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Bramlett SN, Fitzmaurice SM, Harbin NH, Yan W, Bandlamudi C, Van Doorn GE, Smith Y, Hepler JR. Regulator of G Protein Signaling 14 protein expression profile in the adult mouse brain. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.06.22.600169. [PMID: 38979272 PMCID: PMC11230234 DOI: 10.1101/2024.06.22.600169] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/10/2024]
Abstract
Regulator of G protein signaling 14 (RGS14) is a multifunctional signaling protein that serves as a natural suppressor of synaptic plasticity in the mouse brain. Our previous studies showed that RGS14 is highly expressed in postsynaptic dendrites and spines of pyramidal neurons in hippocampal area CA2 of the developing mouse brain. However, our more recent work with adult rhesus macaque brain shows that RGS14 is found in multiple neuron populations throughout hippocampal area CA1 and CA2, caudate nucleus, putamen, globus pallidus, substantia nigra, and amygdala in the adult rhesus monkey brain. In the mouse brain, we also have observed RGS14 protein in discrete limbic regions linked to reward behavior and addiction, including the central amygdala and the nucleus accumbens, but a comprehensive mapping of RGS14 protein expression in the adult mouse brain is lacking. Here, we report that RGS14 is more broadly expressed in mouse brain than previously known. Intense RGS14 staining is observed in specific neuron populations of the hippocampal formation, amygdala, septum, bed nucleus of stria terminalis and ventral striatum/nucleus accumbens. RGS14 is also observed in axon fiber tracts including the dorsal fornix, fimbria, stria terminalis, and the ventrohippocampal commissure. Moderate RGS14 staining is observed in various other adjacent regions not previously reported. These findings show that RGS14 is expressed in brain regions that govern aspects of core cognitive functions such as sensory perception, emotion, memory, motivation, and execution of actions, and suggests that RGS14 may serve to suppress plasticity and filter inputs in these brain regions to set the overall tone on experience-to-action processes.
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2
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Jabra S, Rietsche M, Muellerleile J, O'Leary A, Slattery DA, Deller T, Fellenz M. Sex- and cycle-dependent changes in spine density and size in hippocampal CA2 neurons. Sci Rep 2024; 14:12252. [PMID: 38806649 PMCID: PMC11133407 DOI: 10.1038/s41598-024-62951-x] [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: 02/27/2024] [Accepted: 05/22/2024] [Indexed: 05/30/2024] Open
Abstract
Sex hormones affect structural and functional plasticity in the rodent hippocampus. However, hormone levels not only differ between males and females, but also fluctuate across the female estrous cycle. While sex- and cycle-dependent differences in dendritic spine density and morphology have been found in the rodent CA1 region, but not in the CA3 or the dentate gyrus, comparable structural data on CA2, i.e. the hippocampal region involved in social recognition memory, is so far lacking. In this study, we, therefore, used wildtype male and female mice in diestrus or proestrus to analyze spines on dendritic segments from identified CA2 neurons. In basal stratum oriens, we found no differences in spine density, but a significant shift towards larger spine head areas in male mice compared to females. Conversely, in apical stratum radiatum diestrus females had a significantly higher spine density, and females in either cycle stage had a significant shift towards larger spine head areas as compared to males, with diestrus females showing the larger shift. Our results provide further evidence for the sexual dimorphism of hippocampal area CA2, and underscore the importance of considering not only the sex, but also the stage of the estrous cycle when interpreting morphological data.
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Affiliation(s)
- Sharif Jabra
- Institute of Clinical Neuroanatomy, Neuroscience Center, Goethe University Frankfurt, Theodor-Stern-Kai 7, 60590, Frankfurt am Main, Germany
| | - Michael Rietsche
- Institute of Clinical Neuroanatomy, Neuroscience Center, Goethe University Frankfurt, Theodor-Stern-Kai 7, 60590, Frankfurt am Main, Germany
| | - Julia Muellerleile
- Institute of Clinical Neuroanatomy, Neuroscience Center, Goethe University Frankfurt, Theodor-Stern-Kai 7, 60590, Frankfurt am Main, Germany
| | - Aet O'Leary
- Department of Psychiatry, Psychosomatic Medicine and Psychotherapy, Goethe University Frankfurt, University Hospital, Heinrich-Hoffmann-Straße 10, 60528, Frankfurt am Main, Germany
| | - David A Slattery
- Department of Psychiatry, Psychosomatic Medicine and Psychotherapy, Goethe University Frankfurt, University Hospital, Heinrich-Hoffmann-Straße 10, 60528, Frankfurt am Main, Germany
| | - Thomas Deller
- Institute of Clinical Neuroanatomy, Neuroscience Center, Goethe University Frankfurt, Theodor-Stern-Kai 7, 60590, Frankfurt am Main, Germany
| | - Meike Fellenz
- Institute of Clinical Neuroanatomy, Neuroscience Center, Goethe University Frankfurt, Theodor-Stern-Kai 7, 60590, Frankfurt am Main, Germany.
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Kassraian P, Bigler SK, Gilly DM, Shrotri N, Siegelbaum SA. A neural mechanism for discriminating social threat from social safety. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.07.04.547723. [PMID: 37461518 PMCID: PMC10350012 DOI: 10.1101/2023.07.04.547723] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/04/2023]
Abstract
The ability to distinguish a threatening from non-threatening conspecific based on past experience is critical for adaptive social behaviors. Although recent progress has been made in identifying the neural circuits that contribute to different types of positive and negative social interactions, the neural mechanisms that enable the discrimination of individuals based on past aversive experiences remain unknown. Here, we developed a modified social fear conditioning paradigm that induced in both sexes robust behavioral discrimination of a conspecific associated with a footshock (CS+) from a non-reinforced interaction partner (CS-). Strikingly, chemogenetic or optogenetic silencing of hippocampal CA2 pyramidal neurons, which have been previously implicated in social novelty recognition memory, resulted in generalized avoidance fear behavior towards the equally familiar CS-and CS+. One-photon calcium imaging revealed that the accuracy with which CA2 representations discriminate the CS+ from the CS-animal was enhanced following social fear conditioning and strongly correlated with behavioral discrimination. Moreover the CA2 representations incorporated a generalized or abstract representation of social valence irrespective of conspecific identity and location. Thus, our results demonstrate, for the first time, that the same hippocampal CA2 subregion mediates social memories based on conspecific familiarity and social threat, through the incorporation of a representation of social valence into an initial representation of social identity.
