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Trovò L, Kouvaros S, Schwenk J, Fernandez-Fernandez D, Fritzius T, Rem PD, Früh S, Gassmann M, Fakler B, Bischofberger J, Bettler B. Synaptotagmin-11 facilitates assembly of a presynaptic signaling complex in post-Golgi cargo vesicles. EMBO Rep 2024; 25:2610-2634. [PMID: 38698221 PMCID: PMC11169412 DOI: 10.1038/s44319-024-00147-0] [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: 08/18/2023] [Revised: 04/11/2024] [Accepted: 04/12/2024] [Indexed: 05/05/2024] Open
Abstract
GABAB receptors (GBRs), the G protein-coupled receptors for GABA, regulate synaptic transmission throughout the brain. A main synaptic function of GBRs is the gating of Cav2.2-type Ca2+ channels. However, the cellular compartment where stable GBR/Cav2.2 signaling complexes form remains unknown. In this study, we demonstrate that the vesicular protein synaptotagmin-11 (Syt11) binds to both the auxiliary GBR subunit KCTD16 and Cav2.2 channels. Through these dual interactions, Syt11 recruits GBRs and Cav2.2 channels to post-Golgi vesicles, thus facilitating assembly of GBR/Cav2.2 signaling complexes. In addition, Syt11 stabilizes GBRs and Cav2.2 channels at the neuronal plasma membrane by inhibiting constitutive internalization. Neurons of Syt11 knockout mice exhibit deficits in presynaptic GBRs and Cav2.2 channels, reduced neurotransmitter release, and decreased GBR-mediated presynaptic inhibition, highlighting the critical role of Syt11 in the assembly and stable expression of GBR/Cav2.2 complexes. These findings support that Syt11 acts as a vesicular scaffold protein, aiding in the assembly of signaling complexes from low-abundance components within transport vesicles. This mechanism enables insertion of pre-assembled functional signaling units into the synaptic membrane.
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Affiliation(s)
- Luca Trovò
- Department of Biomedicine, University of Basel, Basel, Switzerland
| | | | - Jochen Schwenk
- Institute of Physiology, Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | | | | | | | - Simon Früh
- Department of Biomedicine, University of Basel, Basel, Switzerland
| | - Martin Gassmann
- Department of Biomedicine, University of Basel, Basel, Switzerland
| | - Bernd Fakler
- Institute of Physiology, Faculty of Medicine, University of Freiburg, Freiburg, Germany
- CIBSS Center for Integrative Biological Signalling Studies, University of Freiburg, Freiburg, Germany
- Center for Basics in NeuroModulation, Freiburg, Germany
| | | | - Bernhard Bettler
- Department of Biomedicine, University of Basel, Basel, Switzerland.
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2
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Kennedy WM, Gonzalez JC, Lee H, Wadiche JI, Overstreet-Wadiche L. T-Type Ca 2+ Channels Mediate a Critical Period of Plasticity in Adult-Born Granule Cells. J Neurosci 2024; 44:e1503232024. [PMID: 38413230 PMCID: PMC11007310 DOI: 10.1523/jneurosci.1503-23.2024] [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: 08/08/2023] [Revised: 01/26/2024] [Accepted: 02/20/2024] [Indexed: 02/29/2024] Open
Abstract
Adult-born granule cells (abGCs) exhibit a transient period of elevated synaptic plasticity that plays an important role in hippocampal function. Various mechanisms have been implicated in this critical period for enhanced plasticity, including minimal GABAergic inhibition and high intrinsic excitability conferred by T-type Ca2+ channels. Here we assess the contribution of synaptic inhibition and intrinsic excitability to long-term potentiation (LTP) in abGCs of adult male and female mice using perforated patch recordings. We show that the timing of critical period plasticity is unaffected by intact GABAergic inhibition such that 4-6-week-old abGCs exhibit LTP that is absent by 8 weeks. Blocking GABAA receptors, or partial blockade of GABA release from PV and nNos-expressing interneurons by a µ-opioid receptor agonist, strongly enhances LTP in 4-week-old GCs, suggesting that minimal inhibition does not underlie critical period plasticity. Instead, the closure of the critical period coincides with a reduction in the contribution of T-type Ca2+ channels to intrinsic excitability, and a selective T-type Ca2+ channel antagonist prevents LTP in 4-week-old but not mature GCs. Interestingly, whole-cell recordings that facilitate T-type Ca2+ channel activity in mature GCs unmasks LTP (with inhibition intact) that is also sensitive to a T-type Ca2+ channel antagonist, suggesting T-type channel activity in mature GCs is suppressed by native intracellular signaling. Together these results show that abGCs use T-type Ca2+ channels to overcome inhibition, providing new insight into how high intrinsic excitability provides young abGCs a competitive advantage for experience-dependent synaptic plasticity.
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Affiliation(s)
- William M Kennedy
- Department of Neurobiology and McKnight Brain Institute, University of Alabama at Birmingham, Birmingham, Alabama 35294
| | - Jose Carlos Gonzalez
- Department of Neurobiology and McKnight Brain Institute, University of Alabama at Birmingham, Birmingham, Alabama 35294
| | - Haeun Lee
- Department of Neurobiology and McKnight Brain Institute, University of Alabama at Birmingham, Birmingham, Alabama 35294
| | - Jacques I Wadiche
- Department of Neurobiology and McKnight Brain Institute, University of Alabama at Birmingham, Birmingham, Alabama 35294
| | - Linda Overstreet-Wadiche
- Department of Neurobiology and McKnight Brain Institute, University of Alabama at Birmingham, Birmingham, Alabama 35294
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3
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Vyleta NP, Snyder JS. Enhanced excitability but mature action potential waveforms at mossy fiber terminals of young, adult-born hippocampal neurons in mice. Commun Biol 2023; 6:290. [PMID: 36934174 PMCID: PMC10024705 DOI: 10.1038/s42003-023-04678-5] [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: 10/12/2022] [Accepted: 03/07/2023] [Indexed: 03/20/2023] Open
Abstract
Adult-born granule neurons pass through immature critical periods where they display enhanced somatic excitability and afferent plasticity, which is believed to endow them with unique roles in hippocampal learning and memory. Using patch clamp recordings in mouse hippocampal slices, here we show that young neuron hyper-excitability is also observed at presynaptic mossy fiber terminals onto CA3 pyramidal neurons. However, action potential waveforms mature faster in the bouton than in the soma, suggesting rapid efferent functionality during immature stages.
