TY - JOUR AB - Metazoan development relies on the formation and remodeling of cell-cell contacts. Dynamic reorganization of adhesion receptors and the actomyosin cell cortex in space and time plays a central role in cell-cell contact formation and maturation. Nevertheless, how this process is mechanistically achieved when new contacts are formed remains unclear. Here, by building a biomimetic assay composed of progenitor cells adhering to supported lipid bilayers functionalized with E-cadherin ectodomains, we show that cortical F-actin flows, driven by the depletion of myosin-2 at the cell contact center, mediate the dynamic reorganization of adhesion receptors and cell cortex at the contact. E-cadherin-dependent downregulation of the small GTPase RhoA at the forming contact leads to both a depletion of myosin-2 and a decrease of F-actin at the contact center. At the contact rim, in contrast, myosin-2 becomes enriched by the retraction of bleb-like protrusions, resulting in a cortical tension gradient from the contact rim to its center. This tension gradient, in turn, triggers centrifugal F-actin flows, leading to further accumulation of F-actin at the contact rim and the progressive redistribution of E-cadherin from the contact center to the rim. Eventually, this combination of actomyosin downregulation and flows at the contact determines the characteristic molecular organization, with E-cadherin and F-actin accumulating at the contact rim, where they are needed to mechanically link the contractile cortices of the adhering cells. AU - Arslan, Feyza N AU - Hannezo, Edouard B AU - Merrin, Jack AU - Loose, Martin AU - Heisenberg, Carl-Philipp J ID - 14795 IS - 1 JF - Current Biology SN - 0960-9822 TI - Adhesion-induced cortical flows pattern E-cadherin-mediated cell contacts VL - 34 ER - TY - CHAP AB - The mammary gland consists of a bilayered epithelial structure with an extensively branched morphology. The majority of this epithelial tree is laid down during puberty, during which actively proliferating terminal end buds repeatedly elongate and bifurcate to form the basic structure of the ductal tree. Mammary ducts consist of a basal and luminal cell layer with a multitude of identified sub-lineages within both layers. The understanding of how these different cell lineages are cooperatively driving branching morphogenesis is a problem of crossing multiple scales, as this requires information on the macroscopic branched structure of the gland, as well as data on single-cell dynamics driving the morphogenic program. Here we describe a method to combine genetic lineage tracing with whole-gland branching analysis. Quantitative data on the global organ structure can be used to derive a model for mammary gland branching morphogenesis and provide a backbone on which the dynamics of individual cell lineages can be simulated and compared to lineage-tracing approaches. Eventually, these quantitative models and experiments allow to understand the couplings between the macroscopic shape of the mammary gland and the underlying single-cell dynamics driving branching morphogenesis. AU - Hannezo, Edouard B AU - Scheele, Colinda L.G.J. ED - Margadant, Coert ID - 12428 SN - 9781071628867 T2 - Cell Migration in Three Dimensions TI - A Guide Toward Multi-scale and Quantitative Branching Analysis in the Mammary Gland VL - 2608 ER - TY - JOUR AB - Living tissues are characterized by an intrinsically mechanochemical interplay of active physical forces and complex biochemical signaling pathways. Either feature alone can give rise to complex emergent phenomena, for example, mechanically driven glassy dynamics and rigidity transitions, or chemically driven reaction-diffusion instabilities. An important question is how to quantitatively assess the contribution of these different cues to the large-scale dynamics of biological materials. We address this in Madin-Darby canine kidney (MDCK) monolayers, considering both mechanochemical feedback between extracellular signal-regulated kinase (ERK) signaling activity and cellular density as well as a mechanically active tissue rheology via a self-propelled vertex model. We show that the relative strength of active migration forces to mechanochemical couplings controls a transition from a uniform active glass to periodic spatiotemporal waves. We parametrize the model from published experimental data sets on MDCK monolayers and use it to make new predictions on the correlation functions of cellular dynamics and the dynamics of topological defects associated with the oscillatory phase of cells. Interestingly, MDCK monolayers are best described by an intermediary parameter region in which both mechanochemical couplings and noisy active propulsion have a strong influence on the dynamics. Finally, we study how tissue rheology and ERK waves produce feedback on one another and uncover a mechanism via which tissue fluidity can be controlled by mechanochemical waves at both the local and global levels. AU - Boocock, Daniel R AU - Hirashima, Tsuyoshi AU - Hannezo, Edouard B ID - 14277 IS - 1 JF - PRX Life SN - 2835-8279 TI - Interplay between mechanochemical patterning and glassy dynamics in cellular monolayers VL - 1 ER - TY - JOUR AB - Surface curvature both emerges from, and influences the behavior of, living objects at length scales ranging from cell membranes to single cells to tissues and organs. The relevance of surface curvature in biology is supported by numerous experimental and theoretical investigations in recent years. In this review, first, a brief introduction to the key ideas of surface curvature in the context of biological systems is given and the challenges that arise when measuring surface curvature are discussed. Giving an overview of the emergence of curvature in biological systems, its significance at different length scales becomes apparent. On the other hand, summarizing current findings also shows that both single cells and entire cell sheets, tissues or organisms respond to curvature by modulating their shape and their migration behavior. Finally, the interplay between the distribution of morphogens or micro-organisms and the emergence of curvature across length scales is addressed with examples demonstrating these key mechanistic principles of morphogenesis. Overall, this review highlights that curved interfaces are not merely a passive by-product of the chemical, biological, and mechanical processes but that curvature acts also as a signal that co-determines these processes. AU - Schamberger, Barbara AU - Ziege, Ricardo AU - Anselme, Karine AU - Ben Amar, Martine AU - Bykowski, Michał AU - Castro, André P.G. AU - Cipitria, Amaia AU - Coles, Rhoslyn A. AU - Dimova, Rumiana AU - Eder, Michaela AU - Ehrig, Sebastian AU - Escudero, Luis M. AU - Evans, Myfanwy E. AU - Fernandes, Paulo R. AU - Fratzl, Peter AU - Geris, Liesbet AU - Gierlinger, Notburga AU - Hannezo, Edouard B AU - Iglič, Aleš AU - Kirkensgaard, Jacob J.K. AU - Kollmannsberger, Philip AU - Kowalewska, Łucja AU - Kurniawan, Nicholas A. AU - Papantoniou, Ioannis AU - Pieuchot, Laurent AU - Pires, Tiago H.V. AU - Renner, Lars D. AU - Sageman-Furnas, Andrew O. AU - Schröder-Turk, Gerd E. AU - Sengupta, Anupam AU - Sharma, Vikas R. AU - Tagua, Antonio AU - Tomba, Caterina AU - Trepat, Xavier AU - Waters, Sarah L. AU - Yeo, Edwina F. AU - Roschger, Andreas AU - Bidan, Cécile M. AU - Dunlop, John W.C. ID - 12710 IS - 13 JF - Advanced Materials SN - 0935-9648 TI - Curvature in biological systems: Its quantification, emergence, and implications across the scales VL - 35 ER - TY - JOUR AB - As developing tissues grow in size and undergo morphogenetic changes, their material properties may be altered. Such changes result from tension dynamics at cell contacts or cellular jamming. Yet, in many cases, the cellular mechanisms controlling the physical state of growing tissues are unclear. We found that at early developmental stages, the epithelium in the developing mouse spinal cord maintains both high junctional tension and high fluidity. This is achieved via a mechanism in which interkinetic nuclear movements generate cell area dynamics that drive extensive cell rearrangements. Over time, the cell proliferation rate declines, effectively solidifying the tissue. Thus, unlike well-studied jamming transitions, the solidification uncovered here resembles a glass transition that depends on the dynamical stresses generated by proliferation and differentiation. Our finding that the fluidity of developing epithelia is linked to interkinetic nuclear movements and the dynamics of growth is likely to be relevant to multiple developing tissues. AU - Bocanegra, Laura AU - Singh, Amrita AU - Hannezo, Edouard B AU - Zagórski, Marcin P AU - Kicheva, Anna ID - 12837 JF - Nature Physics SN - 1745-2473 TI - Cell cycle dynamics control fluidity of the developing mouse neuroepithelium VL - 19 ER - TY - JOUR AB - To meet the physiological demands of the body, organs need to establish a functional tissue architecture and adequate size as the embryo develops to adulthood. In the liver, uni- and bipotent progenitor differentiation into hepatocytes and biliary epithelial cells (BECs), and their relative proportions, comprise the functional architecture. Yet, the contribution of individual liver progenitors at the organ level to both fates, and their specific proportion, is unresolved. Combining mathematical modelling with organ-wide, multispectral FRaeppli-NLS lineage tracing in zebrafish, we demonstrate that a precise BEC-to-hepatocyte ratio is established (i) fast, (ii) solely by heterogeneous lineage decisions from uni- and bipotent progenitors, and (iii) independent of subsequent cell type–specific proliferation. Extending lineage tracing to adulthood determined that embryonic cells undergo spatially heterogeneous three-dimensional growth associated with distinct environments. Strikingly, giant clusters comprising almost half a ventral lobe suggest lobe-specific dominant-like growth behaviours. We show substantial hepatocyte polyploidy in juveniles representing another hallmark of postembryonic liver growth. Our findings uncover heterogeneous progenitor contributions to tissue architecture-defining cell type proportions and postembryonic organ growth as key mechanisms forming the adult liver. AU - Unterweger, Iris A. AU - Klepstad, Julie AU - Hannezo, Edouard B AU - Lundegaard, Pia R. AU - Trusina, Ala AU - Ober, Elke A. ID - 14426 IS - 10 JF - PLoS Biology TI - Lineage tracing identifies heterogeneous hepatoblast contribution to cell lineages and postembryonic organ growth dynamics VL - 21 ER - TY - JOUR AB - Branching morphogenesis is a ubiquitous process that gives rise to high exchange surfaces in the vasculature and epithelial organs. Lymphatic capillaries form branched networks, which play a key role in the circulation of tissue fluid and immune cells. Although mouse models and correlative patient data indicate that the lymphatic capillary density directly correlates with functional output, i.e., tissue fluid drainage and trafficking efficiency of dendritic cells, the mechanisms ensuring efficient tissue coverage remain poorly understood. Here, we use the mouse ear pinna lymphatic vessel network as a model system and combine lineage-tracing, genetic perturbations, whole-organ reconstructions and theoretical modeling to show that the dermal lymphatic capillaries tile space in an optimal, space-filling manner. This coverage is achieved by two complementary mechanisms: initial tissue invasion provides a non-optimal global scaffold via self-organized branching morphogenesis, while VEGF-C dependent side-branching from existing capillaries rapidly optimizes local coverage by directionally targeting low-density regions. With these two ingredients, we show that a minimal biophysical model can reproduce quantitatively whole-network reconstructions, across development and perturbations. Our results show that lymphatic capillary networks can exploit local self-organizing mechanisms to achieve tissue-scale optimization. AU - Ucar, Mehmet C AU - Hannezo, Edouard B AU - Tiilikainen, Emmi AU - Liaqat, Inam AU - Jakobsson, Emma AU - Nurmi, Harri AU - Vaahtomeri, Kari ID - 14378 JF - Nature Communications TI - Self-organized and directed branching results in optimal coverage in developing dermal lymphatic networks VL - 14 ER - TY - JOUR AB - Immune responses rely on the rapid and coordinated migration of leukocytes. Whereas it is well established that single-cell migration is often guided by gradients of chemokines and other chemoattractants, it remains poorly understood how these gradients are generated, maintained, and modulated. By