1
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Arellano JI, Rakic P. Modelling adult neurogenesis in the aging rodent hippocampus: a midlife crisis. Front Neurosci 2024; 18:1416460. [PMID: 38887368 PMCID: PMC11181911 DOI: 10.3389/fnins.2024.1416460] [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: 04/12/2024] [Accepted: 05/17/2024] [Indexed: 06/20/2024] Open
Abstract
Contrary to humans, adult hippocampal neurogenesis in rodents is not controversial. And in the last three decades, multiple studies in rodents have deemed adult neurogenesis essential for most hippocampal functions. The functional relevance of new neurons relies on their distinct physiological properties during their maturation before they become indistinguishable from mature granule cells. Most functional studies have used very young animals with robust neurogenesis. However, this trait declines dramatically with age, questioning its functional relevance in aging animals, a caveat that has been mentioned repeatedly, but rarely analyzed quantitatively. In this meta-analysis, we use data from published studies to determine the critical functional window of new neurons and to model their numbers across age in both mice and rats. Our model shows that new neurons with distinct functional profile represent about 3% of the total granule cells in young adult 3-month-old rodents, and their number decline following a power function to reach less than 1% in middle aged animals and less than 0.5% in old mice and rats. These low ratios pose an important logical and computational caveat to the proposed essential role of new neurons in the dentate gyrus, particularly in middle aged and old animals, a factor that needs to be adequately addressed when defining the relevance of adult neurogenesis in hippocampal function.
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Affiliation(s)
- Jon I. Arellano
- Department of Neuroscience, Yale University, New Haven, CT, United States
| | - Pasko Rakic
- Department of Neuroscience, Yale University, New Haven, CT, United States
- Kavli Institute for Neuroscience at Yale, Yale University, New Haven, CT, United States
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2
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Islam R, White JD, Arefin TM, Mehta S, Liu X, Polis B, Giuliano L, Ahmed S, Bowers C, Zhang J, Kaffman A. Early adversity causes sex-specific deficits in perforant pathway connectivity and contextual memory in adolescent mice. Biol Sex Differ 2024; 15:39. [PMID: 38715106 PMCID: PMC11075329 DOI: 10.1186/s13293-024-00616-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/07/2023] [Accepted: 04/26/2024] [Indexed: 05/12/2024] Open
Abstract
BACKGROUND Early life adversity impairs hippocampal development and function across diverse species. While initial evidence indicated potential variations between males and females, further research is required to validate these observations and better understand the underlying mechanisms contributing to these sex differences. Furthermore, most of the preclinical work in rodents was performed in adult males, with only few studies examining sex differences during adolescence when such differences appear more pronounced. To address these concerns, we investigated the impact of limited bedding (LB), a mouse model of early adversity, on hippocampal development in prepubescent and adolescent male and female mice. METHODS RNA sequencing, confocal microscopy, and electron microscopy were used to evaluate the impact of LB and sex on hippocampal development in prepubescent postnatal day 17 (P17) mice. Additional studies were conducted on adolescent mice aged P29-36, which included contextual fear conditioning, retrograde tracing, and ex vivo diffusion magnetic resonance imaging (dMRI). RESULTS More severe deficits in axonal innervation and myelination were found in the perforant pathway of prepubescent and adolescent LB males compared to LB female littermates. These sex differences were due to a failure of reelin-positive neurons located in the lateral entorhinal cortex (LEC) to innervate the dorsal hippocampus via the perforant pathway in males, but not LB females, and were strongly correlated with deficits in contextual fear conditioning. CONCLUSIONS LB impairs the capacity of reelin-positive cells located in the LEC to project and innervate the dorsal hippocampus in LB males but not female LB littermates. Given the critical role that these projections play in supporting normal hippocampal function, a failure to establish proper connectivity between the LEC and the dorsal hippocampus provides a compelling and novel mechanism to explain the more severe deficits in myelination and contextual freezing found in adolescent LB males.
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Affiliation(s)
- Rafiad Islam
- Department of Psychiatry, Yale University School of Medicine, 300 George Street, Suite 901, New Haven, CT, 06511, USA
| | - Jordon D White
- Department of Psychiatry, Yale University School of Medicine, 300 George Street, Suite 901, New Haven, CT, 06511, USA
| | - Tanzil M Arefin
- Bernard and Irene Schwartz Center for Biomedical Imaging, Department of Radiology, New York University School of Medicine, New York, NY, 10016, USA
- Department of Biomedical Engineering, Center for Neurotechnology in Mental Health Research (CNMHR), The Pennsylvania State University, University Park, PA, 16802, USA
| | - Sameet Mehta
- Yale Center for Genomic Analysis, P.O. Box 27386, West Haven, CT, 06516-7386, USA
| | - Xinran Liu
- Department of Cell Biology, Yale University School of Medicine, 333 Cedar Street, SHM IE26, New Haven, CT, 06510, USA
- Center for Cellular and Molecular Imaging, Electron Microscopy Core Facility, Yale University School of Medicine, New Haven, CT, USA
| | - Baruh Polis
- Department of Psychiatry, Yale University School of Medicine, 300 George Street, Suite 901, New Haven, CT, 06511, USA
| | - Lauryn Giuliano
- Department of Psychiatry, Yale University School of Medicine, 300 George Street, Suite 901, New Haven, CT, 06511, USA
| | - Sahabuddin Ahmed
- Department of Psychiatry, Yale University School of Medicine, 300 George Street, Suite 901, New Haven, CT, 06511, USA
| | - Christian Bowers
- Department of Psychiatry, Yale University School of Medicine, 300 George Street, Suite 901, New Haven, CT, 06511, USA
| | - Jiangyang Zhang
- Bernard and Irene Schwartz Center for Biomedical Imaging, Department of Radiology, New York University School of Medicine, New York, NY, 10016, USA
| | - Arie Kaffman
- Department of Psychiatry, Yale University School of Medicine, 300 George Street, Suite 901, New Haven, CT, 06511, USA.
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3
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Ventura S, Duncan S, Ainge JA. Increased flexibility of CA3 memory representations following environmental enrichment. Curr Biol 2024; 34:2011-2019.e7. [PMID: 38636511 DOI: 10.1016/j.cub.2024.03.054] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2023] [Revised: 02/16/2024] [Accepted: 03/25/2024] [Indexed: 04/20/2024]
Abstract
Environmental enrichment (EE) improves memory, particularly the ability to discriminate similar past experiences.1,2,3,4,5,6 The hippocampus supports this ability via pattern separation, the encoding of similar events using dissimilar memory representations.7 This is carried out in the dentate gyrus (DG) and CA3 subfields.8,9,10,11,12 Upregulation of adult neurogenesis in the DG improves memory through enhanced pattern separation.1,2,3,4,5,6,11,13,14,15,16 Adult-born granule cells (abGCs) in DG are suggested to contribute to pattern separation by driving inhibition in regions such as CA3,13,14,15,16,17,18 leading to sparser, nonoverlapping representations of similar events (although a role for abGCs in driving excitation in the hippocampus has also been reported16). Place cells in the hippocampus contribute to pattern separation by remapping to spatial and contextual alterations to the environment.19,20,21,22,23,24,25,26,27 How spatial responses in CA3 are affected by EE and input from increased numbers of abGCs in DG is, however, unknown. Here, we investigate the neural mechanisms facilitating improved memory following EE using associative recognition memory tasks that model the automatic and integrative nature of episodic memory. We find that EE-dependent improvements in difficult discriminations are related to increased neurogenesis and sparser memory representations across the hippocampus. Additionally, we report for the first time that EE changes how CA3 place cells discriminate similar contexts. CA3 place cells of enriched rats show greater spatial tuning, increased firing rates, and enhanced remapping to contextual changes. These findings point to more precise and flexible CA3 memory representations in enriched rats, which provides a putative mechanism for EE-dependent improvements in fine memory discrimination.
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Affiliation(s)
- Silvia Ventura
- School of Psychology & Neuroscience, University of St. Andrews, St. Mary's Quad, South Street, St. Andrews, Fife, Scotland KY16 9JP, UK
| | - Stephen Duncan
- School of Psychology & Neuroscience, University of St. Andrews, St. Mary's Quad, South Street, St. Andrews, Fife, Scotland KY16 9JP, UK; School of Psychological & Brain Sciences, Indiana University, 1101 E 10th Street, Bloomington, IN 47405, USA
| | - James A Ainge
- School of Psychology & Neuroscience, University of St. Andrews, St. Mary's Quad, South Street, St. Andrews, Fife, Scotland KY16 9JP, UK.
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4
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Santiago RMM, Lopes-Dos-Santos V, Aery Jones EA, Huang Y, Dupret D, Tort ABL. Waveform-based classification of dentate spikes. Sci Rep 2024; 14:2989. [PMID: 38316828 PMCID: PMC10844627 DOI: 10.1038/s41598-024-53075-3] [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: 12/10/2023] [Accepted: 01/27/2024] [Indexed: 02/07/2024] Open
Abstract
Synchronous excitatory discharges from the entorhinal cortex (EC) to the dentate gyrus (DG) generate fast and prominent patterns in the hilar local field potential (LFP), called dentate spikes (DSs). As sharp-wave ripples in CA1, DSs are more likely to occur in quiet behavioral states, when memory consolidation is thought to take place. However, their functions in mnemonic processes are yet to be elucidated. The classification of DSs into types 1 or 2 is determined by their origin in the lateral or medial EC, as revealed by current source density (CSD) analysis, which requires recordings from linear probes with multiple electrodes spanning the DG layers. To allow the investigation of the functional role of each DS type in recordings obtained from single electrodes and tetrodes, which are abundant in the field, we developed an unsupervised method using Gaussian mixture models to classify such events based on their waveforms. Our classification approach achieved high accuracies (> 80%) when validated in 8 mice with DG laminar profiles. The average CSDs, waveforms, rates, and widths of the DS types obtained through our method closely resembled those derived from the CSD-based classification. As an example of application, we used the technique to analyze single-electrode LFPs from apolipoprotein (apo) E3 and apoE4 knock-in mice. We observed that the latter group, which is a model for Alzheimer's disease, exhibited wider DSs of both types from a young age, with a larger effect size for DS type 2, likely reflecting early pathophysiological alterations in the EC-DG network, such as hyperactivity. In addition to the applicability of the method in expanding the study of DS types, our results show that their waveforms carry information about their origins, suggesting different underlying network dynamics and roles in memory processing.
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Affiliation(s)
- Rodrigo M M Santiago
- Computational Neurophysiology Lab, Brain Institute, Federal University of Rio Grande do Norte, Natal, RN, 59078-900, Brazil.
| | - Vítor Lopes-Dos-Santos
- Medical Research Council Brain Network Dynamics Unit, Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, UK
| | - Emily A Aery Jones
- Department of Neurobiology, Stanford University School of Medicine, Stanford, CA, 94305, USA
| | - Yadong Huang
- Gladstone Institute of Neurological Disease, Gladstone Institutes, San Francisco, CA, 94158, USA
| | - David Dupret
- Medical Research Council Brain Network Dynamics Unit, Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, UK
| | - Adriano B L Tort
- Computational Neurophysiology Lab, Brain Institute, Federal University of Rio Grande do Norte, Natal, RN, 59078-900, Brazil
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5
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Li H, Tamura R, Hayashi D, Asai H, Koga J, Ando S, Yokota S, Kaneko J, Sakurai K, Sumiyoshi A, Yamamoto T, Hikishima K, Tanaka KZ, McHugh TJ, Hisatsune T. Silencing dentate newborn neurons alters excitatory/inhibitory balance and impairs behavioral inhibition and flexibility. SCIENCE ADVANCES 2024; 10:eadk4741. [PMID: 38198539 PMCID: PMC10780870 DOI: 10.1126/sciadv.adk4741] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/24/2023] [Accepted: 12/13/2023] [Indexed: 01/12/2024]
Abstract
Adult neurogenesis confers the hippocampus with unparalleled neural plasticity, essential for intricate cognitive functions. The specific influence of sparse newborn neurons (NBNs) in modulating neural activities and subsequently steering behavior, however, remains obscure. Using an engineered NBN-tetanus toxin mouse model (NBN-TeTX), we noninvasively silenced NBNs, elucidating their crucial role in impulse inhibition and cognitive flexibility as evidenced through Morris water maze reversal learning and Go/Nogo task in operant learning. Task-based functional MRI (tb-fMRI) paired with operant learning revealed dorsal hippocampal hyperactivation during the Nogo task in male NBN-TeTX mice, suggesting that hippocampal hyperexcitability might underlie the observed behavioral deficits. Additionally, resting-state fMRI (rs-fMRI) exhibited enhanced functional connectivity between the dorsal and ventral dentate gyrus following NBN silencing. Further investigations into the activities of PV+ interneurons and mossy cells highlighted the indispensability of NBNs in maintaining the hippocampal excitation/inhibition balance. Our findings emphasize that the neural plasticity driven by NBNs extensively modulates the hippocampus, sculpting inhibitory control and cognitive flexibility.
