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Cerda-Jara CA, Kim SJ, Thomas G, Farsi Z, Zolotarov G, Dube G, Deter A, Bahry E, Georgii E, Woehler A, Piwecka M, Rajewsky N. miR-7 controls glutamatergic transmission and neuronal connectivity in a Cdr1as-dependent manner. EMBO Rep 2024:10.1038/s44319-024-00168-9. [PMID: 38831125 DOI: 10.1038/s44319-024-00168-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2024] [Revised: 04/12/2024] [Accepted: 05/14/2024] [Indexed: 06/05/2024] Open
Abstract
The circular RNA (circRNA) Cdr1as is conserved across mammals and highly expressed in neurons, where it directly interacts with microRNA miR-7. However, the biological function of this interaction is unknown. Here, using primary cortical murine neurons, we demonstrate that stimulating neurons by sustained depolarization rapidly induces two-fold transcriptional upregulation of Cdr1as and strong post-transcriptional stabilization of miR-7. Cdr1as loss causes doubling of glutamate release from stimulated synapses and increased frequency and duration of local neuronal bursts. Moreover, the periodicity of neuronal networks increases, and synchronicity is impaired. Strikingly, these effects are reverted by sustained expression of miR-7, which also clears Cdr1as molecules from neuronal projections. Consistently, without Cdr1as, transcriptomic changes caused by miR-7 overexpression are stronger (including miR-7-targets downregulation) and enriched in secretion/synaptic plasticity pathways. Altogether, our results suggest that in cortical neurons Cdr1as buffers miR-7 activity to control glutamatergic excitatory transmission and neuronal connectivity important for long-lasting synaptic adaptations.
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Affiliation(s)
- Cledi A Cerda-Jara
- Laboratory for Systems Biology of Gene Regulatory Elements, Berlin Institute for Medical Systems Biology, Max Delbrück Center for Molecular Medicine, Hannoversche Str. 28, 10115, Berlin, Germany
| | - Seung Joon Kim
- Laboratory for Systems Biology of Gene Regulatory Elements, Berlin Institute for Medical Systems Biology, Max Delbrück Center for Molecular Medicine, Hannoversche Str. 28, 10115, Berlin, Germany
| | - Gwendolin Thomas
- Laboratory for Systems Biology of Gene Regulatory Elements, Berlin Institute for Medical Systems Biology, Max Delbrück Center for Molecular Medicine, Hannoversche Str. 28, 10115, Berlin, Germany
| | - Zohreh Farsi
- Light Microscopy Platform, Berlin Institute for Medical Systems Biology, Max Delbrück Center for Molecular Medicine, Hannoversche Str. 28, 10115, Berlin, Germany
| | - Grygoriy Zolotarov
- Laboratory for Systems Biology of Gene Regulatory Elements, Berlin Institute for Medical Systems Biology, Max Delbrück Center for Molecular Medicine, Hannoversche Str. 28, 10115, Berlin, Germany
| | - Giuliana Dube
- Laboratory for Systems Biology of Gene Regulatory Elements, Berlin Institute for Medical Systems Biology, Max Delbrück Center for Molecular Medicine, Hannoversche Str. 28, 10115, Berlin, Germany
| | - Aylina Deter
- Laboratory for Systems Biology of Gene Regulatory Elements, Berlin Institute for Medical Systems Biology, Max Delbrück Center for Molecular Medicine, Hannoversche Str. 28, 10115, Berlin, Germany
| | - Ella Bahry
- Helmholtz Imaging, Max-Delbrück-Center for Molecular Medicine, Berlin, Germany Hannoversche Str. 28, 10115, Berlin, Germany
| | - Elisabeth Georgii
- Helmholtz AI, Helmholtz Zentrum München, Ingolstädter Landstraße 1, D-85764, Neuherberg, Germany
| | - Andrew Woehler
- Light Microscopy Platform, Berlin Institute for Medical Systems Biology, Max Delbrück Center for Molecular Medicine, Hannoversche Str. 28, 10115, Berlin, Germany
| | - Monika Piwecka
- Department of Non-Coding RNAs, Institute of Bioorganic Chemistry, Polish Academy of Sciences, Noskowskiego 12/14, 61-704, Poznan, Poland
| | - Nikolaus Rajewsky
- Laboratory for Systems Biology of Gene Regulatory Elements, Berlin Institute for Medical Systems Biology, Max Delbrück Center for Molecular Medicine, Hannoversche Str. 28, 10115, Berlin, Germany.