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Affiliation(s)
- Nicholas P Vyleta
- Department of Psychology, Djavad Mowafaghian Center for Brain Health, University of British Columbia, Vancouver, BC, Canada
| | - Jason S Snyder
- Department of Psychology, Djavad Mowafaghian Center for Brain Health, University of British Columbia, Vancouver, BC, Canada.
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4
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Hauser D, Behr K, Konno K, Schreiner D, Schmidt A, Watanabe M, Bischofberger J, Scheiffele P. Targeted proteoform mapping uncovers specific Neurexin-3 variants required for dendritic inhibition. Neuron 2022; 110:2094-2109.e10. [PMID: 35550065 PMCID: PMC9275415 DOI: 10.1016/j.neuron.2022.04.017] [Citation(s) in RCA: 16] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2021] [Revised: 02/05/2022] [Accepted: 04/15/2022] [Indexed: 12/21/2022]
Abstract
The diversification of cell adhesion molecules by alternative splicing is proposed to underlie molecular codes for neuronal wiring. Transcriptomic approaches mapped detailed cell-type-specific mRNA splicing programs. However, it has been hard to probe the synapse-specific localization and function of the resulting protein splice isoforms, or “proteoforms,” in vivo. We here apply a proteoform-centric workflow in mice to test the synapse-specific functions of the splice isoforms of the synaptic adhesion molecule Neurexin-3 (NRXN3). We uncover a major proteoform, NRXN3 AS5, that is highly expressed in GABAergic interneurons and at dendrite-targeting GABAergic terminals. NRXN3 AS5 abundance significantly diverges from Nrxn3 mRNA distribution and is gated by translation-repressive elements. Nrxn3 AS5 isoform deletion results in a selective impairment of dendrite-targeting interneuron synapses in the dentate gyrus without affecting somatic inhibition or glutamatergic perforant-path synapses. This work establishes cell- and synapse-specific functions of a specific neurexin proteoform and highlights the importance of alternative splicing regulation for synapse specification. Translational regulation guides alternative Neurexin proteoform expression NRXN3 AS5 proteoforms are concentrated at dendrite-targeting interneuron synapses A proteome-centric workflow uncovers NRXN3 AS5 interactors in vivo Loss of NRXN3 AS5 leads to selective impairments in dendritic inhibition
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Affiliation(s)
- David Hauser
- Biozentrum of the University of Basel, Spitalstrasse 41, 4056 Basel, Switzerland
| | - Katharina Behr
- Department of Biomedicine, University of Basel, Pestalozzistrasse 20, 4056 Basel, Switzerland
| | - Kohtarou Konno
- Department of Anatomy, Faculty of Medicine, Hokkaido University, Sapporo, Japan
| | - Dietmar Schreiner
- Biozentrum of the University of Basel, Spitalstrasse 41, 4056 Basel, Switzerland
| | - Alexander Schmidt
- Biozentrum of the University of Basel, Spitalstrasse 41, 4056 Basel, Switzerland
| | - Masahiko Watanabe
- Department of Anatomy, Faculty of Medicine, Hokkaido University, Sapporo, Japan
| | - Josef Bischofberger
- Department of Biomedicine, University of Basel, Pestalozzistrasse 20, 4056 Basel, Switzerland
| | - Peter Scheiffele
- Biozentrum of the University of Basel, Spitalstrasse 41, 4056 Basel, Switzerland.
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5
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Pampaloni NP, Plested AJR. Slow excitatory synaptic currents generated by AMPA receptors. J Physiol 2021; 600:217-232. [PMID: 34587649 DOI: 10.1113/jp280877] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2021] [Accepted: 09/01/2021] [Indexed: 12/28/2022] Open
Abstract
Decades of literature indicate that the AMPA-type glutamate receptor is among the fastest acting of all neurotransmitter receptors. These receptors are located at excitatory synapses, and conventional wisdom says that they activate in hundreds of microseconds, deactivate in milliseconds due to their low affinity for glutamate and also desensitize profoundly. These properties circumscribe AMPA receptor activation in both space and time. However, accumulating evidence shows that AMPA receptors can also activate with slow, indefatigable responses. They do so through interactions with auxiliary subunits that are able promote a switch to a high open probability, high-conductance 'superactive' mode. In this review, we show that any assumption that this phenomenon is limited to heterologous expression is false and rather that slow AMPA currents have been widely and repeatedly observed throughout the nervous system. Hallmarks of the superactive mode are a lack of desensitization, resistance to competitive antagonists and a current decay that outlives free glutamate by hundreds of milliseconds. Because the switch to the superactive mode is triggered by activation, AMPA receptors can generate accumulating 'pedestal' currents in response to repetitive stimulation, constituting a postsynaptic mechanism for short-term potentiation in the range 5-100 Hz. Further, slow AMPA currents span 'cognitive' time intervals in the 100 ms range (theta rhythms), of particular interest for hippocampal function, where slow AMPA currents are widely expressed in a synapse-specific manner. Here, we outline the implications that slow AMPA receptors have for excitatory synaptic transmission and computation in the nervous system.
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Affiliation(s)
- Niccolò P Pampaloni
- Institute of Biology, Cellular Biophysics, Humboldt Universität zu Berlin, Berlin, Germany.,Leibniz-Forschungsinstitut für Molekulare Pharmakologie, Berlin, Germany.,NeuroCure Cluster of Excellence, Charité - Universitätsmedizin Berlin, corporate member of Freie Universität Berlin and Humboldt Universität zu Berlin, and Berlin Institute of Health, Charitéplatz 1, Berlin, Germany
| | - Andrew J R Plested
- Institute of Biology, Cellular Biophysics, Humboldt Universität zu Berlin, Berlin, Germany.,Leibniz-Forschungsinstitut für Molekulare Pharmakologie, Berlin, Germany.,NeuroCure Cluster of Excellence, Charité - Universitätsmedizin Berlin, corporate member of Freie Universität Berlin and Humboldt Universität zu Berlin, and Berlin Institute of Health, Charitéplatz 1, Berlin, Germany
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6
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Ceanga M, Dahab M, Witte OW, Keiner S. Adult Neurogenesis and Stroke: A Tale of Two Neurogenic Niches. Front Neurosci 2021; 15:700297. [PMID: 34447293 PMCID: PMC8382802 DOI: 10.3389/fnins.2021.700297] [Citation(s) in RCA: 23] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2021] [Accepted: 06/30/2021] [Indexed: 01/17/2023] Open
Abstract
In the aftermath of an acute stroke, numerous signaling cascades that reshape the brain both in the perilesional zone as well as in more distal regions are activated. Despite continuous improvement in the acute treatment of stroke and the sustained research efforts into the pathophysiology of stroke, we critically lag in our integrated understanding of the delayed and chronic responses to ischemic injury. As such, the beneficial or maladaptive effect of some stroke-induced cellular responses is unclear, restricting the advancement of therapeutic strategies to target long-term complications. A prominent delayed effect of stroke is the robust increase in adult neurogenesis, which raises hopes for a regenerative strategy to counter neurological deficits in stroke survivors. In the adult brain, two regions are known to generate new neurons from endogenous stem cells: the subventricular zone (SVZ) and the dentate subgranular zone (SGZ) of the hippocampus. While both niches respond with an increase in neurogenesis post-stroke, there are significant regional differences in the ensuing stages of survival, migration, and maturation, which may differently influence functional outcome. External interventions such as rehabilitative training add a further layer of complexity by independently modulating the process of adult neurogenesis. In this review we summarize the current knowledge regarding the effects of ischemic stroke on neurogenesis in the SVZ and in the SGZ, and the influence of exogenous stimuli such as motor activity or enriched environment (EE). In addition, we discuss the contribution of SVZ or SGZ post-stroke neurogenesis to sensory, motor and cognitive recovery.
