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Developing zebrafish models relevant to PTSD and other trauma- and stressor-related disorders. Prog Neuropsychopharmacol Biol Psychiatry 2014; 55:67-79. [PMID: 25138994 DOI: 10.1016/j.pnpbp.2014.08.003] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/30/2014] [Revised: 08/01/2014] [Accepted: 08/07/2014] [Indexed: 11/20/2022]
Abstract
While post-traumatic stress disorder (PTSD) and other trauma- and stress-related disorders (TSRDs) represent a serious societal and public health concern, their pathogenesis is largely unknown. Given the clinical complexity of TSRD development and susceptibility, greater investigation into candidate biomarkers and specific genetic pathways implicated in both risk and resilience to trauma becomes critical. In line with this, numerous animal models have been extensively used to better understand the pathogenic mechanisms of PTSD and related TSRD. Here, we discuss the rapidly increasing potential of zebrafish as models of these disorders, and how their use may aid researchers in uncovering novel treatments and therapies in this field.
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102
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Sueki DG, Dunleavy K, Puentedura EJ, Spielholz NI, Cheng MS. The role of associative learning and fear in the development of chronic pain – a comparison of chronic pain and post-traumatic stress disorder. PHYSICAL THERAPY REVIEWS 2014. [DOI: 10.1179/1743288x14y.0000000154] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
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103
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Hager T, Jansen RF, Pieneman AW, Manivannan SN, Golani I, van der Sluis S, Smit AB, Verhage M, Stiedl O. Display of individuality in avoidance behavior and risk assessment of inbred mice. Front Behav Neurosci 2014; 8:314. [PMID: 25278853 PMCID: PMC4165351 DOI: 10.3389/fnbeh.2014.00314] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2014] [Accepted: 08/26/2014] [Indexed: 11/23/2022] Open
Abstract
Factors determining individuality are still poorly understood. Rodents are excellent model organisms to study individuality, due to a rich behavioral repertoire and the availability of well-characterized isogenic populations. However, most current behavioral assays for rodents have short test duration in novel test environments and require human interference, which introduce coercion, thereby limiting the assessment of naturally occurring individuality. Thus, we developed an automated behavior system to longitudinally monitor conditioned fear for assessing PTSD-like behavior in individual mice. The system consists of a safe home compartment connected to a risk-prone test compartment (TC). Entry and exploration of the TC is solely based on deliberate choice determined by individual fear responsiveness and fear extinction. In this novel ethological assay, C57BL/6J mice show homogeneous responses after shock exposure (innate fear), but striking variation in long-lasting fear responses based on avoidance and risk assessment (learned fear), including automated stretch-attend posture quantification. TC entry (retention) latencies after foot shock differed >24 h and the re-explored TC area differed >50% among inbred mice. Next, we compared two closely related C57BL/6 substrains. Despite substantial individual differences, previously observed higher fear of C57BL/6N vs. C57BL/6J mice was reconfirmed, whereas fear extinction was fast and did not differ. The observed variation in fear expression in isogenic mice suggests individual differences in coping style with PTSD-like avoidance. Investigating the assumed epigenetic mechanisms, with reduced interpretational ambiguity and enhanced translational value in this assay, may help improve understanding of personality type-dependent susceptibility and resilience to neuropsychiatric disorders such as PTSD.
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Affiliation(s)
- Torben Hager
- Sylics BV Amsterdam, Netherlands ; Department of Functional Genomics, Center for Neurogenomics and Cognitive Research, VU University Amsterdam Amsterdam, Netherlands ; Department of Clinical Genetics, VU University Medical Center Amsterdam, Netherlands
| | - René F Jansen
- Department of Functional Genomics, Center for Neurogenomics and Cognitive Research, VU University Amsterdam Amsterdam, Netherlands ; Department of Molecular and Cellular Neurobiology, Center for Neurogenomics and Cognitive Research, VU University Amsterdam Amsterdam, Netherlands
| | - Anton W Pieneman
- Department of Functional Genomics, Center for Neurogenomics and Cognitive Research, VU University Amsterdam Amsterdam, Netherlands ; Department of Molecular and Cellular Neurobiology, Center for Neurogenomics and Cognitive Research, VU University Amsterdam Amsterdam, Netherlands
| | | | - Ilan Golani
- Department of Zoology, Faculty of Life Sciences and Sagol School for Neuroscience, Tel Aviv University Tel Aviv, Israel
| | - Sophie van der Sluis
- Department of Functional Genomics, Center for Neurogenomics and Cognitive Research, VU University Amsterdam Amsterdam, Netherlands ; Department of Clinical Genetics, VU University Medical Center Amsterdam, Netherlands
| | - August B Smit
- Department of Molecular and Cellular Neurobiology, Center for Neurogenomics and Cognitive Research, VU University Amsterdam Amsterdam, Netherlands
| | - Matthijs Verhage
- Department of Functional Genomics, Center for Neurogenomics and Cognitive Research, VU University Amsterdam Amsterdam, Netherlands ; Department of Clinical Genetics, VU University Medical Center Amsterdam, Netherlands
| | - Oliver Stiedl
- Department of Functional Genomics, Center for Neurogenomics and Cognitive Research, VU University Amsterdam Amsterdam, Netherlands ; Department of Molecular and Cellular Neurobiology, Center for Neurogenomics and Cognitive Research, VU University Amsterdam Amsterdam, Netherlands
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104
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Kwapis JL, Wood MA. Epigenetic mechanisms in fear conditioning: implications for treating post-traumatic stress disorder. Trends Neurosci 2014; 37:706-20. [PMID: 25220045 DOI: 10.1016/j.tins.2014.08.005] [Citation(s) in RCA: 63] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2014] [Revised: 08/15/2014] [Accepted: 08/18/2014] [Indexed: 12/15/2022]
Abstract
Post-traumatic stress disorder (PTSD) and other anxiety disorders stemming from dysregulated fear memory are problematic and costly. Understanding the molecular mechanisms that contribute to the formation and maintenance of these persistent fear associations is crucial to developing treatments for PTSD. Epigenetic mechanisms, which control gene expression to produce long-lasting changes in cellular function, may support the formation of fear memory underlying PTSD. We address here the role of epigenetic mechanisms in the formation, storage, updating, and extinction of fear memories. We also discuss methods of targeting these epigenetic mechanisms to reduce the initial formation of fear memory or to enhance its extinction. Epigenetic mechanisms may provide a novel target for pharmaceutical and other treatments to reduce aversive memory contributing to PTSD.
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Affiliation(s)
- Janine L Kwapis
- Department of Neurobiology and Behavior, Center for the Neurobiology of Learning and Memory, University of California, Irvine, CA 92697, USA
| | - Marcelo A Wood
- Department of Neurobiology and Behavior, Center for the Neurobiology of Learning and Memory, University of California, Irvine, CA 92697, USA.
