- Since 2012 Alexander Dityatev is the head of the Molecular Neuroplasticity research group at DZNE and a full professo... moreSince 2012 Alexander Dityatev is the head of the Molecular Neuroplasticity research group at DZNE and a full professor at the University of Magdeburg. His group is studying the role of extracellular matrix (ECM) molecules in major brain diseases and develops new strategies to image and target the ECM. The group combines expertise in vitro and in vivo electrophysiology, in vivo two-photon imaging and molecular biology.Alexander Dityatev graduated in Mathematics at the Leningrad State University in 1985. In 1991 he accomplished his PhD in Biology with a thesis on quantal analysis of glutamate release at the Sechenov Institute of Evolutionary Physiology and Biochemistry in Leningrad. In 1992-1996, he worked with Peter Clamann as a postdoctoral fellow at the Department of Physiology, University of Bern, where he studied relationships between the structure and function of synaptic connections in the spinal cord. He then worked with Melitta Schachner as a group leader at the Center for Molecular Neurobiology Hamburg. There Dr. Dityatev with his colleagues uncovered synaptic functions of several cell adhesion and extracellular matrix molecules, such as tenascins, chondroitin sulfate proteoglycans, NCAM, L1, CHL1, and their associated glycans, including HNK-1 and PSA. Many of these functions turned out to involve interplay between recognition molecules and ligand- or voltage gated ion channels, resulting in regulation of perisomatic GABAergic inhibition, hippocampal long-term potentiation/depression and contextual memory. In 2004-2007, Alexander Dityatev was a German Research Foundation Fellow at the University Medical Center Hamburg-Eppendorf. In 2007-2012, being a Senior Researcher at the Italian Institute of Technology (IIT), Dr. Dityatev published several mechanistic studies uncovering how synaptic plasticity and learning are regulated by polysialylated form of NCAM and hyaluronic acid through regulation of extrasynaptic GluN2B receptors and L-type Ca2 channels. In 2010-2014, he was a Chair of COST Action “Brain Extracellular Matrix in Health and Disease”. Dr. Alexander Dityatev co-authored more than 140 papers and 4 patents, and co-edited two books on molecular mechanisms of synaptogenesis and brain ECM.edit
In the brain, Hebbian-type and homeostatic forms of plasticity are affected by neuromodulators like dopamine (DA). Modifications of the perisynaptic extracellular matrix (ECM), which control the functions and mobility of synaptic... more
In the brain, Hebbian-type and homeostatic forms of plasticity are affected by neuromodulators like dopamine (DA). Modifications of the perisynaptic extracellular matrix (ECM), which control the functions and mobility of synaptic receptors as well as the diffusion of transmitters and neuromodulators in the extracellular space, are crucial for the manifestation of plasticity. Mechanistic links between synaptic activation and ECM modifications are largely unknown. Here, we report that neuromodulation via D1-type DA receptors can induce targeted ECM proteolysis specifically at excitatory synapses of rat cortical neurons via proteases ADAMTS-4 and-5. We showed that receptor activation induces increased proteolysis of brevican (BC) and aggrecan, two major constituents of the adult ECM both in vivo and in vitro. ADAMTS immunoreactivity was detected near synapses, and shRNA-mediated knockdown reduced BC cleavage. We have outlined a molecular scenario of how synaptic activity and neuromodulation are linked to ECM rearrangements via increased cAMP levels, NMDA receptor activation, and intracellular calcium signaling.
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 extracellular matrix determines their polarity, their shape, form and is providing cues... more
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 extracellular matrix determines their polarity, their shape, 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 needs 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 organisation 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 CNS elements. To overcome this, a European consorcium „Brain Extracellular Matrix in Health and Disease (ECMNet)“ was established in 2010 with a support 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 (http://www.costbm1001.eu/). Each book chapter of this volume is prepared involving ECMNet members and other leading experts from USA and Japan. The chapters cover the broad range of topics, grouped into 4 Parts, which are devoted to normal physiological functions of neural ECM, its role in brain diseases, development of methods to image the ECM and therapeutically target it, and to generation of artificial ECM.
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 CNS elements. To overcome this, a European consorcium „Brain Extracellular Matrix in Health and Disease (ECMNet)“ was established in 2010 with a support 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 (http://www.costbm1001.eu/). Each book chapter of this volume is prepared involving ECMNet members and other leading experts from USA and Japan. The chapters cover the broad range of topics, grouped into 4 Parts, which are devoted to normal physiological functions of neural ECM, its role in brain diseases, development of methods to image the ECM and therapeutically target it, and to generation of artificial ECM.
