Members

Overview

Head SPP funded collaborator SPP associated collaborator Institute
Dr. Anne-Kathrin Classen Ramya Balaji   Biozentrum Martinsried
Prof. Dr. Christian Dahmann     Institute of Genetics, Dresden
Prof. Dr. Suzanne Eaton Dr. Natalie Dye, Franz Gruber   Max Planck Institute of Molecular Cell Biology and Genetics, Dresden
Prof. Dr. Klaus Ebnet Christian Hartmann   Institute of Medical Biochemistry, Münster
Dr. Carsten Grashoff Anna-Lena Cost   Max Planck Institute of Biochemistry, Martinsried
Prof. Dr. Frauke Gräter Dr. Csaba Daday, Dr. Katra Kolsek   Heidelberg Institute for Theoretical Studies, Heidelberg
Prof. Dr. Stephan Grill, Prof. Dr. Elisabeth Knust Dr. David Flores-Benitez   Biotec, Dresden
Max Planck Institute of Molecular Cell Biology and Genetics, Dresden
Prof. Dr. Robert Grosse Dr. Katharina Grikscheit
Hanna Grobe
  Institute of Pharmacology, Universität Marburg
Prof. Dr. Jörg Großhans, Prof. Dr. Fred Wolf Deqing Kong, Dr. Zhiyi Lv, Prachi Richa, Adem Saglam   Institute of Developmental Biochemistry, Göttingen
Max-Planck-Institut für Dynamik und Selbstorganisation, Göttingen
Prof. Dr. Mechthild Hatzfeld Katrin Rietscher, Assoc. Dr. René Keil, Institute of Molecular Medicine, Halle
Dr. Sandra Iden Martim Gomes Assoc. Michael Saynisch, CECAD, Köln
Prof. Dr. Andreas Janshoff Susanne Karsch   Institute of Physical Chemistry, Göttingen
Prof. Dr. Virginie Lecaudey Christine Molenda, David Kleinhans   Frankfurt
Prof. Dr. Rudolf Leube Dr. Marcin Moch   MOCA, Aachen
Prof. Dr. Thomas M. Magin Dr. Fanny Buechau, Aileen Wingenfeld Assoc. Dr. Jamal Bouameur, Assoc. Alyssa Vetter, Assoc. Andrea Scheffschick, Assoc. Melanie Homberg, Assoc. Kristin Jahn, Institute of Biology, Leipzig
Dr. Maja Matis Amrita Singh   Institute of Cell Biology, Münster
Prof. Dr. Rudolf Merkel Dave Ahrens, Lena Ramms   Institute of Complex Systems, Jülich
Prof. Dr. Carien Niessen Placido Pereira,   CECAD, Köln
PD Dr. Nicolas Schlegel, Prof. Dr. Jens Waschke Hanna Ungewiss   Klinik und Poliklinik für Allgemein-, Viszeral-, Gefäß-, und Kinderchirurgie, Würzburg
Institute of Anatomy and Cell Biology, München
PD Dr. Pavel Strnad Annika Gross Assoc. Prof. Dr. Peter Boor, Dr. Sonja Djudjaj Department of Internal Medicine III, Aachen
Institute of Pathology, Aachen
Associate Prof. Dr. med. Volker Spindler     Institute of Anatomy and Cell Biology

A-K Classen: Cellular junctions as force anchors during epithelial shape transitions

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Principal investigator

Dr. Anne-Kathrin Classen

Albert Ludwigs University of Freiburg
Center for Biological Systems Analysis
 

Habsburger Strasse 49
79104 Freiburg im Breisgau

 

anne.classen(a)zbsa.uni-freiburg.de

Homepage

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SPP funded collaborator

Ramya Balaji

Albert Ludwigs University of Freiburg
Center for Biological Systems Analysis
 

Habsburger Strasse 49
79104 Freiburg im Breisgau

 

ramya.balaji(at)mail.zbsa.uni-freiburg.de

Summary

Epithelial tissues cover organ surfaces throughout our body and fulfill crucial functions such as protection, secretion and absorption. The diversity of epithelial tissue shapes is a consequence of cytoskeleton dynamics, cell-cell adhesion and cell-matrix interactions. The aim of this proposal is to specifically explore cell biological, genetic and biomechanical mechanisms that promote morphogenesis of squamous, cuboidal and columnar cell shapes.
We investigate the hypothesis that cell-intrinsic and cell-extrinsic forces are being integrated at the level of cell-cell adhesion to allow for cuboidal-to-columnar and cuboidal-to-squamous cell shape transitions in the Drosophila follicle cell epithelium. The richness in cell shapes, a simple architecture and the easy microscopic tractability makes the follicle cell epithelium an ideal model system for this study. We propose to merge classical cell biological and genetic analysis with a quantitative framework for a 3D mathematical modeling of the cellular forces during shape transitions. Our work will provide novel interdisciplinary insights into a little understood, but profoundly fundamental aspect of epithelial morphogenesis.

Expertise

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C. Dahmann: Interplay between mechanical tension and cytoskeletal organization in cell separation at compartment boundaries in Drosophila

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Principal investigator

Prof. Dr. Christian Dahmann

Technische Universität Dresden
Institute of Genetics
 

 
01062 Dresden

Tel: +49 (0)(351)-463-39537 (office)

christian.dahmann(at)tu-dresden.de

Homepage

Summary

The interplay between mechanical tension and cytoskeletal organization is important for tissue development and homeostasis. Mechanical forces acting on cell junctions can, for example, result in the assembly of cortical F-actin and the recruitment of Myosin motor proteins to the cell cortex. A hallmark of many developing tissues is the subdivision into immiscible groups of cells with distinct functions and fates termed compartments. Compartmentalization is important for the stable positioning of signaling centers within tissues and thus for growth and patterning. The separation of cells from neighboring compartments at boundaries is challenged by cell intercalations caused by cell proliferation and tissue morphogenesis. Recent data show a key role for a local increase in mechanical tension at cell junctions along compartment boundaries in keeping cells from neighboring compartments separated. Local increases in mechanical tension bias cell rearrangements during cell intercalations to maintain straight boundaries and to prevent mixing between cells from neighboring compartments.

