Biology subjects

Borghi, N.

Publications and source records attributed to Borghi, N..

11 recordsLinked to original sources

bioRxiv2026

Transcriptional coupling of metabolism and cell mechanics controls humanneuroepithelium morphogenesis

Tissue morphogenesis integrates developmental programs with cell mechanics, yet the mechanisms coupling these processes remain poorly understood. We investigated this link during neuroepithelial morphogenesis in human iPSC-derived dorsal spinal organoids. We found that PAX3, a transcription factor whose loss causes neural tube defects, promotes force-bearing adherens junction assembly. It does so by driving apical clustering of N-cadherin complexes, thereby enabling neuroepithelial morphogenesis, a function conserved in the mouse neural tube. Transcriptomic, metabolomic, and functional analyses show that PAX3 sustains upper glycolysis and the associated mannose-dependent glycosylation pathways. Exogenous mannose rescues cadherin clustering and adherens junction mechanics following PAX3 loss, whereas inhibition of glycolysis or glycosylation recapitulates these defects. These findings establish mannose metabolism as a PAX3-regulated pathway conferring mechanical competence to developing tissues.

developmental 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

Epithelial density controls cell migration through an adhesion-nucleus mechanotransduction pathway

Cell density is thought to regulate tissue growth, homeostasis, and regeneration, yet how cells sense and respond to density remains poorly understood. To investigate density-dependent mechanotransduction, we combined genetically encoded biosensors with quantitative fluorescence microscopy in epithelial cells subjected to genetic, pharmacological, and mechanical perturbations. We found that low epithelial density promotes focal adhesion growth, causing mechanical relaxation of vinculin and release of its competitive binding with FAK and ERK. This enables FAK to bind and activate ERK in the cytoplasm. Cytoskeletal tension transmitted through LINC complexes drives their nuclear translocation, where low density induces ERK-dependent chromatin decondensation and increased nuclear envelope tension. This recruits and activates cPLA2, leading to arachidonic acid production and enhanced cell migration. Together, these findings identify a mechanochemical pathway linking cell density to epithelial migration via ERK, cPLA2, and mechanically regulated signaling from adhesions to the nucleus. Significance statementIn multicellular organisms, cells constantly experience crowding, yet how they detect changes in cell density and convert them into biological responses is not well understood. Here, we show how low cell density mechanically triggers signaling inside epithelial cells to promote migration. When cells are sparse, adhesion sites grow and release key signaling proteins that move into the nucleus stretched by the cytoskeleton. These mechanical and biochemical inputs alter nuclear structure, activates lipid signaling, and boosts cell migration. By revealing how mechanical forces, cell adhesions, and nuclear signaling work together, this study provides a clear mechanistic link between cell density and migration, a process central to tissue growth, repair, and disease progression.

cell biology↗

bioRxiv2025

Chromosome condensation mechanically primes the nucleus for mitosis

Accurate transition into mitosis driven by cyclin B1-CDK1 activity is essential to avoid chromosome segregation errors and preserve genome integrity. How this activity is spatially controlled to trigger mitotic onset remains unclear. Here, we show that chromosome condensation triggers an increase in nuclear envelope (NE) tension. This increased tension is required for nuclear translocation of cyclin B1 and dynein loading on nuclear pore complexes (NPCs), ensuring timely mitotic entry. Micromanipulation experiments further indicate this tension-dependent mechanism requires SUN proteins on the NE. Disruption of chromosome condensation leads to an accumulation of the G2 checkpoint kinase Wee1 and inhibition of CDK1 activity, which result in a temporary delay in mitotic entry. This delay can be overridden by increasing tension on the NE, which accelerates the nuclear translocation of cyclin B1 and dynein loading. We propose that mitotic onset is controlled by a chromosome-dependent NE tension mechanism that enables robust spatiotemporal coupling between chromosome condensation and the structural changes required for an efficient mitosis.

