Biology subjects

Roca-Cusachs, P.

Publications and source records attributed to Roca-Cusachs, P..

At least 19 recordsLinked to original sources

bioRxiv2025

Mechanical forces stimulate Golgi export

Cells face diverse mechanical stimuli that vary with cell type, state, and pathological conditions. Mechanobiology investigates how cells sense and respond to these forces. While most work has focused on the cell surface and nucleus as primary mechanosensors, how intracellular organelles adapt to extracellular mechanical forces remains largely unknown. Here, we show that extracellular mechanical signals influence the secretory function of the Golgi apparatus. By subjecting adherent cells to mechanical challenges -cell spreading on different ligands, altered substrate stiffness, or equibiaxial strain-, we reveal that extracellular forces modulate Golgi-to-cell surface carrier biogenesis, thereby regulating exocytosis. Together with changes in Golgi membrane tension, we identify molecular determinants of the mechanotransduction pathway, including microtubule acetylation, diacylglycerol production, and protein kinase D activity. In turn, inhibition of Golgi export suppresses this mechanoresponse and causes impaired cell spreading. These findings uncover a bidirectional mechanotransduction axis in which extracellular mechanics tune Golgi secretory output, providing a framework for investigating organelle-based mechanoadaptation in physiology and disease.

cell biology↗

bioRxiv2025

A keratin bundling transition uncages the nucleus in stretchedepithelia

There is broad consensus that intermediate filaments play a key role in protecting cells and tissues from large deformations. However, little is known about how they fulfil this function. Here we demonstrate that epithelial cells undergo a slow adaptation to stretch that couples a star- bundling transition of keratin filaments and the escape of the nucleus from its keratin cage. The bundling transition begins with a depletion of keratin filaments at tri-cellular junctions followed by a progressive accumulation in thick bundles that bisect cell-cell junctions. Bundling is a cooperative process that initiates in a few scattered cells and propagates to their neighbours through desmosomes, leading to the growth of multicellular clusters that contain a percolated network of thick keratin bundles. Bundling dynamics are slow and strongly influenced by the interaction between actin and keratin. Informed by a computational model, we provide evidence that keratin bundling generates a compressive stress on the nucleus, which is relaxed by nuclear escape from the keratin cage. The topological transitions identified here provide epithelia with a multiscale mechanism to adapt to sustained stretch.

biophysics↗

bioRxiv2025

Mechanically Tunable DNA Hydrogel Microparticles for 3D Cellular Systems

Hydrogel microparticles (HMPs) are powerful tools to study and manipulate cellular behavior in 3D cell culture systems and animal models. Here, fully DNA-based HMPs are presented, whose material properties can be precisely tuned by sequence-programmable design of self-assembling DNA nanostructures. These DNA-HMPs offer control over size, stiffness, viscoelasticity and ligand presentation. They are formed by microfluidic encapsulation of two types of orthogonal DNA nanostars and a sequence-complementary DNA linker in water-in-oil droplets. By varying the valency of the DNA nanostar designs, tunable mechanical properties are achieved - spanning three orders of magnitude in Youngs modulus from 30 Pa to 6.5 kPa with distinct viscoelastic behavior. Click-chemistry based functionalization with the small fibronectin-derived peptide cyclic-RGD (c[RGD]) enables integration into fibroblast spheroids. DNA-HMPs are stably retained within the spheroids for several days and undergo design- and stiffness-dependent remodeling, indicating active interactions between the cells and the DNA-HMPs. Combining tunable material properties and inherent biocompatibility of DNA with straightforward functionalization and stimuli-responsiveness, these DNA-HMPs represent a versatile tool to probe and manipulate tissue behaviors in 3D cell cultures and in vivo models. Table of Contents O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=184 SRC="FIGDIR/small/665473v2_ufig1.gif" ALT="Figure 1000"> View larger version (51K): org.highwire.dtl.DTLVardef@c226ceorg.highwire.dtl.DTLVardef@81c3b3org.highwire.dtl.DTLVardef@1573ee1org.highwire.dtl.DTLVardef@e1518c_HPS_FORMAT_FIGEXP M_FIG DNA hydrogel microparticles are designed to exhibit controllable viscoelasticity and stiffness across three orders of magnitude from 30 Pa to 6.5 kPa. They are uptaken into fibroblast spheroids where they are actively remodeled by cellular forces depending on their mechanical properties. C_FIG