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INTRODUCTIONHyperphosphorylation and aggregation of the microtubule‐associated protein tau cause the development of tauopathies, such as Alzheimer's disease and frontotemporal dementia (FTD). We recently uncovered a causal link... more
INTRODUCTIONHyperphosphorylation and aggregation of the microtubule‐associated protein tau cause the development of tauopathies, such as Alzheimer's disease and frontotemporal dementia (FTD). We recently uncovered a causal link between constitutive serotonin receptor 7 (5‐HT7R) activity and pathological tau aggregation. Here, we evaluated 5‐HT7R inverse agonists as novel drugs in the treatment of tauopathies.METHODSBased on structural homology, we screened multiple approved drugs for their inverse agonism toward 5‐HT7R. Therapeutic potential was validated using biochemical, pharmacological, microscopic, and behavioral approaches in different cellular models including tau aggregation cell line HEK293 tau bimolecular fluorescence complementation, primary mouse neurons, and human induced pluripotent stem cell–derived neurons carrying an FTD‐associated tau mutation as well as in two mouse models of tauopathy.RESULTSAntipsychotic drug amisulpride is a potent 5‐HT7R inverse agonist. Amisulpride ameliorated tau hyperphosphorylation and aggregation in vitro. It further reduced tau pathology and abrogated memory impairment in mice.DISCUSSIONAmisulpride may be a disease‐modifying drug for tauopathies.
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Research Interests: Neuroscience, Chemistry, Polysaccharides, Biological Chemistry, Medicine, and 15 moreBiological Sciences, Brain, Mice, Animals, Propionic Acid, Biological, Neurons, CHEMICAL SCIENCES, Rats, Receptor, Lipid bilayers, Polysialic Acid, Sialic Acids, Neural Cell Adhesion Molecules, and Medical and Health Sciences
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Research Interests: Neuroscience, Psychology, Fear, Long Term Potentiation, Medicine, and 15 moreSynaptic Plasticity, Neuroplasticity, Memory Consolidation, Memory, Hippocampus, Mice, Female, Animals, Male, Fear conditioning, Polysialic Acid, Sialic Acids, Hippocampal formation, Psychology and Cognitive Sciences, and Medical and Health Sciences
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The neural cell adhesion molecule NCAM and its associated polysialic acid (PSA) play important roles in synaptic plasticity in the CA1 and/or CA3 regions of the hippocampus in vitro. Here, we address the question of whether NCAM and PSA... more
The neural cell adhesion molecule NCAM and its associated polysialic acid (PSA) play important roles in synaptic plasticity in the CA1 and/or CA3 regions of the hippocampus in vitro. Here, we address the question of whether NCAM and PSA are involved in regulation of synaptic transmission and plasticity also in vivo at synapses formed by entorhinal cortex axons in the dentate gyrus of mice anaesthetized with urethane. We show that basal synaptic transmission, measured as the slope of field excitatory postsynaptic potentials, was reduced strongly in mice lacking ST8SiaII/STX, the enzyme involved in polysialylation of NCAM in stem cell‐derived immature granule cells, but not in mice deficient either in the NCAM glycoprotein or the enzyme ST8SiaIV/PST involved in polysialylation of NCAM in mature neurons. Strikingly, only mice deficient in NCAM, but not in PST or STX, were impaired in long‐term potentiation (LTP) induced by theta‐burst stimulation, suggesting that LTP in the dentate gyrus depends on the NCAM glycoprotein alone rather than on its associated PSA. As also patterns of synaptic activity during and immediately after induction of LTP were impaired in NCAM‐deficient mice, it is likely that induction of LTP requires NCAM. These data are the first to describe that NCAM is necessary for induction of synaptic plasticity in identified synapses in vivo and suggest that polysialylation of NCAM expressed by immature granule cells in the dentate gyrus supports development of basal excitatory synaptic transmission in this region.