Mechanical tension at cell junctions results from actomyosin-based contractile forces and cell adhesion. Local increases in mechanical tension at compartment boundaries correlate with increases in F-actin and non-muscle Myosin II at cell junctions. It has been proposed, but not tested, that F-actin and Myosin II form a multi-cellular cable along compartment boundaries instrumental for separating cells from neighboring compartments. Moreover, whether mechanical tension influences cytoskeletal organization of cells at compartment boundaries and whether such a cytoskeletal reorganization feeds back on mechanical tension has not been addressed. Here, using the Drosophila abdominal epidermis as a model system, we will address these questions. We expect that our results will provide novel insights into the interplay between mechanical forces and biochemical signals involved in organizing cells into functional tissues.

Expertise

Our lab combines genetic, cell biological, and biophysical approaches to understand how cells form functional epithelial tissues. In particular, we use live imaging followed by quantitative image analysis to investigate cellular dynamics in wild-type and mutant wing imaginal discs and the abdominal epidermis of Drosophila. Moreover, laser ablation of cell junctions is used to measure mechanical forces in epithelia.

S. Eaton: ...

Prof. Dr. Suzanne Eaton

Max Planck Institute of Molecular Cell Biology and Genetics
 
 

Pfotenhauerstr. 108
01307 Dresden

Tel: +49 (0)351-210-2526 (office)

eaton(at)mpi-cbg.de

Homepage

Dr. Natalie Dye

Max Planck Institute of Molecular Cell Biology and Genetics
 
 

Pfotenhauerstr. 108
01307 Dresden

Tel: +49 (0)351-210-2806 (office)

dye(at)mpi-cbg.de

Franz Gruber

Max Planck Institute of Molecular Cell Biology and Genetics
 
 

Pfotenhauerstr. 108
01307 Dresden

Tel: +49 (0)351-210-2451 (office)

gruber(at)mpi-cbg.de

Summary

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Expertise

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K. Ebnet: Role of JAM family adhesion molecules in epithelial cell extrusion

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Principal investigator

Prof. Dr. Klaus Ebnet

Center of Molecular Biology of Inflammation
Institute of Medical Biochemistry
 

Von-Esmarch-Straße 56
48149 Münster

Tel: +49 (0)251-83-52127 (office)

ebnetk(at)uni-muenster.de

Homepage

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SPP funded collaborator

Christian Hartmann

Center of Molecular Biology of Inflammation
Institute of Medical Biochemistry
 

Von-Esmarch-Straße 56
48149 Münster

Tel: +49 (0)+-49-251-8352108 (office)

c_hart11(at)uni-muenster.de

Summary

Epithelial tissues line the body and organ surfaces and form the boundaries between the internal and external environment of multicellular organisms. Certain epithelia such as the stratified epithelium of the skin or the simple epithelia lining the luminal surface of the gut or of the lung are constantly exposed to environmental factors of physical, chemical, or biological nature (e.g. UV-light, toxins, or pathogens), imposing the risk of alterations in the genome which could ultimately lead to cancerous growth. One mechanism that has probably evolved to prevent the accumulation of genome alterations during aging is to replace aged cells by new cells. During this process called Cell Turnover, terminally differentiated cells are replaced by cells newly formed from adult stem cells. The rate of cell turnover is particularly high in epithelia facing the exterior, such as those of the skin or those lining the small intestine. Cell turnover is achieved by a process called Cell Extrusion, during which cells - either living or apoptotic - are expelled from the epithelial layer. Cell extrusion must be a tightly regulated process since failure of extrusion, or extrusion in the wrong (i.e. basal) direction, could lead to cancerous growth and metastasis. The molecular mechanisms that regulate cell extrusion are poorly understood. It is very likely that cell adhesion molecules at the junctions between the extruded cell and its neighbours are directly involved in cell extrusion. Our interest is focused on a family of cell adhesion molecules, the Junctional Adhesion Molecules (JAMs). Several JAMs are localized at epithelial cell-cell junctions, and some JAMs are enriched at the tight junctions. In previous studies we have identified a diverse range of functions for JAMs, for example a role in the regulation of cell-cell contact and tight junction formation, the regulation of cell polarity, and the regulation of mitotic spindle orientation. In this project, we investigate the role of JAMs during epithelial cell extrusion. The specific objectives of this proposal are: (1) identify JAM family members which regulate epithelial cell extrusion; (2) identify binding partners for JAMs through which JAMs could regulate epithelial cell extrusion; (3) address a role for JAMs in the regulation of actomyosin contractility during epithelial cell extrusion.