bioengineering↗

bioRxiv2025

Multiscale wrinkling dynamics in epithelial shells

Thin shells buckle and wrinkle when compressed. While this behavior is generally detrimental in engineering, it has been widely implicated in epithelial morphogenesis and patterning during development. Yet the rules governing buckling of active viscoelastic shells like epithelia remain unclear. Here we delineate those rules by combining an experimental system that allows us to sculpt epithelial shells and subject them to controlled deflation with a 3D computational model linking cytoskeletal dynamics to tissue mechanics. Experiments and simulations across several orders of magnitude in time and space reveal that buckling emerges for fast deflation relative to the cortexs relaxation time, and is suppressed by high contractility. We show, further, that the tissue develops wrinkle patterns with different degrees of symmetry breaking that depend on its size and viscous confinement. Strikingly, we find that epithelial buckling is a multiscale phenomenon involving long-lived supracellular folds but also short-lived subcellular wrinkles in the actin cortex. Finally, by forming epithelial shells with anisotropic curvature we rationally direct buckling into predictable wrinkle patterns. Our study shows that epithelial tissues can be understood as hierarchical materials with mechanical instabilities that can be harnessed to engineer epithelial morphogenesis.

biophysics↗

bioRxiv2025

Mechanical Coordination of Intestinal Cell Extrusion by Supracellular 3D Force Patterns

Every day, the mammalian intestinal epithelium extrudes millions of cells to sustain tissue self-renewal. Despite its fundamental role in intestinal homeostasis, the mechanisms that trigger, compartmentalize, and execute intestinal cell extrusion remain largely unknown. Here, using intestinal organoids, we map the three-dimensional forces and cytoskeletal dynamics that drive intestinal cell extrusion. We show that, unlike in other epithelia, extrusion is initiated by the sudden dissolution of a contractile myosin 2A meshwork triggered by a calcium influx. Following meshwork dissolution, the extruding cell and its neighbors generate an upwards traction force that requires myosin contractility but is generated by lamellipodial protrusions in neighboring cells. Importantly, these lamellipodia not only act as force generators but also determine whether extrusion occurs apically or basally, serving as symmetry breakers of the process. Finally, we show that compartmentalization of cell extrusion to the outside of the intestinal crypt does not require curvature and instead depends on myosin 2A. Our findings reveal that the intestinal epithelium exhibits a distinctive mode of extrusion, in which tension differentials--rather than compressive stresses from crowding--trigger and compartmentalize cell removal.

cell biology↗

bioRxiv2025

Guidance of cellular nematics into shape-programmable living surfaces

Engineering living materials capable of autonomously morphing into predetermined shapes holds great potential for applications ranging from synthetic tissue morphogenesis to soft robotics. In this regard, harnessing the inherent ability of cellular tissues to self-organize and generate robust force fields offers a promising strategy for creating self-shaping living surfaces. However, achieving precise control over tissue mechanics to direct specific morphogenetic outcomes remains a challenge. Here, we introduce a strategy to program tissue shape transformations through the nematic organization of cellular forces. By precisely controlling nematic order and topological defects, we generate millimeter-scale tissues programmed with specific multicellular tension fields. Using a theoretical framework that integrates contractile nematics with thin sheet mechanics, we explore the role of nematically guided tensions in shape morphogenesis. Experimentally, upon tissue detachment, nematically guided tension fields drive out-of-plane deformations, generating reproducible 3D shapes. By integrating tissue contractility and nematic patterning, our approach offers a robust framework for the rational design of shape-programmable living surfaces.

biophysics↗

bioRxiv2024

Single cell migration along and against confined haptotactic gradients

Directed cell migration along gradients of extracellular matrix (ECM) density -a process called haptotaxis- plays a central role in morphogenesis, the immune response, and cancer invasion. It is commonly assumed that cells respond to these gradients by migrating directionally towards the regions of highest ligand density. In contrast with this view, here we show that cells exposed to micropatterned fibronectin gradients exhibit a complex repertoire of trajectories, including directed haptotactic migration up the gradient but also linear oscillations and circles with extended periods of migration down the gradient. To explain this behavior, we developed a biophysical model of haptotactic cell migration based on a coarse-grained molecular clutch model coupled to persistent stochastic polarity dynamics. While initial haptotactic migration is explained by the differential friction at the front and back of the cell, the observed complex trajectories over longer time scales arise from the interplay between differential friction, persistence, and physical confinement. Overall, our study reveals that confinement and persistence modulate the ability of cells to sense and respond to haptotactic cues and provides a framework to understand how cells navigate complex environments.

