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Chen X, Shen Y, Song Z, Wang X, Yao H, Cai Y, Zhao ZA, Hu B. microRNA-2184 orchestrates Mauthner-cell axon regeneration in zebrafish via syt3 modulation. J Genet Genomics 2024:S1673-8527(24)00069-9. [PMID: 38582297 DOI: 10.1016/j.jgg.2024.03.016] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2024] [Revised: 03/30/2024] [Accepted: 03/30/2024] [Indexed: 04/08/2024]
Abstract
MicroRNAs (miRNAs) play a significant role in axon regeneration following spinal cord injury. However, the functions of numerous miRNAs in axon regeneration within the central nervous system (CNS) remain largely unexplored. Here, we elucidate the positive role of miR-2184 in axon regeneration within zebrafish Mauthner cells (M-cells). The upregulation of miR-2184 in the single M-cells facilitates axon regeneration, while the specific sponge-induced silencing of miR-2184 leads to impeded axon regeneration. We show that syt3, a downstream target of miR-2184, negatively regulates axon regeneration, and the regeneration suppression by syt3 depends on its binding to Ca2+. Furthermore, pharmacological stimulation of the cAMP/PKA pathway suggests that changes in the readily releasable pool may affect axon regeneration. Our data indicate that miR-2184 promotes axon regeneration of M-cells within the CNS by modulating the downstream target syt3, providing valuable insights into potential therapeutic strategies.
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Affiliation(s)
- Xinghan Chen
- Hefei National Research Center for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei, Anhui 230026, China
| | - Yueru Shen
- Hefei National Research Center for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei, Anhui 230026, China
| | - Zheng Song
- Hefei National Research Center for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei, Anhui 230026, China
| | - Xinliang Wang
- Hefei National Research Center for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei, Anhui 230026, China
| | - Huaitong Yao
- Hefei National Research Center for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei, Anhui 230026, China
| | - Yuan Cai
- The First Affiliated Hospital of USTC, Division of Life Sciences and Medicine, University of Science and Technology of China, Hefei, Anhui 230026, China
| | - Zi-Ang Zhao
- Hefei National Research Center for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei, Anhui 230026, China
| | - Bing Hu
- Hefei National Research Center for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei, Anhui 230026, China; Center for Advanced Interdisciplinary Science and Biomedicine of IHM, Division of Life Sciences and Medicine, University of Science and Technology of China, Hefei, Anhui 230026, China.
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2
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Silva M, Tran V, Marty A. A maximum of two readily releasable vesicles per docking site at a cerebellar single active zone synapse. eLife 2024; 12:RP91087. [PMID: 38180320 PMCID: PMC10963025 DOI: 10.7554/elife.91087] [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] [Indexed: 01/06/2024] Open
Abstract
Recent research suggests that in central mammalian synapses, active zones contain several docking sites acting in parallel. Before release, one or several synaptic vesicles (SVs) are thought to bind to each docking site, forming the readily releasable pool (RRP). Determining the RRP size per docking site has important implications for short-term synaptic plasticity. Here, using mouse cerebellar slices, we take advantage of recently developed methods to count the number of released SVs at single glutamatergic synapses in response to trains of action potentials (APs). In each recording, the number of docking sites was determined by fitting with a binomial model the number of released SVs in response to individual APs. After normalization with respect to the number of docking sites, the summed number of released SVs following a train of APs was used to estimate of the RRP size per docking site. To improve this estimate, various steps were taken to maximize the release probability of docked SVs, the occupancy of docking sites, as well as the extent of synaptic depression. Under these conditions, the RRP size reached a maximum value close to two SVs per docking site. The results indicate that each docking site contains two distinct SV-binding sites that can simultaneously accommodate up to one SV each. They further suggest that under special experimental conditions, as both sites are close to full occupancy, a maximal RRP size of two SVs per docking site can be reached. More generally, the results validate a sequential two-step docking model previously proposed at this preparation.
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Affiliation(s)
- Melissa Silva
- Université Paris Cité, SPPIN-Saints Pères Paris Institute for the Neurosciences, CNRSParisFrance
| | - Van Tran
- Université Paris Cité, SPPIN-Saints Pères Paris Institute for the Neurosciences, CNRSParisFrance
| | - Alain Marty
- Université Paris Cité, SPPIN-Saints Pères Paris Institute for the Neurosciences, CNRSParisFrance
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3
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Mukhamedyarov MA, Khabibrakhmanov AN, Khuzakhmetova VF, Giniatullin AR, Zakirjanova GF, Zhilyakov NV, Mukhutdinova KA, Samigullin DV, Grigoryev PN, Zakharov AV, Zefirov AL, Petrov AM. Early Alterations in Structural and Functional Properties in the Neuromuscular Junctions of Mutant FUS Mice. Int J Mol Sci 2023; 24:9022. [PMID: 37240370 PMCID: PMC10218837 DOI: 10.3390/ijms24109022] [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: 04/04/2023] [Revised: 05/16/2023] [Accepted: 05/18/2023] [Indexed: 05/28/2023] Open
Abstract
Amyotrophic lateral sclerosis (ALS) is manifested as skeletal muscle denervation, loss of motor neurons and finally severe respiratory failure. Mutations of RNA-binding protein FUS are one of the common genetic reasons of ALS accompanied by a 'dying back' type of degeneration. Using fluorescent approaches and microelectrode recordings, the early structural and functional alterations in diaphragm neuromuscular junctions (NMJs) were studied in mutant FUS mice at the pre-onset stage. Lipid peroxidation and decreased staining with a lipid raft marker were found in the mutant mice. Despite the preservation of the end-plate structure, immunolabeling revealed an increase in levels of presynaptic proteins, SNAP-25 and synapsin 1. The latter can restrain Ca2+-dependent synaptic vesicle mobilization. Indeed, neurotransmitter release upon intense nerve stimulation and its recovery after tetanus and compensatory synaptic vesicle endocytosis were markedly depressed in FUS mice. There was a trend to attenuation of axonal [Ca2+]in increase upon nerve stimulation at 20 Hz. However, no changes in neurotransmitter release and the intraterminal Ca2+ transient in response to low frequency stimulation or in quantal content and the synchrony of neurotransmitter release at low levels of external Ca2+ were detected. At a later stage, shrinking and fragmentation of end plates together with a decrease in presynaptic protein expression and disturbance of the neurotransmitter release timing occurred. Overall, suppression of synaptic vesicle exo-endocytosis upon intense activity probably due to alterations in membrane properties, synapsin 1 levels and Ca2+ kinetics could be an early sign of nascent NMJ pathology, which leads to neuromuscular contact disorganization.
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Affiliation(s)
- Marat A. Mukhamedyarov
- Department of Normal Physiology, Kazan State Medial University, 49 Butlerova St., Kazan 420012, Russia; (M.A.M.)
| | - Aydar N. Khabibrakhmanov
- Department of Normal Physiology, Kazan State Medial University, 49 Butlerova St., Kazan 420012, Russia; (M.A.M.)
| | - Venera F. Khuzakhmetova
- Kazan Institute of Biochemistry and Biophysics, Federal Research Center ‘‘Kazan Scientific Center of RAS”, 2/31 Lobachevsky St., P.O. Box 30, Kazan 420111, Russia (N.V.Z.)
| | - Arthur R. Giniatullin
- Department of Normal Physiology, Kazan State Medial University, 49 Butlerova St., Kazan 420012, Russia; (M.A.M.)
- Kazan Institute of Biochemistry and Biophysics, Federal Research Center ‘‘Kazan Scientific Center of RAS”, 2/31 Lobachevsky St., P.O. Box 30, Kazan 420111, Russia (N.V.Z.)
| | - Guzalia F. Zakirjanova
- Department of Normal Physiology, Kazan State Medial University, 49 Butlerova St., Kazan 420012, Russia; (M.A.M.)
- Kazan Institute of Biochemistry and Biophysics, Federal Research Center ‘‘Kazan Scientific Center of RAS”, 2/31 Lobachevsky St., P.O. Box 30, Kazan 420111, Russia (N.V.Z.)
| | - Nikita V. Zhilyakov
- Kazan Institute of Biochemistry and Biophysics, Federal Research Center ‘‘Kazan Scientific Center of RAS”, 2/31 Lobachevsky St., P.O. Box 30, Kazan 420111, Russia (N.V.Z.)
| | - Kamilla A. Mukhutdinova
- Department of Normal Physiology, Kazan State Medial University, 49 Butlerova St., Kazan 420012, Russia; (M.A.M.)
| | - Dmitry V. Samigullin
- Kazan Institute of Biochemistry and Biophysics, Federal Research Center ‘‘Kazan Scientific Center of RAS”, 2/31 Lobachevsky St., P.O. Box 30, Kazan 420111, Russia (N.V.Z.)
- Department of Radiophotonics and Microwave Technologies, Kazan National Research Technical University, 10 K. Marx St., Kazan 420111, Russia
| | - Pavel N. Grigoryev
- Department of Normal Physiology, Kazan State Medial University, 49 Butlerova St., Kazan 420012, Russia; (M.A.M.)
| | - Andrey V. Zakharov
- Department of Normal Physiology, Kazan State Medial University, 49 Butlerova St., Kazan 420012, Russia; (M.A.M.)
- Laboratory of Neurobiology, Kazan Federal University, Kazan 420008, Russia
| | - Andrey L. Zefirov
- Department of Normal Physiology, Kazan State Medial University, 49 Butlerova St., Kazan 420012, Russia; (M.A.M.)
| | - Alexey M. Petrov
- Department of Normal Physiology, Kazan State Medial University, 49 Butlerova St., Kazan 420012, Russia; (M.A.M.)
- Kazan Institute of Biochemistry and Biophysics, Federal Research Center ‘‘Kazan Scientific Center of RAS”, 2/31 Lobachevsky St., P.O. Box 30, Kazan 420111, Russia (N.V.Z.)
