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 AU - Schwayer, Cornelia AU - Shamipour, Shayan AU - Pranjic-Ferscha, Kornelija AU - Schauer, Alexandra AU - Balda, M AU - Tada, M AU - Matter, K AU - Heisenberg, Carl-Philipp J ID - 7001 IS - 4 JF - Cell SN - 0092-8674 TI - Mechanosensation of tight junctions depends on ZO-1 phase separation and flow VL - 179 ER - TY - JOUR AB - Migrating cells penetrate tissue barriers during development, inflammatory responses, and tumor metastasis. We study if migration in vivo in such three-dimensionally confined environments requires changes in the mechanical properties of the surrounding cells using embryonic Drosophila melanogaster hemocytes, also called macrophages, as a model. We find that macrophage invasion into the germband through transient separation of the apposing ectoderm and mesoderm requires cell deformations and reductions in apical tension in the ectoderm. Interestingly, the genetic pathway governing these mechanical shifts acts downstream of the only known tumor necrosis factor superfamily member in Drosophila, Eiger, and its receptor, Grindelwald. Eiger-Grindelwald signaling reduces levels of active Myosin in the germband ectodermal cortex through the localization of a Crumbs complex component, Patj (Pals-1-associated tight junction protein). We therefore elucidate a distinct molecular pathway that controls tissue tension and demonstrate the importance of such regulation for invasive migration in vivo. AU - Ratheesh, Aparna AU - Biebl, Julia AU - Smutny, Michael AU - Veselá, Jana AU - Papusheva, Ekaterina AU - Krens, Gabriel AU - Kaufmann, Walter AU - György, Attila AU - Casano, Alessandra M AU - Siekhaus, Daria E ID - 308 IS - 3 JF - Developmental Cell TI - Drosophila TNF modulates tissue tension in the embryo to facilitate macrophage invasive migration VL - 45 ER - TY - JOUR AB - During epithelial tissue development, repair, and homeostasis, adherens junctions (AJs) ensure intercellular adhesion and tissue integrity while allowing for cell and tissue dynamics. Mechanical forces play critical roles in AJs’ composition and dynamics. Recent findings highlight that beyond a well-established role in reinforcing cell-cell adhesion, AJ mechanosensitivity promotes junctional remodeling and polarization, thereby regulating critical processes such as cell intercalation, division, and collective migration. Here, we provide an integrated view of mechanosensing mechanisms that regulate cell-cell contact composition, geometry, and integrity under tension and highlight pivotal roles for mechanosensitive AJ remodeling in preserving epithelial integrity and sustaining tissue dynamics. AU - Nunes Pinheiro, Diana C AU - Bellaïche, Yohanns ID - 54 IS - 1 JF - Developmental Cell TI - Mechanical force-driven adherents junction remodeling and epithelial dynamics VL - 47 ER -