Expertise

Mechanisms of cell-cell adhesion; cell adhesion-regulated processes such as cell contact formation and cellular polarization; cell polarity; protein-protein interactions, 3D culture, Live cell imaging of cultured cells

C. Grashoff: Molecular Force Measurements in Epithelial Junctions

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Principal investigator

Dr. Carsten Grashoff

Institut für Molekulare Zellbiologie
 
Quantitative Zellbiologie

Schlossplatz 5
48149 Münster

Tel: +49 (0)251-83-23841 (office)

grashoff(at)uni-muenster.de

Homepage

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SPP funded collaborator

Anna-Lena Cost

Max-Planck-Institute of Biochemistry
 
Group of Molecular Mechanotransduction

Am Klopferspitz 18
82152 Martinsried

Tel: +49 (0)89-8578-2417 (office)

alcost(at)biochem.mpg.de

Summary

The ability of epithelia to bear, sense and respond to mechanical forces is central to a wide range of biological processe. The epidermis of our skin, for instance, is constantly subject to mechanical stimulation and frequently required to adjust to its mechanical environment. It does so by the use of specialized adhesion structures ‒ hemidesmosomes, desmosomes and adherens junctions ‒ that bear mechanical loads and allow coordinated mechanoresponses. Even though it has been recognized decades ago that these junctions are critical for the mechanical integrity of epithelia, our understanding of how forces are processed on the molecular level remains fragmentary because we have been lacking suitable techniques to investigate intracellular force transduction with sufficient spatiotemporal resolution. Therefore, we have further developed our FRET-based tension sensor technique that allows the visualization and measurement of mechanical forces across individual proteins in cells. We will apply these tools to investigate force transduction across epithelial junctions, which will be the basis for a more detailed analysis in later funding periods.

We expect that the biosensors generated in the course of this study will be useful to other research groups of the priority program and of general interest to epithelial cell biologists.

Expertise

Molecular force measurements by FRET-based tension sensors

Mechano-sensing mechanisms in the desmosome from molecular simulations

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Principal investigator

Prof. Dr. Frauke Gräter

Heidelberg Institute for Theoretical Studies
 
 

Schloß-Wolfsbrunnenweg 35
69118 Heidelberg

Tel: +49 (0)6221-533267 (office)

frauke.graeter(at)h-its.org

Homepage

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SPP funded collaborator

Dr. Csaba Daday

Heidelberg Institute for Theoretical Studies
 
 

Schloß-Wolfsbrunnenweg 35
69118 Heidelberg

 

csaba.daday(at)h-its.org

Summary

Desmosomes integrate mechanical stress into biochemical networks at the cell-cell interface. How desmosomal proteins respond to mechanical force such that their structure and function is altered is currently unknown. Our objective is to characterize the mechanical properties and putative force-sensing function of a major desmosomal component, desmoplakin. The spectrin-repeat fragment of desmoplakin features an SH3 domain with a peculiar and cryptic binding site and currently unknown function. The spectrin-SH3 interaction is a hot spot for mutations involved in skin and cardiac diseases, underlining its pivotal role in desmoplakin function. We will put two putative roles of the SH3 domain, and thereby of desmoplakin, to test, namely a mechanically stabilizing function and a mechano-sensing function, which might not exclude each other. To this end, we will perform Molecular Dynamics simulations to monitor the spectrin/SH3 fragment and larger constructs of desmoplakin under tensile forces.
The simulations will allow us to quantify the extent to which the SH3 domain, when being subjected to mechanical force, can stabilize the spectrin repeats against unfolding and/or can expose its binding site for partners involved in downstream chemical signalling. We will also examine desmoplakin variants, lacking the SH3 domain or carrying disease mutants, to shed further light on desmoplakin’s force-carrying and force-sensitive role in stressed desmosomes.

To test eventual redox regulation of desmoplakin’s force response, we will subject the protein at different oxidation states to a newly developed disulfide swapping algorithm and monitor variations in the unfolding mechanism. Our results, after validation by single molecule experiments to be performed at King’s College London, can help to interpret and guide future in vitro and in vivo experiments. We expect our work to reveal, for the first time, a direct role of desmoplakin in force transmission and conversion of mechanical stress into biochemical signals.

Expertise

- computational biophysics

- Molecular Dynamics simulations

- coarse grained models and Brownian dynamics

- bioinformatics

- quantum chemistry

 

 

J. Großhans, F. Wolf: Coordinated dynamics of epithelial cells in the amnioserosa of Drosophila embryos

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Prof. Dr. Jörg Großhans

Georg-August-Universität Göttingen
Institute of Developmental Biochemistry
 

Justus-von-Liebig Weg 11
37077 Göttingen

Tel: +49 (0)551-398242 (office)

jgrossh(at)gwdg.de

Homepage

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Prof. Dr. Fred Wolf

Max-Planck-Institut für Dynamik und Selbstorganisation
Theoretische Neurophysik
 

Am Fassberg 17
37077 Göttingen

Tel: +49 (0)551-5176-423 (office)

fred(at)nld.ds.mpg.de

Homepage

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Prachi Richa

Georg-August-Universität Göttingen
Institute of Developmental Biochemistry
 

Justus-von-Liebig Weg 11
37077 Göttingen

Tel: +49 (0)551-398273 (office)

prachi.richa(at)med.uni-goettingen.de

Summary

Epithelial cells are capable of sensing and reacting to forces and movements generated by or transmitted through their neighbors. Dorsal closure is a major morphogenetic transformation in Drosophila embryos that critically depends on the dynamics of a squamous epithelium called the amnioserosa. Recent findings identified the dynamics of epithelial cells in the amnioserosa (AS cells) as a promising model system for dissecting how epithelial cells coordinate their mechanical activities. AS cells (i) exhibit mechanical behaviors that depend on tissue state and appear coordinated between cells, (ii) are highly accessible to genetic intervention and quantitative live cell imaging, and (iii) exhibit coordinated activity that is statistically invariant over extended periods of time, a fundamental mathematical condition of applicability for data-driven stochastic modelling techniques. Our preliminary data indicate that in xit mutant embryos, in which E-cadherin clusters appear abnormally mobile, intercellular coordination is profoundly disturbed. This suggests that mechano-transduction by E-cadherin based signaling complexes is critical for intercellular coordination. Based on these results and taking advantage of the accessibility of the AS, the current project aims to identify and quantitatively model mechano-transduction mechanisms operating at intercellular junctions between AS cells by combining fly developmental genetics, and in vivo time-lapse imaging (JG), with methods from the mathematical theory of stochastic dynamical systems and large-scale image analysis (FW). In particular, we aim (1) to identify the molecular basis of mechano-transduction mechanisms that turn the mechanical activity and state of neighboring cells into intracellular chemical signals, (2) to use massive live-imaging data to determine quantitative models for the encoding of mechanical stimuli by intracellular chemical signals, and (3) to probe the function of AS cell mechano-transduction by genetically and optically perturbing AS cell dynamics and transduction machinery. We expect that these studies will reveal key molecular components of mechano-transduction in epithelial cells and elucidate the principles by which this machinery guides their active mechanical behavior. Methodologically, the project is designed to demonstrate and optimize a widely applicable approach for obtaining quantitative models of cellular mechano-transduction from live cell imaging in intact tissues. 