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2
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Ralowicz AJ, Hokeness S, Hoppa MB. Frequency of Spontaneous Neurotransmission at Individual Boutons Corresponds to the Size of the Readily Releasable Pool of Vesicles. J Neurosci 2024; 44:e1253232024. [PMID: 38383495 PMCID: PMC11063817 DOI: 10.1523/jneurosci.1253-23.2024] [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: 07/06/2023] [Revised: 02/09/2024] [Accepted: 02/13/2024] [Indexed: 02/23/2024] Open
Abstract
Synapses maintain two forms of neurotransmitter release to support communication in the brain. First, evoked neurotransmitter release is triggered by the invasion of an action potential (AP) across en passant boutons that form along axons. The probability of evoked release (Pr) varies substantially across boutons, even within a single axon. Such heterogeneity is the result of differences in the probability of a single synaptic vesicle (SV) fusing (Pv) and in the number of vesicles available for immediate release, known as the readily releasable pool (RRP). Spontaneous release (also known as a mini) is an important form of neurotransmission that occurs in the absence of APs. Because it cannot be triggered with electrical stimulation, much less is known about potential heterogeneity in the frequency of spontaneous release between boutons. We utilized a photostable and bright fluorescent indicator of glutamate release (iGluSnFR3) to quantify both spontaneous and evoked release at individual glutamatergic boutons. We found that the rate of spontaneous release is quite heterogenous at the level of individual boutons. Interestingly, when measuring both evoked and spontaneous release at single synapses, we found that boutons with the highest rates of spontaneous release also displayed the largest evoked responses. Using a new optical method to measure RRP at individual boutons, we found that this heterogeneity in spontaneous release was strongly correlated with the size of the RRP, but not related to Pv. We conclude that the RRP is a critical and dynamic aspect of synaptic strength that contributes to both evoked and spontaneous vesicle release.
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Affiliation(s)
- Amelia J Ralowicz
- Department of Biology, Dartmouth College, Hanover, New Hampshire 03755
| | - Sasipha Hokeness
- Department of Biology, Dartmouth College, Hanover, New Hampshire 03755
| | - Michael B Hoppa
- Department of Biology, Dartmouth College, Hanover, New Hampshire 03755
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3
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Joy MSH, Nall DL, Emon B, Lee KY, Barishman A, Ahmed M, Rahman S, Selvin PR, Saif MTA. Synapses without tension fail to fire in an in vitro network of hippocampal neurons. Proc Natl Acad Sci U S A 2023; 120:e2311995120. [PMID: 38113266 PMCID: PMC10756289 DOI: 10.1073/pnas.2311995120] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2023] [Accepted: 11/02/2023] [Indexed: 12/21/2023] Open
Abstract
Neurons in the brain communicate with each other at their synapses. It has long been understood that this communication occurs through biochemical processes. Here, we reveal that mechanical tension in neurons is essential for communication. Using in vitro rat hippocampal neurons, we find that 1) neurons become tout/tensed after forming synapses resulting in a contractile neural network, and 2) without this contractility, neurons fail to fire. To measure time evolution of network contractility in 3D (not 2D) extracellular matrix, we developed an ultrasensitive force sensor with 1 nN resolution. We employed Multi-Electrode Array and iGluSnFR, a glutamate sensor, to quantify neuronal firing at the network and at the single synapse scale, respectively. When neuron contractility is relaxed, both techniques show significantly reduced firing. Firing resumes when contractility is restored. This finding highlights the essential contribution of neural contractility in fundamental brain functions and has implications for our understanding of neural physiology.
