Kinesin-8 Motors Improve Nuclear Centering by Promoting Microtubule Catastrophe

In fission yeast, microtubules push against the cell edge, thereby positioning the nucleus in the cell center. Kinesin-8 motors regulate microtubule catastrophe; however, their role in nuclear positioning is not known. Here we develop a physical model that describes how kinesin-8 motors affect nuclear centering by promoting a microtubule catastrophe. Our model predicts the improved centering of the nucleus in the presence of motors, which we confirmed experimentally in living cells. The model also predicts a characteristic time for the recentering of a displaced nucleus, which is supported by our experiments where we displaced the nucleus using optical tweezers

Centrosomal microtubule nucleation regulates radial migration of projection neurons independently of polarization in the developing brain

Cortical projection neurons polarize and form an axon while migrating radially. Even though these dynamic processes are closely interwoven, they are regulated separately-the neurons terminate their migration when reaching their destination, the cortical plate, but continue to grow their axons. Here, we show that in rodents, the centrosome distinguishes these processes. Newly developed molecular tools modulating centrosomal microtubule nucleation combined with in vivo imaging uncovered that dysregulation of centro-somal microtubule nucleation abrogated radial migration without affecting axon formation. Tightly regu-lated centrosomal microtubule nucleation was required for periodic formation of the cytoplasmic dilation at the leading process, which is essential for radial migration. The microtubule nucleating factor g-tubulin decreased at neuronal centrosomes during the migratory phase. As distinct microtubule networks drive neuronal polarization and radial migration, this provides insight into how neuronal migratory defects occur without largely affecting axonal tracts in human developmental cortical dysgeneses, caused by mutations in g-tubulin.ISSN:0896-6273ISSN:1097-419

Isotropic actomyosin dynamics promote organization of the apical cell cortex in epithelial cells

Although cortical actin plays an important role in cellular mechanics and morphogenesis, there is surprisingly little information on cortex organization at the apical surface of cells. In this paper, we characterize organization and dynamics of microvilli (MV) and a previously unappreciated actomyosin network at the apical surface of Madin–Darby canine kidney cells. In contrast to short and static MV in confluent cells, the apical surfaces of nonconfluent epithelial cells (ECs) form highly dynamic protrusions, which are often oriented along the plane of the membrane. These dynamic MV exhibit complex and spatially correlated reorganization, which is dependent on myosin II activity. Surprisingly, myosin II is organized into an extensive network of filaments spanning the entire apical membrane in nonconfluent ECs. Dynamic MV, myosin filaments, and their associated actin filaments form an interconnected, prestressed network. Interestingly, this network regulates lateral mobility of apical membrane probes such as integrins or epidermal growth factor receptors, suggesting that coordinated actomyosin dynamics contributes to apical cell membrane organization

Opto-fluidically multiplexed assembly and micro-robotics.

Acknowledgements: We acknowledge funding by the Max Planck Society, the Karlsruhe Institute of Technology and the University of Cambridge. MK further acknowledges support by the European Research Council, in particular the ERC Starting Grant GHOSTs (Grant No. 853619) and the Hector Foundation. MK and EE acknowledge support by the Volkswagen Foundation (Life! Grant No. 92772). Additionally, the Kreysing lab is co-funded by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) under Germany’s Excellence Strategy – 2082/1 – 390761711 and Research Grant 515462906. We also acknowledge support by the Karlsruhe School of Optics & Photonics (KSOP). WL gratefully acknowledges funding from the Engineering and Physical Sciences Research Council (EPSRC studentship). We thank Nicola Maghelli from the Advanced Imaging Facility and Sergei Klykov from the Scientific Computing Facility at MPI-CBG for software support in LabVIEW and Python. We kindly acknowledge the help of Gayathri Nadar and HongKee Moon from the Scientific Computing Facility at MPI-CBG with reconstruction of the target coordinates for the humanoid robots (Fig. 4e). We also thank Franziska Friedrich from the Media Technologies and Outreach Facility at MPI-CBG for her support. MK and EE thank Michael Schlierf (B CUBE, TU Dresden), Benjamin Seelbinder, Iliya D. Stoev, Susan Wagner and Christoph Zechner (all MPI-CBG Dresden) for stimulating discussions. We thank Iain Patten for valuable discussions on the structure and layout of the manuscript. We thank Núria Taberner from VIZCIE for creating the conceptual 3D-visualization of our technique in Fig. 1a.Funder: Max-Planck-Gesellschaft (Max Planck Society); doi: https://doi.org/10.13039/501100004189Funder: Helmholtz Association; doi: https://doi.org/10.13039/501100009318Funder: Karlsruher Institut für Technologie (Karlsruhe Institute of Technology); doi: https://doi.org/10.13039/100009133Funder: Karlsruhe Institute of Technology | Helmholtz International Research School for Teratronics, Karlsruher Institut für Technologie (Helmholtz International Research School for Teratronics, Karlsruhe Institute of Technology); doi: https://doi.org/10.13039/501100009484Funder: RCUK | Economic and Social Research Council (ESRC); doi: https://doi.org/10.13039/501100000269Funder: University of Cambridge; doi: https://doi.org/10.13039/501100000735Techniques for high-definition micromanipulations, such as optical tweezers, hold substantial interest across a wide range of disciplines. However, their applicability remains constrained by material properties and laser exposure. And while microfluidic manipulations have been suggested as an alternative, their inherent capabilities are limited and further hindered by practical challenges of implementation and control. Here we show that the iterative application of laser-induced, localized flow fields can be used for the relative positioning of multiple micro-particles, irrespectively of their material properties. Compared to the standing theoretical proposal, our method keeps particles mobile, and we show that their precision manipulation is non-linearly accelerated via the multiplexing of temperature stimuli below the heat diffusion limit. The resulting flow fields are topologically rich and mathematically predictable. They represent unprecedented microfluidic control capabilities that are illustrated by the actuation of humanoid micro-robots with up to 30 degrees of freedom, whose motions are sufficiently well-defined to reliably communicate personal characteristics such as gender, happiness and nervousness. Our results constitute high-definition micro-fluidic manipulations with transformative potential for assembly, micro-manufacturing, the life sciences, robotics and opto-hydraulically actuated micro-factories

