated during gastrulation by the rapid and massive internalization of the mesoderm, which contrasts with the much more modest movements of the ectoderm. In the Xenopus embryo, the differences in morphogenetic capabilities of ectoderm and mesoderm can be connected to the intrinsic motility of individual cells, very low for ectoderm, highly for mesoderm. Surprisingly, we find these seemingly deep differences can be accounted for simply by differences in Rock-dependent actomyosin contractility. We show that Rock inhibition is sufficient to rapidly unleash motility in the ectoderm and confer it with mesoderm-like properties. In the mesoderm, this motility is dependent on two negative regulators of RhoA, the small GTPase Rnd1 and the RhoGAP Shirin/Dlc2/ArhGAP37. Both are absolutely essential for gastrulation. At the cellular and tissue level, the two regulators show overlapping yet distinct functions. They both contribute to decrease cortical tension and confer motility, but Shirin tends to increase tissue fluidity and stimulate dispersion, while Rnd1 tends to favour more compact collective migration. Thus, each is able to contribute to a specific property of the migratory behaviour of the mesoderm. We propose that the "ectoderm to mesoderm transition" is a prototypic case of collective migration driven by a downregulation of cellular tension, without the need for the complex changes traditionally associated with the epithelial to mesenchymal transition.

cell biology↗

bioRxiv2018

Limited significance of the in situ proximity ligation assay

In situ proximity ligation assay (isPLA) is an increasingly popular technique that aims at detecting the close proximity of two molecules in fixed samples using two primary antibodies. The maximal distance between the antibodies required for producing a signal is 40 nm, which is lower than optical resolution and approaches the macromolecular scale. Therefore, isPLA may provide refined positional information, and is commonly used as supporting evidence for direct or indirect protein-protein interaction. However, we show here that this method is inherently prone to false interpretations, yielding positive and seemingly specific signals even for totally unrelated antigens. We discuss the difficulty to produce adequate specificity controls. We conclude that isPLA data should be considered with extreme caution.

cell biology↗