@article{6497,
  abstract     = {T cells are actively scanning pMHC-presenting cells in lymphoid organs and nonlymphoid tissues (NLTs) with divergent topologies and confinement. How the T cell actomyosin cytoskeleton facilitates this task in distinct environments is incompletely understood. Here, we show that lack of Myosin IXb (Myo9b), a negative regulator of the small GTPase Rho, led to increased Rho-GTP levels and cell surface stiffness in primary T cells. Nonetheless, intravital imaging revealed robust motility of Myo9b−/− CD8+ T cells in lymphoid tissue and similar expansion and differentiation during immune responses. In contrast, accumulation of Myo9b−/− CD8+ T cells in NLTs was strongly impaired. Specifically, Myo9b was required for T cell crossing of basement membranes, such as those which are present between dermis and epidermis. As consequence, Myo9b−/− CD8+ T cells showed impaired control of skin infections. In sum, we show that Myo9b is critical for the CD8+ T cell adaptation from lymphoid to NLT surveillance and the establishment of protective tissue–resident T cell populations.},
  author       = {Moalli, Federica and Ficht, Xenia and Germann, Philipp and Vladymyrov, Mykhailo and Stolp, Bettina and de Vries, Ingrid and Lyck, Ruth and Balmer, Jasmin and Fiocchi, Amleto and Kreutzfeldt, Mario and Merkler, Doron and Iannacone, Matteo and Ariga, Akitaka and Stoffel, Michael H. and Sharpe, James and Bähler, Martin and Sixt, Michael K and Diz-Muñoz, Alba and Stein, Jens V.},
  issn         = {1540-9538},
  journal      = {The Journal of Experimental Medicine},
  number       = {7},
  pages        = {1869–1890},
  publisher    = {Rockefeller University Press},
  title        = {{The Rho regulator Myosin IXb enables nonlymphoid tissue seeding of protective CD8+T cells}},
  doi          = {10.1084/jem.20170896},
  volume       = {2015},
  year         = {2018},
}

@article{15,
  abstract     = {Although much is known about the physiological framework of T cell motility, and numerous rate-limiting molecules have been identified through loss-of-function approaches, an integrated functional concept of T cell motility is lacking. Here, we used in vivo precision morphometry together with analysis of cytoskeletal dynamics in vitro to deconstruct the basic mechanisms of T cell migration within lymphatic organs. We show that the contributions of the integrin LFA-1 and the chemokine receptor CCR7 are complementary rather than positioned in a linear pathway, as they are during leukocyte extravasation from the blood vasculature. Our data demonstrate that CCR7 controls cortical actin flows, whereas integrins mediate substrate friction that is sufficient to drive locomotion in the absence of considerable surface adhesions and plasma membrane flux.},
  author       = {Hons, Miroslav and Kopf, Aglaja and Hauschild, Robert and Leithner, Alexander F and Gärtner, Florian R and Abe, Jun and Renkawitz, Jörg and Stein, Jens and Sixt, Michael K},
  journal      = {Nature Immunology},
  number       = {6},
  pages        = {606 -- 616},
  publisher    = {Nature Publishing Group},
  title        = {{Chemokines and integrins independently tune actin flow and substrate friction during intranodal migration of T cells}},
  doi          = {10.1038/s41590-018-0109-z},
  volume       = {19},
  year         = {2018},
}

@inbook{153,
  abstract     = {Cells migrating in multicellular organisms steadily traverse complex three-dimensional (3D) environments. To decipher the underlying cell biology, current experimental setups either use simplified 2D, tissue-mimetic 3D (e.g., collagen matrices) or in vivo environments. While only in vivo experiments are truly physiological, they do not allow for precise manipulation of environmental parameters. 2D in vitro experiments do allow mechanical and chemical manipulations, but increasing evidence demonstrates substantial differences of migratory mechanisms in 2D and 3D. Here, we describe simple, robust, and versatile “pillar forests” to investigate cell migration in complex but fully controllable 3D environments. Pillar forests are polydimethylsiloxane-based setups, in which two closely adjacent surfaces are interconnected by arrays of micrometer-sized pillars. Changing the pillar shape, size, height and the inter-pillar distance precisely manipulates microenvironmental parameters (e.g., pore sizes, micro-geometry, micro-topology), while being easily combined with chemotactic cues, surface coatings, diverse cell types and advanced imaging techniques. Thus, pillar forests combine the advantages of 2D cell migration assays with the precise definition of 3D environmental parameters.},
  author       = {Renkawitz, Jörg and Reversat, Anne and Leithner, Alexander F and Merrin, Jack and Sixt, Michael K},
  booktitle    = {Methods in Cell Biology},
  issn         = {0091679X},
  pages        = {79 -- 91},
  publisher    = {Academic Press},
  title        = {{Micro-engineered “pillar forests” to study cell migration in complex but controlled 3D environments}},
  doi          = {10.1016/bs.mcb.2018.07.004},
  volume       = {147},
  year         = {2018},
}