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Takeuchi Y, Yamashiro K, Noguchi A, Liu J, Mitsui S, Ikegaya Y, Matsumoto N. Machine learning-based segmentation of the rodent hippocampal CA2 area from Nissl-stained sections. Front Neuroanat 2023; 17:1172512. [PMID: 37449243 PMCID: PMC10336234 DOI: 10.3389/fnana.2023.1172512] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2023] [Accepted: 06/05/2023] [Indexed: 07/18/2023] Open
Abstract
The hippocampus is a center of learning, memory, and spatial navigation. This region is divided into the CA1, CA2, and CA3 areas, which are anatomically different from each other. Among these divisions, the CA2 area is unique in terms of functional relevance to sociality. The CA2 area is often manually detected based on the size, shape, and density of neurons in the hippocampal pyramidal cell layer, but this manual segmentation relying on cytoarchitecture is impractical to apply to a large number of samples and dependent on experimenters' proficiency. Moreover, the CA2 area has been defined based on expression pattern of molecular marker proteins, but it generally takes days to complete immunostaining for such proteins. Thus, we asked whether the CA2 area can be systematically segmented based on cytoarchitecture alone. Since the expression pattern of regulator of G-protein signaling 14 (RGS14) signifies the CA2 area, we visualized the CA2 area in the mouse hippocampus by RGS14-immunostaining and Nissl-counterstaining and manually delineated the CA2 area. We then established "CAseg," a machine learning-based automated algorithm to segment the CA2 area with the F1-score of approximately 0.8 solely from Nissl-counterstained images that visualized cytoarchitecture. CAseg was extended to the segmentation of the prairie vole CA2 area, which raises the possibility that the use of this algorithm can be expanded to other species. Thus, CAseg will be beneficial for investigating unique properties of the hippocampal CA2 area.
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Affiliation(s)
- Yuki Takeuchi
- Graduate School of Pharmaceutical Sciences, The University of Tokyo, Tokyo, Japan
| | - Kotaro Yamashiro
- Graduate School of Pharmaceutical Sciences, The University of Tokyo, Tokyo, Japan
| | - Asako Noguchi
- Graduate School of Pharmaceutical Sciences, The University of Tokyo, Tokyo, Japan
| | - Jiayan Liu
- Graduate School of Pharmaceutical Sciences, The University of Tokyo, Tokyo, Japan
| | - Shinichi Mitsui
- Department of Rehabilitation Sciences, Graduate School of Health Sciences, Gunma University, Maebashi, Gunma, Japan
| | - Yuji Ikegaya
- Graduate School of Pharmaceutical Sciences, The University of Tokyo, Tokyo, Japan
- Institute for AI and Beyond, The University of Tokyo, Tokyo, Japan
- Center for Information and Neural Networks, National Institute of Information and Communications Technology, Osaka, Japan
| | - Nobuyoshi Matsumoto
- Graduate School of Pharmaceutical Sciences, The University of Tokyo, Tokyo, Japan
- Institute for AI and Beyond, The University of Tokyo, Tokyo, Japan
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Samadi M, Hales CA, Lustberg DJ, Farris S, Ross MR, Zhao M, Hepler JR, Harbin NH, Robinson ESJ, Banks PJ, Bashir ZI, Dudek SM. Mechanisms of mGluR-dependent plasticity in hippocampal area CA2. Hippocampus 2023; 33:730-744. [PMID: 36971428 PMCID: PMC10213158 DOI: 10.1002/hipo.23529] [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: 02/18/2023] [Revised: 03/04/2023] [Accepted: 03/08/2023] [Indexed: 03/29/2023]
Abstract
Pyramidal cells in hippocampal area CA2 have synaptic properties that are distinct from the other CA subregions. Notably, this includes a lack of typical long-term potentiation of stratum radiatum synapses. CA2 neurons express high levels of several known and potential regulators of metabotropic glutamate receptor (mGluR)-dependent signaling including Striatal-Enriched Tyrosine Phosphatase (STEP) and several Regulator of G-protein Signaling (RGS) proteins, yet the functions of these proteins in regulating mGluR-dependent synaptic plasticity in CA2 are completely unknown. Thus, the aim of this study was to examine mGluR-dependent synaptic depression and to determine whether STEP and the RGS proteins RGS4 and RGS14 are involved. Using whole cell voltage-clamp recordings from mouse pyramidal cells, we found that mGluR agonist-induced long-term depression (mGluR-LTD) is more pronounced in CA2 compared with that observed in CA1. This mGluR-LTD in CA2 was found to be protein synthesis and STEP dependent, suggesting that CA2 mGluR-LTD shares mechanistic processes with those seen in CA1, but in addition, RGS14, but not RGS4, was essential for mGluR-LTD in CA2. In addition, we found that exogenous application of STEP could rescue mGluR-LTD in RGS14 KO slices. Supporting a role for CA2 synaptic plasticity in social cognition, we found that RGS14 KO mice had impaired social recognition memory as assessed in a social discrimination task. These results highlight possible roles for mGluRs, RGS14, and STEP in CA2-dependent behaviors, perhaps by biasing the dominant form of synaptic plasticity away from LTP and toward LTD in CA2.