cell biology↗

bioRxiv2023

Collective directional memory controls the range of epithelial cell migration

Cell migration is a fundamental behavior in multicellular development, regeneration, and homeostasis, which is deregulated in cancer. Epithelial cells migrate individually when isolated and collectively within a tissue. However, how interactions between cells affect their ability to explore space and their sensitivity to guidance signals is poorly understood. We show that isolated cells that are persistent random walkers adopt a super-diffusive behavior in an epithelium. The effect is stronger than external guidance cues and enables cells to reach greater distances than when isolated. This behavior is consistent with a fractional Brownian motion that emerges from velocity coordination between neighboring cells with intact intercellular adhesion. Furthermore, we show how the molecular stability and mechanosensitivity of adhesion complexes, both linked to the ability of the adhesion protein vinculin to dimerize, ultimately regulate the speed of collective migration and the sensitivity to guidance signals. Together, our results show how cell speed, persistence, and directionality define the efficiency of spatial cell exploration on short, intermediate, and long time scales, respectively.

biophysics↗

bioRxiv2021

A mechanical G2 checkpoint controls epithelial cell division through E-cadherin-mediated regulation of Wee1-Cdk1

Epithelial cell divisions must be tightly coordinated with cell loss to preserve epithelial integrity. However, it is not well understood how the rate of epithelial cell division adapts to changes in cell number, for instance during homeostatic turnover or upon wounding of epithelia. Here, we show epithelial cells sense local cell density through mechanosensitive E-cadherin adhesions to control G2/M cell cycle progression. We demonstrate that tensile forces on E-cadherin adhesions are reduced as local cell density increases, which prompts the accumulation of the G2 checkpoint kinase Wee1. This elevated abundance of Wee1 results in inhibitory phoshorylation of Cdk1, and thereby establishes a pool of cells that is temporarily halted in G2-phase. Importantly, these cells are readily triggered to divide upon epithelial wounding, due to the consequent increase in intercellular forces and resulting degradation of Wee1. Our data thus demonstrate that epithelial cell division is controlled by a mechanical G2 checkpoint, which is regulated by cell density-dependent intercellular forces sensed and transduced by E-cadherin adhesions.

cell biology↗

bioRxiv2020

Extracellular domains of E-cadherin determine key mechanical phenotypes of an epithelium through cell- and non-cell-autonomous outside-in signalling

Cadherins control intercellular adhesion in most metazoans. In vertebrates, intercellular adhesion differs considerably between cadherins of type-I and type-II, predominantly due to their different extracellular regions. Yet, intercellular adhesion critically depends on actomyosin contractility, in which the role of the cadherin extracellular region is unclear. Here, we dissect the roles of the Extracellular Cadherin (EC) Ig-like domains by expressing chimeric E-cadherin with E-cadherin and cadherin-7 Ig-like domains in cells naturally devoid of cadherins. Using cell-cell separation, cortical tension measurement, tissue-scale stretching and migration assays, we show that distinct EC repeats in the extracellular region of cadherins differentially modulate epithelial sheet integrity, cell-cell separation forces, and cell cortical tension through a Cdc42 pathway, which further differentially regulate epithelial tensile strength, ductility, and ultimately collective migration. Interestingly, dissipative processes rather than static adhesion energy mostly dominate cell-cell separation forces. We provide a framework for the emergence of epithelial phenotypes from cell mechanical properties dependent on EC outside-in signalling.

cell biology↗

bioRxiv2019

LINC complexes are mechanotransducers that discriminate Epithelial-Mesenchymal Transition programs

LINC complexes are transmembrane protein assemblies that physically connect the nucleo- and cytoskeletons through the nuclear envelope. Dysfunctions of LINC complexes are associated with pathologies such as cancer and muscular disorders. The mechanical roles of LINC complexes in these contexts are poorly understood. To address this, we used genetically encoded FRET biosensors of molecular tension in LINC complex proteins of fibroblastic and epithelial cells in culture. We exposed cells to mechanical, genetic and pharmacological perturbations, mimicking a range of physiological and pathological situations. We show that LINC complex proteins experience tension generated by the cytoskeleton and act as mechanical sensors of cell packing. Moreover, the LINC complex discriminates between inductions of partial and complete epithelial-mesenchymal transitions (EMT). We identify the implicated mechanisms, which associate nesprin tension sensing with -catenin capture at the nuclear envelope, thereby regulating {beta}-catenin transcription. Our data thus implicate that LINC complexes are mechanotransducers that fine-tune {beta}-catenin signaling in a manner dependent on the Epithelial-Mesenchymal Transition program.

cell biology↗

bioRxiv2019

Actin accumulates nesprin-2 at the front of the nucleus during confined cell migration