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Affiliation(s)
- Md Saddam Hossain Joy
- Department of Mechanical Science and Engineering, University of Illinois Urbana-Champaign, Urbana, IL61801
| | - Duncan L. Nall
- Department of Physics and Center for Biophysics and Quantitative Biology, University of Illinois Urbana-Champaign, Urbana, IL61801
| | - Bashar Emon
- Department of Mechanical Science and Engineering, University of Illinois Urbana-Champaign, Urbana, IL61801
| | - Ki Yun Lee
- Department of Mechanical Science and Engineering, University of Illinois Urbana-Champaign, Urbana, IL61801
| | - Alexandra Barishman
- Department of Bioengineering, University of Illinois Urbana-Champaign, Urbana, IL61801
| | - Movviz Ahmed
- Department of Chemistry, University of Illinois Urbana-Champaign, Urbana, IL61801
| | - Saeedur Rahman
- Department of Mechanical Science and Engineering, University of Illinois Urbana-Champaign, Urbana, IL61801
| | - Paul R. Selvin
- Department of Physics and Center for Biophysics and Quantitative Biology, University of Illinois Urbana-Champaign, Urbana, IL61801
| | - M. Taher A. Saif
- Department of Mechanical Science and Engineering, University of Illinois Urbana-Champaign, Urbana, IL61801
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4
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Aggarwal A, Liu R, Chen Y, Ralowicz AJ, Bergerson SJ, Tomaska F, Mohar B, Hanson TL, Hasseman JP, Reep D, Tsegaye G, Yao P, Ji X, Kloos M, Walpita D, Patel R, Mohr MA, Tillberg PW, Looger LL, Marvin JS, Hoppa MB, Konnerth A, Kleinfeld D, Schreiter ER, Podgorski K. Glutamate indicators with improved activation kinetics and localization for imaging synaptic transmission. Nat Methods 2023; 20:925-934. [PMID: 37142767 PMCID: PMC10250197 DOI: 10.1038/s41592-023-01863-6] [Citation(s) in RCA: 16] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2022] [Accepted: 03/21/2023] [Indexed: 05/06/2023]
Abstract
The fluorescent glutamate indicator iGluSnFR enables imaging of neurotransmission with genetic and molecular specificity. However, existing iGluSnFR variants exhibit low in vivo signal-to-noise ratios, saturating activation kinetics and exclusion from postsynaptic densities. Using a multiassay screen in bacteria, soluble protein and cultured neurons, we generated variants with improved signal-to-noise ratios and kinetics. We developed surface display constructs that improve iGluSnFR's nanoscopic localization to postsynapses. The resulting indicator iGluSnFR3 exhibits rapid nonsaturating activation kinetics and reports synaptic glutamate release with decreased saturation and increased specificity versus extrasynaptic signals in cultured neurons. Simultaneous imaging and electrophysiology at individual boutons in mouse visual cortex showed that iGluSnFR3 transients report single action potentials with high specificity. In vibrissal sensory cortex layer 4, we used iGluSnFR3 to characterize distinct patterns of touch-evoked feedforward input from thalamocortical boutons and both feedforward and recurrent input onto L4 cortical neuron dendritic spines.
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Affiliation(s)
- Abhi Aggarwal
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, VA, USA
- Allen Institute for Neural Dynamics, Seattle, WA, USA
| | - Rui Liu
- Department of Physics, University of California, San Diego, La Jolla, CA, USA
| | - Yang Chen
- Institute of Neuroscience and Cluster for Systems Neurology (SyNergy), Technical University of Munich (TUM), Munich, Germany
| | - Amelia J Ralowicz
- Department of Biological Sciences, Dartmouth College, Hanover, NH, USA
| | | | - Filip Tomaska
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, VA, USA
- Department of Physiology, Second Faculty of Medicine, Charles University, Prague, Czech Republic
| | - Boaz Mohar
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, VA, USA
| | - Timothy L Hanson
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, VA, USA
| | - Jeremy P Hasseman
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, VA, USA
| | - Daniel Reep
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, VA, USA
| | - Getahun Tsegaye
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, VA, USA
| | - Pantong Yao
- Neurosciences Graduate Program, University of California San Diego, La Jolla, CA, USA
| | - Xiang Ji
- Department of Physics, University of California, San Diego, La Jolla, CA, USA
| | - Marinus Kloos
- Institute of Neuroscience and Cluster for Systems Neurology (SyNergy), Technical University of Munich (TUM), Munich, Germany
| | - Deepika Walpita
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, VA, USA
| | - Ronak Patel
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, VA, USA
| | - Manuel A Mohr
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, VA, USA
- Department of Biosystems Science and Engineering, Swiss Federal Institute of Technology (ETH) Zurich, Basel, Switzerland
| | - Paul W Tillberg
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, VA, USA
| | - Loren L Looger
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, VA, USA
- Howard Hughes Medical Institute, Department of Neurosciences, University of California, San Diego, La Jolla, CA, USA
| | - Jonathan S Marvin
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, VA, USA
| | - Michael B Hoppa
- Department of Biological Sciences, Dartmouth College, Hanover, NH, USA
| | - Arthur Konnerth
- Institute of Neuroscience and Cluster for Systems Neurology (SyNergy), Technical University of Munich (TUM), Munich, Germany
| | - David Kleinfeld
- Department of Physics, University of California, San Diego, La Jolla, CA, USA
- Section of Neurobiology, University of California, San Diego, La Jolla, CA, USA
| | - Eric R Schreiter
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, VA, USA
| | - Kaspar Podgorski
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, VA, USA.
- Allen Institute for Neural Dynamics, Seattle, WA, USA.