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Affiliation(s)
- Mahsa Samadi
- School of Physiology, Pharmacology and Neuroscience, Biomedical Sciences BuildingUniversity Walk, University of BristolBristolUKBS8 1TD
- Neurobiology Laboratory, National Institute of Environmental Health Sciences (NIH)111 T.W. Alexander Drive, Research Triangle ParkDurhamNorth Carolina27709USA
- Present address:
Faculty Education Office, Faculty of Medicine, Imperial College London, Hammersmith Campus, Wolfson Education CentreLondonUKW12 0NN
| | - Claire A. Hales
- School of Physiology, Pharmacology and Neuroscience, Biomedical Sciences BuildingUniversity Walk, University of BristolBristolUKBS8 1TD
- Present address:
Department of Psychology, Djavad Mowafaghian Centre for Brain HealthUniversity of British Columbia2215, Wesbrook MallVancouverBritish ColumbiaV6T 1Z3Canada
| | - Daniel J. Lustberg
- Neurobiology Laboratory, National Institute of Environmental Health Sciences (NIH)111 T.W. Alexander Drive, Research Triangle ParkDurhamNorth Carolina27709USA
- Present address:
Mouse Pharmacology GroupPsychogenics Inc215 College RoadParamusNew Jersey07652USA
| | - Shannon Farris
- Neurobiology Laboratory, National Institute of Environmental Health Sciences (NIH)111 T.W. Alexander Drive, Research Triangle ParkDurhamNorth Carolina27709USA
- Present address:
Fralin Biomedical Research Institute at Virginia TechRoanokeVirginia24014USA
| | - Madeleine R. Ross
- Neurobiology Laboratory, National Institute of Environmental Health Sciences (NIH)111 T.W. Alexander Drive, Research Triangle ParkDurhamNorth Carolina27709USA
| | - Meilan Zhao
- Neurobiology Laboratory, National Institute of Environmental Health Sciences (NIH)111 T.W. Alexander Drive, Research Triangle ParkDurhamNorth Carolina27709USA
| | - John R. Hepler
- Department of Pharmacology and Chemical BiologyEmory University School of Medicine100 Woodruff CircleAtlantaGeorgia30322USA
| | - Nicholas H. Harbin
- Department of Pharmacology and Chemical BiologyEmory University School of Medicine100 Woodruff CircleAtlantaGeorgia30322USA
| | - Emma S. J. Robinson
- School of Physiology, Pharmacology and Neuroscience, Biomedical Sciences BuildingUniversity Walk, University of BristolBristolUKBS8 1TD
| | - Paul J. Banks
- School of Physiology, Pharmacology and Neuroscience, Biomedical Sciences BuildingUniversity Walk, University of BristolBristolUKBS8 1TD
| | - Zafar I. Bashir
- School of Physiology, Pharmacology and Neuroscience, Biomedical Sciences BuildingUniversity Walk, University of BristolBristolUKBS8 1TD
| | - Serena M. Dudek
- Neurobiology Laboratory, National Institute of Environmental Health Sciences (NIH)111 T.W. Alexander Drive, Research Triangle ParkDurhamNorth Carolina27709USA
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6
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Harbin NH, Lustberg DJ, Hurst C, Pare J, Crotty KM, Waters AL, Yeligar SM, Smith Y, Seyfried NT, Weinshenker D, Hepler JR. RGS14 limits seizure-induced mitochondrial oxidative stress and pathology in hippocampus. Neurobiol Dis 2023; 181:106128. [PMID: 37075948 PMCID: PMC10259180 DOI: 10.1016/j.nbd.2023.106128] [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: 01/31/2023] [Revised: 04/02/2023] [Accepted: 04/14/2023] [Indexed: 04/21/2023] Open
Abstract
RGS14 is a complex multifunctional scaffolding protein that is highly enriched within pyramidal cells (PCs) of hippocampal area CA2. In these neurons, RGS14 suppresses glutamate-induced calcium influx and related G protein and ERK signaling in dendritic spines to restrain postsynaptic signaling and plasticity. Previous findings show that, unlike PCs of hippocampal areas CA1 and CA3, CA2 PCs are resistant to a number of neurological insults, including degeneration caused by temporal lobe epilepsy (TLE). While RGS14 is protective against peripheral injury, similar roles for RGS14 during pathological injury in hippocampus remain unexplored. Recent studies showed that area CA2 modulates hippocampal excitability, generates epileptiform activity and promotes hippocampal pathology in animal models and patients with TLE. Because RGS14 suppresses CA2 excitability and signaling, we hypothesized that RGS14 would moderate seizure behavior and early hippocampal pathology following seizure activity, possibly affording protection to CA2 PCs. Using kainic acid (KA) to induce status epilepticus (KA-SE) in mice, we show that the loss of RGS14 (RGS14 KO) accelerated onset of limbic motor seizures and mortality compared to wild type (WT) mice, and that KA-SE upregulated RGS14 protein expression in CA2 and CA1 PCs of WT. Our proteomics data show that the loss of RGS14 impacted the expression of a number of proteins at baseline and after KA-SE, many of which associated unexpectedly with mitochondrial function and oxidative stress. RGS14 was shown to localize to the mitochondria in CA2 PCs of mice and reduce mitochondrial respiration in vitro. As a readout of oxidative stress, we found that RGS14 KO dramatically increased 3- nitrotyrosine levels in CA2 PCs, which was greatly exacerbated following KA-SE and correlated with a lack of superoxide dismutase 2 (SOD2) induction. Assessing for hallmarks of seizure pathology in RGS14 KO, we unexpectedly found no differences in neuronal injury in CA2 PCs. However, we observed a striking and surprising lack of microgliosis in CA1 and CA2 of RGS14 KO compared to WT. Together, our data demonstrate a newly appreciated role for RGS14 in limiting intense seizure activity and pathology in hippocampus. Our findings are consistent with a model where RGS14 limits seizure onset and mortality and, after seizure, is upregulated to support mitochondrial function, prevent oxidative stress in CA2 PCs, and promote microglial activation in hippocampus.
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Affiliation(s)
- N H Harbin
- Department of Pharmacology and Chemical Biology, Emory University School of Medicine, 1510 Clifton Rd, 5001 Rollins Research Ctr, Atlanta, GA 30322, United States.
| | - D J Lustberg
- Department of Human Genetics, Emory University School of Medicine, 615 Michael Street, Suite 301, Atlanta, GA 30322, United States
| | - C Hurst
- Department of Biochemistry, Emory University School of Medicine, 1510 Clifton Rd, 4001 Rollins Research Center, Atlanta, GA 30322, United States.
| | - J Pare
- Emory National Primate Research Center, Emory University, 954, Gatewood Rd NE, Atlanta, GA 30329, United States.
| | - K M Crotty
- Department of Medicine, Division of Pulmonary, Allergy, Critical Care and Sleep Medicine, Emory University, 1364 Clifton Road NE, Suite H-153, Atlanta, GA 30322, United States; Atlanta Veterans Affairs Health Care System, 1670 Clairmont Road, Decatur, GA 30033, United States.
| | - A L Waters
- Department of Pharmacology and Chemical Biology, Emory University School of Medicine, 1510 Clifton Rd, 5001 Rollins Research Ctr, Atlanta, GA 30322, United States.
| | - S M Yeligar
- Department of Medicine, Division of Pulmonary, Allergy, Critical Care and Sleep Medicine, Emory University, 1364 Clifton Road NE, Suite H-153, Atlanta, GA 30322, United States; Atlanta Veterans Affairs Health Care System, 1670 Clairmont Road, Decatur, GA 30033, United States.
| | - Y Smith
- Emory National Primate Research Center, Emory University, 954, Gatewood Rd NE, Atlanta, GA 30329, United States; Department of Neurology, Emory University School of Medicine, 12 Executive Park Dr NE, Atlanta, GA, 30322, United States.
| | - N T Seyfried
- Department of Biochemistry, Emory University School of Medicine, 1510 Clifton Rd, 4001 Rollins Research Center, Atlanta, GA 30322, United States.
| | - D Weinshenker
- Department of Human Genetics, Emory University School of Medicine, 615 Michael Street, Suite 301, Atlanta, GA 30322, United States.
| | - J R Hepler
- Department of Pharmacology and Chemical Biology, Emory University School of Medicine, 1510 Clifton Rd, 5001 Rollins Research Ctr, Atlanta, GA 30322, United States.