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Affiliation(s)
- Haowei Li
- Department of Integrated Biosciences, Graduate School of Frontier Sciences, The University of Tokyo, Kashiwa, Japan
| | - Risako Tamura
- Department of Integrated Biosciences, Graduate School of Frontier Sciences, The University of Tokyo, Kashiwa, Japan
| | - Daiki Hayashi
- Department of Integrated Biosciences, Graduate School of Frontier Sciences, The University of Tokyo, Kashiwa, Japan
| | - Hirotaka Asai
- Department of Integrated Biosciences, Graduate School of Frontier Sciences, The University of Tokyo, Kashiwa, Japan
| | - Junya Koga
- Department of Integrated Biosciences, Graduate School of Frontier Sciences, The University of Tokyo, Kashiwa, Japan
| | - Shota Ando
- Department of Integrated Biosciences, Graduate School of Frontier Sciences, The University of Tokyo, Kashiwa, Japan
| | - Sayumi Yokota
- Department of Integrated Biosciences, Graduate School of Frontier Sciences, The University of Tokyo, Kashiwa, Japan
| | - Jun Kaneko
- Department of Integrated Biosciences, Graduate School of Frontier Sciences, The University of Tokyo, Kashiwa, Japan
| | - Keisuke Sakurai
- Department of Integrated Biosciences, Graduate School of Frontier Sciences, The University of Tokyo, Kashiwa, Japan
| | - Akira Sumiyoshi
- Department of Molecular Imaging and Theranostics, National Institutes for Quantum and Radiological Science and Technology, Chiba, Japan
| | - Tadashi Yamamoto
- Okinawa Institute of Science and Technology Graduate University, Okinawa, Japan
| | - Keigo Hikishima
- Okinawa Institute of Science and Technology Graduate University, Okinawa, Japan
| | - Kazumasa Z. Tanaka
- Okinawa Institute of Science and Technology Graduate University, Okinawa, Japan
- Laboratory for Circuit and Behavioral Physiology, RIKEN Center for Brain Science, Saitama, Japan
| | - Thomas J. McHugh
- Laboratory for Circuit and Behavioral Physiology, RIKEN Center for Brain Science, Saitama, Japan
| | - Tatsuhiro Hisatsune
- Department of Integrated Biosciences, Graduate School of Frontier Sciences, The University of Tokyo, Kashiwa, Japan
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6
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Tuncdemir SN, Grosmark AD, Chung H, Luna VM, Lacefield CO, Losonczy A, Hen R. Adult-born granule cells facilitate remapping of spatial and non-spatial representations in the dentate gyrus. Neuron 2023; 111:4024-4039.e7. [PMID: 37820723 PMCID: PMC10841867 DOI: 10.1016/j.neuron.2023.09.016] [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: 12/07/2022] [Revised: 06/10/2023] [Accepted: 09/13/2023] [Indexed: 10/13/2023]
Abstract
Adult-born granule cells (abGCs) have been implicated in memory discrimination through a neural computation known as pattern separation. Here, using in vivo Ca2+ imaging, we examined how chronic ablation or acute chemogenetic silencing of abGCs affects the activity of mature granule cells (mGCs). In both cases, we observed altered remapping of mGCs. Rather than broadly modulating the activity of all mGCs, abGCs promote the remapping of place cells' firing fields while increasing rate remapping of mGCs that represent sensory cues. In turn, these remapping deficits are associated with behavioral impairments in animals' ability to correctly identify new goal locations. Thus, abGCs facilitate pattern separation through the formation of non-overlapping representations for identical sensory cues encountered in different locations. In the absence of abGCs, the dentate gyrus shifts to a state that is dominated by cue information, a situation that is consistent with the overgeneralization often observed in anxiety or age-related disorders.
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Affiliation(s)
- Sebnem N Tuncdemir
- Departments of Psychiatry and Neuroscience, Columbia University, New York, NY 10032, USA; Division of Systems Neuroscience, New York State Psychiatric Institute, New York, NY 10032, USA
| | - Andres D Grosmark
- Department of Neuroscience, Mortimer B. Zuckerman Mind Brain Behavior Institute, Columbia University, New York, NY 10027, USA
| | - Hannah Chung
- Division of Systems Neuroscience, New York State Psychiatric Institute, New York, NY 10032, USA
| | - Victor M Luna
- Departments of Psychiatry and Neuroscience, Columbia University, New York, NY 10032, USA; Division of Systems Neuroscience, New York State Psychiatric Institute, New York, NY 10032, USA
| | - Clay O Lacefield
- Departments of Psychiatry and Neuroscience, Columbia University, New York, NY 10032, USA; Division of Systems Neuroscience, New York State Psychiatric Institute, New York, NY 10032, USA
| | - Attila Losonczy
- Department of Neuroscience, Mortimer B. Zuckerman Mind Brain Behavior Institute, Columbia University, New York, NY 10027, USA
| | - Rene Hen
- Departments of Psychiatry and Neuroscience, Columbia University, New York, NY 10032, USA; Division of Systems Neuroscience, New York State Psychiatric Institute, New York, NY 10032, USA.
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7
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Santiago RM, Lopes-dos-Santos V, Jones EAA, Huang Y, Dupret D, Tort AB. Waveform-based classification of dentate spikes. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.10.24.563826. [PMID: 37961150 PMCID: PMC10634814 DOI: 10.1101/2023.10.24.563826] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/15/2023]
Abstract
Synchronous excitatory discharges from the entorhinal cortex (EC) to the dentate gyrus (DG) generate fast and prominent patterns in the hilar local field potential (LFP), called dentate spikes (DSs). As sharp-wave ripples in CA1, DSs are more likely to occur in quiet behavioral states, when memory consolidation is thought to take place. However, their functions in mnemonic processes are yet to be elucidated. The classification of DSs into types 1 or 2 is determined by their origin in the lateral or medial EC, as revealed by current source density (CSD) analysis, which requires recordings from linear probes with multiple electrodes spanning the DG layers. To allow the investigation of the functional role of each DS type in recordings obtained from single electrodes and tetrodes, which are abundant in the field, we developed an unsupervised method using Gaussian mixture models to classify such events based on their waveforms. Our classification approach achieved high accuracies (> 80%) when validated in 8 mice with DG laminar profiles. The average CSDs, waveforms, rates, and widths of the DS types obtained through our method closely resembled those derived from the CSD-based classification. As an example of application, we used the technique to analyze single-electrode LFPs from apolipoprotein (apo) E3 and apoE4 knock-in mice. We observed that the latter group, which is a model for Alzheimer's disease, exhibited wider DSs of both types from a young age, with a larger effect size for DS type 2, likely reflecting early pathophysiological alterations in the EC-DG network, such as hyperactivity. In addition to the applicability of the method in expanding the study of DS types, our results show that their waveforms carry information about their origins, suggesting different underlying network dynamics and roles in memory processing.
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Affiliation(s)
- Rodrigo M.M. Santiago
- Computational Neurophysiology Lab, Brain Institute, Federal University of Rio Grande do Norte, Natal, RN, 59078-900, Brazil
| | - Vítor Lopes-dos-Santos
- Medical Research Council Brain Network Dynamics Unit, Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, UK
| | - Emily A. Aery Jones
- Department of Neurobiology, Stanford University School of Medicine, Stanford, CA, 94305, USA
| | - Yadong Huang
- Gladstone Institute of Neurological Disease, Gladstone Institutes, San Francisco, CA 94158, USA
| | - David Dupret
- Medical Research Council Brain Network Dynamics Unit, Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, UK
| | - Adriano B.L. Tort
- Computational Neurophysiology Lab, Brain Institute, Federal University of Rio Grande do Norte, Natal, RN, 59078-900, Brazil
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8
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Meyers KT, Damphousse CC, Ozols AB, Campbell JM, Newbern JM, Hu C, Marrone DF, Gallitano AL. Serial electroconvulsive Seizure alters dendritic complexity and promotes cellular proliferation in the mouse dentate gyrus; a role for Egr3. Brain Stimul 2023; 16:889-900. [PMID: 37146791 PMCID: PMC10776161 DOI: 10.1016/j.brs.2023.04.022] [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: 01/18/2023] [Revised: 04/19/2023] [Accepted: 04/25/2023] [Indexed: 05/07/2023] Open
Abstract
BACKGROUND Despite being one of the safest, most effective treatments for severe mood disorders, the therapeutic mechanisms of electroconvulsive therapy remain unknown. Electroconvulsive seizure (ECS) induces rapid, high-level expression of immediate early genes (IEGs) and brain-derived neurotrophic factor (BDNF), in addition to stimulation of neurogenesis and dendritic remodeling of dentate gyrus (DG) neurons. We have previously shown that this upregulation of BDNF fails to occur in the hippocampus of mice lacking the IEG Egr3. Since BDNF influences neurogenesis and dendritic remodeling, we hypothesized that Egr3-/- mice will exhibit deficits in neurogenesis and dendritic remodeling in response to ECS. OBJECTIVE To test this hypothesis, we examined dendritic remodeling and cellular proliferation in the DG of Egr3-/- and wild-type mice following repeated ECS. METHODS Mice received 10 daily ECSs. Dendritic morphology was examined in Golgi-Cox-stained tissue and cellular proliferation was analyzed through bromodeoxyuridine (BrdU) immunohistochemistry and confocal imaging. RESULTS Serial ECS in mice results in dendritic remodeling, increased spine density, and cellular proliferation in the DG. Loss of Egr3 alters the dendritic remodeling induced by serial ECS but does not change the number of dendritic spines or cellular proliferation consequences of ECS. CONCLUSION Egr3 influences the dendritic remodeling induced by ECS but is not required for ECS-induced proliferation of hippocampal DG cells.
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Affiliation(s)
- K T Meyers
- Interdisciplinary Graduate Program in Neuroscience, Arizona State University, Tempe, AZ, 85281, USA; Basic Medical Sciences, University of Arizona College of Medicine - Phoenix, Phoenix, AZ, 85004, USA
| | - C C Damphousse
- Psychology, Wilfrid Laurier University, Waterloo, ON, N2L 3C5, Canada
| | - A B Ozols
- Basic Medical Sciences, University of Arizona College of Medicine - Phoenix, Phoenix, AZ, 85004, USA
| | - J M Campbell
- Basic Medical Sciences, University of Arizona College of Medicine - Phoenix, Phoenix, AZ, 85004, USA
| | - J M Newbern
- School of Life Sciences, Arizona State University, Tempe, AZ, 85287, USA
| | - C Hu
- Epidemiology and Biostatistics, University of Arizona Mel and Enid Zuckerman College of Public Health - Phoenix, 714 E Van Buren St #119, Phoenix, AZ, 85006, USA
| | - D F Marrone
- Psychology, Wilfrid Laurier University, Waterloo, ON, N2L 3C5, Canada.
| | - A L Gallitano
- Basic Medical Sciences, University of Arizona College of Medicine - Phoenix, Phoenix, AZ, 85004, USA.
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9
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Ash AM, Regele-Blasco E, Seib DR, Chahley E, Skelton PD, Luikart BW, Snyder JS. Adult-born neurons inhibit developmentally-born neurons during spatial learning. Neurobiol Learn Mem 2023; 198:107710. [PMID: 36572174 DOI: 10.1016/j.nlm.2022.107710] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2022] [Revised: 12/20/2022] [Accepted: 12/21/2022] [Indexed: 12/24/2022]
Abstract
Ongoing neurogenesis in the dentate gyrus (DG) subregion of the hippocampus results in a heterogenous population of neurons. Immature adult-born neurons (ABNs) have physiological and anatomical properties that may give them a unique role in learning. For example, compared to older granule neurons, they have greater somatic excitability, which could facilitate their recruitment into memory traces. However, recruitment is also likely to depend on interactions with other DG neurons through processes such as lateral inhibition. Immature ABNs target inhibitory interneurons and, compared to older neurons, they receive less GABAergic inhibition. Thus, they may induce lateral inhibition of mature DG neurons while being less susceptible to inhibition themselves. To test this we used a chemogenetic approach to silence immature ABNs as rats learned a spatial water maze task, and measured activity (Fos expression) in ABNs and developmentally-born neurons (DBNs). A retrovirus expressing the inhibitory DREADD receptor, hM4Di, was injected into the dorsal DG of male rats at 6w to infect neurons born in adulthood. Animals were also injected with BrdU to label DBNs or ABNs. DBNs were significantly more active than immature 4-week-old ABNs. Silencing 4-week-old ABNs did not alter learning but it increased activity in DBNs. However, silencing ABNs did not affect activation in other ABNs within the DG. Silencing ABNs also did not alter Fos expression in parvalbumin- and somatostatin-expressing interneurons. Collectively, these results suggest that ABNs may directly inhibit DBN activity during hippocampal-dependent learning, which may be relevant for maintaining sparse hippocampal representations of experienced events.
