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1,171 results on '"Spatz, Joachim P."'

152. Cyclic stretch increases splicing noise rate in cultured human fibroblasts

Author

Spatz Joachim P, Lamla Markus, Deibler Martin, Striegl Britta, Mellert Kevin, Uhl Michael, Kemkemer Ralf, and Kaufmann Dieter

Subjects
Medicine, Biology (General), QH301-705.5, Science (General), Q1-390
Abstract

Abstract Background Mechanical forces are known to alter the expression of genes, but it has so far not been reported whether they may influence the fidelity of nucleus-based processes. One experimental approach permitting to address this question is the application of cyclic stretch to cultured human fibroblasts. As a marker for the precision of nucleus-based processes, the number of errors that occur during co-transcriptional splicing can then be measured. This so-called splicing noise is found at low frequency in pre-mRNA splicing. Findings The amount of splicing noise was measured by RT-qPCR of seven exon skips from the test genes AATF, MAP3K11, NF1, PCGF2, POLR2A and RABAC1. In cells treated by altered uniaxial cyclic stretching for 18 h, a uniform and significant increase of splicing noise was found for all detectable exon skips. Conclusion Our data demonstrate that application of cyclic stretch to cultured fibroblasts correlates with a reduced transcriptional fidelity caused by increasing splicing noise.

Published
2011
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153. Cell adhesion to agrin presented as a nanopatterned substrate is consistent with an interaction with the extracellular matrix and not transmembrane adhesion molecules

Author

Wolfram Tobias, Spatz Joachim P, and Burgess Robert W

Subjects
Cytology, QH573-671
Abstract

Abstract Background Molecular spacing is important for cell adhesion in a number of ways, ranging from the ordered arrangement of matrix polymers extracellularly, to steric hindrance of adhesion/signaling complexes intracellularly. This has been demonstrated using nanopatterned RGD peptides, a canonical extracellular matrix ligand for integrin interactions. Cell adhesion was greatly reduced when the RGD-coated nanoparticles were separated by more than 60 nm, indicating a sharp spacing-dependent threshold for this form of cell adhesion. Results Here we show a similar dependence of cell adhesion on the spacing of agrin, a protein that exists as both a secreted, matrix-bound form and a type-2 transmembrane form in vivo. Agrin was presented as a substrate for cell adhesion assays by anchoring recombinant protein to gold nanoparticles that were arrayed at tunable distances onto glass coverslips. Cells adhered well to nanopatterned agrin, and when presented as uniformly coated substrates, adhesion to agrin was comparable to other well-studied adhesion molecules, including N-Cadherin. Adhesion of both mouse primary cortical neurons and rat B35 neuroblastoma cells showed a spacing-dependent threshold, with a sharp drop in adhesion when the space between agrin-coated nanoparticles increased from 60 to 90 nm. In contrast, adhesion to N-Cadherin decreased gradually over the entire range of distances tested (uniform, 30, 60, 90, and 160 nm). The spacing of the agrin nanopattern also influenced cell motility, and peptide competition suggested adhesion was partially integrin dependent. Finally, differences in cell adhesion to C-terminal agrin fragments of different lengths were detected using nanopatterned substrates, and these differences were not evident using uniformly coated substrates. Conclusion These results suggest nanopatterned substrates may provide a physiological presentation of adhesive substrates, and are consistent with cells adhering to agrin through a mechanism that more closely resembles an interaction with the extracellular matrix than a transmembrane adhesion molecule.

Published
2008
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155. Cell–Extracellular Matrix Mechanobiology: Forceful Tools and Emerging Needs for Basic and Translational Research

Author

Massachusetts Institute of Technology. Department of Biological Engineering, Massachusetts Institute of Technology. Department of Materials Science and Engineering, Massachusetts Institute of Technology. Department of Mechanical Engineering, Van Vliet, Krystyn J, Kamm, Roger Dale, Holle, Andrew W., Young, Jennifer L., Discher, Dennis, Janmey, Paul, Spatz, Joachim P., Saif, Taher, Massachusetts Institute of Technology. Department of Biological Engineering, Massachusetts Institute of Technology. Department of Materials Science and Engineering, Massachusetts Institute of Technology. Department of Mechanical Engineering, Van Vliet, Krystyn J, Kamm, Roger Dale, Holle, Andrew W., Young, Jennifer L., Discher, Dennis, Janmey, Paul, Spatz, Joachim P., and Saif, Taher