@article{402,
  abstract     = {During metastasis, malignant cells escape the primary tumor, intravasate lymphatic vessels, and reach draining sentinel lymph nodes before they colonize distant organs via the blood circulation. Although lymph node metastasis in cancer patients correlates with poor prognosis, evidence is lacking as to whether and how tumor cells enter the bloodstream via lymph nodes. To investigate this question, we delivered carcinoma cells into the lymph nodes of mice by microinfusing the cells into afferent lymphatic vessels. We found that tumor cells rapidly infiltrated the lymph node parenchyma, invaded blood vessels, and seeded lung metastases without involvement of the thoracic duct. These results suggest that the lymph node blood vessels can serve as an exit route for systemic dissemination of cancer cells in experimental mouse models. Whether this form of tumor cell spreading occurs in cancer patients remains to be determined.},
  author       = {Brown, Markus and Assen, Frank P and Leithner, Alexander F and Abe, Jun and Schachner, Helga and Asfour, Gabriele and Bagó Horváth, Zsuzsanna and Stein, Jens and Uhrin, Pavel and Sixt, Michael K and Kerjaschki, Dontscho},
  journal      = {Science},
  number       = {6382},
  pages        = {1408 -- 1411},
  publisher    = {American Association for the Advancement of Science},
  title        = {{Lymph node blood vessels provide exit routes for metastatic tumor cell dissemination in mice}},
  doi          = {10.1126/science.aal3662},
  volume       = {359},
  year         = {2018},
}

@article{437,
  abstract     = {Dendritic cells (DCs) are sentinels of the adaptive immune system that reside in peripheral organs of mammals. Upon pathogen encounter, they undergo maturation and up-regulate the chemokine receptor CCR7 that guides them along gradients of its chemokine ligands CCL19 and 21 to the next draining lymph node. There, DCs present peripherally acquired antigen to naïve T cells, thereby triggering adaptive immunity.},
  author       = {Leithner, Alexander F and Renkawitz, Jörg and De Vries, Ingrid and Hauschild, Robert and Haecker, Hans and Sixt, Michael K},
  journal      = {European Journal of Immunology},
  number       = {6},
  pages        = {1074 -- 1077},
  publisher    = {Wiley-Blackwell},
  title        = {{Fast and efficient genetic engineering of hematopoietic precursor cells for the study of dendritic cell migration}},
  doi          = {10.1002/eji.201747358},
  volume       = {48},
  year         = {2018},
}

@article{1161,
  abstract     = {Coordinated changes of cell shape are often the result of the excitable, wave-like dynamics of the actin cytoskeleton. New work shows that, in migrating cells, protrusion waves arise from mechanochemical crosstalk between adhesion sites, membrane tension and the actin protrusive machinery.},
  author       = {Müller, Jan and Sixt, Michael K},
  issn         = {09609822},
  journal      = {Current Biology},
  number       = {1},
  pages        = {R24 -- R25},
  publisher    = {Cell Press},
  title        = {{Cell migration: Making the waves}},
  doi          = {10.1016/j.cub.2016.11.035},
  volume       = {27},
  year         = {2017},
}