cell biology↗

bioRxiv2024

Parameters for sensing lipid loosening at the inner nuclear membrane by amphipathic helices

Amphipathic helices (AHs) are ubiquitous protein motifs that modulate targeting to organellar membranes by sensing differences in bulk membrane properties. However, the adaptation between membrane-targeting AHs and the nuclear membrane environment that surrounds the genome is poorly understood. Here, we computationally screened for candidate AHs in a curated list of characterized and putative human inner nuclear membrane (INM) proteins. Cell biological and in vitro experimental assays combined with computational calculations demonstrated that AHs detect lipid packing defects over electrostatics to bind to the INM, indicating that the INM is loosely packed under basal conditions. Membrane tension resulting from hypotonic shock further promoted AH binding to the INM, whereas cell-substrate stretch did not enhance recruitment of membrane tension-sensitive AHs. Together, our work demonstrates the rules driving lipid-protein interactions at the INM, and its implications in the response of the nucleus to different stimuli.

cell biology↗

bioRxiv2024

3D micropatterned traction force microscopy: a technique to control three-dimensional cell shape while measuring cell-substrate force transmission.

Cell shape and function are intimately linked, in a way that is mediated by the forces exerted between cells and their environment. The relationship between cell shape and forces has been extensively studied for cells seeded on flat 2-dimensional (2D) substrates, but not for cells in more physiological three-dimensional (3D) settings. Here, we demonstrate a technique called 3D micropatterned traction force microscopy (3D-TFM) to confine cells in three-dimensional wells of defined shape, while simultaneously measuring the forces transmitted between cells and their microenvironment. This technique is based on the 3D micropatterning of polyacrylamide wells and on the calculation of 3D traction force from their deformation. With 3D-TFM, we show that MCF10A breast epithelial cells exert defined, reproducible patterns of forces on their microenvironment, which can be both contractile and extensile. We further show that cells switch from a global contractile to extensile behaviour as their volume is reduced. Our technique enables the quantitative study of cell mechanobiology with full access to 3D cellular forces while having accurate control over cell morphology and the mechanical conditions of the microenvironment.

bioengineering↗

bioRxiv2024

Cell-matrix force transmission regulates the loss of naïve pluripotency in mouse embryonic stem cells.

The first step in the differentiation of mouse embryonic stem cells (mESCs) is the loss of naive pluripotency. This step involves a major reshaping of cells from a rounded to a spread, adhesive phenotype. Whereas such reshaping is typically associated with increased force transmission to the extracellular matrix (ECM), the magnitude and role of cell-matrix forces in the loss of naive pluripotency is unknown. Here, we show that cell-matrix forces increase during, and are required for, the loss of naive pluripotency in mESCs. Using traction force microscopy, we show that mESCs progressively increase cell-traction forces and mechanotransduction markers as naive pluripotency dissolves. Modulation of force transmission through myosin inhibition, substrate stiffness, or spatial differences within mESC colonies regulates the process. Increased force is triggered by GSK3-mediated signalling, and the effect of force is regulated in part by its transmission to the cell nucleus. Our work unveils a major role of cell-ECM forces in pluripotency dissolution, adding an important aspect to the interplay between biochemical and biophysical cues that drive this process.

developmental biology↗

bioRxiv2024

Optogenetic generation of leader cells reveals a force-velocity relation for collective cell migration

The front of migratory cellular clusters during development, wound healing and cancer invasion is typically populated with highly protrusive cells that are called leader cells. Leader cells are thought to physically pull and direct their cohort of followers, but how leaders and followers are mechanically organized to migrate collectively remains controversial. One possibility is that the autonomous local action of a leader cell is sufficient to drive migration of the group. Yet another possibility is that a global mechanical organization is required for the group to move cohesively. Here we show that the effectiveness of leader-follower organization is proportional to the asymmetry of traction and tension within the cellular cluster. By combining hydrogel micropatterning and optogenetic activation of Rac1, we locally generate highly protrusive leaders at the edge of minimal cell groups. We find that the induced leader can robustly drag one follower but is generally unable to direct larger groups. By measuring traction forces and tension propagation in groups of increasing size, we establish a quantitative relationship between group velocity and the asymmetry of the traction and tension profiles. We propose a model of the motile cluster as an active polar fluid that explains this force-velocity relationship in terms of asymmetries in the distribution of active tractions. Our results challenge the notion of autonomous leader cells by showing that collective cell migration requires a global mechanical organization within the cluster.

cell biology↗

bioRxiv2024

Nucleocytoplasmic transport senses mechanics independently of cell density in cell monolayers.