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105
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Pape J, Binder E. Psychotrauma als Risiko für spätere psychische Störungen. DER NERVENARZT 2014; 85:1382-9. [DOI: 10.1007/s00115-014-4085-8] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
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106
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Santiago M, Antunes C, Guedes M, Sousa N, Marques CJ. TET enzymes and DNA hydroxymethylation in neural development and function - how critical are they? Genomics 2014; 104:334-40. [PMID: 25200796 DOI: 10.1016/j.ygeno.2014.08.018] [Citation(s) in RCA: 74] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2014] [Revised: 08/25/2014] [Accepted: 08/26/2014] [Indexed: 11/30/2022]
Abstract
Epigenetic modifications of the genome play important roles in controlling gene transcription thus regulating several molecular and cellular processes. A novel epigenetic modification - 5-hydroxymethylcytosine (5hmC) - has been recently described and attracted a lot of attention due to its possible involvement in the active DNA demethylation mechanism. TET enzymes are dioxygenases capable of oxidizing the methyl group of 5-methylcytosines (5mC) and thus converting 5mC into 5hmC. Although most of the work on TET enzymes and 5hmC has been carried out in embryonic stem (ES) cells, the highest levels of 5hmC occur in the brain and in neurons, pointing to a role for this epigenetic modification in the control of neuronal differentiation, neural plasticity and brain functions. Here we review the most recent advances on the role of TET enzymes and DNA hydroxymethylation in neuronal differentiation and function.
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Affiliation(s)
- Mafalda Santiago
- Life and Health Sciences Research Institute (ICVS), School of Health Sciences, University of Minho, Braga, Portugal; ICVS/3B's - PT Government Associate Laboratory, Braga, Guimarães, Portugal
| | - Claudia Antunes
- Life and Health Sciences Research Institute (ICVS), School of Health Sciences, University of Minho, Braga, Portugal; ICVS/3B's - PT Government Associate Laboratory, Braga, Guimarães, Portugal
| | - Marta Guedes
- Life and Health Sciences Research Institute (ICVS), School of Health Sciences, University of Minho, Braga, Portugal; ICVS/3B's - PT Government Associate Laboratory, Braga, Guimarães, Portugal
| | - Nuno Sousa
- Life and Health Sciences Research Institute (ICVS), School of Health Sciences, University of Minho, Braga, Portugal; ICVS/3B's - PT Government Associate Laboratory, Braga, Guimarães, Portugal
| | - C Joana Marques
- Life and Health Sciences Research Institute (ICVS), School of Health Sciences, University of Minho, Braga, Portugal; ICVS/3B's - PT Government Associate Laboratory, Braga, Guimarães, Portugal.
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107
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Itzhak Y, Perez-Lanza D, Liddie S. The strength of aversive and appetitive associations and maladaptive behaviors. IUBMB Life 2014; 66:559-71. [PMID: 25196552 DOI: 10.1002/iub.1310] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2014] [Revised: 08/22/2014] [Accepted: 08/23/2014] [Indexed: 12/22/2022]
Abstract
Certain maladaptive behaviors are thought to be acquired through classical Pavlovian conditioning. Exaggerated fear response, which can develop through Pavlovian conditioning, is associated with acquired anxiety disorders such as post-traumatic stress disorders (PTSDs). Inflated reward-seeking behavior, which develops through Pavlovian conditioning, underlies some types of addictive behavior (e.g., addiction to drugs, food, and gambling). These maladaptive behaviors are dependent on associative learning and the development of long-term memory (LTM). In animal models, an aversive reinforcer (fear conditioning) encodes an aversive contextual and cued LTM. On the other hand, an appetitive reinforcer results in conditioned place preference (CPP) that encodes an appetitive contextual LTM. The literature on weak and strong associative learning pertaining to the development of aversive and appetitive LTM is relatively scarce; thus, this review is particularly focused on the strength of associative learning. The strength of associative learning is dependent on the valence of the reinforcer and the salience of the conditioned stimulus that ultimately sways the strength of the memory trace. Our studies suggest that labile (weak) aversive and appetitive LTM may share similar signaling pathways, whereas stable (strong) aversive and appetitive LTM is mediated through different pathways. In addition, we provide some evidence suggesting that extinction of aversive fear memory and appetitive drug memory is likely to be mediated through different signaling molecules. We put forward the importance of studies aimed to investigate the molecular mechanisms underlying the development of weak and strong memories (aversive and appetitive), which would ultimately help in the development of targeted pharmacotherapies for the management of maladaptive behaviors that arise from classical Pavlovian conditioning.
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Affiliation(s)
- Yossef Itzhak
- Department of Psychiatry and Behavioral Sciences, University of Miami Miller School of Medicine, Miami, FL, USA
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108
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Griffiths B, Hunter R. Neuroepigenetics of stress. Neuroscience 2014; 275:420-35. [DOI: 10.1016/j.neuroscience.2014.06.041] [Citation(s) in RCA: 70] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2014] [Revised: 06/05/2014] [Accepted: 06/16/2014] [Indexed: 01/12/2023]
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109
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Amygdala-dependent fear memory consolidation via miR-34a and Notch signaling. Neuron 2014; 83:906-18. [PMID: 25123309 DOI: 10.1016/j.neuron.2014.07.019] [Citation(s) in RCA: 92] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/10/2014] [Indexed: 11/23/2022]
Abstract
UNLABELLED Using an array-based approach after auditory fear conditioning and microRNA (miRNA) sponge-mediated inhibition, we identified a role for miR-34a within the basolateral amygdala (BLA) in fear memory consolidation. Luciferase assays and bioinformatics suggested the Notch pathway as a target of miR-34a. mRNA and protein levels of Notch receptors and ligands are downregulated in a time- and learning-specific manner after fear conditioning in the amygdala. Systemic and stereotaxic manipulations of the Notch pathway indicated that Notch signaling in the BLA suppresses fear memory consolidation. Impairment of fear memory consolidation after inhibition of miR-34a within the BLA is rescued by inhibiting Notch signaling. Together, these data suggest that within the BLA, a transient decrease in Notch signaling, via miR-34a regulation, is important for the consolidation of fear memory. This work expands the idea that developmental molecules have roles in adult behavior and that existing interventions targeting them hold promise for treating neuropsychiatric disorders. VIDEO ABSTRACT
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110
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Lukowiak K, Heckler B, Bennett TE, Schriner EK, Wyrick K, Jewett C, Todd RP, Sorg BA. Enhanced memory persistence is blocked by a DNA methyltransferase inhibitor in the snail Lymnaea stagnalis. ACTA ACUST UNITED AC 2014; 217:2920-9. [PMID: 24902747 DOI: 10.1242/jeb.106765] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Lymnaea stagnalis provides an excellent model system for studying memory because these snails have a well-described set of neurons, a single one of which controls expression of long-term memory of operantly conditioned respiratory behavior. We have shown that several different manipulations, including pre-training exposure to serotonin (5-HT) or methamphetamine, submersion of snails after training to prevent memory interference, and exposure to effluent from predatory crayfish (CE), enhance memory persistence. Changes in DNA methylation underlie formation of strong memories in mammals and 5-HT-enhanced long-term facilitation in Aplysia. Here we determined the impact of the DNA methyltransferase inhibitor, 5-aza-2'-deoxycytidine (5-AZA; 87 μmol l(-1)), on enhanced memory persistence by all four manipulations. We found that 5-HT (100 μmol l(-1)) enhanced memory persistence, which was blocked by 5-AZA pretreatment. Snails pre-exposed to 3.3 μmol l(-1) Meth 4 h prior to training demonstrated memory 72 h later, which was not present in controls. This memory-enhancing effect was blocked by pre-treatment with 87 μmol l(-1) 5-AZA. Similarly, submersion to prevent interference learning as well as training in CE produced memory that was not present in controls, and these effects were blocked by pre-treatment with 87 μmol l(-1) 5-AZA. In contrast, 5-AZA injection did not alter expression of normal (non-enhanced) memory, suggesting that these four stimuli enhance memory persistence by increasing DNA methyltransferase activity, which, in turn, increases expression of memory-enhancing genes and/or inhibits memory suppressor genes. These studies lay important groundwork for delineating gene methylation changes that are common to persistent memory produced by different stimuli.