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5
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Martínez San Segundo P, Terni B, Llobet A. Multivesicular release favors short term synaptic depression in hippocampal autapses. Front Cell Neurosci 2023; 17:1057242. [PMID: 37265578 PMCID: PMC10230035 DOI: 10.3389/fncel.2023.1057242] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2022] [Accepted: 04/10/2023] [Indexed: 06/03/2023] Open
Abstract
Presynaptic terminals of the central nervous system can support univesicular and multivesicular synchronous release of neurotransmitters, however, the functional implications of the prevalence of one mechanism over the other are yet unresolved. Here, we took advantage of the expression of SF-iGluSnFR.S72A in the astrocytic feeder layer of autaptic hippocampal neuronal cultures to associate the liberation of glutamate to excitatory postsynaptic currents. The presence of the glutamate sensor in glial cells avoided any interference with the function of endogenous postsynaptic receptors. It was possible to optically detect changes in neurotransmitter release probability, which was heterogeneous among synaptic boutons studied. For each neuron investigated, the liberation of neurotransmitters occurred through a predominant mechanism. The prevalence of multivesicular over univesicular release increased synaptic strength and enhanced short-term synaptic depression. These results show that the preference of hippocampal boutons to synchronously release one or more vesicles determines the strength and low pass filtering properties of the synapses established.
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Affiliation(s)
- Pablo Martínez San Segundo
- Laboratory of Neurobiology, Department of Pathology and Experimental Therapy, Institute of Neurosciences, University of Barcelona, Barcelona, Spain
- Bellvitge Biomedical Research Institute (IDIBELL), Barcelona, Spain
| | - Beatrice Terni
- Laboratory of Neurobiology, Department of Pathology and Experimental Therapy, Institute of Neurosciences, University of Barcelona, Barcelona, Spain
- Bellvitge Biomedical Research Institute (IDIBELL), Barcelona, Spain
| | - Artur Llobet
- Laboratory of Neurobiology, Department of Pathology and Experimental Therapy, Institute of Neurosciences, University of Barcelona, Barcelona, Spain
- Bellvitge Biomedical Research Institute (IDIBELL), Barcelona, Spain
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6
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Velasco CD, Santarella-Mellwig R, Schorb M, Gao L, Thorn-Seshold O, Llobet A. Microtubule depolymerization contributes to spontaneous neurotransmitter release in vitro. Commun Biol 2023; 6:488. [PMID: 37147475 PMCID: PMC10163034 DOI: 10.1038/s42003-023-04779-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2022] [Accepted: 03/29/2023] [Indexed: 05/07/2023] Open
Abstract
Microtubules are key to multiple neuronal functions involving the transport of organelles, however, their relationship to neurotransmitter release is still unresolved. Here, we show that microtubules present in the presynaptic compartment of cholinergic autaptic synapses are dynamic. To investigate how the balance between microtubule growth and shrinkage affects neurotransmission we induced synchronous microtubule depolymerization by photoactivation of the chemical inhibitor SBTub3. The consequence was an increase in spontaneous neurotransmitter release. An analogous effect was obtained by dialyzing the cytosol with Kif18A, a plus-end-directed kinesin with microtubule depolymerizing activity. Kif18A also inhibited the refilling of the readily releasable pool of synaptic vesicles during high frequency stimulation. The action of Kif18A was associated to one order of magnitude increases in the numbers of exo-endocytic pits and endosomes present in the presynaptic terminal. An enhancement of spontaneous neurotransmitter release was also observed when neurons were dialyzed with stathmin-1, a protein with a widespread presence in the nervous system that induces microtubule depolymerization. Taken together, these results support that microtubules restrict spontaneous neurotransmitter release as well as promote the replenishment of the readily releasable pool of synaptic vesicles.
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Affiliation(s)
- Cecilia D Velasco
- Laboratory of Neurobiology, Department of Pathology and Experimental Therapy, Institute of Neurosciences, University of Barcelona, 08907, L'Hospitalet de Llobregat, Barcelona, Spain
- Bellvitge Biomedical Research Institute (IDIBELL), 08907, L'Hospitalet de Llobregat, Barcelona, Spain
| | - Rachel Santarella-Mellwig
- Electron Microscopy Core Facility, European Molecular Biology Laboratory (EMBL), Meyerhofstrasse 1, 69117, Heidelberg, Germany
| | - Martin Schorb
- Electron Microscopy Core Facility, European Molecular Biology Laboratory (EMBL), Meyerhofstrasse 1, 69117, Heidelberg, Germany
| | - Li Gao
- Department of Pharmacy, Ludwig-Maximilians University of Munich, Munich, 81377, Germany
| | - Oliver Thorn-Seshold
- Department of Pharmacy, Ludwig-Maximilians University of Munich, Munich, 81377, Germany
| | - Artur Llobet
- Laboratory of Neurobiology, Department of Pathology and Experimental Therapy, Institute of Neurosciences, University of Barcelona, 08907, L'Hospitalet de Llobregat, Barcelona, Spain.
