Progress in brain research, volume 214

Advisory Editors

Stephen G. Waxman

Bridget Marie Flaherty Professor of Neurology
Neurobiology, and Pharmacology;
Director, Center for Neuroscience &
Regeneration/Neurorehabilitation Research
Yale University School of Medicine
New Haven, Connecticut
USA

Donald G. Stein

Asa G. Candler Professor
Department of Emergency Medicine
Emory University
Atlanta, Georgia
USA

Dick F. Swaab

Professor of Neurobiology
Medical Faculty, University of Amsterdam;
Leader Research team Neuropsychiatric Disorders
Netherlands Institute for Neuroscience
Amsterdam
The Netherlands

Howard L. Fields

Professor of Neurology
Endowed Chair in Pharmacology of Addiction
Director, Wheeler Center for the Neurobiology of Addiction
University of California
San Francisco, California
USA


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Contributors
Hayder Amin
Istituto Italiano di Tecnologia, NetS3 Laboratory, Neuroscience and Brain
Technologies Dpt., Genova, Italy
Pavle Andjus
Center for Laser Microscopy, Institute for Physiology and Biochemistry, Faculty of
Biology, University of Belgrade, Belgrade, Serbia
Eleonora Aronica
Department of (Neuro)Pathology, Academic Medical Center and Swammerdam
Institute for Life Sciences, Center for Neuroscience, University of Amsterdam,
Amsterdam, and SEIN—Stichting Epilepsie Instellingen Nederland, Heemstede,
The Netherlands
Ke´vin Baranger
Aix Marseille Universite´, CNRS, UMR 7259, NICN, 13344, and Neurology and
Neuropsychology Department, AP-HM, Marseille, France
Martin Bastmeyer
Institute of Zoologie, Karlsruhe, and Institute of Functional Interfaces (IFG),
Karlsruhe Institute of Technology (KIT), Eggenstein-Leopoldshafen, Germany
Luca Berdondini
Istituto Italiano di Tecnologia, NetS3 Laboratory, Neuroscience and Brain

Technologies Dpt., Genova, Italy
Vladimir Berezin
Laboratory of Neural Plasticity, Department of Neuroscience and Pharmacology,
University of Copenhagen, Symbion, Fruebjergvej 3, Box 39, Copenhagen Ø,
Denmark
Katarzyna Bieganska
Cellular Neurophysiology, Hannover Medical School, Hannover, Germany
Judit Bigas
Iproteos S.L., Barcelona, Spain
Elodie Chabrol
UCL Institute of Neurology, University College London, Queen Square, London,
UK
Kae-Jiun Chang
Program in Developmental Biology, and Department of Neuroscience, Baylor
College of Medicine, One Baylor Plaza, Houston, TX, USA
Lorenzo A. Cingolani
Department of Neuroscience and Brain Technologies, Istituto Italiano di
Tecnologia, Genoa, Italy

v


vi

Contributors

Stefanie Dedeurwaerdere
Department of Translational Neuroscience, University of Antwerp, Wilrijk,
Belgium
Alexander Dityatev

Molecular Neuroplasticity Group, German Center for Neurodegenerative
Diseases (DZNE), Magdeburg, Germany; Medical Faculty, Otto-von-Guericke
University, Magdeburg, Germany; Center for Behavioral Brain Sciences (CBBS),
Magdeburg, Germany; Laboratory for Brain Extracellular Matrix Research,
University of Nizhny Novgorod, Nizhny Novgorod, Russia; Department of
Neuroscience and Brain Technologies, Istituto Italiano di Tecnologia, Genova,
Italy
Veronica Estrada
Molecular Neurobiology Laboratory, Department of Neurology, Heinrich-HeineUniversity Medical Center Du¨sseldorf, Du¨sseldorf, Germany
Andreas Faissner
Department of Cell Morphology and Molecular Neurobiology, Ruhr-University
Bochum, Bochum, Germany
James W. Fawcett
John van Geest Centre for Brain Repair, University of Cambridge, Forvie Site,
Robinson Way, Cambridge, UK
Charles ffrench-Constant
MRC Centre for Regenerative Medicine, The University of Edinburgh, Edinburgh,
UK
Mikhail Filippov
Molecular Neuroplasticity Group, German Center for Neurodegenerative
Diseases (DZNE), Magdeburg, Germany
Renato Frischknecht
Department for Neurochemistry and Molecular Biology, Leibniz Institute for
Neurobiology, and Center for Behavioral Brain Sciences (CBBS) Magdeburg,
Germany
Denis Grandgirard
Neuroinfection Laboratory, Institute for Infectious Diseases, University of Bern,
Bern, Switzerland
Anne Heikkinen
Oulu Center for Cell-Matrix Research, Biocenter Oulu and Faculty of Biochemistry

and Molecular Medicine, University of Oulu, Oulu, Finland
Natasˇa Jovanov Milosˇevic´
Croatian Institute for Brain Research, and Department of Medical Biology,
University of Zagreb School of Medicine, Zagreb, Croatia
Milosˇ Judasˇ
Croatian Institute for Brain Research, University of Zagreb School of Medicine,
Zagreb, Croatia


Contributors

Leszek Kaczmarek
Department of Molecular and Cellular Neurobiology, Nencki Institute, Warsaw,
Poland
Meghan E. Kerrisk
Department of Molecular Biophysics and Biochemistry, Yale University,
New Haven, CT, USA
Michel Khrestchatisky
Aix Marseille Universite´, CNRS, UMR 7259, NICN, 13344, Marseille, France
Anthony J. Koleske
Department of Molecular Biophysics and Biochemistry; Department of
Neurobiology; Interdepartmental Neuroscience Program, and Program in Cellular
Neuroscience, Neurodegeneration, and Repair, Yale University, New Haven, CT,
USA
Svetlana Korotchenko
Laboratory for Brain Extracellular Matrix Research, University of Nizhny
Novgorod, Nizhny Novgorod, Russia; Department of Neuroscience and Brain
Technologies; Istituto Italiano di Tecnologia, Genova, Italy
Ivica Kostovic
Croatian Institute for Brain Research, University of Zagreb School of Medicine,

Zagreb, Croatia
Jessica C.F. Kwok
John van Geest Centre for Brain Repair, University of Cambridge, Forvie Site,
Robinson Way, Cambridge, UK
Tomasz Lebitko
Department of Molecular and Cellular Neurobiology, Nencki Institute, Warsaw,
Poland
Stephen L. Leib
Neuroinfection Laboratory, Institute for Infectious Diseases, University of Bern,
Bern, and Biology Division, Spiez Laboratory, Swiss Federal Office for Civil
Protection, Spiez, Switzerland
Fabian D. Liechti
Neuroinfection Laboratory, Institute for Infectious Diseases, University of Bern,
Bern, Switzerland
Katherine Long
MRC Centre for Regenerative Medicine, The University of Edinburgh, Edinburgh,
UK
Bart R. Lubbers
Department of Molecular & Cellular Neurobiology, Center for Neurogenomics &
Cognitive Research, Neuroscience Campus Amsterdam, VU University
Amsterdam, HV Amsterdam, The Netherlands