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Affiliation(s)
- Ken Lukowiak
- Cumming School of Medicine, University of Calgary, Calgary, AL T2N 4N1, Canada
| | - Benjamin Heckler
- Alcohol and Drug Abuse Research Program and Translational Addiction Research Center, Department of Integrative Physiology and Neuroscience, Washington State University, Vancouver, WA 98686, USA
| | - Thomas E Bennett
- Alcohol and Drug Abuse Research Program and Translational Addiction Research Center, Department of Integrative Physiology and Neuroscience, Washington State University, Vancouver, WA 98686, USA
| | - Ellen K Schriner
- Alcohol and Drug Abuse Research Program and Translational Addiction Research Center, Department of Integrative Physiology and Neuroscience, Washington State University, Vancouver, WA 98686, USA
| | - Kathryn Wyrick
- Alcohol and Drug Abuse Research Program and Translational Addiction Research Center, Department of Integrative Physiology and Neuroscience, Washington State University, Vancouver, WA 98686, USA
| | - Cynthia Jewett
- Alcohol and Drug Abuse Research Program and Translational Addiction Research Center, Department of Integrative Physiology and Neuroscience, Washington State University, Vancouver, WA 98686, USA
| | - Ryan P Todd
- Alcohol and Drug Abuse Research Program and Translational Addiction Research Center, Department of Integrative Physiology and Neuroscience, Washington State University, Vancouver, WA 98686, USA
| | - Barbara A Sorg
- Alcohol and Drug Abuse Research Program and Translational Addiction Research Center, Department of Integrative Physiology and Neuroscience, Washington State University, Vancouver, WA 98686, USA
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111
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Active, phosphorylated fingolimod inhibits histone deacetylases and facilitates fear extinction memory. Nat Neurosci 2014; 17:971-80. [PMID: 24859201 DOI: 10.1038/nn.3728] [Citation(s) in RCA: 161] [Impact Index Per Article: 16.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2014] [Accepted: 04/25/2014] [Indexed: 02/08/2023]
Abstract
FTY720 (fingolimod), an FDA-approved drug for treatment of multiple sclerosis, has beneficial effects in the CNS that are not yet well understood, independent of its effects on immune cell trafficking. We show that FTY720 enters the nucleus, where it is phosphorylated by sphingosine kinase 2 (SphK2), and that nuclear FTY720-P binds and inhibits class I histone deacetylases (HDACs), enhancing specific histone acetylations. FTY720 is also phosphorylated in mice and accumulates in the brain, including the hippocampus, inhibits HDACs and enhances histone acetylation and gene expression programs associated with memory and learning, and rescues memory deficits independently of its immunosuppressive actions. Sphk2(-/-) mice have lower levels of hippocampal sphingosine-1-phosphate, an endogenous HDAC inhibitor, and reduced histone acetylation, and display deficits in spatial memory and impaired contextual fear extinction. Thus, sphingosine-1-phosphate and SphK2 play specific roles in memory functions and FTY720 may be a useful adjuvant therapy to facilitate extinction of aversive memories.
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112
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Sparta DR, Smithuis J, Stamatakis AM, Jennings JH, Kantak PA, Ung RL, Stuber GD. Inhibition of projections from the basolateral amygdala to the entorhinal cortex disrupts the acquisition of contextual fear. Front Behav Neurosci 2014; 8:129. [PMID: 24834031 PMCID: PMC4018552 DOI: 10.3389/fnbeh.2014.00129] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2014] [Accepted: 03/28/2014] [Indexed: 01/16/2023] Open
Abstract
The development of excessive fear and/or stress responses to environmental cues such as contexts associated with a traumatic event is a hallmark of post-traumatic stress disorder (PTSD). The basolateral amygdala (BLA) has been implicated as a key structure mediating contextual fear conditioning. In addition, the hippocampus has an integral role in the encoding and processing of contexts associated with strong, salient stimuli such as fear. Given that both the BLA and hippocampus play an important role in the regulation of contextual fear conditioning, examining the functional connectivity between these two structures may elucidate a role for this pathway in the development of PTSD. Here, we used optogenetic strategies to demonstrate that the BLA sends a strong glutamatergic projection to the hippocampal formation through the entorhinal cortex (EC). Next, we photoinhibited glutamatergic fibers from the BLA terminating in the EC during the acquisition or expression of contextual fear conditioning. In mice that received optical inhibition of the BLA-to-EC pathway during the acquisition session, we observed a significant decrease in freezing behavior in a context re-exposure session. In contrast, we observed no differences in freezing behavior in mice that were only photoinhibited during the context re-exposure session. These data demonstrate an important role for the BLA-to-EC glutamatergic pathway in the acquisition of contextual fear conditioning.
