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Avalos A, Traniello IM, Pérez Claudio E, Giray T. Parallel mechanisms of visual memory formation across distinct regions of the honey bee brain. J Exp Biol 2021; 224:jeb242292. [PMID: 34515309 PMCID: PMC10659034 DOI: 10.1242/jeb.242292] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2021] [Accepted: 09/02/2021] [Indexed: 01/29/2023]
Abstract
Visual learning is vital to the behavioral ecology of the Western honey bee (Apis mellifera). Honey bee workers forage for floral resources, a behavior that requires the learning and long-term memory of visual landmarks, but how these memories are mapped to the brain remains poorly understood. To address this gap in our understanding, we collected bees that successfully learned visual associations in a conditioned aversion paradigm and compared gene expression correlates of memory formation in the mushroom bodies, a higher-order sensory integration center classically thought to contribute to learning, as well as the optic lobes, the primary visual neuropil responsible for sensory transduction of visual information. We quantified expression of CREB and CaMKII, two classical genetic markers of learning, and fen-1, a gene specifically associated with punishment learning in vertebrates. As expected, we found substantial involvement of the mushroom bodies for all three markers but additionally report the involvement of the optic lobes across a similar time course. Our findings imply the molecular involvement of a sensory neuropil during visual associative learning parallel to a higher-order brain region, furthering our understanding of how a tiny brain processes environmental signals.
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Affiliation(s)
- Arián Avalos
- United States Department of Agriculture, Agricultural Research Service, Honey Bee Breeding, Genetics and Physiology Research, Baton Rouge, LA 70820, USA
| | - Ian M. Traniello
- Neuroscience Program, University of Illinois at Urbana-Champaign (UIUC), Urbana, IL 61801, USA
- Carl R. Woese Institute for Genomic Biology, UIUC, Urbana, IL 61801, USA
| | - Eddie Pérez Claudio
- Department of Biology, University of Puerto Rico (UPR), Rio Piedras Campus, San Juan, Puerto Rico00931
| | - Tugrul Giray
- Institute of Neurobiology, UPR, Medical Sciences Campus, San Juan, Puerto Rico00936
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2
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Gold AR, Glanzman DL. The central importance of nuclear mechanisms in the storage of memory. Biochem Biophys Res Commun 2021; 564:103-113. [PMID: 34020774 DOI: 10.1016/j.bbrc.2021.04.125] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2021] [Revised: 04/28/2021] [Accepted: 04/28/2021] [Indexed: 12/14/2022]
Abstract
The neurobiological nature of the memory trace (engram) remains controversial. The most widely accepted hypothesis at present is that long-term memory is stored as stable, learning-induced changes in synaptic connections. This hypothesis, the synaptic plasticity hypothesis of memory, is supported by extensive experimental data gathered from over 50 years of research. Nonetheless, there are important mnemonic phenomena that the synaptic plasticity hypothesis cannot, or cannot readily, account for. Furthermore, recent work indicates that epigenetic and genomic mechanisms play heretofore underappreciated roles in memory. Here, we critically assess the evidence that supports the synaptic plasticity hypothesis and discuss alternative non-synaptic, nuclear mechanisms of memory storage, including DNA methylation and retrotransposition. We argue that long-term encoding of memory is mediated by nuclear processes; synaptic plasticity, by contrast, represents a means of relatively temporary memory storage. In addition, we propose that memories are evaluated for their mnemonic significance during an initial period of synaptic storage; if assessed as sufficiently important, the memories then undergo nuclear encoding.
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Affiliation(s)
- Adam R Gold
- Behavioral Neuroscience Program, Department of Psychology, University of California, Los Angeles, Los Angeles, CA, 90095, USA.
| | - David L Glanzman
- Department of Integrative Biology & Physiology, UCLA College, University of California, Los Angeles, Los Angeles, CA, 90095, USA; Department of Neurobiology, David Geffen School of Medicine at UCLA, University of California, Los Angeles, Los Angeles, CA, 90095, USA; Integrative Center for Learning and Memory, Brain Research Institute, University of California, Los Angeles, Los Angeles, CA, 90095, USA.