- Bellvitge Biomedical Research Institute (IDIBELL), 08907, L'Hospitalet de Llobregat, Barcelona, Spain.
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7
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Grasskamp AT, Jusyte M, McCarthy AW, Götz TWB, Ditlevsen S, Walter AM. Spontaneous neurotransmission at evocable synapses predicts their responsiveness to action potentials. Front Cell Neurosci 2023; 17:1129417. [PMID: 36970416 PMCID: PMC10030884 DOI: 10.3389/fncel.2023.1129417] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2022] [Accepted: 02/16/2023] [Indexed: 03/29/2023] Open
Abstract
Synaptic transmission relies on presynaptic neurotransmitter (NT) release from synaptic vesicles (SVs) and on NT detection by postsynaptic receptors. Transmission exists in two principal modes: action-potential (AP) evoked and AP-independent, "spontaneous" transmission. AP-evoked neurotransmission is considered the primary mode of inter-neuronal communication, whereas spontaneous transmission is required for neuronal development, homeostasis, and plasticity. While some synapses appear dedicated to spontaneous transmission only, all AP-responsive synapses also engage spontaneously, but whether this encodes functional information regarding their excitability is unknown. Here we report on functional interdependence of both transmission modes at individual synaptic contacts of Drosophila larval neuromuscular junctions (NMJs) which were identified by the presynaptic scaffolding protein Bruchpilot (BRP) and whose activities were quantified using the genetically encoded Ca2+ indicator GCaMP. Consistent with the role of BRP in organizing the AP-dependent release machinery (voltage-dependent Ca2+ channels and SV fusion machinery), most active BRP-positive synapses (>85%) responded to APs. At these synapses, the level of spontaneous activity was a predictor for their responsiveness to AP-stimulation. AP-stimulation resulted in cross-depletion of spontaneous activity and both transmission modes were affected by the non-specific Ca2+ channel blocker cadmium and engaged overlapping postsynaptic receptors. Thus, by using overlapping machinery, spontaneous transmission is a continuous, stimulus independent predictor for the AP-responsiveness of individual synapses.
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Affiliation(s)
| | - Meida Jusyte
- Leibniz-Forschungsinstitut für Molekulare Pharmakologie, Berlin, Germany
- Einstein Center for Neurosciences, Charité–Universitätsmedizin Berlin, Berlin, Germany
| | | | - Torsten W. B. Götz
- Leibniz-Forschungsinstitut für Molekulare Pharmakologie, Berlin, Germany
| | - Susanne Ditlevsen
- Department of Mathematical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Alexander M. Walter
- Leibniz-Forschungsinstitut für Molekulare Pharmakologie, Berlin, Germany
- Einstein Center for Neurosciences, Charité–Universitätsmedizin Berlin, Berlin, Germany
- Department of Neuroscience, University of Copenhagen, Copenhagen, Denmark
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8
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Hao Y, Toulmé E, König B, Rosenmund C, Plested AJR. Targeted sensors for glutamatergic neurotransmission. eLife 2023; 12:84029. [PMID: 36622100 PMCID: PMC9917459 DOI: 10.7554/elife.84029] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2022] [Accepted: 01/06/2023] [Indexed: 01/10/2023] Open
Abstract
Optical report of neurotransmitter release allows visualisation of excitatory synaptic transmission. Sensitive genetically-encoded fluorescent glutamate reporters operating with a range of affinities and emission wavelengths are available. However, without targeting to synapses, the specificity of the fluorescent signal is uncertain, compared to sensors directed at vesicles or other synaptic markers. We fused the state-of-the-art reporter iGluSnFR to glutamate receptor auxiliary proteins in order to target it to postsynaptic sites. Chimeras of Stargazin and gamma-8 that we named SnFR-γ2 and SnFR-γ8, were enriched at synapses, retained function and reported spontaneous glutamate release in rat hippocampal cells, with apparently diffraction-limited spatial precision. In autaptic mouse neurons cultured on astrocytic microislands, evoked neurotransmitter release could be quantitatively detected at tens of synapses in a field of view whilst evoked currents were recorded simultaneously. These experiments revealed a specific postsynaptic deficit from Stargazin overexpression, resulting in synapses with normal neurotransmitter release but without postsynaptic responses. This defect was reverted by delaying overexpression. By working at different calcium concentrations, we determined that SnFR-γ2 is a linear reporter of the global quantal parameters and short-term synaptic plasticity, whereas iGluSnFR is not. On average, half of iGluSnFR regions of interest (ROIs) showing evoked fluorescence changes had intense rundown, whereas less than 5% of SnFR-γ2 ROIs did. We provide an open-source analysis suite for extracting quantal parameters including release probability from fluorescence time series of individual and grouped synaptic responses. Taken together, postsynaptic targeting improves several properties of iGluSnFR and further demonstrates the importance of subcellular targeting for optogenetic actuators and reporters.