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viii

Contributors

Katarzyna Łukasiuk

The Nencki Institute of Experimental Biology, Polish Academy of Sciences,
Warsaw, Poland
Alessandro Maccione
Istituto Italiano di Tecnologia, NetS3 Laboratory, Neuroscience and Brain
Technologies Dpt., Genova, Italy
Markus Morawski
University of Leipzig, EU-ESF Transnational Junior Research Group
“MESCAMP”, Paul Flechsig Institute for Brain Research, Leipzig, Germany
Mariusz Mucha
University of Exeter, Exeter, UK
Xavier E. Ndode-Ekane
Department of Neurobiology, A. I. Virtanen Institute for Molecular Sciences,
University of Eastern Finland, Kuopio, Finland
Thierry Nieus
Istituto Italiano di Tecnologia, NetS3 Laboratory, Neuroscience and Brain
Technologies Dpt., Genova, Italy
Ghislain Opdenakker
Department of Microbiology and Immunology, Laboratory of Immunobiology,
Rega Institute for Medical Research, University of Leuven, Leuven, Belgium
Robert Pawlak
University of Exeter, Exeter, UK
Taina Pihlajaniemi
Oulu Center for Cell-Matrix Research, Biocenter Oulu and Faculty of Biochemistry
and Molecular Medicine, University of Oulu, Oulu, Finland
Asla Pitka¨nen
Department of Neurobiology, A. I. Virtanen Institute for Molecular Sciences,
University of Eastern Finland, and Department of Neurology, Kuopio University
Hospital, Kuopio, Finland
Evgeni Ponimaskin
Cellular Neurophysiology, Hannover Medical School, Hannover, Germany

Elizabeth M. Powell
Department of Anatomy & Neurobiology, University of Maryland School of
Medicine, Baltimore, MD, USA
Lidija Radenovic
Center for Laser Microscopy, Institute for Physiology and Biochemistry, Faculty of
Biology, University of Belgrade, Belgrade, Serbia
Matthew N. Rasband
Department of Neuroscience, and Program in Developmental Biology, Baylor
College of Medicine, One Baylor Plaza, Houston, TX, USA


Contributors

Santiago Rivera
Aix Marseille Universite´, CNRS, UMR 7259, NICN, 13344, Marseille, France
Jesu´s Seco
Iproteos S.L., Barcelona, Spain
Constanze I. Seidenbecher
Center for Behavioral Brain Sciences (CBBS), and Department of
Neurochemistry and Molecular Biology, Leibniz Institute for Neurobiology,
Magdeburg, Germany
Oleg Senkov
Molecular Neuroplasticity Group, German Center for Neurodegenerative
Diseases (DZNE), Magdeburg, Germany
Alessandro Simi
Istituto Italiano di Tecnologia, NetS3 Laboratory, Neuroscience and Brain
Technologies Dpt., Genova, Italy
August B. Smit
Department of Molecular & Cellular Neurobiology, Center for Neurogenomics &
Cognitive Research, Neuroscience Campus Amsterdam, VU University

Amsterdam, HV Amsterdam, The Netherlands
Eduardo Soriano
Department of Cell Biology, University of Barcelona; Centro de Investigacio´n en
Red sobre Enfermedades Neurodegenerativas (CIBERNED), ISCIII, Madrid, and
Vall d’Hebron Institut de Recerca (VHIR), Barcelona, Spain
Sabine Spijker
Department of Molecular & Cellular Neurobiology, Center for Neurogenomics &
Cognitive Research, Neuroscience Campus Amsterdam, VU University
Amsterdam, HV Amsterdam, The Netherlands
Vera Stamenkovic
Center for Laser Microscopy, Institute for Physiology and Biochemistry, Faculty of
Biology, University of Belgrade, Belgrade, Serbia
Michal Stawarski
Laboratory of Cell Biophysics, Department of Molecular and Cellular
Neurobiology, Nencki Institute of Experimental Biology, Warsaw, Poland
Teresa Tarrago
Iproteos S.L., and Institute for Research in Biomedicine (IRB Barcelona),
Barcelona, Spain
Ayse Tekinay
UNAM-National Nanotechnology Research Center, Institute of Materials Science
and Nanotechnology, Bilkent University, Ankara, Turkey
Ursula Theocharidis
Department of Cell Morphology and Molecular Neurobiology, Ruhr-University
Bochum, Bochum, Germany

ix


x

Contributors

Effie Tsilibary
Institute of Biosciences and Applications, NCSR “Demokritos”, Athens, Greece
Athina Tzinia
Institute of Biosciences and Applications, NCSR “Demokritos”, Athens, Greece
Jo Van Damme
Department of Microbiology and Immunology, Laboratory of Immunobiology,
Rega Institute for Medical Research, University of Leuven, Leuven, Belgium
Michel C. van den Oever
Department of Molecular & Cellular Neurobiology, Center for Neurogenomics &
Cognitive Research, Neuroscience Campus Amsterdam, VU University
Amsterdam, HV Amsterdam, The Netherlands
Jennifer Vandooren
Department of Microbiology and Immunology, Laboratory of Immunobiology,
Rega Institute for Medical Research, University of Leuven, Leuven, Belgium
Lydia Vargova
Charles University, 2nd Faculty of Medicine, and Institute of Experimental
Medicine AS CR, v.v.i., Department of Neuroscience, Prague, Czech Republic
Naiara Vazquez
Department of Translational Neuroscience, University of Antwerp, Wilrijk,
Belgium
Matthew C. Walker
UCL Institute of Neurology, University College London, Queen Square, London,
UK
Peter S. Walmod
Laboratory of Neural Plasticity, Department of Neuroscience and Pharmacology,
University of Copenhagen, Symbion, Fruebjergvej 3, Box 39, Copenhagen Ø,
Denmark
Bernhard Wehrle-Haller

Department of Cell Physiology and Metabolism, Centre Me´dical Universitaire,
University of Geneva, Geneva, Switzerland
Hans Werner Mu¨ller
Molecular Neurobiology Laboratory, Department of Neurology, Heinrich-HeineUniversity Medical Center Du¨sseldorf, Du¨sseldorf, Germany
Grzegorz M. Wilczynski
The Nencki Institute of Experimental Biology, Polish Academy of Sciences,
Warsaw, Poland
Jakub Wlodarczyk
Laboratory of Cell Biophysics, Department of Molecular and Cellular
Neurobiology, Nencki Institute of Experimental Biology, Warsaw, Poland