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Identification and Characterization of the V(D)J Recombination Activating Gene 1 in Long-Term Memory of Context Fear Conditioning. Neural Plast 2015; 2016:1752176. [PMID: 26843989 PMCID: PMC4710954 DOI: 10.1155/2016/1752176] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2015] [Accepted: 10/12/2015] [Indexed: 12/17/2022] Open
Abstract
An increasing body of evidence suggests that mechanisms related to the introduction and repair of DNA double strand breaks (DSBs) may be associated with long-term memory (LTM) processes. Previous studies from our group suggested that factors known to function in DNA recombination/repair machineries, such as DNA ligases, polymerases, and DNA endonucleases, play a role in LTM. Here we report data using C57BL/6 mice showing that the V(D)J recombination-activating gene 1 (RAG1), which encodes a factor that introduces DSBs in immunoglobulin and T-cell receptor genes, is induced in the amygdala, but not in the hippocampus, after context fear conditioning. Amygdalar induction of RAG1 mRNA, measured by real-time PCR, was not observed in context-only or shock-only controls, suggesting that the context fear conditioning response is related to associative learning processes. Furthermore, double immunofluorescence studies demonstrated the neuronal localization of RAG1 protein in amygdalar sections prepared after perfusion and fixation. In functional studies, intra-amygdalar injections of RAG1 gapmer antisense oligonucleotides, given 1 h prior to conditioning, resulted in amygdalar knockdown of RAG1 mRNA and a significant impairment in LTM, tested 24 h after training. Overall, these findings suggest that the V(D)J recombination-activating gene 1, RAG1, may play a role in LTM consolidation.
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Chemotherapy-related cognitive dysfunction: current animal studies and future directions. Brain Imaging Behav 2014; 7:453-9. [PMID: 23949877 DOI: 10.1007/s11682-013-9250-3] [Citation(s) in RCA: 79] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
Cognitive impairment is a potential long-term side effect of adjuvant chemotherapy that can have a major impact on the quality of life of cancer survivors. There is a growing number of preclinical studies addressing this issue, thereby extending our knowledge of the mechanisms underlying chemotherapy-induced neurotoxicity. In this review, we will summarize the recent advances and important findings presented in these studies. Emerging challenges, such as the development of neuroprotective strategies, and the role of the blood-brain barrier on cognitive impairment will be described and future directions in this field of investigation will be outlined.
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Voluntary running in young adult mice reduces anxiety-like behavior and increases the accumulation of bioactive lipids in the cerebral cortex. PLoS One 2013; 8:e81459. [PMID: 24349072 PMCID: PMC3859495 DOI: 10.1371/journal.pone.0081459] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2012] [Accepted: 10/22/2013] [Indexed: 01/27/2023] Open
Abstract
Combinatorial therapies using voluntary exercise and diet supplementation with polyunsaturated fatty acids have synergistic effects benefiting brain function and behavior. Here, we assessed the effects of voluntary exercise on anxiety-like behavior and on total FA accumulation within three brain regions: cortex, hippocampus, and cerebellum of running versus sedentary young adult male C57/BL6J mice. The running group was subjected to one month of voluntary exercise in their home cages, while the sedentary group was kept in their home cages without access to a running wheel. Elevated plus maze (EPM), several behavioral postures and two risk assessment behaviors (RABs) were then measured in both animal groups followed immediately by blood samplings for assessment of corticosterone levels. Brains were then dissected for non-targeted lipidomic analysis of selected brain regions using gas chromatography coupled to mass spectrometry (GC/MS). Results showed that mice in the running group, when examined in the EPM, displayed significantly lower anxiety-like behavior, higher exploratory and risky behaviors, compared to sedentary mice. Notably, we found no differences in blood corticosterone levels between the two groups, suggesting that the different EPM and RAB behaviors were not related to reduced physiological stress in the running mice. Lipidomics analysis revealed a region-specific cortical decrease of the saturated FA: palmitate (C16:0) and a concomitant increase of polyunsaturated FA, arachidonic acid (AA, omega 6-C20: 4) and docosahexaenoic acid (DHA, omega 3-C22: 6), in running mice compared to sedentary controls. Finally, we found that running mice, as opposed to sedentary animals, showed significantly enhanced cortical expression of phospholipase A2 (PLA2) protein, a signaling molecule required in the production of both AA and DHA. In summary, our data support the anxiolytic effects of exercise and provide insights into the molecular processes modulated by exercise that may lead to its beneficial effects on mood.