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Affiliation(s)
- Yuchen Hao
- Institute of Biology, Cellular Biophysics, Humboldt-Universität zu BerlinBerlinGermany
- Leibniz-Forschungsinstitut für Molekulare PharmakologieBerlinGermany
| | - Estelle Toulmé
- Institute for Neurophysiology, Charité - Universitätsmedizin BerlinBerlinGermany
| | - Benjamin König
- Institute of Biology, Cellular Biophysics, Humboldt-Universität zu BerlinBerlinGermany
- Leibniz-Forschungsinstitut für Molekulare PharmakologieBerlinGermany
| | - Christian Rosenmund
- Institute for Neurophysiology, Charité - Universitätsmedizin BerlinBerlinGermany
- NeuroCure Cluster of ExcellenceBerlinGermany
| | - Andrew JR Plested
- Institute of Biology, Cellular Biophysics, Humboldt-Universität zu BerlinBerlinGermany
- Leibniz-Forschungsinstitut für Molekulare PharmakologieBerlinGermany
- NeuroCure Cluster of ExcellenceBerlinGermany
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9
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Bulumulla C, Krasley AT, Cristofori-Armstrong B, Valinsky WC, Walpita D, Ackerman D, Clapham DE, Beyene AG. Visualizing synaptic dopamine efflux with a 2D composite nanofilm. eLife 2022; 11:78773. [PMID: 35786443 PMCID: PMC9363124 DOI: 10.7554/elife.78773] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2022] [Accepted: 07/01/2022] [Indexed: 11/23/2022] Open
Abstract
Chemical neurotransmission constitutes one of the fundamental modalities of communication between neurons. Monitoring release of these chemicals has traditionally been difficult to carry out at spatial and temporal scales relevant to neuron function. To understand chemical neurotransmission more fully, we need to improve the spatial and temporal resolutions of measurements for neurotransmitter release. To address this, we engineered a chemi-sensitive, two-dimensional composite nanofilm that facilitates visualization of the release and diffusion of the neurochemical dopamine with synaptic resolution, quantal sensitivity, and simultaneously from hundreds of release sites. Using this technology, we were able to monitor the spatiotemporal dynamics of dopamine release in dendritic processes, a poorly understood phenomenon. We found that dopamine release is broadcast from a subset of dendritic processes as hotspots that have a mean spatial spread of ≈ 3.2 µm (full width at half maximum [FWHM]) and are observed with a mean spatial frequency of one hotspot per ≈ 7.5 µm of dendritic length. Major dendrites of dopamine neurons and fine dendritic processes, as well as dendritic arbors and dendrites with no apparent varicose morphology participated in dopamine release. Remarkably, these release hotspots co-localized with Bassoon, suggesting that Bassoon may contribute to organizing active zones in dendrites, similar to its role in axon terminals. To form the vast and complex network necessary for an organism to sense and react to the world, neurons must connect at highly specialized junctions. Individual cells communicate at these ‘synapses’ by releasing chemical signals (or neurotransmitters) such as dopamine, a molecule involved in learning and motivation. Despite the central role that synapses play in the brain, it remains challenging to measure exactly where neurotransmitters are released and how far they travel from their release site. Currently, most tools available to scientists only allow bulk measurements of neurotransmitter release. To tackle this limitation, Bulumulla et al. developed a new way to measure neurotransmitter release from neurons, harnessing a technique which uses fluorescent nanosensors that glow brighter when exposed to dopamine. These sensors form a very thin film upon which neurons can grow; when the cells release dopamine, the sensors ‘light up’ as they encounter the molecule. Dubbed DopaFilm, the technology reveals exactly where the neurotransmitter comes from and how it spreads between cells in real time. In particular, the approach showed that dopamine emerges from 'hot spots' at specific sites in cells; it also helped Bulumulla et al. study how dopamine is released from subcellular compartments that have previously not been well characterized. Improving the sensors so that the film could detect other neurotransmitters besides dopamine would broaden the use of this approach. In the future, combining this technology with other types of imaging should enable studies of individual synapses with intricate detail.
