Gerald Seifert

University of Bonn | Uni Bonn · Institute of Cellular Neurosciences

NG2 glia represents a distinct type of macroglial cells in the CNS and is unique among glia because they receive synaptic input from neurons. They are abundantly present in white and gray matter. While the majority of white matter NG2 glia differentiates into oligodendrocytes, the physiological impact of gray matter NG2 glia and their synaptic inpu...

Extensive microglia reactivity has been well described in human and experimental temporal lobe epilepsy (TLE). To date, however, it is not clear whether and based on which molecular mechanisms microglia contribute to the development and progression of focal epilepsy. Astroglial gap junction coupled networks play an important role in regulating neur...

The neurovascular unit (NVU) consists of cells intrinsic to the vessel wall, the endothelial cells and pericytes, and astrocyte endfeet that surround the vessel but are separated from it by basement membrane. Endothelial cells are primarily responsible for creating and maintaining blood–brain-barrier (BBB) tightness, but astrocytes contribute to th...

The neurovascular unit (NVU) consists of cells intrinsic to the vessel wall, the endothelial cells and pericytes, and astrocyte endfeet that surround the vessel but are separated from it by basement membrane. Endothelial cells are primarily responsible for creating and maintaining blood-brain-barrier (BBB) tightness, but astrocytes contribute to th...

NG2 glia represent a distinct type of macroglial cells in the CNS and are unique among glia because they receive synaptic input from neurons. They are abundantly present in white and grey matter. While the majority of white matter NG2 glia differentiates into oligodendrocytes, the physiological impact of grey matter NG2 glia and their synaptic inpu...

Synaptic and axonal glutamatergic signaling to NG2 glia in white matter is critical for the cells’ differentiation and activity dependent myelination. However, in gray matter the impact of neuron-to-NG2 glia signaling is still elusive, because most of these cells keep their non-myelinating phenotype throughout live. Early in postnatal development,...

Objective Growing evidence suggests that dysfunctional astrocytes are crucial players in the development of mesial temporal lobe epilepsy (MTLE). Using a mouse model closely recapitulating key alterations of chronic human MTLE with hippocampal sclerosis, here we asked whether death of astrocytes contributes to the initiation of the disease and inve...

Thalamic astrocytes and oligodendrocytes are coupled via gap junctions and form panglial networks. Here, we show that these networks have a key role in energy supply of neurons. Filling an astrocyte or an oligodendrocyte in acute slices with glucose or lactate is sufficient to rescue the decline of stimulation-induced field post-synaptic potential...

Tanycytes are hypothalamic radial glia-like cells that form the basal wall of the third ventricle (3V) where they sense glucose and modulate neighboring neuronal activity to control feeding behavior. This role requires the coupling of hypothalamic cells since transient decreased hypothalamic Cx43 expression inhibits the increase of brain glucose-in...

The thalamus is important for sensory integration with the ventrobasal thalamus (VB) as relay controlled by GABAergic projections from the nucleus reticularis thalami (NRT). Depending on the [Cl-]i primarily set by cation-chloride-cotransporters, GABA is inhibitory or excitatory. There is evidence that VB and NRT differ in terms of GABA action, wit...

The contribution of glial cells to normal and impaired hippocampal function is increasingly being recognized, although important questions as to the mechanisms that these cells use for their crosstalk with neurons and capillaries are still unanswered or lead to controversy. Astrocytes in the hippocampus are morphologically variable and a single cel...

Neurogenesis is sustained throughout life in the mammalian brain, supporting hippocampus-dependent learning and memory. Its permanent alteration by status epilepticus (SE) is associated with learning and cognitive impairments. The mechanisms underlying the initiation of altered neurogenesis after SE are not understood. Glial fibrillary acidic prote...

Microglia, the central nervous system resident innate immune cells, cluster around Aβ plaques in Alzheimer's disease (AD). The activation phenotype of these plaque-associated microglial cells, and their differences to microglia distant to Aβ plaques, are incompletely understood. We used novel three-dimensional cell analysis software to comprehensiv...