Cells sense and respond to mechanical forces through mechanotransduction, which regulates processes in health and disease. In single cells, mechanotransduction involves the transmission of force to the cell nucleus, where it affects nucleocytoplasmic transport (NCT) and the subsequent nuclear localization of transcriptional regulators such as YAP. However, if and how NCT is mechanosensitive in multicellular systems is unclear. Here, we characterize and use a fluorescent sensor of nucleocytoplasmic transport (Sencyt) and demonstrate that nucleocytoplasmic transport responds to mechanics but not cell density in cell monolayers. Using monolayers of both epithelial and mesenchymal phenotype, we show that NCT is altered in response both to osmotic shocks, and to the inhibition of cell contractility. Further, NCT correlates with the degree of nuclear deformation measured through nuclear solidity, a shape parameter related to nuclear envelope tension. In contrast and in opposition to YAP, NCT is not affected by cell density, showing that the response of YAP to both mechanics and cell-cell contacts operates through distinct mechanisms. Our results demonstrate the generality of the mechanical regulation of NCT.

cell biology↗

bioRxiv2023

Membrane to cortex attachment determines different mechanical phenotypes in LGR5+ and LGR5- colorectal cancer cells

Colorectal cancer tumors are composed of heterogeneous and plastic cell populations, including a pool of cancer stem cells that express LGR5. Whether these distinct cell populations display different mechanical properties, and how these properties might contribute to metastasis is unknown. Using CRC patient derived organoids (PDOs), we found that compared to LGR5- cells, LGR5+ cancer stem cells are stiffer, adhere better to the extracellular matrix (ECM), move slower both as single cells and clusters, display higher nuclear YAP, show a higher survival rate in response to mechanical confinement, and form larger transendothelial gaps. These differences are largely explained by the downregulation of the membrane to cortex attachment proteins Ezrin/Radixin/Moesin (ERMs) in the LGR5+ cells. By analyzing scRNA-seq expression patterns from a patient cohort, we show that this downregulation is a robust signature of colorectal tumors. Our results show that LGR5- cells display a mechanically dynamic phenotype suitable for dissemination from the primary tumor whereas LGR5+ cells display a mechanically stable and resilient phenotype suitable for extravasation and metastatic growth.

cancer biology↗

bioRxiv2023

Fibrillar adhesion dynamics govern the timescales of nuclear mechano-response via the vimentin cytoskeleton

The cell nucleus is continuously exposed to external signals, of both chemical and mechanical nature. To ensure proper cellular response, cells need to regulate not only the transmission of these signals, but also their timing and duration. Such timescale regulation is well described for fluctuating chemical signals, but if and how it applies to mechanical signals reaching the nucleus is still unknown. Here we demonstrate that the formation of fibrillar adhesions locks the nucleus in a mechanically deformed conformation, setting the mechanical response timescale to that of fibrillar adhesion remodelling ([~]1 hour). This process encompasses both mechanical deformation and associated mechanotransduction (such as via YAP), in response to both increased and decreased mechanical stimulation. The underlying mechanism is the anchoring of the vimentin cytoskeleton to fibrillar adhesions and the extracellular matrix through plectin 1f, which maintains nuclear deformation. Our results reveal a mechanism to regulate the timescale of mechanical adaptation, effectively setting a low pass filter to mechanotransduction.

biophysics↗

bioRxiv2022

Cell response to extracellular matrix energy dissipation outweighs rigidity sensing

The mechanical properties of the extracellular matrix (ECM) determine cell differentiation, proliferation and migration through mechanoresponsive proteins including YAP. However, how different mechanical signals cooperate, synergize or compete to steer cell behavior remains poorly understood. Here, we have examined competition between the two major ECM mechanical cues, i.e. rigidity, which activates cell mechanosensing, and viscous energy dissipation, which reduces stiffness blunting cell mechanotransduction. To trigger competition, we have engineered protein hydrogels allowing concomitant modulation of stiffness and viscosity by mechanisms characteristic of native ECM. Culturing cells on these hydrogels, we have found that substrate energy dissipation attenuates YAP mechanosensing prevailing over stiffness cues. Hampered YAP activation on more dissipative substrates correlates with faster actin flow and smaller focal adhesions. Mechanistically, inhibition of actomyosin contractility reverses the outcome of the competition between rigidity and energy dissipation. Our results highlight the dominating contribution of substrate viscosity to the biology of the cell.