Research Interests: Neuroscience, Psychology, Cognitive Science, Chemistry, Long Term Potentiation, and 15 moreCell Adhesion, Medicine, Synaptic Plasticity, Mice, Animals, Neuronal Plasticity, Dentate Gyrus, European, SYNAPSES, Electrodes, Polysialic Acid, Neurosciences, Excitatory Postsynaptic Potentials, Neural Cell Adhesion Molecules, and Electric stimulation
Although the extracellular matrix plays an important role in regulating use-dependent synaptic plasticity, the underlying molecular mechanisms are poorly understood. Here, we examined the synaptic function of hyaluronic acid (HA), a major... more
Although the extracellular matrix plays an important role in regulating use-dependent synaptic plasticity, the underlying molecular mechanisms are poorly understood. Here, we examined the synaptic function of hyaluronic acid (HA), a major element of the extracellular matrix. Enzymatic removal of HA with hyaluronidase reduced nifedipine-sensitive whole-cell Ca2+ currents and Ca2+ transients mediated by L-type voltage-dependent Ca2+ channels (L-VDCCs) in individual dendritic shafts and spines of CA1 pyramidal cells, and abolished an L-VDCC-dependent component of long-term potentiation (LTP) at the CA3-CA1 synapses. Adding exogenous HA, either by bath perfusion or via local delivery near to recorded synapses, completely rescued this LTP component. In a heterologous expression system, HA increased currents mediated by Cav1.2 but not Cav1.3 subunit-containing L-VDCCs. Injection of hyaluronidase in the brain impaired contextual fear conditioning. Our observations unveil a previously unrecognized mechanism by which the perisynaptic HA-rich extracellular matrix influences use-dependent synaptic plasticity through regulation of dendritic Ca2+ channels
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Cannabis use during pregnancy has increased by 62% from 2002 through 2014 and is now the most commonly used illicit drug during pregnancy, in part due to its ability to reduce morning sickness duri...
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The condensed form of neural extracellular matrix (ECM), perineuronal nets (PNNs), is predominantly associated with parvalbumin-expressing (PV+) interneurons in the cortex and hippocampus. PNNs are enriched in several lecticans, including... more
The condensed form of neural extracellular matrix (ECM), perineuronal nets (PNNs), is predominantly associated with parvalbumin-expressing (PV+) interneurons in the cortex and hippocampus. PNNs are enriched in several lecticans, including neurocan (Ncan). A polymorphism in the humanNcangene has been associated with alterations in hippocampus-dependent memory function, variation of prefrontal cortex structure, and a higher risk for schizophrenia or bipolar disorder. Ncan knockout (KO) mice show related behavioral abnormalities, such as hyperactivity. Here we focused on studying how dysregulation of Ncan specifically in the mPFC may affect cognitive and synaptic functions. Intracortical adeno-associated virus (AAV) delivery was used to express shRNA against Ncan. Analysis of PNNs in Ncan shRNA-injected mice revealed a reduction in PNNs labelling byWisteria floribundaagglutinin (WFA) around PV+ interneurons. Reduced Ncan expression resulted in a loss of the mPFC-dependent temporal orde...
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The neuronal intracellular chloride concentration [Cl−]iis critical for γ-aminobutyric acid type A (GABAA) receptor-mediated transmission. Degradation of the extracellular matrix (ECM) is associated with raised [Cl−]ibut neither the... more
The neuronal intracellular chloride concentration [Cl−]iis critical for γ-aminobutyric acid type A (GABAA) receptor-mediated transmission. Degradation of the extracellular matrix (ECM) is associated with raised [Cl−]ibut neither the mechanisms underlying this effect nor the consequences for GABA-mediated transmission are well understood. Hitherto it has been unclear how to reconcile the effect of the ECM on [Cl−]iwith the established role of cation-chloride cotransporters in setting [Cl−]i. In the present work we clarify the role of the ECM in the control of neuronal [Cl−]i. By measuring [Cl−]iin central neurons from male rats we show that the ECM affects basal [Cl−]ias well as the rate of Cl−extrusion after a high load. The mechanism is not via impermeant anions but through regulation of K+-Cl−-cotransporter 2 (KCC2). ECM degradation is accompanied by an N-type Ca2+-channel- and calpain-dependent reduction in the amount of KCC2 protein, increased basal [Cl−]i, reduced Cl−extrusion ...
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The ability to form precise, episodic memories develops with age, with young children only able to form gist-like memories that lack precision. The cellular and molecular events in the developing hippocampus that underlie the emergence of... more
The ability to form precise, episodic memories develops with age, with young children only able to form gist-like memories that lack precision. The cellular and molecular events in the developing hippocampus that underlie the emergence of precise, episodic-like memory formation are unclear. In mice, the absence of a competitive neuronal engram allocation process in the immature hippocampus precluded the formation of sparse engrams and precise memories until the fourth postnatal week, when inhibitory circuits in the hippocampus mature. This age-dependent shift in precision of episodic-like memories involved the functional maturation of parvalbumin-expressing interneurons in subfield CA1 by extracellular perineuronal nets which is necessary and sufficient for the onset of competitive neuronal allocation, sparse engram formation, and memory precision.One-Sentence SummaryEpisodic-like memory precision requires maturation of hippocampal inhibitory interneurons by the extracellular matrix.