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Affiliation(s)
- Dennis R Sparta
- Departments of Psychiatry and Cell Biology and Physiology, UNC Neuroscience Center, University of North Carolina at Chapel Hill Chapel Hill, NC, USA ; Bowles Center for Alcohol Studies, University of North Carolina at Chapel Hill Chapel Hill, NC, USA
| | - Jim Smithuis
- Departments of Psychiatry and Cell Biology and Physiology, UNC Neuroscience Center, University of North Carolina at Chapel Hill Chapel Hill, NC, USA
| | - Alice M Stamatakis
- Departments of Psychiatry and Cell Biology and Physiology, UNC Neuroscience Center, University of North Carolina at Chapel Hill Chapel Hill, NC, USA ; Curriculum in Neurobiology, University of North Carolina at Chapel Hill Chapel Hill, NC, USA
| | - Joshua H Jennings
- Departments of Psychiatry and Cell Biology and Physiology, UNC Neuroscience Center, University of North Carolina at Chapel Hill Chapel Hill, NC, USA ; Curriculum in Neurobiology, University of North Carolina at Chapel Hill Chapel Hill, NC, USA
| | - Pranish A Kantak
- Departments of Psychiatry and Cell Biology and Physiology, UNC Neuroscience Center, University of North Carolina at Chapel Hill Chapel Hill, NC, USA
| | - Randall L Ung
- Departments of Psychiatry and Cell Biology and Physiology, UNC Neuroscience Center, University of North Carolina at Chapel Hill Chapel Hill, NC, USA ; Curriculum in Neurobiology, University of North Carolina at Chapel Hill Chapel Hill, NC, USA
| | - Garret D Stuber
- Departments of Psychiatry and Cell Biology and Physiology, UNC Neuroscience Center, University of North Carolina at Chapel Hill Chapel Hill, NC, USA ; Bowles Center for Alcohol Studies, University of North Carolina at Chapel Hill Chapel Hill, NC, USA ; Curriculum in Neurobiology, University of North Carolina at Chapel Hill Chapel Hill, NC, USA
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113
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The role of DNA methylation in stress-related psychiatric disorders. Neuropharmacology 2014; 80:115-32. [DOI: 10.1016/j.neuropharm.2014.01.013] [Citation(s) in RCA: 219] [Impact Index Per Article: 21.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2013] [Revised: 12/19/2013] [Accepted: 01/09/2014] [Indexed: 02/06/2023]
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114
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Affiliation buffers stress: cumulative genetic risk in oxytocin-vasopressin genes combines with early caregiving to predict PTSD in war-exposed young children. Transl Psychiatry 2014; 4:e370. [PMID: 24618689 PMCID: PMC3966045 DOI: 10.1038/tp.2014.6] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/10/2013] [Revised: 12/19/2013] [Accepted: 01/06/2014] [Indexed: 12/19/2022] Open
Abstract
Research indicates that risk for post-traumatic stress disorder (PTSD) is shaped by the interaction between genetic vulnerability and early caregiving experiences; yet, caregiving has typically been assessed by adult retrospective accounts. Here, we employed a prospective longitudinal design with real-time observations of early caregiving combined with assessment of genetic liability along the axis of vasopressin-oxytocin (OT) gene pathways to test G × E contributions to PTSD. Participants were 232 young Israeli children (1.5-5 years) and their parents, including 148 living in zones of continuous war and 84 controls. A cumulative genetic risk factor was computed for each family member by summing five risk alleles across three genes (OXTR, CD38 and AVPR1a) previously associated with psychopathology, sociality and caregiving. Child PTSD was diagnosed and mother-child interactions were observed in multiple contexts. In middle childhood (7-8 years), child psychopathology was re-evaluated. War exposure increased propensity to develop Axis-I disorder by threefold: 60% of exposed children displayed a psychiatric disorder by middle childhood and 62% of those showed several comorbid disorders. On the other hand, maternal sensitive support reduced risk for psychopathology. G × E effect was found for child genetic risk: in the context of war exposure, greater genetic risk on the vasopressin-OT pathway increased propensity for psychopathology. Among exposed children, chronicity of PTSD from early to middle childhood was related to higher child, maternal and paternal genetic risk, low maternal support and greater initial avoidance symptoms. Child avoidance was predicted by low maternal support and reduced mother-child reciprocity. These findings underscore the saliency of both genetic and behavioral facets of the human affiliation system in shaping vulnerability to PTSD as well as providing an underlying mechanism of post-traumatic resilience.
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115
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Abstract
Post-traumatic stress disorder (PTSD) is increasingly recognized as both a disorder of enormous mental health and societal burden, but also as an anxiety disorder that may be particularly understandable from a scientific perspective. Specifically, PTSD can be conceptualized as a disorder of fear and stress dysregulation, and the neural circuitry underlying these pathways in both animals and humans are becoming increasingly well understood. Furthermore, PTSD is the only disorder in psychiatry in which the initiating factor, the trauma exposure, can be identified. Thus, the pathophysiology of the fear and stress response underlying PTSD can be examined and potentially interrupted. Twin studies have shown that the development of PTSD following a trauma is heritable, and that genetic risk factors may account for up to 30-40% of this heritability. A current goal is to understand the gene pathways that are associated with PTSD, and how those genes act on the fear/stress circuitry to mediate risk vs. resilience for PTSD. This review will examine gene pathways that have recently been analysed, primarily through candidate gene studies (including neuroimaging studies of candidate genes), in addition to genome-wide associations and the epigenetic regulation of PTSD. Future and on-going studies are utilizing larger and collaborative cohorts to identify novel gene candidates through genome-wide association and other powerful genomic approaches. Identification of PTSD biological pathways strengthens the hope of progress in the mechanistic understanding of a model psychiatric disorder and allows for the development of targeted treatments and interventions.
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116
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Rampp C, Binder EB, Provençal N. Epigenetics in posttraumatic stress disorder. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2014; 128:29-50. [PMID: 25410540 DOI: 10.1016/b978-0-12-800977-2.00002-4] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Reported exposure to traumatic event is relatively common within the general population (40-90%), but only a fraction of individuals will develop posttraumatic stress disorder (PTSD). Indeed, the lifetime prevalence of PTSD is estimated to range between 7% and 12%. The factors influencing risk or resilience to PTSD after exposure to traumatic events are likely both environmental, such as type, timing, and extent of trauma, and genetic. Recently, epigenetic mechanisms have been implicated in mediating altered risk for PTSD as they can reflect both genetic and environmental influences. In this chapter, we describe the accumulating evidences for epigenetic factors in PTSD highlighting the importance of sensitive periods as well as methodological aspects such as tissue availabilities for such studies. We describe studies using a candidate gene approach focusing mainly on key players in the stress hormone regulation that show epigenetic alterations both in humans and in animal models for PTSD. We also summarize the results of epigenome-wide studies reporting associations with PTSD. For the above, we focus on one epigenetic mechanism, DNA methylation, as it is so far the best studied for this disorder. Finally, we describe how epigenetic mechanisms could be responsible for the long-lasting effects of gene-environment interactions observed in PTSD.
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Affiliation(s)
- Carina Rampp
- Department of Translational Research in Psychiatry, Max Planck Institute of Psychiatry, Munich, Germany
| | - Elisabeth B Binder
- Department of Translational Research in Psychiatry, Max Planck Institute of Psychiatry, Munich, Germany; Department of Psychiatry and Behavioral Sciences, Emory University School of Medicine, Atlanta, Georgia, USA
| | - Nadine Provençal
- Department of Translational Research in Psychiatry, Max Planck Institute of Psychiatry, Munich, Germany
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117
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Agis-Balboa RC, Fischer A. Generating new neurons to circumvent your fears: the role of IGF signaling. Cell Mol Life Sci 2014; 71:21-42. [PMID: 23543251 PMCID: PMC11113432 DOI: 10.1007/s00018-013-1316-2] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2012] [Revised: 02/12/2013] [Accepted: 03/04/2013] [Indexed: 12/13/2022]
Abstract
Extinction of fear memory is a particular form of cognitive function that is of special interest because of its involvement in the treatment of anxiety and mood disorders. Based on recent literature and our previous findings (EMBO J 30(19):4071-4083, 2011), we propose a new hypothesis that implies a tight relationship among IGF signaling, adult hippocampal neurogenesis and fear extinction. Our proposed model suggests that fear extinction-induced IGF2/IGFBP7 signaling promotes the survival of neurons at 2-4 weeks old that would participate in the discrimination between the original fear memory trace and the new safety memory generated during fear extinction. This is also called "pattern separation", or the ability to distinguish similar but different cues (e.g., context). To understand the molecular mechanisms underlying fear extinction is therefore of great clinical importance.