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Singh M, Sapkota K, Sakimura K, Kano M, Cowell RM, Overstreet-Wadiche L, Hablitz JJ, Nakazawa K. Maturation of GABAergic Synaptic Transmission From Neocortical Parvalbumin Interneurons Involves N-methyl-D-aspartate Receptor Recruitment of Cav2.1 Channels. Neuroscience 2023; 513:38-53. [PMID: 36682446 DOI: 10.1016/j.neuroscience.2023.01.007] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2022] [Revised: 01/02/2023] [Accepted: 01/08/2023] [Indexed: 01/21/2023]
Abstract
N-methyl-D-aspartate receptor (NMDAR) hypofunction during brain development is likely to contribute to the manifestation of schizophrenia (SCZ) in young adulthood. The cellular targets of NMDAR hypofunction appear to be at least in part corticolimbic fast-spiking (FS) interneurons. However, functional alterations in parvalbumin (PV)-positive FS interneurons following NMDAR hypofunction are poorly understood. Paired patch-clamp recordings from murine cortical PV interneurons and pyramidal neurons revealed that genetic deletion of NMDAR subunit Grin1 in prospective PV interneurons before the second postnatal week impaired evoked- and synchronized-GABA release. Whereas intrinsic excitability and spiking characteristics were also disturbed by Grin1 deletion, neither restoring their excitability by K+ channel blockade nor increasing extracellular Ca2+ rescued the GABA release. GABA release was also insensitive to the Cav2.1 channel antagonist ω-agatoxin IVA. Heterozygous deletion of Cacna1a gene (encoding Cav2.1) in PV interneurons produced a similar GABA release phenotype as the Grin1 mutants. Treatment with the Cav2.1/2.2 channel agonist GV-58 augmented somatic Ca2+ currents and GABA release in Cacna1a-haploinsufficient PV interneurons, but failed to enhance GABA release in the Grin1-deleted PV interneurons. Taken together, our results suggest that Grin1 deletion in prospective PV interneurons impairs proper maturation of membrane excitability and Cav2.1-recruited evoked GABA release. This may increase synaptic excitatory/inhibitory ratio in principal neurons, contributing to the emergence of SCZ-like phenotypes.
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Affiliation(s)
- Mahendra Singh
- Department of Neuroscience, Scientific Platforms, Southern Research, Birmingham, AL 35205, USA; Department of Neurobiology, University of Alabama at Birmingham, Birmingham, AL 35294, USA.
| | - Kiran Sapkota
- Department of Neuroscience, Scientific Platforms, Southern Research, Birmingham, AL 35205, USA
| | - Kenji Sakimura
- Department of Animal Model Development, Brain Research Institute, Niigata University, Niigata 951-8585, Japan
| | - Masanobu Kano
- Department of Neurophysiology, Graduate School of Medicine, The University of Tokyo, Tokyo 113-0033, Japan; International Research Center for Neurointelligence (WPI-IRCN), The University of Tokyo Institutes for Advanced Study (UTIAS), The University of Tokyo, Tokyo 113-0033, Japan
| | - Rita M Cowell
- Department of Neuroscience, Scientific Platforms, Southern Research, Birmingham, AL 35205, USA; Department of Psychiatry and Behavioral Neurobiology, University of Alabama at Birmingham, Birmingham, AL 35294, USA; Department of Neurology, University of Alabama at Birmingham, Birmingham, AL 35294, USA
| | | | - John J Hablitz
- Department of Neurobiology, University of Alabama at Birmingham, Birmingham, AL 35294, USA
| | - Kazu Nakazawa
- Department of Neuroscience, Scientific Platforms, Southern Research, Birmingham, AL 35205, USA; Department of Neurobiology, University of Alabama at Birmingham, Birmingham, AL 35294, USA; Department of Psychiatry and Behavioral Neurobiology, University of Alabama at Birmingham, Birmingham, AL 35294, USA
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5
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Myeong J, Klyachko VA. Rapid astrocyte-dependent facilitation amplifies multi-vesicular release in hippocampal synapses. Cell Rep 2022; 41:111820. [PMID: 36516768 PMCID: PMC9805313 DOI: 10.1016/j.celrep.2022.111820] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2022] [Revised: 09/30/2022] [Accepted: 11/21/2022] [Indexed: 12/15/2022] Open
Abstract
Synaptic facilitation is a major form of short-term plasticity typically driven by an increase in residual presynaptic calcium. Using near-total internal reflection fluorescence (near-TIRF) imaging of single vesicle release in cultured hippocampal synapses, we demonstrate a distinctive, release-dependent form of facilitation in which probability of vesicle release is higher following a successful glutamate release event than following a failure. This phenomenon has an onset of ≤500 ms and lasts several seconds, resulting in clusters of successful release events. The release-dependent facilitation requires neuronal contact with astrocytes and astrocytic glutamate uptake by EAAT1. It is not observed in neurons grown alone or in the presence of astrocyte-conditioned media. This form of facilitation dynamically amplifies multi-vesicular release. Facilitation-evoked release events exhibit spatial clustering and have a preferential localization toward the active zone center. These results uncover a rapid astrocyte-dependent form of facilitation acting via modulation of multi-vesicular release and displaying distinctive spatiotemporal properties.
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Affiliation(s)
- Jongyun Myeong
- Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, MO 63132, USA
| | - Vitaly A. Klyachko
- Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, MO 63132, USA,Lead contact,Correspondence:
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6
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Yan P, Liu H, Zhou T, Sun P, Wang Y, Wang X, Zhang L, Wang T, Dong J, Zhu J, Lv L, Li W, Qi S, Liang Y, Kong E. Crosstalk of Synapsin1 palmitoylation and phosphorylation controls the dynamicity of synaptic vesicles in neurons. Cell Death Dis 2022; 13:786. [PMID: 36097267 PMCID: PMC9468182 DOI: 10.1038/s41419-022-05235-4] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2022] [Revised: 08/30/2022] [Accepted: 09/05/2022] [Indexed: 01/21/2023]
Abstract
The dynamics of synaptic vesicles (SVs) within presynaptic domains are tightly controlled by synapsin1 phosphorylation; however, the mechanism underlying the anchoring of synapsin1 with F-actin or SVs is not yet fully understood. Here, we found that Syn1 is modified with protein palmitoylation, and examining the roles of Syn1 palmitoylation in neurons led us to uncover that Syn1 palmitoylation is negatively regulated by its phosphorylation; together, they manipulate the clustering and redistribution of SVs. Using the combined approaches of electron microscopy and genetics, we revealed that Syn1 palmitoylation is vital for its binding with F-actin but not SVs. Inhibition of Syn1 palmitoylation causes defects in SVs clustering and a reduced number of total SVs in vivo. We propose a model in which SVs redistribution is triggered by upregulated Syn1 phosphorylation and downregulated Syn1 palmitoylation, and they reversibly promote SVs clustering. The crosstalk of Syn1 palmitoylation and phosphorylation thereby bidirectionally manipulates SVs dynamics in neurons.
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Affiliation(s)
- Peipei Yan
- grid.412990.70000 0004 1808 322XThe Second Affiliated Hospital of Xinxiang Medical University, Xinxiang, China ,grid.412990.70000 0004 1808 322XInstitute of Psychiatry and Neuroscience, Xinxiang key laboratory of protein palmitoylation and major human diseases, Xinxiang Medical University, Xinxiang, China
| | - Huicong Liu
- grid.412990.70000 0004 1808 322XThe Second Affiliated Hospital of Xinxiang Medical University, Xinxiang, China ,grid.412990.70000 0004 1808 322XInstitute of Psychiatry and Neuroscience, Xinxiang key laboratory of protein palmitoylation and major human diseases, Xinxiang Medical University, Xinxiang, China
| | - Tao Zhou
- grid.412990.70000 0004 1808 322XInstitute of Psychiatry and Neuroscience, Xinxiang key laboratory of protein palmitoylation and major human diseases, Xinxiang Medical University, Xinxiang, China
| | - Pu Sun
- grid.412990.70000 0004 1808 322XInstitute of Psychiatry and Neuroscience, Xinxiang key laboratory of protein palmitoylation and major human diseases, Xinxiang Medical University, Xinxiang, China
| | - Yilin Wang
- grid.412990.70000 0004 1808 322XInstitute of Psychiatry and Neuroscience, Xinxiang key laboratory of protein palmitoylation and major human diseases, Xinxiang Medical University, Xinxiang, China
| | - Xibin Wang
- grid.412990.70000 0004 1808 322XInstitute of Psychiatry and Neuroscience, Xinxiang key laboratory of protein palmitoylation and major human diseases, Xinxiang Medical University, Xinxiang, China
| | - Lin Zhang
- grid.412990.70000 0004 1808 322XInstitute of Psychiatry and Neuroscience, Xinxiang key laboratory of protein palmitoylation and major human diseases, Xinxiang Medical University, Xinxiang, China
| | - Tian Wang
- grid.412990.70000 0004 1808 322XInstitute of Psychiatry and Neuroscience, Xinxiang key laboratory of protein palmitoylation and major human diseases, Xinxiang Medical University, Xinxiang, China
| | - Jing Dong
- grid.412990.70000 0004 1808 322XInstitute of Psychiatry and Neuroscience, Xinxiang key laboratory of protein palmitoylation and major human diseases, Xinxiang Medical University, Xinxiang, China
| | - Jiangli Zhu
- grid.13291.380000 0001 0807 1581Department of Urology, State Key Laboratory of Biotherapy and Cancer Center, West China Hospital, Sichuan University and National Collaborative Innovation Center, 610041 Chengdu, China
| | - Luxian Lv
- grid.412990.70000 0004 1808 322XThe Second Affiliated Hospital of Xinxiang Medical University, Xinxiang, China
| | - Wenqiang Li
- grid.412990.70000 0004 1808 322XThe Second Affiliated Hospital of Xinxiang Medical University, Xinxiang, China
| | - Shiqian Qi
- grid.13291.380000 0001 0807 1581Department of Urology, State Key Laboratory of Biotherapy and Cancer Center, West China Hospital, Sichuan University and National Collaborative Innovation Center, 610041 Chengdu, China
| | - Yinming Liang
- grid.412990.70000 0004 1808 322XLaboratory of Genetic Regulators in the Immune System, Henan Key Laboratory of Immunology and Targeted Therapy, School of Laboratory Medicine, Xinxiang Medical University, Xinxiang, China
| | - Eryan Kong
- grid.412990.70000 0004 1808 322XThe Second Affiliated Hospital of Xinxiang Medical University, Xinxiang, China ,grid.412990.70000 0004 1808 322XInstitute of Psychiatry and Neuroscience, Xinxiang key laboratory of protein palmitoylation and major human diseases, Xinxiang Medical University, Xinxiang, China
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7
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Li A, Zhang S, Loconte V, Liu Y, Ekman A, Thompson GJ, Sali A, Stevens RC, White K, Singla J, Sun L. An intensity-based post-processing tool for 3D instance segmentation of organelles in soft X-ray tomograms. PLoS One 2022; 17:e0269887. [PMID: 36048824 PMCID: PMC9436087 DOI: 10.1371/journal.pone.0269887] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2022] [Accepted: 05/29/2022] [Indexed: 11/29/2022] Open
Abstract
Investigating the 3D structures and rearrangements of organelles within a single cell is critical for better characterizing cellular function. Imaging approaches such as soft X-ray tomography have been widely applied to reveal a complex subcellular organization involving multiple inter-organelle interactions. However, 3D segmentation of organelle instances has been challenging despite its importance in organelle characterization. Here we propose an intensity-based post-processing tool to identify and separate organelle instances. Our tool separates sphere-like (insulin vesicle) and columnar-shaped organelle instances (mitochondrion) based on the intensity of raw tomograms, semantic segmentation masks, and organelle morphology. We validate our tool using synthetic tomograms of organelles and experimental tomograms of pancreatic β-cells to separate insulin vesicle and mitochondria instances. As compared to the commonly used connected regions labeling, watershed, and watershed + Gaussian filter methods, our tool results in improved accuracy in identifying organelles in the synthetic tomograms and an improved description of organelle structures in β-cell tomograms. In addition, under different experimental treatment conditions, significant changes in volumes and intensities of both insulin vesicle and mitochondrion are observed in our instance results, revealing their potential roles in maintaining normal β-cell function. Our tool is expected to be applicable for improving the instance segmentation of other images obtained from different cell types using multiple imaging modalities.
