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Wang XP, Yan D, Jin XP, Zhang WY, Shi T, Wang X, Song W, Xiong X, Guo D, Chen S. The role of amino acid metabolism alterations in acute ischemic stroke: From mechanism to application. Pharmacol Res 2024; 207:107313. [PMID: 39025169 DOI: 10.1016/j.phrs.2024.107313] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/01/2024] [Revised: 07/10/2024] [Accepted: 07/15/2024] [Indexed: 07/20/2024]
Abstract
Acute ischemic stroke (AIS) is the most prevalent type of stroke, and due to its high incidence, disability rate, and mortality rate, it imposes a significant burden on the health care system. Amino acids constitute one of the most crucial metabolic products within the human body, and alterations in their metabolic pathways have been identified in the microenvironment of AIS, thereby influencing the pathogenesis, severity, and prognosis of AIS. The amino acid metabolism characteristics in AIS are complex. On one hand, the dynamic progression of AIS continuously reshapes the amino acid metabolism pattern. Conversely, changes in the amino acid metabolism pattern also exert a double-edged effect on AIS. This interaction is bidirectional, dynamic, heterogeneous, and dose-specific. Therefore, the distinctive metabolic reprogramming features surrounding amino acids during the AIS process are systematically summarized in this paper, aiming to provide potential investigative strategies for the early diagnosis, treatment approaches, and prognostic enhancement of AIS.
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Affiliation(s)
- Xiang-Ping Wang
- First People's Hospital of Linping District; Linping Campus, The Second Affiliated Hospital of Zhejiang University School of Medicine, Hangzhou, 311100, China
| | - Dan Yan
- Affiliated Xiaoshan Hospital, Hangzhou Normal University, Hangzhou 311202, China
| | - Xia-Ping Jin
- First People's Hospital of Linping District; Linping Campus, The Second Affiliated Hospital of Zhejiang University School of Medicine, Hangzhou, 311100, China
| | - Wen-Yan Zhang
- First People's Hospital of Linping District; Linping Campus, The Second Affiliated Hospital of Zhejiang University School of Medicine, Hangzhou, 311100, China
| | - Tao Shi
- First People's Hospital of Linping District; Linping Campus, The Second Affiliated Hospital of Zhejiang University School of Medicine, Hangzhou, 311100, China
| | - Xiang Wang
- First People's Hospital of Linping District; Linping Campus, The Second Affiliated Hospital of Zhejiang University School of Medicine, Hangzhou, 311100, China
| | - Wenjuan Song
- First People's Hospital of Linping District; Linping Campus, The Second Affiliated Hospital of Zhejiang University School of Medicine, Hangzhou, 311100, China
| | - Xing Xiong
- Traditional Chinese Medical Hospital of Xiaoshan, The Affiliated Hospital of Zhejiang Chinese Medical University, Hangzhou, Zhejiang Province 311200, China
| | - Duancheng Guo
- Cancer Institute, Fudan University Shanghai Cancer Center; Department of Oncology, Shanghai Medical College, Fudan University, Shanghai 200032, China.
| | - Sheng Chen
- First People's Hospital of Xiaoshan District, Hangzhou, Zhejiang Province 311200, China.
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2
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Niklaus S, Glasauer SMK, Kovermann P, Farshori KF, Cadetti L, Früh S, Rieser NN, Gesemann M, Zang J, Fahlke C, Neuhauss SCF. Glutamate transporters are involved in direct inhibitory synaptic transmission in the vertebrate retina. Open Biol 2024; 14:240140. [PMID: 39079673 PMCID: PMC11288666 DOI: 10.1098/rsob.240140] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2024] [Accepted: 06/12/2024] [Indexed: 08/03/2024] Open
Abstract
In the central nervous system of vertebrates, glutamate serves as the primary excitatory neurotransmitter. However, in the retina, glutamate released from photoreceptors causes hyperpolarization in post-synaptic ON-bipolar cells through a glutamate-gated chloride current, which seems paradoxical. Our research reveals that this current is modulated by two excitatory glutamate transporters, EAAT5b and EAAT7. In the zebrafish retina, these transporters are located at the dendritic tips of ON-bipolar cells and interact with all four types of cone photoreceptors. The absence of these transporters leads to a decrease in ON-bipolar cell responses, with eaat5b mutants being less severely affected than eaat5b/eaat7 double mutants, which also exhibit altered response kinetics. Biophysical investigations establish that EAAT7 is an active glutamate transporter with a predominant anion conductance. Our study is the first to demonstrate the direct involvement of post-synaptic glutamate transporters in inhibitory direct synaptic transmission at a central nervous system synapse.