combining experimental data with theory on leukocyte chemotaxis guided by the G protein–coupled receptor (GPCR) CCR7, we demonstrate that in addition to its role as the sensory receptor that steers migration, CCR7 also acts as a generator and a modulator of chemotactic gradients. Upon exposure to the CCR7 ligand CCL19, dendritic cells (DCs) effectively internalize the receptor and ligand as part of the canonical GPCR desensitization response. We show that CCR7 internalization also acts as an effective sink for the chemoattractant, dynamically shaping the spatiotemporal distribution of the chemokine. This mechanism drives complex collective migration patterns, enabling DCs to create or sharpen chemotactic gradients. We further show that these self-generated gradients can sustain the long-range guidance of DCs, adapt collective migration patterns to the size and geometry of the environment, and provide a guidance cue for other comigrating cells. Such a dual role of CCR7 as a GPCR that both senses and consumes its ligand can thus provide a novel mode of cellular self-organization. AU - Alanko, Jonna H AU - Ucar, Mehmet C AU - Canigova, Nikola AU - Stopp, Julian A AU - Schwarz, Jan AU - Merrin, Jack AU - Hannezo, Edouard B AU - Sixt, Michael K ID - 14274 IS - 87 JF - Science Immunology KW - General Medicine KW - Immunology SN - 2470-9468 TI - CCR7 acts as both a sensor and a sink for CCL19 to coordinate collective leukocyte migration VL - 8 ER - TY - JOUR AB - Homeostatic balance in the intestinal epithelium relies on a fast cellular turnover, which is coordinated by an intricate interplay between biochemical signalling, mechanical forces and organ geometry. We review recent modelling approaches that have been developed to understand different facets of this remarkable homeostatic equilibrium. Existing models offer different, albeit complementary, perspectives on the problem. First, biomechanical models aim to explain the local and global mechanical stresses driving cell renewal as well as tissue shape maintenance. Second, compartmental models provide insights into the conditions necessary to keep a constant flow of cells with well-defined ratios of cell types, and how perturbations can lead to an unbalance of relative compartment sizes. A third family of models address, at the cellular level, the nature and regulation of stem fate choices that are necessary to fuel cellular turnover. We also review how these different approaches are starting to be integrated together across scales, to provide quantitative predictions and new conceptual frameworks to think about the dynamics of cell renewal in complex tissues. AU - Corominas-Murtra, Bernat AU - Hannezo, Edouard B ID - 12162 JF - Seminars in Cell & Developmental Biology KW - Cell Biology KW - Developmental Biology SN - 1084-9521 TI - Modelling the dynamics of mammalian gut homeostasis VL - 150-151 ER - TY - JOUR AB - When in equilibrium, thermal forces agitate molecules, which then diffuse, collide and bind to form materials. However, the space of accessible structures in which micron-scale particles can be organized by thermal forces is limited, owing to the slow dynamics and metastable states. Active agents in a passive fluid generate forces and flows, forming a bath with active fluctuations. Two unanswered questions are whether those active agents can drive the assembly of passive components into unconventional states and which material properties they will exhibit. Here we show that passive, sticky beads immersed in a bath of swimming Escherichia coli bacteria aggregate into unconventional clusters and gels that are controlled by the activity of the bath. We observe a slow but persistent rotation of the aggregates that originates in the chirality of the E. coli flagella and directs aggregation into structures that are not accessible thermally. We elucidate the aggregation mechanism with a numerical model of spinning, sticky beads and reproduce quantitatively the experimental results. We show that internal activity controls the phase diagram and the structure of the aggregates. Overall, our results highlight the promising role of active baths in designing the structural and mechanical properties of materials with unconventional phases. AU - Grober, Daniel AU - Palaia, Ivan AU - Ucar, Mehmet C AU - Hannezo, Edouard B AU - Šarić, Anđela AU - Palacci, Jérémie A ID - 13971 JF - Nature Physics SN - 1745-2473 TI - Unconventional colloidal aggregation in chiral bacterial baths VL - 19 ER - TY - DATA AB - The emergence of large-scale order in self-organized systems relies on local interactions between individual components. During bacterial cell division, FtsZ -- a prokaryotic homologue of the eukaryotic protein tubulin -- polymerizes into treadmilling filaments that further organize into a cytoskeletal ring. In vitro, FtsZ filaments can form dynamic chiral assemblies. However, how the active and passive properties of individual filaments relate to these large-scale self-organized structures remains poorly understood. Here, we connect single filament properties with the mesoscopic scale by combining minimal active matter simulations and biochemical reconstitution experiments. We show that density and flexibility of active chiral filaments define their global order. At intermediate densities, curved, flexible filaments organize into chiral rings and polar bands. An effectively nematic organization dominates for high densities and for straight, mutant filaments with increased rigidity. Our predicted phase diagram captures these features quantitatively, demonstrating how the flexibility, density and chirality of active filaments affect their collective behaviour. Our findings shed light on the fundamental properties of active chiral matter and explain how treadmilling FtsZ filaments organize during bacterial cell division. AU - Dunajova, Zuzana AU - Prats Mateu, Batirtze AU - Radler, Philipp AU - Lim, Keesiang AU - Brandis, Dörte AU - Velicky, Philipp AU - Danzl, Johann G AU - Wong, Richard W. AU - Elgeti, Jens AU - Hannezo, Edouard B AU - Loose, Martin ID - 13116 TI - Chiral and nematic phases of flexible active filaments ER - TY - JOUR AB - The emergence of large-scale order in self-organized systems relies on local interactions between individual components. During bacterial cell division, FtsZ—a prokaryotic homologue of the eukaryotic protein tubulin—polymerizes into treadmilling filaments that further organize into a cytoskeletal ring. In vitro, FtsZ filaments can form dynamic chiral assemblies. However, how the active and passive properties of individual filaments relate to these large-scale self-organized structures remains poorly understood. Here we connect single-filament properties with the mesoscopic scale by combining minimal active matter simulations and biochemical reconstitution experiments. We show that the density and flexibility of active chiral filaments define their global order. At intermediate densities, curved, flexible filaments organize into chiral rings and polar bands. An effectively nematic organization dominates for high densities and for straight, mutant filaments with increased rigidity. Our predicted phase diagram quantitatively captures these features, demonstrating how the flexibility, density and chirality of the active filaments affect their collective behaviour. Our findings shed light on the fundamental properties of active chiral matter and explain how treadmilling FtsZ filaments organize during bacterial cell division. AU - Dunajova, Zuzana AU - Prats Mateu, Batirtze AU - Radler, Philipp AU - Lim, Keesiang AU - Brandis, Dörte AU - Velicky, Philipp AU - Danzl, Johann G AU - Wong, Richard W. AU - Elgeti, Jens AU - Hannezo, Edouard B AU - Loose, Martin ID - 13314 JF - Nature Physics SN - 1745-2473 TI - Chiral and nematic phases of flexible active filaments VL - 19 ER - TY - JOUR AB - Lymph nodes (LNs) comprise two main structural elements: fibroblastic reticular cells that form dedicated niches for immune cell interaction and capsular fibroblasts that build a shell around the organ. Immunological challenge causes LNs to increase more than tenfold in size within a few days. Here, we characterized the biomechanics of LN swelling on the cellular and organ scale. We identified lymphocyte trapping by influx and proliferation as drivers of an outward pressure force, causing fibroblastic reticular cells of the T-zone (TRCs) and their associated conduits to stretch. After an initial phase of relaxation, TRCs sensed the resulting strain through cell matrix adhesions, which coordinated local growth and remodeling of the stromal network. While the expanded TRC network readopted its typical configuration, a massive fibrotic reaction of the organ capsule set in and countered further organ expansion. Thus, different fibroblast populations mechanically control LN swelling in a multitier fashion. AU - Assen, Frank P AU - Abe, Jun AU - Hons, Miroslav AU - Hauschild, Robert AU - Shamipour, Shayan AU - Kaufmann, Walter AU - Costanzo, Tommaso AU - Krens, Gabriel AU - Brown, Markus AU - Ludewig, Burkhard AU - Hippenmeyer, Simon AU - Heisenberg, Carl-Philipp J AU - Weninger, Wolfgang AU - Hannezo, Edouard B AU - Luther, Sanjiv A. AU - Stein, Jens V. AU - Sixt, Michael K ID - 9794 JF - Nature Immunology SN - 1529-2908 TI - Multitier mechanics control stromal adaptations in swelling lymph nodes VL - 23 ER - TY - JOUR AB - Although rigidity and jamming transitions have been widely studied in physics and material science, their importance in a number of biological processes, including embryo development, tissue homeostasis, wound healing, and disease progression, has only begun to be recognized in the past few years. The hypothesis that biological systems can undergo rigidity/jamming transitions is attractive, as it would allow these systems to change their material properties rapidly and strongly. However, whether such transitions indeed occur in biological systems, how they are being regulated, and what their physiological relevance might be, is still being debated. Here, we review theoretical and experimental advances from the past few years, focusing on the regulation and role of potential tissue rigidity transitions in different biological processes. AU - Hannezo, Edouard B AU - Heisenberg, Carl-Philipp J ID - 10705 IS - 5 JF - Trends in Cell Biology SN - 0962-8924 TI - Rigidity transitions in development and disease VL - 32 ER - TY - JOUR AB - In development, lineage segregation is coordinated in time and space. An important example is the mammalian inner cell mass, in which the primitive endoderm (PrE, founder of the yolk sac) physically segregates from the epiblast (EPI, founder of the fetus). While the molecular requirements have been well studied, the physical mechanisms determining spatial segregation between EPI and PrE remain elusive. Here, we investigate the mechanical basis of EPI and PrE sorting. We find that rather than the differences in static cell surface mechanical parameters as in classical sorting models, it is the differences in surface fluctuations that robustly ensure physical lineage sorting. These differential surface fluctuations systematically correlate with differential cellular fluidity, which we propose together constitute a non-equilibrium sorting mechanism for EPI and PrE lineages. By combining experiments and modeling, we identify cell surface dynamics as a key factor orchestrating the correct spatial segregation of the founder embryonic lineages. AU - Yanagida, Ayaka AU - Corujo-Simon, Elena AU - Revell, Christopher K. AU - Sahu, Preeti AU - Stirparo, Giuliano G. AU - Aspalter, Irene M. AU - Winkel, Alex K. AU - Peters, Ruby AU - De Belly, Henry AU - Cassani, Davide A.D. AU - Achouri, Sarra AU - Blumenfeld, Raphael AU - Franze, Kristian AU - Hannezo, Edouard B AU - Paluch, Ewa K. AU - Nichols, Jennifer AU - Chalut, Kevin J. ID - 10825 IS - 5 JF - Cell SN - 00928674 TI - Cell surface fluctuations regulate early embryonic lineage sorting VL - 185 ER - TY - JOUR AB - Embryo development requires biochemical signalling to generate patterns of cell fates and active mechanical forces to drive tissue shape changes. However, how these processes are coordinated, and how tissue patterning is preserved despite the cellular flows occurring during morphogenesis, remains poorly understood. Gastrulation is a crucial embryonic stage that involves both patterning and internalization of the mesendoderm germ layer tissue. Here we show that, in zebrafish embryos, a gradient in Nodal signalling orchestrates pattern-preserving internalization movements by triggering a motility-driven unjamming transition. In