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10
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Mendonça PRF, Tagliatti E, Langley H, Kotzadimitriou D, Zamora-Chimal CG, Timofeeva Y, Volynski KE. Asynchronous glutamate release is enhanced in low release efficacy synapses and dispersed across the active zone. Nat Commun 2022; 13:3497. [PMID: 35715404 PMCID: PMC9206079 DOI: 10.1038/s41467-022-31070-4] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2021] [Accepted: 05/31/2022] [Indexed: 11/09/2022] Open
Abstract
The balance between fast synchronous and delayed asynchronous release of neurotransmitters has a major role in defining computational properties of neuronal synapses and regulation of neuronal network activity. However, how it is tuned at the single synapse level remains poorly understood. Here, using the fluorescent glutamate sensor SF-iGluSnFR, we image quantal vesicular release in tens to hundreds of individual synaptic outputs from single pyramidal cells with 4 millisecond temporal and 75 nm spatial resolution. We find that the ratio between synchronous and asynchronous synaptic vesicle exocytosis varies extensively among synapses supplied by the same axon, and that the synchronicity of release is reduced at low release probability synapses. We further demonstrate that asynchronous exocytosis sites are more widely distributed within the release area than synchronous sites. Together, our results reveal a universal relationship between the two major functional properties of synapses - the timing and the overall efficacy of neurotransmitter release.
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Affiliation(s)
- Philipe R F Mendonça
- University College London Institute of Neurology, London, UK. .,Department of Physiology and Biophysics, Federal University of Minas Gerais, Gerais, Brazil.
| | - Erica Tagliatti
- University College London Institute of Neurology, London, UK
| | - Helen Langley
- University College London Institute of Neurology, London, UK
| | | | | | - Yulia Timofeeva
- University College London Institute of Neurology, London, UK. .,Department of Computer Science, University of Warwick, Coventry, UK.
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11
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α-Synuclein induced cholesterol lowering increases tonic and reduces depolarization-evoked synaptic vesicle recycling and glutamate release. NPJ Parkinsons Dis 2022; 8:71. [PMID: 35672421 PMCID: PMC9174203 DOI: 10.1038/s41531-022-00334-7] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2021] [Accepted: 05/17/2022] [Indexed: 02/07/2023] Open
Abstract
α-Synuclein (α-syn) is a key molecule linked to Parkinson's disease pathology. Physiologically, the monomeric α-syn in the presynaptic termini is involved in regulation of neurotransmission, but the pathophysiology of extracellular monomeric α-syn is still unknown. Utilizing both in vivo and in vitro approaches, we investigated how extracellular α-syn impact presynaptic structure and function. Our data revealed that treatment with exogenous α-syn leads to increased tonic and decreased depolarization-evoked synaptic vesicle (SV) recycling and glutamate release. This was associated with mobilization of molecularly distinct SV pools and reorganization of active zone components. Our study also showed that exogenous α-syn impaired neuronal cholesterol level and that the cholesterol binding domain of α-syn was sufficient to exert the same presynaptic phenotype as the full-length protein. The present study sheds new light on physiological functions of extracellular α-syn in overall maintenance of presynaptic activity that involves the reorganization of both presynaptic compartment and cholesterol-rich plasma membrane domains.
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Tjahjono N, Jin Y, Hsu A, Roukes M, Tian L. Letting the little light of mind shine: Advances and future directions in neurochemical detection. Neurosci Res 2022; 179:65-78. [PMID: 34861294 PMCID: PMC9508992 DOI: 10.1016/j.neures.2021.11.012] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2021] [Accepted: 11/29/2021] [Indexed: 12/12/2022]
Abstract
Synaptic transmission via neurochemical release is the fundamental process that integrates and relays encoded information in the brain to regulate physiological function, cognition, and emotion. To unravel the biochemical, biophysical, and computational mechanisms of signal processing, one needs to precisely measure the neurochemical release dynamics with molecular and cell-type specificity and high resolution. Here we reviewed the development of analytical, electrochemical, and fluorescence imaging approaches to detect neurotransmitter and neuromodulator release. We discussed the advantages and practicality in implementation of each technology for ease-of-use, flexibility for multimodal studies, and challenges for future optimization. We hope this review will provide a versatile guide for tool engineering and applications for recording neurochemical release.
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Affiliation(s)
- Nikki Tjahjono
- Biomedical Engineering Graduate Group, University of California, Davis, Davis, CA, 95616, USA
| | - Yihan Jin
- Neuroscience Graduate Group, University of California, Davis, Davis, CA, 95618, USA
| | - Alice Hsu
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA, 91125, USA
| | - Michael Roukes
- Department of Physics, California Institute of Technology, Pasadena, CA, 91125, USA
| | - Lin Tian
- Department of Biochemistry and Molecular Medicine, School of Medicine, University of California, Davis, Davis, CA, 95616, USA.