Neuronal inhibition is mediated by glycine and/or GABA. Inferior colliculus (IC) neurons receive glycinergic and GABAergic inputs, whereas inhibition in hippocampus (HC) predominantly relies on GABA. Astrocytes heterogeneously express neurotransmitter transporters and are expected to adapt to the local requirements regarding neurotransmitter homeos...

Ca2+ signaling in astrocytes is considered to be mainly mediated by metabotropic receptors linked to intracellular Ca2+ release. However, recent studies demonstrate a significant contribution of Ca2+ influx to spontaneous and evoked Ca2+ signaling in astrocytes, suggesting that Ca2+ influx might account for astrocytic Ca2+ signaling to a greater ex...

Besides astrocytes and oligodendrocytes, NG2 proteoglycan-expressing cells (NG2 glia) represent a third subtype of macroglia in the brain. Originally described as oligodendrocyte precursor cells, they feature several characteristics not expected from mere progenitor cells, including synaptic connections with neurons. There is accumulating evidence...

Astrocyte K⁺ channels and the K⁺ currents they mediate dwarf all other transmembrane conductances in these cells. This defining feature of astrocytes and its functional implications have been investigated intensely over the past decades. Nonetheless, many aspects of astrocyte K⁺ handling and signaling remain incompletely understood. In this review,...

Perivascular endfeet of astrocytes are highly polarized compartments that ensheath blood vessels and contribute to the blood-brain barrier. They experience calcium transients with neuronal activity, a phenomenon involved in neurovascular coupling. Endfeet also mediate the uptake of glucose from the blood, a process stimulated in active brain region...

Cytoplasmic polyadenylation element binding proteins (CPEBs) are auxiliary translational factors that associate with consensus sequences present in 3'UTRs of mRNAs, thereby activating or repressing their translation. Knowing that CPEBs are players in cell cycle regulation and cellular senescence prompted us to investigate their contribution to the...

Cytoplasmic polyadenylation element binding (CPEB) proteins are translational regulators that are involved in the control of cellular senescence, synaptic plasticity, learning and memory. We have previously found all four known CPEB family members to be transcribed in the mouse hippocampus. Aside from a brief description of CPEB2 in mouse brain, no...

Astrocytes may express ionotropic glutamate and gamma-aminobutyric acid (GABA) receptors, which allow them to sense and to respond to neuronal activity. However, so far the properties of astrocytes have been studied only in a few brain regions. Here, we provide the first detailed receptor analysis of astrocytes in the murine ventrobasal thalamus an...

NG2 glial cells (as from now NG2 cells) are unique in receiving synaptic input from neurons. However, the components regulating formation and maintenance of these neuron-glia synapses remain elusive. The transmembrane protein NG2 has been considered a potential mediator of synapse formation and alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic ac...

The thalamus plays important roles as a relay station for sensory information in the central nervous system (CNS). Although thalamic glial cells participate in this activity, little is known about their properties. In this study, we characterized the formation of coupled networks between astrocytes and oligodendrocytes in the murine ventrobasal tha...

NG2 cells, a main pool of glial progenitors, express γ-aminobutyric acid A (GABAA) receptors (GABAARs), the functional and molecular properties of which are largely unknown. We recently reported that transmission between GABAergic interneurons and NG2 cells drastically changes during development of the somatosensory cortex, switching from synaptic...

NG2 cells are equipped with transmitter receptors and receive direct synaptic input from glutamatergic and GABAergic neurons. The functional impact of these neuron-glia synapses is still unclear. Here, we combined functional and molecular techniques to analyze properties of GABAA receptors in NG2 cells of the juvenile mouse hippocampus. GABA activa...

Glial fibrillary acidic protein (GFAP)-positive astrocytes with radial processes [radial glia (RG)-like cells] in the postnatal dentate gyrus share many of the characteristics of embryonic radial glia and appear to act as precursor cells for adult dentate neurogenesis, a process important for pattern separation and hippocampus-dependent learning. A...