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Affiliation(s)
- Stephanie Niklaus
- Department of Molecular Life Sciences, University of Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland
| | - Stella M. K. Glasauer
- Department of Molecular Life Sciences, University of Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland
| | - Peter Kovermann
- Institute of Biological Information Processing, Molekular- und Zellphysiologie (IBI-1), Forschungszentrum Jülich, Leo-Brandt-Strasse, 52425 Jülich, Germany
| | - Kulsum F. Farshori
- Department of Molecular Life Sciences, University of Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland
| | - Lucia Cadetti
- Department of Molecular Life Sciences, University of Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland
| | - Simon Früh
- Department of Molecular Life Sciences, University of Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland
| | - Nicolas N. Rieser
- Department of Molecular Life Sciences, University of Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland
| | - Matthias Gesemann
- Department of Molecular Life Sciences, University of Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland
| | - Jingjing Zang
- Department of Molecular Life Sciences, University of Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland
| | - Christoph Fahlke
- Institute of Biological Information Processing, Molekular- und Zellphysiologie (IBI-1), Forschungszentrum Jülich, Leo-Brandt-Strasse, 52425 Jülich, Germany
| | - Stephan C. F. Neuhauss
- Department of Molecular Life Sciences, University of Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland
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Clark AM, Yu D, Neiswanger G, Zhu D, Zou J, Maschek JA, Burgoyne T, Yang J. Disruption of CFAP418 interaction with lipids causes widespread abnormal membrane-associated cellular processes in retinal degenerations. JCI Insight 2024; 9:e162621. [PMID: 37971880 PMCID: PMC10906455 DOI: 10.1172/jci.insight.162621] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2022] [Accepted: 11/15/2023] [Indexed: 11/19/2023] Open
Abstract
Syndromic ciliopathies and retinal degenerations are large heterogeneous groups of genetic diseases. Pathogenic variants in the CFAP418 gene may cause both disorders, and its protein sequence is evolutionarily conserved. However, the disease mechanism underlying CFAP418 mutations has not been explored. Here, we apply quantitative lipidomic, proteomic, and phosphoproteomic profiling and affinity purification coupled with mass spectrometry to address the molecular function of CFAP418 in the retina. We show that CFAP418 protein binds to the lipid metabolism precursor phosphatidic acid (PA) and mitochondrion-specific lipid cardiolipin but does not form a tight and static complex with proteins. Loss of Cfap418 in mice disturbs membrane lipid homeostasis and membrane-protein associations, which subsequently causes mitochondrial defects and membrane-remodeling abnormalities across multiple vesicular trafficking pathways in photoreceptors, especially the endosomal sorting complexes required for transport (ESCRT) pathway. Ablation of Cfap418 also increases the activity of PA-binding protein kinase Cα in the retina. Overall, our results indicate that membrane lipid imbalance is a pathological mechanism underlying syndromic ciliopathies and retinal degenerations which is associated with other known causative genes of these diseases.