Contributors

Sujeong Yang
John van Geest Centre for Brain Repair, University of Cambridge, Forvie Site,
Robinson Way, Cambridge, UK
Michisuke Yuzaki
Department of Physiology, School of Medicine, Keio University, Tokyo, Japan
Andre Zeug
Cellular Neurophysiology, Hannover Medical School, Hannover, Germany

xi


Preface
The organization of the extracellular matrix (ECM) is a reflection of the role and
function of organs in our bodies. The interaction of cells with the ECM determines
their polarity, shape, and form and is providing cues for survival and proliferation.
The brain, in comparison with other organs, shows an extremely complex architecture, in which neurons, glial cells, and blood vessels are interacting to create and

maintain a dynamic network, in which beneficial synaptic connections need to be
actively maintained and other remodeled in response to changes in signaling input.
Similar to other organ systems, cell–cell interactions based on direct contacts via
cadherins and signaling receptors, as well as cell–matrix interactions with the
ECM scaffold, are controlling the organization of glial cells and neurons as well as
the projections of neurites and location of synapses. All these structures are
embedded within an ECM scaffold formed by fiber or network-forming proteins
and membrane-anchored or secreted glycosaminoglycans.
Despite recent advances in the ECM field, the importance of neural ECM for
physiological and pathological processes is less widely recognized than that of other
nervous system elements. To overcome this, a European consortium “Brain Extracellular Matrix in Health and Disease (ECMNet)” was established in 2010 as a part
of intergovernmental framework for European Cooperation in Science and Technology (COST). Now, ECMNet combines more than 200 young and established researchers from 20 European countries ( Each book
chapter of this volume is prepared involving ECMNet members and other leading
experts from the USA and Japan. The chapters cover the broad range of topics,
grouped into four parts, which are devoted to normal physiological functions of
neural ECM, its role in brain diseases, development of methods to image the
ECM, to therapeutically target it, and to generate artificial ECM.

FUNCTIONS OF NEURAL ECM
The neural ECM is well recognized to play a key role in neural development and the
first two chapters of the book are devoted to this topic. Theocharidis, Long, ffrenchConstant, and Faissner (2014) discuss available data on expression of tenascins,
laminins, and proteoglycans in the ECM of the stem cell niche and argue for crucial
importance of ECM for the biology of this cellular compartment. Heikkinen,
Pihlajaniemi, Faissner, and Yuzaki (2014) focus on how proteoglycans, tenascin,
and C1q (C1qDC) family proteins regulate synapse formation, maintenance, and
pruning during neural development. In the adult central nervous system (CNS), multiple neural ECM molecules together with astroglial, pre-, and postsynaptic elements
form tetrapartite synapses, and the ECM regulates Hebbian synaptic plasticity
through the modulation of perisomatic GABAergic inhibition, intrinsic neuronal excitability, and intracellular signaling, as presented by Senkov, Andjus, Radenovic,

xiii

xiv

Preface

Soriano, and Dityatev (2014). This chapter also gives an account on bidirectional modulation of memory acquisition by ECM molecules and highlights that removal of ECM
may promote cognitive flexibility and extinction of fear and drug memories. To stabilize network dynamics and avoid hypo- and hyperexcitability of neurons, adaptive
Hebbian modifications of neurons and synapses must be complemented by homeostatic forms of plasticity. Frischknecht, Chang, Rasband, and Seidenbecher (2014)
point to the ECM as a prime candidate to orchestrate and integrate individual cellular
states into the homeostasis of the tissue, which is implemented via synaptic scaling,
adjustment in the balance between excitation and inhibition, and axon initial segment
plasticity. Many effects of ECM molecules are mediated by their interactions with
cognate ECM receptors, first of all, integrins. Kerrisk, Cingolani, and Koleske
(2014) discuss how activation of ECM receptors modulates downstream signaling cascades that control cytoskeletal dynamics and synaptic activity to regulate neuronal
structure and function and thereby impact animal behavior. Tsilibary and
colleagues (2014) focus on the role of extracellular proteolysis and put forward a challenging view that the main function of proteolysis is not the degradation of ECM and
the loosening of perisynaptic structures, but rather a release of signaling molecules
from the ECM, transsynaptic proteins, and latent forms of growth factors.

NEURAL ECM IN BRAIN DISEASES
As summarized in the first part of this volume, various components of the ECM play
a significant role in maintenance of the environmental milieu for different cell types
in the CNS and in regulation of cellular responses to physiological stimuli. Compelling evidence collected over recent years, however, demonstrate that plasticity in the
ECM can also be triggered by genetic or acquired pathological stimuli to the brain.
Moreover, the ECM is an active player in the CNS repair process by forming a scaffold, which orchestrates the cellular plasticity events toward either favorable or unfavorable outcome over the lifespan. Milosˇevic´, Judasˇ, Aronica, and Kostovic (2014)
discuss the expression pattern of major components of the fetal ECM in the human
brain and the role they play during normal laminar and connectivity development as
well as in the neurodevelopmental disorders. Kwok, Yang, and Fawcett (2014) address current progresses of chondroitin sulfate proteoglycans in regulating plasticity
in neurodegenerative diseases, brain tumors, and CNS injury. They also investigate

the opportunities of manipulating ECM to facilitate postinjury recovery. Vandooren,
Damme, and Ghislain Opdenakker (2014) discuss the mechanisms of matrix metalloproteinase MMP-9 in neuroinflammation, and the use of MMP-9-specific inhibitors
as anti-inflammatory agents. Morawski, Filippov, Tzinia, Tsilibary, and Vargova
(2014) review the information on age-related changes in the ECM, how they could
contribute to pathophysiology of neurodegenerative diseases, such as Alzheimer’s
disease, and what could be the therapeutic approaches targeted to the ECM to combat,
for example, amyloid clearance. Pitka¨nen et al. (2014) review the role of uPARinteractome, MMPs and TIMPs, tenascin-R, and LG1 in different epilepsy syndromes


Preface

and how they contribute to epileptogenesis and ictogenesis. In addition, the role of the
ECM in epilepsy-related comorbidies and the current status of in vivo imaging of
ECM-related molecules in patients are discussed. Lubbers, Smit, Spijker, and van
den Oever (2014) review neurodevelopmental and other mechanisms affecting different components of the ECM, which could lead to the expression of neuropsychiatric
disorders, in particular, addiction, schizophrenia, and mood disorders.

