TY - JOUR AB - Migration frequently involves Rac-mediated protrusion of lamellipodia, formed by Arp2/3 complex-dependent branching thought to be crucial for force generation and stability of these networks. The formins FMNL2 and FMNL3 are Cdc42 effectors targeting to the lamellipodium tip and shown here to nucleate and elongate actin filaments with complementary activities in vitro. In migrating B16-F1 melanoma cells, both formins contribute to the velocity of lamellipodium protrusion. Loss of FMNL2/3 function in melanoma cells and fibroblasts reduces lamellipodial width, actin filament density and -bundling, without changing patterns of Arp2/3 complex incorporation. Strikingly, in melanoma cells, FMNL2/3 gene inactivation almost completely abolishes protrusion forces exerted by lamellipodia and modifies their ultrastructural organization. Consistently, CRISPR/Cas-mediated depletion of FMNL2/3 in fibroblasts reduces both migration and capability of cells to move against viscous media. Together, we conclude that force generation in lamellipodia strongly depends on FMNL formin activity, operating in addition to Arp2/3 complex-dependent filament branching. AU - Kage, Frieda AU - Winterhoff, Moritz AU - Dimchev, Vanessa AU - Müller, Jan AU - Thalheim, Tobias AU - Freise, Anika AU - Brühmann, Stefan AU - Kollasser, Jana AU - Block, Jennifer AU - Dimchev, Georgi A AU - Geyer, Matthias AU - Schnittler, Hams AU - Brakebusch, Cord AU - Stradal, Theresia AU - Carlier, Marie AU - Sixt, Michael K AU - Käs, Josef AU - Faix, Jan AU - Rottner, Klemens ID - 659 JF - Nature Communications SN - 20411723 TI - FMNL formins boost lamellipodial force generation VL - 8 ER - TY - JOUR AB - Growing microtubules are protected from depolymerization by the presence of a GTP or GDP/Pi cap. End-binding proteins of the EB1 family bind to the stabilizing cap, allowing monitoring of its size in real time. The cap size has been shown to correlate with instantaneous microtubule stability. Here we have quantitatively characterized the properties of cap size fluctuations during steadystate growth and have developed a theory predicting their timescale and amplitude from the kinetics of microtubule growth and cap maturation. In contrast to growth speed fluctuations, cap size fluctuations show a characteristic timescale, which is defined by the lifetime of the cap sites. Growth fluctuations affect the amplitude of cap size fluctuations; however, cap size does not affect growth speed, indicating that microtubules are far from instability during most of their time of growth. Our theory provides the basis for a quantitative understanding of microtubule stability fluctuations during steady-state growth. AU - Rickman, Jamie AU - Düllberg, Christian F AU - Cade, Nicholas AU - Griffin, Lewis AU - Surrey, Thomas ID - 660 IS - 13 JF - PNAS SN - 00278424 TI - Steady state EB cap size fluctuations are determined by stochastic microtubule growth and maturation VL - 114 ER - TY - JOUR AB - We report a direct-numerical-simulation study of the Taylor-Couette flow in the quasi-Keplerian regime at shear Reynolds numbers up to (105). Quasi-Keplerian rotating flow has been investigated for decades as a simplified model system to study the origin of turbulence in accretion disks that is not fully understood. The flow in this study is axially periodic and thus the experimental end-wall effects on the stability of the flow are avoided. Using optimal linear perturbations as initial conditions, our simulations find no sustained turbulence: the strong initial perturbations distort the velocity profile and trigger turbulence that eventually decays. AU - Shi, Liang AU - Hof, Björn AU - Rampp, Markus AU - Avila, Marc ID - 662 IS - 4 JF - Physics of Fluids SN - 10706631 TI - Hydrodynamic turbulence in quasi Keplerian rotating flows VL - 29 ER - TY - CONF AB - In this paper, we propose an approach to automatically compute invariant clusters for nonlinear semialgebraic hybrid systems. An invariant cluster for an ordinary differential equation (ODE) is a multivariate polynomial invariant g(u→, x→) = 0, parametric in u→, which can yield an infinite number of concrete invariants by assigning different values to u→ so that every trajectory of the system can be overapproximated precisely by the intersection of a group of concrete invariants. For semialgebraic systems, which involve ODEs with multivariate polynomial right-hand sides, given a template multivariate polynomial g(u→, x→), an invariant cluster can be obtained by first computing the remainder of the Lie derivative of g(u→, x→) divided by g(u→, x→) and then solving the system of polynomial equations obtained from the coefficients of the remainder. Based on invariant clusters and sum-of-squares (SOS) programming, we present a new method for the safety verification of hybrid systems. Experiments on nonlinear benchmark systems from biology and control theory show that our approach is efficient. AU - Kong, Hui AU - Bogomolov, Sergiy AU - Schilling, Christian AU - Jiang, Yu AU - Henzinger, Thomas A ID - 663 SN - 978-145034590-3 T2 - Proceedings of the 20th International Conference on Hybrid Systems TI - Safety verification of nonlinear hybrid systems based on invariant clusters ER - TY - JOUR AB - Perinatal exposure to penicillin may result in longlasting gut and behavioral changes. AU - Novarino, Gaia ID - 667 IS - 387 JF - Science Translational Medicine SN - 19466234 TI - The antisocial side of antibiotics VL - 9 ER -