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7
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Montanez-Miranda C, Bramlett SN, Hepler JR. RGS14 expression in CA2 hippocampus, amygdala, and basal ganglia: Implications for human brain physiology and disease. Hippocampus 2023; 33:166-181. [PMID: 36541898 PMCID: PMC9974931 DOI: 10.1002/hipo.23492] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2022] [Revised: 11/09/2022] [Accepted: 12/07/2022] [Indexed: 12/24/2022]
Abstract
RGS14 is a multifunctional scaffolding protein that is highly expressed within postsynaptic spines of pyramidal neurons in hippocampal area CA2. Known roles of RGS14 in CA2 include regulating G protein, H-Ras/ERK, and calcium signaling pathways to serve as a natural suppressor of synaptic plasticity and postsynaptic signaling. RGS14 also shows marked postsynaptic expression in major structures of the limbic system and basal ganglia, including the amygdala and both the ventral and dorsal subdivisions of the striatum. In this review, we discuss the signaling functions of RGS14 and its role in postsynaptic strength (long-term potentiation) and spine structural plasticity in CA2 hippocampal neurons, and how RGS14 suppression of plasticity impacts linked behaviors such as spatial learning, object memory, and fear conditioning. We also review RGS14 expression in the limbic system and basal ganglia and speculate on its possible roles in regulating plasticity in these regions, with a focus on behaviors related to emotion and motivation. Finally, we explore the functional implications of RGS14 in various brain circuits and speculate on its possible roles in certain disease states such as hippocampal seizures, addiction, and anxiety disorders.
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Affiliation(s)
| | | | - John R. Hepler
- Department of Pharmacology and Chemical Biology, Emory University School of Medicine, Atlanta, GA, 30322-3090
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8
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Dudek SM, Alexander GM, Farris S. Introduction to the special issue on: A new view of hippocampal area CA2. Hippocampus 2023; 33:127-132. [PMID: 36826426 DOI: 10.1002/hipo.23514] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/31/2023] [Indexed: 02/25/2023]
Affiliation(s)
- Serena M Dudek
- Neurobiology Laboratory, National Institute of Environmental Health Sciences, National Institute of Health, Research Triangle Park, North Carolina, USA
| | - Georgia M Alexander
- Neurobiology Laboratory, National Institute of Environmental Health Sciences, National Institute of Health, Research Triangle Park, North Carolina, USA
| | - Shannon Farris
- Center for Neurobiology Research, Fralin Biomedical Research Institute, Virginia Tech Carilion, Roanoke, Virginia, USA
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9
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Radzicki D, Chong S, Dudek SM. Morphological and molecular markers of mouse area CA2 along the proximodistal and dorsoventral hippocampal axes. Hippocampus 2023; 33:133-149. [PMID: 36762588 PMCID: PMC10443601 DOI: 10.1002/hipo.23509] [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: 11/08/2022] [Revised: 01/20/2023] [Accepted: 01/23/2023] [Indexed: 02/11/2023]
Abstract
Hippocampal area CA2 is a molecularly and functionally distinct region of the hippocampus that has classically been defined as the area with large pyramidal neurons lacking input from the dentate gyrus and the thorny excrescences (TEs) characteristic of CA3 neurons. A modern definition of CA2, however, makes use of the expression of several molecular markers that distinguish it from neighboring CA3 and CA1. Using immunohistochemistry, we sought to characterize the staining patterns of commonly used CA2 markers along the dorsal-ventral hippocampal axis and determine how these markers align along the proximodistal axis. We used a region of CA2 that stained for both Regulator of G-protein Signaling 14 (RGS14) and Purkinje Cell Protein 4 (PCP4; "double-labeled zone" [DLZ]) as a reference. Here, we report that certain commonly used CA2 molecular markers may be better suited for drawing distinct boundaries between CA2/3 and CA2/1. For example, RGS14+ and STEP+ neurons showed minimal to no extension into area CA1 while areas stained with VGluT2 and Wisteria Floribunda agglutinin were consistently smaller than the DLZ/CA2 borders by ~100 μ on the CA1 or CA3 sides respectively. In addition, these patterns are dependent on position along the dorsal-ventral hippocampal axis such that PCP4 labeling often extended beyond the distal border of the DLZ into CA1. Finally, we found that, consistent with previous findings, mossy fibers innervate a subset of RGS14 positive neurons (~65%-70%) and that mossy fiber bouton number and relative size in CA2 are less than that of boutons in CA3. Unexpectedly, we did find evidence of some complex spines on apical dendrites in CA2, though much fewer in number than in CA3. Our results indicate that certain molecular markers may be better suited than others when defining the proximal and distal borders of area CA2 and that the presence or absence of complex spines alone may not be suitable as a distinguishing feature differentiating CA3 from CA2 neurons.
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Affiliation(s)
- Daniel Radzicki
- Neurobiology Laboratory, National Institute of Environmental Health SciencesNational Institute of HealthResearch Triangle ParkNorth CarolinaUSA
| | - Sarah Chong
- Neurobiology Laboratory, National Institute of Environmental Health SciencesNational Institute of HealthResearch Triangle ParkNorth CarolinaUSA
| | - Serena M. Dudek
- Neurobiology Laboratory, National Institute of Environmental Health SciencesNational Institute of HealthResearch Triangle ParkNorth CarolinaUSA
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10
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Bienkowski MS. Further refining the boundaries of the hippocampus CA2 with gene expression and connectivity: Potential subregions and heterogeneous cell types. Hippocampus 2023; 33:150-160. [PMID: 36786207 PMCID: PMC9987718 DOI: 10.1002/hipo.23508] [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: 10/11/2022] [Revised: 01/20/2023] [Accepted: 01/23/2023] [Indexed: 02/15/2023]
Abstract
Over the last two decades, the definition of hippocampal area CA2 has evolved from Lorente de Nó's original Golgi-based morphological description with the discovery of specific CA2 gene expression markers. Exploiting the specificity of these molecules has allowed for the genetic dissection of CA2 structure and function in transgenic mice. With this change in criteria, the anatomical boundaries of the CA2 have expanded across the hippocampal axis but the CA2's full rostrocaudal extent is not consistently delineated across atlases. The Hippocampus Gene Expression Atlas (HGEA) provides a comprehensive map of 20 gene expression domains across the entire mouse hippocampus including the CA2. In this commentary, I will review the consensus gene expression patterns that demarcate the expanded CA2 boundaries in the HGEA. Using DropViz single-cell transcriptomics and Mouse Connectome Project connectomics data, I will then suggest potential differences in CA2 cell type heterogeneity and connectivity that may identify and characterize further CA2 subregions.