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Efimova OI, Anokhin KV. 5-Bromo-2’-Deoxyuridine Impairs Long-Term Food Aversion Memory in Edible Snail. Bull Exp Biol Med 2012; 153:767-70. [DOI: 10.1007/s10517-012-1822-5] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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van Veen T, Goeman JJ, Monajemi R, Wardenaar KJ, Hartman CA, Snieder H, Nolte IM, Penninx BWJH, Zitman FG. Different gene sets contribute to different symptom dimensions of depression and anxiety. Am J Med Genet B Neuropsychiatr Genet 2012; 159B:519-28. [PMID: 22573416 DOI: 10.1002/ajmg.b.32058] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/12/2012] [Accepted: 04/19/2012] [Indexed: 01/09/2023]
Abstract
Although many genetic association studies have been carried out, it remains unclear which genes contribute to depression. This may be due to heterogeneity of the DSM-IV category of depression. Specific symptom-dimensions provide a more homogenous phenotype. Furthermore, as effects of individual genes are small, analysis of genetic data at the pathway-level provides more power to detect associations and yield valuable biological insight. In 1,398 individuals with a Major Depressive Disorder, the symptom dimensions of the tripartite model of anxiety and depression, General Distress, Anhedonic Depression, and Anxious Arousal, were measured with the Mood and Anxiety Symptoms Questionnaire (30-item Dutch adaptation; MASQ-D30). Association of these symptom dimensions with candidate gene sets and gene sets from two public pathway databases was tested using the Global test. One pathway was associated with General Distress, and concerned molecules expressed in the endoplasmatic reticulum lumen. Seven pathways were associated with Anhedonic Depression. Important themes were neurodevelopment, neurodegeneration, and cytoskeleton. Furthermore, three gene sets associated with Anxious Arousal regarded development, morphology, and genetic recombination. The individual pathways explained up to 1.7% of the variance. These data demonstrate mechanisms that influence the specific dimensions. Moreover, they show the value of using dimensional phenotypes on one hand and gene sets on the other hand.
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Affiliation(s)
- Tineke van Veen
- Department of Psychiatry, Leiden University Medical Centre, Leiden, The Netherlands.
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8
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Conditioned taste aversion modifies persistently the subsequent induction of neocortical long-term potentiation in vivo. Neurobiol Learn Mem 2011; 95:519-26. [DOI: 10.1016/j.nlm.2011.03.003] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2010] [Revised: 02/24/2011] [Accepted: 03/21/2011] [Indexed: 12/21/2022]
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Ginsburg S, Jablonka E. The evolution of associative learning: A factor in the Cambrian explosion. J Theor Biol 2010; 266:11-20. [DOI: 10.1016/j.jtbi.2010.06.017] [Citation(s) in RCA: 73] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2010] [Revised: 05/23/2010] [Accepted: 06/09/2010] [Indexed: 02/02/2023]
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Komissarova NV, Tiunova AA, Anokhin KV. Selective Impairments to Memory Consolidation in Chicks Produced by 5′-Iodo-2′-Deoxyuridine. ACTA ACUST UNITED AC 2009; 40:215-23. [DOI: 10.1007/s11055-009-9237-0] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2007] [Accepted: 06/09/2008] [Indexed: 10/20/2022]
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Saavedra-Rodríguez L, Vázquez A, Ortiz-Zuazaga HG, Chorna NE, González FA, Andrés L, Rodríguez K, Ramírez F, Rodríguez A, de Ortiz SP. Identification of flap structure-specific endonuclease 1 as a factor involved in long-term memory formation of aversive learning. J Neurosci 2009; 29:5726-37. [PMID: 19420241 PMCID: PMC2699464 DOI: 10.1523/jneurosci.4033-08.2009] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2008] [Revised: 03/11/2009] [Accepted: 03/24/2009] [Indexed: 01/19/2023] Open
Abstract
We previously proposed that DNA recombination/repair processes play a role in memory formation. Here, we examined the possible role of the fen-1 gene, encoding a flap structure-specific endonuclease, in memory consolidation of conditioned taste aversion (CTA). Quantitative real-time PCR showed that amygdalar fen-1 mRNA induction was associated to the central processing of the illness experience related to CTA and to CTA itself, but not to the central processing resulting from the presentation of a novel flavor. CTA also increased expression of the Fen-1 protein in the amygdala, but not the insular cortex. In addition, double immunofluorescence analyses showed that amygdalar Fen-1 expression is mostly localized within neurons. Importantly, functional studies demonstrated that amygdalar antisense knockdown of fen-1 expression impaired consolidation, but not short-term memory, of CTA. Overall, these studies define the fen-1 endonuclease as a new DNA recombination/repair factor involved in the formation of long-term memories.