Expertise

- Live imaging of embryonic development in Drosophila embryo
- Laser ablations
- Ca+2 uncaging using UV laser

M. Hatzfeld: Characterization of plakophilins as desmosomal signalling hubs controlling intercellular adhesion and proliferation in the epidermis

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Principal investigator

Prof. Dr. Mechthild Hatzfeld

Martin-Luther-University, Halle
Institute of Molecular Medicine
Division of Pathobiochemistry

 
 

Tel: +49 (0)345-5574422 (office)

mechthild.hatzfeld(at)medizin.uni-halle.de

Homepage

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Associated collaborator

Katrin Rietscher

Leipzig University
Institute of Biology
Div. of Cell and Developmental Biology

 
 

Tel: +49 (0)341-97-39583 (office)

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Associated collaborator

Assoc. Dr. Rene Keil

Martin-Luther-University, Halle
Institute of Molecular Medicine
Division of Pathobiochemistry

 
 

Tel: +49 (0)345-5573836 (office)

rene.keil(at)medizin.uni-halle.de

Homepage

Summary

The epidermis is a multi-layered self-renewing tissue. Proliferating cells in the basal layer continuously move up into the suprabasal layers and differentiate. This process of regeneration is regulated by various kinds of growth factors many of which are produced by keratinocytes. Members of the epidermal growth factor (EGF) and insulin-like growth factor (IGF) families play a central role in regulating proliferation versus differentiation. Cohesion in the epidermis is primarily mediated by desmosomes which must be tightly regulated to allow for plasticity on the one hand without compromising tissue cohesion and barrier function on the other hand. Plakophilins (PKPs) 1-3 are components of the desmosomal plaque that links keratin filaments to the desmosomal cadherins. Although it is known that at least one PKP is necessary to build a desmosome, the differential contribution of PKPs to desmosome formation, size and stability as well as to extra-desmosomal functions is still an open question.

In our previous work, we have shown that PKPs 1 and 3 act as switches between desmosomal adhesion, cell proliferation, cell migration and anchorage independent growth. We find that in vitro, PKP1 strengthens intercellular adhesion and increases desmosome size. However, PKP1 can also stimulate cell proliferation by associating with the translation initiation complex to increase protein biosynthesis. This correlates with decreased intercellular cohesion. Activation of these non-desmosomal functions of PKP1 depends on its phosphorylation by the Akt2 kinase downstream of IGF1/insulin signaling. In this setting, PKP1 is translocated from desmosomes into the cytoplasm. The loss of PKP1-desmosome association correlates with a loss of intercellular cohesion, increased proliferation and anchorage independent growth.

The aim of the current project is to characterize the differential roles of PKPs 1 and 3 in growth factor signaling in detail and determine their role in epidermal homeostasis.

Expertise

Cell biology of desmosomes, signaling via adhesion molecules, keratinocyte culture, microscopy (live cell imaging, FRET, FRAP, immunofluorescence)

S. Iden: Coupling intercellular adhesion and cell polarity signaling at epidermal junctions

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Principal investigator

Dr. Sandra Iden

University of Cologne
CECAD Research Center
Research group Cell Polarity and Cancer

Joseph-Stelzmann-Str. 26
50931 Köln

Tel: +49 (0)221-478-89587 (office)

sandra.iden(at)uk-koeln.de

Homepage

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SPP funded Collaborator

Martim Gomes

University of Cologne
CECAD Research Center
Research group Cell Polarity and Cancer

Joseph-Stelzmann-Str. 26
50931 Köln

Tel: +49 (0)221-478-84375 (office)

mgomes(at)uni-koeln.de

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Assoc. Collaborator

Michael Saynisch

University of Cologne
CECAD Research Center
Research group Cell Polarity and Cancer

Joseph-Stelzmann-Str. 26
50931 Köln

Tel: +49 (0)221-478-8950 (office)

michael.saynisch(at)uk-koeln.de

Summary

My group investigates functions of mammalian polarity proteins in skin morphogenesis and homeostasis, epithelial regeneration and stress responses as well as cancer. We study how deregulated polarity signaling impacts on cyto-architecture, survival and cell death using genetically modified mice in developmental and disease models as well as 2D and 3D in vitro cell culture systems. Our aim is to better understand how cell polarity signaling contributes to fundamental epithelial functions and to age-associated pathologies to reveal novel directions for targeted therapies.

