Biology subjects

Kurzawa, L.

Publications and source records attributed to Kurzawa, L..

5 recordsLinked to original sources

bioRxiv2024

Contractile forces direct the chiral swirling of minimal cell collectives

Chirality is a conserved biological feature with critical implications in tissue morphogenesis and embryonic development. In culture, large multicellular groups exhibit spontaneous chiral symmetry break when moving collectively on micropatterned surfaces. Although several studies have shown that actin network integrity and acto-myosin network contractility participate to the establishment of the chirality of the movement, the exact contribution of contractile forces to the directionality of the chiral bias in collectives remains to be elucidated. Here we studied the contractile forces produced by a minimal collective constituted of a pair of endothelial cells. We first show that cell doublets confined on disk-shaped micropatterns undergo spontaneous and persistent chiral swirling, displaying a mild but robust clockwise (CW) bias, as the one observed in bigger collectives. This bias could be amplified or reversed by modulating contractile forces. Traction force measurements revealed that large forces tend to drive counter-clockwise (CCW) rotation whereas low forces rather favor a CW rotation. Furthermore, the study of heterotypic doublets indicates that the speed and direction of the rotation is determined by the more contractile cells within the doublets. These results thus revealed that contractile leader cells could drive the chiral motion of minimal collectives. Significance StatementChirality, which represents a fundamental property of living systems, manifests in cell collectives by their persistent biased directional swirling. Despite the clear identification of the implication of actomyosin cytoskeleton in driving the internal chiral symmetry break occurring in cells, little is known about the actual role of cellular forces produced by this network in the development of handedness in collectives. Our findings establish that the level of mechanical energy developed by pairs of confined endothelial cells regulates the strength and direction of their rotation. Our results also identify the more contractile cell of the doublet as the cell driving the direction and speed of rotation of the pair. This study thus sheds new light on the importance of the generation and integration of mechanical forces within a small collective in the determination of its chiral rotation.

cell biology↗

bioRxiv2020

Stress fibers are embedded in a contractile cortical network.

Contractile actomyosin networks generate intracellular forces essential for the regulation of cell shape, migration, and cell-fate decisions, ultimately leading to the remodeling and patterning of tissues. Although actin filaments aligned in bundles represent the main source of traction-force production in adherent cells, there is increasing evidence that these bundles form interconnected and interconvertible structures with the rest of the intracellular actin network. In this study, we explored how these bundles are connected to the surrounding cortical network and the mechanical impact of these interconnected structures on the production and distribution of traction forces on the extracellular matrix and throughout the cell. By using a combination of hydrogel micropatterning, traction-force microscopy and laser photoablation, we measured the relaxation of the cellular traction field in response to local photoablations at various positions within the cell. Our experimental results and modeling of the mechanical response of the network revealed that bundles were fully embedded along their entire length in a continuous and contractile network of cortical filaments. Moreover, the propagation of the contraction of these bundles throughout the entire cell was dependent on this embedding. In addition, these bundles appeared to originate from the alignment and coalescence of thin and unattached cortical actin filaments from the surrounding mesh.

cell biology↗

bioRxiv2020

Loss of Ena/VASP interferes with lamellipodium architecture, motility and integrin-dependent adhesion

Cell migration entails networks and bundles of actin filaments termed lamellipodia and microspikes or filopodia, respectively, as well as focal adhesions, all of which recruit Ena/VASP family members hitherto thought to antagonize efficient cell motility. However, we find these proteins to act as positive regulators of migration in different cell lines. CRISPR/Cas9-mediated loss of Ena/VASP proteins reduced lamellipodial actin assembly and perturbed lamellipodial architecture, as evidenced by changed network geometry as well as reduction of filament length and number that was accompanied by abnormal Arp2/3 complex and heterodimeric capping protein accumulation. Loss of Ena/VASP function also abolished the formation of microspikes normally embedded in lamellipodia, but not of filopodia capable of emanating without lamellipodia. Ena/VASP-deficiency also impaired integrin-mediated adhesion accompanied by reduced traction forces exerted through these structures. Our data thus uncover novel, cellular Ena/VASP functions of these actin polymerases that are fully consistent with their promotion of cell migration.

cell biology↗

bioRxiv2019

Biophysical properties of intermediate states of EMT outperform both epithelial and mesenchymal states.

Potential metastatic cells can dissociate from a primary breast tumor by undergoing an epithelial-to-mesenchymal transmission (EMT). Recent work has revealed that cells in intermediate states of EMT acquire an augmented capacity for tumor-cell dissemination. These states have been characterized by molecular markers, but the structural features and the cellular mechanisms that underlie the acquisition of their invasive properties are still unknown. Using human mammary epithelial cells, we generated cells in intermediate states of EMT through the induction of a single EMT-inducing transcription factor, ZEB1, and cells in a mesenchymal state by stimulation with TGF{beta}. In stereotypic and spatially-defined culture conditions, the architecture, internal organization and mechanical properties of cells in the epithelial, intermediate and mesenchymal state were measured and compared. We found that the lack of intercellular cohesiveness in epithelial and mesenchymal cells can be detected early by microtubule destabilization and the repositioning of the centrosome from the cell-cell junction to the cell center. Consistent with their high migration velocities, cells in intermediate states produced low contractile forces compared with epithelial and mesenchymal cells. The high contractile forces in mesenchymal cells powered a retrograde flow pushing the nucleus away from cell adhesion to the extracellular matrix. Therefore, cells in intermediate state had structural and mechanical properties that were distinct but not necessarily intermediate between epithelial and mesenchymal cells. Based on these observations, we found that a panel of triple-negative breast cancer lines had intermediate rather than mesenchymal characteristics suggesting that the structural and mechanical properties of the intermediate state are important for understanding tumor-cell dissemination.

cell biology↗

bioRxiv2019

Spatial integration of mechanical forces by alpha-actinin establishes actin network symmetry.

Cell and tissue morphogenesis depend on the production and spatial organization of tensional forces in the actin cytoskeleton. Actin network architecture is complex because it is made of distinct modules in which filaments adopt a variety of organizations. The assembly and dynamics of these modules is well described but the self-organisation rules directing the global network architecture are much less understood. Here we investigated the mechanism regulating the interplay between network architecture and the geometry of cells extracellular environment. We found that -actinin, a filament crosslinker, is essential for network symmetry to be consistent with extracellular microenvironment symmetry. It appeared to be required for the interconnection of transverse arcs with radial fibres to ensure an appropriate balance between forces at cell adhesions and across the entire actin network. Furthermore, the connectivity of the actin network appeared necessary for the cell ability to integrate and adapt to complex patterns of extracellular cues as they migrate. Altogether, our study has unveiled a role of actin-filament crosslinking in the physical integration of mechanical forces throughout the entire cell, and the role of this integration in the establishment and adaptation of intracellular symmetry axes in accordance with the geometry of extracellular cues.

cell biology↗