addition to its role as a morphogen determining embryo patterning, graded Nodal signalling mechanically subdivides the mesendoderm into a small fraction of highly protrusive leader cells, able to autonomously internalize via local unjamming, and less protrusive followers, which need to be pulled inwards by the leaders. The Nodal gradient further enforces a code of preferential adhesion coupling leaders to their immediate followers, resulting in a collective and ordered mode of internalization that preserves mesendoderm patterning. Integrating this dual mechanical role of Nodal signalling into minimal active particle simulations quantitatively predicts both physiological and experimentally perturbed internalization movements. This provides a quantitative framework for how a morphogen-encoded unjamming transition can bidirectionally couple tissue mechanics with patterning during complex three-dimensional morphogenesis. AU - Nunes Pinheiro, Diana C AU - Kardos, Roland AU - Hannezo, Edouard B AU - Heisenberg, Carl-Philipp J ID - 12209 IS - 12 JF - Nature Physics KW - General Physics and Astronomy SN - 1745-2473 TI - Morphogen gradient orchestrates pattern-preserving tissue morphogenesis via motility-driven unjamming VL - 18 ER - TY - JOUR AB - The development dynamics and self-organization of glandular branched epithelia is of utmost importance for our understanding of diverse processes ranging from normal tissue growth to the growth of cancerous tissues. Using single primary murine pancreatic ductal adenocarcinoma (PDAC) cells embedded in a collagen matrix and adapted media supplementation, we generate organoids that self-organize into highly branched structures displaying a seamless lumen connecting terminal end buds, replicating in vivo PDAC architecture. We identify distinct morphogenesis phases, each characterized by a unique pattern of cell invasion, matrix deformation, protein expression, and respective molecular dependencies. We propose a minimal theoretical model of a branching and proliferating tissue, capturing the dynamics of the first phases. Observing the interaction of morphogenesis, mechanical environment and gene expression in vitro sets a benchmark for the understanding of self-organization processes governing complex organoid structure formation processes and branching morphogenesis. AU - Randriamanantsoa, S. AU - Papargyriou, A. AU - Maurer, H. C. AU - Peschke, K. AU - Schuster, M. AU - Zecchin, G. AU - Steiger, K. AU - Öllinger, R. AU - Saur, D. AU - Scheel, C. AU - Rad, R. AU - Hannezo, Edouard B AU - Reichert, M. AU - Bausch, A. R. ID - 12217 JF - Nature Communications KW - General Physics and Astronomy KW - General Biochemistry KW - Genetics and Molecular Biology KW - General Chemistry KW - Multidisciplinary SN - 2041-1723 TI - Spatiotemporal dynamics of self-organized branching in pancreas-derived organoids VL - 13 ER - TY - JOUR AB - The sculpting of germ layers during gastrulation relies on the coordinated migration of progenitor cells, yet the cues controlling these long-range directed movements remain largely unknown. While directional migration often relies on a chemokine gradient generated from a localized source, we find that zebrafish ventrolateral mesoderm is guided by a self-generated gradient of the initially uniformly expressed and secreted protein Toddler/ELABELA/Apela. We show that the Apelin receptor, which is specifically expressed in mesodermal cells, has a dual role during gastrulation, acting as a scavenger receptor to generate a Toddler gradient, and as a chemokine receptor to sense this guidance cue. Thus, we uncover a single receptor–based self-generated gradient as the enigmatic guidance cue that can robustly steer the directional migration of mesoderm through the complex and continuously changing environment of the gastrulating embryo. AU - Stock, Jessica AU - Kazmar, Tomas AU - Schlumm, Friederike AU - Hannezo, Edouard B AU - Pauli, Andrea ID - 12253 IS - 37 JF - Science Advances SN - 2375-2548 TI - A self-generated Toddler gradient guides mesodermal cell migration VL - 8 ER - TY - JOUR AB - Cell migration in confining physiological environments relies on the concerted dynamics of several cellular components, including protrusions, adhesions with the environment, and the cell nucleus. However, it remains poorly understood how the dynamic interplay of these components and the cell polarity determine the emergent migration behavior at the cellular scale. Here, we combine data-driven inference with a mechanistic bottom-up approach to develop a model for protrusion and polarity dynamics in confined cell migration, revealing how the cellular dynamics adapt to confining geometries. Specifically, we use experimental data of joint protrusion-nucleus migration trajectories of cells on confining micropatterns to systematically determine a mechanistic model linking the stochastic dynamics of cell polarity, protrusions, and nucleus. This model indicates that the cellular dynamics adapt to confining constrictions through a switch in the polarity dynamics from a negative to a positive self-reinforcing feedback loop. Our model further reveals how this feedback loop leads to stereotypical cycles of protrusion-nucleus dynamics that drive the migration of the cell through constrictions. These cycles are disrupted upon perturbation of cytoskeletal components, indicating that the positive feedback is controlled by cellular migration mechanisms. Our data-driven theoretical approach therefore identifies polarity feedback adaptation as a key mechanism in confined cell migration. AU - Brückner, David AU - Schmitt, Matthew AU - Fink, Alexandra AU - Ladurner, Georg AU - Flommersfeld, Johannes AU - Arlt, Nicolas AU - Hannezo, Edouard B AU - Rädler, Joachim O. AU - Broedersz, Chase P. ID - 12277 IS - 3 JF - Physical Review X KW - General Physics and Astronomy SN - 2160-3308 TI - Geometry adaptation of protrusion and polarity dynamics in confined cell migration VL - 12 ER - TY - JOUR AB - The morphology and functionality of the epithelial lining differ along the intestinal tract, but tissue renewal at all sites is driven by stem cells at the base of crypts1,2,3. Whether stem cell numbers and behaviour vary at different sites is unknown. Here we show using intravital microscopy that, despite similarities in the number and distribution of proliferative cells with an Lgr5 signature in mice, small intestinal crypts contain twice as many effective stem cells as large intestinal crypts. We find that, although passively displaced by a conveyor-belt-like upward movement, small intestinal cells positioned away from the crypt base can function as long-term effective stem cells owing to Wnt-dependent retrograde cellular movement. By contrast, the near absence of retrograde movement in the large intestine restricts cell repositioning, leading to a reduction in effective stem cell number. Moreover, after suppression of the retrograde movement in the small intestine, the number of effective stem cells is reduced, and the rate of monoclonal conversion of crypts is accelerated. Together, these results show that the number of effective stem cells is determined by active retrograde movement, revealing a new channel of stem cell regulation that can be experimentally and pharmacologically manipulated. AU - Azkanaz, Maria AU - Corominas-Murtra, Bernat AU - Ellenbroek, Saskia I. J. AU - Bruens, Lotte AU - Webb, Anna T. AU - Laskaris, Dimitrios AU - Oost, Koen C. AU - Lafirenze, Simona J. A. AU - Annusver, Karl AU - Messal, Hendrik A. AU - Iqbal, Sharif AU - Flanagan, Dustin J. AU - Huels, David J. AU - Rojas-Rodríguez, Felipe AU - Vizoso, Miguel AU - Kasper, Maria AU - Sansom, Owen J. AU - Snippert, Hugo J. AU - Liberali, Prisca AU - Simons, Benjamin D. AU - Katajisto, Pekka AU - Hannezo, Edouard B AU - van Rheenen, Jacco ID - 12274 IS - 7919 JF - Nature KW - Multidisciplinary SN - 0028-0836 TI - Retrograde movements determine effective stem cell numbers in the intestine VL - 607 ER - TY - GEN AB - Source data and source code for the graphs in "Spatiotemporal dynamics of self-organized branching pancreatic cancer-derived organoids". AU - Randriamanantsoa, Samuel AU - Papargyriou, Aristeidis AU - Maurer, Carlo AU - Peschke, Katja AU - Schuster, Maximilian AU - Zecchin, Giulia AU - Steiger, Katja AU - Öllinger, Rupert AU - Saur, Dieter AU - Scheel, Christina AU - Rad, Roland AU - Hannezo, Edouard B AU - Reichert, Maximilian AU - Bausch, Andreas R. ID - 13068 TI - Spatiotemporal dynamics of self-organized branching in pancreas-derived organoids ER - TY - JOUR AB - Collective cell migration offers a rich field of study for non-equilibrium physics and cellular biology, revealing phenomena such as glassy dynamics, pattern formation and active turbulence. However, how mechanical and chemical signalling are integrated at the cellular level to give rise to such collective behaviours remains unclear. We address this by focusing on the highly conserved phenomenon of spatiotemporal waves of density and extracellular signal-regulated kinase (ERK) activation, which appear both in vitro and in vivo during collective cell migration and wound healing. First, we propose a biophysical theory, backed by mechanical and optogenetic perturbation experiments, showing that patterns can be quantitatively explained by a mechanochemical coupling between active cellular tensions and the mechanosensitive ERK pathway. Next, we demonstrate how this biophysical mechanism can robustly induce long-ranged order and migration in a desired orientation, and we determine the theoretically optimal wavelength and period for inducing maximal migration towards free edges, which fits well with experimentally observed dynamics. We thereby provide a bridge between the biophysical origin of spatiotemporal instabilities and the design principles of robust and efficient long-ranged migration. AU - Boocock, Daniel R AU - Hino, Naoya AU - Ruzickova, Natalia AU - Hirashima, Tsuyoshi AU - Hannezo, Edouard B ID - 8602 JF - Nature Physics SN - 17452473 TI - Theory of mechanochemical patterning and optimal migration in cell monolayers VL - 17 ER - TY - JOUR AB - Organ function depends on tissues adopting the correct architecture. However, insights into organ architecture are currently hampered by an absence of standardized quantitative 3D analysis. We aimed to develop a robust technology to visualize, digitalize, and segment the architecture of two tubular systems in 3D: double resin casting micro computed tomography (DUCT). As proof of principle, we applied DUCT to a mouse model for Alagille syndrome (Jag1Ndr/Ndr mice), characterized by intrahepatic bile duct paucity, that can spontaneously generate a biliary system in adulthood. DUCT identified increased central biliary branching and peripheral bile duct tortuosity as two compensatory processes occurring in distinct regions of Jag1Ndr/Ndr liver, leading to full reconstitution of wild-type biliary volume and phenotypic recovery. DUCT is thus a powerful new technology for 3D analysis, which can reveal novel phenotypes and provide a standardized method of defining liver architecture in mouse models. AU - Hankeova, Simona AU - Salplachta, Jakub AU - Zikmund, Tomas AU - Kavkova, Michaela AU - Van Hul, Noémi AU - Brinek, Adam AU - Smekalova, Veronika AU - Laznovsky, Jakub AU - Dawit, Feven AU - Jaros, Josef AU - Bryja, Vítězslav AU - Lendahl, Urban AU - Ellis, Ewa AU - Nemeth, Antal AU - Fischler, Björn AU - Hannezo, Edouard B AU - Kaiser, Jozef AU - Andersson, Emma Rachel ID - 9244 JF - eLife TI - DUCT reveals architectural mechanisms contributing to bile duct recovery in a mouse model for alagille syndrome VL - 10 ER - TY - JOUR AB - Assemblies of actin and its regulators underlie the dynamic morphology of all eukaryotic cells. To understand how actin regulatory proteins work together to generate actin-rich structures such as filopodia, we analyzed the localization of diverse actin regulators within filopodia in Drosophila embryos and in a complementary in vitro system of filopodia-like structures (FLSs). We found that the composition of the regulatory protein complex where actin is incorporated (the filopodial tip complex) is remarkably heterogeneous both in vivo and in vitro. Our data reveal that different pairs of proteins correlate with each other and with actin bundle length, suggesting the presence of functional subcomplexes. This is consistent with a theoretical framework where three or more redundant subcomplexes join the tip complex stochastically, with any two being sufficient to drive filopodia formation. We provide an explanation for the observed heterogeneity and suggest that a