Expertise

mouse disease models (skin cancer, wound healing), functional assays to study cell-cell adhesion and cell polarization, primary (co)cultures of keratinocytes and melanocytes, live cell imaging, quantitative morphometric analyses

A. Janshoff: Tension Generation in Epithelial Cells – the Impact of Next Neighbors

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Principal investigator

Prof. Dr. Andreas Janshoff

University of Goettingen
Institute of Physical Chemistry
 

Tammannstr. 6
37077 Goettingen

Tel: +49 (0)551-3910633 (office)

ajansho(at)gwdg.de

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SPP funded collaborator

Susanne Karsch

University of Goettingen
Institute of Physical Chemistry
 

Tammannstr. 6
37077 Göttingen

Tel: +49 (0)551-3933960 (office)

skarsch1(at)uni-goettingen.de

Summary

The goal of the project is to investigate the mechanotransduction of cell-cell contacts in the context of confluent epithelial monolayers. The proposal is driven by the central hypothesis that adherens junctions transmit forces to neighboring cells and thereby report about chemical and physical stimuli of individually treated cells. The mechanical response of epithelial cells to external stress heavily depends on the polarization state and strength of cell-cell contacts. Here, we want to explore how cells respond to chemical and physical stimuli applied to neighboring cells and to what extent cell-cell contacts alter the mechanical response to external stress. Therefore,  a single cell will be wounded or manipulated, while the state of the adjacent neighbors is monitored.
 

Expertise

Atomic Force Microscopy, Optical Tweezer, Imaging, Microinjection

V. Lecaudey: Role of the tight junction-associated protein Amotl2a in regulating the Hippo pathway and the size of the posterior lateral line primordium in zebrafish

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Principal investigator

Prof. Dr. Virginie Lecaudey

University of Frankfurt
 
 

Max-von-Laue-Str. 13
60438 Frankfurt (Main)

Tel: +49 (0)69-798-42102 (office)

lecaudey(at)bio.uni-frankfurt.de

Homepage

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SPP funded collaborator

Christine Molenda

University of Frankfurt
 
Developmental Biology of Vertebrates

Max-von-Laue-Str. 13
60438 Frankfurt (Main)

 

molenda(at)bio.uni-frankfurt.de

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SPP funded collaborator

David Kleinhans

University of Frankfurt
 
Developmental Biology of Vertebrates

Max-von-Laue-Str. 13
60438 Frankfurt (Main)

Tel: +49 (0)6979842106 (office)

kleinhans(at)bio.uni-frankfurt.de

Summary

Control of organ size is a crucial aspect of embryonic development and homeostasis. Yet how cells sense when an organ has reached its final size and limit its growth is far from being understood. The Hippo signaling pathway plays a fundamental role in this control. When Hippo signaling is active, the downstream effectors Yap and Taz get phosphorylated and retained in the cytosol. In contrast, when Hippo signaling is inactive, Yap and Taz can translocate into the nucleus and activate the transcription of genes promoting proliferation and survival. Recently, the junction-associated proteins of the Motin family have been shown to inhibit Yap/Taz independent of the core kinase cascade.
The lateral line (LL) of zebrafish is a very powerful model to study epithelial morphogenesis. The LL primordium (LLP) is a group of about 100 adherent cells that collectively migrate on both sides of the fish embryo. As they migrate, cells change their shape to form cell clusters that are then deposited and differentiate into mechanosensory organs. In this project, we use this system to understand how tissue growth is controlled. We recently showed that loss of the Motin protein Amotl2a leads to an inc
rease in proliferation, and thus in the size of the LLP. This growth-limiting function is mediated by the Hippo pathway effector Yap1, with which Amotl2a physically interacts, and the Wnt/β-catenin effector Lef1. Since Motin proteins are also known to interact with junction complexes and with the actin cytoskeleton, they are good candidates to be implicated in the response of cells to mechanical forces. The main goal of our project is to investigate whether Amotl2a acts as a sensor of changes in cell density or cell shape to control proliferation and growth.

Expertise

Use of zebrafish as a model organism; Live imaging; Generation of zebrafish mutants and genome editing using TALEN and Cas9/Crispr

R. Leube: ...

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Principal investigator

Prof. Dr. Rudolf Leube

University Hospital Aachen
MOCA
 

Pauwelsstraße 30
52074 Aachen

Tel: +49 (0)241-8089107 (office)

rleube(at)ukaachen.de

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SPP funded collaborator

Dr. Marcin Moch

University Hospital Aachen
MOCA
 

Pauwelsstraße 30
52074 Aachen

 

Summary

The cytoplasmic keratin intermediate filaments together with their desmosomal anchorage sites at cell-cell borders are hallmark features of epithelial differentiation. The keratin cytoskeleton thereby establishes a transcellular scaffold that affects all aspects of epithelial function requiring a highly dynamic regulation of keratin-desmosome interactions. The central function of the keratin-desmosome complex is evidenced by many genetic and acquired epithelial diseases, in which either keratin polypeptides or desmosomal components are modified. Although molecular binding sites between desmosomal components and keratin polypeptides have been identified, the consequences of desmosomal anchorage for motility, turnover and mechanical properties of keratin filaments have not been studied in detail. Even less is known how the different states of desmosomal adhesion, which have been classified as calcium-sensitive and calcium-insensitive (hyperadhesive), and how desmosomal signaling affects the keratin cytoskeleton. Instead, most of our current knowledge on keratin filament dynamics is based on observations in isolated single cells, which do not reflect the native tissue context. The proposed work therefore aims to fill the existing gap by comparing keratin filaments that are anchored to desmosomes of different adhesive strength with those that are not.

To do this, we will examine the keratin cytoskeleton in human immortalized HaCaT keratinocyte-derived cell lines with no desmosomes, calcium-sensitive desmosomes, hyperadhesive desmosomes, ectopic desmosomal plaques and modified desmosomal signaling. Using advanced microscopy techniques, image analysis routines and tools for measurements of cell mechanics that we have developed for single epithelial cells we want to examine how desmosomal anchorage affects keratin filament branching and bundling, keratin filament motility, keratin filament turnover and cytoplasmic viscoelasticity. We also want to examine how desmosome-mediated mechanical stress affects keratin network morphology and dynamics.