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Affiliation(s)
- Angdi Li
- iHuman Institute, ShanghaiTech University, Shanghai, China
- School of Life Science and Technology, ShanghaiTech University, Shanghai, China
- University of Chinese Academy of Sciences, Beijing, China
| | - Shuning Zhang
- iHuman Institute, ShanghaiTech University, Shanghai, China
- School of Life Science and Technology, ShanghaiTech University, Shanghai, China
- University of Chinese Academy of Sciences, Beijing, China
| | - Valentina Loconte
- iHuman Institute, ShanghaiTech University, Shanghai, China
- School of Life Science and Technology, ShanghaiTech University, Shanghai, China
| | - Yan Liu
- iHuman Institute, ShanghaiTech University, Shanghai, China
- School of Life Science and Technology, ShanghaiTech University, Shanghai, China
| | - Axel Ekman
- Department of Anatomy, University of California San Francisco, San Francisco, CA, United States of America
- Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, CA, United States of America
| | | | - Andrej Sali
- California Institute for Quantitative Biosciences, Department of Bioengineering and Therapeutic Sciences, Department of Pharmaceutical Chemistry, University of California, San Francisco, San Francisco, CA, United States of America
| | - Raymond C. Stevens
- iHuman Institute, ShanghaiTech University, Shanghai, China
- School of Life Science and Technology, ShanghaiTech University, Shanghai, China
- Department of Biological Sciences, Bridge Institute, University of Southern California, Los Angeles, CA, United States of America
- Department of Chemistry, Bridge Institute, University of Southern California, Los Angeles, CA, United States of America
| | - Kate White
- Department of Chemistry, Bridge Institute, University of Southern California, Los Angeles, CA, United States of America
- * E-mail: (KW); (JS); (LS)
| | - Jitin Singla
- Department of Biosciences and Bioengineering, Indian Institute of Technology Roorkee, Roorkee, Uttarakhand, India
- * E-mail: (KW); (JS); (LS)
| | - Liping Sun
- iHuman Institute, ShanghaiTech University, Shanghai, China
- School of Life Science and Technology, ShanghaiTech University, Shanghai, China
- * E-mail: (KW); (JS); (LS)
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8
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Montenegro‐Venegas C, Guhathakurta D, Pina‐Fernandez E, Andres‐Alonso M, Plattner F, Gundelfinger ED, Fejtova A. Bassoon controls synaptic vesicle release via regulation of presynaptic phosphorylation and
cAMP. EMBO Rep 2022; 23:e53659. [PMID: 35766170 PMCID: PMC9346490 DOI: 10.15252/embr.202153659] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2021] [Revised: 05/23/2022] [Accepted: 06/01/2022] [Indexed: 11/11/2022] Open
Abstract
Neuronal presynaptic terminals contain hundreds of neurotransmitter‐filled synaptic vesicles (SVs). The morphologically uniform SVs differ in their release competence segregating into functional pools that differentially contribute to neurotransmission. The presynaptic scaffold bassoon is required for neurotransmission, but the underlying molecular mechanisms are unknown. We report that glutamatergic synapses lacking bassoon feature decreased SV release competence and increased resting pool of SVs as assessed by imaging of SV release in cultured neurons. CDK5/calcineurin and cAMP/PKA presynaptic signalling are dysregulated, resulting in an aberrant phosphorylation of their downstream effectors synapsin1 and SNAP25, well‐known regulators of SV release competence. An acute pharmacological restoration of physiological CDK5 and cAMP/PKA activity fully normalises the SV pools in neurons lacking bassoon. Finally, we demonstrate that CDK5‐dependent regulation of PDE4 activity interacts with cAMP/PKA signalling and thereby controls SV release competence. These data reveal that bassoon organises SV pools in glutamatergic synapses via regulation of presynaptic phosphorylation and cAMP homeostasis and indicate a role of CDK5/PDE4/cAMP axis in the control of neurotransmitter release.
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Affiliation(s)
- Carolina Montenegro‐Venegas
- Department of Neurochemistry and Molecular Biology Leibniz Institute for Neurobiology Magdeburg Germany
- Center for Behavioral Brain Sciences (CBBS) Magdeburg Germany
- Institute for Pharmacology and Toxicology, Medical Faculty Otto von Guericke University Magdeburg Germany
| | - Debarpan Guhathakurta
- Molecular Psychiatry, Department of Psychiatry and Psychotherapy Universitätsklinikum Erlangen, Friedrich‐Alexander‐Universität Erlangen‐Nürnberg Erlangen Germany
| | | | - Maria Andres‐Alonso
- RG Presynaptic Plasticity Leibniz Institute for Neurobiology Magdeburg Germany
| | | | - Eckart D Gundelfinger
- Department of Neurochemistry and Molecular Biology Leibniz Institute for Neurobiology Magdeburg Germany
- Center for Behavioral Brain Sciences (CBBS) Magdeburg Germany
- Institute for Pharmacology and Toxicology, Medical Faculty Otto von Guericke University Magdeburg Germany
| | - Anna Fejtova
- Department of Neurochemistry and Molecular Biology Leibniz Institute for Neurobiology Magdeburg Germany
- Molecular Psychiatry, Department of Psychiatry and Psychotherapy Universitätsklinikum Erlangen, Friedrich‐Alexander‐Universität Erlangen‐Nürnberg Erlangen Germany
- RG Presynaptic Plasticity Leibniz Institute for Neurobiology Magdeburg Germany
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9
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Kaplanian A, Vinos M, Skaliora I. GABAb- and GABAa- mediated regulation of Up and Down states across development. J Physiol 2022; 600:2401-2427. [PMID: 35365894 DOI: 10.1113/jp282736] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2021] [Accepted: 03/18/2022] [Indexed: 11/08/2022] Open
Abstract
KEY POINTS Slow oscillations (SOs), the EEG hallmark of non-REM sleep, and their cellular counterpart, Up-and-Down states (UDSs), are considered the default activity of the cerebral cortex and reflect the underlying neural connectivity. GABAb- and GABAa- receptor-mediated inhibition play a major role in regulating UDS activity. Although SOs and UDSs exhibit significant alterations as a function of age, it is unknown how developmental changes in inhibition contribute to the developmental profile of this activity. In this study, we reveal for the first time, age-dependent effects of GABAb and GABAa signalling on UDSs. We also document the differential subunit composition of postsynaptic GABAa receptors in young and adult animals, highlighting the α1-subunit as a major component of the age-differentiated regulation of UDSs. These findings help clarify the mechanisms that underlie the maturation of cortical network activity, and enhance our understanding regarding the emergence of neurodevelopmental disorders. ABSTRACT Slow oscillations, the hallmark of non-REM sleep, and their cellular counterpart, Up-and-Down states (UDSs), are considered a signature of cortical dynamics that reflect the intrinsic network organization. Although previous studies have explored the role of inhibition in regulating UDSs, little is known about whether this role changes with maturation. This is surprising since both slow oscillations and UDSs exhibit significant age-dependent alterations. To elucidate the developmental impact of GABAb and GABAa receptors on UDS activity, we conducted simultaneous LFP and intracellular recordings ex vivo, in brain slices of young and adult male mice, using selective blockers, CGP and non-saturating concentration of gabazine, respectively. Blockade of both GABAb- and GABAa- signalling showed age-differentiated functions. CGP caused an increase in Down state duration in young animals, but a decrease in adults. Gabazine evoked Spike-and-Wave-Discharges in both ages; however, while young networks became completely epileptic, adults maintained the ability to generate UDSs. Furthermore, voltage clamp recordings of mIPSCs revealed that gabazine selectively blocks phasic currents, particularly involving postsynaptic mechanisms. The latter exhibit clear maturational changes, suggesting a different subunit composition of GABAa receptors in young vs. adult animals. Indeed, subsequent LFP recordings under diazepam (nanomolar or micromolar concentrations) revealed that mechanisms engaging the drug's classical-binding-site, mediated by α1-subunit containing GABAa receptors, have a bigger contribution in Up state initiation in young networks compared to adults. Taken together, these findings help clarify the mechanisms that underlie the maturation of cortical network activity and enhance our understanding regarding the emergence of neurodevelopmental disorders. Abstract figure legend GABAb receptors' participation in Up state termination mechanisms is well-conserved across development. However, regulation of Down-to-Up transitions is age-dependent; GABAb receptors promote them in young while preventing them in adults. Up state maintenance is determined by age-dependent synaptic GABAa receptors' subunit composition and kinetics; α1-GABAa receptors dominate in young while non-α1-GABAa receptors dominate in adults. This article is protected by copyright. All rights reserved.