@article{664,
  abstract     = {Immune cells communicate using cytokine signals, but the quantitative rules of this communication aren't clear. In this issue of Immunity, Oyler-Yaniv et al. (2017) suggest that the distribution of a cytokine within a lymphatic organ is primarily governed by the local density of cells consuming it.},
  author       = {Assen, Frank P and Sixt, Michael K},
  issn         = {10747613},
  journal      = {Immunity},
  number       = {4},
  pages        = {519 -- 520},
  publisher    = {Cell Press},
  title        = {{The dynamic cytokine niche}},
  doi          = {10.1016/j.immuni.2017.04.006},
  volume       = {46},
  year         = {2017},
}

@article{668,
  abstract     = {Macrophage filopodia, finger-like membrane protrusions, were first implicated in phagocytosis more than 100 years ago, but little is still known about the involvement of these actin-dependent structures in particle clearance. Using spinning disk confocal microscopy to image filopodial dynamics in mouse resident Lifeact-EGFP macrophages, we show that filopodia, or filopodia-like structures, support pathogen clearance by multiple means. Filopodia supported the phagocytic uptake of bacterial (Escherichia coli) particles by (i) capturing along the filopodial shaft and surfing toward the cell body, the most common mode of capture; (ii) capturing via the tip followed by retraction; (iii) combinations of surfing and retraction; or (iv) sweeping actions. In addition, filopodia supported the uptake of zymosan (Saccharomyces cerevisiae) particles by (i) providing fixation, (ii) capturing at the tip and filopodia-guided actin anterograde flow with phagocytic cup formation, and (iii) the rapid growth of new protrusions. To explore the role of filopodia-inducing Cdc42, we generated myeloid-restricted Cdc42 knock-out mice. Cdc42-deficient macrophages exhibited rapid phagocytic cup kinetics, but reduced particle clearance, which could be explained by the marked rounded-up morphology of these cells. Macrophages lacking Myo10, thought to act downstream of Cdc42, had normal morphology, motility, and phagocytic cup formation, but displayed markedly reduced filopodia formation. In conclusion, live-cell imaging revealed multiple mechanisms involving macrophage filopodia in particle capture and engulfment. Cdc42 is not critical for filopodia or phagocytic cup formation, but plays a key role in driving macrophage lamellipodial spreading.},
  author       = {Horsthemke, Markus and Bachg, Anne and Groll, Katharina and Moyzio, Sven and Müther, Barbara and Hemkemeyer, Sandra and Wedlich Söldner, Roland and Sixt, Michael K and Tacke, Sebastian and Bähler, Martin and Hanley, Peter},
  issn         = {00219258},
  journal      = {Journal of Biological Chemistry},
  number       = {17},
  pages        = {7258 -- 7273},
  publisher    = {American Society for Biochemistry and Molecular Biology},
  title        = {{Multiple roles of filopodial dynamics in particle capture and phagocytosis and phenotypes of Cdc42 and Myo10 deletion}},
  doi          = {10.1074/jbc.M116.766923},
  volume       = {292},
  year         = {2017},
}

@article{672,
  abstract     = {Trafficking cells frequently transmigrate through epithelial and endothelial monolayers. How monolayers cooperate with the penetrating cells to support their transit is poorly understood. We studied dendritic cell (DC) entry into lymphatic capillaries as a model system for transendothelial migration. We find that the chemokine CCL21, which is the decisive guidance cue for intravasation, mainly localizes in the trans-Golgi network and intracellular vesicles of lymphatic endothelial cells. Upon DC transmigration, these Golgi deposits disperse and CCL21 becomes extracellularly enriched at the sites of endothelial cell-cell junctions. When we reconstitute the transmigration process in vitro, we find that secretion of CCL21-positive vesicles is triggered by a DC contact-induced calcium signal, and selective calcium chelation in lymphatic endothelium attenuates transmigration. Altogether, our data demonstrate a chemokine-mediated feedback between DCs and lymphatic endothelium, which facilitates transendothelial migration.},
  author       = {Vaahtomeri, Kari and Brown, Markus and Hauschild, Robert and De Vries, Ingrid and Leithner, Alexander F and Mehling, Matthias and Kaufmann, Walter and Sixt, Michael K},
  issn         = {22111247},
  journal      = {Cell Reports},
  number       = {5},
  pages        = {902 -- 909},
  publisher    = {Cell Press},
  title        = {{Locally triggered release of the chemokine CCL21 promotes dendritic cell transmigration across lymphatic endothelia}},
  doi          = {10.1016/j.celrep.2017.04.027},
  volume       = {19},
  year         = {2017},
}