Expertise

Research at MOCA concentrates on the intermediate filament cytosekeleton and its interaction with junctional complexes using genetic and biochemical tools to manipulate cells (2D and 3D cell culture) and organisms (mouse and C. elegans). We employ microscopy to analyze and monitor these interactions in various constellations at different temporal (imaging of fixed specimen and time-lapse recording of vital specimen) and spatial resolution (epifluorescene, confocal and light sheet microscopy and electron microscopy).

T. Magin: Mechanotransduction and signalling by the desmosome/keratin complex

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Principal investigator

Prof. Dr. rer. nat. Thomas Magin

Leipzig University
Institute of Biology
Div. of Cell and Developmental Biology

Philipp-Rosenthal-Str. 55
04103 Leipzig

Tel: +49 (0)341-97-39582 (office)

thomas.magin(at)uni-leipzig.de

Homepage

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SPP funded collaborator

Dr. Fanny Büchau

Leipzig University
Institute of Biology
Div. of Cell and Developmental Biology

 
 

Tel: +49 (0)341-97-39583 (office)

fanny.buechau(at)uni-leipzig.de

Associated collaborator

Dr. Jamal Bouameur

Leipzig University
Institute of Biology
 

 
 

Tel: +49 (0)341-97-39581 (office)

jamal-eddine.bouameur(at)uni-leipzig.de

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Associated collaborator

Dr. Melanie Homberg

Leipzig University
Institute of Biology
 

 
 

Tel: +49 (0)341-97-39586 (office)

melanie.homberg(at)uni-leipzig.de

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Associated collaborator

Andrea Scheffschick

Leipzig University
Institute of Biology
 

 
 

Tel: +49 (0)341-97-39585 (office)

andrea.scheffschick(at)uni-leipzig.de

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Associated collaborator

Alyssa Vetter

Leipzig University
Institute of Biology
 

 
 

Tel: +49 (0)341-97-39586 (office)

alyssa.vetter(at)uni-leipzig.de

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Associated collaborator

Kristin Jahn

Leipzig University
Institute of Biology
 

 
 

Tel: +49 (0)341-97-39585 (office)

kristin.jahn(at)uni-leipzig.de

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SPP funded collaborator

Aileen Wingenfeld

Leipzig University
Institute of Biology
 

 
 

Tel: +49 (0)341-97-39580 (office)

aileen.wingenfeld(at)uni-leipzig.de

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Associated collaborator

Katrin Rietscher

Leipzig University
Institute of Biology
Div. of Cell and Developmental Biology

 
 

Tel: +49 (0)341-97-39583 (office)

Summary

The epidermis protects the body against mechanical force, dehydration and infections by virtue of interactions between cell adhesion complexes and the cytoskeleton. These functions rely to a large extent on the desmosome/keratin complex (DKC). To which extent desmosome composition determines cytoskeletal organization, cell signaling and differentiation and vice versa, how keratins affect desmosome adhesion and signalling function, remains largely unknown. To address these questions, we have generated mice and keratinocyte cell lines that either lack the entire keratin protein family or re-express distinct sets of keratins. These tools allow for the first time to dissect DKC functions in sensing and transmitting mechanical and chemical signals. We will investigate 1) the interdependence of desmosome-keratin composition, 2) the role of phosphorylation in regulating keratin-desmosome interactions, 3) the influence of strain on the desmosome-keratin complex and 4) strain-dependent transcriptional changes in normal and keratin-deficient keratinocytes.

We expect that this project significantly advances the understanding of the above protein complex in epidermal differentiation, barrier function and stress responses.

Expertise

Mechanisms of epidermal differentiation; molecular cell biology of keratins and desmosomes, keratinocyte culture, transgenic mouse models

M. Matis: Mechanobiological Analysis of Microtubule-Based Forces at Epithelial Adherens Junctions During Tissue Morphogenesis

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Principal investigator

Dr. Maja Matis

University of Münster
Institute of Cell Biology
Developmental Mechanobiology Group

Von-Esmarch-Straße 56
48149 Münster

Tel: +49 (0)251-83-57183 (office)

matism(at)uni-muenster.de

Homepage

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SPP funded collaborator

Amrita Singh

University of Münster
Institute of Cell Biology
Developmental Mechanobiology Group

Von-Esmarch-Straße 56
48149 Münster

Tel: +49 (0)251-83-52187 (office)

amrita.singh(at)uni-muenster.de

Summary

During tissue morphogenesis, individual cells self-assemble into complex tissues and organs with highly specialized forms and functions. Such precise sculpting requires the application of forces generated within cells by the cytoskeleton and transmission of these forces through adhesion molecules within and between neighboring cells.

In order to reshape a tissue, force generation must exceed mechanical resistance, thus global patterns of force generation and tissue stiffness jointly dictate speed and direction of tissue rearrangements. While many of the genes and chemical cues that regulate these processes during morphogenesis have been identified, little is known quantitatively about how these mechanical processes are coupled across cells in a developing tissue. Despite growing evidence that MT can generate forces in cells in a manner analogous to actin, relatively little is known about how coupling of MT-based forces at epithelial intercellular junctions contributes to the mechanical state of tissue and cell-shape changes during morphogenesis.

The goal of this project is to develop and apply new tools that will help answering the fundamental question how cells coordinate forces across a tissue during morphogenetic rearrangements. We will use a dual approach that relies on new optical and chemical tools that, in conjunction with classical genetic approaches, will be used to quantitatively analyze how the cytoskeleton coordinates forces across cells during morphogenetic tissue rearrangements. Together, this interdisciplinary approach will allow us to quantitatively address the fundamental principles underlying force-control during tissue organization via MTs. We expect that insights from our study will uncover new roles of the MT cytoskeleton in epithelial tissue morphogenesis, and open up new inroads to investigate how derangement of MT dynamics at intercellular junctions leads to diseases.