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Affiliation(s)
- Mihai Ceanga
- Hans-Berger Department of Neurology, Jena University Hospital, Jena, Germany.,Section Translational Neuroimmunology, Department of Neurology, Jena University Hospital, Jena, Germany
| | - Mahmoud Dahab
- Hans-Berger Department of Neurology, Jena University Hospital, Jena, Germany
| | - Otto W Witte
- Hans-Berger Department of Neurology, Jena University Hospital, Jena, Germany
| | - Silke Keiner
- Hans-Berger Department of Neurology, Jena University Hospital, Jena, Germany
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7
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Pampaloni NP, Riva I, Carbone AL, Plested AJR. Slow AMPA receptors in hippocampal principal cells. Cell Rep 2021; 36:109496. [PMID: 34348150 PMCID: PMC8356020 DOI: 10.1016/j.celrep.2021.109496] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2020] [Revised: 06/01/2021] [Accepted: 07/14/2021] [Indexed: 01/22/2023] Open
Abstract
Glutamate receptor ion channels, including α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors, mediate fast excitatory neurotransmission in the CNS. Previous work suggested that AMPA receptors produce a synaptic current with a millisecond duration. However, we find that about two-thirds of principal cells in the hippocampal CA1 region also express AMPA receptors with reduced desensitization that can stay active for half a second after repetitive stimuli. These slow AMPA receptors are expressed at about half of the synapses, with a flat spatial distribution. The increased charge transfer from slow AMPA receptors allows short-term potentiation from a postsynaptic locus and reliable triggering of action potentials. Biophysical and pharmacological observations imply slow AMPA receptors incorporate auxiliary proteins, and their activation lengthens miniature synaptic currents. These data indicate that AMPA receptors are a major source of synaptic diversity. Synapses harboring slow AMPA receptors could have unique roles in hippocampal function.
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Affiliation(s)
- Niccolò P Pampaloni
- Molecular Neuroscience and Biophysics, Leibniz Forschungsinstitut für Molekulare Pharmakologie (FMP), 13125 Berlin, Germany; Charité-Universitätsmedizin Berlin, corporate member of Freie Universität Berlin and Humboldt-Universität zu Berlin, and Berlin Institute of Health, NeuroCure Cluster of Excellence, Charitéplatz 1, 10117 Berlin, Germany; Institute of Biology, Cellular Biophysics, Humboldt Universität zu Berlin, 10115 Berlin, Germany
| | - Irene Riva
- Molecular Neuroscience and Biophysics, Leibniz Forschungsinstitut für Molekulare Pharmakologie (FMP), 13125 Berlin, Germany; Charité-Universitätsmedizin Berlin, corporate member of Freie Universität Berlin and Humboldt-Universität zu Berlin, and Berlin Institute of Health, NeuroCure Cluster of Excellence, Charitéplatz 1, 10117 Berlin, Germany; Institute of Biology, Cellular Biophysics, Humboldt Universität zu Berlin, 10115 Berlin, Germany
| | - Anna L Carbone
- Molecular Neuroscience and Biophysics, Leibniz Forschungsinstitut für Molekulare Pharmakologie (FMP), 13125 Berlin, Germany; Charité-Universitätsmedizin Berlin, corporate member of Freie Universität Berlin and Humboldt-Universität zu Berlin, and Berlin Institute of Health, NeuroCure Cluster of Excellence, Charitéplatz 1, 10117 Berlin, Germany
| | - Andrew J R Plested
- Molecular Neuroscience and Biophysics, Leibniz Forschungsinstitut für Molekulare Pharmakologie (FMP), 13125 Berlin, Germany; Charité-Universitätsmedizin Berlin, corporate member of Freie Universität Berlin and Humboldt-Universität zu Berlin, and Berlin Institute of Health, NeuroCure Cluster of Excellence, Charitéplatz 1, 10117 Berlin, Germany; Institute of Biology, Cellular Biophysics, Humboldt Universität zu Berlin, 10115 Berlin, Germany.
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8
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Pagano J, Giona F, Beretta S, Verpelli C, Sala C. N-methyl-d-aspartate receptor function in neuronal and synaptic development and signaling. Curr Opin Pharmacol 2021; 56:93-101. [PMID: 33429227 DOI: 10.1016/j.coph.2020.12.006] [Citation(s) in RCA: 22] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2020] [Revised: 12/01/2020] [Accepted: 12/04/2020] [Indexed: 02/08/2023]
Abstract
The N-methyl-d-aspartate (NMDA) receptor, among the ionotropic glutamate receptors, are fundamental to integrating and transducing complex signaling in neurons. Glutamate activation of these receptors mediates intracellular signals essential to neuronal and synaptic formation and synaptic plasticity and also contribute to excitotoxic processes in several neurological disorders. The NMDA receptor signaling is mediated by the permeability to Ca2+ and by the large network of signaling and scaffolding proteins associated mostly with the large C-terminal domain of GluN2 subunits. Important studies showed that GluN2 C-terminal interactions differ in accordance with the GluN2 subtype, and this influences the type of signaling that NMDA receptor activity controls. Thus, it is not surprising that mutations in genes that codify for NMDA receptor subunits have been associated with severe neuronal diseases. We will review recent advances and explore outstanding problems in this active area of research.