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BackgroundThe pathological alterations of small arteries and capillaries defined as cerebral small vessel disease (CSVD) are characterized by age-dependent blood-brain barrier (BBB) breakdown and vessel wall remodeling manifesting in... more
BackgroundThe pathological alterations of small arteries and capillaries defined as cerebral small vessel disease (CSVD) are characterized by age-dependent blood-brain barrier (BBB) breakdown and vessel wall remodeling manifesting in small vessel occlusions and perivascular bleeds. As collagen XVIII (Col18a1) is an abundant heparan sulfate proteoglycan in vascular basement membranes, we focused on studying the role of collagen XVIII in vascular integrity and neurovascular unit maintenance in the context of CSVD.MethodsIn this study, we examined BBB breakdown, neuroinflammation and (peri)synaptic protein alterations using immunohistochemistry in 5- and 12-month-old Col18a1-/- and Col18a1+/+ mice. To further characterize molecular alterations, we used qPCR and compared the expression levels of major genes encoding tight junction and basement membrane proteins, inflammatory markers, neural extracellular matrix (ECM) proteins and proteinases.ResultsOur immunohistochemical analysis revea...
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Neurotrypsin (NT) is a neuronal trypsin-like serine protease whose mutations cause severe mental retardation in humans. NT is activated by Hebbian-like conjunction of pre- and postsynaptic activities, which promotes the formation of... more
Neurotrypsin (NT) is a neuronal trypsin-like serine protease whose mutations cause severe mental retardation in humans. NT is activated by Hebbian-like conjunction of pre- and postsynaptic activities, which promotes the formation of dendritic filopodia via proteolytic cleavage of the proteoglycan agrin. Here, we investigated the functional importance of this mechanism for synaptic plasticity, learning and extinction of memory. We report that juvenile neurotrypsin-deficient (NT-/-) mice exhibit impaired long-term potentiation induced by a spaced stimulation protocol designed to probe the generation of new filopodia and their conversion into functional synapses. Behaviorally, juvenile NT-/- mice show impaired contextual fear memory and have a sociability deficit. The latter persists in aged NT-/- mice, which, unlike juvenile mice, show normal recall but impaired extinction of contextual fear memories. Structurally, juvenile mutants exhibit significantly reduced spine density in the CA...
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Background The metabolic syndrome is a consequence of modern lifestyle that causes synaptic insulin resistance and cognitive deficits and that in interaction with a high amyloid load is an important risk factor for Alzheimer's... more
Background The metabolic syndrome is a consequence of modern lifestyle that causes synaptic insulin resistance and cognitive deficits and that in interaction with a high amyloid load is an important risk factor for Alzheimer's disease. It has been proposed that neuroinflammation might be an intervening variable, but the underlying mechanisms are currently unknown. Methods We utilized primary neurons to induce synaptic insulin resistance as well as a mouse model of high-risk aging that includes a high amyloid load, neuroinflammation, and diet-induced obesity to test hypotheses on underlying mechanisms. Results We found that neddylation and subsequent activation of cullin-RING ligase complexes induced synaptic insulin resistance through ubiquitylation and degradation of the insulin-receptor substrate IRS1 that organizes synaptic insulin signaling. Accordingly, inhibition of neddylation preserved synaptic insulin signaling and rescued memory deficits in mice with a high amyloid loa...
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A.N. Balashova, Postgraduate, the Department of Neurodynamics and Neurobiology1; A.E. Dityatev, PhD, Professor, Group Leader2; Head of the Brain Matrix Research Laboratory1; I.V. Mukhina, D.Bio.Sc., Professor, Head of Central Scientific... more
A.N. Balashova, Postgraduate, the Department of Neurodynamics and Neurobiology1; A.E. Dityatev, PhD, Professor, Group Leader2; Head of the Brain Matrix Research Laboratory1; I.V. Mukhina, D.Bio.Sc., Professor, Head of Central Scientific Research Laboratory of Scientific Research Institute of Applied and Fundamental Medicine3; Head of the Department of Normal Physiology3; Professor of the Department of Neurodynamics and Neurobiology1; Researcher of the Brain Matrix Research Laboratory1
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While high risk of failure is an inherent part of developing innovative therapies, it can be reduced by adherence to evidence-based rigorous research practices. Supported through the European Union’s Innovative Medicines Initiative, the... more
While high risk of failure is an inherent part of developing innovative therapies, it can be reduced by adherence to evidence-based rigorous research practices. Supported through the European Union’s Innovative Medicines Initiative, the EQIPD consortium has developed a novel preclinical research quality system that can be applied in both public and private sectors and is free for anyone to use. The EQIPD Quality System was designed to be suited to boost innovation by ensuring the generation of robust and reliable preclinical data while being lean, effective and not becoming a burden that could negatively impact the freedom to explore scientific questions. EQIPD defines research quality as the extent to which research data are fit for their intended use. Fitness, in this context, is defined by the stakeholders, who are the scientists directly involved in the research, but also their funders, sponsors, publishers, research tool manufacturers, and collaboration partners such as peers i...