Opto-fluidically multiplexed assembly and micro-robotics

Abstract Techniques for high-definition micromanipulations, such as optical tweezers, hold substantial interest across a wide range of disciplines. However, their applicability remains constrained by material properties and laser exposure. And while microfluidic manipulations have been suggested as an alternative, their inherent capabilities are limited and further hindered by practical challenges of implementation and control. Here we show that the iterative application of laser-induced, localized flow fields can be used for the relative positioning of multiple micro-particles, irrespectively of their material properties. Compared to the standing theoretical proposal, our method keeps particles mobile, and we show that their precision manipulation is non-linearly accelerated via the multiplexing of temperature stimuli below the heat diffusion limit. The resulting flow fields are topologically rich and mathematically predictable. They represent unprecedented microfluidic control capabilities that are illustrated by the actuation of humanoid micro-robots with up to 30 degrees of freedom, whose motions are sufficiently well-defined to reliably communicate personal characteristics such as gender, happiness and nervousness. Our results constitute high-definition micro-fluidic manipulations with transformative potential for assembly, micro-manufacturing, the life sciences, robotics and opto-hydraulically actuated micro-factories

NSC230378

A key aspect of life is sexual reproduction, which requires concerted movement. For successful mixing of the genetic material, molecular motors move the nucleus back and forth inside the cell. How motors work together to produce these large-scale movements, however, remains a mystery. To answer this question, we studied nuclear movement in fission yeast, which is driven by motor proteins pulling on microtubules. We show that motor proteins dynamically redistribute from one part of the cell to the other, generating asymmetric patterns of motors and, consequently, of forces that generate movement. By combining quantitative live cell imaging and laser ablation with a theoretical model, we find that this dynamic motor redistribution occurs purely as a result of changes in the mechan- ical strain sensed by the motor proteins. Our work therefore demonstrates that spatio-temporal pattern formation within a cell can occur as a result of mechani- cal cues (Vogel et al., 2009), which differs from conventional molecular signaling, as well as from self-organization based on a combination of biochemical reactions and diffusion

Self-Organization of Dynein Motors Generates Meiotic Nuclear Oscillations

Meiotic nuclear oscillations in the fission yeast Schizosaccharomyces pombe are crucial for proper chromosome pairing and recombination. We report a mechanism of these oscillations on the basis of collective behavior of dynein motors linking the cell cortex and dynamic microtubules that extend from the spindle pole body in opposite directions. By combining quantitative live cell imaging and laser ablation with a theoretical description, we show that dynein dynamically redistributes in the cell in response to load forces, resulting in more dynein attached to the leading than to the trailing microtubules. The redistribution of motors introduces an asymmetry of motor forces pulling in opposite directions, leading to the generation of oscillations. Our work provides the first direct in vivo observation of self-organized dynamic dynein distributions, which, owing to the intrinsic motor properties, generate regular large-scale movements in the cell

CLIJ: GPU-accelerated image processing for everyone

Web of Science1716