NEURAL ECM-TARGETING TOOLS AND THERAPEUTICS
There is a growing interest to develop methodology allowing for detailed structural
and functional analysis of ECM, particularly in vivo, to be able to follow ECM remodeling during plasticity and in diseased brains. Zeug et al. (2014) provide a detailed
overview of current microscopic methods used for ECM analysis and also describe
general labeling strategies for ECM visualization and imaging of the proteolytic reorganization of ECM as well as applications of F€orster resonance energy transferbased approaches to monitor ECM functions with a high spatiotemporal resolution.
Baranger et al. (2014) discuss data on the endogenous MMP inhibitors in the CNS
and regulation of MMP-mediated proteolysis in inflammatory, neurodegenerative
and infectious diseases, and synthetic inhibitors of MMPs and the perspective of their
therapeutic use. Berezin, Walmod, Filippov, and Dityatev (2014) provide a comprehensive overview of multiple strategies for targeting the ECM molecules and their
metabolizing enzymes and receptors with antibodies, peptides, glycosaminoglycans,
and other natural and synthetic compounds. They also discuss application of developing ECM-targeting drugs in Alzheimer’s disease, epilepsy, schizophrenia, addiction, multiple sclerosis, Parkinson’s disease, and cancer.

NEURAL ECM SCAFFOLDS

The unique electrochemical connection at synapses is backed up by multiple mechanical connections linking the pre- and postsynaptic membranes to each other
as well as to the surrounding ECM. Because of this intimate link between neurites
and their synapses and the unique 3D architecture of the brain, it is so far impossible
to artificially reconstruct the brain. Nevertheless, in the last part of this volume, we
would like to address the questions how one could mimic a scaffold that can be used
by neurons and glial cells to create neuronal connections that can be used to functionally replace damaged tissues (Estrada, Tekinay, & Mu¨ller, 2014). To do this,
one does not only need to develop ways of creating surfaces or scaffolds, which
would allow the growth of neurites and glia, but also ways to create electrochemical
connections between the healthy brain tissue and implanted neuronal networks, as
discussed by Simi, Amin, Maccione, Nieus, and Berdondini (2014). An alternative
approach to create new functional brain tissue would be to implant neuronal stem
cells in such a way that glial cells and neurons can rebuild the damaged scaffolds.
In order to do this, we require however precise information how a stem cell

xv


xvi

Preface

compartment is maintained and how differentiating neurons can be instructed to migrate, to stop, and to send out axons and dendrites in a stereotype and reproducible
manner. One class of receptors that can read both structural and mechanical information that are preprogrammed within the ECM are integrins. However, to instruct
neuronal or glial cell behavior via the extracellular scaffold, we need to understand
how integrins are mediating adhesion to ECM and provide specific signaling for
neurite extension or maturation of synapses, the aspects discussed by WehrleHaller and Bastmeyer (2014).
This volume is the first book focusing on the neural ECM, which is an attempt to
synthesize the views of basic scientists, medical doctors, and engineers how it works
under normal conditions and in diseased brains and how to repair or reconstitute it.
We expect that this volume will become a reference book for PhD students to facilitate their entry in this complex and dynamic field and will be highly beneficial for

established neuroscientists to better understand the role of ECM in their “favorite”
functions of neural cells, for pharma industry and doctors to include the ECM in the
shortlist of therapeutically attractive targets and for tissue engineers to learn how to
better mimic the complexity of neural ECM and design new functional ECM
scaffolds.
Alexander Dityatev
Magdeburg, Germany
Bernhard Wehrle-Haller
Geneva, Switzerland
Asla Pitka¨nen
Kuopio, Finland

REFERENCES
Baranger, K., Rivera, S., Liechti, F.D., Grandgirard, D., Bigas, J., Seco, J., et al., 2014.
Endogenous and synthetic MMP inhibitors in CNS physiopathology. Prog. Brain Res.
214, 313–351.
Berezin, V., Walmod, P.S., Filippov, M., Dityatev, A., 2014. Targeting of ECM molecules and
their metabolizing enzymes and receptors for the treatment of CNS diseases. Prog. Brain
Res. 214, 353–388.
Estrada, V., Tekinay, A., Mu¨ller, H.W., 2014. Neural ECM mimetics. Prog. Brain Res. 214,
391–413.
Frischknecht, R., Chang, K.-J., Rasband, M.N., Seidenbecher, C.I., 2014. Neural ECM molecules in axonal and synaptic homeostatic plasticity. Prog. Brain Res. 214, 81–100.
Heikkinen, A., Pihlajaniemi, T., Faissner, A., Yuzaki, M., 2014. Neural ECM and synaptogenesis. Prog. Brain Res. 214, 29–51.
Kerrisk, M.E., Cingolani, L.A., Koleske, A.J., 2014. ECM receptors in neuronal structure, synaptic plasticity, and behavior. Prog. Brain Res. 214, 101–131.
Kwok, J.C.F., Yang, S., Fawcett, J.W., 2014. Neural ECM in regeneration and rehabilitation.
Prog. Brain Res. 214, 179–192.


Preface

Lubbers, B.R., Smit, A.B., Spijker, S., van den Oever, M.C., 2014. Neural ECM in addiction,
schizophrenia, and mood disorder. Prog. Brain Res. 214, 263–284.
Milosˇevic´, N.J., Judasˇ, M., Aronica, E., Kostovic, I., 2014. Neural ECM in laminar organization and connectivity development in healthy and diseased human brain. Prog. Brain Res.
214, 159–178.
Morawski, M., Filippov, M., Tzinia, A., Tsilibary, E., Vargova, L., 2014. ECM in brain aging
and dementia. Prog. Brain Res. 214, 207–227.
Pitka¨nen, A., Ndode-Ekane, X.E., Łukasiuk, K., Wilczynski, G.M., Dityatev, A., Walker, M.C.,
et al., 2014. Neural ECM and epilepsy. Prog. Brain Res. 214, 229–262.
Senkov, O., Andjus, P., Radenovic, L., Soriano, E., Dityatev, A., 2014. Neural ECM molecules
in synaptic plasticity, learning and memory. Prog. Brain Res. 214, 53–80.
Simi, A., Amin, H., Maccione, A., Nieus, T., Berdondini, L., 2014. Integration of microstructured scaffolds, neurons and multielectrode arrays. Prog. Brain Res. 214, 415–442.
Theocharidis, U., Long, K., ffrench-Constant, C., Faissner, A., 2014. Regulation of the neural
stem cell compartment by extracellular matrix constituents. Prog. Brain Res. 214, 3–28.
Tsilibary, E., Tzinia, A., Radenovic, L., Stamenkovic, V., Lebitko, T., Mucha, M., et al., 2014.
Neural ECM proteases in learning and synaptic plasticity. Prog. Brain Res. 214, 135–157.
Vandooren, J., Damme, J.V., Ghislain Opdenakker, G., 2014. On the structure and functions of
gelatinase B/matrix metalloproteinase-9 in neuroinflammation. Prog. Brain Res. 214,
193–206.
Wehrle-Haller, B., Bastmeyer, M., 2014. Intracellular signaling and perception of neuronal
scaffold through integrins and their adapter proteins. Prog. Brain Res. 214, 443–460.
Zeug, A., Stawarski, M., Bieganska, K., Korotchenko, S., Wlodarczyk, J., Dityatev, A., et al.,
2014. Current microscopic methods for the neural ECM analysis. Prog. Brain Res. 214,
287–312.