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Affiliation(s)
- Michael S Bienkowski
- USC Mark and Mary Stevens Neuroimaging and Informatics Institute, Keck School of Medicine of USC, University of Southern California, Los Angeles, California, USA
- Zilkha Neurogenetic Institute, Keck School of Medicine of University of Southern California, Los Angeles, California, USA
- USC Center for Integrative Connectomics, Keck School of Medicine of University of Southern California, Los Angeles, CA, USA
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11
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Harbin NH, Lustberg DJ, Hurst C, Pare JF, Crotty KM, Waters AL, Yeligar SM, Smith Y, Seyfried NT, Weinshenker D, Hepler JR. RGS14 is neuroprotective against seizure-induced mitochondrial oxidative stress and pathology in hippocampus. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.02.01.526349. [PMID: 36778349 PMCID: PMC9915580 DOI: 10.1101/2023.02.01.526349] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
RGS14 is a complex multifunctional scaffolding protein that is highly enriched within pyramidal cells (PCs) of hippocampal area CA2. There, RGS14 suppresses glutamate-induced calcium influx and related G protein and ERK signaling in dendritic spines to restrain postsynaptic signaling and plasticity. Previous findings show that, unlike PCs of hippocampal areas CA1 and CA3, CA2 PCs are resistant to a number of neurological insults, including degeneration caused by temporal lobe epilepsy (TLE). While RGS14 is protective against peripheral injury, similar roles for RGS14 during pathological injury in hippocampus remain unexplored. Recent studies show that area CA2 modulates hippocampal excitability, generates epileptiform activity and promotes hippocampal pathology in animal models and patients with TLE. Because RGS14 suppresses CA2 excitability and signaling, we hypothesized that RGS14 would moderate seizure behavior and early hippocampal pathology following seizure activity. Using kainic acid (KA) to induce status epilepticus (KA-SE) in mice, we show loss of RGS14 (RGS14 KO) accelerated onset of limbic motor seizures and mortality compared to wild type (WT) mice, and that KA-SE upregulated RGS14 protein expression in CA2 and CA1 PCs of WT. Utilizing proteomics, we saw loss of RGS14 impacted the expression of a number of proteins at baseline and after KA-SE, many of which associated unexpectedly with mitochondrial function and oxidative stress. RGS14 was shown to localize to the mitochondria in CA2 PCs of mice and reduce mitochondrial respiration in vitro . As a readout of oxidative stress, we found RGS14 KO dramatically increased 3-nitrotyrosine levels in CA2 PCs, which was greatly exacerbated following KA-SE and correlated with a lack of superoxide dismutase 2 (SOD2) induction. Assessing for hallmarks of seizure pathology in RGS14 KO, we observed worse neuronal injury in area CA3 (but none in CA2 or CA1), and a lack of microgliosis in CA1 and CA2 compared to WT. Together, our data demonstrates a newly appreciated neuroprotective role for RGS14 against intense seizure activity in hippocampus. Our findings are consistent with a model where, after seizure, RGS14 is upregulated to support mitochondrial function and prevent oxidative stress in CA2 PCs, limit seizure onset and hippocampal neuronal injury, and promote microglial activation in hippocampus.
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12
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Sachella TE, Ihidoype MR, Proulx CD, Pafundo DE, Medina JH, Mendez P, Piriz J. A novel role for the lateral habenula in fear learning. Neuropsychopharmacology 2022; 47:1210-1219. [PMID: 35217797 PMCID: PMC9018839 DOI: 10.1038/s41386-022-01294-5] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/11/2021] [Revised: 02/06/2022] [Accepted: 02/08/2022] [Indexed: 02/02/2023]
Abstract
Fear is an extreme form of aversion that underlies pathological conditions such as panic or phobias. Fear conditioning (FC) is the best-understood model of fear learning. In FC the context and a cue are independently associated with a threatening unconditioned stimulus (US). The lateral habenula (LHb) is a general encoder of aversion. However, its role in fear learning remains poorly understood. Here we studied in rats the role of the LHb in FC using optogenetics and pharmacological tools. We found that inhibition or activation of the LHb during entire FC training impaired both cued and contextual FC. In contrast, optogenetic inhibition of the LHb restricted to cue and US presentation impaired cued but not contextual FC. In either case, simultaneous activation of contextual and cued components of FC, by the presentation of the cue in the training context, recovered the conditioned fear response. Our results support the notion that the LHb is required for the formation of independent contextual and cued fear memories, a previously uncharacterized function for this structure, that could be critical in fear generalization.
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Affiliation(s)
- Tomas E. Sachella
- grid.423606.50000 0001 1945 2152Instituto de Fisiología y Biofísica “Bernardo Houssay” (IFIBIO-Houssay), Grupo de Neurociencia de Sistemas, Universidad de Buenos Aires y Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Buenos Aires, Argentina
| | - Marina R. Ihidoype
- grid.423606.50000 0001 1945 2152Instituto de Fisiología y Biofísica “Bernardo Houssay” (IFIBIO-Houssay), Grupo de Neurociencia de Sistemas, Universidad de Buenos Aires y Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Buenos Aires, Argentina
| | - Christophe D. Proulx
- grid.23856.3a0000 0004 1936 8390CERVO Brain Research Center, Department of Psychiatry and Neurosciences, Université Laval, Quebec City, Quebec Canada
| | - Diego E. Pafundo
- grid.423606.50000 0001 1945 2152Instituto de Fisiología y Biofísica “Bernardo Houssay” (IFIBIO-Houssay), Grupo de Neurociencia de Sistemas, Universidad de Buenos Aires y Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Buenos Aires, Argentina
| | - Jorge H. Medina
- grid.423606.50000 0001 1945 2152Instituto de Biología Celular y Neurociencia “Prof. E. De Robertis” (IBCN), Universidad de Buenos Aires y Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Buenos Aires, Argentina ,grid.441574.70000000090137393Instituto Tecnológico de Buenos Aires (ITBA), Buenos Aires, Argentina
| | - Pablo Mendez
- grid.419043.b0000 0001 2177 5516Instituto Cajal, CSIC, Madrid, España
| | - Joaquin Piriz
- Instituto de Fisiología y Biofísica "Bernardo Houssay" (IFIBIO-Houssay), Grupo de Neurociencia de Sistemas, Universidad de Buenos Aires y Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Buenos Aires, Argentina. .,Instituto de Fisiología Biología Molecular y Neurociencias (IFIBYNE), Universidad de Buenos Aires y Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Buenos Aires, Argentina.
