Aurora kinase A enables collective invasion and metastasis by endowing a leader cell phenotype and stabilizing Eplin-mediated cohesion with follower cells

The metastatic process initiates with collective cell invasion into surrounding tissues and axillary nodes, and subsequent colonization at a distant site. Previously, we found collective invasion is augmented during the G2 cell cycle phase, facilitated through Aurora kinase A (AURKA)-mediated centrosome polarization in the leader cell. Here, we identify cell cycle-associated gene signatures as overrepresented in axilla and liver metastatic sites, with AURKA expression strongly correlated with breast cancer metastasis signatures, and pan-cancer patient survival. Then, we show GFP-AURKA expression endows breast epithelia cells with the ability to form metastatic outgrowths within immune-incompetent chicken embryos. Multi-parametric imaging of wound closure assays reveals phenotypes enabled by, and dependent upon AURKA expression. We discover leader cells express AURKA and acquire front-polarized centrosomes, which differentiates them from other cells in the migrating group. Ectopic expression of GFP-AURKA induces a leader cell phenotype. Conversely, inhibition of AURKA activity alters actin dynamics, promotes turnover of cell contacts, and reduces coordination within migrating groups. Specifically, AURKA interacts with the actin regulator EPLIN, and AURKA inhibition localizes EPLIN to lamellipodia and away from E-cadherin-positive contacts. Inhibiting these necessary roles for AURKA may provide a critical barrier against the metastatic spread of human breast carcinoma cells. ### Competing Interest Statement The authors have declared no competing interest. Canadian Institutes of Health Research, CIHR F-19 03865, TFRI PPG F22-00533, CIHR F22-03789, CIHR F24-00975

A non-invasive approach for understanding localized force generation in 3D tissues

The development, maintenance and repair of epithelial tissues critically rely on adhesion complexes that ensure structural integrity while enabling dynamic remodeling. Such tissue remodeling underpins both physiological morphogenesis and pathological transformation. Central to these processes are mechanical forces, which tightly couple cytoskeletal organization to adhesion dynamics. Despite extensive investigations in two dimensional (2D) systems, how these interactions are orchestrated within polarized three dimensional (3D) epithelia remains largely unresolved. Here, we introduce a new, non invasive strategy to probe localized force generation within 3D epithelial tissues. We engineered elastic polyacrylamide (PAAm) microbeads with cell mimetic size and mechanical properties, enabling their seamless integration. In contrast to conventional bead injection approaches, these PAAm microbeads were spontaneously engulfed by the tissue, thereby establishing an intrinsic interface through which bead deformation can be directly correlated with local cytoskeletal architecture and adhesion organization, as visualized through high resolution imaging combined with quantitative 3D computational reconstruction. Using this approach, we demonstrated that localized mechanical perturbations trigger pronounced cytoskeletal remodelling while preserving global tissue polarity. We further identified the extracellular matrix composition as key determinant of bead tissue interactions, with collagen I coating promoting robust adhesion and efficient incorporation. At the bead / cell interface, cells assembled tension bearing focal adhesions and organized actin stress fibers, revealing the emergence of active cortical stress. Strikingly, quantitative analysis of bead deformation revealed a previously unrecognized mechanical duality: spatially segregated regions of pulling and pushing forces coexisted at the microscale, directly correlated with local cytoskeleton dynamics. This finding challenges the prevailing view of homogenous force application and instead supports a model in which cells deploy highly coordinated and spatially patterned force generating strategies. Altogether, this integrative and non invasive strategy offers a comprehensive pipeline for dissecting the dynamic interplay between cellular processes and tissue mechanics during morphogenesis in 3D model systems. ### Competing Interest Statement The authors have declared no competing interest. CNRS, MiTi interdisciplinary programs Fondation ARC pour la Recherche sur le Cancer, https://ror.org/0489qz649, PGA 2023 Agence Nationale de la Recherche, ANR-25-CE13-3505-01, ANR-16-CONV0001, ANR24-INBS-0005 FBI BIOGEN INSERM 2021-2023 Cancer Control strategy, PCSI 25CP045-00 Excellence Initiative of Aix-Marseille University–A*MIDEX

Nematic structures contribute to robust zygotic polarization in C. elegans

The C. elegans zygote is a powerful model for asymmetric cell division. Its strikingly patterned cortex features thick F-actin bundles and myosin foci, contractile nematic structures that drive characteristic surface ruffles. Early in the cell cycle, symmetry breaks near the sperm-contributed centrosomes, typically at the presumptive posterior pole, and is marked by local downregulation of contractility. This initiates a cortical flow that polarizes the cell and enables PAR proteins to establish anterior and posterior domains. While biochemical mechanisms maintaining these domains are well understood, the mechanical role of cortical architecture in polarization remains unclear. We developed a three-dimensional (3D) mechanical model of C. elegans zygote polarization that represents the actin bundles and myosin foci of the cortex as a network of stiff contractile filaments. We measured cortical flow with high spatiotemporal resolution by tracking myosin foci, and used these data alongside mechanical properties from the literature to parametrize the model. The model simulates the complete polarization process in 3D, from symmetry breaking through domain stabilization, and reproduces key cortical dynamics including flow profiles, surface ruffles, and tension anisotropy. Domain arrest near the embryo midpoint emerges from density-dependent contractility regulation, in which cortical material redistribution during flow creates a mechanical negative feedback that balances anterior and posterior tension. We find that compressive flow aligns actin bundles in the anterior domain and generates anisotropic tension perpendicular to the flow direction. Although this alignment is not essential for polarization when symmetry breaking occurs at the pole, it contributes to this process when symmetry breaking occurs laterally. In such cases, anisotropic tension from aligned bundles drives axis convergence by rotating the posterior domain towards the nearest pole. Nematic cortical structures therefore ensure robust alignment of the polarization axis. ### Competing Interest Statement The authors have declared no competing interest. FWO, G008423N, 11D9923N, 1194222N Swiss National Science Foundation, 310030_197749

JCI - Loss of RPGR disrupts motile cilia and causes primary ciliary dyskinesia by affecting F-actin dynamics