mechanism based on multiple components allows stereotypical filopodial dynamics to arise from diverse upstream signaling pathways. AU - Dobramysl, Ulrich AU - Jarsch, Iris Katharina AU - Inoue, Yoshiko AU - Shimo, Hanae AU - Richier, Benjamin AU - Gadsby, Jonathan R. AU - Mason, Julia AU - Szałapak, Alicja AU - Ioannou, Pantelis Savvas AU - Correia, Guilherme Pereira AU - Walrant, Astrid AU - Butler, Richard AU - Hannezo, Edouard B AU - Simons, Benjamin D. AU - Gallop, Jennifer L. ID - 9306 IS - 4 JF - Journal of Cell Biology TI - Stochastic combinations of actin regulatory proteins are sufficient to drive filopodia formation VL - 220 ER - TY - JOUR AB - Embryo morphogenesis is impacted by dynamic changes in tissue material properties, which have been proposed to occur via processes akin to phase transitions (PTs). Here, we show that rigidity percolation provides a simple and robust theoretical framework to predict material/structural PTs of embryonic tissues from local cell connectivity. By using percolation theory, combined with directly monitoring dynamic changes in tissue rheology and cell contact mechanics, we demonstrate that the zebrafish blastoderm undergoes a genuine rigidity PT, brought about by a small reduction in adhesion-dependent cell connectivity below a critical value. We quantitatively predict and experimentally verify hallmarks of PTs, including power-law exponents and associated discontinuities of macroscopic observables. Finally, we show that this uniform PT depends on blastoderm cells undergoing meta-synchronous divisions causing random and, consequently, uniform changes in cell connectivity. Collectively, our theoretical and experimental findings reveal the structural basis of material PTs in an organismal context. AU - Petridou, Nicoletta AU - Corominas-Murtra, Bernat AU - Heisenberg, Carl-Philipp J AU - Hannezo, Edouard B ID - 9316 IS - 7 JF - Cell SN - 00928674 TI - Rigidity percolation uncovers a structural basis for embryonic tissue phase transitions VL - 184 ER - TY - JOUR AB - The way in which interactions between mechanics and biochemistry lead to the emergence of complex cell and tissue organization is an old question that has recently attracted renewed interest from biologists, physicists, mathematicians and computer scientists. Rapid advances in optical physics, microscopy and computational image analysis have greatly enhanced our ability to observe and quantify spatiotemporal patterns of signalling, force generation, deformation, and flow in living cells and tissues. Powerful new tools for genetic, biophysical and optogenetic manipulation are allowing us to perturb the underlying machinery that generates these patterns in increasingly sophisticated ways. Rapid advances in theory and computing have made it possible to construct predictive models that describe how cell and tissue organization and dynamics emerge from the local coupling of biochemistry and mechanics. Together, these advances have opened up a wealth of new opportunities to explore how mechanochemical patterning shapes organismal development. In this roadmap, we present a series of forward-looking case studies on mechanochemical patterning in development, written by scientists working at the interface between the physical and biological sciences, and covering a wide range of spatial and temporal scales, organisms, and modes of development. Together, these contributions highlight the many ways in which the dynamic coupling of mechanics and biochemistry shapes biological dynamics: from mechanoenzymes that sense force to tune their activity and motor output, to collectives of cells in tissues that flow and redistribute biochemical signals during development. AU - Lenne, Pierre François AU - Munro, Edwin AU - Heemskerk, Idse AU - Warmflash, Aryeh AU - Bocanegra, Laura AU - Kishi, Kasumi AU - Kicheva, Anna AU - Long, Yuchen AU - Fruleux, Antoine AU - Boudaoud, Arezki AU - Saunders, Timothy E. AU - Caldarelli, Paolo AU - Michaut, Arthur AU - Gros, Jerome AU - Maroudas-Sacks, Yonit AU - Keren, Kinneret AU - Hannezo, Edouard B AU - Gartner, Zev J. AU - Stormo, Benjamin AU - Gladfelter, Amy AU - Rodrigues, Alan AU - Shyer, Amy AU - Minc, Nicolas AU - Maître, Jean Léon AU - Di Talia, Stefano AU - Khamaisi, Bassma AU - Sprinzak, David AU - Tlili, Sham ID - 9349 IS - 4 JF - Physical biology TI - Roadmap for the multiscale coupling of biochemical and mechanical signals during development VL - 18 ER - TY - JOUR AB - Intestinal organoids derived from single cells undergo complex crypt–villus patterning and morphogenesis. However, the nature and coordination of the underlying forces remains poorly characterized. Here, using light-sheet microscopy and large-scale imaging quantification, we demonstrate that crypt formation coincides with a stark reduction in lumen volume. We develop a 3D biophysical model to computationally screen different mechanical scenarios of crypt morphogenesis. Combining this with live-imaging data and multiple mechanical perturbations, we show that actomyosin-driven crypt apical contraction and villus basal tension work synergistically with lumen volume reduction to drive crypt morphogenesis, and demonstrate the existence of a critical point in differential tensions above which crypt morphology becomes robust to volume changes. Finally, we identified a sodium/glucose cotransporter that is specific to differentiated enterocytes that modulates lumen volume reduction through cell swelling in the villus region. Together, our study uncovers the cellular basis of how cell fate modulates osmotic and actomyosin forces to coordinate robust morphogenesis. AU - Yang, Qiutan AU - Xue, Shi-lei AU - Chan, Chii Jou AU - Rempfler, Markus AU - Vischi, Dario AU - Maurer-Gutierrez, Francisca AU - Hiiragi, Takashi AU - Hannezo, Edouard B AU - Liberali, Prisca ID - 9629 JF - Nature Cell Biology SN - 1465-7392 TI - Cell fate coordinates mechano-osmotic forces in intestinal crypt formation VL - 23 ER - TY - JOUR AB - Proper control of division orientation and symmetry, largely determined by spindle positioning, is essential to development and homeostasis. Spindle positioning has been extensively studied in cells dividing in two-dimensional (2D) environments and in epithelial tissues, where proteins such as NuMA (also known as NUMA1) orient division along the interphase long axis of the cell. However, little is known about how cells control spindle positioning in three-dimensional (3D) environments, such as early mammalian embryos and a variety of adult tissues. Here, we use mouse embryonic stem cells (ESCs), which grow in 3D colonies, as a model to investigate division in 3D. We observe that, at the periphery of 3D colonies, ESCs display high spindle mobility and divide asymmetrically. Our data suggest that enhanced spindle movements are due to unequal distribution of the cell–cell junction protein E-cadherin between future daughter cells. Interestingly, when cells progress towards differentiation, division becomes more symmetric, with more elongated shapes in metaphase and enhanced cortical NuMA recruitment in anaphase. Altogether, this study suggests that in 3D contexts, the geometry of the cell and its contacts with neighbors control division orientation and symmetry. AU - Chaigne, Agathe AU - Smith, Matthew B. AU - Cavestany, R. L. AU - Hannezo, Edouard B AU - Chalut, Kevin J. AU - Paluch, Ewa K. ID - 9952 IS - 14 JF - Journal of Cell Science SN - 00219533 TI - Three-dimensional geometry controls division symmetry in stem cell colonies VL - 134 ER - TY - JOUR AB - Branching morphogenesis governs the formation of many organs such as lung, kidney, and the neurovascular system. Many studies have explored system-specific molecular and cellular regulatory mechanisms, as well as self-organizing rules underlying branching morphogenesis. However, in addition to local cues, branched tissue growth can also be influenced by global guidance. Here, we develop a theoretical framework for a stochastic self-organized branching process in the presence of external cues. Combining analytical theory with numerical simulations, we predict differential signatures of global vs. local regulatory mechanisms on the branching pattern, such as angle distributions, domain size, and space-filling efficiency. We find that branch alignment follows a generic scaling law determined by the strength of global guidance, while local interactions influence the tissue density but not its overall territory. Finally, using zebrafish innervation as a model system, we test these key features of the model experimentally. Our work thus provides quantitative predictions to disentangle the role of different types of cues in shaping branched structures across scales. AU - Ucar, Mehmet C AU - Kamenev, Dmitrii AU - Sunadome, Kazunori AU - Fachet, Dominik C AU - Lallemend, Francois AU - Adameyko, Igor AU - Hadjab, Saida AU - Hannezo, Edouard B ID - 10402 JF - Nature Communications TI - Theory of branching morphogenesis by local interactions and global guidance VL - 12 ER - TY - JOUR AB - How tissues acquire complex shapes is a fundamental question in biology and regenerative medicine. Zebrafish semicircular canals form from invaginations in the otic epithelium (buds) that extend and fuse to form the hubs of each canal. We find that conventional actomyosin-driven behaviors are not required. Instead, local secretion of hyaluronan, made by the enzymes uridine 5′-diphosphate dehydrogenase (ugdh) and hyaluronan synthase 3 (has3), drives canal morphogenesis. Charged hyaluronate polymers osmotically swell with water and generate isotropic extracellular pressure to deform the overlying epithelium into buds. The mechanical anisotropy needed to shape buds into tubes is conferred by a polarized distribution of actomyosin and E-cadherin-rich membrane tethers, which we term cytocinches. Most work on tissue morphogenesis ascribes actomyosin contractility as the driving force, while the extracellular matrix shapes tissues through differential stiffness. Our work inverts this expectation. Hyaluronate pressure shaped by anisotropic tissue stiffness may be a widespread mechanism for powering morphological change in organogenesis and tissue engineering. AU - Munjal, Akankshi AU - Hannezo, Edouard B AU - Tsai, Tony Y.C. AU - Mitchison, Timothy J. AU - Megason, Sean G. ID - 10573 IS - 26 JF - Cell SN - 0092-8674 TI - Extracellular hyaluronate pressure shaped by cellular tethers drives tissue morphogenesis VL - 184 ER - TY - JOUR AB - The early development of many organisms involves the folding of cell monolayers, but this behaviour is difficult to reproduce in vitro; therefore, both mechanistic causes and effects of local curvature remain unclear. Here we study epithelial cell monolayers on corrugated hydrogels engineered into wavy patterns, examining how concave and convex curvatures affect cellular and nuclear shape. We find that substrate curvature affects monolayer thickness, which is larger in valleys than crests. We show that this feature generically arises in a vertex model, leading to the hypothesis that cells may sense curvature by modifying the thickness of the tissue. We find that local curvature also affects nuclear morphology and positioning, which we explain by extending the vertex model to take into account membrane–nucleus interactions, encoding thickness modulation in changes to nuclear deformation and position. We propose that curvature governs the spatial distribution of yes-associated proteins via nuclear shape and density changes. We show that curvature also induces significant variations in lamins, chromatin condensation and cell proliferation rate in folded epithelial tissues. Together, this work identifies active cell mechanics and nuclear mechanoadaptation as the key players of the mechanistic regulation of epithelia to substrate curvature. AU - Luciano, Marine AU - Xue, Shi-lei AU - De Vos, Winnok H. AU - Redondo-Morata, Lorena AU - Surin, Mathieu AU - Lafont, Frank AU - Hannezo, Edouard B AU - Gabriele, Sylvain ID - 10365 IS - 12 JF - Nature Physics SN - 1745-2473 TI - Cell monolayers sense curvature by exploiting active mechanics and nuclear mechanoadaptation VL - 17 ER - TY - JOUR AB - During embryonic and postnatal development, organs and tissues grow steadily to achieve their final size at the end of puberty. However, little is known about the cellular dynamics that mediate postnatal growth. By combining in vivo clonal lineage tracing, proliferation kinetics, single-cell transcriptomics, andin vitro micro-pattern experiments, we resolved the cellular dynamics taking place during postnatal skin epidermis expansion. Our data revealed that