Abstract

Extracellular biophysical cues have a profound influence on a wide range of cell behaviors, including growth, motility, differentiation, apoptosis, gene expression, adhesion, and signal transduction. Cells not only respond to definitively mechanical cues from the extracellular matrix (ECM) but can also sometimes alter the mechanical properties of the matrix and hence influence subsequent matrix-based cues in both physiological and pathological processes. Interactions between cells and materials in vitro can modify cell phenotype and ECM structure, whether intentionally or inadvertently. Interactions between cell and matrix mechanics in vivo are of particular importance in a wide variety of disorders, including cancer, central nervous system injury, fibrotic diseases, and myocardial infarction. Both the in vitro and in vivo effects of this coupling between mechanics and biology hold important implications for clinical applications., National Science Foundation (U.S.)

Published
2018

156. Investigating the inner structure of focal adhesions with single-molecule localization microscopy

Author

Aleksandra Radenovic, Daniel Sage, Hendrik Deschout, Ilia Platzman, Spatz, Joachim P., and Lely Feletti

Subjects
Biological Physics (physics.bio-ph), FOS: Physical sciences, Physics - Biological Physics
Abstract

Cells rely on focal adhesions (FAs) to carry out a variety of important tasks, including motion, environmental sensing, and adhesion to the extracellular matrix. Although attaining a fundamental characterization of FAs is a compelling goal, their extensive complexity and small size, which can be below the diffraction limit, have hindered a full understanding. In this study we have used single-molecule localization microscopy (SMLM) to investigate integrin $\beta$3 and paxillin in rat embryonic fibroblasts growing on two different extracellular matrix-representing substrates (i.e. fibronectin-coated substrates and specifically bio-functionalized nano-patterned substrates). To quantify the substructure of FAs, we developed a method based on expectation maximization of a Gaussian mixture that accounts for localization uncertainty and background. Analysis of our SMLM data indicates that the structures within FAs, characterized as a Gaussian mixture, typically have areas between 0.01 and 1 $\mu$m$^2$, contain 10 to 100 localizations, and can exhibit substantial eccentricity. Our approach based on SMLM opens new avenues for studying structural and functional biology of molecular assemblies that display substantial varieties in size, shape, and density.

Published
2017

157. Vascularized 3D Human Skin Models in the Forefront of Dermatological Research

Author

Rimal, Rahul, Muduli, Saradaprasan, Desai, Prachi, Marquez, Andrea Bonnin, Möller, Martin, Platzman, Ilia, Spatz, Joachim, and Singh, Smriti

Abstract

In vitro engineered skin models are emerging as an alternative platform to reduce and replace animal testing in dermatological research. Despite the progress made in recent years, considerable challenges still exist for the inclusion of diverse cell types within skin models. Blood vessels, in particular, are essential in maintaining tissue homeostasis and are one of many primary contributors to skin disease inception and progression. Substantial efforts in the past have allowed the successful fabrication of vascularized skin models that are currently utilized for disease modeling and drugs/cosmetics testing. This review first discusses the need for vascularization within tissue‐engineered skin models, highlighting their role in skin grafting and disease pathophysiology. Second, the review spotlights the milestones and recent progress in the fabrication and utilization of vascularized skin models. Additionally, advances including the use of bioreactors, organ‐on‐a‐chip devices, and organoid systems are briefly explored. Finally, the challenges and future outlook for vascularized skin models are addressed. Vascularized human skin models are an emerging alternate platform for drug testing. The need for incorporation of blood vessels within in vitro models emerges from the fact that skin diseases and the ensuing therapy influence vessel morphology, functionality, and growth. Use of bioreactors, biofabrication techniques, and synthetic cell‐mimics are predicted to pave a pathway for more advanced vascularized skin models.

Published
2024
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158. Impaired integrin α5/β1‐mediated hepatocyte growth factor release by stellate cells of the aged liver.