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Affiliation(s)
- Alyssa M Ash
- Department of Psychology, Djavad Mowafaghian Centre for Brain Health, University of British Columbia, Vancouver, BC, Canada
| | - Elena Regele-Blasco
- Department of Psychology, Djavad Mowafaghian Centre for Brain Health, University of British Columbia, Vancouver, BC, Canada
| | - Désirée R Seib
- Department of Psychology, Djavad Mowafaghian Centre for Brain Health, University of British Columbia, Vancouver, BC, Canada
| | - Erin Chahley
- Department of Psychology, Djavad Mowafaghian Centre for Brain Health, University of British Columbia, Vancouver, BC, Canada
| | - Patrick D Skelton
- Department of Molecular and Systems Biology, Geisel School of Medicine at Dartmouth, Hanover, NH, United States
| | - Bryan W Luikart
- Department of Molecular and Systems Biology, Geisel School of Medicine at Dartmouth, Hanover, NH, United States
| | - Jason S Snyder
- Department of Psychology, Djavad Mowafaghian Centre for Brain Health, University of British Columbia, Vancouver, BC, Canada.
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10
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Adult-born dentate granule cells promote hippocampal population sparsity. Nat Neurosci 2022; 25:1481-1491. [PMID: 36216999 PMCID: PMC9630129 DOI: 10.1038/s41593-022-01176-5] [Citation(s) in RCA: 29] [Impact Index Per Article: 14.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2021] [Accepted: 09/01/2022] [Indexed: 01/13/2023]
Abstract
The dentate gyrus (DG) gates neocortical information flow to the hippocampus. Intriguingly, the DG also produces adult-born dentate granule cells (abDGCs) throughout the lifespan, but their contribution to downstream firing dynamics remains unclear. Here, we show that abDGCs promote sparser hippocampal population spiking during mnemonic processing of novel stimuli. By combining triple-(DG-CA3-CA1) ensemble recordings and optogenetic interventions in behaving mice, we show that abDGCs constitute a subset of high-firing-rate neurons with enhanced activity responses to novelty and strong modulation by theta oscillations. Selectively activating abDGCs in their 4-7-week post-birth period increases sparsity of hippocampal population patterns, whereas suppressing abDGCs reduces this sparsity, increases principal cell firing rates and impairs novel object recognition with reduced dimensionality of the network firing structure, without affecting single-neuron spatial representations. We propose that adult-born granule cells transiently support sparser hippocampal population activity structure for higher-dimensional responses relevant to effective mnemonic information processing.
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11
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Li S, Zhou Q, Liu E, Du H, Yu N, Yu H, Wang W, Li M, Weng Y, Gao Y, Pi G, Wang X, Ke D, Wang J. Alzheimer-like tau accumulation in dentate gyrus mossy cells induces spatial cognitive deficits by disrupting multiple memory-related signaling and inhibiting local neural circuit. Aging Cell 2022; 21:e13600. [PMID: 35355405 PMCID: PMC9124302 DOI: 10.1111/acel.13600] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2022] [Revised: 02/28/2022] [Accepted: 03/14/2022] [Indexed: 12/22/2022] Open
Abstract
Abnormal tau accumulation and spatial memory loss constitute characteristic pathology and symptoms of Alzheimer disease (AD). Yet, the intrinsic connections and the mechanism between them are not fully understood. In the current study, we observed a prominent accumulation of the AD‐like hyperphosphorylated and truncated tau (hTau N368) proteins in hippocampal dentate gyrus (DG) mossy cells of 3xTg‐AD mice. Further investigation demonstrated that the ventral DG (vDG) mossy cell‐specific overexpressing hTau for 3 months induced spatial cognitive deficits, while expressing hTau N368 for only 1 month caused remarkable spatial cognitive impairment with more prominent tau pathologies. By in vivo electrophysiological and optic fiber recording, we observed that the vDG mossy cell‐specific overexpression of hTau N368 disrupted theta oscillations with local neural network inactivation in the dorsal DG subset, suggesting impairment of the ventral to dorsal neural circuit. The mossy cell‐specific transcriptomic data revealed that multiple AD‐associated signaling pathways were disrupted by hTau N368, including reduction of synapse‐associated proteins, inhibition of AKT and activation of glycogen synthase kinase‐3β. Importantly, chemogenetic activating mossy cells efficiently attenuated the hTau N368‐induced spatial cognitive deficits. Together, our findings indicate that the mossy cell pathological tau accumulation could induce the AD‐like spatial memory deficit by inhibiting the local neural network activity, which not only reveals new pathogenesis underlying the mossy cell‐related spatial memory loss but also provides a mouse model of Mossy cell‐specific hTau accumulation for drug development in AD and the related tauopathies.
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Affiliation(s)
- Shihong Li
- Department of Pathophysiology School of Basic Medicine Key Laboratory of Education Ministry of China/Hubei Province for Neurological Disorders Tongji Medical College Huazhong University of Science and Technology Wuhan China
| | - Qiuzhi Zhou
- Department of Pathophysiology School of Basic Medicine Key Laboratory of Education Ministry of China/Hubei Province for Neurological Disorders Tongji Medical College Huazhong University of Science and Technology Wuhan China
| | - Enjie Liu
- Department of Pathology The First Affiliated Hospital of Zhengzhou University Zhengzhou China
| | - Huiyun Du
- Department of Physiology School of Basic Medicine and Tongji Medical College Huazhong University of Science and Technology Wuhan China
| | - Nana Yu
- Department of Pathophysiology School of Basic Medicine Key Laboratory of Education Ministry of China/Hubei Province for Neurological Disorders Tongji Medical College Huazhong University of Science and Technology Wuhan China
| | - Haitao Yu
- Department of Pathophysiology School of Basic Medicine Key Laboratory of Education Ministry of China/Hubei Province for Neurological Disorders Tongji Medical College Huazhong University of Science and Technology Wuhan China
| | - Weijin Wang
- Department of Pathophysiology School of Basic Medicine Key Laboratory of Education Ministry of China/Hubei Province for Neurological Disorders Tongji Medical College Huazhong University of Science and Technology Wuhan China
| | - Mengzhu Li
- Department of Pathophysiology School of Basic Medicine Key Laboratory of Education Ministry of China/Hubei Province for Neurological Disorders Tongji Medical College Huazhong University of Science and Technology Wuhan China
| | - Ying Weng
- Department of Pathophysiology School of Basic Medicine Key Laboratory of Education Ministry of China/Hubei Province for Neurological Disorders Tongji Medical College Huazhong University of Science and Technology Wuhan China
| | - Yang Gao
- Department of Pathophysiology School of Basic Medicine Key Laboratory of Education Ministry of China/Hubei Province for Neurological Disorders Tongji Medical College Huazhong University of Science and Technology Wuhan China
| | - Guilin Pi
- Department of Pathophysiology School of Basic Medicine Key Laboratory of Education Ministry of China/Hubei Province for Neurological Disorders Tongji Medical College Huazhong University of Science and Technology Wuhan China
| | - Xin Wang
- Department of Pathophysiology School of Basic Medicine Key Laboratory of Education Ministry of China/Hubei Province for Neurological Disorders Tongji Medical College Huazhong University of Science and Technology Wuhan China
| | - Dan Ke
- Department of Pathophysiology School of Basic Medicine Key Laboratory of Education Ministry of China/Hubei Province for Neurological Disorders Tongji Medical College Huazhong University of Science and Technology Wuhan China
| | - Jian‐Zhi Wang
- Department of Pathophysiology School of Basic Medicine Key Laboratory of Education Ministry of China/Hubei Province for Neurological Disorders Tongji Medical College Huazhong University of Science and Technology Wuhan China
- Co‐Innovation Center of Neuroregeneration Nantong University Nantong China
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12
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Ramsden CE, Keyes GS, Calzada E, Horowitz MS, Zamora D, Jahanipour J, Sedlock A, Indig FE, Moaddel R, Kapogiannis D, Maric D. Lipid Peroxidation Induced ApoE Receptor-Ligand Disruption as a Unifying Hypothesis Underlying Sporadic Alzheimer's Disease in Humans. J Alzheimers Dis 2022; 87:1251-1290. [PMID: 35466940 DOI: 10.3233/jad-220071] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
BACKGROUND Sporadic Alzheimer's disease (sAD) lacks a unifying hypothesis that can account for the lipid peroxidation observed early in the disease, enrichment of ApoE in the core of neuritic plaques, hallmark plaques and tangles, and selective vulnerability of entorhinal-hippocampal structures. OBJECTIVE We hypothesized that 1) high expression of ApoER2 (receptor for ApoE and Reelin) helps explain this anatomical vulnerability; 2) lipid peroxidation of ApoE and ApoER2 contributes to sAD pathogenesis, by disrupting neuronal ApoE delivery and Reelin-ApoER2-Dab1 signaling cascades. METHODS In vitro biochemical experiments; Single-marker and multiplex fluorescence-immunohistochemistry (IHC) in postmortem specimens from 26 individuals who died cognitively normal, with mild cognitive impairment or with sAD. RESULTS ApoE and ApoER2 peptides and proteins were susceptible to attack by reactive lipid aldehydes, generating lipid-protein adducts and crosslinked ApoE-ApoER2 complexes. Using in situ hybridization alongside IHC, we observed that: 1) ApoER2 is strongly expressed in terminal zones of the entorhinal-hippocampal 'perforant path' projections that underlie memory; 2) ApoE, lipid aldehyde-modified ApoE, Reelin, ApoER2, and the downstream Reelin-ApoER2 cascade components Dab1 and Thr19-phosphorylated PSD95 accumulated in the vicinity of neuritic plaques in perforant path terminal zones in sAD cases; 3) several ApoE/Reelin-ApoER2-Dab1 pathway markers were higher in sAD cases and positively correlated with histological progression and cognitive deficits. CONCLUSION Results demonstrate derangements in multiple ApoE/Reelin-ApoER2-Dab1 axis components in perforant path terminal zones in sAD and provide proof-of-concept that ApoE and ApoER2 are vulnerable to aldehyde-induced adduction and crosslinking. Findings provide the foundation for a unifying hypothesis implicating lipid peroxidation of ApoE and ApoE receptors in sAD.
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Affiliation(s)
- Christopher E Ramsden
- Lipid Peroxidation Unit, Laboratory of Clinical Investigation, National Institute on Aging, NIH, Baltimore, MD, USA.,Intramural Program of the National Institute on Alcohol Abuse and Alcoholism, NIH, Bethesda, MD, USA
| | - Gregory S Keyes
- Lipid Peroxidation Unit, Laboratory of Clinical Investigation, National Institute on Aging, NIH, Baltimore, MD, USA
| | - Elizabeth Calzada
- Lipid Peroxidation Unit, Laboratory of Clinical Investigation, National Institute on Aging, NIH, Baltimore, MD, USA
| | - Mark S Horowitz
- Lipid Peroxidation Unit, Laboratory of Clinical Investigation, National Institute on Aging, NIH, Baltimore, MD, USA
| | - Daisy Zamora
- Lipid Peroxidation Unit, Laboratory of Clinical Investigation, National Institute on Aging, NIH, Baltimore, MD, USA
| | - Jahandar Jahanipour
- Flow and Imaging Cytometry Core Facility, National Institute of Neurological Disorders and Stroke, NIH, Bethesda, MD, USA
| | - Andrea Sedlock
- Flow and Imaging Cytometry Core Facility, National Institute of Neurological Disorders and Stroke, NIH, Bethesda, MD, USA
| | - Fred E Indig
- Confocal Imaging Facility, National Institute on Aging Intramural Research Program, NIH, Baltimore, MD, USA
| | - Ruin Moaddel
- Laboratory of Clinical Investigation, National Institute on Aging, NIH, Baltimore, MD, USA
| | - Dimitrios Kapogiannis
- Human Neuroscience Unit, Laboratory of Clinical Investigation, National Institute on Aging, NIH, Baltimore, MD, USA
| | - Dragan Maric
- Flow and Imaging Cytometry Core Facility, National Institute of Neurological Disorders and Stroke, NIH, Bethesda, MD, USA
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13
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GoodSmith D, Kim SH, Puliyadi V, Ming GL, Song H, Knierim JJ, Christian KM. Flexible encoding of objects and space in single cells of the dentate gyrus. Curr Biol 2022; 32:1088-1101.e5. [PMID: 35108522 PMCID: PMC8930604 DOI: 10.1016/j.cub.2022.01.023] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2021] [Revised: 11/12/2021] [Accepted: 01/10/2022] [Indexed: 01/05/2023]
Abstract
The hippocampus is involved in the formation of memories that require associations among stimuli to construct representations of space and the items and events within that space. Neurons in the dentate gyrus (DG), an initial input region of the hippocampus, have robust spatial tuning, but it is unclear how nonspatial information may be integrated with spatial activity in this region. We recorded from the DG of 21 adult mice as they foraged for food in an environment that contained discrete objects. We found DG cells with multiple firing fields at a fixed distance and direction from objects (landmark vector cells) and cells that exhibited localized changes in spatial firing when objects in the environment were manipulated. By classifying recorded DG cells into putative dentate granule cells and mossy cells, we examined how the addition or displacement of objects affected the spatial firing of these DG cell types. Object-related activity was detected in a significant proportion of mossy cells. Although few granule cells with responses to object manipulations were recorded, likely because of the sparse nature of granule cell firing, there was generally no significant difference in the proportion of granule cells and mossy cells with object responses. When mice explored a second environment with the same objects, DG spatial maps completely reorganized, and a different subset of cells responded to object manipulations. Together, these data reveal the capacity of DG cells to detect small changes in the environment while preserving a stable spatial representation of the overall context.