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Wang CS, Chanaday NL, Monteggia LM, Kavalali ET. Probing the segregation of evoked and spontaneous neurotransmission via photobleaching and recovery of a fluorescent glutamate sensor. eLife 2022; 11:e76008. [PMID: 35420542 PMCID: PMC9129874 DOI: 10.7554/elife.76008] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2021] [Accepted: 04/08/2022] [Indexed: 11/13/2022] Open
Abstract
Synapses maintain both action potential-evoked and spontaneous neurotransmitter release; however, organization of these two forms of release within an individual synapse remains unclear. Here, we used photobleaching properties of iGluSnFR, a fluorescent probe that detects glutamate, to investigate the subsynaptic organization of evoked and spontaneous release in primary hippocampal cultures. In nonneuronal cells and neuronal dendrites, iGluSnFR fluorescence is intensely photobleached and recovers via diffusion of nonphotobleached probes with a time constant of ~10 s. After photobleaching, while evoked iGluSnFR events could be rapidly suppressed, their recovery required several hours. In contrast, iGluSnFR responses to spontaneous release were comparatively resilient to photobleaching, unless the complete pool of iGluSnFR was activated by glutamate perfusion. This differential effect of photobleaching on different modes of neurotransmission is consistent with a subsynaptic organization where sites of evoked glutamate release are clustered and corresponding iGluSnFR probes are diffusion restricted, while spontaneous release sites are broadly spread across a synapse with readily diffusible iGluSnFR probes.
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Affiliation(s)
- Camille S Wang
- Vanderbilt Brain Institute, Vanderbilt UniversityNashvilleUnited States
| | - Natali L Chanaday
- Department of Pharmacology, Vanderbilt UniversityNashvilleUnited States
| | - Lisa M Monteggia
- Vanderbilt Brain Institute, Vanderbilt UniversityNashvilleUnited States
- Department of Pharmacology, Vanderbilt UniversityNashvilleUnited States
| | - Ege T Kavalali
- Vanderbilt Brain Institute, Vanderbilt UniversityNashvilleUnited States
- Department of Pharmacology, Vanderbilt UniversityNashvilleUnited States
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14
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Van Dyck M, Mishra RK, Pestana F, Verstraelen P, Lavreysen H, Pita-Almenar JD, Kashikar ND, De Vos WH. High-throughput Analysis of Synaptic Activity in Electrically Stimulated Neuronal Cultures. Neuroinformatics 2021; 19:737-750. [PMID: 34374965 DOI: 10.1007/s12021-021-09536-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/10/2021] [Indexed: 10/20/2022]
Abstract
Synaptic dysfunction is a hallmark of various neurodegenerative and neurodevelopmental disorders. To interrogate synapse function in a systematic manner, we have established an automated high-throughput imaging pipeline based on fluorescence microscopy acquisition and image analysis of electrically stimulated synaptic transmission in neuronal cultures. Identification and measurement of synaptic signal fluctuations is achieved by means of an image analysis algorithm based on singular value decomposition. By exploiting the synchronicity of the evoked responses, the algorithm allows disentangling distinct temporally correlated patterns of firing synapse populations or cell types that are present in the same recording. We demonstrate the performance of the analysis with a pilot compound screen and show that the multiparametric readout allows classifying treatments by their spatiotemporal fingerprint. The image analysis and visualization software has been made publicly available on Github ( https://www.github.com/S3Toolbox ). The streamlined automation of multi-well image acquisition, electrical stimulation, analysis, and meta-data warehousing facilitates large-scale synapse-oriented screens and, in doing so, it will accelerate the drug discovery process.
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Affiliation(s)
- Michiel Van Dyck
- Laboratory of Cell Biology and Histology, University of Antwerp, CDE, Antwerp, Belgium.,Janssen Research and Development, Neuroscience Therapeutic Area, Beerse, Belgium
| | - Rajiv K Mishra
- iOligos Technologies Private Limited, 1703, CB2, Supertech Capetown, Sector-74, 201301, Noida, India
| | - Francisco Pestana
- Janssen Research and Development, Neuroscience Therapeutic Area, Beerse, Belgium
| | - Peter Verstraelen
- Laboratory of Cell Biology and Histology, University of Antwerp, CDE, Antwerp, Belgium
| | - Hilde Lavreysen
- Janssen Research and Development, Neuroscience Therapeutic Area, Beerse, Belgium
| | - Juan D Pita-Almenar
- Janssen Research and Development, Neuroscience Therapeutic Area, Beerse, Belgium
| | - Nachiket D Kashikar
- Resolve BioSciences GmbH, Creative Campus Monheim Gebäude A03, Alfred-Nobel-Strasse 10, 40789, Monheim am Rhein, Germany.
| | - Winnok H De Vos
- Laboratory of Cell Biology and Histology, University of Antwerp, CDE, Antwerp, Belgium.
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