Expertise

Our lab investigates the mechanical and structural properties of apical non-centrosomal MTs nucleated at adherens junctions.  For this we are using new optical and chemical tools (e.g live imaging, caged MT drugs, laser ablation, FRAP, FRET based tension sensors, etc.) in conjunction with classical genetic and proteomic approaches. The quantitative data obtained in this interdisciplinary approach are correlated with results obtained from quantitative image analysis of developing epithelium to study how mechanobiological properties of MTs contribute to tissue remodeling.

R. Merkel: Probing tensed cell-cell adhesions

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Principal investigator

Prof. Dr. Rudolf Merkel

Forschungszentrem Jülich GmbH
Institute of Complex Systems 7: Biomechanics
 

Leo-Brandt-Str.
52425 Jülich

Tel: +49 (0)2461-61-4551 (office)

rmerkel(at)fz-juelich.de

Homepage

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SPP funded collaborator

Dave Ahrens

Forschungszentrem Jülich GmbH
Institute of Complex Systems 7: Biomechanics
 

Leo-Brandt-Str.
52425 Jülich

Tel: +49 (0)2461-61-5119 (office)

d.ahrens(at)fz-juelich.de

SPP funded collaborator

Lena Ramms

Forschungszentrem Jülich GmbH
Institute of Complex Systems 7: Biomechanics
 

Leo-Brandt-Str.
52425 Jülich

Tel: +49 (0)2461-61-1413 (office)

l.ramms(at)fz-juelich.de

Summary

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Expertise

optical imaging & digital image processing, statistical data analysis, micromechanical probing of cells, nanotechnology, soft replica molding, AFM, micropipette aspiration, optical spectroscopy, calorimetry, dynamic force spectroscopy

C. Niessen: Mechanotransduction and cytoskeletal organization by cadherins in stratifying epithelia

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Principal investigator

Prof. Dr. Carien Niessen

University of Cologne
CECAD Research Center
 

Joseph-Stelzmann-Str. 26
50931 Köln

Tel: +49 (0)221-478-89512 (office)

carien.niessen(at)uni-koeln.de

Homepage

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SPP funded collaborator

Placido Pereira

University of Cologne
CECAD Research Center
 

Joseph-Stelzmann-Str. 26
50931 Köln

Tel: +49 (0)221-478-89912 (office)

junio3p(at)hotmail.com

Homepage

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Associated collaborator

Dr. Matthias Ruebsam

University of Cologne
CECAD Research Center
 

Joseph-Stelzmann-Str. 26
50931 Köln

Tel: +49 (0)221-478-89912 (office)

ruebsam0(at)uni-koeln.de

Homepage

Associated collaborator

Dr. Alexander Kyumurkov

University of Cologne
CECAD Research Center
 

Joseph-Stelzmann-Str. 26
50931 Köln

Tel: +49 (0)221-478-89912 (office)

akyumurkov(at)gmail.com

Homepage

Summary


Tissue formation requires the coordination of forces across cells and tissue boundaries to drive cellular rearrangements. The skin epidermis is a self-renewing multi-layered stratifying epithelium and crucial for skin barrier function. Self-renewal of basal stem cells is balanced with a spatiotemporal controlled differentiation program of their progeny. This program is accompanied by spatial coordination of adherens junction and cytoskeletal organization and cell shape changes. However, it is not known whether junctional tension and cell shape changes control selfrenewal and differentiation programs. In the present proposal we ask how cadherins control coordinated by cadherins and whether this is important for epidermal morphogenesis and homeostasis. To this end we will characterize in depth how classical cadherins coordinate the structure and organization of adherens junctions and associated actomyosin cytoskeleton in the self-renewing epidermis using a combined imaging and proteomics approach on in vivo and in vitro models. We will further ask whether tension across cadherin complexes regulate epidermal adhesive and tensile strength and drive epidermal self-renewal, differentiation and intercellular migration. Together, the experiments proposed will likely contribute to a better understanding of the molecular mechanisms by which cadherin/catenin mechanosensing control the morphogenesis and homeostasis of stratifying epithelia.

Expertise

Transgenic mouse models, primary cell culture, imaging

N. Schlegel, J. Waschke: Role of Dsg2-dependent adhesion and signalling in Crohn’s disease

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Principal investigator

PD Dr. Nicolas Schlegel

Universität Würzburg
Klinik und Poliklinik für Allgemein-, Viszeral-, Gefäß-, und Kinderchirurgie
 

 
 

 

schlegel_n(at)ukw.de

Homepage

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Principal investigator

Prof. Dr. Jens Waschke

Ludwig-Maximilians-Universität München
Institute of Anatomy and Cell Biology
Department I

Pettenkoferstraße 11
80336 München

 

jens.waschke(at)med.uni-muenchen.de

Homepage

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SPP funded collaborator

Hanna Ungewiss

Ludwig-Maximilians-Universität München
Institute of Anatomy and Cell Biology
Department I

Pettenkoferstraße 11
80336 München

 

hanna.ungewiss(at)med.uni-muenchen.de

Summary

Crohn’s disease (CD) is an inflammatory bowel disease (IBD) with complex pathogenesis which is characterized by impaired intestinal epithelial barrier integrity. We previously showed that desmosomes besides of adherens junctions are required for maintenance of barrier properties in enterocytes and that desmoglein 2 (Dsg2), which together with desmocollin 2 is the major desmosomal adhesion molecule, is crucial in this context.