Panglial networks are essential for normal physiology in the CNS, and the function of distinct connexins participating in these networks is not well understood. We generated Connexin32 (Cx32)-deficient mice with additional deletion of astrocytic Cx43 to explore the role of both connexins in panglial networks. Cx43/Cx32 double knock-out (dKO) mice r...

This resource is the long-awaited new revision of the most highly regarded reference volume on glial cells, and has been completely revised, greatly enlarged, and enhanced with full color figures throughout. Neglected in research for years, it is now evident that the brain only functions in a concerted action of all the cells, namely glia and neuro...

Rationale: The gap junctional protein connexin (Cx) 45 is strongly expressed in the early embryonic myocardium. In the adult hearts of mice and humans, the expression mainly is restricted to the cardiac conduction system. Cx45 plays an essential role for development and function of the embryonic heart because general and cardiomyocyte-directed def...

Purpose: Dysfunction of the blood-brain barrier (BBB) and albumin extravasation have been suggested to play a role in the etiology of human epilepsy. In this context, dysfunction of glial cells attracts increasing attention. Our study was aimed to analyze in the hippocampus (1) which cell types internalize albumin injected into the lateral ventric...

Astrocytes are endowed with the machinery to sense and respond to neuronal activity. Recent work has demonstrated that astrocytes play important physiological roles in the CNS, e.g., they synchronize action potential firing, ensure ion homeostasis, transmitter clearance and glucose metabolism, and regulate the vascular tone. Astrocytes are abundant...

In this study, we have investigated the contribution of oligodendrocytic connexin47 (Cx47) and astrocytic Cx30 to panglial gap junctional networks as well as myelin maintenance and function by deletion of both connexin coding DNAs in mice. Biocytin injections revealed complete disruption of oligodendrocyte-to-astrocyte coupling in the white matter...

In this study, we have investigated the contribution of oligodendrocytic connexin47 (Cx47) and astrocytic Cx30 to panglial gap junctional networks as well as myelin maintenance and function by deletion of both connexin coding DNAs in mice. Biocytin injections revealed complete disruption of oligodendrocyte-to-astrocyte coupling in the white matter...

In this study, we have investigated the contribution of oligodendrocytic connexin47 (Cx47) and astrocytic Cx30 to panglial gap junctional networks as well as myelin maintenance and function by deletion of both connexin coding DNAs in mice. Biocytin injections revealed complete disruption of oligodendrocyte-to-astrocyte coupling in the white matter...

Increased ammonium (NH(4) (+) ) concentration in the brain is the prime candidate responsible for hepatic encephalopathy (HE), a serious neurological disorder caused by liver failure and characterized by disturbed glutamatergic neurotransmission and impaired glial function. We investigated the mechanisms of NH(4) (+) -induced depolarization of astr...

Objectives. Glial cells constitute 90% of the human brain and are subdivided into macro- and micro-glial cell types. Astrocytes, a macroglial subtype, are located within well circumscribed well circumscribed regions of the brain such as the dentate gyrus. They possess a radial glia (RG)-like morphology and express glial-fibrillary acid protein (GFA...

In a strategy to identify novel genes involved in glioma pathogenesis by molecular characterization of chromosomal translocation breakpoints, we identified the KIAA1797 gene, encoding a protein with an as yet undefined function, to be disrupted by a 7;9 translocation in a primary glioblastoma culture. Array-based comparative genomic hybridization d...

Astrocytes express a plethora of ion channels, neurotransmitter receptors and transporters and thus are endowed with the machinery to sense and respond to neuronal activity. Recent studies have implicated astrocytes in important physiological roles in the CNS, such as synchronization of neuronal firing, ion homeostasis, neurotransmitter uptake, glu...

Elongation of an NG2 cell process. (cf. Fig. 10B). Two-photon time-lapse video was obtained from Alexa-594 dye-loaded NG2/EYFP cell processes located in an acute brain slice. Optical stacks of 20 planes were recorded every 34 s. Maximum z-projections are shown with 1 frame per second (volume 16×14×5 µm, total time 330 s, aCSF, 35°C). (AVI)

Retraction of an NG2 cell process and movement of intracellular varicosities. (cf. Fig. 10C, D). Similar recording parameters as in Video S2 were used. (AVI)

Demonstration of full inclusion of vGLUT1 positive objects in NG2 cell processes (3D reconstruction). The cell is the one shown in Fig. 9. NG2 cells from hippocampus (CA1) were identified by electrophysiology, biocytin-filled, fixed and visualized by streptavidin CY3 (red channel). The green channel displays immunocytochemical detection of vGLUT1....