xvii


Brain extracellular matrix meets
COST—Matrix for European
research networks

Srec´ko Gajovic´*,1, Roland Pochet{,2
*Croatian Institute for Brain Research, University of Zagreb School of Medicine, Zagreb, Croatia;
COST Domain Committee Biomedicine and Molecular Biosciences, Rapporteur of COST Action
BM1001—ECMNET: Brain Extracellular Matrix in Health and Disease, Brussels, Belgium
{
Faculte´ de Me´decine, Universite´ Libre de Bruxelles, Brussels, Belgium
1
Corresponding author: Tel.: +358-1-4566948; Fax: +358-1-4566795,
e-mail address:

Abstract
Today’s researchers are faced with a change from curiosity-driven to mandate-driven research.
These two approaches are well combined within scientific networks (Actions) supported by
the European Cooperation in Science and Technology (COST) program. The functioning
of COST Actions, although directed only to networking, has a substantial impact on European
science and can be compared to the functioning of the extracellular matrix in the brain, which
although scarce plays a key role in initiation, maintenance, and plasticity of intercellular interactions in the nervous system. COST networks enable interdisciplinary approach and support early-stage researchers, which is a vital asset for the advancement of science.

Keywords
curiosity-driven research, mandate-driven research, extracellular matrix, interdisciplinarity,
early-stage researchers

Scientists are frequently considered as a distinct group of people, not sharing the
same characteristics as the general population. Although this stereotype is certainly
far from reality, it shapes the public perception. Scientists are perceived as people
with broad knowledge dedicated to solving unresolved issues with persistence and
care of the details. The origin of the stereotype are famous scientists in history
and different fictional or real-life characters described in the literature, movies, theater plays, or newspaper articles. One should note that their success is often considered to be a result of individual effort and a consequence of some of their personality
2

Past Chair of COST Domain Committee Biomedicine and Molecular Biosciences (2010–2013),
Brussels, Belgium.

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Brain extracellular matrix meets COST

features. One of these features is curiosity, and curiosity was agreed as a major driving force of science. This type of research is referred to as curiosity-driven research
or blue-skies research, and today, scientists will strongly defend their scientific freedom and the right to perform research based on their individual curiosity
(Linden, 2008).
On the other hand, today’s science is a complex network of many interacting
elements, which make scientific activities far more demanding than a simple pursuit
of individual curiosities. An opposing approach to curiosity-driven research is
mandate-driven research. The science of today is not only here to provide new
knowledge but also to solve the emerging societal issues and contribute to the societal needs (Svalastog, 2014). The turning point in this process was considered to be
the Manhattan project, when governments of several countries engaged numerous
scientists as well as other professionals in a joint effort to create the first atomic
bombs. The project involved more than 130,000 people and the cost of nearly
US$2 billion (in the 1940s; Web page Wikipedia, 2014: />wiki/Manhattan_Project, as assessed on June 6, 2014).
Although curiosity is an inevitable element of today’s science, it is clear that currently we have a highly expensive system involving many individuals with different
expertise. If we pursue the extracellular matrix in the brain analogy, in order to
achieve the brain complexity, many individual cells should be engaged and their activities should be supported. The brain activities are supported by the activity of the
whole body, which “serves” the brain and which is “governed” by the brain. An important part of this support is provided directly in the brain by the extracellular matrix. As the extracellular matrix in the brain is scarce, at first it was considered as not
very important, but it is more and more recognized as essential component for formation, maintenance, and plasticity of synaptic connections and for concerted action
of neuronal, glial, vascular, and immune cells.
Although the parallels between biological systems and society are only of illustrative nature, they are still worth exploring. The resources used by the today’s science are considerable and need to be justified. Therefore, the mandate-driven
research is frequently imperative for scientists to maintain their activities. The

resource allocation by granting agencies is usually organized on the top-down basis,
where the need is first identified and then the resources are allocated to the project
best fitting to the requested mandate. In this context, the European Union (EU)
defines the needs at the level of the European Parliament and subsequently the
European Commission organizes the granting system (previously Framework
Programmes, currently Horizon 2020), which addresses the predefined needs with
dedicated calls. This rationale is clearly supported by the need to justify the resources
collected from the EU countries and their tax payers. Still it is constantly criticized by
scientific community as it predicts a novelty before it appears, and leaves many
potentially fruitful research lines unrecognized and consequently unfunded. One
of the ways to complement the top-down approach is to apply the bottom-up approach, such as in programs financed through European Commission, the most notable examples of which are COST (European Cooperation in Science and
Technology) and the European Research Council (ERC).


Brain extracellular matrix meets COST

COST was founded in 1971 long before the establishment of the EU in 1993.
Therefore, COST is an intergovernmental organization, governed by the European
member states, some of which are non-EU countries (currently, COST has 34 member states), and Israel as a Cooperating State (Web page COST, 2014: http://www.
cost.eu/, as assessed on June 6, 2014). The operating costs are currently covered by
grants obtained from the European Commission. COST is dedicated to select networks using the bottom-up approach. The basic form of this network is referred
to as an Action, which is granted for a limited time period to achieve its tasks through
networking. Although these tasks could be rather complex, the financing is limited
only to support the networking activities, rather than to provide the resources (e.g.,
equipment and consumables) necessary to achieve this goal. The Action financing is
considered as only a top-up to the existing resources enabling research activities, and
the Action should provide a concerted effort using its other resources to achieve more
than an individual group can do by itself.
It is obvious that the financial contribution of COST Action is scarce in comparison to the total resources used by the Action members. By analogy, it could be considered negligible in the same way that the scarce extracellular matrix was
considered not important for the brain. On the contrary, the cumulative experience

gained throughout the history of COST shows that COST is indeed a very useful instrument supporting European Science and Technology. Achievements of COST
networks are confirmed not only by the so-called tangible results (e.g., number of
joint scientific publications) but also by many intangible benefits, such as cultivating
a spirit of large-scale interdisciplinary research. The opinion of the authors is that
these intangible results are of the outmost importance and have profoundly changed
the European science.
As any study of COST would lack a control group, i.e., a group of countries resembling Europe and without COST, it is impossible to verify the contribution of
COST and difficult to demonstrate the benefits of COST to the European science.
Here, we can use the example of extracellular matrix in the brain showing its importance for coordination of interactions between neurons and other cells, aiming to
maintain cellular networks, while supporting their adaptive functional plasticity.
In the same way, COST Actions have helped European scientists to get to know each
other, communicate, and coordinate their individual efforts toward a joint cooperation. Although Actions are funded for a limited period of time, the strength of these
collaborations is not limited to the Action lifetime, but it lasts long after and continues in different forms of joint activities, many of them not even related to research, but rather to education, regulatory work, entrepreneurship, and novel
economical activities. Very often, the extracellular matrix is formed between cells
of different types/origins and serves to avoid antagonism between them, so to say to
harmonize their relationships. One of the well-known examples is the ECM molecule laminin 11, which is a part of extracellular matrix that prevents invasion of
Schwan cell processes into the synaptic cleft between the motor nerve terminal
and the muscle fiber and thus helps to maintain synaptic transmission (Patton,
Chiu, & Sanes, 1998). Similarly, COST Actions help to avoid competition between
groups by stimulating cooperative activities.

