Biology subjects

Silberzan, P.

Publications and source records attributed to Silberzan, P..

4 recordsLinked to original sources

bioRxiv2025

Identification of PKN2 and MOB4 as Coordinators of Collective Cell Migration

In animals, collective cell migration is critical during development and adult life for repairing organs. It remains, however, poorly understood compared with single cell migration. The polymerization of branched actin by the RAC1-WAVE-Arp2/3 pathway is established to power membrane protrusions at the front of migrating cells, but also to maintain cell junctions in epithelial monolayers. Here we have identified novel regulators of collective cell migration using a two-pronged approach: candidates were extracted from publicly available RAC1-WAVE-Arp2/3 dependency maps and screened in a second step using CRISPR/Cas9 genetic inactivation. In a wound healing assay, PKN2 knockout (KO) MCF10A cells display decreased collective migration due to destabilization of adherens junctions, whereas MOB4 KO cells display increased collective migration with a loss of migration orientation. Upon wound healing, PKN2 relocalizes to lateral junctions and maintains coordinated migration in the monolayer, whereas MOB4 relocalizes to the front edge of leader and follower cells collectively migrating towards the wound. The role of MOB4 in controlling collective migration requires YAP1, since MOB4 KO cells fail to activate YAP1 and their phenotype is rescued by constitutively active YAP1. Together, these findings reveal two complementary activities required for coordinating cells in collective migration.

cell biology↗

bioRxiv2023

Vinculin Antagonizes Branched Actin in Controlling Membrane Protrusion, Cell Migration and Cell Cycle Progression

Vinculin is a mechanotransducer that reinforces links between cell adhesions and linear arrays of actin filaments upon myosin-mediated contractility. Both adhesions to the substratum and neighboring cells, however, are initiated within membrane protrusions that originate from Arp2/3-nucleated branched actin networks. Vinculin has been reported to interact with the Arp2/3 complex, but the role of this interaction remains poorly understood. Here we compared the phenotypes of vinculin knock-out (KO) cells with those of knock-in (KI) cells, where the point mutation P878A that impairs the Arp2/3 interaction is introduced in the two vinculin alleles of MCF10A mammary epithelial cells. The interaction of vinculin with Arp2/3 inhibits actin polymerization at membrane protrusions and decreases migration persistence of single cells. In cell monolayers, vinculin recruits Arp2/3 and the vinculin-Arp2/3 interaction participates in cell-cell junction plasticity. Through this interaction, vinculin controls the decision to enter a new cell cycle as a function of cell density.

cell biology↗

bioRxiv2022

Contractility-induced self-organization of smooth muscle cells: from multilayer cell sheets to dynamic three-dimensional clusters

Smooth muscle cells (SMCs) are mural cells that play a vital contractile function in many tissues. Abnormalities in SMC organization are associated with many diseases including atherosclerosis, asthma, and uterine fibroids. Various studies have reported that SMCs cultured on flat surfaces can spontaneously form three-dimensional clusters whose organization resembles that encountered in some of these pathological settings. Remarkably, how these structures form remains unknown. Here we combine in vitro experiments and physical modeling to show that three-dimensional clusters initiate when cellular contractile forces induce a hole in a flat SMC sheet, a process that can be modeled as the brittle fracture of a viscoelastic material. The subsequent evolution of the nascent cluster can be modeled as an active dewetting process with cluster shape evolution driven by a balance between cluster surface tension, arising from both cell contractility and adhesion, and cluster viscous dissipation. The description of the physical mechanisms governing the spontaneous emergence of these intriguing three-dimensional clusters offers insight into SMC-related disorders.

biophysics↗

bioRxiv2021

Crisscross multilayering of cell sheets

Simple hydrostatic skeletons such as the Hydras consist of two stacked layers of cells perpendicularly oriented. Although this crisscross architecture can be recapitulated in vitro, little is known on the formation of such multilayers starting from a monolayer. In the present article, we show that bilayering of myoblasts results from the organization and activity of the cells originally in the monolayer which can be described as a contractile active nematic. As expected, most of the +1/2 topological defects that are associated with this nematic order self-propel. However, a subpopulation of these defects remains immobile. Perpendicular bilayering occurs exclusively at these motionless defects. Indeed, cells located at the head of these defects converge toward the (immobile) core and accumulate there until they start migrating on top of the tail of the first layer while the tail cells migrate in the opposite direction under the head cells. Since the cells keep their initial orientations, the two stacked layers end up perpendicularly oriented. This concerted process leading to a bilayer is dependent on the apical secretion of Extra Cellular Matrix (ECM) by the cells. Indeed, we evidence the presence of ECM between the cell layers and at the apical surface of the topmost layer. ECM molecules are oriented in the direction of the cells that produce them, which may guide the migration of the subsequent cell layers on their apical side. Significance StatementHydrostatic skeletons such as that of the Hydra consist of two stacked layers of cells perpendicularly oriented whose coordinated contraction allows for complex movements. Such crisscross organization is also observed with myoblasts in culture. Confluent monolayers organize in well-aligned domains between which topological defects position themselves. Although these singularities are generally self-propelled, a fraction of them remains motionless. Perpendicular bilayering occurs exclusively at these particular pinned defects. Cells first accumulate at the head of the defects until they split in two perpendicular layers migrating in an antiparallel way on top of each other. Such a concerted process is highly dependent on the precise organization of the cell-secreted Extra Cellular Matrix (ECM).

biophysics↗