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Affiliation(s)
- Ani Kaplanian
- Center for Basic Research, Biomedical Research Foundation of Academy of Athens (BRFAA), Athens, 11527, Greece.,Department of Biology, University of Patras, Rio, 26504, Greece
| | - Michael Vinos
- Center for Basic Research, Biomedical Research Foundation of Academy of Athens (BRFAA), Athens, 11527, Greece.,Department of History and Philosophy of Science, University of Athens, Athens, 15771, Greece
| | - Irini Skaliora
- Center for Basic Research, Biomedical Research Foundation of Academy of Athens (BRFAA), Athens, 11527, Greece.,Department of History and Philosophy of Science, University of Athens, Athens, 15771, Greece
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10
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Kleis P, Paschen E, Häussler U, Bernal Sierra YA, Haas CA. Long-term in vivo application of a potassium channel-based optogenetic silencer in the healthy and epileptic mouse hippocampus. BMC Biol 2022; 20:18. [PMID: 35031048 PMCID: PMC8760681 DOI: 10.1186/s12915-021-01210-1] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2021] [Accepted: 12/07/2021] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Optogenetic tools allow precise manipulation of neuronal activity via genetically encoded light-sensitive proteins. Currently available optogenetic inhibitors are not suitable for prolonged use due to short-lasting photocurrents, tissue heating, and unintended changes in ion distributions, which may interfere with normal neuron physiology. To overcome these limitations, a novel potassium channel-based optogenetic silencer, named PACK, was recently developed. The PACK tool has two components: a photoactivated adenylyl cyclase from Beggiatoa (bPAC) and a cAMP-dependent potassium channel, SthK, which carries a large, long-lasting potassium current in mammalian cells. Previously, it has been shown that activating the PACK silencer with short light pulses led to a significant reduction of neuronal firing in various in vitro and acute in vivo settings. Here, we examined the viability of performing long-term studies in vivo by looking at the inhibitory action and side effects of PACK and its components in healthy and epileptic adult male mice. RESULTS We targeted hippocampal cornu ammonis (CA1) pyramidal cells using a viral vector and enabled illumination of these neurons via an implanted optic fiber. Local field potential (LFP) recordings from CA1 of freely moving mice revealed significantly reduced neuronal activity during 50-min intermittent (0.1 Hz) illumination, especially in the gamma frequency range. Adversely, PACK expression in healthy mice induced chronic astrogliosis, dispersion of pyramidal cells, and generalized seizures. These side effects were independent of the light application and were also present in mice expressing bPAC without the potassium channel. Light activation of bPAC alone increased neuronal activity, presumably via enhanced cAMP signaling. Furthermore, we applied bPAC and PACK in the contralateral hippocampus of chronically epileptic mice following a unilateral injection of intrahippocampal kainate. Unexpectedly, the expression of bPAC in the contralateral CA1 area was sufficient to prevent the spread of spontaneous epileptiform activity from the seizure focus to the contralateral hippocampus. CONCLUSION Our study highlights the PACK tool as a potent optogenetic inhibitor in vivo. However, further refinement of its light-sensitive domain is required to avoid unexpected physiological changes.
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Affiliation(s)
- P Kleis
- Experimental Epilepsy Research, Department of Neurosurgery, Medical Center - University of Freiburg, Faculty of Medicine, 79106, Freiburg, Germany
| | - E Paschen
- Experimental Epilepsy Research, Department of Neurosurgery, Medical Center - University of Freiburg, Faculty of Medicine, 79106, Freiburg, Germany.,Faculty of Biology, University of Freiburg, 79104, Freiburg, Germany
| | - U Häussler
- Experimental Epilepsy Research, Department of Neurosurgery, Medical Center - University of Freiburg, Faculty of Medicine, 79106, Freiburg, Germany.,BrainLinks-BrainTools, University of Freiburg, 79110, Freiburg, Germany
| | - Y A Bernal Sierra
- Experimental Biophysics, Institute of Biology, Humboldt University of Berlin, 10115, Berlin, Germany
| | - C A Haas
- Experimental Epilepsy Research, Department of Neurosurgery, Medical Center - University of Freiburg, Faculty of Medicine, 79106, Freiburg, Germany. .,BrainLinks-BrainTools, University of Freiburg, 79110, Freiburg, Germany. .,Center for Basics in NeuroModulation, Faculty of Medicine, University of Freiburg, 79106, Freiburg, Germany.
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11
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Wichmann C, Kuner T. Heterogeneity of glutamatergic synapses: cellular mechanisms and network consequences. Physiol Rev 2022; 102:269-318. [PMID: 34727002 DOI: 10.1152/physrev.00039.2020] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Chemical synapses are commonly known as a structurally and functionally highly diverse class of cell-cell contacts specialized to mediate communication between neurons. They represent the smallest "computational" unit of the brain and are typically divided into excitatory and inhibitory as well as modulatory categories. These categories are subdivided into diverse types, each representing a different structure-function repertoire that in turn are thought to endow neuronal networks with distinct computational properties. The diversity of structure and function found among a given category of synapses is referred to as heterogeneity. The main building blocks for this heterogeneity are synaptic vesicles, the active zone, the synaptic cleft, the postsynaptic density, and glial processes associated with the synapse. Each of these five structural modules entails a distinct repertoire of functions, and their combination specifies the range of functional heterogeneity at mammalian excitatory synapses, which are the focus of this review. We describe synapse heterogeneity that is manifested on different levels of complexity ranging from the cellular morphology of the pre- and postsynaptic cells toward the expression of different protein isoforms at individual release sites. We attempt to define the range of structural building blocks that are used to vary the basic functional repertoire of excitatory synaptic contacts and discuss sources and general mechanisms of synapse heterogeneity. Finally, we explore the possible impact of synapse heterogeneity on neuronal network function.
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Affiliation(s)
- Carolin Wichmann
- Molecular Architecture of Synapses Group, Institute for Auditory Neuroscience, InnerEarLab and Institute for Biostructural Imaging of Neurodegeneration, University Medical Center Göttingen, Göttingen, Germany
| | - Thomas Kuner
- Department of Functional Neuroanatomy, Institute for Anatomy and Cell Biology, Heidelberg, Germany
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12
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Deutschmann AU, Kirkland JM, Briand LA. Adolescent social isolation induced alterations in nucleus accumbens glutamate signalling. Addict Biol 2022; 27:e13077. [PMID: 34278652 PMCID: PMC9206853 DOI: 10.1111/adb.13077] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2021] [Revised: 05/20/2021] [Accepted: 06/28/2021] [Indexed: 01/03/2023]
Abstract
Exposure to adversity during early childhood and adolescence increases an individual's vulnerability to developing substance use disorder. Despite the knowledge of this vulnerability, the mechanisms underlying it are still poorly understood. Excitatory afferents to the nucleus accumbens (NAc) mediate responses to both stressful and rewarding stimuli. Understanding how adolescent social isolation alters these afferents could inform the development of targeted interventions both before and after drug use. Here, we used social isolation rearing as a model of early life adversity which we have previously demonstrated increases vulnerability to cocaine addiction-like behaviour. The current study examined the effect of social isolation rearing on presynaptic glutamatergic transmission in NAc medium spiny neurons in both male and female mice. We show that social isolation rearing alters presynaptic plasticity in the NAc by decreasing the paired-pulse ratio and the size of the readily releasable pool of glutamate. Optogenetically activating the glutamatergic input from the ventral hippocampus to the NAc is sufficient to recapitulate the decreases in paired-pulse ratio and readily releasable pool size seen following electrical stimulation of all NAc afferents. Further, optogenetically inhibiting the ventral hippocampal afferent during electrical stimulation eliminates the effect of early life adversity on the paired-pulse ratio or readily releasable pool size. In summary, we demonstrate that social isolation rearing leads to alterations in glutamate transmission driven by projections from the ventral hippocampus. These data suggest that targeting the circuit from the ventral hippocampus to the nucleus accumbens could provide a means to reverse stress-induced plasticity.