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Affiliation(s)
- Jessica Pagano
- CNR Neuroscience Institute, Milano and NeuroMi Milan Center for Neuroscience, University of Milano-Bicocca, Milan, Italy
| | - Federica Giona
- CNR Neuroscience Institute, Milano and NeuroMi Milan Center for Neuroscience, University of Milano-Bicocca, Milan, Italy
| | - Stefania Beretta
- CNR Neuroscience Institute, Milano and NeuroMi Milan Center for Neuroscience, University of Milano-Bicocca, Milan, Italy
| | - Chiara Verpelli
- CNR Neuroscience Institute, Milano and NeuroMi Milan Center for Neuroscience, University of Milano-Bicocca, Milan, Italy
| | - Carlo Sala
- CNR Neuroscience Institute, Milano and NeuroMi Milan Center for Neuroscience, University of Milano-Bicocca, Milan, Italy.
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9
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Stroke Accelerates and Uncouples Intrinsic and Synaptic Excitability Maturation of Mouse Hippocampal DCX + Adult-Born Granule Cells. J Neurosci 2019; 39:1755-1766. [PMID: 30617211 DOI: 10.1523/jneurosci.3303-17.2018] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2017] [Revised: 11/05/2018] [Accepted: 11/08/2018] [Indexed: 11/21/2022] Open
Abstract
Stroke robustly stimulates adult neurogenesis in the hippocampal dentate gyrus. It is currently unknown whether this process induces beneficial or maladaptive effects, but morphological and behavioral studies have reported aberrant neurogenesis and impaired hippocampal-dependent memory following stroke. However, the intrinsic function and network incorporation of adult-born granule cells (ABGCs) after ischemia is unclear. Using patch-clamp electrophysiology, we evaluated doublecortin-positive (DCX+) ABGCs as well as DCX- dentate gyrus granule cells 2 weeks after a stroke or sham operation in DCX/DsRed transgenic mice of either sex. The developmental status, intrinsic excitability, and synaptic excitability of ABGCs were accelerated following stroke, while dendritic morphology was not aberrant. Regression analysis revealed uncoupled development of intrinsic and network excitability, resulting in young, intrinsically hyperexcitable ABGCs receiving disproportionately large glutamatergic inputs. This aberrant functional maturation in the subgroup of ABGCs in the hippocampus may contribute to defective hippocampal function and increased seizure susceptibility following stroke.SIGNIFICANCE STATEMENT Stroke increases hippocampal neurogenesis but the functional consequences of the postlesional response is mostly unclear. Our findings provide novel evidence of aberrant functional maturation of newly generated neurons following stroke. We demonstrate that stroke not only causes an accelerated maturation of the intrinsic and synaptic parameters of doublecortin-positive, new granule cells in the hippocampus, but that this accelerated development does not follow physiological dynamics due to uncoupled intrinsic and synaptic maturation. Hyperexcitable immature neurons may contribute to disrupted network integration following stroke.
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10
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Verstraelen P, Van Dyck M, Verschuuren M, Kashikar ND, Nuydens R, Timmermans JP, De Vos WH. Image-Based Profiling of Synaptic Connectivity in Primary Neuronal Cell Culture. Front Neurosci 2018; 12:389. [PMID: 29997468 PMCID: PMC6028601 DOI: 10.3389/fnins.2018.00389] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2017] [Accepted: 05/22/2018] [Indexed: 12/04/2022] Open
Abstract
Neurological disorders display a broad spectrum of clinical manifestations. Yet, at the cellular level, virtually all these diseases converge into a common phenotype of dysregulated synaptic connectivity. In dementia, synapse dysfunction precedes neurodegeneration and cognitive impairment by several years, making the synapse a crucial entry point for the development of diagnostic and therapeutic strategies. Whereas high-resolution imaging and biochemical fractionations yield detailed insight into the molecular composition of the synapse, standardized assays are required to quickly gauge synaptic connectivity across large populations of cells under a variety of experimental conditions. Such screening capabilities have now become widely accessible with the advent of high-throughput, high-content microscopy. In this review, we discuss how microscopy-based approaches can be used to extract quantitative information about synaptic connectivity in primary neurons with deep coverage. We elaborate on microscopic readouts that may serve as a proxy for morphofunctional connectivity and we critically analyze their merits and limitations. Finally, we allude to the potential of alternative culture paradigms and integrative approaches to enable comprehensive profiling of synaptic connectivity.
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Affiliation(s)
- Peter Verstraelen
- Laboratory of Cell Biology and Histology, Department of Veterinary Sciences, University of Antwerp, Antwerp, Belgium
| | - Michiel Van Dyck
- Laboratory of Cell Biology and Histology, Department of Veterinary Sciences, University of Antwerp, Antwerp, Belgium
| | - Marlies Verschuuren
- Laboratory of Cell Biology and Histology, Department of Veterinary Sciences, University of Antwerp, Antwerp, Belgium
| | | | - Rony Nuydens
- Janssen Research and Development, Janssen Pharmaceutica N.V., Beerse, Belgium
| | - Jean-Pierre Timmermans
- Laboratory of Cell Biology and Histology, Department of Veterinary Sciences, University of Antwerp, Antwerp, Belgium
| | - Winnok H. De Vos
- Laboratory of Cell Biology and Histology, Department of Veterinary Sciences, University of Antwerp, Antwerp, Belgium
- Cell Systems and Imaging, Department of Molecular Biotechnology, Ghent University, Ghent, Belgium
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11
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Li L, Sultan S, Heigele S, Schmidt-Salzmann C, Toni N, Bischofberger J. Silent synapses generate sparse and orthogonal action potential firing in adult-born hippocampal granule cells. eLife 2017; 6:23612. [PMID: 28826488 PMCID: PMC5580881 DOI: 10.7554/elife.23612] [Citation(s) in RCA: 38] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2016] [Accepted: 08/07/2017] [Indexed: 12/12/2022] Open
Abstract
In adult neurogenesis young neurons connect to the existing network via formation of thousands of new synapses. At early developmental stages, glutamatergic synapses are sparse, immature and functionally 'silent', expressing mainly NMDA receptors. Here we show in 2- to 3-week-old young neurons of adult mice, that brief-burst activity in glutamatergic fibers is sufficient to induce postsynaptic AP firing in the absence of AMPA receptors. The enhanced excitability of the young neurons lead to efficient temporal summation of small NMDA currents, dynamic unblocking of silent synapses and NMDA-receptor-dependent AP firing. Therefore, early synaptic inputs are powerfully converted into reliable spiking output. Furthermore, due to high synaptic gain, small dendritic trees and sparse connectivity, neighboring young neurons are activated by different distinct subsets of afferent fibers with minimal overlap. Taken together, synaptic recruitment of young neurons generates sparse and orthogonal AP firing, which may support sparse coding during hippocampal information processing.