@article{674,
  abstract     = {Navigation of cells along gradients of guidance cues is a determining step in many developmental and immunological processes. Gradients can either be soluble or immobilized to tissues as demonstrated for the haptotactic migration of dendritic cells (DCs) toward higher concentrations of immobilized chemokine CCL21. To elucidate how gradient characteristics govern cellular response patterns, we here introduce an in vitro system allowing to track migratory responses of DCs to precisely controlled immobilized gradients of CCL21. We find that haptotactic sensing depends on the absolute CCL21 concentration and local steepness of the gradient, consistent with a scenario where DC directionality is governed by the signal-to-noise ratio of CCL21 binding to the receptor CCR7. We find that the conditions for optimal DC guidance are perfectly provided by the CCL21 gradients we measure in vivo. Furthermore, we find that CCR7 signal termination by the G-protein-coupled receptor kinase 6 (GRK6) is crucial for haptotactic but dispensable for chemotactic CCL21 gradient sensing in vitro and confirm those observations in vivo. These findings suggest that stable, tissue-bound CCL21 gradients as sustainable “roads” ensure optimal guidance in vivo.},
  author       = {Schwarz, Jan and Bierbaum, Veronika and Vaahtomeri, Kari and Hauschild, Robert and Brown, Markus and De Vries, Ingrid and Leithner, Alexander F and Reversat, Anne and Merrin, Jack and Tarrant, Teresa and Bollenbach, Tobias and Sixt, Michael K},
  issn         = {09609822},
  journal      = {Current Biology},
  number       = {9},
  pages        = {1314 -- 1325},
  publisher    = {Cell Press},
  title        = {{Dendritic cells interpret haptotactic chemokine gradients in a manner governed by signal to noise ratio and dependent on GRK6}},
  doi          = {10.1016/j.cub.2017.04.004},
  volume       = {27},
  year         = {2017},
}

@article{677,
  abstract     = {The INO80 complex (INO80-C) is an evolutionarily conserved nucleosome remodeler that acts in transcription, replication, and genome stability. It is required for resistance against genotoxic agents and is involved in the repair of DNA double-strand breaks (DSBs) by homologous recombination (HR). However, the causes of the HR defect in INO80-C mutant cells are controversial. Here, we unite previous findings using a system to study HR with high spatial resolution in budding yeast. We find that INO80-C has at least two distinct functions during HR—DNA end resection and presynaptic filament formation. Importantly, the second function is linked to the histone variant H2A.Z. In the absence of H2A.Z, presynaptic filament formation and HR are restored in INO80-C-deficient mutants, suggesting that presynaptic filament formation is the crucial INO80-C function during HR.},
  author       = {Lademann, Claudio and Renkawitz, Jörg and Pfander, Boris and Jentsch, Stefan},
  issn         = {22111247},
  journal      = {Cell Reports},
  number       = {7},
  pages        = {1294 -- 1303},
  publisher    = {Cell Press},
  title        = {{The INO80 complex removes H2A.Z to promote presynaptic filament formation during homologous recombination}},
  doi          = {10.1016/j.celrep.2017.04.051},
  volume       = {19},
  year         = {2017},
}