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Affiliation(s)
| | | | - Lisa A. Briand
- Department of Psychology, Temple University,Neuroscience Program, Temple University
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13
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Glycine Release Is Potentiated by cAMP via EPAC2 and Ca 2+ Stores in a Retinal Interneuron. J Neurosci 2021; 41:9503-9520. [PMID: 34620721 PMCID: PMC8612479 DOI: 10.1523/jneurosci.0670-21.2021] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2021] [Revised: 09/28/2021] [Accepted: 09/30/2021] [Indexed: 11/21/2022] Open
Abstract
Neuromodulation via the intracellular second messenger cAMP is ubiquitous at presynaptic nerve terminals. This modulation of synaptic transmission allows exocytosis to adapt to stimulus levels and reliably encode information. The AII amacrine cell (AII-AC) is a central hub for signal processing in the mammalian retina. The main apical dendrite of the AII-AC is connected to several lobular appendages that release glycine onto OFF cone bipolar cells and ganglion cells. However, the influence of cAMP on glycine release is not well understood. Using membrane capacitance measurements from mouse AII-ACs to directly measure exocytosis, we observe that intracellular dialysis of 1 mm cAMP enhances exocytosis without affecting the L-type Ca2+ current. Responses to depolarizing pulses of various durations show that the size of the readily releasable pool of vesicles nearly doubles with cAMP, while paired-pulse depression experiments suggest that release probability does not change. Specific agonists and antagonists for exchange protein activated by cAMP 2 (EPAC2) revealed that the cAMP-induced enhancement of exocytosis requires EPAC2 activation. Furthermore, intact Ca2+ stores were also necessary for the cAMP potentiation of exocytosis. Postsynaptic recordings from OFF cone bipolar cells showed that increasing cAMP with forskolin potentiated the frequency of glycinergic spontaneous IPSCs. We propose that cAMP elevations in the AII-AC lead to a robust enhancement of glycine release through an EPAC2 and Ca2+ store signaling pathway. Our results thus contribute to a better understanding of how AII-AC crossover inhibitory circuits adapt to changes in ambient luminance.SIGNIFICANCE STATEMENT The mammalian retina operates over a wide dynamic range of light intensities and contrast levels. To optimize the signal-to-noise ratio of processed visual information, both excitatory and inhibitory synapses within the retina must modulate their gain in synaptic transmission to adapt to different levels of ambient light. Here we show that increases of cAMP concentration within AII amacrine cells produce enhanced exocytosis from these glycinergic interneurons. Therefore, we propose that light-sensitive neuromodulators may change the output of glycine release from AII amacrine cells. This novel mechanism may fine-tune the amount of tonic and phasic synaptic inhibition received by bipolar cell terminals and, consequently, the spiking patterns that ganglion cells send to the upstream visual areas of the brain.
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14
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Tanaka M, Sakaba T, Miki T. Quantal analysis estimates docking site occupancy determining short-term depression at hippocampal glutamatergic synapses. J Physiol 2021; 599:5301-5327. [PMID: 34705277 DOI: 10.1113/jp282235] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2021] [Accepted: 10/20/2021] [Indexed: 12/23/2022] Open
Abstract
Before fusion, synaptic vesicles (SVs) pause at discrete release/docking sites. During repetitive stimulation, the probability of site occupancy changes following SV fusion and replenishment. The occupancy probability is considered to be one of the crucial determinants of synaptic strength, but it is difficult to estimate separately because it usually blends with other synaptic parameters. Thus, the contribution of site occupancy to synaptic function, particularly to synaptic depression, remains elusive. Here, we directly estimated the occupancy probability at the hippocampal mossy fibre-CA3 interneuron synapse showing synaptic depression, using statistics of counts of vesicular events detected by deconvolution. We found that this synapse had a particularly high occupancy (∼0.85) with a high release probability of a docked SV (∼0.8) under 3 mm external calcium conditions. Analyses of quantal amplitudes and SV counts indicated that quantal size reduction decreased the amplitudes of all responses in a train to a similar degree, whereas release/docking site number was unchanged during trains, suggesting that quantal size and release/docking site number had little influence on the extent of synaptic depression. Model simulations revealed that the initial occupancy with high release probability and slow replenishment determined the time course of synaptic depression. Consistently, decreasing external calcium concentration reduced both the occupancy and release probability, and the reductions in turn produced less depression. Based on these results, we suggest that the occupancy probability is a crucial determinant of short-term synaptic depression at glutamatergic synapses in the hippocampus. KEY POINTS: The occupancy probability of a release/docking site by a synaptic vesicle at presynaptic terminals is considered to be one of the crucial determinants of synaptic strength, but it is difficult to estimate separately from other synaptic parameters. Here, we directly estimate the occupancy probability at the hippocampal mossy fibre-interneuron synapse using statistics of vesicular events detected by deconvolution. We show that the synapses have particularly high occupancy (0.85) with high release probability (0.8) under high external calcium concentration ([Ca2+ ]o ) conditions, and that both parameter values change with [Ca2+ ]o , shaping synaptic depression. Analyses of the quantal amplitudes and synaptic vesicle counts suggest that quantal sizes and release/docking site number have little influence on the extent of synaptic depression. The results suggest that the occupancy probability is a crucial determinant of short-term synaptic depression at glutamatergic synapses in the hippocampus.
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Affiliation(s)
- Mamoru Tanaka
- Graduate School of Brain Science, Doshisha University, Kyoto, Japan
| | - Takeshi Sakaba
- Graduate School of Brain Science, Doshisha University, Kyoto, Japan
| | - Takafumi Miki
- Graduate School of Brain Science, Doshisha University, Kyoto, Japan.,Organization for Research Initiatives and Development, Doshisha University, Kyoto, Japan
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15
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Ketamine increases activity of a fronto-striatal projection that regulates compulsive behavior in SAPAP3 knockout mice. Nat Commun 2021; 12:6040. [PMID: 34654803 PMCID: PMC8519915 DOI: 10.1038/s41467-021-26247-2] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2020] [Accepted: 09/17/2021] [Indexed: 12/03/2022] Open
Abstract
Obsessive-Compulsive Disorder (OCD), characterized by intrusive thoughts (obsessions) and repetitive behaviors (compulsions), is associated with dysfunction in fronto-striatal circuits. There are currently no fast-acting pharmacological treatments for OCD. However, recent clinical studies demonstrated that an intravenous infusion of ketamine rapidly reduces OCD symptoms. To probe mechanisms underlying ketamine’s therapeutic effect on OCD-like behaviors, we used the SAPAP3 knockout (KO) mouse model of compulsive grooming. Here we recapitulate the fast-acting therapeutic effect of ketamine on compulsive behavior, and show that ketamine increases activity of dorsomedial prefrontal neurons projecting to the dorsomedial striatum in KO mice. Optogenetically mimicking this increase in fronto-striatal activity reduced compulsive grooming behavior in KO mice. Conversely, inhibiting this circuit in wild-type mice increased grooming. Finally, we demonstrate that ketamine blocks the exacerbation of grooming in KO mice caused by optogenetically inhibiting fronto-striatal activity. These studies demonstrate that ketamine increases activity in a fronto-striatal circuit that causally controls compulsive grooming behavior, suggesting this circuit may be important for ketamine’s therapeutic effects in OCD. Intravenous infusion of ketamine rapidly reduces obsessive-compulsive disorder symptoms. Here, the authors show in mice that ketamine acts by increasing activity in a fronto-striatal circuit that causally controls compulsive grooming behaviour.
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16
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Climbing Fiber-Mediated Spillover Transmission to Interneurons Is Regulated by EAAT4. J Neurosci 2021; 41:8126-8133. [PMID: 34400517 DOI: 10.1523/jneurosci.0616-21.2021] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2021] [Revised: 06/21/2021] [Accepted: 07/24/2021] [Indexed: 11/21/2022] Open
Abstract
Neurotransmitter spillover is a form of communication not readily predicted by anatomic structure. In the cerebellum, glutamate spillover from climbing fibers recruits molecular layer interneurons in the absence of conventional synaptic connections. Spillover-mediated signaling is typically limited by transporters that bind and reuptake glutamate. Here, we show that patterned expression of the excitatory amino acid transporter 4 (EAAT4) in Purkinje cells regulates glutamate spillover to molecular layer interneurons. Using male and female Aldolase C-Venus knock-in mice to visualize zebrin microzones, we find larger climbing fiber-evoked spillover EPSCs in regions with low levels of EAAT4 compared with regions with high EAAT4. This difference is not explained by presynaptic glutamate release properties or postsynaptic receptor density but rather by differences in the glutamate concentration reaching receptors on interneurons. Inhibiting glutamate transport normalizes the differences between microzones, suggesting that heterogeneity in EAAT4 expression is a primary determinant of differential spillover. These results show that neuronal glutamate transporters limit extrasynaptic transmission in a non-cell-autonomous manner and provide new insight into the functional specialization of cerebellar microzones.SIGNIFICANCE STATEMENT Excitatory amino acid transporters (EAATs) help maintain the fidelity and independence of point-to-point synaptic transmission. Whereas glial transporters are critical to maintain low ambient levels of extracellular glutamate to prevent excitotoxicity, neuronal transporters have more subtle roles in shaping excitatory synaptic transmission. Here we show that the patterned expression of neuronal EAAT4 in cerebellar microzones controls glutamate spillover from cerebellar climbing fibers to nearby interneurons. These results contribute to fundamental understanding of neuronal transporter functions and specialization of cerebellar microzones.
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17
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Schmuhl-Giesen S, Rollenhagen A, Walkenfort B, Yakoubi R, Sätzler K, Miller D, von Lehe M, Hasenberg M, Lübke JHR. Sublamina-Specific Dynamics and Ultrastructural Heterogeneity of Layer 6 Excitatory Synaptic Boutons in the Adult Human Temporal Lobe Neocortex. Cereb Cortex 2021; 32:1840-1865. [PMID: 34530440 PMCID: PMC9070345 DOI: 10.1093/cercor/bhab315] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
Abstract
Synapses “govern” the computational properties of any given network in the brain. However, their detailed quantitative morphology is still rather unknown, particularly in humans. Quantitative 3D-models of synaptic boutons (SBs) in layer (L)6a and L6b of the temporal lobe neocortex (TLN) were generated from biopsy samples after epilepsy surgery using fine-scale transmission electron microscopy, 3D-volume reconstructions and electron microscopic tomography. Beside the overall geometry of SBs, the size of active zones (AZs) and that of the three pools of synaptic vesicles (SVs) were quantified. SBs in L6 of the TLN were middle-sized (~5 μm2), the majority contained only a single but comparatively large AZ (~0.20 μm2). SBs had a total pool of ~1100 SVs with comparatively large readily releasable (RRP, ~10 SVs L6a), (RRP, ~15 SVs L6b), recycling (RP, ~150 SVs), and resting (~900 SVs) pools. All pools showed a remarkably large variability suggesting a strong modulation of short-term synaptic plasticity. In conclusion, L6 SBs are highly reliable in synaptic transmission within the L6 network in the TLN and may act as “amplifiers,” “integrators” but also as “discriminators” for columnar specific, long-range extracortical and cortico-thalamic signals from the sensory periphery.