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Affiliation(s)
- Liyi Li
- Department of Biomedicine, University of Basel, Basel, Switzerland
| | - Sébastien Sultan
- Department of Fundamental Neurosciences, University of Lausanne, Lausanne, Switzerland
| | - Stefanie Heigele
- Department of Biomedicine, University of Basel, Basel, Switzerland
| | | | - Nicolas Toni
- Department of Fundamental Neurosciences, University of Lausanne, Lausanne, Switzerland
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12
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Negi SK, Guda C. Global gene expression profiling of healthy human brain and its application in studying neurological disorders. Sci Rep 2017; 7:897. [PMID: 28420888 PMCID: PMC5429860 DOI: 10.1038/s41598-017-00952-9] [Citation(s) in RCA: 39] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2016] [Accepted: 03/20/2017] [Indexed: 12/31/2022] Open
Abstract
Brain function is governed by precise regulation of gene expression across its anatomically distinct structures; however, the expression patterns of genes across hundreds of brain structures are not clearly understood. Here, we describe a gene expression model, which is representative of the healthy human brain transcriptome by using data from the Allen Brain Atlas. Our in-depth gene expression profiling revealed that 84% of genes are expressed in at least one of the 190 brain structures studied. Hierarchical clustering based on gene expression profiles delineated brain regions into structurally tiered spatial groups and we observed striking enrichment for region-specific processes. Further, weighted co-expression network analysis identified 19 robust modules of highly correlated genes enriched with functional associations for neurogenesis, dopamine signaling, immune regulation and behavior. Also, structural distribution maps of major neurotransmission systems in the brain were generated. Finally, we developed a supervised classification model, which achieved 84% and 81% accuracies for predicting autism- and Parkinson’s-implicated genes, respectively, using our expression model as a baseline. This study represents the first use of global gene expression profiling from healthy human brain to develop a disease gene prediction model and this generic methodology can be applied to study any neurological disorder.
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Affiliation(s)
- Simarjeet K Negi
- Department of Genetics, Cell Biology and Anatomy, University of Nebraska Medical Center, Omaha, NE, 68198, USA
| | - Chittibabu Guda
- Department of Genetics, Cell Biology and Anatomy, University of Nebraska Medical Center, Omaha, NE, 68198, USA. .,Bioinformatics and Systems Biology Core, University of Nebraska Medical Center, Omaha, NE, 68198, USA. .,Department of Biochemistry and Molecular Biology, University of Nebraska Medical Center, Omaha, NE, 68198, USA. .,Fred and Pamela Buffet Cancer Center, University of Nebraska Medical Center, Omaha, NE, 68198, USA.
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13
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Bergström P, Agholme L, Nazir FH, Satir TM, Toombs J, Wellington H, Strandberg J, Bontell TO, Kvartsberg H, Holmström M, Boreström C, Simonsson S, Kunath T, Lindahl A, Blennow K, Hanse E, Portelius E, Wray S, Zetterberg H. Amyloid precursor protein expression and processing are differentially regulated during cortical neuron differentiation. Sci Rep 2016; 6:29200. [PMID: 27383650 PMCID: PMC4935877 DOI: 10.1038/srep29200] [Citation(s) in RCA: 52] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2016] [Accepted: 06/14/2016] [Indexed: 12/15/2022] Open
Abstract
Amyloid precursor protein (APP) and its cleavage product amyloid β (Aβ) have been thoroughly studied in Alzheimer’s disease. However, APP also appears to be important for neuronal development. Differentiation of induced pluripotent stem cells (iPSCs) towards cortical neurons enables in vitro mechanistic studies on human neuronal development. Here, we investigated expression and proteolytic processing of APP during differentiation of human iPSCs towards cortical neurons over a 100-day period. APP expression remained stable during neuronal differentiation, whereas APP processing changed. α-Cleaved soluble APP (sAPPα) was secreted early during differentiation, from neuronal progenitors, while β-cleaved soluble APP (sAPPβ) was first secreted after deep-layer neurons had formed. Short Aβ peptides, including Aβ1-15/16, peaked during the progenitor stage, while processing shifted towards longer peptides, such as Aβ1-40/42, when post-mitotic neurons appeared. This indicates that APP processing is regulated throughout differentiation of cortical neurons and that amyloidogenic APP processing, as reflected by Aβ1-40/42, is associated with mature neuronal phenotypes.
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Affiliation(s)
- Petra Bergström
- Institute of Neuroscience and Physiology, Department of Psychiatry and Neurochemistry, The Sahlgrenska Academy at the University of Gothenburg, S-405 30, Gothenburg, Sweden
| | - Lotta Agholme
- Institute of Neuroscience and Physiology, Department of Psychiatry and Neurochemistry, The Sahlgrenska Academy at the University of Gothenburg, S-405 30, Gothenburg, Sweden
| | - Faisal Hayat Nazir
- Institute of Neuroscience and Physiology, Department of Psychiatry and Neurochemistry, The Sahlgrenska Academy at the University of Gothenburg, S-405 30, Gothenburg, Sweden
| | - Tugce Munise Satir
- Institute of Neuroscience and Physiology, Department of Psychiatry and Neurochemistry, The Sahlgrenska Academy at the University of Gothenburg, S-405 30, Gothenburg, Sweden
| | - Jamie Toombs
- UCL Institute of Neurology, Department of Molecular Neuroscience, University College London, Queen Square, London, WC1N 3BG, UK
| | - Henrietta Wellington
- UCL Institute of Neurology, Department of Molecular Neuroscience, University College London, Queen Square, London, WC1N 3BG, UK
| | - Joakim Strandberg
- Institute of Neuroscience and Physiology, Department of Physiology, The Sahlgrenska Academy at the University of Gothenburg, S-405 30, Gothenburg, Sweden
| | - Thomas Olsson Bontell
- Institute of Neuroscience and Physiology, Department of Physiology, The Sahlgrenska Academy at the University of Gothenburg, S-405 30, Gothenburg, Sweden.,Department of Clinical Pathology and Cytology, Sahlgrenska University Hospital, S-413 45, Gothenburg, Sweden
| | - Hlin Kvartsberg
- Institute of Neuroscience and Physiology, Department of Psychiatry and Neurochemistry, The Sahlgrenska Academy at the University of Gothenburg, S-431 80, Mölndal, Sweden
| | - Maria Holmström
- Institute of Neuroscience and Physiology, Department of Psychiatry and Neurochemistry, The Sahlgrenska Academy at the University of Gothenburg, S-405 30, Gothenburg, Sweden
| | - Cecilia Boreström
- Institute of Biomedicine, Department of Clinical Chemistry and Transfusion Medicine, The Sahlgrenska Academy at the University of Gothenburg, S-405 30, Gothenburg, Sweden
| | - Stina Simonsson
- Institute of Biomedicine, Department of Clinical Chemistry and Transfusion Medicine, The Sahlgrenska Academy at the University of Gothenburg, S-405 30, Gothenburg, Sweden
| | - Tilo Kunath