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Affiliation(s)
- Anna M. Clark
- Department of Ophthalmology and Visual Sciences, Moran Eye Center, and
| | - Dongmei Yu
- Department of Ophthalmology and Visual Sciences, Moran Eye Center, and
| | - Grace Neiswanger
- Department of Ophthalmology and Visual Sciences, Moran Eye Center, and
| | - Daniel Zhu
- Department of Ophthalmology and Visual Sciences, Moran Eye Center, and
| | - Junhuang Zou
- Department of Ophthalmology and Visual Sciences, Moran Eye Center, and
| | - J. Alan Maschek
- Department of Nutrition and Integrative Physiology, University of Utah, Salt Lake City, Utah, USA
| | - Thomas Burgoyne
- UCL Institute of Ophthalmology, University College of London, London, United Kingdom
| | - Jun Yang
- Department of Ophthalmology and Visual Sciences, Moran Eye Center, and
- Department of Otolaryngology, and
- Department of Neurobiology, University of Utah, Salt Lake City, Utah, USA
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Thoreson WB, Chhunchha B. EAAT5 glutamate transporter rapidly binds glutamate with micromolar affinity in mouse rods. J Gen Physiol 2023; 155:e202313349. [PMID: 37477643 PMCID: PMC10359920 DOI: 10.1085/jgp.202313349] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2023] [Revised: 04/17/2023] [Accepted: 07/05/2023] [Indexed: 07/22/2023] Open
Abstract
Light responses of rod photoreceptor cells in the retina are encoded by changes in synaptic glutamate release that is in turn shaped by reuptake involving EAAT5 plasma membrane glutamate transporters. Heterologously expressed EAAT5 activates too slowly upon glutamate binding to support significant uptake. We tested EAAT5 activation in mouse rods in vivo by stimulating glutamate transporter anion currents (IA(glu)) with UV flash photolysis of MNI-glutamate, varying flash intensity to vary glutamate levels. Responses to uncaging rose rapidly with time constants of 2-3 ms, similar to IA(glu) events arising from spontaneous release. Spontaneous release events and IA(glu) evoked by weak flashes also declined with similar time constants of 40-50 ms. Stronger flashes evoked responses that decayed more slowly. Time constants were twofold faster at 35°C, suggesting that they reflect transporter kinetics, not diffusion. Selective EAAT1 and EAAT2 inhibitors had no significant effect, suggesting IA(glu) in rods arises solely from EAAT5. We calibrated glutamate levels attained during flash photolysis by expressing a fluorescent glutamate sensor iGluSnFr in cultured epithelial cells. We compared fluorescence at different glutamate concentrations to fluorescence evoked by photolytic uncaging of MNI-glutamate. The relationship between flash intensity and glutamate yielded EC50 values for EAAT5 amplitude, decay time, and rise time of ∼10 μM. Micromolar affinity and rapid activation of EAAT5 in rods show it can rapidly bind synaptic glutamate. However, we also found that EAAT5 currents are saturated by the synchronous release of only a few vesicles, suggesting limited capacity and a role for glial uptake at higher release rates.
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Affiliation(s)
- Wallace B. Thoreson
- Department of Ophthalmology and Visual Sciences, Truhlsen Eye Institute, Omaha, NE, USA
- Department of Pharmacology and Experimental Neuroscience, University of Nebraska Medical Center, Omaha, NE, USA
| | - Bhavana Chhunchha
- Department of Ophthalmology and Visual Sciences, Truhlsen Eye Institute, Omaha, NE, USA
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The Protective Role of Glutathione on Zinc-Induced Neuron Death after Brain Injuries. Int J Mol Sci 2023; 24:ijms24032950. [PMID: 36769273 PMCID: PMC9917832 DOI: 10.3390/ijms24032950] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2022] [Revised: 01/30/2023] [Accepted: 02/01/2023] [Indexed: 02/05/2023] Open
Abstract
Glutathione (GSH) is necessary for maintaining physiological antioxidant function, which is responsible for maintaining free radicals derived from reactive oxygen species at low levels and is associated with improved cognitive performance after brain injury. GSH is produced by the linkage of tripeptides that consist of glutamic acid, cysteine, and glycine. The adequate supplementation of GSH has neuroprotective effects in several brain injuries such as cerebral ischemia, hypoglycemia, and traumatic brain injury. Brain injuries produce an excess of reactive oxygen species through complex biochemical cascades, which exacerbates primary neuronal damage. GSH concentrations are known to be closely correlated with the activities of certain genes such as excitatory amino acid carrier 1 (EAAC1), glutamate transporter-associated protein 3-18 (Gtrap3-18), and zinc transporter 3 (ZnT3). Following brain-injury-induced oxidative stress, EAAC1 function is negatively impacted, which then reduces cysteine absorption and impairs neuronal GSH synthesis. In these circumstances, vesicular zinc is also released into the synaptic cleft and then translocated into postsynaptic neurons. The excessive influx of zinc inhibits glutathione reductase, which inhibits GSH's antioxidant functions in neurons, resulting in neuronal damage and ultimately in the impairment of cognitive function. Therefore, in this review, we explore the overall relationship between zinc and GSH in terms of oxidative stress and neuronal cell death. Furthermore, we seek to understand how the modulation of zinc can rescue brain-insult-induced neuronal death after ischemia, hypoglycemia, and traumatic brain injury.