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13
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Foster SL, Lustberg DJ, Harbin NH, Bramlett SN, Hepler JR, Weinshenker D. RGS14 modulates locomotor behavior and ERK signaling induced by environmental novelty and cocaine within discrete limbic structures. Psychopharmacology (Berl) 2021; 238:2755-2773. [PMID: 34184126 PMCID: PMC8455459 DOI: 10.1007/s00213-021-05892-x] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/21/2021] [Accepted: 06/01/2021] [Indexed: 12/14/2022]
Abstract
RATIONALE In rodents, exposure to novel environments or psychostimulants promotes locomotion. Indeed, locomotor reactivity to novelty strongly predicts behavioral responses to psychostimulants in animal models of addiction. RGS14 is a plasticity-restricting protein with unique functional domains that enable it to suppress ERK-dependent signaling as well as regulate G protein activity. Although recent studies show that RGS14 is expressed in multiple limbic regions implicated in psychostimulant- and novelty-induced hyperlocomotion, its function has been examined mostly in the context of hippocampal physiology and memory. OBJECTIVE We investigated whether RGS14 modulates novelty- and cocaine-induced locomotion (NIL and CIL, respectively) and neuronal activity. METHODS We assessed Rgs14 knockout (RGS14 KO) mice and wild-type (WT) littermate controls using NIL and CIL behavioral tests, followed by quantification of c-fos and phosphorylated ERK (pERK) induction in limbic regions that normally express RGS14. RESULTS RGS14 KO mice were less active than WT controls in the NIL test, driven by avoidance of the center of the novel environment. By contrast, RGS14 KO mice demonstrated augmented peripheral locomotion in the CIL test conducted in either a familiar or novel environment. RGS14 KO mice exhibited increased thigmotaxis, as well as greater c-fos and pERK induction in the central amygdala and dorsal hippocampus, when cocaine and novelty were paired. CONCLUSIONS RGS14 KO mice exhibited anti-correlated locomotor responses to novelty and cocaine, but displayed increased thigmotaxis in response to either stimuli which was augmented by their combination. Our findings also suggest RGS14 may reduce neuronal activity in limbic subregions by inhibiting ERK-dependent signaling.
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Affiliation(s)
- Stephanie L Foster
- , Department of Human Genetics, Emory University School of Medicine, 615 Michael St., Whitehead 301, Atlanta, GA, 30322, USA
| | - Daniel J Lustberg
- , Department of Human Genetics, Emory University School of Medicine, 615 Michael St., Whitehead 301, Atlanta, GA, 30322, USA
| | - Nicholas H Harbin
- Department of Pharmacology and Chemical Biology, Emory University School of Medicine, 1510 Clifton Rd, Atlanta, GA, 30322, USA
| | - Sara N Bramlett
- Department of Pharmacology and Chemical Biology, Emory University School of Medicine, 1510 Clifton Rd, Atlanta, GA, 30322, USA
| | - John R Hepler
- Department of Pharmacology and Chemical Biology, Emory University School of Medicine, 1510 Clifton Rd, Atlanta, GA, 30322, USA.
| | - David Weinshenker
- , Department of Human Genetics, Emory University School of Medicine, 615 Michael St., Whitehead 301, Atlanta, GA, 30322, USA.
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14
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RGS14 Regulation of Post-Synaptic Signaling and Spine Plasticity in Brain. Int J Mol Sci 2021; 22:ijms22136823. [PMID: 34201943 PMCID: PMC8268017 DOI: 10.3390/ijms22136823] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2021] [Revised: 06/12/2021] [Accepted: 06/14/2021] [Indexed: 02/06/2023] Open
Abstract
The regulator of G-protein signaling 14 (RGS14) is a multifunctional signaling protein that regulates post synaptic plasticity in neurons. RGS14 is expressed in the brain regions essential for learning, memory, emotion, and stimulus-induced behaviors, including the basal ganglia, limbic system, and cortex. Behaviorally, RGS14 regulates spatial and object memory, female-specific responses to cued fear conditioning, and environmental- and psychostimulant-induced locomotion. At the cellular level, RGS14 acts as a scaffolding protein that integrates G protein, Ras/ERK, and calcium/calmodulin signaling pathways essential for spine plasticity and cell signaling, allowing RGS14 to naturally suppress long-term potentiation (LTP) and structural plasticity in hippocampal area CA2 pyramidal cells. Recent proteomics findings indicate that RGS14 also engages the actomyosin system in the brain, perhaps to impact spine morphogenesis. Of note, RGS14 is also a nucleocytoplasmic shuttling protein, where its role in the nucleus remains uncertain. Balanced nuclear import/export and dendritic spine localization are likely essential for RGS14 neuronal functions as a regulator of synaptic plasticity. Supporting this idea, human genetic variants disrupting RGS14 localization also disrupt RGS14’s effects on plasticity. This review will focus on the known and unexplored roles of RGS14 in cell signaling, physiology, disease and behavior.
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15
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Bin Ibrahim MZ, Benoy A, Sajikumar S. Long-term plasticity in the hippocampus: maintaining within and 'tagging' between synapses. FEBS J 2021; 289:2176-2201. [PMID: 34109726 DOI: 10.1111/febs.16065] [Citation(s) in RCA: 32] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2021] [Revised: 05/15/2021] [Accepted: 06/01/2021] [Indexed: 12/11/2022]
Abstract
Synapses between neurons are malleable biochemical structures, strengthening and diminishing over time dependent on the type of information they receive. This phenomenon known as synaptic plasticity underlies learning and memory, and its different forms, long-term potentiation (LTP) and long-term depression (LTD), perform varied cognitive roles in reinforcement, relearning and associating memories. Moreover, both LTP and LTD can exist in an early transient form (early-LTP/LTD) or a late persistent form (late-LTP/LTD), which are triggered by different induction protocols, and also differ in their dependence on protein synthesis and the involvement of key molecular players. Beyond homosynaptic modifications, synapses can also interact with one another. This is encapsulated in the synaptic tagging and capture hypothesis (STC), where synapses expressing early-LTP/LTD present a 'tag' that can capture the protein synthesis products generated during a temporally proximal late-LTP/LTD induction. This 'tagging' phenomenon forms the framework of synaptic interactions in various conditions and accounts for the cellular basis of the time-dependent associativity of short-lasting and long-lasting memories. All these synaptic modifications take place under controlled neuronal conditions, regulated by subcellular elements such as epigenetic regulation, proteasomal degradation and neuromodulatory signals. Here, we review current understanding of the different forms of synaptic plasticity and its regulatory mechanisms in the hippocampus, a brain region critical for memory formation. We also discuss expression of plasticity in hippocampal CA2 area, a long-overlooked narrow hippocampal subfield and the behavioural correlate of STC. Lastly, we put forth perspectives for an integrated view of memory representation in synapses.