Author

Rohn, Friederike, Kordes, Claus, Buschmann, Tobias, Reichert, Doreen, Wammers, Marianne, Poschmann, Gereon, Stühler, Kai, Benk, Amelie S., Geiger, Fania, Spatz, Joachim P., and Häussinger, Dieter

Subjects
HEPATOCYTE growth factor, KUPFFER cells, INTEGRINS, LIVER cells, BLOOD flow, LIVER regeneration
Abstract

Hepatic blood flow and sinusoidal endothelial fenestration decrease during aging. Consequently, fluid mechanical forces are reduced in the space of Disse where hepatic stellate cells (HSC) have their niche. We provide evidence that integrin α5/β1 is an important mechanosensor in HSC involved in shear stress‐induced release of hepatocyte growth factor (HGF), an essential inductor of liver regeneration which is impaired during aging. The expression of the integrin subunits α5 and β1 decreases in liver and HSC from aged rats. CRISPR/Cas9‐mediated integrin α5 and β1 knockouts in isolated HSC lead to lowered HGF release and impaired cellular adhesion. Fluid mechanical forces increase integrin α5 and laminin gene expression whereas integrin β1 remains unaffected. In the aged liver, laminin β2 and γ1 protein chains as components of laminin‐521 are lowered. The integrin α5 knockout in HSC reduces laminin expression via mechanosensory mechanisms. Culture of HSC on nanostructured surfaces functionalized with laminin‐521 enhances Hgf expression in HSC, demonstrating that these ECM proteins are critically involved in HSC function. During aging, HSC acquire a senescence‐associated secretory phenotype and lower their growth factor expression essential for tissue repair. Our findings suggest that impaired mechanosensing via integrin α5/β1 in HSC contributes to age‐related reduction of ECM and HGF release that could affect liver regeneration. [ABSTRACT FROM AUTHOR]

Published
2020
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163. Tailored environments to study motile cells and pathogens

Author

Muthinja, Julianne Mendi, primary, Ripp, Johanna, additional, Krüger, Timothy, additional, Imle, Andrea, additional, Haraszti, Tamás, additional, Fackler, Oliver T., additional, Spatz, Joachim P., additional, Engstler, Markus, additional, and Frischknecht, Friedrich, additional

Published
2018
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170. Membrane-grafted hyaluronan films: A well-defined model system of glycoconjugate cell coats

Author

Richter, Ralf P., Hock, Kai K., Burkhartsmeyer, Jeffrey, Boehm, Heike, Bingen, Pit, Guoliang Wang, Steinmetz, Nicole F., Evans, David J., and Spatz, Joachim P.

Subjects
Hyaluronic acid -- Structure, Lipid membranes -- Mechanical properties, Dielectric films -- Structure, Dielectric films -- Mechanical properties, Thin films -- Structure, Thin films -- Mechanical properties, Chemistry
Abstract

A simple method is presented to create hyaluronan films that are well-defined in their molecular attachment to the substrate, a supported lipid bilayer (SLB). Surface-sensitive techniques are used to investigate the films' thickness, grafting density, permeability and mechanical properties.

Published
2007

172. Sequential bottom-up assembly of mechanically stabilized synthetic cells by microfluidics

Author

Weiss, Marian, primary, Frohnmayer, Johannes Patrick, additional, Benk, Lucia Theresa, additional, Haller, Barbara, additional, Janiesch, Jan-Willi, additional, Heitkamp, Thomas, additional, Börsch, Michael, additional, Lira, Rafael B., additional, Dimova, Rumiana, additional, Lipowsky, Reinhard, additional, Bodenschatz, Eberhard, additional, Baret, Jean-Christophe, additional, Vidakovic-Koch, Tanja, additional, Sundmacher, Kai, additional, Platzman, Ilia, additional, and Spatz, Joachim P., additional

Published
2017
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178. A unique profilin-actin interface is important for malaria parasite motility

Author

Moreau, Catherine A., primary, Bhargav, Saligram P., additional, Kumar, Hirdesh, additional, Quadt, Katharina A., additional, Piirainen, Henni, additional, Strauss, Léanne, additional, Kehrer, Jessica, additional, Streichfuss, Martin, additional, Spatz, Joachim P., additional, Wade, Rebecca C., additional, Kursula, Inari, additional, and Frischknecht, Friedrich, additional

Published
2017
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181. Biomimetic Optical Nanostructures

Author

Weishaupt, Klaus, Diao, Zhaolu, Brunner, Robert, and Spatz, Joachim

Abstract

Optical nanostructures have evolved successfully in nature over millions of years. For example, such nanostructures are found on the compound eyes of night active insects. These “moth‐eye” structures offer extraordinary anti‐reflective (AR) properties and therefore allow the insects to hide from their predators. This concept has been transferred to technical applications and enables artificial AR characteristics on high‐end optical elements with performance advantages not possible with classical layer‐based AR coatings. An appropriate manufacturing technology combines self‐organization of nano‐particles with a reactive ion‐etching process.