@article{679,
  abstract     = {Protective responses against pathogens require a rapid mobilization of resting neutrophils and the timely removal of activated ones. Neutrophils are exceptionally short-lived leukocytes, yet it remains unclear whether the lifespan of pathogen-engaged neutrophils is regulated differently from that in the circulating steady-state pool. Here, we have found that under homeostatic conditions, the mRNA-destabilizing protein tristetraprolin (TTP) regulates apoptosis and the numbers of activated infiltrating murine neutrophils but not neutrophil cellularity. Activated TTP-deficient neutrophils exhibited decreased apoptosis and enhanced accumulation at the infection site. In the context of myeloid-specific deletion of Ttp, the potentiation of neutrophil deployment protected mice against lethal soft tissue infection with Streptococcus pyogenes and prevented bacterial dissemination. Neutrophil transcriptome analysis revealed that decreased apoptosis of TTP-deficient neutrophils was specifically associated with elevated expression of myeloid cell leukemia 1 (Mcl1) but not other antiapoptotic B cell leukemia/ lymphoma 2 (Bcl2) family members. Higher Mcl1 expression resulted from stabilization of Mcl1 mRNA in the absence of TTP. The low apoptosis rate of infiltrating TTP-deficient neutrophils was comparable to that of transgenic Mcl1-overexpressing neutrophils. Our study demonstrates that posttranscriptional gene regulation by TTP schedules the termination of the antimicrobial engagement of neutrophils. The balancing role of TTP comes at the cost of an increased risk of bacterial infections.},
  author       = {Ebner, Florian and Sedlyarov, Vitaly and Tasciyan, Saren and Ivin, Masa and Kratochvill, Franz and Gratz, Nina and Kenner, Lukas and Villunger, Andreas and Sixt, Michael K and Kovarik, Pavel},
  issn         = {00219738},
  journal      = {The Journal of Clinical Investigation},
  number       = {6},
  pages        = {2051 -- 2065},
  publisher    = {American Society for Clinical Investigation},
  title        = {{The RNA-binding protein tristetraprolin schedules apoptosis of pathogen-engaged neutrophils during bacterial infection}},
  doi          = {10.1172/JCI80631},
  volume       = {127},
  year         = {2017},
}

@article{694,
  abstract     = {A change regarding the extent of adhesion - hereafter referred to as adhesion plasticity - between adhesive and less-adhesive states of mammalian cells is important for their behavior. To investigate adhesion plasticity, we have selected a stable isogenic subpopulation of human MDA-MB-468 breast carcinoma cells growing in suspension. These suspension cells are unable to re-adhere to various matrices or to contract three-dimensional collagen lattices. By using transcriptome analysis, we identified the focal adhesion protein tensin3 (Tns3) as a determinant of adhesion plasticity. Tns3 is strongly reduced at mRNA and protein levels in suspension cells. Furthermore, by transiently challenging breast cancer cells to grow under non-adherent conditions markedly reduces Tns3 protein expression, which is regained upon re-adhesion. Stable knockdown of Tns3 in parental MDA-MB-468 cells results in defective adhesion, spreading and migration. Tns3-knockdown cells display impaired structure and dynamics of focal adhesion complexes as determined by immunostaining. Restoration of Tns3 protein expression in suspension cells partially rescues adhesion and focal contact composition. Our work identifies Tns3 as a crucial focal adhesion component regulated by, and functionally contributing to, the switch between adhesive and non-adhesive states in MDA-MB-468 cancer cells.},
  author       = {Veß, Astrid and Blache, Ulrich and Leitner, Laura and Kurz, Angela and Ehrenpfordt, Anja and Sixt, Michael K and Posern, Guido},
  issn         = {00219533},
  journal      = {Journal of Cell Science},
  number       = {13},
  pages        = {2172 -- 2184},
  publisher    = {Company of Biologists},
  title        = {{A dual phenotype of MDA MB 468 cancer cells reveals mutual regulation of tensin3 and adhesion plasticity}},
  doi          = {10.1242/jcs.200899},
  volume       = {130},
  year         = {2017},
}

@article{727,
  abstract     = {Actin filaments polymerizing against membranes power endocytosis, vesicular traffic, and cell motility. In vitro reconstitution studies suggest that the structure and the dynamics of actin networks respond to mechanical forces. We demonstrate that lamellipodial actin of migrating cells responds to mechanical load when membrane tension is modulated. In a steady state, migrating cell filaments assume the canonical dendritic geometry, defined by Arp2/3-generated 70° branch points. Increased tension triggers a dense network with a broadened range of angles, whereas decreased tension causes a shift to a sparse configuration dominated by filaments growing perpendicularly to the plasma membrane. We show that these responses emerge from the geometry of branched actin: when load per filament decreases, elongation speed increases and perpendicular filaments gradually outcompete others because they polymerize the shortest distance to the membrane, where they are protected from capping. This network-intrinsic geometrical adaptation mechanism tunes protrusive force in response to mechanical load.},
  author       = {Mueller, Jan and Szep, Gregory and Nemethova, Maria and De Vries, Ingrid and Lieber, Arnon and Winkler, Christoph and Kruse, Karsten and Small, John and Schmeiser, Christian and Keren, Kinneret and Hauschild, Robert and Sixt, Michael K},
  issn         = {00928674},
  journal      = {Cell},
  number       = {1},
  pages        = {188 -- 200},
  publisher    = {Cell Press},
  title        = {{Load adaptation of lamellipodial actin networks}},
  doi          = {10.1016/j.cell.2017.07.051},
  volume       = {171},
  year         = {2017},
}