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Affiliation(s)
- Mohammad Zaki Bin Ibrahim
- Department of Physiology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore.,Life Sciences Institute Neurobiology Programme, National University of Singapore, Singapore
| | - Amrita Benoy
- Department of Physiology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore.,Life Sciences Institute Neurobiology Programme, National University of Singapore, Singapore
| | - Sreedharan Sajikumar
- Department of Physiology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore.,Life Sciences Institute Neurobiology Programme, National University of Singapore, Singapore.,Healthy Longevity Translational Research Programme, Yong Loo Lin School of Medicine, National University of Singapore, Singapore
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16
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Lehr AB, Kumar A, Tetzlaff C, Hafting T, Fyhn M, Stöber TM. CA2 beyond social memory: Evidence for a fundamental role in hippocampal information processing. Neurosci Biobehav Rev 2021; 126:398-412. [PMID: 33775693 DOI: 10.1016/j.neubiorev.2021.03.020] [Citation(s) in RCA: 24] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2020] [Revised: 03/16/2021] [Accepted: 03/18/2021] [Indexed: 01/16/2023]
Abstract
Hippocampal region CA2 has received increased attention due to its importance in social recognition memory. While its specific function remains to be identified, there are indications that CA2 plays a major role in a variety of situations, widely extending beyond social memory. In this targeted review, we highlight lines of research which have begun to converge on a more fundamental role for CA2 in hippocampus-dependent memory processing. We discuss recent proposals that speak to the computations CA2 may perform within the hippocampal circuit.
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Affiliation(s)
- Andrew B Lehr
- Department of Computational Neuroscience, University of Göttingen, Germany; Bernstein Center for Computational Neuroscience, University of Göttingen, Germany; Department of Computational Physiology, Simula Research Laboratory, Lysaker, Norway; Centre for Integrative Neuroplasticity, University of Oslo, Norway.
| | - Arvind Kumar
- Department of Computational Science and Technology, KTH Royal Institute of Technology, Sweden
| | - Christian Tetzlaff
- Department of Computational Neuroscience, University of Göttingen, Germany; Bernstein Center for Computational Neuroscience, University of Göttingen, Germany
| | - Torkel Hafting
- Centre for Integrative Neuroplasticity, University of Oslo, Norway; Institute of Basic Medical Sciences, University of Oslo, Norway
| | - Marianne Fyhn
- Centre for Integrative Neuroplasticity, University of Oslo, Norway; Department of Biosciences, University of Oslo, Norway
| | - Tristan M Stöber
- Department of Computational Physiology, Simula Research Laboratory, Lysaker, Norway; Centre for Integrative Neuroplasticity, University of Oslo, Norway; Department of Informatics, University of Oslo, Norway.
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17
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Lunardi P, Mansk LMZ, Jaimes LF, Pereira GS. On the novel mechanisms for social memory and the emerging role of neurogenesis. Brain Res Bull 2021; 171:56-66. [PMID: 33753208 DOI: 10.1016/j.brainresbull.2021.03.006] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2020] [Revised: 02/24/2021] [Accepted: 03/08/2021] [Indexed: 01/25/2023]
Abstract
Social memory (SM) is a key element in social cognition and it encompasses the neural representation of conspecifics, an essential information to guide behavior in a social context. Here we evaluate classical and cutting-edge studies on neurobiology of SM, using as a guiding principle behavioral tasks performed in adult rodents. Our review highlights the relevance of the hippocampus, especially the CA2 region, as a neural substrate for SM and suggest that neural ensembles in the olfactory bulb may also encode SM traces. Compared to other hippocampus-dependent memories, much remains to be done to describe the neurobiological foundations of SM. Nonetheless, we argue that special attention should be paid to neurogenesis. Finally, we pinpoint the remaining open question on whether the hippocampal adult neurogenesis acts through pattern separation to permit the discrimination of highly similar stimuli during behavior.
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Affiliation(s)
- Paula Lunardi
- Núcleo de Neurociências, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Belo Horizonte, Brazil
| | - Lara M Z Mansk
- Núcleo de Neurociências, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Belo Horizonte, Brazil
| | - Laura F Jaimes
- Núcleo de Neurociências, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Belo Horizonte, Brazil
| | - Grace S Pereira
- Núcleo de Neurociências, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Belo Horizonte, Brazil.
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18
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Squires KE, Gerber KJ, Tillman MC, Lustberg DJ, Montañez-Miranda C, Zhao M, Ramineni S, Scharer CD, Saha RN, Shu FJ, Schroeder JP, Ortlund EA, Weinshenker D, Dudek SM, Hepler JR. Human genetic variants disrupt RGS14 nuclear shuttling and regulation of LTP in hippocampal neurons. J Biol Chem 2021; 296:100024. [PMID: 33410399 PMCID: PMC7949046 DOI: 10.1074/jbc.ra120.016009] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2020] [Revised: 10/26/2020] [Accepted: 11/04/2020] [Indexed: 12/13/2022] Open
Abstract
The human genome contains vast genetic diversity as naturally occurring coding variants, yet the impact of these variants on protein function and physiology is poorly understood. RGS14 is a multifunctional signaling protein that suppresses synaptic plasticity in dendritic spines of hippocampal neurons. RGS14 also is a nucleocytoplasmic shuttling protein, suggesting that balanced nuclear import/export and dendritic spine localization are essential for RGS14 functions. We identified genetic variants L505R (LR) and R507Q (RQ) located within the nuclear export sequence (NES) of human RGS14. Here we report that RGS14 encoding LR or RQ profoundly impacts protein functions in hippocampal neurons. RGS14 membrane localization is regulated by binding Gαi-GDP, whereas RGS14 nuclear export is regulated by Exportin 1 (XPO1). Remarkably, LR and RQ variants disrupt RGS14 binding to Gαi1-GDP and XPO1, nucleocytoplasmic equilibrium, and capacity to inhibit long-term potentiation (LTP). Variant LR accumulates irreversibly in the nucleus, preventing RGS14 binding to Gαi1, localization to dendritic spines, and inhibitory actions on LTP induction, while variant RQ exhibits a mixed phenotype. When introduced into mice by CRISPR/Cas9, RGS14-LR protein expression was detected predominantly in the nuclei of neurons within hippocampus, central amygdala, piriform cortex, and striatum, brain regions associated with learning and synaptic plasticity. Whereas mice completely lacking RGS14 exhibit enhanced spatial learning, mice carrying variant LR exhibit normal spatial learning, suggesting that RGS14 may have distinct functions in the nucleus independent from those in dendrites and spines. These findings show that naturally occurring genetic variants can profoundly alter normal protein function, impacting physiology in unexpected ways.