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Affiliation(s)
- R C Agis-Balboa
- Department of Psychiatry and Psychotherapy, University Medical Center Göttingen, Grisebach Str. 5, 37077, Göttingen, Germany,
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118
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McCarthy MM, Nugent BM. Epigenetic contributions to hormonally-mediated sexual differentiation of the brain. J Neuroendocrinol 2013; 25:1133-40. [PMID: 23919286 PMCID: PMC5330673 DOI: 10.1111/jne.12072] [Citation(s) in RCA: 81] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/18/2013] [Revised: 06/18/2013] [Accepted: 06/29/2013] [Indexed: 12/28/2022]
Abstract
It has been long established that hormones exert enduring influences on the developing brain that direct the reproductive response in adulthood, although the cellular mechanisms by which organisational effects are maintained have not been determined satisfactorily. Recent interest in epigenetic modifications to the nervous system has highlighted the potential for hormone-induced changes to the genome that could endure for the lifespan but not be transmitted to the next generation. Preliminary evidence suggests that this is indeed possible because sex differences in the histone code and in the methylation of CpGs in the promoters of specific genes have been identified and, at times, functionally correlated with behaviour. The present review provides an overview of epigenetic processes and discusses the current state-of-the-art, and also identifies future directions.
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Affiliation(s)
- M M McCarthy
- Department of Pharmacology, School of Medicine, University of Maryland, Baltimore, MD, USA
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119
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Hunter RG, McEwen BS. Stress and anxiety across the lifespan: structural plasticity and epigenetic regulation. Epigenomics 2013; 5:177-94. [PMID: 23566095 DOI: 10.2217/epi.13.8] [Citation(s) in RCA: 105] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
The brain is the central organ of the body's response to and perception of stress. Both the juvenile and the adult brain show a significant capacity for lasting physiological, structural and behavioral plasticity as a consequence of stress exposure. The hypothesis that epigenetic mechanisms might lie behind the lasting effects of stress upon the brain has proven a fruitful one. In this review, we examine the growing literature showing that stress has a direct impact on epigenetic marks at all life history stages thus far examined and how, in turn, epigenetic mechanisms play a role in altering stress responsiveness, anxiety and brain plasticity across the lifespan and beyond to succeeding generations. In addition, we will examine our own recent findings that stress interacts with the epigenome to regulate the expression of transposable elements in a regionally specific fashion, a finding with significant implications for a portion of the genome which is tenfold larger than that occupied by the genes themselves.
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Affiliation(s)
- Richard G Hunter
- Harold & Margaret Milliken Hatch Laboratory of Neuroendocrinology, The Rockefeller University, 1230 York Ave., New York, NY 10065, USA.
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120
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Mac Callum PE, Hebert M, Adamec RE, Blundell J. Systemic inhibition of mTOR kinase via rapamycin disrupts consolidation and reconsolidation of auditory fear memory. Neurobiol Learn Mem 2013; 112:176-85. [PMID: 24012802 DOI: 10.1016/j.nlm.2013.08.014] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2013] [Revised: 08/27/2013] [Accepted: 08/28/2013] [Indexed: 11/30/2022]
Abstract
The mammalian target of rapamycin (mTOR) kinase is a critical regulator of mRNA translation and is known to be involved in various long lasting forms of synaptic and behavioural plasticity. However, information concerning the temporal pattern of mTOR activation and susceptibility to pharmacological intervention during both consolidation and reconsolidation of long-term memory (LTM) remains scant. Male C57BL/6 mice were injected systemically with rapamycin at various time points following conditioning or retrieval in an auditory fear conditioning paradigm, and compared to vehicle (and/or anisomycin) controls for subsequent memory recall. Systemic blockade of mTOR with rapamycin immediately or 12h after training or reactivation impairs both consolidation and reconsolidation of an auditory fear memory. Further behavioural analysis revealed that the enduring effects of rapamycin on reconsolidation are dependent upon reactivation of the memory trace. Rapamycin, however, has no effect on short-term memory or the ability to retrieve an established fear memory. Collectively, our data suggest that biphasic mTOR signalling is essential for both consolidation and reconsolidation-like activities that contribute to the formation, re-stabilization, and persistence of long term auditory-fear memories, while not influencing other aspects of the memory trace. These findings also provide evidence for a cogent treatment model for reducing the emotional strength of established, traumatic memories analogous to those observed in acquired anxiety disorders such as posttraumatic stress disorder (PTSD) and specific phobias, through pharmacologic blockade of mTOR using systemic rapamycin following reactivation.
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Affiliation(s)
- Phillip E Mac Callum
- Department of Psychology, Memorial University of Newfoundland, 232 Elizabeth Ave., St. John's, Newfoundland A1B 3X9, Canada
| | - Mark Hebert
- Department of Psychology, Memorial University of Newfoundland, 232 Elizabeth Ave., St. John's, Newfoundland A1B 3X9, Canada
| | - Robert E Adamec
- Department of Psychology, Memorial University of Newfoundland, 232 Elizabeth Ave., St. John's, Newfoundland A1B 3X9, Canada
| | - Jacqueline Blundell
- Department of Psychology, Memorial University of Newfoundland, 232 Elizabeth Ave., St. John's, Newfoundland A1B 3X9, Canada.
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121
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Emerging roles for chromatin as a signal integration and storage platform. Nat Rev Mol Cell Biol 2013; 14:211-24. [PMID: 23524488 DOI: 10.1038/nrm3545] [Citation(s) in RCA: 210] [Impact Index Per Article: 19.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Cells of a multicellular organism, all containing nearly identical genetic information, respond to differentiation cues in variable ways. In addition, cells are plastic, able to execute their specialized function while maintaining the ability to adapt to environmental changes. This is achieved through multiple mechanisms, including the direct regulation of chromatin-based processes in response to stimuli. How signal transduction pathways directly communicate with chromatin to change the epigenetic landscape is poorly understood. The preponderance of covalent modifications on histone tails coupled with a relatively small number of functional outputs raises the possibility that chromatin acts as a site of signal integration and storage.
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Zoladz PR, Diamond DM. Current status on behavioral and biological markers of PTSD: a search for clarity in a conflicting literature. Neurosci Biobehav Rev 2013; 37:860-95. [PMID: 23567521 DOI: 10.1016/j.neubiorev.2013.03.024] [Citation(s) in RCA: 188] [Impact Index Per Article: 17.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2012] [Revised: 03/23/2013] [Accepted: 03/27/2013] [Indexed: 12/24/2022]
Abstract
Extensive research has identified stereotypic behavioral and biological abnormalities in post-traumatic stress disorder (PTSD), such as heightened autonomic activity, an exaggerated startle response, reduced basal cortisol levels and cognitive impairments. We have reviewed primary research in this area, noting that factors involved in the susceptibility and expression of PTSD symptoms are more complex and heterogeneous than is commonly stated, with extensive findings which are inconsistent with the stereotypic behavioral and biological profile of the PTSD patient. A thorough assessment of the literature indicates that interactions among myriad susceptibility factors, including social support, early life stress, sex, age, peri- and post-traumatic dissociation, cognitive appraisal of trauma, neuroendocrine abnormalities and gene polymorphisms, in conjunction with the inconsistent expression of the disorder across studies, confounds attempts to characterize PTSD as a monolithic disorder. Overall, our assessment of the literature addresses the great challenge in developing a behavioral and biomarker-based diagnosis of PTSD.