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Affiliation(s)
- Douglas GoodSmith
- Department of Neuroscience and Mahoney Institute for Neurosciences, Perelman School of Medicine, University of Pennsylvania, 3400 Civic Center Boulevard, Philadelphia, PA 19104, USA; Zanvyl Krieger Mind/Brain Institute, Johns Hopkins University, 3400 N Charles Street, Baltimore, MD 21218, USA; The Solomon H. Snyder Department of Neuroscience, Johns Hopkins University School of Medicine, 733 N Broadway, Baltimore, MD 21205, USA; Department of Neurobiology and Neuroscience Institute, University of Chicago, 5801 S Ellis Avenue, Chicago, IL 60637, USA
| | - Sang Hoon Kim
- Department of Neuroscience and Mahoney Institute for Neurosciences, Perelman School of Medicine, University of Pennsylvania, 3400 Civic Center Boulevard, Philadelphia, PA 19104, USA
| | - Vyash Puliyadi
- Department of Psychological and Brain Sciences, Johns Hopkins University, 3400 N Charles Street, Baltimore, MD 21218, USA; Zanvyl Krieger Mind/Brain Institute, Johns Hopkins University, 3400 N Charles Street, Baltimore, MD 21218, USA
| | - Guo-Li Ming
- Department of Neuroscience and Mahoney Institute for Neurosciences, Perelman School of Medicine, University of Pennsylvania, 3400 Civic Center Boulevard, Philadelphia, PA 19104, USA; Department of Cell and Developmental Biology, Perelman School of Medicine, University of Pennsylvania, 3400 Civic Center Boulevard, Philadelphia, PA 19104, USA; Institute for Regenerative Medicine, Perelman School of Medicine, University of Pennsylvania, 3400 Civic Center Boulevard, Philadelphia, PA 19104, USA; Department of Psychiatry, Perelman School of Medicine, University of Pennsylvania, 3400 Civic Center Boulevard, Philadelphia, PA 19104, USA
| | - Hongjun Song
- Department of Neuroscience and Mahoney Institute for Neurosciences, Perelman School of Medicine, University of Pennsylvania, 3400 Civic Center Boulevard, Philadelphia, PA 19104, USA; Department of Cell and Developmental Biology, Perelman School of Medicine, University of Pennsylvania, 3400 Civic Center Boulevard, Philadelphia, PA 19104, USA; Institute for Regenerative Medicine, Perelman School of Medicine, University of Pennsylvania, 3400 Civic Center Boulevard, Philadelphia, PA 19104, USA; The Epigenetics Institute, Perelman School of Medicine, University of Pennsylvania, 3400 Civic Center Boulevard, Philadelphia, PA 19104, USA.
| | - James J Knierim
- Zanvyl Krieger Mind/Brain Institute, Johns Hopkins University, 3400 N Charles Street, Baltimore, MD 21218, USA; The Solomon H. Snyder Department of Neuroscience, Johns Hopkins University School of Medicine, 733 N Broadway, Baltimore, MD 21205, USA; Kavli Neuroscience Discovery Institute, Johns Hopkins University School of Medicine, 733 N Broadway, Baltimore, MD 21205, USA.
| | - Kimberly M Christian
- Department of Neuroscience and Mahoney Institute for Neurosciences, Perelman School of Medicine, University of Pennsylvania, 3400 Civic Center Boulevard, Philadelphia, PA 19104, USA.
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14
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Di Castro MA, Volterra A. Astrocyte control of the entorhinal cortex-dentate gyrus circuit: Relevance to cognitive processing and impairment in pathology. Glia 2021; 70:1536-1553. [PMID: 34904753 PMCID: PMC9299993 DOI: 10.1002/glia.24128] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2021] [Revised: 11/28/2021] [Accepted: 11/30/2021] [Indexed: 12/20/2022]
Abstract
The entorhinal cortex-dentate gyrus circuit is centrally involved in memory processing conveying to the hippocampus spatial and nonspatial context information via, respectively, medial and lateral perforant path (MPP and LPP) excitatory projections onto dentate granule cells (GCs). Here, we review work of several years from our group showing that astrocytes sense local synaptic transmission and exert in turn a presynaptic control at PP-GC synapses. Modulation of neurotransmitter release probability by astrocytes sets basal synaptic strength and dynamic range for long-term potentiation of PP-GC synapses. Intriguingly, this astrocyte control is circuit-specific, being present only at MPP-GC (not LPP-GC) synapses, which selectively express atypical presynaptic N-methyl-D-aspartate receptors (NMDAR) suitable to activation by astrocyte-released glutamate. Moreover, the astrocytic control is peculiarly dependent on the cytokine TNFα, which at constitutive levels acts as a gating factor for the astrocyte signaling. During inflammation/infection processes, increased levels of TNFα lead to uncontrolled astrocyte glutamate release, altered PP-GC circuit processing and, ultimately, impaired contextual memory performance. The TNFα-dependent pathological switch of the synaptic control from astrocytes and its deleterious consequences are observed in animal models of HIV brain infection and multiple sclerosis, conditions both known to cause cognitive disturbances in up to 50% of patients. The review also discusses open issues related to the identified astrocytic pathway: its role in contextual memory processing, potential damaging role in Alzheimer's disease, the existence of vesicular glutamate release from DG astrocytes, and the possible synaptic-like connectivity between astrocytic output sites and PP receptive sites.
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Affiliation(s)
- Maria Amalia Di Castro
- Department of Fundamental Neuroscience, University of Lausanne, Lausanne, Switzerland.,Department of Physiology and Pharmacology, Sapienza University of Rome, Rome, Italy
| | - Andrea Volterra
- Department of Fundamental Neuroscience, University of Lausanne, Lausanne, Switzerland
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15
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Kwon O, Yang H, Kim SC, Kim J, Sim J, Lee J, Hwang EM, Shim S, Park JY. TWIK-1 BAC-GFP Transgenic Mice, an Animal Model for TWIK-1 Expression. Cells 2021; 10:cells10102751. [PMID: 34685731 PMCID: PMC8534699 DOI: 10.3390/cells10102751] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2021] [Revised: 09/26/2021] [Accepted: 10/11/2021] [Indexed: 12/15/2022] Open
Abstract
TWIK-1 is the first identified member of the two-pore domain potassium (K2P) channels that are involved in neuronal excitability and astrocytic passive conductance in the brain. Despite the physiological roles of TWIK-1, there is still a lack of information on the basic expression patterns of TWIK-1 proteins in the brain. Here, using a modified bacterial artificial chromosome (BAC), we generated a transgenic mouse (Tg mouse) line expressing green fluorescent protein (GFP) under the control of the TWIK-1 promoter (TWIK-1 BAC-GFP Tg mice). We confirmed that nearly all GFP-producing cells co-expressed endogenous TWIK-1 in the brain of TWIK-1 BAC-GFP Tg mice. GFP signals were highly expressed in various brain areas, including the dentate gyrus (DG), lateral entorhinal cortex (LEC), and cerebellum (Cb). In addition, we found that GFP signals were highly expressed in immature granule cells in the DG. Finally, our TWIK-1 BAC-GFP Tg mice mimic the upregulation of TWIK-1 mRNA expression in the hippocampus following the injection of kainic acid (KA). Our data clearly showed that TWIK-1 BAC-GFP Tg mice are a useful animal model for studying the mechanisms regulating TWIK-1 gene expression and the physiological roles of TWIK-1 channels in the brain.
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Affiliation(s)
- Osung Kwon
- Department of Integrated Biomedical and Life Science, Graduate School, Jiyoun Lee Korea University, Seoul 02841, Korea; (O.K.); (S.-C.K.); (J.K.); (J.S.); (J.L.)
| | - Hayoung Yang
- Department of Biochemistry, Chungbuk National University, Cheongju 28644, Korea;
| | - Seung-Chan Kim
- Department of Integrated Biomedical and Life Science, Graduate School, Jiyoun Lee Korea University, Seoul 02841, Korea; (O.K.); (S.-C.K.); (J.K.); (J.S.); (J.L.)
- Center for Functional Connectomics, Korea Institute of Science and Technology (KIST), Seoul 02792, Korea;
| | - Juhyun Kim
- Department of Integrated Biomedical and Life Science, Graduate School, Jiyoun Lee Korea University, Seoul 02841, Korea; (O.K.); (S.-C.K.); (J.K.); (J.S.); (J.L.)
- BK21FOUR R&E Center for Learning Health Systems, Korea University, Seoul 02841, Korea
| | - Jaewon Sim
- Department of Integrated Biomedical and Life Science, Graduate School, Jiyoun Lee Korea University, Seoul 02841, Korea; (O.K.); (S.-C.K.); (J.K.); (J.S.); (J.L.)
| | - Jiyoun Lee
- Department of Integrated Biomedical and Life Science, Graduate School, Jiyoun Lee Korea University, Seoul 02841, Korea; (O.K.); (S.-C.K.); (J.K.); (J.S.); (J.L.)
- BK21FOUR R&E Center for Learning Health Systems, Korea University, Seoul 02841, Korea
| | - Eun-Mi Hwang
- Center for Functional Connectomics, Korea Institute of Science and Technology (KIST), Seoul 02792, Korea;
| | - Sungbo Shim
- Department of Biochemistry, Chungbuk National University, Cheongju 28644, Korea;
- Correspondence: (S.S.); (J.-Y.P.)
| | - Jae-Yong Park
- Department of Integrated Biomedical and Life Science, Graduate School, Jiyoun Lee Korea University, Seoul 02841, Korea; (O.K.); (S.-C.K.); (J.K.); (J.S.); (J.L.)
- Correspondence: (S.S.); (J.-Y.P.)
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16
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Sparsification of AP firing in adult-born hippocampal granule cells via voltage-dependent α5-GABA A receptors. Cell Rep 2021; 37:109768. [PMID: 34610304 DOI: 10.1016/j.celrep.2021.109768] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2020] [Revised: 07/07/2021] [Accepted: 09/08/2021] [Indexed: 11/21/2022] Open
Abstract
GABA can depolarize immature neurons close to the action potential (AP) threshold in development and adult neurogenesis. Nevertheless, GABAergic synapses effectively inhibit AP firing in newborn granule cells of the adult hippocampus as early as two weeks post-mitosis. The underlying mechanisms are largely unclear. Here, we analyze GABAergic inputs in newborn hippocampal granule cells mediated by soma-targeting parvalbumin and dendrite-targeting somatostatin interneurons. Surprisingly, both interneuron subtypes activate α5-subunit-containing GABAA receptors (α5-GABAARs) in young neurons, showing a nonlinear voltage dependence with increasing conductance around the AP threshold. By contrast, in mature cells, parvalbumin interneurons mediate linear GABAergic synaptic currents lacking α5-subunits, while somatostatin interneurons continue to target nonlinear α5-GABAARs. Computational modeling shows that the voltage-dependent amplification of α5-GABAAR opening in young neurons is crucial for inhibition of AP firing to generate balanced and sparse firing activity, even with depolarized GABA reversal potential.
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17
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Oulé M, Atucha E, Wells TM, Macharadze T, Sauvage MM, Kreutz MR, Lopez-Rojas J. Dendritic Kv4.2 potassium channels selectively mediate spatial pattern separation in the dentate gyrus. iScience 2021; 24:102876. [PMID: 34386734 PMCID: PMC8346659 DOI: 10.1016/j.isci.2021.102876] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2021] [Revised: 04/22/2021] [Accepted: 07/14/2021] [Indexed: 11/23/2022] Open
Abstract
The capacity to distinguish comparable experiences is fundamental for the recall of similar memories and has been proposed to require pattern separation in the dentate gyrus (DG). However, the cellular mechanisms by which mature granule cells (GCs) of the DG accomplish this function are poorly characterized. Here, we show that Kv4.2 channels selectively modulate the excitability of medial dendrites of dentate GCs. These dendrites are targeted by the medial entorhinal cortex, the main source of spatial inputs to the DG. Accordingly, we found that the spatial pattern separation capability of animals lacking the Kv4.2 channel is significantly impaired. This points to the role of intrinsic excitability in supporting the mnemonic function of the dentate and to the Kv4.2 channel as a candidate substrate promoting spatial pattern separation.