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Affiliation(s)
- Lorena Saavedra-Rodríguez
- Molecular and Cellular Cognition Laboratory and
- Functional Genomics Research Center, Department of Biology, and
| | - Adrinel Vázquez
- Molecular and Cellular Cognition Laboratory and
- Functional Genomics Research Center, Department of Biology, and
| | - Humberto G. Ortiz-Zuazaga
- High Performance Computing Facility, University of Puerto Rico, Central Administration, San Juan, Puerto Rico 00931
| | - Nataliya E. Chorna
- Department of Chemistry, University of Puerto Rico, Río Piedras Campus, San Juan, Puerto Rico 00931-3360, and
| | - Fernando A. González
- Department of Chemistry, University of Puerto Rico, Río Piedras Campus, San Juan, Puerto Rico 00931-3360, and
| | | | | | | | | | - Sandra Peña de Ortiz
- Molecular and Cellular Cognition Laboratory and
- Functional Genomics Research Center, Department of Biology, and
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Xu J, Yan HC, Yang B, Tong LS, Zou YX, Tian Y. Effects of lead exposure on hippocampal metabotropic glutamate receptor subtype 3 and 7 in developmental rats. J Negat Results Biomed 2009; 8:5. [PMID: 19374778 PMCID: PMC2674876 DOI: 10.1186/1477-5751-8-5] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2008] [Accepted: 04/20/2009] [Indexed: 11/15/2022] Open
Abstract
Background A complete explanation of the mechanisms by which Pb2+ exerts toxic effects on developmental central nervous system remains unknown. Glutamate is critical to the developing brain through various subtypes of ionotropic or metabotropic glutamate receptors (mGluRs). Ionotropic N-methyl-D-aspartate receptors have been considered as a principal target in lead-induced neurotoxicity. The relationship between mGluR3/mGluR7 and synaptic plasticity had been verified by many recent studies. The present study aimed to examine the role of mGluR3/mGluR7 in lead-induced neurotoxicity. Methods Twenty-four adult and female rats were randomly selected and placed on control or 0.2% lead acetate during gestation and lactation. Blood lead and hippocampal lead levels of pups were analyzed at weaning to evaluate the actual lead content at the end of the exposure. Impairments of short -term memory and long-term memory of pups were assessed by tests using Morris water maze and by detection of hippocampal ultrastructural alterations on electron microscopy. The impact of lead exposure on mGluR3 and mGluR7 mRNA expression in hippocampal tissue of pups were investigated by quantitative real-time polymerase chain reaction and its potential role in lead neurotoxicity were discussed. Results Lead levels of blood and hippocampi in the lead-exposed rats were significantly higher than those in the controls (P < 0.001). In tests using Morris Water Maze, the overall decrease in goal latency and swimming distance was taken to indicate that controls had shorter latencies and distance than lead-exposed rats (P = 0.001 and P < 0.001 by repeated-measures analysis of variance). On transmission electron microscopy neuronal ultrastructural alterations were observed and the results of real-time polymerase chain reaction showed that exposure to 0.2% lead acetate did not substantially change gene expression of mGluR3 and mGluR7 mRNA compared with controls. Conclusion Exposure to lead before and after birth can damage short-term and long-term memory ability of young rats and hippocampal ultrastructure. However, the current study does not provide evidence that the expression of rat hippocampal mGluR3 and mGluR7 can be altered by systemic administration of lead during gestation and lactation, which are informative for the field of lead-induced developmental neurotoxicity noting that it seems not to be worthwhile to include mGluR3 and mGluR7 in future studies.