- MRC Centre for Regenerative Medicine, School of Biological Sciences, University of Edinburgh, Edinburgh, EH16 4UU, UK
| | - Anders Lindahl
- Institute of Biomedicine, Department of Clinical Chemistry and Transfusion Medicine, The Sahlgrenska Academy at the University of Gothenburg, S-405 30, Gothenburg, Sweden
| | - Kaj Blennow
- Institute of Neuroscience and Physiology, Department of Psychiatry and Neurochemistry, The Sahlgrenska Academy at the University of Gothenburg, S-431 80, Mölndal, Sweden
| | - Eric Hanse
- Institute of Neuroscience and Physiology, Department of Physiology, The Sahlgrenska Academy at the University of Gothenburg, S-405 30, Gothenburg, Sweden
| | - Erik Portelius
- Institute of Neuroscience and Physiology, Department of Psychiatry and Neurochemistry, The Sahlgrenska Academy at the University of Gothenburg, S-431 80, Mölndal, Sweden
| | - Selina Wray
- UCL Institute of Neurology, Department of Molecular Neuroscience, University College London, Queen Square, London, WC1N 3BG, UK
| | - Henrik Zetterberg
- UCL Institute of Neurology, Department of Molecular Neuroscience, University College London, Queen Square, London, WC1N 3BG, UK.,Institute of Neuroscience and Physiology, Department of Psychiatry and Neurochemistry, The Sahlgrenska Academy at the University of Gothenburg, S-431 80, Mölndal, Sweden
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14
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Distinct Defects in Synaptic Differentiation of Neocortical Neurons in Response to Prenatal Valproate Exposure. Sci Rep 2016; 6:27400. [PMID: 27264355 PMCID: PMC4893673 DOI: 10.1038/srep27400] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2016] [Accepted: 05/18/2016] [Indexed: 01/17/2023] Open
Abstract
Autism spectrum disorders (ASDs) are a heterogeneous group of neurodevelopmental disorders characterized by impairments in social interactions and stereotyped behaviors. Valproic acid (VPA) is frequently used to treat epilepsy and bipolar disorders. When taken during pregnancy, VPA increases the risk of the unborn child to develop an ASD. In rodents, in utero VPA exposure can precipitate behavioral phenotypes related to ASD in the offspring. Therefore, such rodent models may allow for identification of synaptic pathophysiology underlying ASD risk. Here, we systematically probed alterations in synaptic proteins that might contribute to autism-related behavior in the offspring of in utero VPA-exposed mice. Moreover, we tested whether direct VPA exposure of cultured neocortical neurons may recapitulate the molecular alterations seen in vivo. VPA-exposed neurons in culture exhibit a significant increase in the number of glutamatergic synapses accompanied by a significant decrease in the number of GABAergic synapses. This shift in excitatory/inhibitory balance results in substantially increased spontaneous activity in neuronal networks arising from VPA-exposed neurons. Pharmacological experiments demonstrate that the alterations in GABAergic and glutamatergic synaptic proteins and structures are largely caused by inhibition of histone deacetylases. Therefore, our study highlights an epigenetic mechanism underlying the synaptic pathophysiology in this ASD model.
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15
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Low excitatory innervation balances high intrinsic excitability of immature dentate neurons. Nat Commun 2016; 7:11313. [PMID: 27095423 PMCID: PMC4843000 DOI: 10.1038/ncomms11313] [Citation(s) in RCA: 62] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2016] [Accepted: 03/11/2016] [Indexed: 01/22/2023] Open
Abstract
Persistent neurogenesis in the dentate gyrus produces immature neurons with high intrinsic excitability and low levels of inhibition that are predicted to be more broadly responsive to afferent activity than mature neurons. Mounting evidence suggests that these immature neurons are necessary for generating distinct neural representations of similar contexts, but it is unclear how broadly responsive neurons help distinguish between similar patterns of afferent activity. Here we show that stimulation of the entorhinal cortex in mouse brain slices paradoxically generates spiking of mature neurons in the absence of immature neuron spiking. Immature neurons with high intrinsic excitability fail to spike due to insufficient excitatory drive that results from low innervation rather than silent synapses or low release probability. Our results suggest that low synaptic connectivity prevents immature neurons from responding broadly to cortical activity, potentially enabling excitable immature neurons to contribute to sparse and orthogonal dentate representations. Immature dentate gyrus neurons are highly excitable and are thought to be more responsive to afferent activity than mature neurons. Here, the authors find stimulation of the entorhinal cortex paradoxically generates spiking in mature rather than immature neurons due to low synaptic connectivity of immature cells.
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16
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Transcriptional Profiling of Newly Generated Dentate Granule Cells Using TU Tagging Reveals Pattern Shifts in Gene Expression during Circuit Integration. eNeuro 2016; 3:eN-NWR-0024-16. [PMID: 27011954 PMCID: PMC4797955 DOI: 10.1523/eneuro.0024-16.2016] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2016] [Accepted: 02/04/2016] [Indexed: 11/21/2022] Open
Abstract
Despite representing only a small fraction of hippocampal granule cells, adult-generated newborn granule cells have been implicated in learning and memory (Aimone et al., 2011). Newborn granule cells undergo functional maturation and circuit integration over a period of weeks. However, it is difficult to assess the accompanying gene expression profiles in vivo with high spatial and temporal resolution using traditional methods. Here we used a novel method ["thiouracil (TU) tagging"] to map the profiles of nascent mRNAs in mouse immature newborn granule cells compared with mature granule cells. We targeted a nonmammalian uracil salvage enzyme, uracil phosphoribosyltransferase, to newborn neurons and mature granule cells using retroviral and lentiviral constructs, respectively. Subsequent injection of 4-TU tagged nascent RNAs for analysis by RNA sequencing. Several hundred genes were significantly enhanced in the retroviral dataset compared with the lentiviral dataset. We compared a selection of the enriched genes with steady-state levels of mRNAs using quantitative PCR. Ontology analysis revealed distinct patterns of nascent mRNA expression, with newly generated immature neurons showing enhanced expression for genes involved in synaptic function, and neural differentiation and development, as well as genes not previously associated with granule cell maturation. Surprisingly, the nascent mRNAs enriched in mature cells were related to energy homeostasis and metabolism, presumably indicative of the increased energy demands of synaptic transmission and their complex dendritic architecture. The high spatial and temporal resolution of our modified TU-tagging method provides a foundation for comparison with steady-state RNA analyses by traditional transcriptomic approaches in defining the functional roles of newborn neurons.