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Affiliation(s)
- Katherine E Squires
- Department of Pharmacology and Chemical Biology, Emory University, Atlanta Georgia, USA
| | - Kyle J Gerber
- Department of Pharmacology and Chemical Biology, Emory University, Atlanta Georgia, USA
| | | | - Daniel J Lustberg
- Department of Human Genetics, Emory University, Atlanta Georgia, USA
| | | | - Meilan Zhao
- National Institute of Environmental Health Sciences, Research Triangle Park, Raleigh North Carolina, USA
| | - Suneela Ramineni
- Department of Pharmacology and Chemical Biology, Emory University, Atlanta Georgia, USA
| | | | - Ramendra N Saha
- Department of Molecular & Cell Biology, University of California-Merced, Merced California, USA
| | - Feng-Jue Shu
- Department of Pharmacology and Chemical Biology, Emory University, Atlanta Georgia, USA
| | - Jason P Schroeder
- Department of Human Genetics, Emory University, Atlanta Georgia, USA
| | - Eric A Ortlund
- Department of Biochemistry, Emory University, Atlanta Georgia, USA
| | - David Weinshenker
- Department of Human Genetics, Emory University, Atlanta Georgia, USA
| | - Serena M Dudek
- National Institute of Environmental Health Sciences, Research Triangle Park, Raleigh North Carolina, USA
| | - John R Hepler
- Department of Pharmacology and Chemical Biology, Emory University, Atlanta Georgia, USA.
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19
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Aplnr knockout mice display sex-specific changes in conditioned fear. Behav Brain Res 2020; 400:113059. [PMID: 33309737 DOI: 10.1016/j.bbr.2020.113059] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2020] [Revised: 12/04/2020] [Accepted: 12/05/2020] [Indexed: 11/23/2022]
Abstract
The G-protein-coupled receptor APLNR and its ligands apelin and ELABELA/TODDLER/apela comprise the apelinergic system, a signaling pathway that is critical during development and physiological homeostasis. Targeted regulation of the receptor has been proposed to treat several important diseases including heart failure, pulmonary arterial hypertension and metabolic syndrome. The apelinergic system is widely expressed within the central nervous system (CNS). However, the role of this system in the CNS has not been completely elucidated. Utilizing an Aplnr knockout mouse model, we report here results from tests of sensory ability, locomotion, reward preference, social preference, learning and memory, and anxiety. We find that knockout of Aplnr leads to significant effects on acoustic startle response and sex-specific effects on conditioned fear responses without significant changes in baseline anxiety. In particular, male Aplnr knockout mice display enhanced context- and cue-dependent fear responses. Our results complement previous reports that exogenous Apelin administration reduced conditioned fear and freezing responses in rodent models, and future studies will explore the therapeutic benefit of APLNR-targeted drugs in rodent models of PTSD.
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20
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Williams Avram SK, Lee HJ, Fastman J, Cymerblit-Sabba A, Smith A, Vincent M, Song J, Granovetter MC, Lee SH, Cilz NI, Stackmann M, Chaturvedi R, Young WS. NMDA Receptor in Vasopressin 1b Neurons Is Not Required for Short-Term Social Memory, Object Memory or Aggression. Front Behav Neurosci 2019; 13:218. [PMID: 31787886 PMCID: PMC6856057 DOI: 10.3389/fnbeh.2019.00218] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2019] [Accepted: 09/05/2019] [Indexed: 12/20/2022] Open
Abstract
The arginine vasopressin 1b receptor (Avpr1b) plays an important role in social behaviors including aggression, social learning and memory. Genetic removal of Avpr1b from mouse models results in deficits in aggression and short-term social recognition in adults. Avpr1b gene expression is highly enriched in the pyramidal neurons of the hippocampal cornu ammonis 2 (CA2) region. Activity of the hippocampal CA2 has been shown to be required for normal short-term social recognition and aggressive behaviors. Vasopressin acts to enhance synaptic responses of CA2 neurons through a NMDA-receptor dependent mechanism. Genetic removal of the obligatory subunit of the NMDA receptor (Grin1) within distinct hippocampal regions impairs non-social learning and memory. However, the question of a direct role for NMDA receptor activity in Avpr1b neurons to modulate social behavior remains unclear. To answer this question, we first created a novel transgenic mouse line with Cre recombinase knocked into the Avpr1b coding region to genetically target Avpr1b neurons. We confirmed this line has dense Cre expression throughout the dorsal and ventral CA2 regions of the hippocampus, along with scattered expression within the caudate-putamen and olfactory bulb (OB). Conditional removal of the NMDA receptor was achieved by crossing our line to an available floxed Grin1 line. The resulting mice were measured on a battery of social and memory behavioral tests. Surprisingly, we did not observe any differences between Avpr1b-Grin1 knockout mice and their wildtype siblings. We conclude that mice without typical NMDA receptor function in Avpr1b neurons can develop normal aggression as well as short-term social and object memory performance.
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Affiliation(s)
- Sarah K Williams Avram
- Section on Neural Gene Expression, National Institute of Mental Health, National Institutes of Health, Bethesda, MD, United States.,Systems Neuroscience Imaging Resource, Intramural Research Program, National Institute of Mental Health, National Institutes of Health, Bethesda, MD, United States
| | - Heon-Jin Lee
- Section on Neural Gene Expression, National Institute of Mental Health, National Institutes of Health, Bethesda, MD, United States.,Department of Microbiology and Immunology, School of Dentistry, Kyungpook National University, Daegu, South Korea
| | - Jarrett Fastman
- Section on Neural Gene Expression, National Institute of Mental Health, National Institutes of Health, Bethesda, MD, United States
| | - Adi Cymerblit-Sabba
- Section on Neural Gene Expression, National Institute of Mental Health, National Institutes of Health, Bethesda, MD, United States
| | - Adam Smith
- Section on Neural Gene Expression, National Institute of Mental Health, National Institutes of Health, Bethesda, MD, United States.,Neuroscience Program, Department of Pharmacology & Toxicology, University of Kansas, Lawrence, KS, United States
| | - Matthew Vincent
- Section on Neural Gene Expression, National Institute of Mental Health, National Institutes of Health, Bethesda, MD, United States
| | - June Song
- Section on Neural Gene Expression, National Institute of Mental Health, National Institutes of Health, Bethesda, MD, United States
| | - Michael C Granovetter
- Section on Neural Gene Expression, National Institute of Mental Health, National Institutes of Health, Bethesda, MD, United States
| | - Su-Hyun Lee
- Section on Neural Gene Expression, National Institute of Mental Health, National Institutes of Health, Bethesda, MD, United States
| | - Nicholas I Cilz
- Section on Neural Gene Expression, National Institute of Mental Health, National Institutes of Health, Bethesda, MD, United States
| | - Michelle Stackmann
- Section on Neural Gene Expression, National Institute of Mental Health, National Institutes of Health, Bethesda, MD, United States
| | - Rahul Chaturvedi
- Section on Neural Gene Expression, National Institute of Mental Health, National Institutes of Health, Bethesda, MD, United States
| | - W Scott Young
- Section on Neural Gene Expression, National Institute of Mental Health, National Institutes of Health, Bethesda, MD, United States
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