TY - JOUR AB - Efficient migration on adhesive surfaces involves the protrusion of lamellipodial actin networks and their subsequent stabilization by nascent adhesions. The actin-binding protein lamellipodin (Lpd) is thought to play a critical role in lamellipodium protrusion, by delivering Ena/VASP proteins onto the growing plus ends of actin filaments and by interacting with the WAVE regulatory complex, an activator of the Arp2/3 complex, at the leading edge. Using B16-F1 melanoma cell lines, we demonstrate that genetic ablation of Lpd compromises protrusion efficiency and coincident cell migration without altering essential parameters of lamellipodia, including their maximal rate of forward advancement and actin polymerization. We also confirmed lamellipodia and migration phenotypes with CRISPR/Cas9-mediated Lpd knockout Rat2 fibroblasts, excluding cell type-specific effects. Moreover, computer-aided analysis of cell-edge morphodynamics on B16-F1 cell lamellipodia revealed that loss of Lpd correlates with reduced temporal protrusion maintenance as a prerequisite of nascent adhesion formation. We conclude that Lpd optimizes protrusion and nascent adhesion formation by counteracting frequent, chaotic retraction and membrane ruffling.This article has an associated First Person interview with the first author of the paper. AU - Dimchev, Georgi A AU - Amiri, Behnam AU - Humphries, Ashley C. AU - Schaks, Matthias AU - Dimchev, Vanessa AU - Stradal, Theresia E. B. AU - Faix, Jan AU - Krause, Matthias AU - Way, Michael AU - Falcke, Martin AU - Rottner, Klemens ID - 8434 IS - 7 JF - Journal of Cell Science KW - Cell Biology SN - 0021-9533 TI - Lamellipodin tunes cell migration by stabilizing protrusions and promoting adhesion formation VL - 133 ER - TY - JOUR AB - Autoluminescent plants engineered to express a bacterial bioluminescence gene cluster in plastids have not been widely adopted because of low light output. We engineered tobacco plants with a fungal bioluminescence system that converts caffeic acid (present in all plants) into luciferin and report self-sustained luminescence that is visible to the naked eye. Our findings could underpin development of a suite of imaging tools for plants. AU - Mitiouchkina, Tatiana AU - Mishin, Alexander S. AU - Gonzalez Somermeyer, Louisa AU - Markina, Nadezhda M. AU - Chepurnyh, Tatiana V. AU - Guglya, Elena B. AU - Karataeva, Tatiana A. AU - Palkina, Kseniia A. AU - Shakhova, Ekaterina S. AU - Fakhranurova, Liliia I. AU - Chekova, Sofia V. AU - Tsarkova, Aleksandra S. AU - Golubev, Yaroslav V. AU - Negrebetsky, Vadim V. AU - Dolgushin, Sergey A. AU - Shalaev, Pavel V. AU - Shlykov, Dmitry AU - Melnik, Olesya A. AU - Shipunova, Victoria O. AU - Deyev, Sergey M. AU - Bubyrev, Andrey I. AU - Pushin, Alexander S. AU - Choob, Vladimir V. AU - Dolgov, Sergey V. AU - Kondrashov, Fyodor AU - Yampolsky, Ilia V. AU - Sarkisyan, Karen S. ID - 7889 JF - Nature Biotechnology SN - 1087-0156 TI - Plants with genetically encoded autoluminescence VL - 38 ER - TY - GEN AB - Tension of the actomyosin cell cortex plays a key role in determining cell-cell contact growth and size. The level of cortical tension outside of the cell-cell contact, when pulling at the contact edge, scales with the total size to which a cell-cell contact can grow1,2. Here we show in zebrafish primary germ layer progenitor cells that this monotonic relationship only applies to a narrow range of cortical tension increase, and that above a critical threshold, contact size inversely scales with cortical tension. This switch from cortical tension increasing to decreasing progenitor cell-cell contact size is caused by cortical tension promoting E-cadherin anchoring to the actomyosin cytoskeleton, thereby increasing clustering and stability of E-cadherin at the contact. Once tension-mediated E-cadherin stabilization at the contact exceeds a critical threshold level, the rate by which the contact expands in response to pulling forces from the cortex sharply drops, leading to smaller contacts at physiologically relevant timescales of contact formation. Thus, the activity of cortical tension in expanding cell-cell contact size is limited by tension stabilizing