@misc{5567,
  abstract     = {Immunological synapse DC-Tcells},
  author       = {Leithner, Alexander F},
  keywords     = {Immunological synapse},
  publisher    = {Institute of Science and Technology Austria},
  title        = {{Immunological synapse DC-Tcells}},
  doi          = {10.15479/AT:ISTA:71},
  year         = {2017},
}

@article{569,
  abstract     = {The actomyosin ring generates force to ingress the cytokinetic cleavage furrow in animal cells, yet its filament organization and the mechanism of contractility is not well understood. We quantified actin filament order in human cells using fluorescence polarization microscopy and found that cleavage furrow ingression initiates by contraction of an equatorial actin network with randomly oriented filaments. The network subsequently gradually reoriented actin filaments along the cell equator. This strictly depended on myosin II activity, suggesting local network reorganization by mechanical forces. Cortical laser microsurgery revealed that during cytokinesis progression, mechanical tension increased substantially along the direction of the cell equator, while the network contracted laterally along the pole-to-pole axis without a detectable increase in tension. Our data suggest that an asymmetric increase in cortical tension promotes filament reorientation along the cytokinetic cleavage furrow, which might have implications for diverse other biological processes involving actomyosin rings.},
  author       = {Spira, Felix and Cuylen Haering, Sara and Mehta, Shalin and Samwer, Matthias and Reversat, Anne and Verma, Amitabh and Oldenbourg, Rudolf and Sixt, Michael K and Gerlich, Daniel},
  issn         = {2050084X},
  journal      = {eLife},
  publisher    = {eLife Sciences Publications},
  title        = {{Cytokinesis in vertebrate cells initiates by contraction of an equatorial actomyosin network composed of randomly oriented filaments}},
  doi          = {10.7554/eLife.30867},
  volume       = {6},
  year         = {2017},
}

@article{571,
  abstract     = {Blood platelets are critical for hemostasis and thrombosis and play diverse roles during immune responses. Despite these versatile tasks in mammalian biology, their skills on a cellular level are deemed limited, mainly consisting in rolling, adhesion, and aggregate formation. Here, we identify an unappreciated asset of platelets and show that adherent platelets use adhesion receptors to mechanically probe the adhesive substrate in their local microenvironment. When actomyosin-dependent traction forces overcome substrate resistance, platelets migrate and pile up the adhesive substrate together with any bound particulate material. They use this ability to act as cellular scavengers, scanning the vascular surface for potential invaders and collecting deposited bacteria. Microbe collection by migrating platelets boosts the activity of professional phagocytes, exacerbating inflammatory tissue injury in sepsis. This assigns platelets a central role in innate immune responses and identifies them as potential targets to dampen inflammatory tissue damage in clinical scenarios of severe systemic infection. In addition to their role in thrombosis and hemostasis, platelets can also migrate to sites of infection to help trap bacteria and clear the vascular surface.},
  author       = {Gärtner, Florian R and Ahmad, Zerkah and Rosenberger, Gerhild and Fan, Shuxia and Nicolai, Leo and Busch, Benjamin and Yavuz, Gökce and Luckner, Manja and Ishikawa Ankerhold, Hellen and Hennel, Roman and Benechet, Alexandre and Lorenz, Michael and Chandraratne, Sue and Schubert, Irene and Helmer, Sebastian and Striednig, Bianca and Stark, Konstantin and Janko, Marek and Böttcher, Ralph and Verschoor, Admar and Leon, Catherine and Gachet, Christian and Gudermann, Thomas and Mederos Y Schnitzler, Michael and Pincus, Zachary and Iannacone, Matteo and Haas, Rainer and Wanner, Gerhard and Lauber, Kirsten and Sixt, Michael K and Massberg, Steffen},
  issn         = {00928674},
  journal      = {Cell Press},
  number       = {6},
  pages        = {1368 -- 1382},
  publisher    = {Cell Press},
  title        = {{Migrating platelets are mechano scavengers that collect and bundle bacteria}},
  doi          = {10.1016/j.cell.2017.11.001},
  volume       = {171},
  year         = {2017},
}