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Affiliation(s)
| | - Astrid Rollenhagen
- Institute of Neuroscience and Medicine INM-10, Research Centre Jülich GmbH, 52425, Jülich, Germany
| | - Bernd Walkenfort
- Imaging Center Essen (IMCES), Electron Microscopy Unit (EMU), Medical Faculty of the University of Duisburg-Essen, 45147, Essen, Germany
| | - Rachida Yakoubi
- Institute of Neuroscience and Medicine INM-10, Research Centre Jülich GmbH, 52425, Jülich, Germany
| | - Kurt Sätzler
- School of Biomedical Sciences, University of Ulster, Londonderry, BT52 1SA, UK
| | - Dorothea Miller
- University Hospital/Knappschaftskrankenhaus Bochum, 44892, Bochum, Germany
| | - Marec von Lehe
- Department of Neurosurgery, Brandenburg Medical School, Ruppiner Clinics, 16816, Neuruppin, Germany
| | - Mike Hasenberg
- Imaging Center Essen (IMCES), Electron Microscopy Unit (EMU), Medical Faculty of the University of Duisburg-Essen, 45147, Essen, Germany
| | - Joachim H R Lübke
- Address correspondence to Joachim Lübke, Institute of Neuroscience and Medicine INM-10, Research Centre Jülich GmbH, 52425 Jülich, Germany.
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18
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Orlando M, Dvorzhak A, Bruentgens F, Maglione M, Rost BR, Sigrist SJ, Breustedt J, Schmitz D. Recruitment of release sites underlies chemical presynaptic potentiation at hippocampal mossy fiber boutons. PLoS Biol 2021; 19:e3001149. [PMID: 34153028 PMCID: PMC8216508 DOI: 10.1371/journal.pbio.3001149] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2020] [Accepted: 02/17/2021] [Indexed: 01/14/2023] Open
Abstract
Synaptic plasticity is a cellular model for learning and memory. However, the expression mechanisms underlying presynaptic forms of plasticity are not well understood. Here, we investigate functional and structural correlates of presynaptic potentiation at large hippocampal mossy fiber boutons induced by the adenylyl cyclase activator forskolin. We performed 2-photon imaging of the genetically encoded glutamate sensor iGluu that revealed an increase in the surface area used for glutamate release at potentiated terminals. Time-gated stimulated emission depletion microscopy revealed no change in the coupling distance between P/Q-type calcium channels and release sites mapped by Munc13-1 cluster position. Finally, by high-pressure freezing and transmission electron microscopy analysis, we found a fast remodeling of synaptic ultrastructure at potentiated boutons: Synaptic vesicles dispersed in the terminal and accumulated at the active zones, while active zone density and synaptic complexity increased. We suggest that these rapid and early structural rearrangements might enable long-term increase in synaptic strength.
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Affiliation(s)
- Marta Orlando
- Charité – Universitätsmedizin Berlin, corporate member of Freie Universität Berlin and Humboldt-Universität zu Berlin, Berlin, Germany
- NeuroCure Cluster of Excellence, Berlin, Germany
| | - Anton Dvorzhak
- Charité – Universitätsmedizin Berlin, corporate member of Freie Universität Berlin and Humboldt-Universität zu Berlin, Berlin, Germany
- NeuroCure Cluster of Excellence, Berlin, Germany
| | - Felicitas Bruentgens
- Charité – Universitätsmedizin Berlin, corporate member of Freie Universität Berlin and Humboldt-Universität zu Berlin, Berlin, Germany
- NeuroCure Cluster of Excellence, Berlin, Germany
| | - Marta Maglione
- NeuroCure Cluster of Excellence, Berlin, Germany
- Department of Biology, Chemistry, and Pharmacy, Freie Universität Berlin, Berlin, Germany
| | - Benjamin R. Rost
- Charité – Universitätsmedizin Berlin, corporate member of Freie Universität Berlin and Humboldt-Universität zu Berlin, Berlin, Germany
- German Center for Neurodegenerative Diseases, Berlin, Germany
| | - Stephan J. Sigrist
- NeuroCure Cluster of Excellence, Berlin, Germany
- Department of Biology, Chemistry, and Pharmacy, Freie Universität Berlin, Berlin, Germany
- German Center for Neurodegenerative Diseases, Berlin, Germany
| | - Jörg Breustedt
- Charité – Universitätsmedizin Berlin, corporate member of Freie Universität Berlin and Humboldt-Universität zu Berlin, Berlin, Germany
- NeuroCure Cluster of Excellence, Berlin, Germany
| | - Dietmar Schmitz
- Charité – Universitätsmedizin Berlin, corporate member of Freie Universität Berlin and Humboldt-Universität zu Berlin, Berlin, Germany
- NeuroCure Cluster of Excellence, Berlin, Germany
- German Center for Neurodegenerative Diseases, Berlin, Germany
- Bernstein Center for Computational Neuroscience Berlin, Berlin, Germany
- Einstein Center for Neurosciences Berlin, Berlin, Germany
- Max Delbrück Center for Molecular Medicine, Berlin, Germany
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19
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Bhimreddy M, Rushton E, Kopke DL, Broadie K. Secreted C-type lectin regulation of neuromuscular junction synaptic vesicle dynamics modulates coordinated movement. J Cell Sci 2021; 134:261954. [PMID: 33973638 DOI: 10.1242/jcs.257592] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2020] [Accepted: 04/03/2021] [Indexed: 11/20/2022] Open
Abstract
The synaptic cleft manifests enriched glycosylation, with structured glycans coordinating signaling between presynaptic and postsynaptic cells. Glycosylated signaling ligands orchestrating communication are tightly regulated by secreted glycan-binding lectins. Using the Drosophila neuromuscular junction (NMJ) as a model glutamatergic synapse, we identify a new Ca2+-binding (C-type) lectin, Lectin-galC1 (LGC1), which modulates presynaptic function and neurotransmission strength. We find that LGC1 is enriched in motoneuron presynaptic boutons and secreted into the NMJ extracellular synaptomatrix. We show that LGC1 limits locomotor peristalsis and coordinated movement speed, with a specific requirement for synaptic function, but not NMJ architecture. LGC1 controls neurotransmission strength by limiting presynaptic active zone (AZ) and postsynaptic glutamate receptor (GluR) aligned synapse number, reducing both spontaneous and stimulation-evoked synaptic vesicle (SV) release, and capping SV cycling rate. During high-frequency stimulation (HFS), mutants have faster synaptic depression and impaired recovery while replenishing depleted SV pools. Although LGC1 removal increases the number of glutamatergic synapses, we find that LGC1-null mutants exhibit decreased SV density within presynaptic boutons, particularly SV pools at presynaptic active zones. Thus, LGC1 regulates NMJ neurotransmission to modulate coordinated movement.
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Affiliation(s)
- Meghana Bhimreddy
- Department of Biological Sciences, Vanderbilt University and Medical Center, Nashville, TN 37235, USA
| | - Emma Rushton
- Department of Biological Sciences, Vanderbilt University and Medical Center, Nashville, TN 37235, USA
| | - Danielle L Kopke
- Department of Biological Sciences, Vanderbilt University and Medical Center, Nashville, TN 37235, USA
| | - Kendal Broadie
- Department of Biological Sciences, Vanderbilt University and Medical Center, Nashville, TN 37235, USA.,Kennedy Center for Research on Human Development, Vanderbilt University and Medical Center, Nashville, TN 37235, USA.,Vanderbilt Brain Institute, Vanderbilt University and Medical Center, Nashville, TN 37235, USA
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Oldani S, Moreno-Velasquez L, Faiss L, Stumpf A, Rosenmund C, Schmitz D, Rost BR. SynaptoPAC, an optogenetic tool for induction of presynaptic plasticity. J Neurochem 2020; 156:324-336. [PMID: 33037623 DOI: 10.1111/jnc.15210] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2020] [Revised: 09/21/2020] [Accepted: 10/01/2020] [Indexed: 11/26/2022]
Abstract
Optogenetic manipulations have transformed neuroscience in recent years. While sophisticated tools now exist for controlling the firing patterns of neurons, it remains challenging to optogenetically define the plasticity state of individual synapses. A variety of synapses in the mammalian brain express presynaptic long-term potentiation (LTP) upon elevation of presynaptic cyclic adenosine monophosphate (cAMP), but the molecular expression mechanisms as well as the impact of presynaptic LTP on network activity and behavior are not fully understood. In order to establish optogenetic control of presynaptic cAMP levels and thereby presynaptic potentiation, we developed synaptoPAC, a presynaptically targeted version of the photoactivated adenylyl cyclase bPAC. In cultures of hippocampal granule cells of Wistar rats, activation of synaptoPAC with blue light increased action potential-evoked transmission, an effect not seen in hippocampal cultures of non-granule cells. In acute brain slices of C57BL/6N mice, synaptoPAC activation immediately triggered a strong presynaptic potentiation at mossy fiber synapses in CA3, but not at Schaffer collateral synapses in CA1. Following light-triggered potentiation, mossy fiber transmission decreased within 20 min, but remained enhanced still after 30 min. The optogenetic potentiation altered the short-term plasticity dynamics of release, reminiscent of presynaptic LTP. Our work establishes synaptoPAC as an optogenetic tool that enables acute light-controlled potentiation of transmitter release at specific synapses in the brain, facilitating studies of the role of presynaptic potentiation in network function and animal behavior in an unprecedented manner. Read the Editorial Highlight for this article on page 270.