E-cadherin-actin complexes at the contact. AU - Slovakova, Jana AU - Sikora, Mateusz K AU - Caballero Mancebo, Silvia AU - Krens, Gabriel AU - Kaufmann, Walter AU - Huljev, Karla AU - Heisenberg, Carl-Philipp J ID - 9750 T2 - bioRxiv TI - Tension-dependent stabilization of E-cadherin limits cell-cell contact expansion ER - TY - JOUR AB - Eukaryotic cells migrate by coupling the intracellular force of the actin cytoskeleton to the environment. While force coupling is usually mediated by transmembrane adhesion receptors, especially those of the integrin family, amoeboid cells such as leukocytes can migrate extremely fast despite very low adhesive forces1. Here we show that leukocytes cannot only migrate under low adhesion but can also transmit forces in the complete absence of transmembrane force coupling. When confined within three-dimensional environments, they use the topographical features of the substrate to propel themselves. Here the retrograde flow of the actin cytoskeleton follows the texture of the substrate, creating retrograde shear forces that are sufficient to drive the cell body forwards. Notably, adhesion-dependent and adhesion-independent migration are not mutually exclusive, but rather are variants of the same principle of coupling retrograde actin flow to the environment and thus can potentially operate interchangeably and simultaneously. As adhesion-free migration is independent of the chemical composition of the environment, it renders cells completely autonomous in their locomotive behaviour. AU - Reversat, Anne AU - Gärtner, Florian R AU - Merrin, Jack AU - Stopp, Julian A AU - Tasciyan, Saren AU - Aguilera Servin, Juan L AU - De Vries, Ingrid AU - Hauschild, Robert AU - Hons, Miroslav AU - Piel, Matthieu AU - Callan-Jones, Andrew AU - Voituriez, Raphael AU - Sixt, Michael K ID - 7885 JF - Nature SN - 00280836 TI - Cellular locomotion using environmental topography VL - 582 ER - TY - JOUR AB - This paper presents a novel abstraction technique for analyzing Lyapunov and asymptotic stability of polyhedral switched systems. A polyhedral switched system is a hybrid system in which the continuous dynamics is specified by polyhedral differential inclusions, the invariants and guards are specified by polyhedral sets and the switching between the modes do not involve reset of variables. A finite state weighted graph abstracting the polyhedral switched system is constructed from a finite partition of the state–space, such that the satisfaction of certain graph conditions, such as the absence of cycles with product of weights on the edges greater than (or equal) to 1, implies the stability of the system. However, the graph is in general conservative and hence, the violation of the graph conditions does not imply instability. If the analysis fails to establish stability due to the conservativeness in the approximation, a counterexample (cycle with product of edge weights greater than or equal to 1) indicating a potential reason for the failure is returned. Further, a more precise approximation of the switched system can be constructed by considering a finer partition of the state–space in the construction of the finite weighted graph. We present experimental results on analyzing stability of switched systems using the above method. AU - Garcia Soto, Miriam AU - Prabhakar, Pavithra ID - 7426 IS - 5 JF - Nonlinear Analysis: Hybrid Systems SN - 1751-570X TI - Abstraction based verification of stability of polyhedral switched systems VL - 36 ER - TY - THES AB - Metabolic adaptation is a critical feature of migrating cells. It tunes the metabolic programs of migrating cells to allow them to efficiently exert their crucial roles in development, inflammatory responses and tumor metastasis. Cell migration through physically challenging contexts requires energy. However, how the metabolic reprogramming that underlies in vivo cell invasion is controlled is still unanswered. In my PhD project, I identify a novel conserved metabolic shift in Drosophila melanogaster immune cells that by modulating their bioenergetic potential controls developmentally programmed tissue invasion. We show that this regulation requires a novel conserved nuclear