@article{659,
  abstract     = {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.},
  author       = {Kage, Frieda and Winterhoff, Moritz and Dimchev, Vanessa and Müller, Jan and Thalheim, Tobias and Freise, Anika and Brühmann, Stefan and Kollasser, Jana and Block, Jennifer and Dimchev, Georgi A and Geyer, Matthias and Schnittler, Hams and Brakebusch, Cord and Stradal, Theresia and Carlier, Marie and Sixt, Michael K and Käs, Josef and Faix, Jan and Rottner, Klemens},
  issn         = {20411723},
  journal      = {Nature Communications},
  publisher    = {Nature Publishing Group},
  title        = {{FMNL formins boost lamellipodial force generation}},
  doi          = {10.1038/ncomms14832},
  volume       = {8},
  year         = {2017},
}

@phdthesis{1129,
  abstract     = {Directed cell migration is a hallmark feature, present in almost all multi-cellular
organisms. Despite its importance, basic questions regarding force transduction
or directional sensing are still heavily investigated. Directed migration of cells
guided by immobilized guidance cues - haptotaxis - occurs in key-processes,
such as embryonic development and immunity (Middleton et al., 1997; Nguyen
et al., 2000; Thiery, 1984; Weber et al., 2013). Immobilized guidance cues
comprise adhesive ligands, such as collagen and fibronectin (Barczyk et al.,
2009), or chemokines - the main guidance cues for migratory leukocytes
(Middleton et al., 1997; Weber et al., 2013). While adhesive ligands serve as
attachment sites guiding cell migration (Carter, 1965), chemokines instruct
haptotactic migration by inducing adhesion to adhesive ligands and directional
guidance (Rot and Andrian, 2004; Schumann et al., 2010). Quantitative analysis
of the cellular response to immobilized guidance cues requires in vitro assays
that foster cell migration, offer accurate control of the immobilized cues on a
subcellular scale and in the ideal case closely reproduce in vivo conditions. The
exploration of haptotactic cell migration through design and employment of such
assays represents the main focus of this work.
Dendritic cells (DCs) are leukocytes, which after encountering danger
signals such as pathogens in peripheral organs instruct naïve T-cells and
consequently the adaptive immune response in the lymph node (Mellman and
Steinman, 2001). To reach the lymph node from the periphery, DCs follow
haptotactic gradients of the chemokine CCL21 towards lymphatic vessels
(Weber et al., 2013). Questions about how DCs interpret haptotactic CCL21
gradients have not yet been addressed. The main reason for this is the lack of
an assay that offers diverse haptotactic environments, hence allowing the study
of DC migration as a response to different signals of immobilized guidance cue.
In this work, we developed an in vitro assay that enables us to
quantitatively assess DC haptotaxis, by combining precisely controllable
chemokine photo-patterning with physically confining migration conditions. With this tool at hand, we studied the influence of CCL21 gradient properties and
concentration on DC haptotaxis. We found that haptotactic gradient sensing
depends on the absolute CCL21 concentration in combination with the local
steepness of the gradient. Our analysis suggests that the directionality of
migrating DCs is governed by the signal-to-noise ratio of CCL21 binding to its
receptor CCR7. Moreover, the haptotactic CCL21 gradient formed in vivo
provides an optimal shape for DCs to recognize haptotactic guidance cue.
By reconstitution of the CCL21 gradient in vitro we were also able to
study the influence of CCR7 signal termination on DC haptotaxis. To this end,
we used DCs lacking the G-protein coupled receptor kinase GRK6, which is
responsible for CCL21 induced CCR7 receptor phosphorylation and
desensitization (Zidar et al., 2009). We found that CCR7 desensitization by
GRK6 is crucial for maintenance of haptotactic CCL21 gradient sensing in vitro
and confirm those observations in vivo.
In the context of the organism, immobilized haptotactic guidance cues
often coincide and compete with soluble chemotactic guidance cues. During
wound healing, fibroblasts are exposed and influenced by adhesive cues and
soluble factors at the same time (Wu et al., 2012; Wynn, 2008). Similarly,
migrating DCs are exposed to both, soluble chemokines (CCL19 and truncated
CCL21) inducing chemotactic behavior as well as the immobilized CCL21. To
quantitatively assess these complex coinciding immobilized and soluble
guidance cues, we implemented our chemokine photo-patterning technique in a
microfluidic system allowing for chemotactic gradient generation. To validate
the assay, we observed DC migration in competing CCL19/CCL21
environments.
Adhesiveness guided haptotaxis has been studied intensively over the
last century. However, quantitative studies leading to conceptual models are
largely missing, again due to the lack of a precisely controllable in vitro assay. A
requirement for such an in vitro assay is that it must prevent any uncontrolled
cell adhesion. This can be accomplished by stable passivation of the surface. In
addition, controlled adhesion must be sustainable, quantifiable and dose
dependent in order to create homogenous gradients. Therefore, we developed a novel covalent photo-patterning technique satisfying all these needs. In
combination with a sustainable poly-vinyl alcohol (PVA) surface coating we
were able to generate gradients of adhesive cue to direct cell migration. This
approach allowed us to characterize the haptotactic migratory behavior of
zebrafish keratocytes in vitro. Furthermore, defined patterns of adhesive cue
allowed us to control for cell shape and growth on a subcellular scale.},
  author       = {Schwarz, Jan},
  issn         = {2663-337X},
  pages        = {178},
  publisher    = {Institute of Science and Technology Austria},
  title        = {{Quantitative analysis of haptotactic cell migration}},
  year         = {2016},
}