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SummaryThe brain extracellular matrix (ECM) assembles around neurons and synapses, and is thought to change only rarely, through proteolysis and renewed protein synthesis. We report here an alternative ECM remodeling mechanism, based on... more
SummaryThe brain extracellular matrix (ECM) assembles around neurons and synapses, and is thought to change only rarely, through proteolysis and renewed protein synthesis. We report here an alternative ECM remodeling mechanism, based on the recycling of ECM molecules. We found that a key ECM protein, Tenascin-R, is frequently endocytosed, and later resurfaces, preferentially near synapses. The TNR molecules complete this cycle within ∼3 days, in an activity-dependent fashion.
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LGI1 (Leucine-Rich Glioma-Inactivated 1) is a secreted trans-synaptic protein that interacts presynaptically with Kv1.1 potassium channels and ADAM23, and postsynaptically, influencing AMPA receptors through a direct link with the ADAM22... more
LGI1 (Leucine-Rich Glioma-Inactivated 1) is a secreted trans-synaptic protein that interacts presynaptically with Kv1.1 potassium channels and ADAM23, and postsynaptically, influencing AMPA receptors through a direct link with the ADAM22 cell adhesion protein. Haploinsufficiency of LGI1 or autoantibodies directed against LGI1 are associated with human epilepsy, generating the hypothesis that a subacute reduction of LGI1 is sufficient to increase network excitability. We tested this hypothesis in ex vivo hippocampal slices and in neuronal cultures, by subacutely reducing LGI1 expression with shRNA. Injection of shRNA-LGI1 in the hippocampus increased dentate granule cell excitability and low frequency facilitation of mossy fibers to CA3 pyramidal cell neurotransmission. Application of the Kv1 family blocker, alpha-dendrotoxin, occluded this effect, implicating the involvement of Kv1.1. This subacute reduction of LGI1 was also sufficient to increase neuronal network activity in neuron...
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Inspired from plant medicine, a drug that partially compensates for memory decline in aged flies and mice is identified.
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Neurotrypsin (NT) is a neuronal trypsin-like serine protease whose mutations cause severe mental retardation in humans. NT is activated in vitro by Hebbian-like conjunction of pre- and postsynaptic activities, which promotes the formation... more
Neurotrypsin (NT) is a neuronal trypsin-like serine protease whose mutations cause severe mental retardation in humans. NT is activated in vitro by Hebbian-like conjunction of pre- and postsynaptic activities, which promotes the formation of dendritic filopodia via proteolytic cleavage of the proteoglycan agrin. Here, we investigated the functional importance of this mechanism for synaptic plasticity, learning, and extinction of memory. We report that juvenile neurotrypsin-deficient (NT−/−) mice exhibit impaired long-term potentiation induced by a spaced stimulation protocol designed to probe the generation of new filopodia and their conversion into functional synapses. Behaviorally, juvenile NT−/− mice show impaired contextual fear memory and have a sociability deficit. The latter persists in aged NT−/− mice, which, unlike juvenile mice, show normal recall but impaired extinction of contextual fear memories. Structurally, juvenile mutants exhibit reduced spine density in the CA1 re...
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Our previous studies demonstrated that enzymatic removal of highly sulfated heparan sulfates with heparinase 1 impaired axonal excitability and reduced expression of ankyrin G at the axon initial segments in the CA1 region of the... more
Our previous studies demonstrated that enzymatic removal of highly sulfated heparan sulfates with heparinase 1 impaired axonal excitability and reduced expression of ankyrin G at the axon initial segments in the CA1 region of the hippocampus ex vivo, impaired context discrimination in vivo, and elevated Ca2+/calmodulin-dependent protein kinase II (CaMKII) activity in vitro. Here, we show that in vivo delivery of heparinase 1 in the CA1 region of the hippocampus elevated autophosphorylation of CaMKII 24 hours after injection in mice. Patch-clamp recording in CA1 neurons revealed no significant heparinase effects on the amplitude or frequency of miniature excitatory and inhibitory postsynaptic currents, while the threshold for action potential generation was increased and fewer spikes were generated in response to current injection. Delivery of heparinase on the next day after contextual fear conditioning induced context overgeneralization 24 hours after injection. Co-administration o...