Therefore, we started to investigate the role of Dsg2 in CD and found that in patients’ intestinal biopsies suffering from conservative refractory CD Dsg2 is reduced and displays altered localization. A possible role of Dsg2 in CD is new and the mechanisms by which Dsg2 strengthens the intestinal barrier are unclear. As with other autoimmune diseases treatment options in CD are limited and associated with severe side-effects. Understanding the mechanism how Dsg2 is involved in CD pathogenesis would possibly allow to establish new therapeutic approaches. Preliminary data indicate that tumor necrosis factor α (TNFα), which is well known to be critically involved in CD pathogenesis compromised Dsg2-dependent enterocyte cohesion. In keratinocytes, we recently found that the contribution of desmosomal cadherins to overall cell cohesion as well as to the signalling pathways regulated by specific Dsg isoforms substantially differ and that adhesive properties and signal transduction appear to be linked. Thus, the role of Dsg2 as adhesion-dependent signaling hub in enterocytes needs to be clarified. We will investigate adhesion- and signaling-dependent functions of Dsg2 in CD in vitro and in vivo. In patients’ biopsies alterations in Dsg2 turnover and localization will be correlated with disease stage and localization within the gut. In addition, the signaling pathways by which TNFα regulates enterocyte desmosomal adhesion and which downstream of Dsg 2 control barrier properties and more specifically tight junction integrity will be determined. Therefore, in cultured monolayers of intestinal epithelial cells the effects of TNFα on Dsg2 localization and Dsg2-mediated cell cohesion will be studied using dissociation assays, atomic force microscopy as well as laser tweezers and modulated by Dsg-specific peptides. Transepithelial resistance (TER) and measurements of FITC-dextran flux across monolayers will be used to assess barrier function in vitro and DSS colitis and permeability measurements in isolated gut segments will be applied in vivo. Signaling pathways will be investigated with focus on p38MAPK, cAMP and Rho-GTPase signaling which are known to be linked to regulation of the intestinal barrier and desmosomal adhesion. Finally, the modulating effect of cortisol on Dsg2 adhesive function and on signalling pathways will be characterized.

Expertise

Regulation of desmosomes and adherens junctions in context with epithelial and endothelial barriers, force measurements on living cells by AFM

P. Strnad: Consequences of desmosomal alterations in the intestinal epithelia

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Principal investigator

PD Dr. Pavel Strnad

University Hospital Aachen
Department of Internal Medicine III
 

Pauwelsstraße 30
52074 Aachen

Tel: +49 (0)241-80-35324 (office)

pstrnad(at)ukaachen.de

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Associated collaborator

Assoc. Prof. Dr. Peter Boor

University Hospital Aachen
Institute of Pathology
 

Pauwelsstraße 30
52074 Aachen

Tel: +49 (0)241-80-85227 (office)

pboor(at)ukaachen.de

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Associated collaborator

Dr. Sonja Djudjaj

University Hospital Aachen
Institute of Pathology
 

Pauwelsstraße 30
52074 Aachen

 

sdjudjaj(at)ukaachen.de

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SPP funded collaborator

Annika Gross

University Hospital Aachen
Department of Internal Medicine III
 

Pauwelsstraße 30
52074 Aachen

 

angross(at)ukaachen.de

Summary

To protect the organism against luminal pathogens while enabling selective uptake of nutrients through specific transport systems, intestinal epithelia contain the apical junctional complex (AJC) consisting of tight junctions, adherens junctions and desmosomes. Desmosomes constitute the least investigated AJC component and are composed of transmembrane cadherins of the desmoglein (Dsg) and desmocollin (Dsc) type that are associated through the intracellular plaque proteins plakoglobin, plakophilin and desmoplakin to the cytoplasmic keratin intermediate filament cytoskeleton. Dsg2 and Dsc2 are the major desmosomal cadherins of intestinal epithelia. They have been implicated in the regulation of epithelial cell proliferation and tumorigenesis. Recent data indicate that Dsg2 is reduced in patients with inflammatory bowel disorders and that stabilization of inflammation-induced Dsg2 loss may ameliorate a loss of epithelial barrier function. To further study the functional relevance of Dsg2 in the intestinal epithelia, we generated intestine-specific, conditional DSG2 knockouts (DSG2 Δint/Δint) Gavage with FITC-dextran and subsequent FITC measurement in serum was used to assess intestinal permeability. Colitis was induced by five-day treatment with dextran sodium sulfate (DSS) or gavage-mediated infection with Citrobacter rodentium. DSG2 Δint/Δint mice display a robust knockdown of intestinal Dsg2 and a profound alteration of the remaining desmosomal components with upregulation of Dsc2 and a decrease in plakoglobin and desmoplakin while overall histology is inconspicuous. Under basal condition, DSG2 Δint/Δint mice are phenotypically normal but have a somewhat increased intestinal permeability. After DSS treatment, they suffer higher weight loss, and stronger epithelial damage/inflammation. 14 days after infection with Citrobacter rodentium, DSG2 Δint/Δint mice display stronger crypt hyperplasia and elevated levels of the proinflammatory/bacterial response genes. In our current proposal, we are assessing the pathomechanisms underlying the observed changes using genetically modified mice and intestinal organoids as the primary research tools.

Expertise

The group of PD Dr. Strnad studies the development and progression of chronic digestive diseases using transgenic animals and primary cell cultures as the major research models. The typical methods that are routinely used include a large variety of experimental murine digestive disease models, thorough histological/immunohistochemical analysis, microarray/omics approaches and basic biochemical methods (immunoprecipitation, subcellular fractionation, analysis of oxidative stress etc). Human relevance of the observed experimental findings is further evaluated in patients with digestive diseases that are either recruited in University Hospital Aachen or are available through a network of collaborating scientists.

Associate Prof. Dr. med. Volker Spindler

Summary

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Expertise

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