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Affiliation(s)
- Marie Oulé
- Research Group Neuroplasticity, Leibniz Institute for Neurobiology, 39118 Magdeburg, Germany
| | - Erika Atucha
- Functional Architecture of Memory Department, Leibniz Institute for Neurobiology, 39118 Magdeburg, Germany
| | - Tenyse M. Wells
- Functional Architecture of Memory Department, Leibniz Institute for Neurobiology, 39118 Magdeburg, Germany
| | - Tamar Macharadze
- Research Group Neuroplasticity, Leibniz Institute for Neurobiology, 39118 Magdeburg, Germany
- Department of Anesthesiology and Intensive Care Medicine, Otto-von-Guericke-University, 39120 Magdeburg, Germany
| | - Magdalena M. Sauvage
- Functional Architecture of Memory Department, Leibniz Institute for Neurobiology, 39118 Magdeburg, Germany
- Otto von Guericke University, Medical Faculty, Functional Neuroplasticity Department, 39120, Magdeburg, Germany
- Center for Behavioral Brain Sciences (CBBS), 39106 Magdeburg, Germany
| | - Michael R. Kreutz
- Research Group Neuroplasticity, Leibniz Institute for Neurobiology, 39118 Magdeburg, Germany
- Center for Behavioral Brain Sciences (CBBS), 39106 Magdeburg, Germany
- Leibniz Group 'Dendritic Organelles and Synaptic Function', University Medical Center Hamburg-Eppendorf, Center for Molecular Neurobiology (ZMNH), 20251 Hamburg, Germany
- German Center for Neurodegenerative Diseases (DZNE), 39120 Magdeburg, Germany
| | - Jeffrey Lopez-Rojas
- Research Group Neuroplasticity, Leibniz Institute for Neurobiology, 39118 Magdeburg, Germany
- Center for Behavioral Brain Sciences (CBBS), 39106 Magdeburg, Germany
- Department of Neuroscience, The Kavli Institute for Brain Science, Mortimer B. Zuckerman Mind Brain Behavior Institute, Vagelos College of Physicians and Surgeons, Columbia University, New York, NY 10027, USA
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18
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Vyleta NP, Snyder JS. Prolonged development of long-term potentiation at lateral entorhinal cortex synapses onto adult-born neurons. PLoS One 2021; 16:e0253642. [PMID: 34143843 PMCID: PMC8213073 DOI: 10.1371/journal.pone.0253642] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2021] [Accepted: 06/09/2021] [Indexed: 11/18/2022] Open
Abstract
Critical period plasticity at adult-born neuron synapses is widely believed to contribute to the learning and memory functions of the hippocampus. Experience regulates circuit integration and for a transient interval, until cells are ~6 weeks old, new neurons display enhanced long-term potentiation (LTP) at afferent and efferent synapses. Since neurogenesis declines substantially with age, this raises questions about the extent of lasting plasticity offered by adult-born neurons. Notably, however, the hippocampus receives sensory information from two major cortical pathways. Broadly speaking, the medial entorhinal cortex conveys spatial information to the hippocampus via the medial perforant path (MPP), and the lateral entorhinal cortex, via the lateral perforant path (LPP), codes for the cues and items that make experiences unique. While enhanced critical period plasticity at MPP synapses is relatively well characterized, no studies have examined long-term plasticity at LPP synapses onto adult-born neurons, even though the lateral entorhinal cortex is uniquely vulnerable to aging and Alzheimer's pathology. We therefore investigated LTP at LPP inputs both within (4-6 weeks) and beyond (8+ weeks) the traditional critical period. At immature stages, adult-born neurons did not undergo significant LTP at LPP synapses, and often displayed long-term depression after theta burst stimulation. However, over the course of 3-4 months, adult-born neurons displayed increasingly greater amounts of LTP. Analyses of short-term plasticity point towards a presynaptic mechanism, where transmitter release probability declines as cells mature, providing a greater dynamic range for strengthening synapses. Collectively, our findings identify a novel form of new neuron plasticity that develops over an extended interval, and may therefore be relevant for maintaining cognitive function in aging.
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Affiliation(s)
- Nicholas P. Vyleta
- Department of Psychology, Djavad Mowafaghian Centre for Brain Health, University of British Columbia, Vancouver, BC, Canada
| | - Jason S. Snyder
- Department of Psychology, Djavad Mowafaghian Centre for Brain Health, University of British Columbia, Vancouver, BC, Canada
- * E-mail:
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19
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Collitti-Klausnitzer J, Hagena H, Dubovyk V, Manahan-Vaughan D. Preferential frequency-dependent induction of synaptic depression by the lateral perforant path and of synaptic potentiation by the medial perforant path inputs to the dentate gyrus. Hippocampus 2021; 31:957-981. [PMID: 34002905 DOI: 10.1002/hipo.23338] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2020] [Revised: 04/28/2021] [Accepted: 05/02/2021] [Indexed: 12/19/2022]
Abstract
The encoding of spatial representations is enabled by synaptic plasticity. The entorhinal cortex sends information to the hippocampus via the lateral (LPP) and medial perforant (MPP) paths that transfer egocentric item-related and allocentric spatial information, respectively. To what extent LPP and MPP information-relay results in different homosynaptic synaptic plasticity responses is unclear. We examined the frequency dependency (at 1, 5, 10, 50, 100, 200 Hz) of long-term potentiation (LTP) and long-term depression (LTD) at MPP and LPP synapses in the dentate gyrus (DG) of freely behaving adult rats. We report that whereas the MPP-DG synapses exhibit a predisposition toward the expression of LTP, LPP-DG synapses prefer to express synaptic depression. The divergence of synaptic plasticity responses is most prominent at afferent frequencies of 5, 100, Hz and 200 Hz. Priming with 10 or 50 Hz significantly modified the subsequent plasticity response in a frequency-dependent manner, but failed to change the preferred direction of change in synaptic strength of MPP and LPP synapses. Evaluation of the expression of GluN1, GluN2A, or GluN2B subunits of the NMDA receptor revealed equivalent expression in the outer and middle thirds of the molecular layer where LPP and MPP inputs convene, respectively, thus excluding NMDA receptors as a substrate for the frequency-dependent differences in bidirectional plasticity. These findings demonstrate that the LPP and MPP inputs to the DG enable differentiated and distinct forms of synaptic plasticity in response to the same afferent frequencies. Effects are extremely robust and resilient to metaplastic priming. These properties may support the functional differentiation of allocentric and item information provided to the DG by the MPP and LPP, respectively, that has been proposed by others. We propose that allocentric spatial information, conveyed by the MPP is encoded through hippocampal LTP in a designated synaptic network. This network is refined and optimized to include egocentric contextual information through LTD triggered by LPP inputs.
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Affiliation(s)
| | - Hardy Hagena
- Department of Neurophysiology, Medical Faculty, Ruhr University Bochum, Germany
| | - Valentyna Dubovyk
- Department of Neurophysiology, Medical Faculty, Ruhr University Bochum, Germany
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20
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Díaz González M, Buberman A, Morales M, Ferrer I, Knafo S. Aberrant Synaptic PTEN in Symptomatic Alzheimer's Patients May Link Synaptic Depression to Network Failure. Front Synaptic Neurosci 2021; 13:683290. [PMID: 34045952 PMCID: PMC8144462 DOI: 10.3389/fnsyn.2021.683290] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2021] [Accepted: 04/19/2021] [Indexed: 11/13/2022] Open
Abstract
In Alzheimer’s disease (AD), Amyloid β (Aβ) impairs synaptic function by inhibiting long-term potentiation (LTP), and by facilitating long-term depression (LTD). There is now evidence from AD models that Aβ provokes this shift toward synaptic depression by triggering the access to and accumulation of PTEN in the postsynaptic terminal of hippocampal neurons. Here we quantified the PTEN in 196,138 individual excitatory dentate gyrus synapses from AD patients at different stages of the disease and from controls with no neuropathological findings. We detected a gradual increase of synaptic PTEN in AD brains as the disease progresses, in conjunction with a significant decrease in synaptic density. The synapses that remain in symptomatic AD patients are more likely to be smaller and exhibit fewer AMPA receptors (AMPARs). Hence, a high Aβ load appears to strongly compromise human hippocampal synapses, as reflected by an increase in PTEN, inducing a loss of AMPARs that may eventually provoke synaptic failure and loss.
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Affiliation(s)
- Marta Díaz González
- Department of Physiology and Cell Biology, Faculty of Health Sciences, The National Institute for Biotechnology in the Negev, Ben-Gurion University of the Negev, Beer-Sheva, Israel
| | - Assaf Buberman
- Department of Physiology and Cell Biology, Faculty of Health Sciences, The National Institute for Biotechnology in the Negev, Ben-Gurion University of the Negev, Beer-Sheva, Israel
| | - Miguel Morales
- Instituto Biofisika (UPV/EHU, CSIC), University of the Basque Country, Leioa, Spain
| | - Isidro Ferrer
- Department of Pathology and Experimental Therapeutics, Biomedical Network Research Center of Neurodegenerative Diseases (CIBERNED), Biomedical Research Institute of Bellvitge (IDIBELL), Service of Pathologic Anatomy, Bellvitge University Hospital, University of Barcelona, L'Hospitalet de Llobregat, Spain
| | - Shira Knafo
- Department of Physiology and Cell Biology, Faculty of Health Sciences, The National Institute for Biotechnology in the Negev, Ben-Gurion University of the Negev, Beer-Sheva, Israel.,Instituto Biofisika (UPV/EHU, CSIC), University of the Basque Country, Leioa, Spain.,Ikerbasque, Basque Foundation for Science, Bilbao, Spain
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21
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Huckleberry KA, Shansky RM. The unique plasticity of hippocampal adult-born neurons: Contributing to a heterogeneous dentate. Hippocampus 2021; 31:543-556. [PMID: 33638581 DOI: 10.1002/hipo.23318] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2020] [Revised: 01/15/2021] [Accepted: 02/09/2021] [Indexed: 12/14/2022]
Abstract
The dentate gyrus (DG) of the hippocampus is evolutionarily conserved as one of the few sites of adult neurogenesis in mammals. Although there is clear evidence that neurogenesis is necessary for healthy hippocampal function, whether adult-born neurons are simply integrated into existing hippocampal networks to serve a similar purpose to that of developmentally born neurons or whether they represent a discrete cell population with unique functions remains less clear. In this review, we consider evidence for discrete cellular, synaptic, and structural features of adult-born DG neurons, suggesting that neurogenesis contributes to the formation of a heterogeneous DG. We therefore propose that hippocampal neurogenesis creates a specialized neuronal subpopulation that may play a key role in hippocampal functions like episodic memory. We note critical gaps in this extensive body of work, including a general failure to include female animals in relevant research and a need for more precise consideration of intrahippocampal neuroanatomy.
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Affiliation(s)
- Kylie A Huckleberry
- Behavioral Neuroscience Program, Department of Psychology, Northeastern University, Boston, Massachusetts, USA
| | - Rebecca M Shansky
- Behavioral Neuroscience Program, Department of Psychology, Northeastern University, Boston, Massachusetts, USA
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22
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Houser CR, Peng Z, Wei X, Huang CS, Mody I. Mossy Cells in the Dorsal and Ventral Dentate Gyrus Differ in Their Patterns of Axonal Projections. J Neurosci 2021; 41:991-1004. [PMID: 33268544 PMCID: PMC7880284 DOI: 10.1523/jneurosci.2455-20.2020] [Citation(s) in RCA: 21] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2020] [Revised: 11/08/2020] [Accepted: 11/20/2020] [Indexed: 01/22/2023] Open
Abstract
Mossy cells (MCs) of the dentate gyrus (DG) are a major group of excitatory hilar neurons that are important for regulating activity of dentate granule cells. MCs are particularly intriguing because of their extensive longitudinal connections within the DG. It has generally been assumed that MCs in the dorsal and ventral DG have similar patterns of termination in the inner one-third of the dentate molecular layer. Here, we demonstrate that axonal projections of MCs in these two regions are considerably different. MCs in dorsal and ventral regions were labeled selectively with Cre-dependent eYFP or mCherry, using two transgenic mouse lines (including both sexes) that express Cre-recombinase in MCs. At four to six weeks following unilateral labeling of MCs in the ventral DG, a dense band of fibers was present in the inner one-fourth of the molecular layer and extended bilaterally throughout the rostral-caudal extent of the DG, replicating the expected distribution of MC axons. In contrast, following labeling of MCs in the dorsal DG, the projections were more diffusely distributed. At the level of transfection, fibers were present in the inner molecular layer, but they progressively expanded into the middle molecular layer and, most ventrally, formed a distinct band in this region. Optical stimulation of these caudal fibers expressing ChR2 demonstrated robust EPSCs in ipsilateral granule cells and enhanced the effects of perforant path stimulation in the ventral DG. These findings suggest that MCs in the dorsal and ventral DG differ in the distribution of their axonal projections and possibly their function.SIGNIFICANCE STATEMENT Mossy cells (MCs), a major cell type in the hilus of the dentate gyrus (DG), are unique in providing extensive longitudinal and commissural projections throughout the DG. Although it has been assumed that all MCs have similar patterns of termination in the inner molecular layer of the DG, we discovered that the axonal projections of dorsal and ventral MCs differ. While ventral MC projections exhibit the classical pattern, with dense innervation in the inner molecular layer, dorsal MCs have a more diffuse distribution and expand into the middle molecular layer where they overlap and interact with innervation from the perforant path. These distinct locations and patterns of axonal projections suggest that dorsal and ventral MCs may have different functional roles.