The mechanisms by which cells exert forces on their nuclei to migrate through openings smaller than the nuclear diameter remain unclear. In microfluidic devices, the hourglass shape of the nucleus and its strain patterns as it translocates through narrow constrictions suggest pulling forces. We use CRISPR/Cas9 to fluorescently label nesprin-2 giant, a protein that links the cytoskeleton to the interior of the nucleus. We demonstrate that nesprin-2 giant accumulates at the front of the nucleus during nuclear deformation through narrow constrictions, independently of the nuclear lamina. We find that nesprins are more mobile than lamin A/C, at time scales similar to that of the accumulation. Using artificial constructs, we show that the actin-binding domain of nesprin-2 is necessary and sufficient to generate this accumulation, and that microtubules are not necessary. Actin filaments are organized in a barrel structure around the moving nucleus in the direction of movement, suggesting that this structure is responsible for redistribution of nesprins towards the front of the nucleus. Two-photon ablation and the use of drugs inhibiting the cytoskeleton demonstrate a pulling force on the nucleus from the front of the cell that is dependent on formin and actomyosin contractility. This elastic recoil is significantly reduced when nesprins are reduced at the nuclear envelope. We thus show that actin redistributes nesprin-2 giant towards the front of the nucleus and contributes to pulling the nucleus through narrow constrictions, in concert with myosin.

cell biology↗

bioRxiv2018

Chromatin Condensation Fluctuations Rather Than Steady-State Predict Chromatin Accessibility

Chromatin accessibility to protein factors is critical for genome activities. Dynamic changes in nucleosomal DNA compaction and higher order chromatin structures are expected to allow specific sites to be accessible to regulatory factors and the transcriptional machinery. However, the dynamic properties of chromatin that regulate its accessibility are poorly understood. Here, we took advantage of the microenvironment sensitivity of the fluorescence lifetime of EGFP-H4 histone incorporated in chromatin to map in the nucleus of live cells the dynamics of chromatin condensation and its direct interaction with a tail acetylation recognition domain (the double bromodomain module of human TAFII250, dBD). We reveal chromatin condensation fluctuations supported by mechanisms fundamentally distinct from that of condensation. Fluctuations are spontaneous, yet their amplitudes are affected by their sub-nuclear localization and by distinct and competing mechanisms dependent on histone acetylation, ATP, and both. Moreover, we show that accessibility of acetylated histone H4 to dBD is not restricted by chromatin condensation nor predicted by acetylation, rather, it is predicted by chromatin condensation fluctuations.\n\nSignificanceIn higher eukaryotes, the structure and compaction of chromatin are considered as barriers to genome activities. Epigenetic marks such as post-translational modifications of histones can modify the structure and compaction of chromatin. The accessibility of protein factors to these epigenetic marks is therefore of paramount importance for genome activities. We reveal chromatin condensation fluctuations supported by mechanisms fundamentally distinct from that of condensation itself. We show that accessibility of acetylated histone H4 to double bromodomains is not restricted by chromatin condensation nor predicted by acetylation, rather, it is predicted by chromatin condensation fluctuations.\n\nClassificationBiological Sciences, Cell Biology

cell biology↗

bioRxiv2018

Intermediate filaments control collective migration by restricting traction forces and sustaining cell-cell contacts

Mesenchymal cell migration relies on the coordinated regulation of the actin and microtubule networks which participate in polarised cell protrusion, adhesion and contraction. During collective migration, most of the traction forces are generated by the acto-myosin network linked to focal adhesions at the front of leader cells, which transmit these pulling forces to the followers. Here, using an in vitro wound healing assay to induce polarisation and collective directed migration of primary astrocytes, we show that the intermediate filament (IF) network composed of vimentin, GFAP and nestin contributes to directed collective movement by controlling the distribution of forces in the migrating cell monolayer. Together with the cytoskeletal linker plectin, these IFs control the organisation and dynamics of the acto-myosin network, promoting the actin-driven treadmilling of adherens junctions, thereby facilitating the polarisation of leader cells. Independently of their effect on adherens junctions, IFs influence the dynamics and localisation of focal adhesions and limit their mechanical coupling to the acto-myosin network. We thus conclude that IFs promote collective directed migration by restricting the generation of traction forces to the front of leader cells, preventing aberrant tractions in the followers and by contributing to the maintenance of lateral cell-cell interactions.

cell biology↗