Microtubules are well-preserved in the processes of freshly dissociated, identified astrocytes. Labeling for both, cell nuclei (bisbenzimidine) and glial filaments (GFAP, Alexa 360) is revealed in the blue channel. An astrocyte (center) and two unidentified cells (right) are displayed. Microtubules (α-tubulin, red) are obvious in the astrocyte proc...

Exemplary agarose gels of mRNA-transcripts for Cav channel family and S100β. (TIF)

Primers used for single-cell RT-PCR. (DOC)

NG2 cells, the fourth type of glia in the mammalian CNS, receive synaptic input from neurons. The function of this innervation is unknown yet. Postsynaptic changes in intracellular Ca2+-concentration ([Ca2+]i) might be a possible consequence. We employed transgenic mice with fluorescently labeled NG2 cells to address this issue. To identify Ca2+-si...

Mice deficient in the water channel aquaporin-4 (AQP4) demonstrate increased seizure duration in response to hippocampal stimulation as well as impaired extracellular K+ clearance. However, the expression of AQP4 in the hippocampus is not well described. In this study, we investigated (i) the developmental, laminar and cell-type specificity of AQP4...

Summary Findings obtained from surgical specimens of epilepsy patients and animal models of epilepsy demonstrate dysfunction of astrocytes in epilepsy. Specifically, gap junction coupling, glutamate uptake, and K+ buffering are compromised. In epilepsy models, astroglial alterations occur very early after status epilepticus, suggesting their crucia...

Cytoplasmic Polyadenylation Element Binding proteins (CPEBs) regulate protein synthesis in neurons crucial for LTP maintenance, memory and learning. Neuronal CPEBs also mediate hyperexcitability of neurons in an animal model of temporal lobe epilepsy (TLE). Unlike in neurons, CPEB function in microglial cells has hardly been investigated. Neuronal...

The presence of ionotropic and metabotropic neurotransmitter receptors led to the conclusion that astrocytes are endowed with the machinery to sense and respond to neuronal activity. Recent studies have implicated astrocytes in important physiological roles in the CNS, such as synchronisation of neuronal firing, ion homeostasis, neurotransmitter up...

Epilepsy comprises a group of disorders characterized by the periodic occurrence of seizures. Currently available anticonvulsant drugs and therapies are insufficient to controlling seizure activity in about one third of epilepsy patients. Thus, there is an urgent need for new therapies that prevent the genesis of the disorder and improve seizure co...

Astrocytes in different brain regions display variable functional properties. In the hippocampus, astrocytes predominantly express time- and voltage-independent currents, but the underlying ion channels are not well defined. This ignorance is partly attributable to abundant intercellular coupling of these cells through gap junctions, impeding quant...

In the adult dentate gyrus, radial glia-like cells represent putative stem cells generating neurons and glial cells. Here, we combined patch-clamp recordings, biocytin filling, immunohistochemistry, single-cell transcript analysis, and mouse transgenics to test for connexin expression and gap junctional coupling of radial glia-like cells and its im...

Synaptotagmins are a large family of membrane-trafficking proteins. They are evolutionarily conserved and have 15 members in rodents and humans. Synaptotagmins-1, -2, and -9, are known to have an essential role as calcium sensors for fast synaptic release. Synaptotagmin-7 is a major calcium sensor for the exocytosis of large secretory vesicles in e...

The NG2 glycoprotein is a type I membrane protein expressed by immature cells in the developing and adult mouse. NG2+ cells of the embryonic and adult brain have been principally viewed as oligodendrocyte precursor cells but have additionally been considered a fourth glial class. They are likely to be a heterogeneous population. In order to facilit...