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Affiliation(s)
- Carolyn R Houser
- Department of Neurobiology
- Brain Research Institute, David Geffen School of Medicine at the University of California, Los Angeles, Los Angeles, California 90095
| | | | | | | | - Istvan Mody
- Department of Neurology
- Brain Research Institute, David Geffen School of Medicine at the University of California, Los Angeles, Los Angeles, California 90095
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23
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Gustus K, Li L, Newville J, Cunningham LA. Functional and Structural Correlates of Impaired Enrichment-Mediated Adult Hippocampal Neurogenesis in a Mouse Model of Prenatal Alcohol Exposure. Brain Plast 2020; 6:67-82. [PMID: 33680847 PMCID: PMC7902980 DOI: 10.3233/bpl-200112] [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] [Indexed: 12/24/2022] Open
Abstract
Background: Fetal alcohol spectrum disorders (FASDs) are associated with a wide range of cognitive deficiencies. Objective: We previously
found that gestational exposure to moderate levels of alcohol in mice throughout the 1st-2nd human trimester-equivalents
for brain development results in profound impairment of the hippocampal neurogenic response to enriched environment
(EE) in adulthood, without altering baseline neurogenesis rate under standard housing (SH). However, the functional and
structural consequences of impaired EE-mediated neurogenesis in the context of prenatal alcohol exposure (PAE) have
not been determined. Results: Here, we demonstrate that PAE-EE mice display impaired performance on a neurogenesis-dependent
pattern discrimination task, broadened behavioral activation of the dentate gyrus, as assessed by expression of the immediate
early gene, c-Fos, and impaired dendritic branching of adult-generated dentate granule cells (aDGCs). Conclusions: These studies further underscore the impact of moderate gestational alcohol exposure on adult hippocampal plasticity and support adult hippocampal neurogenesis as a potential therapeutic target to remediate certain neurological outcomes in FASD.
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Affiliation(s)
- Kymberly Gustus
- Department of Neurosciences, University of New Mexico School of Medicine, Albuquerque, NM, USA
| | - Lu Li
- Department of Neurosciences, University of New Mexico School of Medicine, Albuquerque, NM, USA
| | - Jessie Newville
- Department of Neurosciences, University of New Mexico School of Medicine, Albuquerque, NM, USA
| | - Lee Anna Cunningham
- Department of Neurosciences, University of New Mexico School of Medicine, Albuquerque, NM, USA
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24
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FGFR Regulation of Dendrite Elaboration in Adult-born Granule Cells Depends on Intracellular Mediator and Proximity to the Soma. Neuroscience 2020; 453:148-167. [PMID: 33246055 DOI: 10.1016/j.neuroscience.2020.10.024] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2020] [Revised: 10/20/2020] [Accepted: 10/21/2020] [Indexed: 01/24/2023]
Abstract
Fibroblast Growth Factor Receptors (FGFRs) play crucial roles in promoting dendrite growth and branching during development. In mice, three FGFR genes, Fgfr1, Fgfr2, and Fgfr3, remain expressed in the adult neurogenic niche of the hippocampal dentate gyrus. However, the function of FGFRs in the dendritic maturation of adult-born neurons remains largely unexplored. Here, using conditional alleles of Fgfr1, Fgfr2, and Fgfr3 as well as Fgfr1 alleles lacking binding sites for Phospholipase-Cγ (PLCγ) and FGF Receptor Substrate (FRS) proteins, we test the requirement for FGFRs in dendritogenesis of adult-born granule cells. We find that deleting all three receptors results in a small decrease in proximal dendrite elaboration. In contrast, specifically mutating Tyr766 in FGFR1 (a PLCγ binding site) in an Fgfr2;Fgfr3 deficient background results in a dramatic increase of overall dendrite elaboration, while blocking FGFR1-FRS signaling causes proximal dendrite deficits and, to a lesser extent than Tyr766 mutants, increases distal dendrite elaboration. These findings reveal unexpectedly complex roles for FGFRs and their intracellular mediators in regulating proximal and distal dendrite elaboration, with the most notable role in suppressing distal elaboration through the PLCγbinding site.
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25
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Young JK. Neurogenesis Makes a Crucial Contribution to the Neuropathology of Alzheimer's Disease. J Alzheimers Dis Rep 2020; 4:365-371. [PMID: 33163897 PMCID: PMC7592839 DOI: 10.3233/adr-200218] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
One unexplained feature of Alzheimer’s disease (AD) is that the lateral entorhinal cortex undergoes neurodegeneration before other brain areas. However, this brain region does not have elevated levels of amyloid peptides in comparison with undamaged regions. What is the cause of this special vulnerability of the entorhinal cortex? One special feature of the lateral entorhinal cortex is that it projects to newborn neurons that have undergone adult neurogenesis in the dentate gyrus of the hippocampus. Neurogenesis is abnormal in human AD brains, and modulation of neurogenesis in experimental animals influences the course of AD. This complex process of neurogenesis may expose axon terminals originating from neurons of the entorhinal cortex to a unique combination of molecules that can enhance toxic effects of amyloid. Retrograde degeneration of neurons with axons terminating in the dentate gyrus provides a likely explanation for the spatial patterns of neuronal cell death seen in AD. Specialized astrocytes in the dentate gyrus participate in adult neurogenesis and produce fatty acid binding protein7 (FABP7). These FABP7+ cells undergo an aging-related mitochondrial pathology that likely impairs their functions. This age-related abnormality may contribute to the impairment in neurogenesis seen in aging and Alzheimer’s disease. Also, a compromised function of these astrocytes likely results in local elevations of palmitic acid, iron, copper, and glucose, which all enhance the toxicity of amyloid peptides. Treatments that modulate neurogenesis or diminish the production of these toxic substances may prove more successful than treatments that are solely aimed at reducing the amyloid burden alone.
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Affiliation(s)
- John K Young
- Professor Emeritus, Department of Anatomy, Howard University College of Medicine, Washington, DC, USA
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26
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Woods NI, Stefanini F, Apodaca-Montano DL, Tan IMC, Biane JS, Kheirbek MA. The Dentate Gyrus Classifies Cortical Representations of Learned Stimuli. Neuron 2020; 107:173-184.e6. [PMID: 32359400 DOI: 10.1016/j.neuron.2020.04.002] [Citation(s) in RCA: 46] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2019] [Revised: 03/16/2020] [Accepted: 03/31/2020] [Indexed: 10/24/2022]
Abstract
Animals must discern important stimuli and place them onto their cognitive map of their environment. The neocortex conveys general representations of sensory events to the hippocampus, and the hippocampus is thought to classify and sharpen the distinctions between these events. We recorded populations of dentate gyrus granule cells (DG GCs) and lateral entorhinal cortex (LEC) neurons across days to understand how sensory representations are modified by experience. We found representations of odors in DG GCs that required synaptic input from the LEC. Odor classification accuracy in DG GCs correlated with future behavioral discrimination. In associative learning, DG GCs, more so than LEC neurons, changed their responses to odor stimuli, increasing the distance in neural representations between stimuli, responding more to the conditioned and less to the unconditioned odorant. Thus, with learning, DG GCs amplify the decodability of cortical representations of important stimuli, which may facilitate information storage to guide behavior.
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Affiliation(s)
- Nicholas I Woods
- Neuroscience Graduate Program, University of California, San Francisco, San Francisco, CA 94158, USA; Medical Scientist Training Program, University of California, San Francisco, San Francisco, CA 94158, USA
| | - Fabio Stefanini
- Center for Theoretical Neuroscience, Mortimer B. Zuckerman Mind Brain Behavior Institute, Department of Neuroscience, Columbia University, New York, NY 10027, USA
| | | | - Isabelle M C Tan
- Department of Psychiatry, University of California, San Francisco, San Francisco, CA 94158, USA
| | - Jeremy S Biane
- Department of Psychiatry, University of California, San Francisco, San Francisco, CA 94158, USA
| | - Mazen A Kheirbek
- Neuroscience Graduate Program, University of California, San Francisco, San Francisco, CA 94158, USA; Department of Psychiatry, University of California, San Francisco, San Francisco, CA 94158, USA; Kavli Institute for Fundamental Neuroscience, University of California, San Francisco, San Francisco, CA 94158, USA; Weill Institute for Neurosciences, University of California, San Francisco, San Francisco, CA 94158, USA; Center for Integrative Neuroscience, University of California, San Francisco, San Francisco, CA 94158, USA.
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27
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Zingg B, Peng B, Huang J, Tao HW, Zhang LI. Synaptic Specificity and Application of Anterograde Transsynaptic AAV for Probing Neural Circuitry. J Neurosci 2020; 40:3250-3267. [PMID: 32198185 PMCID: PMC7159884 DOI: 10.1523/jneurosci.2158-19.2020] [Citation(s) in RCA: 92] [Impact Index Per Article: 23.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2019] [Revised: 03/05/2020] [Accepted: 03/08/2020] [Indexed: 12/20/2022] Open
Abstract
Revealing the organization and function of neural circuits is greatly facilitated by viral tools that spread transsynaptically. Adeno-associated virus (AAV) exhibits anterograde transneuronal transport, however, the synaptic specificity of this spread and its broad application within a diverse set of circuits remains to be explored. Here, using anatomic, functional, and molecular approaches, we provide evidence for the preferential transport of AAV1 to postsynaptically connected neurons and reveal its spread is strongly dependent on synaptic transmitter release. In addition to glutamatergic pathways, AAV1 also spreads through GABAergic synapses to both excitatory and inhibitory cell types. We observed little or no transport, however, through neuromodulatory projections (e.g., serotonergic, cholinergic, and noradrenergic). In addition, we found that AAV1 can be transported through long-distance descending projections from various brain regions to effectively transduce spinal cord neurons. Combined with newly designed intersectional and sparse labeling strategies, AAV1 can be applied within a wide variety of pathways to categorize neurons according to their input sources, morphology, and molecular identities. These properties make AAV1 a promising anterograde transsynaptic tool for establishing a comprehensive cell-atlas of the brain, although its capacity for retrograde transport currently limits its use to unidirectional circuits.SIGNIFICANCE STATEMENT The discovery of anterograde transneuronal spread of AAV1 generates great promise for its application as a unique tool for manipulating input-defined cell populations and mapping their outputs. However, several outstanding questions remain for anterograde transsynaptic approaches in the field: (1) whether AAV1 spreads exclusively or specifically to synaptically connected neurons, and (2) how broad its application could be in various types of neural circuits in the brain. This study provides several lines of evidence in terms of anatomy, functional innervation, and underlying mechanisms, to strongly support that AAV1 anterograde transneuronal spread is highly synapse specific. In addition, several potentially important applications of transsynaptic AAV1 in probing neural circuits are described.
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Affiliation(s)
- Brian Zingg
- Zilkha Neurogenetic Institute
- Neuroscience Graduate Program, Keck School of Medicine, University of Southern California, Los Angeles, California 90033
| | - Bo Peng
- Zilkha Neurogenetic Institute
- Neuroscience Graduate Program, Keck School of Medicine, University of Southern California, Los Angeles, California 90033
| | - Junxiang Huang
- Zilkha Neurogenetic Institute
- Neuroscience Graduate Program, Keck School of Medicine, University of Southern California, Los Angeles, California 90033
| | - Huizhong W Tao
- Zilkha Neurogenetic Institute
- Department of Physiology and Neuroscience
| | - Li I Zhang
- Zilkha Neurogenetic Institute
- Department of Physiology and Neuroscience
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28
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Steffke EE, Kirca D, Mazei-Robison MS, Robison AJ. Serum- and glucocorticoid-inducible kinase 1 activity reduces dendritic spines in dorsal hippocampus. Neurosci Lett 2020; 725:134909. [PMID: 32169587 DOI: 10.1016/j.neulet.2020.134909] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2019] [Revised: 02/28/2020] [Accepted: 03/09/2020] [Indexed: 12/19/2022]
Abstract
The hippocampus has a well-known role in mediating learning and memory, and its function can be directly regulated by both stress and glucocorticoid receptor activation. Hippocampal contributions to learning are thought to be dependent on changes in the plasticity of synapses within specific subregions, and these functional changes are accompanied by morphological changes in the number and shape of dendritic spines, the physical correlates of these glutamatergic synapses. Serum- and glucocorticoid-inducible kinase 1 (SGK1) regulates dendritic spine morphology in the prefrontal cortex, and modulation of SGK1 expression in mouse hippocampus regulates learning. However, the role of SGK1 in dendritic spine morphology within the CA1 and dentate gyrus regions of the hippocampus are unknown. Thus, herpes simplex viral vectors expressing GFP and various SGK1 constructs, including wild type SGK1, a catalytically inactive version of SGK1 (K127Q), and a phospho-defective version of SGK1 (S78A), were infused into the hippocampus of adult mice and confocal fluorescent microscopy was used to visualize dendritic spines. We show that increasing expression of SGK1 in the dentate gyrus increased the total number of spines, driven primarily by an increase in mushroom spines, while decreasing SGK1 activity (K127Q) in the CA1 region increased the total number of dendritic spines, driven by a significant increase in mushroom and stubby spines. The differential effects of SGK1 in these regions may be mediated by the interactions of SGK1 with multiple pathways required for spine formation and stability. As the formation of mature synapses is a crucial component of learning and memory, this indicates that SGK1 is a potential target in the pathway underlying stress-associated changes in cognition and memory.