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Affiliation(s)
- Phillip R Zoladz
- Department of Psychology, Sociology, & Criminal Justice, Ohio Northern University, 525 S. Main St., Ada, OH, 45810, USA
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Anderson-Schmidt H, Beltcheva O, Brandon MD, Byrne EM, Diehl EJ, Duncan L, Gonzalez SD, Hannon E, Kantojärvi K, Karagiannidis I, Kos MZ, Kotyuk E, Laufer BI, Mantha K, McGregor NW, Meier S, Nieratschker V, Spiers H, Squassina A, Thakur GA, Tiwari Y, Viswanath B, Way MJ, Wong CCP, O'Shea A, DeLisi LE. Selected rapporteur summaries from the XX World Congress of Psychiatric Genetics, Hamburg, Germany, October 14-18, 2012. Am J Med Genet B Neuropsychiatr Genet 2013; 162B:96-121. [PMID: 23341144 PMCID: PMC4090768 DOI: 10.1002/ajmg.b.32132] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/19/2012] [Accepted: 12/28/2012] [Indexed: 12/19/2022]
Abstract
The XXth World Congress of Psychiatric Genetics (WCPG), sponsored by The International Society of Psychiatric Genetics (ISPG) took place in Hamburg, Germany on October 14-18, 2012. Approximately 600 participants gathered to discuss the latest findings in this rapidly advancing field. The following report was written by student travel awardees. Each was assigned sessions as rapporteurs. This manuscript represents topics covered in most, but not all, oral presentations during the conference, and some of the major notable new findings reported at this 2012 WCPG.
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Affiliation(s)
- Heike Anderson-Schmidt
- Dept. of Psychiatry and Psychotherapy, Section of Psychiatric Genetics, Von-Siebold-Str. 5, University Medical Centre Göttingen, Goettingen, Germany, Phone: 0049 551 3920485
| | - Olga Beltcheva
- Molecular Medicine Center, Medical University – Sofia, 2 Zdrave str., SBALAG “Maichin dom”, et. 14, Phone: +359 2 9172 268
| | - Mariko D Brandon
- Meharry Medical College, Nashville, TN, 421 Van Buren Street, Nashville, TN 37208, Phone: 205-529-2138
| | - Enda M Byrne
- The University of Queensland, Queensland Brain Institute, St. Lucia, QLD 4072, Australia, Queensland Brain Institute, Upland Road, St. Lucia, QLD 4072, Australia, Phone: +61 7 3346 6300
| | - Eric J Diehl
- University of Western Ontario, 1151 Richmond St., London Ontario Canada, N6A 5B7
| | - Laramie Duncan
- Harvard School of Public Health, 185 Cambridge St., Boston, MA 02114, phone: (303) 819-8952, fax: 617- 726-0830
| | - Suzanne D Gonzalez
- Texas Tech University Health Sciences Center, Center of Excellence in Neurosciences, 454 Soledad St. Suite 200, San Antonio, TX, 78205, Phone: 210-270-1980, Fax: 210-270-1985
| | - Eilis Hannon
- Institute of Psychologoical Medicine and Clinical Neurosciences, Cardiff University School of Medicine, Henry Wellcome Building, Heath Park, Cardiff, CF14 4XN, +44 02920 687863
| | - Katri Kantojärvi
- Department of Medical Genetics, University of Helsinki, P.O. Box 63, 00014 University of Helsinki, Finland, Phone: +358 50 3598450, Fax: +358 9 191 25105
| | - Iordanis Karagiannidis
- Department of Molecular Biology and Genetics, Democritus University of Thrace, Panepistimioupoli, Dragana Alexandroupoli 68100, Greece, Phone: +306943023084
| | - Mark Z Kos
- Texas Biomedical Research Institute, 7620 N.W. Loop 410, San Antonio, TX 78227, Phone: (210) 258-9880, Fax: (210) 258-9444
| | - Eszter Kotyuk
- Institute of Psychology, Eötvös Loránd University, Budapest, Hungary, 1064 Budapest, Izabella utca 46. Phone: +36306572144
| | - Benjamin I Laufer
- University of Western Ontario, 1151 Richmond Street London Ontario Canada N6A 5B7, phone: 519 661 2111 x86928
| | - Katarzyna Mantha
- University of Western Ontario, 1151 Richmond Street, London, Ontario, Canada, N6A 5B7, Phone: 519-661-2111 x86928
| | - Nathaniel W McGregor
- Department of Psychiatry, Division of Biomedical Sciences, Faculty of Medicine and Health Sciences University of Stellenbosch, Tygerberg Medical Campus, Tygerberg, South Africa, 7505, Phone: (+27)21 938 9692 (lab), Fax: (+27)21 938 9863
| | - Sandra Meier
- Department of Genetic Epidemiology in Psychiatry, Central Institute of Mental Health Mannheim, University Medical Center Mannheim, University of Heidelberg, Germany, J5, 68159 Mannheim, Germany, Phone: 49 621 1703 6071, Fax: 49 621 1703 6065
| | - Vanessa Nieratschker
- Department of Genetic Epidemiology in Psychiatry, Central Institute of Mental Health, Medical Faculty Mannheim / Heidelberg University, J 5, 68159 Mannheim, Germany; Phone: 004962117036091, Fax: 004962117036055
| | - Helen Spiers
- King's College London, MRC SGDP Centre PO82, Institute of Psychiatry, De Crespigny Park Denmark Hill, London SE5 8AF, Phone: 020 7848 0873, Fax: 020 7848 0866
| | - Alessio Squassina
- Section of Neuroscience and Clinical Pharmacology, Department of Biomedical Sciences, University of Cagliari, Sp 8, Sestu-Monserrato, Km 0.700, 09042 Cagliari, Italy, Phone +39 070 675 4334, Fax +39 070 675 4320
| | - Geeta A Thakur
- Integrated Program in Neuroscience, McGill University, Douglas Mental Health University Institute, 6875 LaSalle Blvd., Montreal, Quebec, Canada, H4H 1R3, Phone: 1-514-761-6131 ext. 3429, Fax: 1-514-888-4064
| | - Yash Tiwari
- Neuroscience Research Australia (NeuRA), Sydney, Australia, Phone: (+61) 02 93991112, Fax: (+61) 02 9399 1005
| | - Biju Viswanath
- Department of Psychiatry, National Institute of Mental Health and Neuro Sciences, Hosur Road, Bangalore – 560029, Phone: +91 80 26995261, Fax: +91 80 26564822
| | - Michael J Way
- University College London, Molecular Psychiatry Laboratory, UCL Mental Health Sciences Unit, Rockefeller Building, Gower Street, London, WC1E 6BT
| | - Cybele CP Wong
- MRC Social, Genetic & Developmental Psychiatry Centre, Institute of Psychiatry, PO80, King's College London, London SE5 8AF, United Kingdom, Phone: (44) 20 7848 0521
| | - Anne O'Shea
- Coordinator and editor of reports. Address all correspondence to Lynn E DeLisi, MD, Harvard Medical School, Brockton VA Boston Healthcare System, 940 Belmont Street, Brockton, MA 02301, Phone: 774-826-3155, Fax: 774-826-1758, DeLisi76aol.com
| | - Lynn E DeLisi
- Coordinator and editor of reports. Address all correspondence to Lynn E DeLisi, MD, Harvard Medical School, Brockton VA Boston Healthcare System, 940 Belmont Street, Brockton, MA 02301, Phone: 774-826-3155, Fax: 774-826-1758, DeLisi76aol.com
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The histone deacetylase inhibitor sodium butyrate modulates acquisition and extinction of cocaine-induced conditioned place preference. Pharmacol Biochem Behav 2013; 106:109-16. [PMID: 23454534 DOI: 10.1016/j.pbb.2013.02.009] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/31/2012] [Revised: 02/14/2013] [Accepted: 02/18/2013] [Indexed: 01/08/2023]
Abstract