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Affiliation(s)
- Silvia Oldani
- German Center for Neurodegenerative Diseases (DZNE), 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, Berlin, Germany
| | - Laura Moreno-Velasquez
- Charité - Universitätsmedizin Berlin, corporate member of Freie Universität Berlin and Humboldt-Universität zu Berlin, and Berlin Institute of Health, NeuroCure Cluster of Excellence, Berlin, Germany
| | - Lukas Faiss
- German Center for Neurodegenerative Diseases (DZNE), 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, Berlin, Germany
| | - Alexander Stumpf
- Charité - Universitätsmedizin Berlin, corporate member of Freie Universität Berlin and Humboldt-Universität zu Berlin, and Berlin Institute of Health, NeuroCure Cluster of Excellence, Berlin, Germany
| | - Christian Rosenmund
- Charité - Universitätsmedizin Berlin, corporate member of Freie Universität Berlin and Humboldt-Universität zu Berlin, and Berlin Institute of Health, NeuroCure Cluster of Excellence, Berlin, Germany
| | - Dietmar Schmitz
- German Center for Neurodegenerative Diseases (DZNE), 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, Berlin, Germany.,Max-Delbruck-Centrum (MDC) for Molecular Medicine in the Helmholtz Association, Berlin, Germany.,Bernstein Center for Computational Neuroscience, Berlin, Germany.,Einstein Center for Neurosciences Berlin, Berlin, Germany
| | - Benjamin R Rost
- German Center for Neurodegenerative Diseases (DZNE), Berlin, Germany
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21
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Synaptic Organization of the Human Temporal Lobe Neocortex as Revealed by High-Resolution Transmission, Focused Ion Beam Scanning, and Electron Microscopic Tomography. Int J Mol Sci 2020; 21:ijms21155558. [PMID: 32756507 PMCID: PMC7432700 DOI: 10.3390/ijms21155558] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2020] [Revised: 07/27/2020] [Accepted: 07/29/2020] [Indexed: 01/02/2023] Open
Abstract
Modern electron microscopy (EM) such as fine-scale transmission EM, focused ion beam scanning EM, and EM tomography have enormously improved our knowledge about the synaptic organization of the normal, developmental, and pathologically altered brain. In contrast to various animal species, comparably little is known about these structures in the human brain. Non-epileptic neocortical access tissue from epilepsy surgery was used to generate quantitative 3D models of synapses. Beside the overall geometry, the number, size, and shape of active zones and of the three functionally defined pools of synaptic vesicles representing morphological correlates for synaptic transmission and plasticity were quantified. EM tomography further allowed new insights in the morphological organization and size of the functionally defined readily releasable pool. Beside similarities, human synaptic boutons, although comparably small (approximately 5 µm), differed substantially in several structural parameters, such as the shape and size of active zones, which were on average 2 to 3-fold larger than in experimental animals. The total pool of synaptic vesicles exceeded that in experimental animals by approximately 2 to 3-fold, in particular the readily releasable and recycling pool by approximately 2 to 5-fold, although these pools seemed to be layer-specifically organized. Taken together, synaptic boutons in the human temporal lobe neocortex represent unique entities perfectly adapted to the “job” they have to fulfill in the circuitry in which they are embedded. Furthermore, the quantitative 3D models of synaptic boutons are useful to explain and even predict the functional properties of synaptic connections in the human neocortex.
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22
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Vaden RJ, Gonzalez JC, Tsai MC, Niver AJ, Fusilier AR, Griffith CM, Kramer RH, Wadiche JI, Overstreet-Wadiche L. Parvalbumin interneurons provide spillover to newborn and mature dentate granule cells. eLife 2020; 9:54125. [PMID: 32602839 PMCID: PMC7326496 DOI: 10.7554/elife.54125] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2019] [Accepted: 06/19/2020] [Indexed: 01/09/2023] Open
Abstract
Parvalbumin-expressing interneurons (PVs) in the dentate gyrus provide activity-dependent regulation of adult neurogenesis as well as maintain inhibitory control of mature neurons. In mature neurons, PVs evoke GABAA postsynaptic currents (GPSCs) with fast rise and decay phases that allow precise control of spike timing, yet synaptic currents with fast kinetics do not appear in adult-born neurons until several weeks after cell birth. Here we used mouse hippocampal slices to address how PVs signal to newborn neurons prior to the appearance of fast GPSCs. Whereas PV-evoked currents in mature neurons exhibit hallmark fast rise and decay phases, newborn neurons display slow GPSCs with characteristics of spillover signaling. We also unmasked slow spillover currents in mature neurons in the absence of fast GPSCs. Our results suggest that PVs mediate slow spillover signaling in addition to conventional fast synaptic signaling, and that spillover transmission mediates activity-dependent regulation of early events in adult neurogenesis.
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Affiliation(s)
- Ryan J Vaden
- Department of Neurobiology, University of Alabama at Birmingham, Birmingham, United States
| | - Jose Carlos Gonzalez
- Department of Neurobiology, University of Alabama at Birmingham, Birmingham, United States
| | - Ming-Chi Tsai
- Department of Molecular and Cellular Biology, University of California Berkeley, Berkeley, United States
| | - Anastasia J Niver
- Department of Neurobiology, University of Alabama at Birmingham, Birmingham, United States
| | - Allison R Fusilier
- Department of Neurobiology, University of Alabama at Birmingham, Birmingham, United States
| | - Chelsea M Griffith
- Department of Neurobiology, University of Alabama at Birmingham, Birmingham, United States
| | - Richard H Kramer
- Department of Molecular and Cellular Biology, University of California Berkeley, Berkeley, United States
| | - Jacques I Wadiche
- Department of Neurobiology, University of Alabama at Birmingham, Birmingham, United States
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23
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A Slow Short-Term Depression at Purkinje to Deep Cerebellar Nuclear Neuron Synapses Supports Gain-Control and Linear Encoding over Second-Long Time Windows. J Neurosci 2020; 40:5937-5953. [PMID: 32554551 DOI: 10.1523/jneurosci.2078-19.2020] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2019] [Revised: 04/21/2020] [Accepted: 05/23/2020] [Indexed: 11/21/2022] Open
Abstract
Modifications in the sensitivity of neural elements allow the brain to adapt its functions to varying demands. Frequency-dependent short-term synaptic depression (STD) provides a dynamic gain-control mechanism enabling adaptation to different background conditions alongside enhanced sensitivity to input-driven changes in activity. In contrast, synapses displaying frequency-invariant transmission can faithfully transfer ongoing presynaptic rates enabling linear processing, deemed critical for many functions. However, rigid frequency-invariant transmission may lead to runaway dynamics and low sensitivity to changes in rate. Here, I investigated the Purkinje cell to deep cerebellar nuclei neuron synapses (PC_DCNs), which display frequency invariance, and yet, PCs maintain background activity at disparate rates, even at rest. Using protracted PC_DCN activation (120 s) to mimic background activity in cerebellar slices from mature mice of both sexes, I identified a previously unrecognized, frequency-dependent, slow STD (S-STD), adapting IPSC amplitudes in tens of seconds to minutes. However, after changes in activation rates, over a behavior-relevant second-long time window, S-STD enabled scaled linear encoding of PC rates in synaptic charge transfer and DCN spiking activity. Combined electrophysiology, optogenetics, and statistical analysis suggested that S-STD mechanism is input-specific, involving decreased ready-to-release quanta, and distinct from faster short-term plasticity (f-STP). Accordingly, an S-STD component with a scaling effect (i.e., activity-dependent release sites inactivation), extending a model explaining PC_DCN release on shorter timescales using balanced f-STP, reproduced the experimental results. Thus, these results elucidates a novel slow gain-control mechanism able to support linear transfer of behavior-driven/learned PC rates concurrently with background activity adaptation, and furthermore, provides an alternative pathway to refine PC output.SIGNIFICANCE STATEMENT The brain can adapt to varying demands by dynamically changing the gain of its synapses; however, some tasks require ongoing linear transfer of presynaptic rates, seemingly incompatible with nonlinear gain adaptation. Here, I report a novel slow gain-control mechanism enabling scaled linear encoding of presynaptic rates over behavior-relevant time windows, and adaptation to background activity at the Purkinje to deep cerebellar nuclear neurons synapses (PC_DCNs). A previously unrecognized PC_DCNs slow and frequency-dependent short-term synaptic depression (S-STD) mediates this process. Experimental evidence and simulations suggested that scaled linear encoding emerges from the combination of S-STD slow dynamics and frequency-invariant transmission at faster timescales. These results demonstrate a mechanism reconciling rate code with background activity adaptation and suitable for flexibly tuning PCs output via background activity modulation.
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24
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Bednarz K, Alshafie W, Aufmkolk S, Desserteaux T, Markam PS, Storch KF, Stroh T. Ultradian Secretion of Growth Hormone in Mice: Linking Physiology With Changes in Synapse Parameters Using Super-Resolution Microscopy. Front Neural Circuits 2020; 14:21. [PMID: 32523515 PMCID: PMC7261915 DOI: 10.3389/fncir.2020.00021] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2020] [Accepted: 04/14/2020] [Indexed: 01/19/2023] Open
Abstract
Neuroendocrine circuits are orchestrated by the pituitary gland in response to hypothalamic hormone-releasing and inhibiting factors to generate an ultradian and/or circadian rhythm of hormone secretion. However, mechanisms that govern this rhythmicity are not fully understood. It has been shown that synaptic transmission in the rodent hypothalamus undergoes cyclical changes in parallel with rhythmic hormone secretion and a growing body of evidence suggests that rapid rewiring of hypothalamic neurons may be the source of these changes. For decades, structural synaptic studies have been utilizing electron microscopy, which provides the resolution suitable for visualizing synapses. However, the small field of view, limited specificity and manual analysis susceptible to bias fuel the search for a more quantitative approach. Here, we apply the fluorescence super-resolution microscopy approach direct Stochastic Optical Reconstruction Microscopy (dSTORM) to quantify and structurally characterize excitatory and inhibitory synapses that contact growth hormone-releasing-hormone (GHRH) neurons during peak and trough values of growth hormone (GH) concentration in mice. This approach relies on a three-color immunofluorescence staining of GHRH and pre- and post-synaptic markers, and a quantitative analysis with a Density-Based Spatial Clustering of Applications with Noise (DBSCAN) algorithm. With this method we confirm our previous findings, using electron microscopy, of increased excitatory synaptic input to GHRH neurons during peak levels of GH. Additionally, we find a shift in synapse numbers during low GH levels, where more inhibitory synaptic inputs are detected. Lastly, we utilize dSTORM to study novel aspects of synaptic structure. We show that more excitatory (but not inhibitory) pre-synaptic clusters associate with excitatory post-synaptic clusters during peaks of GH secretion and that the numbers of post-synaptic clusters increase during high hormone levels. The results presented here provide an opportunity to highlight dSTORM as a valuable quantitative approach to study synaptic structure in the neuroendocrine circuit. Importantly, our analysis of GH circuitry sheds light on the potential mechanism that drives ultradian changes in synaptic transmission and possibly aids in GH pulse generation in mice.