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Understanding changes in the expression of genes involved in regulating various components of the neural extracellular matrix (ECM) during aging can provide an insight into aging-associated decline in synaptic and cognitive functions.... more
Understanding changes in the expression of genes involved in regulating various components of the neural extracellular matrix (ECM) during aging can provide an insight into aging-associated decline in synaptic and cognitive functions. Hence, in this study, we compared the expression levels of ECM-related genes in the hippocampus of young, aged and very aged mice. ECM gene expression was downregulated, despite the accumulation of ECM proteoglycans during aging. The most robustly downregulated gene was carbohydrate sulfotransferase 3 (Chst3), the enzyme responsible for the chondroitin 6-sulfation (C6S) of proteoglycans. Further analysis of epigenetic mechanisms revealed a decrease in H3K4me3, three methyl groups at the lysine 4 on the histone H3 proteins, associated with the promoter region of the Chst3 gene, resulting in the downregulation of Chst3 expression in non-neuronal cells. Cluster analysis revealed that the expression of lecticans—substrates of CHST3—is tightly co-regulated ...
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The extracellular matrix (ECM) plays a key role in synaptogenesis and the regulation of synaptic functions in the central nervous system. Recent studies revealed that in addition to dopaminergic and serotoninergic neuromodulatory systems,... more
The extracellular matrix (ECM) plays a key role in synaptogenesis and the regulation of synaptic functions in the central nervous system. Recent studies revealed that in addition to dopaminergic and serotoninergic neuromodulatory systems, microglia also contribute to the regulation of ECM remodeling. In the present work, we investigated the physiological role of microglia in the remodeling of perineuronal nets (PNNs), predominantly associated with parvalbumin-immunopositive (PV+) interneurons, and the perisynaptic ECM around pyramidal neurons in the hippocampus. Adult mice were treated with PLX3397 (pexidartinib), as the inhibitor of colony-stimulating factor 1 receptor (CSF1-R), to deplete microglia. Then, confocal analysis of the ECM and synapses was performed. Although the elimination of microglia did not alter the overall number or intensity of PNNs in the CA1 region of the hippocampus, it decreased the size of PNN holes and elevated the expression of the surrounding ECM. In the...
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For some time, it has been accepted that the β-site APP cleaving enzyme 1 (BACE1) and the γ-secretase are two main players in the amyloidogenic processing of the β-amyloid precursor protein (APP). Recently, the membrane-type 5 matrix... more
For some time, it has been accepted that the β-site APP cleaving enzyme 1 (BACE1) and the γ-secretase are two main players in the amyloidogenic processing of the β-amyloid precursor protein (APP). Recently, the membrane-type 5 matrix metalloproteinase (MT5-MMP/MMP-24), mainly expressed in the nervous system, has been highlighted as a new key player in APP-processing, able to stimulate amyloidogenesis and also to generate a neurotoxic APP derivative. In addition, the loss of MT5-MMP has been demonstrated to abrogate pathological hallmarks in a mouse model of Alzheimer’s disease (AD), thus shedding light on MT5-MMP as an attractive new therapeutic target. However, a more comprehensive analysis of the role of MT5-MMP is necessary to evaluate how its targeting affects neurons and glia in pathological and physiological situations. In this study, leveraging on CRISPR-Cas9 genome editing strategy, we established cultures of human-induced pluripotent stem cells (hiPSC)-derived neurons and a...
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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 extracellular matrix determines their polarity, their shape, form and is providing cues... more
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 extracellular matrix determines their polarity, their shape, 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 needs 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 organisation 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 CNS elements. To overcome this, a European consorcium „Brain Extracellular Matrix in Health and Disease (ECMNet)“ was established in 2010 with a support 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 (http://www.costbm1001.eu/). Each book chapter of this volume is prepared involving ECMNet members and other leading experts from USA and Japan. The chapters cover the broad range of topics, grouped into 4 Parts, which are devoted to normal physiological functions of neural ECM, its role in brain diseases, development of methods to image the ECM and therapeutically target it, and to generation of artificial ECM.
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Expression of the neural cell adhesion molecule (NCAM) has been shown to promote long-term potentiation (LTP) and stabilization of synapses during early synaptogenesis. Here, we searched for the mechanisms of synaptogenic activity of... more
Expression of the neural cell adhesion molecule (NCAM) has been shown to promote long-term potentiation (LTP) and stabilization of synapses during early synaptogenesis. Here, we searched for the mechanisms of synaptogenic activity of NCAM, focusing on the role of polysialic acid (PSA), an unusual carbohydrate preferentially associated with NCAM. We show that enzymatic removal of PSA with endoneuraminidase-N (endo-N) abolished preferential formation of synapses on NCAM-expressing cells in heterogenotypic cocultures of wild-type and NCAM-deficient hippocampal neurons. Transfection of NCAM-deficient neurons with either of three major NCAM isoforms (different in intracellular domains but identical in extracellular domains and carrying PSA) stimulated preferential synapse formation on NCAM isoform-expressing neurons. Enzymatic removal of heparan sulfates from cultured neurons and a mutation in the heparin-binding domain of NCAM diminished synaptogenic activity of neuronally expressed PSA...