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Sijben HJ, Dall’ Acqua L, Liu R, Jarret A, Christodoulaki E, Onstein S, Wolf G, Verburgt SJ, Le Dévédec SE, Wiedmer T, Superti-Furga G, IJzerman AP, Heitman LH. Impedance-Based Phenotypic Readout of Transporter Function: A Case for Glutamate Transporters. Front Pharmacol 2022; 13:872335. [PMID: 35677430 PMCID: PMC9169222 DOI: 10.3389/fphar.2022.872335] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2022] [Accepted: 03/29/2022] [Indexed: 11/18/2022] Open
Abstract
Excitatory amino acid transporters (EAAT/SLC1) mediate Na+-dependent uptake of extracellular glutamate and are potential drug targets for neurological disorders. Conventional methods to assess glutamate transport in vitro are based on radiolabels, fluorescent dyes or electrophysiology, which potentially compromise the cell’s physiology and are generally less suited for primary drug screens. Here, we describe a novel label-free method to assess human EAAT function in living cells, i.e., without the use of chemical modifications to the substrate or cellular environment. In adherent HEK293 cells overexpressing EAAT1, stimulation with glutamate or aspartate induced cell spreading, which was detected in real-time using an impedance-based biosensor. This change in cell morphology was prevented in the presence of the Na+/K+-ATPase inhibitor ouabain and EAAT inhibitors, which suggests the substrate-induced response was ion-dependent and transporter-specific. A mechanistic explanation for the phenotypic response was substantiated by actin cytoskeleton remodeling and changes in the intracellular levels of the osmolyte taurine, which suggests that the response involves cell swelling. In addition, substrate-induced cellular responses were observed for cells expressing other EAAT subtypes, as well as in a breast cancer cell line (MDA-MB-468) with endogenous EAAT1 expression. These findings allowed the development of a label-free high-throughput screening assay, which could be beneficial in early drug discovery for EAATs and holds potential for the study of other transport proteins that modulate cell shape.
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Affiliation(s)
- Hubert J. Sijben
- Division of Drug Discovery and Safety, Leiden Academic Centre for Drug Research, Leiden University, Leiden, Netherlands
| | - Laura Dall’ Acqua
- Division of Drug Discovery and Safety, Leiden Academic Centre for Drug Research, Leiden University, Leiden, Netherlands
| | - Rongfang Liu
- Division of Drug Discovery and Safety, Leiden Academic Centre for Drug Research, Leiden University, Leiden, Netherlands
| | - Abigail Jarret
- CeMM Research Center for Molecular Medicine of the Austrian Academy of Sciences, Medical University of Vienna, Vienna, Austria
| | - Eirini Christodoulaki
- CeMM Research Center for Molecular Medicine of the Austrian Academy of Sciences, Medical University of Vienna, Vienna, Austria
| | - Svenja Onstein
- CeMM Research Center for Molecular Medicine of the Austrian Academy of Sciences, Medical University of Vienna, Vienna, Austria
| | - Gernot Wolf
- CeMM Research Center for Molecular Medicine of the Austrian Academy of Sciences, Medical University of Vienna, Vienna, Austria
| | - Simone J. Verburgt
- Division of Drug Discovery and Safety, Leiden Academic Centre for Drug Research, Leiden University, Leiden, Netherlands
| | - Sylvia E. Le Dévédec
- Division of Drug Discovery and Safety, Leiden Academic Centre for Drug Research, Leiden University, Leiden, Netherlands
| | - Tabea Wiedmer
- CeMM Research Center for Molecular Medicine of the Austrian Academy of Sciences, Medical University of Vienna, Vienna, Austria
| | - Giulio Superti-Furga
- CeMM Research Center for Molecular Medicine of the Austrian Academy of Sciences, Medical University of Vienna, Vienna, Austria
| | - Adriaan P. IJzerman
- Division of Drug Discovery and Safety, Leiden Academic Centre for Drug Research, Leiden University, Leiden, Netherlands
| | - Laura H. Heitman
- Division of Drug Discovery and Safety, Leiden Academic Centre for Drug Research, Leiden University, Leiden, Netherlands
- Oncode Institute, Leiden, Netherlands
- *Correspondence: Laura H. Heitman,
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Tang FS, Yuan HL, Liu JB, Zhang G, Chen SY, Ke JB. Glutamate Transporters EAAT2 and EAAT5 Differentially Shape Synaptic Transmission from Rod Bipolar Cell Terminals. eNeuro 2022; 9:ENEURO.0074-22.2022. [PMID: 35523583 PMCID: PMC9121915 DOI: 10.1523/eneuro.0074-22.2022] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2022] [Revised: 04/26/2022] [Accepted: 05/02/2022] [Indexed: 11/21/2022] Open