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Affiliation(s)
- Emily E Steffke
- Department of Physiology, Michigan State University, East Lansing, MI, 48824, United States
| | - Deniz Kirca
- Department of Physiology, Michigan State University, East Lansing, MI, 48824, United States
| | | | - Alfred J Robison
- Department of Physiology, Michigan State University, East Lansing, MI, 48824, United States.
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29
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Dentate gyrus circuits for encoding, retrieval and discrimination of episodic memories. Nat Rev Neurosci 2020; 21:153-168. [PMID: 32042144 DOI: 10.1038/s41583-019-0260-z] [Citation(s) in RCA: 186] [Impact Index Per Article: 46.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/18/2019] [Indexed: 12/19/2022]
Abstract
The dentate gyrus (DG) has a key role in hippocampal memory formation. Intriguingly, DG lesions impair many, but not all, hippocampus-dependent mnemonic functions, indicating that the rest of the hippocampus (CA1-CA3) can operate autonomously under certain conditions. An extensive body of theoretical work has proposed how the architectural elements and various cell types of the DG may underlie its function in cognition. Recent studies recorded and manipulated the activity of different neuron types in the DG during memory tasks and have provided exciting new insights into the mechanisms of DG computational processes, particularly for the encoding, retrieval and discrimination of similar memories. Here, we review these DG-dependent mnemonic functions in light of the new findings and explore mechanistic links between the cellular and network properties of, and the computations performed by, the DG.
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30
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Abstract
The dentate gyrus continually produces new neurons throughout life. Behavioral studies in rodents and network models show that new neurons contribute to normal dentate functions, but there are many unanswered questions about how the relatively small population of new neurons alters network activity. Here we discuss experimental evidence that supports multiple cellular mechanisms by which adult-born neurons contribute to circuit function. Whereas past work focused on the unique intrinsic properties of young neurons, more recent studies also suggest that adult-born neurons alter the excitability of the mature neuronal population via unexpected circuit interactions.
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Affiliation(s)
- Cristina V Dieni
- Department of Ophthalmology and Visual Sciences, University of Alabama at Birmingham, Birmingham, AL, 35294, USA
| | - Jose Carlos Gonzalez
- Department of Neurobiology, University of Alabama at Birmingham, Birmingham, AL, 35294, USA
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31
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Tuncdemir SN, Lacefield CO, Hen R. Contributions of adult neurogenesis to dentate gyrus network activity and computations. Behav Brain Res 2019; 374:112112. [PMID: 31377252 PMCID: PMC6724741 DOI: 10.1016/j.bbr.2019.112112] [Citation(s) in RCA: 44] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2019] [Revised: 07/18/2019] [Accepted: 07/24/2019] [Indexed: 01/01/2023]
Abstract
Anatomical observations, theoretical work and lesion experiments have led to the idea that an important function of the dentate gyrus of the mammalian hippocampus is pattern separation, a neural computation that ensures new memories are encoded without interference from previously stored memories that share similar features. The dentate gyrus also exhibits a unique form of neural plasticity that results from the continuous integration of newly born excitatory granule cells, termed adult hippocampal neurogenesis. However, the manner in which adult neurogenesis contributes to dentate gyrus network activity and computations is incompletely understood. Here, we first describe the prevailing models for the role of adult neurogenesis in dentate gyrus network function and then re-evaluate these models in the light of recent findings regarding the in vivo activity of the dentate gyrus and synaptic interactions of adult born granule cells with local circuit components, as well as, inputs, and outputs of the dentate gyrus. We propose that adult neurogenesis provides flexibility for the dentate gyrus to rapidly generate a context specific, distributed representation of important sensory stimuli such as spatial cues, which ultimately gives rise to behavioral discrimination.
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Affiliation(s)
- Sebnem Nur Tuncdemir
- Department of Psychiatry, Division of Systems Neuroscience, Columbia University and the Research Foundation for Mental Hygiene, New York State Psychiatric Institute, NY, USA.
| | - Clay Orion Lacefield
- Department of Psychiatry, Division of Systems Neuroscience, Columbia University and the Research Foundation for Mental Hygiene, New York State Psychiatric Institute, NY, USA
| | - Rene Hen
- Department of Psychiatry, Division of Systems Neuroscience, Columbia University and the Research Foundation for Mental Hygiene, New York State Psychiatric Institute, NY, USA.
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32
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Christian KM, Ming GL, Song H. Adult neurogenesis and the dentate gyrus: Predicting function from form. Behav Brain Res 2019; 379:112346. [PMID: 31722241 DOI: 10.1016/j.bbr.2019.112346] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2019] [Revised: 11/05/2019] [Accepted: 11/05/2019] [Indexed: 12/11/2022]
Abstract
Hypotheses about the functional properties of the dentate gyrus and adult dentate neurogenesis have been shaped by early observations of the anatomy of this region, mostly in rodents. This has led to the development of a few core propositions that have guided research over the past several years, including the predicted role of this region in pattern separation and the local transformation of inputs from the entorhinal cortex. We now have the opportunity to review these predictions and update these anatomical observations based on recently developed techniques that reveal the complex structure, connectivity, and dynamic properties of distinct cell populations in the dentate gyrus at a higher resolution. Cumulative evidence suggests that the dentate gyrus and adult-born granule cells play a role in some forms of behavioral discriminations, but there are still many unanswered questions about how the dentate gyrus processes information to support the disambiguation of stimuli.
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Affiliation(s)
- Kimberly M Christian
- Department of Neuroscience, University of Pennsylvania, Philadelphia, PA, 19104, USA; Mahoney Institute for Neurosciences, University of Pennsylvania, Philadelphia, PA, 19104, USA.
| | - Guo-Li Ming
- Department of Neuroscience, University of Pennsylvania, Philadelphia, PA, 19104, USA; Mahoney Institute for Neurosciences, University of Pennsylvania, Philadelphia, PA, 19104, USA; Department of Developmental and Cell Biology, University of Pennsylvania, Philadelphia, PA, 19104, USA; Institute for Regenerative Medicine, University of Pennsylvania, Philadelphia, PA, 19104, USA; Department of Psychiatry, University of Pennsylvania, Philadelphia, PA, 19104, USA; Institute for Epigenetics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Hongjun Song
- Department of Neuroscience, University of Pennsylvania, Philadelphia, PA, 19104, USA; Mahoney Institute for Neurosciences, University of Pennsylvania, Philadelphia, PA, 19104, USA; Department of Developmental and Cell Biology, University of Pennsylvania, Philadelphia, PA, 19104, USA; Institute for Regenerative Medicine, University of Pennsylvania, Philadelphia, PA, 19104, USA; Institute for Epigenetics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA.
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33
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Pten loss results in inappropriate excitatory connectivity. Mol Psychiatry 2019; 24:1627-1640. [PMID: 30967683 PMCID: PMC6785382 DOI: 10.1038/s41380-019-0412-6] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/12/2018] [Revised: 01/31/2019] [Accepted: 03/18/2019] [Indexed: 11/10/2022]
Abstract
Pten mutations are associated with autism spectrum disorder. Pten loss of function in neurons increases excitatory synaptic connectivity, contributing to an imbalance between excitation and inhibition. We aimed to determine whether Pten loss results in aberrant connectivity in neural circuits. We compared postnatally generated wild-type and Pten knockout granule neurons integrating into the dentate gyrus using a variety of methods to examine their connectivity. We found that postsynaptic Pten loss provides an advantage to dendritic spines in competition over a limited pool of presynaptic boutons. Retrograde monosynaptic tracing with rabies virus reveals that this results in synaptic contact with more presynaptic partners. Using independently excitable opsins to interrogate multiple inputs onto a single neuron, we found that excess connectivity is established indiscriminately from among glutamatergic afferents. Therefore, Pten loss results in inappropriate connectivity whereby neurons are coupled to a greater number of synaptic partners.
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34
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Dentate Gyrus Mossy Cells Share a Role in Pattern Separation with Dentate Granule Cells and Proximal CA3 Pyramidal Cells. J Neurosci 2019; 39:9570-9584. [PMID: 31641051 DOI: 10.1523/jneurosci.0940-19.2019] [Citation(s) in RCA: 29] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2019] [Revised: 09/26/2019] [Accepted: 10/03/2019] [Indexed: 01/04/2023] Open
Abstract
The complementary processes of pattern completion and pattern separation are thought to be essential for successful memory storage and recall. The dentate gyrus (DG) and proximal CA3 (pCA3) regions have been implicated in pattern separation, in part through extracellular recording studies of these areas. However, the DG contains two types of excitatory cells: granule cells of the granule layer and mossy cells of the hilus. Little is known about the firing properties of mossy cells in freely moving animals, and it is unclear how their activity may contribute to the mnemonic functions of the hippocampus. Furthermore, tetrodes in the dentate granule layer and pCA3 pyramidal layer can also record mossy cells, thus introducing ambiguity into the identification of cell types recorded. Using a random forests classifier, we classified cells recorded in DG (Neunuebel and Knierim, 2014) and pCA3 (Lee et al., 2015) of 16 male rats and separately examined the responses of granule cells, mossy cells, and pCA3 pyramidal cells in a local/global cue mismatch task. All three cell types displayed low correlations between the population representations of the rat's position in the standard and cue-mismatch sessions. These results suggest that all three excitatory cell types within the DG/pCA3 circuit may act as a single functional unit to support pattern separation.SIGNIFICANCE STATEMENT Mossy cells in the dentate gyrus (DG) are an integral component of the DG/pCA3 circuit. While the role of granule cells in the circuitry and computations of the hippocampus has been a focus of study for decades, the contributions of mossy cells have been largely overlooked. Recent studies have revealed the spatial firing properties of mossy cells in awake behaving animals, but how the activity of these highly active cells contributes to the mnemonic functions of the DG is uncertain. We separately analyzed mossy cells, granule cells, and pCA3 cells and found that all three cell types respond similarly to a local/global cue mismatch, suggesting that they form a single functional unit supporting pattern separation.
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Miller SM, Sahay A. Functions of adult-born neurons in hippocampal memory interference and indexing. Nat Neurosci 2019; 22:1565-1575. [PMID: 31477897 DOI: 10.1038/s41593-019-0484-2] [Citation(s) in RCA: 72] [Impact Index Per Article: 14.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2019] [Accepted: 07/30/2019] [Indexed: 12/22/2022]
Abstract
The dentate gyrus-CA3 circuit of the hippocampus is continuously modified by the integration of adult-born dentate granule cells (abDGCs). All abDGCs undergo a prolonged period of maturation, during which they exhibit heightened synaptic plasticity and refinement of electrophysiological properties and connectivity. Consistent with theoretical models and the known functions of the dentate gyrus-CA3 circuit, acute or chronic manipulations of abDGCs support a role for abDGCs in the regulation of memory interference. In this Review, we integrate insights from studies that examine the maturation of abDGCs and their integration into the circuit with network mechanisms that support memory discrimination, consolidation and clearance. We propose that adult hippocampal neurogenesis enables the generation of a library of experiences, each registered in mature abDGC physiology and connectivity. Mature abDGCs recruit inhibitory microcircuits to support pattern separation and memory indexing.
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Affiliation(s)
- Samara M Miller
- Center for Regenerative Medicine, Massachusetts General Hospital, Boston, Massachusetts, USA.,Harvard Stem Cell Institute, Cambridge, Massachusetts, USA.,Department of Psychiatry, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts, USA
| | - Amar Sahay
- Center for Regenerative Medicine, Massachusetts General Hospital, Boston, Massachusetts, USA. .,Harvard Stem Cell Institute, Cambridge, Massachusetts, USA. .,Department of Psychiatry, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts, USA. .,BROAD Institute of Harvard and MIT, Cambridge, Massachusetts, USA.