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In the advanced stages of Alzheimer's disease (AD), microglia are transformed to an activated phenotype with thickened and retracted processes, migrate to the site of amyloid‐beta (Aβ) plaques, and proliferate. In the early stages of... more
In the advanced stages of Alzheimer's disease (AD), microglia are transformed to an activated phenotype with thickened and retracted processes, migrate to the site of amyloid‐beta (Aβ) plaques, and proliferate. In the early stages of AD, it is still poorly understood whether the microglial function is altered and which factors may regulate these changes. Here, we focused on studying microglia in the retrosplenial cortex (RSC) in 3‐ to 4‐month‐old 5xFAD mice as a transgenic mouse model of AD. At this age, there are neither Aβ plaques, nor activation of microglia, nor dysregulation in the expression of genes encoding major extracellular matrix (ECM) molecules or extracellular proteases in the RSC. Still, histochemical evaluation of the fine structure of neural ECM revealed increased levels of Wisteria floribunda agglutinin labeling in holes of perineuronal nets and changes in the perimeter of ECM barriers around the holes in 5xFAD mice. Two‐photon vital microscopy demonstrated normal morphology and resting motility of microglia but strongly diminished number of microglial cells that migrated to the photolesion site in 5xFAD mice. Enzymatic digestion of ECM by chondroitinase ABC (ChABC) ameliorated this defect. Accordingly, the characterization of cell surface markers by flow cytometry demonstrated altered expression of microglial CD45. Moreover, ChABC treatment reduced the invasion of myeloid‐derived mononuclear cells into the RSC of 5xFAD mice. Hence, the migration of both microglia and myeloid cells is altered during the early stages of amyloidosis and can be restored at least partially by the attenuation of the ECM.
Research Interests: Glia and Neurosciences
Vascular damage, central nervous system (CNS) injury, seizure or even psychological stress may trigger activation of microglia and infiltration of other immune cells, accompanied by high levels of expression and activity of extracellular... more
Vascular damage, central nervous system (CNS) injury, seizure or even psychological stress may trigger activation of microglia and infiltration of other immune cells, accompanied by high levels of expression and activity of extracellular proteases, such as matrix metalloproteinases (MMPs), and degradation/remodelling of the perivascular and perineuronal extracellular matrix (ECM). This acute response is followed by the recovery/chronic phase, during which the activation of astrocytes leads to the upregulated synthesis of ECM molecules, which, in combination with elevated expression of tissue inhibitor of metalloproteinases (TIMP) proteins, increases the aggregation of ECM molecules. This biphasic dysregulation of local balance between extracellular proteases and the ECM activates multiple temporally overlapping signalling cascades, involving receptor‐type protein tyrosine phosphatases, integrins, Toll‐like receptors, cell adhesion molecules, and ion channels, resulting in impaired synaptic plasticity and cognition. An additional level of complexity is related to the leakage of blood plasma proteins, such as fibrinogen, and the diffusion of perivascularly overproduced MMPs, TIMPs and ECM molecules into the CNS parenchyma, leading to diverse effects on neurons and incorporation of these molecules into the interstitial neural ECM. This review aims to outline these complex common mechanisms in stroke, CNS injury, depression, epilepsy, multiple sclerosis and cerebral small vessel disease and to discuss translational strategies to advance the development of new therapies for these neurological and psychiatric diseases.
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Microglia continuously monitor synapses, but active synaptic remodeling by microglia in mature healthy brains is rarely directly observed. We performed targeted photoablation of single synapses in mature transgenic mice expressing... more
Microglia continuously monitor synapses, but active synaptic remodeling by microglia in mature healthy brains is rarely directly observed. We performed targeted photoablation of single synapses in mature transgenic mice expressing fluorescent labels in neurons and microglia. The photodamage focally increased the duration of microglia-neuron contacts, and dramatically exacerbated both the turnover of dendritic spines and presynaptic boutons as well as the generation of new filopodia originating from spine heads or boutons. The results of microglia depletion confirmed that elevated spine turnover and the generation of presynaptic filopodia are microglia-dependent processes.