@article{1137,
  abstract     = {RASGRP1 is an important guanine nucleotide exchange factor and activator of the RAS-MAPK pathway following T cell antigen receptor (TCR) signaling. The consequences of RASGRP1 mutations in humans are unknown. In a patient with recurrent bacterial and viral infections, born to healthy consanguineous parents, we used homozygosity mapping and exome sequencing to identify a biallelic stop-gain variant in RASGRP1. This variant segregated perfectly with the disease and has not been reported in genetic databases. RASGRP1 deficiency was associated in T cells and B cells with decreased phosphorylation of the extracellular-signal-regulated serine kinase ERK, which was restored following expression of wild-type RASGRP1. RASGRP1 deficiency also resulted in defective proliferation, activation and motility of T cells and B cells. RASGRP1-deficient natural killer (NK) cells exhibited impaired cytotoxicity with defective granule convergence and actin accumulation. Interaction proteomics identified the dynein light chain DYNLL1 as interacting with RASGRP1, which links RASGRP1 to cytoskeletal dynamics. RASGRP1-deficient cells showed decreased activation of the GTPase RhoA. Treatment with lenalidomide increased RhoA activity and reversed the migration and activation defects of RASGRP1-deficient lymphocytes.},
  author       = {Salzer, Elisabeth and Çaǧdaş, Deniz and Hons, Miroslav and Mace, Emily and Garncarz, Wojciech and Petronczki, Oezlem and Platzer, René and Pfajfer, Laurène and Bilic, Ivan and Ban, Sol and Willmann, Katharina and Mukherjee, Malini and Supper, Verena and Hsu, Hsiangting and Banerjee, Pinaki and Sinha, Papiya and Mcclanahan, Fabienne and Zlabinger, Gerhard and Pickl, Winfried and Gribben, John and Stockinger, Hannes and Bennett, Keiryn and Huppa, Johannes and Dupré, Loï̈C and Sanal, Özden and Jäger, Ulrich and Sixt, Michael K and Tezcan, Ilhan and Orange, Jordan and Boztug, Kaan},
  journal      = {Nature Immunology},
  number       = {12},
  pages        = {1352 -- 1360},
  publisher    = {Nature Publishing Group},
  title        = {{RASGRP1 deficiency causes immunodeficiency with impaired cytoskeletal dynamics}},
  doi          = {10.1038/ni.3575},
  volume       = {17},
  year         = {2016},
}