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Chatzi C, Zhang Y, Hendricks WD, Chen Y, Schnell E, Goodman RH, Westbrook GL. Exercise-induced enhancement of synaptic function triggered by the inverse BAR protein, Mtss1L. eLife 2019; 8:45920. [PMID: 31232686 PMCID: PMC6609409 DOI: 10.7554/elife.45920] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2019] [Accepted: 06/22/2019] [Indexed: 01/11/2023] Open
Abstract
Exercise is a potent enhancer of learning and memory, yet we know little of the underlying mechanisms that likely include alterations in synaptic efficacy in the hippocampus. To address this issue, we exposed mice to a single episode of voluntary exercise, and permanently marked activated mature hippocampal dentate granule cells using conditional Fos-TRAP mice. Exercise-activated neurons (Fos-TRAPed) showed an input-selective increase in dendritic spines and excitatory postsynaptic currents at 3 days post-exercise, indicative of exercise-induced structural plasticity. Laser-capture microdissection and RNASeq of activated neurons revealed that the most highly induced transcript was Mtss1L, a little-studied I-BAR domain-containing gene, which we hypothesized could be involved in membrane curvature and dendritic spine formation. shRNA-mediated Mtss1L knockdown in vivo prevented the exercise-induced increases in spines and excitatory postsynaptic currents. Our results link short-term effects of exercise to activity-dependent expression of Mtss1L, which we propose as a novel effector of activity-dependent rearrangement of synapses.
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Affiliation(s)
- Christina Chatzi
- Vollum Institute, Oregon Health & Science University, Portland, United States
| | - Yingyu Zhang
- Vollum Institute, Oregon Health & Science University, Portland, United States
| | - Wiiliam D Hendricks
- Vollum Institute, Oregon Health & Science University, Portland, United States.,Neuroscience Graduate Program, Vollum Institute, Oregon Health & Science University, Portland, United States
| | - Yang Chen
- Vollum Institute, Oregon Health & Science University, Portland, United States.,Neuroscience Graduate Program, Vollum Institute, Oregon Health & Science University, Portland, United States
| | - Eric Schnell
- Department of Anesthesiology and Perioperative Medicine, Oregon Health & Science University, Portland, United States.,Portland VA Health Care System, Portland, United States
| | - Richard H Goodman
- Vollum Institute, Oregon Health & Science University, Portland, United States
| | - Gary L Westbrook
- Vollum Institute, Oregon Health & Science University, Portland, United States
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Synaptic properties of newly generated granule cells support sparse coding in the adult hippocampus. Behav Brain Res 2019; 372:112036. [PMID: 31201871 DOI: 10.1016/j.bbr.2019.112036] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2019] [Revised: 06/06/2019] [Accepted: 06/11/2019] [Indexed: 12/14/2022]
Abstract
In the adult hippocampus new neurons are continuously generated throughout life and integrate into the existing network via the formation of thousands of new synapses. Adult-born granule cells are known to improve learning and memory at about 3-6 weeks post mitosis by enhancing the brains ability to discriminate similar memory items. However, the underlying mechanisms are still controversial. Here we review the distinct functional properties of the newborn young neurons, including enhanced excitability, reduced GABAergic inhibition, NMDA-receptor dependent electrogenesis and enhanced synaptic plasticity. Although these cellular properties provide a competitive advantage for synapse formation, they do not generate 'hyperactivity' of young neurons. By contrast, in vivo evidence from immediate early gene expression and calcium imaging indicates that young neurons show sparse activity during learning. Similarly, in vitro data show a low number of high-impact synapses, leading to activation young cells by distinct subsets of afferent fibers with minimal overlap. Overall, the enhanced excitability of young cells does not generate hyperactivity but rather counterbalance the low number of excitatory input synapses. Finally, sparse coding in young neurons has been shown to be crucial for neurogenesis-dependent improvement of learning behavior. Taken together, converging evidence from cell physiology and behavioral studies suggests a mechanism that can explain the beneficial effects of adult neurogenesis on brain function.
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Luna VM, Anacker C, Burghardt NS, Khandaker H, Andreu V, Millette A, Leary P, Ravenelle R, Jimenez JC, Mastrodonato A, Denny CA, Fenton AA, Scharfman HE, Hen R. Adult-born hippocampal neurons bidirectionally modulate entorhinal inputs into the dentate gyrus. Science 2019; 364:578-583. [PMID: 31073064 PMCID: PMC6800071 DOI: 10.1126/science.aat8789] [Citation(s) in RCA: 115] [Impact Index Per Article: 23.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2018] [Accepted: 03/27/2019] [Indexed: 12/13/2022]
Abstract
Young adult-born granule cells (abGCs) in the dentate gyrus (DG) have a profound impact on cognition and mood. However, it remains unclear how abGCs distinctively contribute to local DG information processing. We found that the actions of abGCs in the DG depend on the origin of incoming afferents. In response to lateral entorhinal cortex (LEC) inputs, abGCs exert monosynaptic inhibition of mature granule cells (mGCs) through group II metabotropic glutamate receptors. By contrast, in response to medial entorhinal cortex (MEC) inputs, abGCs directly excite mGCs through N-methyl-d-aspartate receptors. Thus, a critical function of abGCs may be to regulate the relative synaptic strengths of LEC-driven contextual information versus MEC-driven spatial information to shape distinct neural representations in the DG.
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Affiliation(s)
- Victor M Luna
- Division of Systems Neuroscience, Department of Psychiatry, Columbia University and the Research Foundation for Mental Hygiene, New York State Psychiatric Institute, New York, NY 10032, USA.
| | - Christoph Anacker
- Division of Systems Neuroscience, Department of Psychiatry, Columbia University and the Research Foundation for Mental Hygiene, New York State Psychiatric Institute, New York, NY 10032, USA
- Sackler Institute for Developmental Psychobiology, New York, NY 10065, USA
| | - Nesha S Burghardt
- Department of Psychology, Hunter College, The City University of New York, New York, NY 10021, USA
- Department of Psychology, The Graduate Center, The City University of New York, New York, NY 10016, USA
| | - Hameda Khandaker
- Department of Psychology, Hunter College, The City University of New York, New York, NY 10021, USA
- Department of Psychology, The Graduate Center, The City University of New York, New York, NY 10016, USA
| | - Valentine Andreu
- Division of Systems Neuroscience, Department of Psychiatry, Columbia University and the Research Foundation for Mental Hygiene, New York State Psychiatric Institute, New York, NY 10032, USA
| | - Amira Millette
- Division of Systems Neuroscience, Department of Psychiatry, Columbia University and the Research Foundation for Mental Hygiene, New York State Psychiatric Institute, New York, NY 10032, USA
| | - Paige Leary
- Departments of Child and Adolescent Psychiatry, Neuroscience and Physiology, and Psychiatry and the Neuroscience Institute, New York University Langone Health, New York, NY 10016, USA
| | - Rebecca Ravenelle
- Department of Psychology, Hunter College, The City University of New York, New York, NY 10021, USA
- Department of Biology, The Graduate Center, The City University of New York, New York, NY 10021, USA
| | - Jessica C Jimenez
- Division of Systems Neuroscience, Department of Psychiatry, Columbia University and the Research Foundation for Mental Hygiene, New York State Psychiatric Institute, New York, NY 10032, USA
| | - Alessia Mastrodonato
- Division of Systems Neuroscience, Department of Psychiatry, Columbia University and the Research Foundation for Mental Hygiene, New York State Psychiatric Institute, New York, NY 10032, USA
| | - Christine A Denny
- Division of Systems Neuroscience, Department of Psychiatry, Columbia University and the Research Foundation for Mental Hygiene, New York State Psychiatric Institute, New York, NY 10032, USA
| | - Andre A Fenton
- Center for Neural Science, New York University, New York, NY 10003, USA
- State University of New York Downstate Medical Center, Brooklyn, NY 11203, USA
| | - Helen E Scharfman
- Departments of Child and Adolescent Psychiatry, Neuroscience and Physiology, and Psychiatry and the Neuroscience Institute, New York University Langone Health, New York, NY 10016, USA
| | - Rene Hen
- Division of Systems Neuroscience, Department of Psychiatry, Columbia University and the Research Foundation for Mental Hygiene, New York State Psychiatric Institute, New York, NY 10032, USA.
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Restrained Dendritic Growth of Adult-Born Granule Cells Innervated by Transplanted Fetal GABAergic Interneurons in Mice with Temporal Lobe Epilepsy. eNeuro 2019; 6:ENEURO.0110-18.2019. [PMID: 31043461 PMCID: PMC6497906 DOI: 10.1523/eneuro.0110-18.2019] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2018] [Revised: 03/11/2019] [Accepted: 03/15/2019] [Indexed: 12/16/2022] Open
Abstract
The dentate gyrus (DG) is a region of the adult rodent brain that undergoes continuous neurogenesis. Seizures and loss or dysfunction of GABAergic synapses onto adult-born dentate granule cells (GCs) alter their dendritic growth and migration, resulting in dysmorphic and hyperexcitable GCs. Additionally, transplants of fetal GABAergic interneurons in the DG of mice with temporal lobe epilepsy (TLE) result in seizure suppression, but it is unknown whether increasing interneurons with these transplants restores GABAergic innervation to adult-born GCs. Here, we address this question by birth-dating GCs with retrovirus at different times up to 12 weeks after pilocarpine-induced TLE in adult mice. Channelrhodopsin 2 (ChR2)-enhanced yellow fluorescent protein (EYFP)-expressing medial-ganglionic eminence (MGE)-derived GABAergic interneurons from embryonic day (E)13.5 mouse embryos were transplanted into the DG of the TLE mice and GCs with transplant-derived inhibitory post-synaptic currents (IPSCs) were identified by patch-clamp electrophysiology and optogenetic interrogation. Putative synaptic sites between GCs and GABAergic transplants were also confirmed by intracellular biocytin staining, immunohistochemistry, and confocal imaging. 3D reconstructions of dendritic arbors and quantitative morphometric analyses were carried out in >150 adult-born GCs. GABAergic inputs from transplanted interneurons correlated with markedly shorter GC dendrites, compared to GCs that were not innervated by the transplants. Moreover, these effects were confined to distal dendritic branches and a short time window of six to eight weeks. The effects were independent of seizures as they were also observed in naïve mice with MGE transplants. These findings are consistent with the hypothesis that increased inhibitory currents over a smaller dendritic arbor in adult-born GCs may reduce their excitability and lead to seizure suppression.
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Voss MW, Soto C, Yoo S, Sodoma M, Vivar C, van Praag H. Exercise and Hippocampal Memory Systems. Trends Cogn Sci 2019; 23:318-333. [PMID: 30777641 PMCID: PMC6422697 DOI: 10.1016/j.tics.2019.01.006] [Citation(s) in RCA: 122] [Impact Index Per Article: 24.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2018] [Revised: 01/11/2019] [Accepted: 01/16/2019] [Indexed: 01/17/2023]
Abstract
No medications prevent or reverse age-related cognitive decline. Physical activity (PA) enhances memory in rodents, but findings are mixed in human studies. As a result, exercise guidelines specific for brain health are absent. Here, we re-examine results from human studies, and suggest the use of more sensitive tasks to evaluate PA effects on age-related changes in the hippocampus, such as relational memory and mnemonic discrimination. We discuss recent advances from rodent and human studies into the underlying mechanisms at both the central and peripheral levels, including neurotrophins and myokines that could contribute to improved memory. Finally, we suggest guidelines for future research to help expedite well-founded PA recommendations for the public.
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Affiliation(s)
- Michelle W Voss
- Department of Psychological and Brain Sciences, University of Iowa, Iowa City, IA, USA.
| | - Carmen Soto
- Laboratory of Neurogenesis and Neuroplasticity, Department of Physiology, Biophysics and Neuroscience, Center for Research and Advanced Studies of the National Polytechnic Institute, Mexico City, Mexico
| | - Seungwoo Yoo
- Department of Biomedical Science, Charles E. Schmidt College of Medicine, and Brain Institute, Florida Atlantic University, Jupiter, FL 33458, USA
| | - Matthew Sodoma
- Department of Psychological and Brain Sciences, University of Iowa, Iowa City, IA, USA
| | - Carmen Vivar
- Laboratory of Neurogenesis and Neuroplasticity, Department of Physiology, Biophysics and Neuroscience, Center for Research and Advanced Studies of the National Polytechnic Institute, Mexico City, Mexico
| | - Henriette van Praag
- Department of Biomedical Science, Charles E. Schmidt College of Medicine, and Brain Institute, Florida Atlantic University, Jupiter, FL 33458, USA
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41
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Recalibrating the Relevance of Adult Neurogenesis. Trends Neurosci 2019; 42:164-178. [PMID: 30686490 DOI: 10.1016/j.tins.2018.12.001] [Citation(s) in RCA: 125] [Impact Index Per Article: 25.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2018] [Revised: 11/28/2018] [Accepted: 12/10/2018] [Indexed: 10/27/2022]
Abstract
Conflicting reports about whether adult hippocampal neurogenesis occurs in humans raise questions about its significance for human health and the relevance of animal models. Drawing upon published data, I review species' neurogenesis rates across the lifespan and propose that accelerated neurodevelopmental timing is consistent with lower rates of neurogenesis in adult primates and humans. Nonetheless, protracted neurogenesis may produce populations of neurons that retain plastic properties for long intervals, and have distinct functions depending on when in the lifespan they were born. With some conceptual recalibration we may therefore be able to reconcile seemingly disparate findings and continue to ask how adult neurogenesis, as studied in animals, is relevant for human health.
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