Despite decades of research on treatments for cocaine dependence, relapse rates following many behavioral and drug-based therapies remain high. This may be in part because cocaine-associated cues and contexts can invoke powerful drug cravings years after quitting. Recent studies suggest that drugs that promote cognitive function can enhance the formation of memories involving cocaine and other substances. One target of these drugs is facilitating histone acetylation to promote learning by increasing gene transcription that supports memory formation. Here, we investigate the effects of the histone deacetylase (HDAC) inhibitor sodium butyrate (NaBut) on cocaine-induced conditioned place preference (CPP) in C57BL/6 mice. After establishing a graded dose-response curve (2, 5, & 20 mg/kg) for cocaine-induced CPP, we examined the effects of different doses of NaBut (0, 0.3, 0.6, & 1.2 g/kg) on conditioning, extinction, and post-extinction reconditioning of CPP. A high dose of NaBut (1.2 g/kg) enhanced initial acquisition of cocaine CPP, but there were no effects of NaBut on reconditioning of extinguished CPP. Effects of NaBut on extinction were more complex, with a low-dose (0.3 g/kg) facilitating extinction and a high dose (1.2 g/kg) weakening extinction evident by preference at a retention test. These findings suggest that HDAC inhibition may have dose dependent effects on different components of cocaine CPP, with implications for (1) involvement of histone acetylation in context-drug learning, (2) interpretation of acute and chronic drug effects, and (3) the targeting of different types of learning in therapeutic application of HDAC inhibitors.
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125
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Lattal KM, Wood MA. Epigenetics and persistent memory: implications for reconsolidation and silent extinction beyond the zero. Nat Neurosci 2013; 16:124-9. [PMID: 23354385 PMCID: PMC3740093 DOI: 10.1038/nn.3302] [Citation(s) in RCA: 76] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2012] [Accepted: 12/10/2012] [Indexed: 12/13/2022]
Abstract
Targeting epigenetic mechanisms during initial learning or memory retrieval can lead to persistent memory. Retrieval induces plasticity that may result in reconsolidation of the original memory, in which critical molecular events are needed to stabilize the memory, or extinction, in which new learning during the retrieval trial creates an additional memory that reflects the changed environmental contingencies. A canonical feature of extinction is that the original response is temporarily suppressed, but returns under various conditions. These characteristics have defined whether a given manipulation alters extinction (when persistence does not occur) or reconsolidation (when persistence does occur). A problem arises with these behavioral definitions when considering the potential for persistent memory of extinction. Recent studies have found that epigenetic modulation of memory processes leads to surprisingly robust and persistent extinction. We discuss evidence from behavioral epigenetic approaches that forces a re-evaluation of widely used behavioral definitions of extinction and reconsolidation.
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Zovkic IB, Guzman-Karlsson MC, Sweatt JD. Epigenetic regulation of memory formation and maintenance. Learn Mem 2013; 20:61-74. [PMID: 23322554 DOI: 10.1101/lm.026575.112] [Citation(s) in RCA: 229] [Impact Index Per Article: 20.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Understanding the cellular and molecular mechanisms underlying the formation and maintenance of memories is a central goal of the neuroscience community. It is well regarded that an organism's ability to lastingly adapt its behavior in response to a transient environmental stimulus relies on the central nervous system's capability for structural and functional plasticity. This plasticity is dependent on a well-regulated program of neurotransmitter release, post-synaptic receptor activation, intracellular signaling cascades, gene transcription, and subsequent protein synthesis. In the last decade, epigenetic markers like DNA methylation and post-translational modifications of histone tails have emerged as important regulators of the memory process. Their ability to regulate gene transcription dynamically in response to neuronal activation supports the consolidation of long-term memory. Furthermore, the persistent and self-propagating nature of these mechanisms, particularly DNA methylation, suggests a molecular mechanism for memory maintenance. In this review, we will examine the evidence that supports a role of epigenetic mechanisms in learning and memory. In doing so, we hope to emphasize (1) the widespread involvement of these mechanisms across different behavioral paradigms and distinct brain regions, (2) the temporal and genetic specificity of these mechanisms in response to upstream signaling cascades, and (3) the functional outcome these mechanisms may have on structural and functional plasticity. Finally, we consider the future directions of neuroepigenetic research as it relates to neuronal storage of information.
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Affiliation(s)
- Iva B Zovkic
- Department of Neurobiology and Evelyn F McKnight Brain Institute, University of Alabama at Birmingham, Birmingham, Alabama 35294, USA
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Rusiecki JA, Byrne C, Galdzicki Z, Srikantan V, Chen L, Poulin M, Yan L, Baccarelli A. PTSD and DNA Methylation in Select Immune Function Gene Promoter Regions: A Repeated Measures Case-Control Study of U.S. Military Service Members. Front Psychiatry 2013; 4:56. [PMID: 23805108 PMCID: PMC3690381 DOI: 10.3389/fpsyt.2013.00056] [Citation(s) in RCA: 76] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/07/2013] [Accepted: 06/02/2013] [Indexed: 01/13/2023] Open
Abstract
BACKGROUND The underlying molecular mechanisms of PTSD are largely unknown. Distinct expression signatures for PTSD have been found, in particular for immune activation transcripts. DNA methylation may be significant in the pathophysiology of PTSD, since the process is intrinsically linked to gene expression. We evaluated temporal changes in DNA methylation in select promoter regions of immune system-related genes in U.S. military service members with a PTSD diagnosis, pre- and post-diagnosis, and in controls. METHODS Cases (n = 75) had a post-deployment diagnosis of PTSD in their medical record. Controls (n = 75) were randomly selected service members with no PTSD diagnosis. DNA was extracted from pre- and post-deployment sera. DNA methylation (%5-mC) was quantified at specific CpG sites in promoter regions of insulin-like growth factor 2 (IGF2), long non-coding RNA transcript H19, interleukin-8 (IL8), IL16, and IL18 via pyrosequencing. We used multivariate analysis of variance and generalized linear models to calculate adjusted means (adjusted for age, gender, and race) to make temporal comparisons of %5-mC for cases (pre- to post-deployment) versus controls (pre- to post-deployment). RESULTS There were significant differences in the change of %5-mC pre- to post-deployment between cases and controls for H19 (cases: +0.57%, controls: -1.97%; p = 0.04) and IL18 (cases: +1.39%, controls: -3.83%; p = 0.01). For H19 the difference was driven by a significant reduction in %5-mC among controls; for IL18 the difference was driven by both a reduction in %5-mC among controls and an increase in %5-mC among cases. Stratified analyses revealed more pronounced differences in the adjusted means of pre-post H19 and IL18 methylation differences for cases versus controls among older service members, males, service members of white race, and those with shorter deployments (6-12 months). CONCLUSION In the study of deployed personnel, those who did not develop PTSD had reduced %5-mC levels of H19 and IL18 after deployment, while those who did develop PTSD had increased levels of IL18. Additionally, pre-deployment the people who later became cases had lower levels of IL18 %5-mC compared with controls. These findings are preliminary and should be investigated in larger studies.