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17
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Sultan S, Li L, Moss J, Petrelli F, Cassé F, Gebara E, Lopatar J, Pfrieger FW, Bezzi P, Bischofberger J, Toni N. Synaptic Integration of Adult-Born Hippocampal Neurons Is Locally Controlled by Astrocytes. Neuron 2015; 88:957-972. [PMID: 26606999 DOI: 10.1016/j.neuron.2015.10.037] [Citation(s) in RCA: 188] [Impact Index Per Article: 20.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2015] [Revised: 09/23/2015] [Accepted: 10/13/2015] [Indexed: 01/20/2023]
Abstract
Adult neurogenesis is regulated by the neurogenic niche, through mechanisms that remain poorly defined. Here, we investigated whether niche-constituting astrocytes influence the maturation of adult-born hippocampal neurons using two independent transgenic approaches to block vesicular release from astrocytes. In these models, adult-born neurons but not mature neurons showed reduced glutamatergic synaptic input and dendritic spine density that was accompanied with lower functional integration and cell survival. By taking advantage of the mosaic expression of transgenes in astrocytes, we found that spine density was reduced exclusively in segments intersecting blocked astrocytes, revealing an extrinsic, local control of spine formation. Defects in NMDA receptor (NMDAR)-mediated synaptic transmission and dendrite maturation were partially restored by exogenous D-serine, whose extracellular level was decreased in transgenic models. Together, these results reveal a critical role for adult astrocytes in local dendritic spine maturation, which is necessary for the NMDAR-dependent functional integration of newborn neurons.
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Affiliation(s)
- Sébastien Sultan
- University of Lausanne, Department of Fundamental Neurosciences, 9 rue du Bugnon, 1005 Lausanne, Switzerland
| | - Liyi Li
- Department of Biomedicine, Physiological Institute, University of Basel, Pestalozzistrasse 20, 4056 Basel, Switzerland
| | - Jonathan Moss
- University of Lausanne, Department of Fundamental Neurosciences, 9 rue du Bugnon, 1005 Lausanne, Switzerland
| | - Francesco Petrelli
- University of Lausanne, Department of Fundamental Neurosciences, 9 rue du Bugnon, 1005 Lausanne, Switzerland
| | - Frédéric Cassé
- University of Lausanne, Department of Fundamental Neurosciences, 9 rue du Bugnon, 1005 Lausanne, Switzerland
| | - Elias Gebara
- University of Lausanne, Department of Fundamental Neurosciences, 9 rue du Bugnon, 1005 Lausanne, Switzerland
| | - Jan Lopatar
- University of Lausanne, Department of Fundamental Neurosciences, 9 rue du Bugnon, 1005 Lausanne, Switzerland
| | - Frank W Pfrieger
- CNRS UPR 3212, University of Strasbourg, Institute of Cellular and Integrative Neurosciences, 67084 Strasbourg, France
| | - Paola Bezzi
- University of Lausanne, Department of Fundamental Neurosciences, 9 rue du Bugnon, 1005 Lausanne, Switzerland
| | - Josef Bischofberger
- Department of Biomedicine, Physiological Institute, University of Basel, Pestalozzistrasse 20, 4056 Basel, Switzerland
| | - Nicolas Toni
- University of Lausanne, Department of Fundamental Neurosciences, 9 rue du Bugnon, 1005 Lausanne, Switzerland.
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18
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Mu Y, Zhao C, Toni N, Yao J, Gage FH. Distinct roles of NMDA receptors at different stages of granule cell development in the adult brain. eLife 2015; 4:e07871. [PMID: 26473971 PMCID: PMC4608052 DOI: 10.7554/elife.07871] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2015] [Accepted: 09/12/2015] [Indexed: 12/01/2022] Open
Abstract
NMDA receptor (NMDAR)-dependent forms of synaptic plasticity are thought to underlie the assembly of developing neuronal circuits and to play a crucial role in learning and memory. It remains unclear how NMDAR might contribute to the wiring of adult-born granule cells (GCs). Here we demonstrate that nascent GCs lacking NMDARs but rescued from apoptosis by overexpressing the pro-survival protein Bcl2 were deficient in spine formation. Insufficient spinogenesis might be a general cause of cell death restricted within the NMDAR-dependent critical time window for GC survival. NMDAR loss also led to enhanced mushroom spine formation and synaptic AMPAR activity throughout the development of newborn GCs. Moreover, similar elevated synapse maturation in the absence of NMDARs was observed in neonate-generated GCs and CA1 pyramidal neurons. Together, these data suggest that NMDAR operates as a molecular monitor for controlling the activity-dependent establishment and maturation rate of synaptic connections between newborn neurons and others. DOI:http://dx.doi.org/10.7554/eLife.07871.001 The brain contains billions of cells called neurons. Although most neurons have already formed by the time we are born, part of the brain called the hippocampus produces new neurons throughout our life. These new neurons are thought to be important for learning and forming new memories. Neurons send signals to each other across connections called synapses. Small protrusions called spines stick out of the neuron and each tends to have one synapse that receives a signal from another neuron. Via these connections, the neurons are organized into networks and circuits that control how different parts of the brain work. Therefore, once new neurons are made, they also need to be connected to the correct neurons. The NMDA receptor is found in the surface of neurons, and mutated neurons that lack this receptor often die shortly after birth. The NMDA receptor is also known to be important for organizing synapses. Exactly how NMDA receptors help new neurons to survive and integrate into circuits has not been investigated in detail. Mu, Zhao et al. now address this issue by using mice in which a gene called NR1, which produces one of the proteins that makes up the NMDA receptor, can be deleted at specific stages of neuron development. Analyzing brain slices from the mice showed that deleting NR1 from newly-formed neurons caused them to die within two or three weeks. When these neurons were forced to survive, they had fewer spines than normal. By contrast, deleting NR1 from neurons that has already survived for longer than four weeks did not alter how many spines the neurons had. Instead, the synapses on the spines worked better. Mu, Zhao et al. therefore suggest that NMDA receptors have different roles at different stages of a neuron's development. Initially, NMDA receptors help the neurons to survive and form spines. The receptors then help to ensure the spines become the correct size, and enable the neurons to connect into the right neural circuits by helping to control the strength of synapses. Mu, Zhao et al. theorize that the mere presence of NMDA receptors suppresses spine maturation. Furthermore, this inhibitory effect is only released when the NMDA receptor is activated, or when the NMDA receptor is absent due to the deletion of the NR1 gene. Further studies will be needed to validate this hypothesis. DOI:http://dx.doi.org/10.7554/eLife.07871.002