protein, named Atossa. Atossa enhances the transcription of a set of proteins, including an RNA helicase Porthos and two metabolic enzymes, each of which increases the tissue invasion of leading Drosophila macrophages and can rescue the atossa mutant phenotype. Porthos selectively regulates the translational efficiency of a subset of mRNAs containing a 5’-UTR cis-regulatory TOP-like sequence. These 5’TOPL mRNA targets encode mitochondrial-related proteins, including subunits of mitochondrial oxidative phosphorylation (OXPHOS) components III and V and other metabolic-related proteins. Porthos powers up mitochondrial OXPHOS to engender a sufficient ATP supply, which is required for tissue invasion of leading macrophages. Atossa’s two vertebrate orthologs rescue the invasion defect. In my PhD project, I elucidate that Atossa displays a conserved developmental metabolic control to modulate metabolic capacities and the cellular energy state, through altered transcription and translation, to aid the tissue infiltration of leading cells into energy demanding barriers. AU - Emtenani, Shamsi ID - 8983 SN - 2663-337X TI - Metabolic regulation of Drosophila macrophage tissue invasion ER - TY - GEN AB - The infiltration of immune cells into tissues underlies the establishment of tissue resident macrophages, and responses to infections and tumors. Yet the mechanisms immune cells utilize to negotiate tissue barriers in living organisms are not well understood, and a role for cortical actin has not been examined. Here we find that the tissue invasion of Drosophila macrophages, also known as plasmatocytes or hemocytes, utilizes enhanced cortical F-actin levels stimulated by the Drosophila member of the fos proto oncogene transcription factor family (Dfos, Kayak). RNA sequencing analysis and live imaging show that Dfos enhances F-actin levels around the entire macrophage surface by increasing mRNA levels of the membrane spanning molecular scaffold tetraspanin TM4SF, and the actin cross-linking filamin Cheerio which are themselves required for invasion. Cortical F-actin levels are critical as expressing a dominant active form of Diaphanous, a actin polymerizing Formin, can rescue the Dfos Dominant Negative macrophage invasion defect. In vivo imaging shows that Dfos is required to enhance the efficiency of the initial phases of macrophage tissue entry. Genetic evidence argues that this Dfos-induced program in macrophages counteracts the constraint produced by the tension of surrounding tissues and buffers the mechanical properties of the macrophage nucleus from affecting tissue entry. We thus identify tuning the cortical actin cytoskeleton through Dfos as a key process allowing efficient forward movement of an immune cell into surrounding tissues. AU - Belyaeva, Vera AU - Wachner, Stephanie AU - Gridchyn, Igor AU - Linder, Markus AU - Emtenani, Shamsi AU - György, Attila AU - Sibilia, Maria AU - Siekhaus, Daria E ID - 8557 T2 - bioRxiv TI - Cortical actin properties controlled by Drosophila Fos aid macrophage infiltration against surrounding tissue resistance ER - TY - GEN AB - Holes in planar Ge have high mobilities, strong spin-orbit interaction and electrically tunable g-factors, and are therefore emerging as a promising candidate for hybrid superconductorsemiconductor devices. This is further motivated by the observation of supercurrent transport in planar Ge Josephson Field effect transistors (JoFETs). A key challenge towards hybrid germanium quantum technology is the design of high quality interfaces and superconducting contacts that are robust against magnetic fields. By combining the assets of Al, which has a long superconducting coherence, and Nb, which has a significant superconducting gap, we form low-disordered JoFETs with large ICRN products that are capable of withstanding high magnetic fields. We furthermore demonstrate the ability of phase-biasing individual JoFETs opening up an avenue to explore topological superconductivity in planar Ge. The persistence of superconductivity in the reported hybrid devices beyond 1.8 T paves the way towards integrating spin qubits and proximity-induced superconductivity on the same chip. AU - Aggarwal, Kushagra AU - Hofmann, Andrea C AU - Jirovec, Daniel AU - Prieto Gonzalez, Ivan AU - Sammak, Amir AU - Botifoll, Marc AU - Marti-Sanchez, Sara AU - Veldhorst, Menno AU - Arbiol, Jordi AU - Scappucci, Giordano AU - Katsaros, Georgios ID - 8831 T2 - arXiv TI - Enhancement of proximity induced superconductivity in planar Germanium ER - TY - JOUR AB - The molecular anatomy of synapses defines their characteristics in transmission and plasticity. Precise measurements of the number and distribution of synaptic proteins are important for our understanding of synapse heterogeneity within and between brain regions. Freeze–fracture replica immunogold electron microscopy enables us to analyze them quantitatively on a two-dimensional membrane surface. Here, we introduce Darea software, which utilizes deep learning for analysis of replica images and demonstrate its usefulness for quick measurements of the pre- and postsynaptic areas, density and distribution of gold particles at synapses in a reproducible manner. We used Darea for comparing glutamate receptor and calcium channel distributions between hippocampal CA3-CA1 spine synapses on apical and basal dendrites, which differ in signaling pathways involved in synaptic plasticity. We found that apical synapses express a higher density of α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors and a stronger increase of AMPA receptors with synaptic size, while basal synapses show a larger increase in N-methyl-D-aspartate (NMDA) receptors with size. Interestingly, AMPA and NMDA receptors are segregated within postsynaptic sites and negatively correlated in density among both apical and basal synapses. In the presynaptic sites, Cav2.1 voltage-gated calcium channels show similar densities in apical and basal synapses with distributions consistent with an exclusion zone model of calcium channel-release site topography. AU - Kleindienst, David AU - Montanaro-Punzengruber, Jacqueline-Claire AU - Bhandari, Pradeep AU - Case, Matthew J AU - Fukazawa, Yugo AU - Shigemoto, Ryuichi ID - 8532 IS - 18 JF - International Journal of Molecular Sciences SN - 16616596 TI - Deep learning-assisted high-throughput analysis of freeze-fracture replica images applied to glutamate receptors and calcium channels at hippocampal synapses VL - 21 ER - TY - CONF AB - Interprocedural data-flow analyses form an expressive and useful paradigm of numerous static analysis applications, such as live variables analysis, alias analysis and null pointers analysis. The most widely-used framework for interprocedural data-flow analysis is IFDS, which encompasses distributive data-flow functions over a finite domain. On-demand data-flow analyses restrict the focus of the analysis on specific program locations and data facts. This setting provides a natural split between (i) an offline (or preprocessing) phase, where the program is partially analyzed and analysis summaries are created, and (ii) an online (or query) phase, where analysis queries arrive on demand and the summaries are used to speed up answering queries. In this work, we consider on-demand IFDS analyses where the queries concern program locations of the same procedure (aka same-context queries). We exploit the fact that flow graphs of programs have low treewidth to develop faster algorithms that are space and time optimal for many common data-flow analyses, in both the preprocessing and the query phase. We also use treewidth to develop query solutions that are embarrassingly parallelizable, i.e. the total work for answering each query is split to a number of threads such that each thread performs only a constant amount of work. Finally, we implement a static analyzer based on our algorithms, and perform a series of on-demand analysis experiments on standard benchmarks. Our experimental results show a drastic speed-up of the queries after only a lightweight preprocessing phase, which significantly outperforms existing techniques. AU - Chatterjee, Krishnendu AU - Goharshady, Amir Kafshdar AU - Ibsen-Jensen, Rasmus AU - Pavlogiannis, Andreas ID - 7810 SN - 03029743 T2 - European Symposium on Programming TI - Optimal and perfectly parallel algorithms for on-demand data-flow analysis VL - 12075 ER -