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xxii

Brain extracellular matrix meets COST

One of the COST particularities is the support of interdisciplinary research. In
this context, it is noteworthy that neural extracellular matrix molecules are secreted

by neurons and glial cells and form a structure integrating components derived from
these major cell types. Thus, the extracellular matrix is not just an extension of neurons or glia into the extracellular space but a unique integrative entity, which can
receive and release specific signals in response to cellular activity. Similarly, COST
Actions are composed from experts from different fields that bring their expertize to
address specific scientific and social needs and generate unique knowledge, concepts, and products. Currently, to make substantial scientific breakthroughs is mainly
possible through interdisciplinary efforts. The difficulties to achieve interdisciplinary collaboration are considered as a major obstacle to further scientific advancement (Bennett & Gadlin, 2012). COST Actions are a unique instrument to solve
this issue. The complexity of science clearly dictates the need for specialization,
meaning that every individual can gain only a tiny subset of the total knowledge
and skills. Combining different expertize in a network is an obvious solution, still
the interdisciplinary efforts are difficult to achieve. One of the major obstacles described is a communication problem because different disciplines develop different
approaches and even different vocabularies, hindering the cross talk between disciplines. COST Actions, by gathering experts from different fields, stimulate the cross
talk and offer the dedicated time and recourses to exchange information and opinions. COST Actions also involve early-stage researchers, and it is of outmost importance to allow young researchers to communicate and understand other disciplines.
This can be seen as investment into future that can further promote the advancement
of European science.
To maintain COST networks productivity is not an easy task. It is achieved by
organizing the scientific committees on the basis of the intergovernmental principle.
According to this principle, scientists belonging to the scientific committees could
assist other scientists to develop networks. However, the evaluation and monitoring
system based on standing scientific committees received criticism mainly related to
the standardized procedures and avoidance of conflicts of interest. This is another
aspect of the development of our society, where public institutions simultaneously
promote and undermine general trust (Robbins, 2012). Frequently, to regain trust,
administrative procedures take precedence to free collaboration. Paradoxically,
the system gets complicated, therefore less transparent (opposite to what was
intended to be achieved), and the public trust further weakens. Whether the same will
happen in the future of COST remains to be seen, but it is certain that the current
COST system based on standing scientific evaluation and monitoring committees
will expire in September 2014.
In conclusion, just as the extracellular matrix is essential to functioning of the
brain, the networking of scientists is essential for further advancement of science.

One of the important networking tools is COST, and among the exemplary results
of COST Action networks is the current issue of Progress in Brain Research. We
think that promoting networking and bottom-up approach represents an optimum
balance between curiosity- and mandate-driven research. Networking is a skill that


Brain extracellular matrix meets COST

needs to be developed and that enables the cross talk between the disciplines. Therefore, training of early-stage researchers in networking skills and maintaining functional networks is vital for further advancement of science.

REFERENCES
Bennett, L.M., Gadlin, H., 2012. Collaboration and team science: from theory to practice.
Journal of Investigative Medicine 60, 768–775.
Linden, B., 2008. Basic Blue Skies Research in the UK: Are we losing out? Journal of Biomedical Discovery and Collaboration 3, 3.
Patton, B.L., Chiu, A.Y., Sanes, J.R., 1998. Synaptic laminin prevents glial entry into the synaptic cleft. Nature 393, 698–701.
Robbins, B.G., 2012. A blessing and a curse? Political institutions in the growth and decay of
generalized trust: a cross-national panel analysis, 1980–2009. PLoS One 7, e35120.
Svalastog, A.L., 2014. The value of bio-objects and policy discourses in Europe. Croatian
Medical Journal 55, 167–170.

xxiii


CHAPTER

Regulation of the neural
stem cell compartment by
extracellular matrix
constituents

1

Ursula Theocharidis*, Katherine Long{, Charles ffrench-Constant{,
Andreas Faissner*,1
*Department of Cell Morphology and Molecular Neurobiology, Ruhr-University
Bochum, Bochum, Germany
{
MRC Centre for Regenerative Medicine, The University of Edinburgh, Edinburgh, UK
1
Corresponding author: Tel.: +49-234-3223851; Fax: +49-234-3214313,
e-mail address:

Abstract
Neural stem cells (NSCs) derive from the neuroepithelium of the neural tube, develop into
radial glial cells, and recede at later developmental stages. In the adult, late descendants of
these embryonic NSCs reside in discretely confined areas of the central nervous system,
the stem cell niches. The best accepted canonical niches are the subventricular zone of the
lateral ventricle and the subgranular zone of the dentate gyrus of the hippocampus. Stem cell
niches provide a privileged environment to NSCs that supports self-renewal and maintenance
of this cellular compartment. While numerous studies have highlighted the importance of transcription factors, morphogens, cytokines, and growth factors as intrinsic and extrinsic factors
of stem cell regulation, less attention has been paid to the molecular micromilieu that characterizes the stem cell niches. In this chapter, we summarize increasing evidence that the extracellular matrix (ECM) of the stem cell environment is of crucial importance for the biology of
this cellular compartment. A deeper understanding of the molecular composition of the ECM,
the complementary receptors, and the signal transduction pathways engaged may prove highly
relevant for harnessing NSCs in the context of biotechnological applications.

Keywords
Asymmetrical division, Extracellular matrix, Glial progenitors, Integrins, Laminin, Neural
stem cell niche, Phosphacan, Proteoglycans, Radial glial cells, Subventricular zone, Tenascin

Progress in Brain Research, Volume 214, ISSN 0079-6123, />© 2014 Elsevier B.V. All rights reserved.