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Affiliation(s)
- Yangling Mu
- Department of Physiology, School of Basic Medicine, Huazhong University of Science and Technology, Wuhan, China.,Institute of Brain Research, Huazhong University of Science and Technology, Wuhan, China
| | - Chunmei Zhao
- Laboratory of Genetics, Salk Institute for Biological Studies, La Jolla, United States
| | - Nicolas Toni
- Department of Fundamental Neurosciences, University of Lausanne, Lausanne, Switzerland
| | - Jun Yao
- State Key Laboratory of Biomembrane and Membrane Biotechnology, Tsinghua-Peking Center for Life Sciences, School of Life Sciences, Tsinghua University, Beijing, China
| | - Fred H Gage
- Laboratory of Genetics, Salk Institute for Biological Studies, La Jolla, United States
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19
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Ferreira-Neto HC, Antunes VR, Stern JE. ATP stimulates rat hypothalamic sympathetic neurons by enhancing AMPA receptor-mediated currents. J Neurophysiol 2015; 114:159-69. [PMID: 25904713 PMCID: PMC4507951 DOI: 10.1152/jn.01011.2014] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2014] [Accepted: 04/19/2015] [Indexed: 01/12/2023] Open
Abstract
We have previously shown that ATP within the paraventricular nucleus (PVN) induces an increase in sympathetic activity, an effect attenuated by the antagonism of P2 and/or glutamatergic receptors. Here, we evaluated precise cellular mechanisms underlying the ATP-glutamate interaction in the PVN and assessed whether this receptor coupling contributed to osmotically driven sympathetic PVN neuronal activity. Whole-cell patch-clamp recordings obtained from PVN-rostral ventrolateral medulla neurons showed that ATP (100 μM, 1 min, bath applied) induced an increase in firing rate (89%), an effect blocked by kynurenic acid (1 mM) or 4-[[4-Formyl-5-hydroxy-6-methyl-3-[(phosphonooxy)methyl]-2-pyridinyl]azo]-1,3-benzenedisulfonic acid tetrasodium salt (PPADS) (10 μM). Whereas ATP did not affect glutamate synaptic function, α-amino-3-hydroxy-5-methylisoxazole propionic acid (AMPA) receptor-mediated currents evoked by focal application of AMPA (50 μM, n = 13) were increased in magnitude by ATP (AMPA amplitude: 33%, AMPA area: 52%). ATP potentiation of AMPA currents was blocked by PPADS (n = 12) and by chelation of intracellular Ca(2+) (BAPTA, n = 10). Finally, a hyperosmotic stimulus (mannitol 1%, +55 mosM, n = 8) potentiated evoked AMPA currents (53%), an effect blocked by PPADS (n = 6). Taken together, our data support a functional stimulatory coupling between P2 and AMPA receptors (likely of extrasynaptic location) in PVN sympathetic neurons, which is engaged in response to an acute hyperosmotic stimulus, which might contribute in turn to osmotically driven sympathoexcitatory responses by the PVN.
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Affiliation(s)
- Hildebrando Candido Ferreira-Neto
- Department of Physiology and Biophysics, Institute of Biomedical Sciences, University of Sao Paulo, Sao Paulo, Brazil; Department of Physiology, Georgia Regents University, Augusta, Georgia
| | - Vagner R Antunes
- Department of Physiology and Biophysics, Institute of Biomedical Sciences, University of Sao Paulo, Sao Paulo, Brazil
| | - Javier E Stern
- Department of Physiology, Georgia Regents University, Augusta, Georgia
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20
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Kannangara TS, Bostrom CA, Ratzlaff A, Thompson L, Cater RM, Gil-Mohapel J, Christie BR. Deletion of the NMDA receptor GluN2A subunit significantly decreases dendritic growth in maturing dentate granule neurons. PLoS One 2014; 9:e103155. [PMID: 25083703 PMCID: PMC4118862 DOI: 10.1371/journal.pone.0103155] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2014] [Accepted: 06/26/2014] [Indexed: 11/18/2022] Open
Abstract
It is known that NMDA receptors can modulate adult hippocampal neurogenesis, but the contribution of specific regulatory GluN2 subunits has been difficult to determine. Here we demonstrate that mice lacking GluN2A (formerly NR2A) do not show altered cell proliferation or neuronal differentiation, but present significant changes in neuronal morphology in dentate granule cells. Specifically, GluN2A deletion significantly decreased total dendritic length and dendritic complexity in DG neurons located in the inner granular zone. Furthermore, the absence of GluN2A also resulted in a localized increase in spine density in the middle molecular layer, a region innervated by the medial perforant path. Interestingly, alterations in dendritic morphology and spine density were never seen in dentate granule cells located in the outer granular zone, a region that has been hypothesized to contain older, more mature, neurons. These results indicate that although the GluN2A subunit is not critical for the cell proliferation and differentiation stages of the neurogenic process, it does appear to play a role in establishing synaptic and dendritic morphology in maturing dentate granule cells localized in the inner granular zone.
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Affiliation(s)
- Timal S. Kannangara
- Division of Medical Sciences, University of Victoria, Victoria, Canada
- Department of Cellular and Physiological Sciences, University of British Columbia, Victoria, Canada
- Graduate Program of Neuroscience and The Brain Research Centre, University of British Columbia, Victoria, Canada
| | - Crystal A. Bostrom
- Division of Medical Sciences, University of Victoria, Victoria, Canada
- Department of Biology, University of Victoria, Victoria, Canada
| | - Andrea Ratzlaff
- Division of Medical Sciences, University of Victoria, Victoria, Canada
- Department of Biology, University of Victoria, Victoria, Canada
| | - Lee Thompson
- Division of Medical Sciences, University of Victoria, Victoria, Canada
- Department of Biology, University of Victoria, Victoria, Canada
| | - Robyn M. Cater
- Division of Medical Sciences, University of Victoria, Victoria, Canada
- Department of Biology, University of Victoria, Victoria, Canada
| | - Joana Gil-Mohapel
- Division of Medical Sciences, University of Victoria, Victoria, Canada
| | - Brian R. Christie
- Division of Medical Sciences, University of Victoria, Victoria, Canada
- Department of Biology, University of Victoria, Victoria, Canada
- Neuroscience Graduate Program, University of Victoria, Victoria, Canada
- Department of Cellular and Physiological Sciences, University of British Columbia, Victoria, Canada
- Graduate Program of Neuroscience and The Brain Research Centre, University of British Columbia, Victoria, Canada
- * E-mail:
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