Published
2020
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182. Reconceptualizing Fluorescence Correlation Spectroscopy for Monitoring and Analyzing Periodically Passing Objects

Author

Zamir, Eli, Frey, Christoph, Weiss, Marian, Antona, Silvia, Frohnmayer, Johannes P., Janiesch, Jan-Willi, Platzman, Ilia, and Spatz, Joachim P.

Abstract

Fluorescence correlation spectroscopy (FCS) is a sensitive technique commonly applied for studying the dynamics of nanoscale-labeled objects in solution. Current analysis of FCS data is largely based on the assumption that the labeled objects are stochastically displaced due to Brownian motion. However, this assumption is often invalid for microscale objects, since the motion of these objects is dominated by Stokes drag and settling or rising effects, rather than stochastic Brownian motion. To utilize the power of FCS for systems with nonstochastic displacements of objects, the collection and analysis of FCS data have to be reconceptualized. Here, we extended the applicability of FCS for the detection and analysis of periodically passing objects. Toward this end, we implemented droplet-based microfluidics, in which monodispersed droplets containing fluorescent marker are flowing equally spaced within microchannels. We show by simulations and experiments that FCS can sensitively quantify the flow-rates, variability, and content of rapidly passing droplets. This information can be derived at high temporal resolution, based on the intensity fluctuations generated by only 5–10 passing droplets. Moreover, by utilizing the periodicity of the flowing droplets for noise reduction by averaging, FCS can monitor accurately the droplets flow even if their fluorescence intensity is negligible. Hence, extending FCS for periodically passing objects converts it into a powerful analytical tool for high-throughput droplet-based microfluidics. Moreover, based on the principles described here, FCS can be straightforwardly applied for a variety of systems in which the passing of objects is periodic rather than stochastic.

Published
2024
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183. Designed Ankyrin Repeat Proteins as Actin Labels of Distinct Cytoskeletal Structures in Living Cells

Author

Ivanova, Julia R., Benk, Amelie S., Schaefer, Jonas V., Dreier, Birgit, Hermann, Leon O., Plückthun, Andreas, Missirlis, Dimitris, and Spatz, Joachim P.

Abstract

The orchestrated assembly of actin and actin-binding proteins into cytoskeletal structures coordinates cell morphology changes during migration, cytokinesis, and adaptation to external stimuli. The accurate and unbiased visualization of the diverse actin assemblies within cells is an ongoing challenge. We describe here the identification and use of designed ankyrin repeat proteins (DARPins) as synthetic actin binders. Actin-binding DARPins were identified through ribosome display and validated biochemically. When introduced or expressed inside living cells, fluorescently labeled DARPins accumulated at actin filaments, validated through phalloidin colocalization on fixed cells. Nevertheless, different DARPins displayed different actin labeling patterns: some DARPins labeled efficiently dynamic structures, such as filopodia, lamellipodia, and blebs, while others accumulated primarily in stress fibers. This differential intracellular distribution correlated with DARPin–actin binding kinetics, as measured by fluorescence recovery after photobleaching experiments. Moreover, the rapid arrest of actin dynamics induced by pharmacological treatment led to the fast relocalization of DARPins. Our data support the hypothesis that the localization of actin probes depends on the inherent dynamic movement of the actin cytoskeleton. Compared to the widely used LifeAct probe, one DARPin exhibited enhanced signal-to-background ratio while retaining a similar ability to label stress fibers. In summary, we propose DARPins as promising actin-binding proteins for labeling or manipulation in living cells.

Published
2024
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184. Synthese und Evaluierung bioaktiver Verbindungen für Integrine und den CXCR4-Rezeptor

Author

Kessler, Horst (Prof. Dr. Dr. h.c.), Spatz, Joachim P. (Prof. Dr.), Wester, Hans-Jürgen (Prof. Dr.), Groll, Michael (Prof. Dr.), Kapp, Tobias Gustav, Kessler, Horst (Prof. Dr. Dr. h.c.), Spatz, Joachim P. (Prof. Dr.), Wester, Hans-Jürgen (Prof. Dr.), Groll, Michael (Prof. Dr.), and Kapp, Tobias Gustav

