Publications

Colorectal cancer (CRC) tumors are composed of heterogeneous and plastic cell populations, including a pool of cancer stem cells that express LGR5. Whether these distinct cell populations display different mechanical properties, and how these properties might contribute to metastasis is poorly understood. Using CRC patient derived organoids (PDOs), we find that compared to LGR5- cells, LGR5+ cancer stem cells are stiffer, adhere better to the extracellular matrix (ECM), move slower both as single cells and clusters, display higher nuclear YAP, show a higher survival rate in response to mechanical confinement, and form larger transendothelial gaps. These differences are largely explained by the downregulation of the membrane to cortex attachment proteins Ezrin/Radixin/Moesin (ERMs) in the LGR5+ cells. By analyzing single cell RNA-sequencing (scRNA-seq) expression patterns from a patient cohort, we show that this downregulation is a robust signature of colorectal tumors. Our results show that LGR5- cells display a mechanically dynamic phenotype suitable for dissemination from the primary tumor whereas LGR5+ cells display a mechanically stable and resilient phenotype suitable for extravasation and metastatic growth. The mechanical properties of heterogeneous cell populations in colorectal tumors and the relevance to cancer metastasis remain not fully understood. Here, the authors suggest that the variations in malignant phenotypes between LGR5-positive cancer stem cells and LGR5-negative cells could be due to their distinct mechanical phenotypes observed in vitro, determined by the membrane to cortex attachment proteins Ezrin/Radixin/Moesin.

JTD Keywords: , , Adhesion, Deformability, E-cadherin, Erm proteins, Expression, Metastasis, Organization, Plasticit, Stem-cells, Tumor-cells

Adherens junctions (AJs) allow cell contact to inhibit epithelial migration yet also permit epithelia to move as coherent sheets. How, then, do cells identify which contacts will inhibit locomotion? Here, we show that in human epithelial cells this arises from the orientation of cortical flows at AJs. When the leader cells from different migrating sheets make head-on contact with one another, they assemble AJs that couple together oppositely directed cortical flows. This applies a tensile signal to the actin-binding domain (ABD) of a-cate-nin, which provides a clutch to promote lateral adhesion growth and inhibit the lamellipodial activity neces-sary for migration. In contrast, AJs found between leader cells in the same migrating sheet have cortical flows aligned in the same direction, and no such mechanical inhibition takes place. Therefore, a-catenin mechano-sensitivity in the clutch between E-cadherin and cortical F-actin allows cells to interpret the direction of motion via cortical flows and signal for contact to inhibit locomotion.

JTD Keywords: Clutch, Contact inhibition of locomotion, Cortical flow, E-cadherin adhesion, Mechanical tension, Α-catenin

The function of organs such as lungs, kidneys and mammary glands relies on the three-dimensional geometry of their epithelium. To adopt shapes such as spheres, tubes and ellipsoids, epithelia generate mechanical stresses that are generally unknown. Here we engineer curved epithelial monolayers of controlled size and shape and map their state of stress. We design pressurized epithelia with circular, rectangular and ellipsoidal footprints. We develop a computational method, called curved monolayer stress microscopy, to map the stress tensor in these epithelia. This method establishes a correspondence between epithelial shape and mechanical stress without assumptions of material properties. In epithelia with spherical geometry we show that stress weakly increases with areal strain in a size-independent manner. In epithelia with rectangular and ellipsoidal cross-section we find pronounced stress anisotropies that impact cell alignment. Our approach enables a systematic study of how geometry and stress influence epithelial fate and function in three-dimensions.© 2023. The Author(s).

JTD Keywords: cell, forces, morphogenesis, tension, E-cadherin, Epithelial cells, Epithelium, Microscopy, Stress, mechanical

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

JTD Keywords: Adhesion, Dynamics, E-cadherin, Gradient, Migration, Model, Motility, Movements, Rigidity, Substrate stiffness

Several factors present in the extracellular environment regulate epithelial cell adhesion and dynamics. Among them, growth factors such as EGF, upon binding to their receptors at the cell surface, get internalized and directly activate the acto-myosin machinery. In this study we present the effects of EGF on the contractility of epithelial cancer cell colonies in confined geometry of different sizes. We show that the extent to which EGF triggers contractility scales with the cluster size and thus the number of cells. Moreover, the collective contractility results in a radial distribution of traction forces, which are dependent on integrin β1 peripheral adhesions and transmitted to neighboring cells through adherens junctions. Taken together, EGF-induced contractility acts on the mechanical crosstalk and linkage between the cell-cell and cell-matrix compartments, regulating collective responses.Copyright © 2022 The Authors. Published by Elsevier GmbH.. All rights reserved.

JTD Keywords: actin, activation, actomyosin, adherens junctions, adhesion, e-cadherin, egf, maturation, mechanical regulation, micropatterning, migration, traction forces, transduction, transmission, Actomyosin, Adherens junctions, Cell adhesion, Cell membrane, Collective contractility, Egf, Epidermal growth factor, Epidermal-growth-factor, Epithelial cells, Micropatterning, Myosins, Traction forces

Epithelial cell divisions are coordinated with cell loss to preserve epithelial integrity. However, how epithelia adapt their rate of cell division to changes in cell number, for instance during homeostatic turnover or wounding, is not well understood. Here, we show that epithelial cells sense local cell density through mechanosensitive E-cadherin adhesions to control G2/M cell-cycle progression. As local cell density increases, tensile forces on E-cadherin adhesions are reduced, which prompts the accumulation of the G2 checkpoint kinase Wee1 and downstream inhibitory phosphorylation of Cdk1. Consequently, dense epithelia contain a pool of cells that are temporarily halted in G2 phase. These cells are readily triggered to divide following epithelial wounding due to the consequent increase in intercellular forces and resulting degradation of Wee1. Our data collectively show that epithelial cell division is controlled by a mechanical G2 checkpoint, which is regulated by cell-density-dependent intercellular forces sensed and transduced by E-cadherin adhesions.Copyright © 2022 The Author(s). Published by Elsevier Inc. All rights reserved.

JTD Keywords: Adherens junction, Cadherins, Cell cycle, Cell cycle proteins, Cell division, Cp: cell biology, E-cadherin, Epithelial cells, Epithelial homeostasis, G2 checkpoint, G2 phase cell cycle checkpoints, Mechanical forces, Mechanotransduction, Mitosis, Phosphorylation, Proliferation

[Figure: see text].

JTD Keywords: activation, cell extrusion, contraction, drives, homeostasis, interface, junctions, kinase, tension, Adhesion, Article, Cell membranes, Chemical activation, Cytology, E-cadherin, Epithelial monolayers, Epithelium, Homoeostasis, Human, Mechanical instabilities, Monolayers, Morphological transformations, Morphology, Normal tissue, Oncogenics, Soft substrates, Substrates, Tissue, Tissue mechanics, Tissue morphology, Tumor development