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Affiliation(s)
- Klaudia Bednarz
- Department of Neurology and Neurosurgery, Montreal Neurological Institute, McGill University, Montreal, QC, Canada.,Department of Anatomy and Cell Biology, McGill University, Montreal, QC, Canada
| | - Walaa Alshafie
- Department of Neurology and Neurosurgery, Montreal Neurological Institute, McGill University, Montreal, QC, Canada.,Integrated Program in Neuroscience, McGill University, Montreal, QC, Canada
| | - Sarah Aufmkolk
- Department of Genetics, Harvard Medical School, Boston, MA, United States
| | - Théotime Desserteaux
- Department of Neurology and Neurosurgery, Montreal Neurological Institute, McGill University, Montreal, QC, Canada
| | - Pratap Singh Markam
- Integrated Program in Neuroscience, McGill University, Montreal, QC, Canada.,Douglas Mental Health University Institute, Montreal, QC, Canada
| | - Kai-Florian Storch
- Douglas Mental Health University Institute, Montreal, QC, Canada.,Department of Psychiatry, McGill University, Montreal, QC, Canada
| | - Thomas Stroh
- Department of Neurology and Neurosurgery, Montreal Neurological Institute, McGill University, Montreal, QC, Canada.,Department of Anatomy and Cell Biology, McGill University, Montreal, QC, Canada
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25
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Prume M, Rollenhagen A, Yakoubi R, Sätzler K, Lübke JH. Quantitative Three-Dimensional Reconstructions of Excitatory Synaptic Boutons in the "Barrel Field" of the Adult "Reeler" Mouse Somatosensory Neocortex: A Comparative Fine-Scale Electron Microscopic Analysis with the Wild Type Mouse. Cereb Cortex 2020; 30:3209-3227. [PMID: 31813963 DOI: 10.1093/cercor/bhz304] [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] [Indexed: 12/11/2022] Open
Abstract
Synapses are key structural determinants for information processing and computations in the normal and pathologically altered brain. Here, the quantitative morphology of excitatory synaptic boutons in the "reeler" mutant, a model system for various neurological disorders, was investigated and compared with wild-type (WT) mice using high-resolution, fine-scale electron microscopy (EM) and quantitative three-dimensional (3D) models of synaptic boutons. Beside their overall geometry, the shape and size of presynaptic active zones (PreAZs) and postsynaptic densities (PSDs) forming the active zones and the three pools of synaptic vesicles (SVs), namely the readily releasable pool (RRP), the recycling pool (RP), and the resting pool, were quantified. Although the reeler mouse neocortex is severely disturbed, no significant differences were found in most of the structural parameters investigated: the size of boutons (~3 μm2), size of the PreAZs and PSDs (~0.17 μm2), total number of SVs, and SVs within a perimeter (p) of 10 nm and p20 nm RRP; the p60 nm, p100 nm, and p60-p200 nm RP; and the resting pool, except the synaptic cleft width. Taken together, the synaptic organization and structural composition of synaptic boutons in the reeler neocortex remain comparably "normal" and may thus contribute to a "correct" wiring of neurons within the reeler cortical network.
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Affiliation(s)
- Miriam Prume
- Institute of Neuroscience and Medicine INM-10, Research Centre Jülich GmbH, 52425 Jülich, Germany
| | - Astrid Rollenhagen
- Institute of Neuroscience and Medicine INM-10, Research Centre Jülich GmbH, 52425 Jülich, Germany
| | - Rachida Yakoubi
- Institute of Neuroscience and Medicine INM-10, Research Centre Jülich GmbH, 52425 Jülich, Germany
| | - Kurt Sätzler
- School of Biomedical Sciences, University of Ulster, Londonderry BT52 1SA, UK
| | - Joachim Hr Lübke
- Institute of Neuroscience and Medicine INM-10, Research Centre Jülich GmbH, 52425 Jülich, Germany.,Department of Psychiatry, Psychotherapy and Psychosomatics, Medical Faculty, RWTH University Hospital Aachen, 52074 Aachen, Germany.,JARA Translational Brain Medicine, Jülich/Aachen, Germany
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26
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Area-Specific Synapse Structure in Branched Posterior Nucleus Axons Reveals a New Level of Complexity in Thalamocortical Networks. J Neurosci 2020; 40:2663-2679. [PMID: 32054677 PMCID: PMC7096142 DOI: 10.1523/jneurosci.2886-19.2020] [Citation(s) in RCA: 28] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2019] [Revised: 02/04/2020] [Accepted: 02/05/2020] [Indexed: 12/05/2022] Open
Abstract
Thalamocortical posterior nucleus (Po) axons innervating the vibrissal somatosensory (S1) and motor (MC) cortices are key links in the brain neuronal network that allows rodents to explore the environment whisking with their motile snout vibrissae. Thalamocortical posterior nucleus (Po) axons innervating the vibrissal somatosensory (S1) and motor (MC) cortices are key links in the brain neuronal network that allows rodents to explore the environment whisking with their motile snout vibrissae. Here, using fine-scale high-end 3D electron microscopy, we demonstrate in adult male C57BL/6 wild-type mice marked differences between MC versus S1 Po synapses in (1) bouton and active zone size, (2) neurotransmitter vesicle pool size, (3) distribution of mitochondria around synapses, and (4) proportion of synapses established on dendritic spines and dendritic shafts. These differences are as large, or even more pronounced, than those between Po and ventro-posterior thalamic nucleus synapses in S1. Moreover, using single-axon transfection labeling, we demonstrate that the above differences actually occur on the MC versus the S1 branches of individual Po cell axons that innervate both areas. Along with recently-discovered divergences in efficacy and plasticity, the synaptic structure differences reported here thus reveal a new subcellular level of complexity. This is a finding that upends current models of thalamocortical circuitry, and that might as well illuminate the functional logic of other branched projection axon systems. SIGNIFICANCE STATEMENT Many long-distance brain connections depend on neurons whose branched axons target separate regions. Using 3D electron microscopy and single-cell transfection, we investigated the mouse Posterior thalamic nucleus (Po) cell axons that simultaneously innervate motor and sensory areas of the cerebral cortex involved in whisker movement control. We demonstrate significant differences in the size of the boutons made in each area by individual Po axons, as well as in functionally-relevant parameters in the composition of their synapses. In addition, we found similarly large differences between the synapses of Po versus ventral posteromedial thalamic nucleus axons in the whisker sensory cortex. Area-specific synapse structure in individual axons implies a new, unsuspected level of complexity in long-distance brain connections.
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27
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Yakoubi R, Rollenhagen A, von Lehe M, Miller D, Walkenfort B, Hasenberg M, Sätzler K, Lübke JH. Ultrastructural heterogeneity of layer 4 excitatory synaptic boutons in the adult human temporal lobe neocortex. eLife 2019; 8:48373. [PMID: 31746736 PMCID: PMC6919978 DOI: 10.7554/elife.48373] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2019] [Accepted: 11/19/2019] [Indexed: 01/09/2023] Open
Abstract
Synapses are fundamental building blocks controlling and modulating the ‘behavior’ of brain networks. How their structural composition, most notably their quantitative morphology underlie their computational properties remains rather unclear, particularly in humans. Here, excitatory synaptic boutons (SBs) in layer 4 (L4) of the temporal lobe neocortex (TLN) were quantitatively investigated. Biopsies from epilepsy surgery were used for fine-scale and tomographic electron microscopy (EM) to generate 3D-reconstructions of SBs. Particularly, the size of active zones (AZs) and that of the three functionally defined pools of synaptic vesicles (SVs) were quantified. SBs were comparatively small (~2.50 μm2), with a single AZ (~0.13 µm2); preferentially established on spines. SBs had a total pool of ~1800 SVs with strikingly large readily releasable (~20), recycling (~80) and resting pools (~850). Thus, human L4 SBs may act as ‘amplifiers’ of signals from the sensory periphery, integrate, synchronize and modulate intra- and extracortical synaptic activity.
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Affiliation(s)
- Rachida Yakoubi
- Institute of Neuroscience and Medicine INM-10, Research Centre Jülich GmbH, Jülich, Germany
| | - Astrid Rollenhagen
- Institute of Neuroscience and Medicine INM-10, Research Centre Jülich GmbH, Jülich, Germany
| | - Marec von Lehe
- Department of Neurosurgery, Knappschaftskrankenhaus Bochum, Bochum, Germany.,Department of Neurosurgery, Brandenburg Medical School, Ruppiner Clinics, Neuruppin, Germany
| | - Dorothea Miller
- Department of Neurosurgery, Knappschaftskrankenhaus Bochum, Bochum, Germany
| | - Bernd Walkenfort
- Medical Research Centre, IMCES Electron Microscopy Unit (EMU), University Hospital Essen, Essen, Germany
| | - Mike Hasenberg
- Medical Research Centre, IMCES Electron Microscopy Unit (EMU), University Hospital Essen, Essen, Germany
| | - Kurt Sätzler
- School of Biomedical Sciences, University of Ulster, Londonderry, United Kingdom
| | - Joachim Hr Lübke
- Institute of Neuroscience and Medicine INM-10, Research Centre Jülich GmbH, Jülich, Germany.,Department of Psychiatry, Psychotherapy and Psychosomatics, Faculty of Medicine, RWTH University Hospital Aachen, Aachen, Germany.,JARA Translational Brain Medicine, Jülich/Aachen, Germany
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