Abstract
Excitatory amino acid transporters (EAATs) control visual signal transmission in the retina by rapidly removing glutamate released from photoreceptors and bipolar cells (BCs). Although it has been reported that EAAT2 and EAAT5 are expressed at presynaptic terminals of photoreceptors and some BCs in mammals, the distinct functions of these two glutamate transporters in retinal synaptic transmission, especially at a single synapse, remain elusive. In this study, we found that EAAT2 was expressed in all BC types while coexisting with EAAT5 in rod bipolar (RB) cells and several types of cone BCs from mice of either sex. Our immunohistochemical study, together with a recently published literature (Gehlen et al., 2021), showed that EAAT2 and EAAT5 were both located in RB axon terminals near release sites. Optogenetic, electrophysiological and pharmacological analyses, however, demonstrated that EAAT2 and EAAT5 regulated neurotransmission at RB→AII amacrine cell synapses in significantly different ways: EAAT5 dramatically affected both the peak amplitude and kinetics of postsynaptic responses in AIIs, whereas EAAT2 had either relatively small or opposite effects. By contrast, blockade of EAAT1/GLAST, which was exclusively expressed in Müller cells, showed no obvious effect on AII responses, indicating that glutamate uptake by Müller cells did not influence synaptic transmission from RB terminals. Furthermore, we found that temporal resolution at RB→AII synapses was reduced substantially by blockade of EAAT5 but not EAAT2. Taken together, our work reveals the distinct functions of EAAT2 and EAAT5 in signal transmission at RB ribbon synapses.
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Affiliation(s)
| | | | | | | | | | - Jiang-Bin Ke
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangdong Provincial Key Laboratory of Ophthalmology and Visual Science, Guangzhou 510060, China
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Boccuni I, Fairless R. Retinal Glutamate Neurotransmission: From Physiology to Pathophysiological Mechanisms of Retinal Ganglion Cell Degeneration. Life (Basel) 2022; 12:638. [PMID: 35629305 PMCID: PMC9147752 DOI: 10.3390/life12050638] [Citation(s) in RCA: 17] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2022] [Revised: 04/22/2022] [Accepted: 04/22/2022] [Indexed: 12/12/2022] Open
Abstract
Glutamate neurotransmission and metabolism are finely modulated by the retinal network, where the efficient processing of visual information is shaped by the differential distribution and composition of glutamate receptors and transporters. However, disturbances in glutamate homeostasis can result in glutamate excitotoxicity, a major initiating factor of common neurodegenerative diseases. Within the retina, glutamate excitotoxicity can impair visual transmission by initiating degeneration of neuronal populations, including retinal ganglion cells (RGCs). The vulnerability of RGCs is observed not just as a result of retinal diseases but has also been ascribed to other common neurodegenerative and peripheral diseases. In this review, we describe the vulnerability of RGCs to glutamate excitotoxicity and the contribution of different glutamate receptors and transporters to this. In particular, we focus on the N-methyl-d-aspartate (NMDA) receptor as the major effector of glutamate-induced mechanisms of neurodegeneration, including impairment of calcium homeostasis, changes in gene expression and signalling, and mitochondrial dysfunction, as well as the role of endoplasmic reticular stress. Due to recent developments in the search for modulators of NMDA receptor signalling, novel neuroprotective strategies may be on the horizon.
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Affiliation(s)
- Isabella Boccuni
- Institute for Physiology and Pathophysiology, Heidelberg University, 69120 Heidelberg, Germany
- Department of Neurology, University Clinic Heidelberg, 69120 Heidelberg, Germany;
| | - Richard Fairless
- Department of Neurology, University Clinic Heidelberg, 69120 Heidelberg, Germany;
- Clinical Cooperation Unit (CCU) Neurooncology, German Cancer Consortium (DKTK), German Cancer Research Center (DKFZ), 69120 Heidelberg, Germany
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