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Affiliation(s)
- Jian Xu
- Xin Hua Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai Institute for Pediatric Research, Shanghai Key Laboratory of Children's Environmental Health, Shanghai, PR China.
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Arshavsky YI. “The seven sins” of the Hebbian synapse: Can the hypothesis of synaptic plasticity explain long-term memory consolidation? Prog Neurobiol 2006; 80:99-113. [PMID: 17074430 DOI: 10.1016/j.pneurobio.2006.09.004] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2006] [Revised: 09/25/2006] [Accepted: 09/26/2006] [Indexed: 11/16/2022]
Abstract
Memorizing new facts and events means that entering information produces specific physical changes within the brain. According to the commonly accepted view, traces of memory are stored through the structural modifications of synaptic connections, which result in changes of synaptic efficiency and, therefore, in formations of new patterns of neural activity (the hypothesis of synaptic plasticity). Most of the current knowledge on learning and initial stages of memory consolidation ("synaptic consolidation") is based on this hypothesis. However, the hypothesis of synaptic plasticity faces a number of conceptual and experimental difficulties when it deals with potentially permanent consolidation of declarative memory ("system consolidation"). These difficulties are rooted in the major intrinsic self-contradiction of the hypothesis: stable declarative memory is unlikely to be based on such a non-stable foundation as synaptic plasticity. Memory that can last throughout an entire lifespan should be "etched in stone." The only "stone-like" molecules within living cells are DNA molecules. Therefore, I advocate an alternative, genomic hypothesis of memory, which suggests that acquired information is persistently stored within individual neurons through modifications of DNA, and that these modifications serve as the carriers of elementary memory traces.
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Affiliation(s)
- Yuri I Arshavsky
- Institute for Nonlinear Science, University of California San Diego, La Jolla, CA 92093-0402, USA.
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Arshavsky YI. Alzheimer's disease, brain immune privilege and memory: a hypothesis. J Neural Transm (Vienna) 2006; 113:1697-707. [PMID: 16932992 DOI: 10.1007/s00702-006-0524-4] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2006] [Accepted: 04/28/2006] [Indexed: 12/13/2022]
Abstract
The most distinctive feature of Alzheimer's disease (AD) is the specific degeneration of the neurons involved in memory consolidation, storage, and retrieval. Patients suffering from AD forget basic information about their past, loose linguistic and calculative abilities and communication skills. Thus, understanding the etiology of AD may provide insights into the mechanisms of memory and vice versa. The brain is an immunologically privileged site protected from the organism's immune reactions by the blood-brain barrier (BBB). All risk factors for AD (both cardiovascular and genetic) lead to destruction of the BBB. Evidence emerging from recent literature indicates that AD may have an autoimmune nature associated with BBB impairments. This hypothesis suggests that the process of memory consolidation involves the synthesis of novel macromolecules recognized by the immune system as "non-self" antigens. The objective of this paper is to stimulate new approaches to studies of neural mechanisms underpinning memory consolidation and its breakdown during AD. If the hypothesis on the autoimmune nature of AD is correct, the identification of the putative antigenic macromolecules might be critical to understanding the etiology and prevention of AD, as well as for elucidating cellular mechanisms of learning and memory.
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Affiliation(s)
- Y I Arshavsky
- Institute for Nonlinear Science, University of California San Diego, La Jolla, CA 92093-0402, USA.