Abstract

Literaturbekannte Integrinliganden wurden erstmalig in einem einheitlichen in-vitro-Testsystem auf deren Bindungsaffinität gegenüber sechs RGD-bindenden Integrinen evaluiert. Ein peptidomimetischer Integrinligand wurde funktionalisiert und ein cyclisches Pentapeptid durch einen N-Methylscan optimiert und in der molekularen Bildgebung eingesetzt. Durch die Modifizierung der Guanidiniumgruppe von Arginin in Integrinliganden konnte die Subtypselektivität stark beeinflusst werden. Des weiteren wurde eineSynthesemethode zur Funktionalisierung der Guanidiniumgruppe bei der Peptidfestphasensynthese entwickelt, damit konnten CXCR4-Liganden nahezu ohne Affinitätsverluste funktionalisiert werden. Außerdem wurde das Adhäsionsverhalten von humanen mesenchymalen Stammzeller auf einer mit CXCR4-Liganden beschichteten Titanoberfläche untersucht., Several well known integrin ligands were, for the first time, homogenously evaluated in an in-vitro testing system for their binding affinity to six different RGD-binding integrin subtyptes. A peptidomimetic integrin ligand was optimized and functionalized, a cyclic pentapeptide ligand optimized through a N-methylscan and used for molecular imaging. Different modifications of the guanidine group of arginine in integrin ligands strongly influenced their subtype selectivity profiles. Furthermore, a method for the functionalization via the guanidine group was developed to be used during solid phase peptide synthesis. Using this protocol, CXCR4 ligands could be functionalized almost without influencing the binding affinity. Moreover, the adhesion of human mesenchumal stem cells on titan surfaces coated with CXCR4 ligands was investigated.

Published
2016

185. Polarizing cytoskeletal tension to induce leader cell formation during collective cell migration

Author

Rausch, Sebastian, Das, Tamal, Soiné, Jérôme RD, Hofmann, Tobias W, Boehm, Christian HJ, Schwarz, Ulrich S, Boehm, Heike, and Spatz, Joachim P

Subjects
Materials Science(all), Chemistry(all), Biochemistry, Genetics and Molecular Biology(all), Physics and Astronomy(all)
Abstract

The collective migration of cells is fundamental to epithelial biology. One of the hallmarks of collective behavior in migrating cohesive epithelial cell sheets is the emergence of so called leader cells. These cells exhibit a distinct morphology with a large and highly active lamellipodium. Although it is generally accepted that they play a crucial part in collective migration, the biophysical factors that regulate their formation remain unknown.Here we show that a geometry-based cue like local variation of curvature of the collective's perimeter is capable of triggering leader cell formation and promoting enhanced motility at defined positions. Remarkably, the extent of this effect scales with the magnitude of the curvature.Cytoskeletal tension was found to be important for geometry induced leader cell formation, as cells treated with tension reducing agents appeared less sensitive to local curvature variation. Accordingly, traction force microscopy revealed an increased level of shear stress at highly curved positions even before the cell migration had actually started, indicating the presence of a collective polarization induced by the geometry of the confinement.Together our findings suggest that high curvature leads to locally increased stress accumulation, mediated via cell-substrate interaction as well as via cytoskeleton tension. The stress accumulation in turn enhances the probability of leader cell formation as well as cell motility. This work defines the importance of geometric cue such as local curvature in the collective migration dynamics of epithelial cells and thus shows implications for the biophysical regulation of epithelium during wound healing, embryonic development, and oncogenesis.

Published
2013

190. Selective binding and lateral clustering ofα5β1 andαvβ3 integrins: Unraveling the spatial requirements for cell spreading and focal adhesion assembly

Author

Schaufler, Viktoria, primary, Czichos-Medda, Helmi, additional, Hirschfeld-Warnecken, Vera, additional, Neubauer, Stefanie, additional, Rechenmacher, Florian, additional, Medda, Rebecca, additional, Kessler, Horst, additional, Geiger, Benjamin, additional, Spatz, Joachim P., additional, and Cavalcanti-Adam, E. Ada, additional

Published
2016
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200. T cell activation is determined by the number of presented antigens

Author

Deeg, Janosch, Axmann, Markus, Matic, Jovana, Liapis, Anastasia, Depoil, David, Afrose, Jehan, Curado, Silvia, Dustin, Michael L., and Spatz, Joachim P.

Subjects
chemical and pharmacologic phenomena
Abstract

Antigen recognition is a key event during T cell activation. Here, we introduce nanopatterned antigen arrays that mimic the antigen presenting cell surface during T cell activation. The assessment of activation related events revealed the requirement of a minimal density of 90-140 stimulating major histocompatibility complex class II proteins (pMHC) molecules per μm(2). We demonstrate that these substrates induce T cell responses in a pMHC dose-dependent manner and that the number of presented pMHCs dominates over local pMHC density.

Published
2013

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