Embryonic stem (ES) cell-derived neural progenitor cells (ESNPs) generated in vitro are multipotent progenitors which can differentiate into oligodendrocytes, astrocytes, and neurons. Given the exciting prospects for ES cell-based treatments of neurological disorders, several studies investigated the migration, integration, and differentiation of g...

Neuropeptide Y (NPY) reduces anxiety-related behavior in various animal models. Since activity in the lateral amygdala (LA) seems crucial for fear expression of behavior, we studied the mechanisms of NPY in LA projection neurons using whole-cell patch-clamp recordings in slices of the rat amygdala in vitro. Application of NPY activated a membrane K...

One of the main challenges for a better understanding of signaling mechanisms in the normal and diseased central nervous system (CNS) is to unravel the molecular basics of function on the cellular and systemic levels. Several important cellular processes, such as proliferation, differentiation, and cell death, are directly or indirectly influenced...

Currently available anticonvulsant drugs and complementary therapies are insufficient to control seizures in about a third of epileptic patients. Thus, there is an urgent need for new treatments that prevent the development of epilepsy and control it better in patients already afflicted with the disease. A prerequisite to reach this goal is a deepe...

Purinergic signalling plays a major role in intercellular communication between neurons and glial cells. Glial cells express metabotropic receptors for ATP and adenosine, the latter being activated after ATP cleavage through extracellular ecto-ATPase activity. Ionotropic receptors for extracellular ATP, so called P2X receptors, might contribute to...

One of the main challenges for a better understanding of signaling mechanisms in the normal and diseased central nervous system (CNS) is to unravel the molecular basics of function on the cellular and systemic levels. Several important cellular processes, such as proliferation, differentiation, and cell death, are directly or indirectly influenced...

One hundred fifty years ago glial cells were discovered as a second, non-neuronal, cell type in the central nervous system. To ascribe a function to these new, enigmatic cells, it was suggested that they either glue the neurons together (the Greek word “γλια” means “glue”) or provide a robust scaffold for them (“support cells”). Although both specu...

Neurons in the rat lateral amygdala in situ were classified based upon electrophysiological and molecular parameters, as studied by patch-clamp, single-cell RT-PCR and unsupervised cluster analyses. Projection neurons (class I) were characterized by low firing rates, frequency adaptation and expression of the vesicular glutamate transporter (VGLUT1...

Recent work on glial cell physiology has revealed that glial cells, and astrocytes in particular, are much more actively involved in brain information processing than previously thought. This finding has stimulated the view that the active brain should no longer be regarded solely as a network of neuronal contacts, but instead as a circuit of integ...

Neuronal properties were investigated through patch-clamp recording in situ in surgical specimens of the human lateral amygdala (LA) obtained from patients with intractable temporal lobe epilepsy. Projection neurons displayed spiny dendrites, action potentials with varying degree of frequency adaptation, and an inwardly rectifying K+ (Kir) conducta...

For decades, glial cells of the nervous system have been considered passive supporting cells. However, in the meantime it has been found that astrocytes and oligodendrocytes express almost the same set of ion channels and membrane receptors as neurons. Spectacular recent findings now demonstrate that subtypes of glial cells receive direct synaptic...

Zusammenfassung Gliazellen im Nervensystem sind über Jahrzehnte als passive Stützelemente betrachtet worden. Inzwischen ist jedoch klar, dass Astrozyten und Oligodendrozyten über ein ähnlich breites Repertoire an Ionenkanälen und Membranrezeptoren verfügen wie Nervenzellen. Spektakuläre Befunde der letzten Jahre zeigen, dass Subtypen von Gliazellen...

Astrocytes establish rapid cell-to-cell communication through the release of chemical transmitters. The underlying mechanisms and functional significance of this release are, however, not well understood. Here we identify an astrocytic vesicular compartment that is competent for glutamate exocytosis. Using postembedding immunogold labeling of the r...

Astrocytes express ionotropic glutamate receptors (GluRs), and recent evidence suggests that these receptors contribute to direct signaling between neurons and glial cells in vivo. Here, we have used functional and molecular analyses to investigate receptor properties in astrocytes of human hippocampus resected from patients with pharmacoresistant...