harmonious growth is engineered by a single population of developmental progenitors presenting a fixed fate imbalance of self-renewing divisions with an ever-decreasing proliferation rate. Single-cell RNA sequencing revealed that epidermal developmental progenitors form a more uniform population compared with adult stem and progenitor cells. Finally, we found that the spatial pattern of cell division orientation is dictated locally by the underlying collagen fiber orientation. Our results uncover a simple design principle of organ growth where progenitors and differentiated cells expand in harmony with their surrounding tissues. AU - Dekoninck, Sophie AU - Hannezo, Edouard B AU - Sifrim, Alejandro AU - Miroshnikova, Yekaterina A. AU - Aragona, Mariaceleste AU - Malfait, Milan AU - Gargouri, Souhir AU - De Neunheuser, Charlotte AU - Dubois, Christine AU - Voet, Thierry AU - Wickström, Sara A. AU - Simons, Benjamin D. AU - Blanpain, Cédric ID - 7789 IS - 3 JF - Cell SN - 00928674 TI - Defining the design principles of skin epidermis postnatal growth VL - 181 ER - TY - JOUR AB - Understanding to what extent stem cell potential is a cell-intrinsic property or an emergent behavior coming from global tissue dynamics and geometry is a key outstanding question of systems and stem cell biology. Here, we propose a theory of stem cell dynamics as a stochastic competition for access to a spatially localized niche, giving rise to a stochastic conveyor-belt model. Cell divisions produce a steady cellular stream which advects cells away from the niche, while random rearrangements enable cells away from the niche to be favorably repositioned. Importantly, even when assuming that all cells in a tissue are molecularly equivalent, we predict a common (“universal”) functional dependence of the long-term clonal survival probability on distance from the niche, as well as the emergence of a well-defined number of functional stem cells, dependent only on the rate of random movements vs. mitosis-driven advection. We test the predictions of this theory on datasets of pubertal mammary gland tips and embryonic kidney tips, as well as homeostatic intestinal crypts. Importantly, we find good agreement for the predicted functional dependency of the competition as a function of position, and thus functional stem cell number in each organ. This argues for a key role of positional fluctuations in dictating stem cell number and dynamics, and we discuss the applicability of this theory to other settings. AU - Corominas-Murtra, Bernat AU - Scheele, Colinda L.G.J. AU - Kishi, Kasumi AU - Ellenbroek, Saskia I.J. AU - Simons, Benjamin D. AU - Van Rheenen, Jacco AU - Hannezo, Edouard B ID - 8220 IS - 29 JF - Proceedings of the National Academy of Sciences of the United States of America TI - Stem cell lineage survival as a noisy competition for niche access VL - 117 ER - TY - JOUR AB - Pancreatic islets play an essential role in regulating blood glucose level. Although the molecular pathways underlying islet cell differentiation are beginning to be resolved, the cellular basis of islet morphogenesis and fate allocation remain unclear. By combining unbiased and targeted lineage tracing, we address the events leading to islet formation in the mouse. From the statistical analysis of clones induced at multiple embryonic timepoints, here we show that, during the secondary transition, islet formation involves the aggregation of multiple equipotent endocrine progenitors that transition from a phase of stochastic amplification by cell division into a phase of sublineage restriction and limited islet fission. Together, these results explain quantitatively the heterogeneous size distribution and degree of polyclonality of maturing islets, as well as dispersion of progenitors within and between islets. Further, our results show that, during the secondary transition, α- and β-cells are generated in a contemporary manner. Together, these findings provide insight into the cellular basis of islet development. AU - Sznurkowska, Magdalena K. AU - Hannezo, Edouard B AU - Azzarelli, Roberta AU - Chatzeli, Lemonia AU - Ikeda, Tatsuro AU - Yoshida, Shosei AU - Philpott, Anna AU - Simons, Benjamin D ID - 8669 JF - Nature Communications TI - Tracing the cellular basis of islet specification in mouse pancreas VL - 11 ER - TY - JOUR AB - Cell fate transitions are key to development and homeostasis. It is thus essential to understand the cellular mechanisms controlling fate transitions. Cell division has been implicated in fate decisions in many stem cell types, including neuronal and epithelial progenitors. In other stem cells, such as embryonic stem (ES) cells, the role of division remains unclear. Here, we show that exit from naive pluripotency in mouse ES cells generally occurs after a division. We further show that exit timing is strongly correlated between sister cells, which remain connected by cytoplasmic bridges long after division, and that bridge abscission progressively accelerates as cells exit naive pluripotency. Finally, interfering with abscission impairs naive pluripotency exit, and artificially inducing abscission accelerates it. Altogether, our data indicate that a switch in the division machinery leading to faster abscission regulates pluripotency exit. Our study identifies abscission as a key cellular process coupling cell division to fate transitions. AU - Chaigne, Agathe AU - Labouesse, Céline AU - White, Ian J. AU - Agnew, Meghan AU - Hannezo, Edouard B AU - Chalut, Kevin J. AU - Paluch, Ewa K. ID - 8672 IS - 2 JF - Developmental Cell SN - 15345807 TI - Abscission couples cell division to embryonic stem cell fate VL - 55 ER - TY - JOUR AB - The sebaceous gland (SG) is an essential component of the skin, and SG dysfunction is debilitating1,2. Yet, the cellular bases for its origin, development and subsequent maintenance remain poorly understood. Here, we apply large-scale quantitative fate mapping to define the patterns of cell fate behaviour during SG development and maintenance. We show that the SG develops from a defined number of lineage-restricted progenitors that undergo a programme of independent and stochastic cell fate decisions. Following an expansion phase, equipotent progenitors transition into a phase of homeostatic turnover, which is correlated with changes in the mechanical properties of the stroma and spatial restrictions on gland size. Expression of the oncogene KrasG12D results in a release from these constraints and unbridled gland expansion. Quantitative clonal fate analysis reveals that, during this phase, the primary effect of the Kras oncogene is to drive a constant fate bias with little effect on cell division rates. These findings provide insight into the developmental programme of the SG, as well as the mechanisms that drive tumour progression and gland dysfunction. AU - Andersen, Marianne Stemann AU - Hannezo, Edouard B AU - Ulyanchenko, Svetlana AU - Estrach, Soline AU - Antoku, Yasuko AU - Pisano, Sabrina AU - Boonekamp, Kim E. AU - Sendrup, Sarah AU - Maimets, Martti AU - Pedersen, Marianne Terndrup AU - Johansen, Jens V. AU - Clement, Ditte L. AU - Feral, Chloe C. AU - Simons, Benjamin D. AU - Jensen, Kim B. ID - 7476 IS - 8 JF - Nature Cell Biology SN - 1465-7392 TI - Tracing the cellular dynamics of sebaceous gland development in normal and perturbed states VL - 21 ER - TY - JOUR AB - The formation of self-organized patterns is key to the morphogenesis of multicellular organisms, although a comprehensive theory of biological pattern formation is still lacking. Here, we propose a minimal model combining tissue mechanics with morphogen turnover and transport to explore routes to patterning. Our active description couples morphogen reaction and diffusion, which impact cell differentiation and tissue mechanics, to a two-phase poroelastic rheology, where one tissue phase consists of a poroelastic cell network and the other one of a permeating extracellular fluid, which provides a feedback by actively transporting morphogens. While this model encompasses previous theories approximating tissues to inert monophasic media, such as Turing’s reaction–diffusion model, it overcomes some of their key limitations permitting pattern formation via any two-species biochemical kinetics due to mechanically induced cross-diffusion flows. Moreover, we describe a qualitatively different advection-driven Keller–Segel instability which allows for the formation of patterns with a single morphogen and whose fundamental mode pattern robustly scales with tissue size. We discuss the potential relevance of these findings for tissue morphogenesis. AU - Recho, Pierre AU - Hallou, Adrien AU - Hannezo, Edouard B ID - 6191 IS - 12 JF - Proceedings of the National Academy of Sciences of the United States of America SN - 00278424 TI - Theory of mechanochemical patterning in biphasic biological tissues VL - 116 ER - TY - JOUR AB - Adult intestinal stem cells are located at the bottom of crypts of Lieberkühn, where they express markers such as LGR5 1,2 and fuel the constant replenishment of the intestinal epithelium1. Although fetal LGR5-expressing cells can give rise to adult intestinal stem cells3,4, it remains unclear whether this population in the patterned epithelium represents unique intestinal stem-cell precursors. Here we show, using unbiased quantitative lineage-tracing approaches, biophysical modelling and intestinal transplantation, that all cells of the mouse intestinal epithelium—irrespective of their location and pattern of LGR5 expression in the fetal gut tube—contribute actively to the adult intestinal stem cell pool. Using 3D imaging, we find that during fetal development the villus undergoes gross remodelling and fission. This brings epithelial cells from the non-proliferative villus into the proliferative intervillus region, which enables them to contribute to the adult stem-cell niche. Our results demonstrate that large-scale remodelling of the intestinal wall and cell-fate specification are closely linked. Moreover, these findings provide a direct link between the observed plasticity and cellular reprogramming of differentiating cells in adult tissues following damage5,6,7,8,9, revealing that stem-cell identity is an induced rather than a hardwired property. AU - Guiu, Jordi AU - Hannezo, Edouard B AU - Yui, Shiro AU - Demharter, Samuel AU - Ulyanchenko, Svetlana AU - Maimets, Martti AU - Jørgensen, Anne AU - Perlman, Signe AU - Lundvall, Lene AU - Mamsen, Linn Salto AU - Larsen, Agnete AU - Olesen, Rasmus H. AU - Andersen, Claus Yding AU - Thuesen, Lea Langhoff AU - Hare, Kristine Juul AU - Pers, Tune H. AU - Khodosevich, Konstantin AU - Simons, Benjamin D. AU - Jensen, Kim B. ID - 6513 JF - Nature SN - 00280836 TI - Tracing the origin of adult intestinal stem cells VL - 570 ER - TY - JOUR AB - Branching morphogenesis is a prototypical example of complex three-dimensional organ sculpting, required in multiple developmental settings to maximize the area of exchange surfaces. It requires, in particular, the coordinated growth of different cell types together with complex patterning to lead to robust macroscopic outputs. In recent years, novel multiscale quantitative biology approaches, together with biophysical modelling, have begun to shed new light of this topic. Here, we wish to review some of these recent developments, highlighting the generic design principles that can be abstracted across different branched organs, as well as the implications for the broader fields of stem cell, developmental and systems biology. AU - Hannezo, Edouard B AU - Simons, Benjamin D. ID - 6559 JF - Current Opinion in Cell Biology SN - 09550674 TI - Multiscale dynamics of branching morphogenesis VL - 60 ER - TY - JOUR AB - There is increasing evidence that both mechanical and biochemical signals play important roles in development and disease. The development of complex organisms, in particular, has been proposed to rely on the feedback between mechanical and biochemical patterning events. This feedback occurs at the molecular level via mechanosensation but can also arise as an emergent property of the system at the cellular and tissue level. In recent years, dynamic changes in tissue geometry, flow, rheology, and cell fate specification have emerged as key platforms of mechanochemical feedback loops in multiple processes. Here, we review recent experimental and theoretical advances in understanding how these feedbacks function in development and disease. AU - Hannezo, Edouard B AU - Heisenberg, Carl-Philipp J ID - 6601 IS - 1 JF - Cell SN - 00928674 TI - Mechanochemical feedback loops in development and disease VL - 178 ER - TY - JOUR AB - Steady-state turnover is a hallmark of epithelial tissues throughout adult life. Intestinal epithelial turnover is marked by continuous cell migration, which is assumed to be driven by mitotic pressure from the crypts. However, the balance of forces in renewal remains ill-defined. Combining biophysical modeling and quantitative three-dimensional tissue imaging with genetic and physical manipulations, we revealed the existence of an actin-related protein 2/3 complex–dependent active migratory force, which explains quantitatively the profiles of cell speed, density, and tissue tension along the villi. Cells migrate collectively with minimal rearrangements while displaying dual—apicobasal and front-back—polarity characterized by actin-rich basal protrusions oriented in the direction of migration. We propose that active migration is a critical component of gut epithelial turnover. AU - Krndija, Denis AU - Marjou, Fatima El AU - Guirao, Boris AU - Richon, Sophie AU - Leroy, Olivier AU - Bellaiche, Yohanns AU - Hannezo, Edouard B AU - Vignjevic, Danijela Matic ID - 6832 IS - 6454 JF - Science TI - Active cell migration is critical for steady-state epithelial turnover in the gut VL - 365 ER - TY - JOUR AB - Tissue morphogenesis is driven by mechanical forces that elicit changes in cell size, shape and motion. The extent by which forces deform tissues critically depends on the rheological properties of the recipient tissue. Yet, whether and how dynamic changes in tissue rheology affect tissue morphogenesis and how they are regulated within the developing organism remain unclear. Here, we show that blastoderm spreading at the onset of zebrafish morphogenesis relies on a rapid, pronounced and spatially patterned tissue fluidization. Blastoderm fluidization is temporally controlled by mitotic cell rounding-dependent cell–cell contact disassembly during the last rounds of cell cleavages. Moreover, fluidization is spatially restricted to the central blastoderm by local activation of non-canonical Wnt signalling within the blastoderm margin, increasing cell cohesion and thereby counteracting the effect of mitotic rounding on contact disassembly. Overall, our results identify a fluidity transition mediated by loss of cell cohesion as a critical regulator of embryo morphogenesis. AU - Petridou, Nicoletta AU - Grigolon, Silvia AU - Salbreux, Guillaume AU - Hannezo, Edouard B AU - Heisenberg, Carl-Philipp J ID - 5789 JF - Nature Cell Biology SN - 14657392 TI - Fluidization-mediated tissue spreading by mitotic cell rounding and non-canonical Wnt signalling VL - 21 ER - TY - JOUR AB - Segregation of maternal determinants within the oocyte constitutes the first step in embryo patterning. In zebrafish oocytes, extensive ooplasmic streaming leads to the segregation of ooplasm from yolk granules along the animal-vegetal axis of the oocyte. Here, we show that this process does not rely on cortical actin reorganization, as previously thought, but instead on a cell-cycle-dependent bulk actin polymerization wave traveling from the animal to the vegetal pole of the oocyte. This wave functions in segregation by both pulling ooplasm animally and pushing yolk granules vegetally. Using biophysical experimentation and theory, we show that ooplasm pulling is mediated by bulk actin network flows exerting friction forces on the ooplasm, while yolk granule pushing is achieved by a mechanism closely resembling actin comet formation on yolk granules. Our study defines a novel role of cell-cycle-controlled bulk actin polymerization waves in oocyte polarization via ooplasmic segregation. AU - Shamipour, Shayan AU - Kardos, Roland AU - Xue, Shi-lei AU - Hof, Björn AU - Hannezo, Edouard B AU - Heisenberg, Carl-Philipp J ID - 6508 IS - 6 JF - Cell SN - 00928674 TI - Bulk actin dynamics drive phase segregation in zebrafish oocytes VL - 177 ER - TY - JOUR AB - The actomyosin cytoskeleton, a key stress-producing unit in epithelial cells, oscillates spontaneously in a wide variety of systems. Although much of the signal cascade regulating myosin activity has been characterized, the origin of such oscillatory behavior is still unclear. Here, we show that basal myosin II oscillation in Drosophila ovarian epithelium is not controlled by actomyosin cortical tension, but instead relies on a biochemical oscillator involving ROCK and myosin phosphatase. Key to this oscillation is a diffusive ROCK flow, linking junctional Rho1 to medial actomyosin cortex, and dynamically maintained by a self-activation loop reliant on ROCK kinase activity. In response to the resulting myosin II recruitment, myosin phosphatase is locally enriched and shuts off ROCK and myosin II signals. Coupling Drosophila genetics, live imaging, modeling, and optogenetics, we uncover an intrinsic biochemical oscillator at the core of myosin II regulatory network, shedding light on the spatio-temporal dynamics of force generation. AU - Qin, Xiang AU - Hannezo, Edouard B AU - Mangeat, Thomas AU - Liu, Chang AU - Majumder, Pralay AU - Liu, Jjiaying AU - Choesmel Cadamuro, Valerie AU - Mcdonald, Jocelyn AU - Liu, Yinyao AU - Yi, Bin AU - Wang, Xiaobo ID - 401 IS - 1 JF - Nature Communications TI - A biochemical network controlling basal myosin oscillation VL - 9 ER - TY - JOUR AB - Recent lineage tracing studies have revealed that mammary gland homeostasis relies on unipotent stem cells. However, whether and when lineage restriction occurs during embryonic mammary development, and which signals orchestrate cell fate specification, remain unknown. Using a combination of in vivo clonal analysis with whole mount immunofluorescence and mathematical modelling of clonal dynamics, we found that embryonic multipotent mammary cells become lineage-restricted surprisingly early in development, with evidence for unipotency as early as E12.5 and no statistically discernable bipotency after E15.5. To gain insights into the mechanisms governing the switch from multipotency to unipotency, we used gain-of-function Notch1 mice and demonstrated that Notch activation cell autonomously dictates luminal cell fate specification to both embryonic and basally committed mammary cells. These functional studies have important implications for understanding the signals underlying cell plasticity and serve to clarify how reactivation of embryonic programs in adult cells can lead to cancer. AU - Lilja, Anna AU - Rodilla, Veronica AU - Huyghe, Mathilde AU - Hannezo, Edouard B AU - Landragin, Camille AU - Renaud, Olivier AU - Leroy, Olivier AU - Rulands, Steffen AU - Simons, Benjamin AU - Fré, Silvia ID - 288 IS - 6 JF - Nature Cell Biology TI - Clonal analysis of Notch1-expressing cells reveals the existence of unipotent stem cells that retain long-term plasticity in the embryonic mammary gland VL - 20 ER - TY - JOUR AB - Pancreas development involves a coordinated process in which an early phase of cell segregation is followed by a longer phase of lineage restriction, expansion, and tissue remodeling. By combining clonal tracing and whole-mount reconstruction with proliferation kinetics and single-cell transcriptional profiling, we define the functional basis of pancreas morphogenesis. We show that the large-scale organization of mouse pancreas can be traced to the activity of self-renewing precursors positioned at the termini of growing ducts, which act collectively to drive serial rounds of stochastic ductal bifurcation balanced by termination. During this phase of branching morphogenesis, multipotent precursors become progressively fate-restricted, giving rise to self-renewing acinar-committed precursors that are conveyed with growing ducts, as well as ductal progenitors that expand the trailing ducts and give rise to delaminating endocrine cells. These findings define quantitatively how the functional behavior and lineage progression of precursor pools determine the large-scale patterning of pancreatic sub-compartments. AU - Sznurkowska, Magdalena AU - Hannezo, Edouard B AU - Azzarelli, Roberta AU - Rulands, Steffen AU - Nestorowa, Sonia AU - Hindley, Christopher AU - Nichols, Jennifer AU - Göttgens, Berthold AU - Huch, Meritxell AU - Philpott, Anna AU - Simons, Benjamin ID - 132 IS - 3 JF - Developmental Cell TI - Defining lineage potential and fate behavior of precursors during pancreas development VL - 46 ER - TY - JOUR AB - Branching morphogenesis remains a subject of abiding interest. Although much is known about the gene regulatory programs and signaling pathways that operate at the cellular scale, it has remained unclear how the macroscopic features of branched organs, including their size, network topology and spatial patterning, are encoded. Lately, it has been proposed that, these features can be explained quantitatively in several organs within a single unifying framework. Based on large- scale organ recon - structions and cell lineage tracing, it has been argued that morphogenesis follows from the collective dynamics of sublineage- restricted self- renewing progenitor cells, localized at ductal tips, that act cooperatively to drive a serial process of ductal elon - gation and stochastic tip bifurcation. By correlating differentiation or cell cycle exit with proximity to maturing ducts, this dynamic results in the specification of a com- plex network of defined density and statistical organization. These results suggest that, for several mammalian tissues, branched epithelial structures develop as a self- organized process, reliant upon a strikingly simple, but generic, set of local rules, without recourse to a rigid and deterministic sequence of genetically programmed events. Here, we review the basis of these findings and discuss their implications. AU - Hannezo, Edouard B AU - Simons, Benjamin D. ID - 5787 IS - 9 JF - Development Growth and Differentiation SN - 00121592 TI - Statistical theory of branching morphogenesis VL - 60 ER - TY - JOUR AB - Cell shape is determined by a balance of intrinsic properties of the cell as well as its mechanochemical environment. Inhomogeneous shape changes underlie many morphogenetic events and involve spatial gradients in active cellular forces induced by complex chemical signaling. Here, we introduce a mechanochemical model based on the notion that cell shape changes may be induced by external diffusible biomolecules that influence cellular contractility (or equivalently, adhesions) in a concentration-dependent manner—and whose spatial profile in turn is affected by cell shape. We map out theoretically the possible interplay between chemical concentration and cellular structure. Besides providing a direct route to spatial gradients in cell shape profiles in tissues, we show that the dependence on cell shape helps create robust mechanochemical gradients. AU - Dasbiswas, Kinjal AU - Hannezo, Claude-Edouard B AU - Gov, Nir ID - 421 IS - 4 JF - Biophysical Journal TI - Theory of eppithelial cell shape transitions induced by mechanoactive chemical gradients VL - 114 ER - TY - JOUR AB - During puberty, the mouse mammary gland develops into a highly branched epithelial network. Owing to the absence of exclusive stem cell markers, the location, multiplicity, dynamics and fate of mammary stem cells (MaSCs), which drive branching morphogenesis, are unknown. Here we show that morphogenesis is driven by proliferative terminal end buds that terminate or bifurcate with near equal probability, in a stochastic and time-invariant manner, leading to a heterogeneous epithelial network. We show that the majority of terminal end bud cells function as highly proliferative, lineage-committed MaSCs that are heterogeneous in their expression profile and short-term contribution to ductal extension. Yet, through cell rearrangements during terminal end bud bifurcation, each MaSC is able to contribute actively to long-term growth. Our study shows that the behaviour of MaSCs is not directly linked to a single expression profile. Instead, morphogenesis relies upon lineage-restricted heterogeneous MaSC populations that function as single equipotent pools in the long term. AU - Scheele, Colinda AU - Hannezo, Edouard B AU - Muraro, Mauro AU - Zomer, Anoek AU - Langedijk, Nathalia AU - Van Oudenaarden, Alexander AU - Simons, Benjamin AU - Van Rheenen, Jacco ID - 934 IS - 7641 JF - Nature SN - 00280836 TI - Identity and dynamics of mammary stem cells during branching morphogenesis VL - 542 ER - TY - JOUR AB - Homeostatic replacement of epithelial cells from basal precursors is a multistep process involving progenitor cell specification, radial intercalation and, finally, apical surface emergence. Recent data demonstrate that actin-based pushing under the control of the