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CHAPTER 1 Extracellular matrix and neurogenesis

1 NEUROGENESIS UNFOLDS IN DISTINCT STEPS
AND INVOLVES NEURAL STEM CELLS
The neural plate derives from the neuroectoderm and is composed of a layer of neuroepithelial cells that expand by symmetrical division. With increasing growth of the
neural tube, the neuroepithelium progressively elongates to give rise to radial glial
cells with a radial morphology whose processes span the developing CNS. These radial glia give rise to neurons and glial cells in vivo and thus serve as authentic neural
stem cells (NSCs; Anthony et al., 2004; Hartfuss et al., 2001; Malatesta et al., 2000,
2003; Noctor et al., 2001, 2004). They divide by symmetrical divisions at the inner
(or ventricular) surface of the developing neural tube—the ventricular zone—at early
stages but later on give birth to neurons by switching to an asymmetrical division
mode (Kriegstein and Alvarez-Buylla, 2009; Merkle and Alvarez-Buylla, 2006).
In the classical model of radial glial-guided migration, this cell population has also
been highlighted as a scaffold for migrating neurons (Rakic, 2007). In mammalian
species, neurons may be generated via a population of intermediate progenitors (or
amplifying precursors) that are generated by the asymmetrical stem cell divisions
and then undergo a restricted number of symmetrical divisions so increasing neurogenesis and enabling ongoing cortical expansion (Gotz and Huttner, 2005). In species that are characterized by a substantially enlarged cortical surface such as
primates, additional populations of amplifying precursors are found in a further, distinct neurogenic zone close to the cortical surface, so fueling the further cortical
growth (Fietz and Huttner, 2011; Hansen et al., 2010).
Following neurogenesis, the stem cells switch to the generation of astrocytes and
oligodendrocyte precursors, with the latter migrating to target regions to myelinate
the axonal connections (Nave, 2010). The majority of the radial glia undergo a final
symmetrical division to generate two differentiated daughters and so vanish from the
CNS, with the exception of the Bergmann glia of the cerebellum and the Mu¨ller glia

of the retina. Some descendants of the radial glia, however, persist as radial-type astrocytes that reside in the subventricular zone (SVZ) of the lateral ventricle and the
subgranular zone (SGZ) of the dentate gyrus of the hippocampus. There, the astrocytes act as adult NSCs and serve neurogenesis in the adult CNS (Kriegstein and
Alvarez-Buylla, 2009).

2 MOLECULAR DETERMINANTS OF ASYMMETRICAL DIVISION
The transition from symmetrical to asymmetrical division of radial glia accompanies
the generation of distinct neural cell precursor populations. Asymmetrical division
implies that the daughter cells of a dividing stem cell adopt different fates that are
reflected by distinct patterns of gene expression and consequently differentiation
pathways. Conceptually the differences of the daughter cells could be caused either
by a differential repartition of intrinsic determinants of the dividing stem cell, or,
alternatively, the daughter cells might segregate into different microenvironments
that subsequently would engage specific receptors and drive the progeny into distinct


4 The stem cell niches of the adult CNS

differentiation pathways. Evidence for the selective distribution of intrinsic determinants during stem cell division has been obtained in drosophila, for example, the protein numb (Couturier et al., 2013), male versus female chromosomes, or centrosomes
(Yadlapalli and Yamashita, 2013). In mammalian NSCs, the asymmetrical distribution of apical membranes of radial glia as a consequence of the inclination angle of
the cell division plane has been highlighted (Gotz and Huttner, 2005), as well as the
asymmetrical distribution of centrosome-associated primary cilium membrane
(Paridaen et al., 2013).

3 ENVIRONMENTAL ASYMMETRY AND THE STEM CELL NICHE
The alternative interpretation of divisional asymmetry instructed by different microenvironments that drive the progeny into distinct differentiation pathways emphasizes the influence of the cellular microenvironment. In the adult nervous system,
NSCs are confined to privileged areas, the so-called stem cell niches. Stem cell
niches have been detected in various organs and are characterized by the coexistence
of stem cells, supporting niche cells, the neighborhood of blood vessels, and a specialized extracellular matrix (ECM; Scadden, 2006). In this microenvironment, stem
cells interact with niche cells and other cellular components via membrane-mediated
cell–cell interactions and respond to morphogens, cytokines, and growth factors; to

autocrine, paracrine, and endocrine signals; and to ECM components.

4 THE STEM CELL NICHES OF THE ADULT CNS
In the adult CNS, the two generally accepted canonical regions of neurogenesis are
the SVZ of the lateral ventricle and the SGZ of the hippocampus. It is likely that these
neurogenic areas are characterized by specialized environments that sustain NSCs
and, as in niches elsewhere, function as integrative entities for a large number of
physiological stimuli (Scadden, 2006; Zhao et al., 2008). In the CNS, the specialized
niche microenvironment is constituted by astrocytes, endothelia of blood vessels,
leptomeningeal cells, and the cerebrospinal fluid in the case of the SVZ. Morphogens, cytokines, ECM constituents, and neurotransmitters are released into the niche
environment (Ihrie and Alvarez-Buylla, 2011; Kazanis and ffrench-Constant, 2011;
Patel et al., 2012). In these niches, a subclass of slowly dividing astrocytes (descendants of the radial glia, the major neural stem/progenitor cell (NSPC) of the developing nervous system as described earlier) that express the transcription factor Sox2
and the intermediate filament protein GFAP act as stem cells (Ming and Song, 2005).
These astrocytes are also called type B cells and continuously generate transitamplifying precursors, type C cells, which rapidly expand the cell pool and develop
further to the type A cells, the neuroblasts. These migrate towards the olfactory bulb
through a migration path that is surrounded by (non-stem cell) astrocytes, forming
the rostral migratory stream. The morphogen sonic hedgehog (Shh) supports the

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CHAPTER 1 Extracellular matrix and neurogenesis

proliferation and the maintenance of the neuroblasts. When they reach their target,
these neuroblasts differentiate into dopaminergic interneurons and contribute to the
regeneration of the local olfactory network (Ming and Song, 2011; Zhao et al., 2008).
In the SGZ of the hippocampal dentate gyrus in the adult forebrain (Kempermann
et al., 2004), the granule neurons of the hippocampus are born continuously from the

NSPCs. It has been proposed that this neurogenesis in the hippocampus plays an important role for memory formation (Garthe and Kempermann, 2013). As in the SVZ,
this occurs via the formation of an amplifying precursor population. Here, however,
the cellular and molecular composition of the niche is poorly established although
the observation that increasing blood vessel density in the SGZ increases neurogenesis (Licht et al., 2011) suggests that blood vessels are an important part of the niche
just as they are in the SVZ.
In recent years, increasing evidence has pointed to the versatility and various
functions of the ECM in the NSC compartment. The ECM consists of glycoproteins
and proteoglycans and assembles to selective and specific macromolecular superstructures in the stem cell microenvironment (Barros et al., 2011; Dityatev et al.,
2010; Garwood et al., 2001). A systematic comparison of transcriptomes has underlined that the ECM microenvironment distinguishes the neurogenic zones of the inner and the outer SVZs in the human embryonic brain. The data suggested that cell
adhesion and cell-ECM interactions are relevant for the proliferation and self-renewal
of neural progenitors in the developing human neocortex. Important classes of ECM
molecules that have emerged from expression of the stem and amplifying precursorcontaining regions include tenascins, collagens, laminins, proteoglycans, and the
integrin receptors (Fietz et al., 2012). In particular, the stimulation of the integrin
avb3 promotes the expansion of basal progenitors of the mouse brain by increasing
cell cycle reentry of Pax6-negative and Tbr2-positive intermediate progenitors
(Stenzel et al., 2014). Next, therefore, we will discuss ECM molecules implicated
by prior work in adult neural niches. The primary focus will be the tenascins, after
which we will review the work on laminins, proteoglycans, and ECM receptors.