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Perineuronal nets (PNNs) represent a highly condensed specialized form of brain extracellular matrix (ECM) enwrapping mostly parvalbumin‐positive interneurons in the brain in a mesh‐like fashion. PNNs not only regulate the onset and... more
Perineuronal nets (PNNs) represent a highly condensed specialized form of brain extracellular matrix (ECM) enwrapping mostly parvalbumin‐positive interneurons in the brain in a mesh‐like fashion. PNNs not only regulate the onset and completion of the critical period during postnatal brain development, control cell excitability, and synaptic transmission but are also implicated in several brain disorders including schizophrenia. Holes in the perineuronal nets, harboring the synaptic contacts, along with hole‐surrounding ECM barrier can be viewed as PNN compartmentalization units that might determine the properties of synapses and heterosynaptic communication. In this study, we developed a novel open‐source script for Fiji (ImageJ) to semi‐automatically quantify structural alterations of PNNs such as the number of PNN units, area, mean intensity of PNN marker expression in 2D and 3D, shape parameters of PNN units in the ketamine‐treated Sprague–Dawley rat model of schizophrenia using high‐resolution confocal microscopic images. We discovered that the mean intensity of ECM within PNN units is inversely correlated with the area and the perimeter of the PNN holes. The intensity, size, and shape of PNN units proved to be three major principal factors to describe their variability. Ketamine‐treated rats had more numerous but smaller and less circular PNN units than control rats. These parameters allowed to correctly classify individual PNNs as derived from control or ketamine‐treated groups with ≈85% reliability. Thus, the proposed multidimensional analysis of PNN units provided a robust and comprehensive morphometric fingerprinting of fine ECM structure abnormalities in the experimental model of schizophrenia.
Research Interests:
In the brain, Hebbian-type and homeostatic forms of plasticity are affected by neuromodulators like dopamine (DA). Modifications of the perisynaptic extracellular matrix (ECM), which control the functions and mobility of synaptic... more
In the brain, Hebbian-type and homeostatic forms of plasticity are affected by neuromodulators like dopamine (DA). Modifications of the perisynaptic extracellular matrix (ECM), which control the functions and mobility of synaptic receptors as well as the diffusion of transmitters and neuromodulators in the extracellular space, are crucial for the manifestation of plasticity. Mechanistic links between synaptic activation and ECM modifications are largely unknown. Here, we report that neuromodulation via D1-type DA receptors can induce targeted ECM proteolysis specifically at excitatory synapses of rat cortical neurons via proteases ADAMTS-4 and -5. We showed that receptor activation induces increased proteolysis of brevican (BC) and aggrecan, two major constituents of the adult ECM both in vivo and in vitro. ADAMTS immunoreactivity was detected near synapses, and shRNA-mediated knockdown reduced BC cleavage. We have outlined a molecular scenario of how synaptic activity and neuromodu...
Research Interests:
Activity-dependent remodeling of excitatory connections underpins memory formation in the brain. Serotonin receptors are known to contribute to such remodeling, yet the underlying molecular machinery remains poorly understood. Here, we... more
Activity-dependent remodeling of excitatory connections underpins memory formation in the brain. Serotonin receptors are known to contribute to such remodeling, yet the underlying molecular machinery remains poorly understood. Here, we employ high-resolution time-lapse FRET imaging in neuroblastoma cells and neuronal dendrites to establish that activation of serotonin receptor 5-HT4 (5-HT4R) rapidly triggers spatially-restricted RhoA activity and G13-mediated phosphorylation of cofilin, thus locally boosting the filamentous actin fraction. In neuroblastoma cells, this leads to cell rounding and neurite retraction. In hippocampal neurons in situ, 5-HT4R-mediated RhoA activation triggers maturation of dendritic spines. This is paralleled by RhoA-dependent, transient alterations in cell excitability, as reflected by increased spontaneous synaptic activity, apparent shunting of evoked synaptic responses, and enhanced long-term potentiation of excitatory transmission. The 5-HT4R/G13/RhoA...
Research Interests:
Research Interests:
Neuronal synapses undergo structural and functional changes throughout life, essential for nervous system physiology. However, these changes may also perturb the excitatory/inhibitory neurotransmission balance and trigger neuropsychiatric... more
Neuronal synapses undergo structural and functional changes throughout life, essential for nervous system physiology. However, these changes may also perturb the excitatory/inhibitory neurotransmission balance and trigger neuropsychiatric and neurological disorders. Molecular tools to restore this balance are highly desirable. Here, we report the design and characterization of CPTX, a synthetic synaptic organizer combining structural elements from cerebellin-1 and neuronal pentraxin-1 to interact with presynaptic neurexins and postsynaptic AMPA-type ionotropic glutamate receptors. CPTX induced the formation of excitatory synapses in vitro and in vivo and restored synaptic functions, motor coordination, spatial and contextual memories, and locomotion in mouse models for cerebellar ataxia, Alzheimer’s disease and spinal cord injury, respectively. Thus, CPTX represents a prototype for novel structure-guided biologics that can efficiently repair or remodel neuronal circuits.One Sentence...