formin protein Fmn1 drives apical emergence in nascent multiciliated epithelial cells (MCCs), but little else is known about this actin network or the control of Fmn1. Here, we explore the role of the small GTPase RhoA in MCC apical emergence. Disruption of RhoA function reduced the rate of apical surface expansion and decreased the final size of the apical domain. Analysis of cell shapes suggests that RhoA alters the balance of forces exerted on the MCC apical surface. Finally, quantitative time-lapse imaging and fluorescence recovery after photobleaching studies argue that RhoA works in concert with Fmn1 to control assembly of the specialized apical actin network in MCCs. These data provide new molecular insights into epithelial apical surface assembly and could also shed light on mechanisms of apical lumen formation AU - Sedzinski, Jakub AU - Hannezo, Edouard B AU - Tu, Fan AU - Biro, Maté AU - Wallingford, John ID - 936 IS - 5 JF - Journal of Cell Science TI - RhoA regulates actin network dynamics during apical surface emergence in multiciliated epithelial cells VL - 130 ER - TY - JOUR AB - During epithelial cytokinesis, the remodelling of adhesive cell-cell contacts between the dividing cell and its neighbours has profound implications for the integrity, arrangement and morphogenesis of proliferative tissues. In both vertebrates and invertebrates, this remodelling requires the activity of non-muscle myosin II (MyoII) in the interphasic cells neighbouring the dividing cell. However, the mechanisms that coordinate cytokinesis and MyoII activity in the neighbours are unknown. Here we show that in the Drosophila notum epithelium, each cell division is associated with a mechanosensing and transmission event that controls MyoII dynamics in neighbouring cells. We find that the ring pulling forces promote local junction elongation, which results in local E-cadherin dilution at the ingressing adherens junction. In turn, the reduction in E-cadherin concentration and the contractility of the neighbouring cells promote self-organized actomyosin flows, ultimately leading to accumulation of MyoII at the base of the ingressing junction. Although force transduction has been extensively studied in the context of adherens junction reinforcement to stabilize adhesive cell-cell contacts, we propose an alternative mechanosensing mechanism that coordinates actomyosin dynamics between epithelial cells and sustains the remodelling of the adherens junction in response to mechanical forces. AU - Pinheiro, Diana AU - Hannezo, Edouard B AU - Herszterg, Sophie AU - Bosveld, Floris AU - Gaugué, Isabelle AU - Balakireva, Maria AU - Wang, Zhimin AU - Cristo, Inês AU - Rigaud, Stéphane AU - Markova, Olga AU - Bellaïche, Yohanns ID - 937 IS - 7652 JF - Nature SN - 00280836 TI - Transmission of cytokinesis forces via E cadherin dilution and actomyosin flows VL - 545 ER - TY - JOUR AB - The morphogenesis of branched organs remains a subject of abiding interest. Although much is known about the underlying signaling pathways, it remains unclear how macroscopic features of branched organs, including their size, network topology, and spatial patterning, are encoded. Here, we show that, in mouse mammary gland, kidney, and human prostate, these features can be explained quantitatively within a single unifying framework of branching and annihilating random walks. Based on quantitative analyses of large-scale organ reconstructions and proliferation kinetics measurements, we propose that morphogenesis follows from the proliferative activity of equipotent tips that stochastically branch and randomly explore their environment but compete neutrally for space, becoming proliferatively inactive when in proximity with neighboring ducts. These results show that complex branched epithelial structures develop as a self-organized process, reliant upon a strikingly simple but generic rule, without recourse to a rigid and deterministic sequence of genetically programmed events. AU - Hannezo, Edouard B AU - Scheele, Colinda AU - Moad, Mohammad AU - Drogo, Nicholas AU - Heer, Rakesh AU - Sampogna, Rosemary AU - Van Rheenen, Jacco AU - Simons, Benjamin ID - 726 IS - 1 JF - Cell SN - 00928674 TI - A unifying theory of branching morphogenesis VL - 171 ER - TY - JOUR AB - The changes in cell dynamics after oncogenic mutation that lead to the development of tumours are currently unknown. Here, using skin epidermis as a model, we assessed the effect of oncogenic hedgehog signalling in distinct cell populations and their capacity to induce basal cell carcinoma, the most frequent cancer in humans. We found that only stem cells, and not progenitors, initiated tumour formation upon oncogenic hedgehog signalling. This difference was due to the hierarchical organization of tumour growth in oncogene-targeted stem cells, characterized by an increase in symmetric self-renewing divisions and a higher p53-dependent resistance to apoptosis, leading to rapid clonal expansion and progression into invasive tumours. Our work reveals that the capacity of oncogene-targeted cells to induce tumour formation is dependent not only on their long-term survival and expansion, but also on the specific clonal dynamics of the cancer cell of origin. AU - Sánchez Danés, Adriana AU - Hannezo, Edouard B AU - Larsimont, Jean AU - Liagre, Mélanie AU - Youssef, Khalil AU - Simons, Benjamin AU - Blanpain, Cédric ID - 930 IS - 7616 JF - Nature TI - Defining the clonal dynamics leading to mouse skin tumour initiation VL - 536 ER - TY - JOUR AB - In many adult tissues, stem cells and differentiated cells are not homogeneously distributed: stem cells are arranged in periodic "niches," and differentiated cells are constantly produced and migrate out of these niches. In this article, we provide a general theoretical framework to study mixtures of dividing and actively migrating particles, which we apply to biological tissues. We show in particular that the interplay between the stresses arising from active cell migration and stem cell division give rise to robust stem cell patterns. The instability of the tissue leads to spatial patterns which are either steady or oscillating in time. The wavelength of the instability has an order of magnitude consistent with the biological observations. We also discuss the implications of these results for future in vitro and in vivo experiments. AU - Hannezo, Edouard B AU - Coucke, Alice AU - Joanny, Jean ID - 931 IS - 2 JF - Physical Review E Statistical Nonlinear and Soft Matter Physics TI - Interplay of migratory and division forces as a generic mechanism for stem cell patterns VL - 93 ER - TY - JOUR AB - Epithelial sheets are crucial components of all metazoan animals, enclosing organs and protecting the animal from its environment. Epithelial homeostasis poses unique challenges, as addition of new cells and loss of old cells must be achieved without disrupting the fluid-tight barrier and apicobasal polarity of the epithelium. Several studies have identified cell biological mechanisms underlying extrusion of cells from epithelia, but far less is known of the converse mechanism by which new cells are added. Here, we combine molecular, pharmacological, and laser-dissection experiments with theoretical modeling to characterize forces driving emergence of an apical surface as single nascent cells are added to a vertebrate epithelium in vivo. We find that this process involves the interplay between cell-autonomous actin-generated pushing forces in the emerging cell and mechanical properties of neighboring cells. Our findings define the forces driving this cell behavior, contributing to a more comprehensive understanding of epithelial homeostasis. AU - Sedzinski, Jakub AU - Hannezo, Edouard B AU - Tu, Fan AU - Biro, Maté AU - Wallingford, John ID - 932 IS - 1 JF - Developmental Cell TI - Emergence of an Apical Epithelial Cell Surface In Vivo VL - 36 ER - TY - JOUR AB - The actomyosin cytoskeleton is a primary force-generating mechanism in morphogenesis, thus a robust spatial control of cytoskeletal positioning is essential. In this report, we demonstrate that actomyosin contractility and planar cell polarity (PCP) interact in post-mitotic Ciona notochord cells to self-assemble and reposition actomyosin rings, which play an essential role for cell elongation. Intriguingly, rings always form at the cells′ anterior edge before migrating towards the center as contractility increases, reflecting a novel dynamical property of the cortex. Our drug and genetic manipulations uncover a tug-of-war between contractility, which localizes cortical flows toward the equator and PCP, which tries to reposition them. We develop a simple model of the physical forces underlying this tug-of-war, which quantitatively reproduces our results. We thus propose a quantitative framework for dissecting the relative contribution of contractility and PCP to the self-assembly and repositioning of cytoskeletal structures, which should be applicable to other morphogenetic events. AU - Sehring, Ivonne AU - Recho, Pierre AU - Denker, Elsa AU - Kourakis, Matthew AU - Mathiesen, Birthe AU - Hannezo, Edouard B AU - Dong, Bo AU - Jiang, Di ID - 928 JF - eLife TI - Assembly and positioning of actomyosin rings by contractility and planar cell polarity VL - 4 ER - TY - JOUR AB - This paper presents a numerical study of a Capillary Pumped Loop evaporator. A two-dimensional unsteady mathematical model of a flat evaporator is developed to simulate heat and mass transfer in unsaturated porous wick with phase change. The liquid-vapor phase change inside the porous wick is described by Langmuir's law. The governing equations are solved by the Finite Element Method. The results are presented then for a sintered nickel wick and methanol as a working fluid. The heat flux required to the transition from the all-liquid wick to the vapor-liquid wick is calculated. The dynamic and thermodynamic behavior of the working fluid in the capillary structure are discussed in this paper. AU - Boubaker, Riadh AU - Platel, Vincent AU - Bergès, Alexis AU - Bancelin, Mathieu AU - Hannezo, Edouard B ID - 924 JF - Applied Thermal Engineering TI - Dynamic model of heat and mass transfer in an unsaturated porous wick of capillary pumped loop VL - 76 ER - TY - JOUR AB - An essential question of morphogenesis is how patterns arise without preexisting positional information, as inspired by Turing. In the past few years, cytoskeletal flows in the cell cortex have been identified as a key mechanism of molecular patterning at the subcellular level. Theoretical and in vitro studies have suggested that biological polymers such as actomyosin gels have the property to self-organize, but the applicability of this concept in an in vivo setting remains unclear. Here, we report that the regular spacing pattern of supracellular actin rings in the Drosophila tracheal tubule is governed by a self-organizing principle. We propose a simple biophysical model where pattern formation arises from the interplay of myosin contractility and actin turnover. We validate the hypotheses of the model using photobleaching experiments and report that the formation of actin rings is contractility dependent. Moreover, genetic and pharmacological perturbations of the physical properties of the actomyosin gel modify the spacing of the pattern, as the model predicted. In addition, our model posited a role of cortical friction in stabilizing the spacing pattern of actin rings. Consistently, genetic depletion of apical extracellular matrix caused strikingly dynamic movements of actin rings, mirroring our model prediction of a transition from steady to chaotic actin patterns at low cortical friction. Our results therefore demonstrate quantitatively that a hydrodynamical instability of the actin cortex can trigger regular pattern formation and drive morphogenesis in an in vivo setting. AU - Hannezo, Edouard B AU - Dong, Bo AU - Recho, Pierre AU - Joanny, Jean AU - Hayashi, Shigeo ID - 929 IS - 28 JF - PNAS TI - Cortical instability drives periodic supracellular actin pattern formation in epithelial tubes VL - 112 ER - TY - JOUR AB - Although collective cell motion plays an important role, for example during wound healing, embryogenesis, or cancer progression, the fundamental rules governing this motion are still not well understood, in particular at high cell density. We study here the motion of human bronchial epithelial cells within a monolayer, over long times. We observe that, as the monolayer ages, the cells slow down monotonously, while the velocity correlation length first increases as the cells slow down but eventually decreases at the slowest motions. By