bioengineering↗

bioRxiv2022

Stiffness-dependent active wetting enables optimal collective cell durotaxis

The directed migration of cellular clusters enables morphogenesis, wound healing, and collective cancer invasion. Gradients of substrate stiffness are known to direct the migration of cellular clusters in a process called collective durotaxis, but underlying mechanisms remain unclear. Here, we unveil a connection between collective durotaxis and the wetting properties of cellular clusters. We show that clusters of cancer cells dewet soft substrates and wet stiff ones. At intermediate stiffness, at the crossover from low to high wettability, clusters on uniform-stiffness substrates become maximally motile, and clusters on stiffness gradients exhibit optimal durotaxis. Durotactic velocity increases with cluster size, stiffness gradient, and actomyosin activity. We demonstrate this behavior on substrates coated with the cell-cell adhesion protein E-cadherin and then establish its generality on substrates coated with extracellular matrix. We develop a physical model of three-dimensional active wetting that explains this mode of collective durotaxis in terms of a balance between in-plane active traction and tissue contractility, and out-of-plane surface tension. Finally, we show that the distribution of cluster displacements has a heavy tail, with infrequent but large cellular hops that contribute to durotactic migration. Our study demonstrates a physical mechanism of collective durotaxis, through both cell-cell and cell-substrate adhesion ligands, based on the wetting properties of active droplets.

biophysics↗

bioRxiv2022

Regulation of cell dynamics by rapid transport of integrins through the biosynthetic pathway

Cells sense and respond to the extracellular matrix (ECM) milieu through integrin proteins. Integrin availability on the plasma membrane, regulated by endosomal receptor uptake and recycling, has been extensively studied and regulates cell dynamics in various normal and pathological contexts1-5. In contrast, the role of integrin transport through the biosynthetic pathway has been considered primarily as a mechanism to replenish the receptor pool and too slow to influence cell dynamics6. Here, we adopted the RUSH (Retention Using Selective Hooks) assay to synchronize integrin anterograde transport from the endoplasmic reticulum (ER), allowing spatial and temporal analysis of newly synthesized receptor traffic. We observe that the delivery of new integrins to the plasma membrane is polarized in response to specific ECM ligands, facilitates integrin recruitment specifically to the membrane-proximal tip of focal adhesions (FA) and contributes to cell protrusion and FA growth. We explain the augmented adhesion growth using a computational molecular clutch model7, where increased integrin availability drives recruitment of additional integrins. Notably, a subset of newly synthesized integrins undergo rapid traffic from the ER to the cell surface to facilitate localized cell spreading, seemingly bypassing the Golgi. This unconventional secretion is dependent on cell adhesion and mediated by Golgi reassembling stacking proteins (GRASPs) association with the PDZ-binding motif in the integrin 5 cytoplasmic tail. This spatially targeted delivery of integrins through the biosynthetic pathway may propel cell dynamics by rapidly altering adhesion receptor availability, providing cells with an additional degree of plasticity to respond to their environment.

cell biology↗

bioRxiv2022

Mapping mechanical stress in curved epithelia of designed size and shape

The function of organs such as lungs, kidneys and mammary glands relies on the three-dimensional geometry of their epithelium. To adopt shapes such as spheres, tubes and ellipsoids, epithelia generate mechanical stresses that are generally unknown. Here we engineered curved epithelial monolayers of controlled size and shape and mapped their state of stress. We designed pressurized epithelia with circular, rectangular and ellipsoidal footprints. We developed a computational method to map the stress tensor in these epithelia. This method establishes a direct correspondence between epithelial shape and mechanical stress without assumptions of material properties. In epithelia with spherical geometry spanning more than one order of magnitude in radius, we show that stress weakly increases with areal strain in a size-independent manner. In epithelia with rectangular and ellipsoidal cross-section we found pronounced stress anisotropies consistent with the asymmetric distribution of tractions measured at the cell-substrate contact line. In these anisotropic profiles, cell shape tended to align with the direction of maximum principal stress but this alignment was non-universal and depended on epithelial geometry. Besides interrogating the fundamental mechanics of epithelia over a broad range of sizes and shapes, our approach will enable a systematic study of how geometry and stress influence epithelial fate and function in three-dimensions.

biophysics↗