Work over the past ten years has significantly added to our understanding of astrocyte physiology. A huge number of original reports on astrocyte ion channel properties now are available, and it is beyond the scope of this report to provide a complete survey of this work. Rather, while referring to reviews for detailed information, we tried to focu...

Embryonic stem (ES) cells provide attractive prospects for neural transplantation. So far, grafting strategies in the CNS have focused mainly on neuronal replacement. Employing a slice culture model, we found that ES cell-derived glial precursors (ESGPs) possess a remarkable capacity to integrate into the host glial network. Following deposition on...

To further characterize the recently described gap junction gene connexin 47 (Cx47), we generated Cx47-null mice by replacing the Cx47 coding DNA with an enhanced green fluorescent protein (EGFP) reporter gene, which was thus placed under control of the endogenous Cx47 promoter. Homozygous mutant mice were fertile and showed no obvious morphologica...

The voltage-gated potassium channel Kv1.1 contains phosphorylation sites for protein kinase A (PKA) and protein kinase C (PKC). To study Kv1.1 protein expression and cellular distribution in regard to its level of phosphorylation, the effects of PKA and PKC activation on Kv1.1 were investigated in HEK 293 cells stably transfected with Kv1.1 (HEK 29...

Recent data have suggested the existence of direct signaling pathways between glial cells and neurons. Here we report the coexistence of distinct types of cells expressing astrocyte-specific markers within the hippocampus that display diverse morphological, molecular, and functional profiles. Usage of transgenic mice with GFAP promoter-controlled e...

Astrocytes in the hippocampus express glutamate receptors of the AMPA subtype. An increasing body of evidence suggests a contribution of astroglial AMPA receptors to a direct signaling between neurons and glial cells in vivo. Here, we have combined functional analysis with singlecell RT-PCR to investigate whether hippocampal astrocytes express Ca(2...

Astrocytes in the hippocampus express various ion channels and transmitter receptors. In addition, the properties of these cells significantly change during postnatal development and under pathophysiological conditions such as epilepsy. We have investigated whether this phenotypic heterogeneity reflects different stages of cellular maturation from...

Forskolin (FSK) affects voltage-gated K(+) (Kv) currents in different cell types, but it is not known which of the various subunits form FSK-sensitive Kv channels. We compared the effect of the compound at Kv1.1 and Kv1.4 channels ectopically expressed in HEK 293 cells. Low FSK concentrations induced a phosphorylation-dependent potentiation of Kv1....

Epilepsy is a condition in the brain characterized by repetitively occurring seizures. While various changes in neuronal properties have been reported to accompany or induce seizure activity in human or experimental epilepsy, other studies suggested that glial cells might be involved in epileptogenesis. Recent findings demonstrate that in the cours...

Astrocytes and neurons are tightly associated and recent data suggest a direct signaling between neuronal and glial cells in vivo. To further analyze these interactions, the patch-clamp technique was combined with single-cell RT-PCR in acute hippocampal brain slices. Subsequent to functional analysis, the cytoplasm of the same cell was harvested to...

Recent data suggested a role for glial cells in epilepsy. This study sought to identify and functionally characterize AMPA receptors expressed by astrocytes in human hippocampal tissue resected from patients with intractable temporal lobe epilepsy. Patch-clamp and fast application methods were combined to investigate astrocytes in situ and after fr...

6-Hydroxykynurenic acid (6-HKA), a derivative of kynurenic acid (KYNA) extracted from Ginkgo biloba leaves, was tested for its putative glutamate receptor (GluR) antagonism in comparison to the scaffold substance. The patch-clamp method together with fast-application techniques were used to estimate inhibition by 6-HKA and KYNA of agonist binding a...

Functional properties of astrocytes were investigated with the patch-clamp technique in acute hippocampal brain slices obtained from surgical specimens of patients suffering from pharmaco-resistant temporal lobe epilepsy (TLE). In patients with significant neuronal cell loss, i.e. Ammon’s horn sclerosis, the glial current patterns resembled propert...