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Affiliation(s)
- Jennifer A Rusiecki
- Department of Preventive Medicine, School of Medicine, Uniformed Services University , Bethesda, MD , USA
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Affiliation(s)
- Schahram Akbarian
- Departments of Neuroscience and Psychiatry, Friedman Brain Institute, Mount Sinai School of Medicine, New York, NY, USA. E-mail: or
| | - Eric J Nestler
- Departments of Neuroscience and Psychiatry, Friedman Brain Institute, Mount Sinai School of Medicine, New York, NY, USA. E-mail: or
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Nabel EM, Morishita H. Regulating critical period plasticity: insight from the visual system to fear circuitry for therapeutic interventions. Front Psychiatry 2013; 4:146. [PMID: 24273519 PMCID: PMC3822369 DOI: 10.3389/fpsyt.2013.00146] [Citation(s) in RCA: 57] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/13/2013] [Accepted: 10/25/2013] [Indexed: 11/13/2022] Open
Abstract
Early temporary windows of heightened brain plasticity called critical periods developmentally sculpt neural circuits and contribute to adult behavior. Regulatory mechanisms of visual cortex development - the preeminent model of experience-dependent critical period plasticity-actively limit adult plasticity and have proved fruitful therapeutic targets to reopen plasticity and rewire faulty visual system connections later in life. Interestingly, these molecular mechanisms have been implicated in the regulation of plasticity in other functions beyond vision. Applying mechanistic understandings of critical period plasticity in the visual cortex to fear circuitry may provide a conceptual framework for developing novel therapeutic tools to mitigate aberrant fear responses in post traumatic stress disorder. In this review, we turn to the model of experience-dependent visual plasticity to provide novel insights for the mechanisms regulating plasticity in the fear system. Fear circuitry, particularly fear memory erasure, also undergoes age-related changes in experience-dependent plasticity. We consider the contributions of molecular brakes that halt visual critical period plasticity to circuitry underlying fear memory erasure. A major molecular brake in the visual cortex, perineuronal net formation, recently has been identified in the development of fear systems that are resilient to fear memory erasure. The roles of other molecular brakes, myelin-related Nogo receptor signaling and Lynx family proteins - endogenous inhibitors for nicotinic acetylcholine receptor, are explored in the context of fear memory plasticity. Such fear plasticity regulators, including epigenetic effects, provide promising targets for therapeutic interventions.
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Affiliation(s)
- Elisa M Nabel
- Graduate School of Biomedical Sciences, Icahn School of Medicine at Mount Sinai , New York, NY , USA
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Maddox SA, Schafe GE, Ressler KJ. Exploring epigenetic regulation of fear memory and biomarkers associated with post-traumatic stress disorder. Front Psychiatry 2013; 4:62. [PMID: 23847551 PMCID: PMC3697031 DOI: 10.3389/fpsyt.2013.00062] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/30/2013] [Accepted: 06/13/2013] [Indexed: 12/21/2022] Open
Abstract
This review examines recent work on epigenetic mechanisms underlying animal models of fear learning as well as its translational implications in disorders of fear regulation, such as Post-traumatic Stress Disorder (PTSD). Specifically, we will examine work outlining roles of differential histone acetylation and DNA-methylation associated with consolidation, reconsolidation, and extinction in Pavlovian fear paradigms. We then focus on the numerous studies examining the epigenetic modifications of the Brain-derived neurotrophin factor (BDNF) pathway and the extension of these findings from animal models to recent work in human clinical populations. We will also review recently published data on FKBP5 regulation of glucocorticoid receptor function, and how this is modulated in animal models of PTSD and in human clinical populations via epigenetic mechanisms. As glucocorticoid regulation of memory consolidation is well established in fear models, we examine how these recent data contribute to our broader understanding of fear memory formation. The combined recent progress in epigenetic modulation of memory with the advances in fear neurobiology suggest that this area may be critical to progress in our understanding of fear-related disorders with implications for new approaches to treatment and prevention.
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Affiliation(s)
- Stephanie A Maddox
- Yerkes National Primate Research Center , Atlanta, GA , USA ; Department of Psychiatry and Behavioral Sciences, Emory University School of Medicine , Atlanta, GA , USA
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Zovkic IB, Meadows JP, Kaas GA, Sweatt JD. Interindividual Variability in Stress Susceptibility: A Role for Epigenetic Mechanisms in PTSD. Front Psychiatry 2013; 4:60. [PMID: 23805109 PMCID: PMC3693073 DOI: 10.3389/fpsyt.2013.00060] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/30/2013] [Accepted: 06/11/2013] [Indexed: 12/13/2022] Open
Abstract
Post-traumatic stress disorder (PTSD) is a psychiatric condition characterized by intrusive and persistent memories of a psychologically traumatic event that leads to significant functional and social impairment in affected individuals. The molecular bases underlying persistent outcomes of a transient traumatic event have remained elusive for many years, but recent studies in rodents have implicated epigenetic modifications of chromatin structure and DNA methylation as fundamental mechanisms for the induction and stabilization of fear memory. In addition to mediating adaptations to traumatic events that ultimately cause PTSD, epigenetic mechanisms are also involved in establishing individual differences in PTSD risk and resilience by mediating long-lasting effects of genes and early environment on adult function and behavior. In this review, we discuss the current evidence for epigenetic regulation of PTSD in human studies and in animal models and comment on ways in which these models can be expanded. In addition, we identify key outstanding questions in the study of epigenetic mechanisms of PTSD in the context of rapidly evolving technologies that are constantly updating and adjusting our understanding of epigenetic modifications and their functional roles. Finally, we discuss the potential application of epigenetic approaches in identifying markers of risk and resilience that can be utilized to promote early intervention and develop therapeutic strategies to combat PTSD after symptom onset.
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Affiliation(s)
- Iva B Zovkic
- Department of Neurobiology, Evelyn F. McKnight Brain Institute, University of Alabama at Birmingham , Birmingham, AL , USA
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