5 TENASCIN PROTEINS IN THE NSC NICHE
Tenascin-C proteins were among the first identified ECM proteins of the NSC niche
(Gates et al., 1995). The glycoproteins tenascin-C (TN-C), tenascin-R (TN-R),
tenascin-X (TN-X), and tenascin-W (TN-W) of the tenascin gene family share a
set of structural motifs, namely, a cysteine-rich N-terminus, a sequence of fibronectin type III (FNIII) modules, and homologies to fibrinogen-beta at the C-terminus
(Tucker et al., 2006). TN-C was of particular interest because it is transiently
expressed by astrocytes in the developing CNS. There, it is distributed in discrete
boundary-like patterns, for example, in the barrel field of the somatosensory cortex
of the mouse (Faissner and Steindler, 1995). Numerous studies have highlighted repulsive, inhibitory, or stimulatory effects of TN-C on axon growth and guidance and
demonstrated cell type-dependent differences in TN-C responsiveness (Faissner,

5 Tenascin proteins in the NSC niche

1997; Wehrle-Haller and Chiquet, 1993). As a special feature, TN-C monomers comprise alternatively spliced FNIII domains between the fifth domain and the sixth domain of the constitutive structure, up to six motifs in the mouse and nine motifs in the
human (Fig. 1). These domains are spliced independently from one another, which
provides the basis for 2n combinatorial variants with n individual FNIII domains.
Thus, up to 64 combinations are conceivable in the mouse, and 512 variants could
potentially be generated in the human. In fact, 24 variants were found on the mRNA
level in an initial screen in the developing mouse cerebellum ( Joester and Faissner,
1999, 2001; Theocharidis and Faissner, 2012). There is evidence that the combinatorial variants are regulated during development (Rigato et al., 2002) and in response
to lesions (Dobbertin et al., 2010; Garwood et al., 2012). TN-C thus belongs in a category of genes that can generate a large number of variants by alternative splicing of
structural domains, similar to dsCAMs (Zipursky and Sanes, 2010) or to neurexins
(Craig and Kang, 2007). Unlike the latter two that are expressed in neurons, TN-C so
far is the only glial gene with this remarkable characteristic. Tenascin genes seem to
have emerged in urochordates but not in other invertebrate phyla and hence may be

FIGURE 1
Multimodular tenascin-C structure. Tenascin-C appears as oligomeric protein consisting
of six monomers. The monomers show a multimodular structure with an N-terminal cysteinerich assembly domain and 14,5 EGF-like repeats, followed by a number of fibronectin
type III (FNIII) domains. Six of them are constitutively expressed and can be supplemented
with up to six (in the mouse) alternatively spliced FNIII domains. This leads to sequences
of different sizes that have been analyzed in detail (Joester and Faissner, 1999; Theocharidis
and Faissner, 2012; von Holst et al., 2007).

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CHAPTER 1 Extracellular matrix and neurogenesis

specific for chordates (Tucker et al., 2006). Genes with related egf-type repeats have
been described in drosophila, namely, the Tenm genes (Baumgartner et al., 1994).
The N-terminus links tenascin monomers to multimers, for example, TN-C assembles to hexamers under nonreducing conditions that appear as so-called hexabrachions upon electron microscopy of rotary-shadowed preparations (ChiquetEhrismann and Tucker, 2011).
The adult niche of the SVZ is strongly enriched in TN-C where it is expressed by
type B cells and deposited in an area neighboring the ependymal cell layer (Fig. 2). In
the tenascin-CÀ/À knockout, minor structural deficits of the niche could be detected,
the number of stem cells and their progeny however was not affected, and the regeneration of the stem cell compartment upon treatment with cytosine beta-D-arabinofuranoside was not different from the wild type (Kazanis et al., 2007). The astrocytes
surrounding the migrating type A neuroblasts are enriched with TN-C that may keep
the neuroblasts on track by its repulsive properties (Faissner and Kruse, 1990;
Jankovski and Sotelo, 1996). Additionally, in their destination in the olfactory bulb,
the related gene TN-R attracts the neuroblasts out of the stream into the periglomerular networks (Saghatelyan et al., 2004).

6 EXPRESSION OF TENASCIN GENES IN RADIAL GLIA
AND ASTROCYTE PROGENITORS
The expression of TN-C in the adult stem cell niche has led to further studies at earlier developmental stages. In the mouse neural tube, TN-C can be detected at around
E12–E13 and is clearly expressed in radial glia (Fig. 3; Garcion et al., 2001, 2004).
Radial glial cells can be identified with selective markers such as vimentin, BLBP,
GLAST, and nestin. The cells can be cultivated in the model of neurospheres, aggregates of cells in suspension culture that comprise NSPCs and various progenitors.
These neurospheres express TN-C and 20 isoforms were detected on the message
level in cultures derived from embryonic forebrain. Among these, the combination
of FNIII domains A1A4BD was novel and has so far only been found in NSPCs.
Vector-driven overexpression of the paired-box transcription factor Pax6, a transcription factor that is characteristic of radial glia, resulted in enhanced expression
of TN-C variants that contain 4–6 alternatively spliced FNIII domains (von Holst
et al., 2007). In order to study the biological significance of TN-C for NSCs, neurospheres obtained from wild-type and tenascin-CÀ/À knockout mice were compared.
These studies showed that the upregulation of the EGF receptor is delayed in the absence of TN-C, which modifies the response of NSPCs to growth factors. Overall, the
transition from solely FGF2-responsive towards FGF2- and EGF-responsive NSPCs
seems favored by TN-C (Garcion et al., 2004). To understand in more detail potential
underlying genetic mechanisms, gene trap lines of NSPCs were established and exposed to TN-C proteins as stimulus. The analysis of responsive genes revealed that
TN-C represses the expression of Sam68, a member of the STAR family of splicing

factors that binds to several mRNA species. When overexpressed in NSPCs, Sam68