comparing experiments, analytic model, and detailed particle-based simulations, we shed light on this biological amorphous solidification process, demonstrating that the observed dynamics can be explained as a consequence of the combined maturation and strengthening of cell-cell and cell-substrate adhesions. Surprisingly, the increase of cell surface density due to proliferation is only secondary in this process. This analysis is confirmed with two other cell types. The very general relations between the mean cell velocity and velocity correlation lengths, which apply for aggregates of self-propelled particles, as well as motile cells, can possibly be used to discriminate between various parameter changes in vivo, from noninvasive microscopy data. AU - García, Simón AU - Hannezo, Edouard B AU - Elgeti, Jens AU - Joanny, Jean AU - Silberzan, Pascal AU - Gov, Nir ID - 933 IS - 50 JF - PNAS TI - Physics of active jamming during collective cellular motion in a monolayer VL - 112 ER - TY - JOUR AB - The morphological stability of biological tubes is crucial for the efficient circulation of fluids and gases. Failure of this stability causes irregularly shaped tubes found in multiple pathological conditions. Here, we report that Drosophila mutants of the ESCRT III component Shrub/Vps32 exhibit a strikingly elongated sinusoidal tube phenotype. This is caused by excessive apical membrane synthesis accompanied by the ectopic accumulation and overactivation of Crumbs in swollen endosomes. Furthermore, we demonstrate that the apical extracellular matrix (aECM) of the tracheal tube is a viscoelastic material coupled with the apical membrane. We present a simple mechanical model in which aECM elasticity, apical membrane growth, and their interaction are three vital parameters determining the stability of biological tubes. Our findings demonstrate a mechanical role for the extracellular matrix and suggest that the interaction of the apical membrane and an elastic aECM determines the final morphology of biological tubes independent of cell shape. AU - Dong, Bo AU - Hannezo, Edouard B AU - Hayashi, Shigeo ID - 925 IS - 4 JF - Cell Reports TI - Balance between apical membrane growth and luminal matrix resistance determines epithelial tubule shape VL - 7 ER - TY - JOUR AB - Morphogenesis during embryo development requires the coordination of mechanical forces to generate the macroscopic shapes of organs. We propose a minimal theoretical model, based on cell adhesion and actomyosin contractility, which describes the various shapes of epithelial cells and the bending and buckling of epithelial sheets, as well as the relative stability of cellular tubes and spheres. We show that, to understand these processes, a full 3D description of the cells is needed, but that simple scaling laws can still be derived. The morphologies observed in vivo can be understood as stable points of mechanical equations and the transitions between them are either continuous or discontinuous. We then focus on epithelial sheet bending, a ubiquitous morphogenetic process. We calculate the curvature of an epithelium as a function of actin belt tension as well as of cell-cell and and cell-substrate tension. The model allows for a comparison of the relative stabilities of spherical or cylindrical cellular structures (acini or tubes). Finally, we propose a unique type of buckling instability of epithelia, driven by a flattening of individual cell shapes, and discuss experimental tests to verify our predictions. AU - Hannezo, Edouard B AU - Prost, Jacques AU - Joanny, Jean ID - 927 IS - 1 JF - PNAS TI - Theory of epithelial sheet morphology in three dimensions VL - 111 ER - TY - JOUR AB - The regulation of cell growth in animal tissues is a question of critical importance: most tissues contain different types of cells in interconversion and the fraction of each type has to be controlled in a precise way, by mechanisms that remain unclear. Here, we provide a theoretical framework for the homeostasis of stem-cell-containing epithelial tissues using mechanical equations, which describe the size of the tissue and kinetic equations, which describe the interconversions of the cell populations. We show that several features, such as the evolution of stem cell fractions during intestinal development, the shape of a developing intestinal wall, as well as the increase in the proliferative compartment in cancer initiation, can be studied and understood from generic modelling which does not rely on a particular regulatory mechanism. Finally, inspired by recent experiments, we propose a model where cell division rates are regulated by the mechanical stresses in the epithelial sheet. We show that pressure-controlled growth can, in addition to the previous features, also explain with few parameters the formation of stem cell compartments as well as the morphologies observed when a colonic crypt becomes cancerous. We also discuss optimal strategies of wound healing, in connection with experiments on the cornea. AU - Hannezo, Edouard B AU - Prost, Jacques AU - Joanny, Jean ID - 926 IS - 93 JF - Journal of the Royal Society Interface TI - Growth homeostatic regulation and stem cell dynamics in tissues VL - 11 ER - TY - JOUR AB - Recent experiments have shown that spreading epithelial sheets exhibit a long-range coordination of motility forces that leads to a buildup of tension in the tissue, which may enhance cell division and the speed of wound healing. Furthermore, the edges of these epithelial sheets commonly show finger-like protrusions whereas the bulk often displays spontaneous swirls of motile cells. To explain these experimental observations, we propose a simple flocking-type mechanism, in which cells tend to align their motility forceswith their velocity. Implementing this idea in amechanical tissue simulation, the proposed model gives rise to efficient spreading and can explain the experimentally observed long-range alignment of motility forces in highly disordered patterns, as well as the buildup of tensile stress throughout the tissue. Our model also qualitatively reproduces the dependence of swirl size and swirl velocity on cell density reported in experiments and exhibits an undulation instability at the edge of the spreading tissue commonly observed in vivo. Finally, we study the dependence of colony spreading speed on important physical and biological parameters and derive simple scaling relations that show that coordination of motility forces leads to an improvement of the wound healing process for realistic tissue parameters. AU - Basan, Markus AU - Elgeti, Jens AU - Hannezo, Edouard B AU - Rappel, Wouter AU - Levine, Herbert ID - 921 IS - 7 JF - PNAS TI - Alignment of cellular motility forces with tissue flow as a mechanism for efficient wound healing VL - 110 ER - TY - JOUR AB - We study theoretically the morphologies of biological tubes affected by various pathologies. When epithelial cells grow, the negative tension produced by their division provokes a buckling instability. Several shapes are investigated: varicose, dilated, sinuous, or sausagelike. They are all found in pathologies of tracheal, renal tubes, or arteries. The final shape depends crucially on the mechanical parameters of the tissues: Young's modulus, wall-to-lumen ratio, homeostatic pressure. We argue that since tissues must be in quasistatic mechanical equilibrium, abnormal shapes convey information as to what causes the pathology. We calculate a phase diagram of tubular instabilities which could be a helpful guide for investigating the underlying genetic regulation. AU - Hannezo, Edouard B AU - Prost, Jacques AU - Joanny, Jean ID - 922 IS - 1 JF - Physical Review Letters TI - Mechanical instabilities of biological tubes VL - 109 ER - TY - JOUR AB - The conserved role of Notch signaling in controlling intestinal cell fate specification and homeostasis has been extensively studied. Nevertheless, the precise identity of the cells in which Notch signaling is active and the role of different Notch receptor paralogues in the intestine remain ambiguous, due to the lack of reliable tools to investigate Notch expression and function in vivo. We generated a new series of transgenic mice that allowed us, by lineage analysis, to formally prove that Notch1 and Notch2 are specifically expressed in crypt stem cells. In addition, a novel Notch reporter mouse, Hes1-EmGFP SAT, demonstrated exclusive Notch activity in crypt stem cells and absorptive progenitors. This roster of knock-in and reporter mice represents a valuable resource to functionally explore the Notch pathway in vivo in virtually all tissues. AU - Fré, Silvia AU - Hannezo, Edouard B AU - Šale, Sanja AU - Huyghe, Mathilde AU - Lafkas, Daniel AU - Kissel, Holger AU - Louvi, Angeliki AU - Greve, Jeffrey AU - Louvard, Daniel AU - Artavanis Tsakonas, Spyros ID - 923 IS - 10 JF - PLoS One TI - Notch lineages and activity in intestinal stem cells determined by a new set of knock in mice VL - 6 ER - TY - JOUR AB - Collective cell migration in tissues occurs throughout embryonic development, during wound healing, and in cancerous tumor invasion, yet most detailed knowledge of cell migration comes from single-cell studies. As single cells migrate, the shape of the cell body fluctuates dramatically through cyclic processes of extension, adhesion, and retraction, accompanied by erratic changes in migration direction. Within confluent cell layers, such subcellular motions must be coupled between neighbors, yet the influence of these subcellular motions on collective migration is not known. Here we study motion within a confluent epithelial cell sheet, simultaneously measuring collective migration and subcellular motions, covering a broad range of length scales, time scales, and cell densities. At large length scales and time scales collective migration slows as cell density rises, yet the fastest cells move in large, multicell groups whose scale grows with increasing cell density. This behavior has an intriguing analogy to dynamic heterogeneities found in particulate systems as they become more crowded and approach a glass transition. In addition we find a diminishing self-diffusivity of short-wavelength motions within the cell layer, and growing peaks in the vibrational density of states associated with cooperative cell-shape fluctuations. Both of these observations are also intriguingly reminiscent of a glass transition. Thus, these results provide a broad and suggestive analogy between cell motion within a confluent layer and the dynamics of supercooled colloidal and molecular fluids approaching a glass transition. AU - Angelini, Thomas AU - Hannezo, Edouard B AU - Trepatc, Xavier AU - Marquez, Manuel AU - Fredberg, Jeffrey AU - Weitz, David ID - 919 IS - 12 JF - Proceedings of the National Academy of Sciences of the United States of America TI - Glass-like dynamics of collective cell migration VL - 108 ER - TY - JOUR AB - We study theoretically the shapes of a dividing epithelial monolayer of cells lying on top of an elastic stroma. The negative tension created by cell division provokes a buckling instability at a finite wave vector leading to the formation of periodic arrays of villi and crypts. The instability is similar to the buckling of a metallic plate under compression. We use the results to rationalize the various structures of the intestinal lining observed in vivo. Taking into account the coupling between cell division and local curvature, we obtain different patterns of villi and crypts, which could explain the different morphologies of the small intestine and the colon. AU - Hannezo, Edouard B AU - Prost, Jacques AU - Joanny, Jean ID - 918 IS - 7 JF - Physical Review Letters TI - Instabilities of monolayered epithelia Shape and structure of villi and crypts VL - 107 ER - TY - JOUR AB - Most eukaryotic cells sense and respond to the mechanical properties of their surroundings. This can strongly influence their collective behavior in embryonic development, tissue function, and wound healing. We use a deformable substrate to measure collective behavior in cell motion due to substrate mediated cell-cell interactions. We quantify spatial and temporal correlations in migration velocity and substrate deformation, and show that cooperative cell-driven patterns of substrate deformation mediate long-distance mechanical coupling between cells and control collective cell migration. AU - Angelini, Thomas AU - Hannezo, Edouard B AU - Trepat, Xavier AU - Fredberg, Jeffrey AU - Weitz, David ID - 920 IS - 16 JF - Physical Review Letters TI - Cell migration driven by cooperative substrate deformation patterns VL - 104 ER -