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Colón-Cesario M, Wang J, Ramos X, García HG, Dávila JJ, Laguna J, Rosado C, Peña de Ortiz S. An inhibitor of DNA recombination blocks memory consolidation, but not reconsolidation, in context fear conditioning. J Neurosci 2006; 26:5524-33. [PMID: 16707804 PMCID: PMC6675301 DOI: 10.1523/jneurosci.3050-05.2006] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Genomic recombination requires cutting, processing, and rejoining of DNA by endonucleases, polymerases, and ligases, among other factors. We have proposed that DNA recombination mechanisms may contribute to long-term memory (LTM) formation in the brain. Our previous studies with the nucleoside analog 1-beta-D-arabinofuranosylcytosine triphosphate (ara-CTP), a known inhibitor of DNA ligases and polymerases, showed that this agent blocked consolidation of conditioned taste aversion without interfering with short-term memory (STM). However, because polymerases and ligases are also essential for DNA replication, it remained unclear whether the effects of this drug on consolidation were attributable to interference with DNA recombination or neurogenesis. Here we show, using C57BL/6 mice, that ara-CTP specifically blocks consolidation but not STM of context fear conditioning, a task previously shown not to require neurogenesis. The effects of a single systemic dose of cytosine arabinoside (ara-C) on LTM were evident as early as 6 h after training. In addition, although ara-C impaired LTM, it did not impair general locomotor activity nor induce brain neurotoxicity. Importantly, hippocampal, but not insular cortex, infusions of ara-C also blocked consolidation of context fear conditioning. Separate studies revealed that context fear conditioning training significantly induced nonhomologous DNA end joining activity indicative of DNA ligase-dependent recombination in hippocampal, but not cortex, protein extracts. Finally, unlike inhibition of protein synthesis, systemic ara-C did not block reconsolidation of context fear conditioning. Our results support the idea that DNA recombination is a process specific to consolidation that is not involved in the postreactivation editing of memories.
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Levenson JM, Roth TL, Lubin FD, Miller CA, Huang IC, Desai P, Malone LM, Sweatt JD. Evidence that DNA (cytosine-5) methyltransferase regulates synaptic plasticity in the hippocampus. J Biol Chem 2006; 281:15763-73. [PMID: 16606618 DOI: 10.1074/jbc.m511767200] [Citation(s) in RCA: 442] [Impact Index Per Article: 24.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
DNA (cytosine-5) methylation represents one of the most widely used mechanisms of enduring cellular memory. Stable patterns of DNA methylation are established during development, resulting in creation of persisting cellular phenotypes. There is growing evidence that the nervous system has co-opted a number of cellular mechanisms used during development to subserve the formation of long term memory. In this study, we examined the role DNA (cytosine-5) methyltransferase (DNMT) activity might play in regulating the induction of synaptic plasticity. We found that the DNA within promoters for reelin and brain-derived neurotrophic factor, genes implicated in the induction of synaptic plasticity in the adult hippocampus, exhibited rapid and dramatic changes in cytosine methylation when DNMT activity was inhibited. Moreover, zebularine and 5-aza-2-deoxycytidine, inhibitors of DNMT activity, blocked the induction of long term potentiation at Schaffer collateral synapses. Activation of protein kinase C in the hippocampus decreased reelin promoter methylation and increased DNMT3A gene expression. Interestingly, DNMT activity is required for protein kinase C-induced increases in histone H3 acetylation. Considered together, these results suggest that DNMT activity is dynamically regulated in the adult nervous system and that DNMT may play a role in regulating the induction of synaptic plasticity in the mature CNS.
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Affiliation(s)
- Jonathan M Levenson
- Department of Neuroscience, Baylor College of Medicine, Houston, Texas 77030, USA
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Quirk GJ, Peña de Ortiz S. Stuck in time without a nucleus: theoretical comment on Sangha et Al. (2005). Behav Neurosci 2005; 119:1155-7. [PMID: 16187846 DOI: 10.1037/0735-7044.119.4.1155] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Is forgetting caused by the passage of time or by interference from new learning? S. Sangha et al. (2005) offer strong support for the latter idea by using the sea snail Lymnaea. Memory for inhibitory avoidance was prolonged from 3 days to 7 days by preventing the snails from making unreinforced conditioned responses (extinction) following training. Similar effects were obtained with posttraining ablation of the soma of the right pedal dorsal 1, the neuron necessary for consolidation, reconsolidation, and extinction in this task. Without the soma, Lymnaea was unable to retain any new learning or forget old learning, hence remaining "stuck in time." These findings elegantly demonstrate that transcriptional regulation of gene expression is essential for memory consolidation: Local protein synthesis is not sufficient. Furthermore, memory for conditioning and extinction can coexist in the same neuron.
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Affiliation(s)
- Gregory J Quirk
- Department of Physiology, Ponce School of Medicine, Ponce, Puerto Rico.
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