151
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Bousiges O, Neidl R, Majchrzak M, Muller MA, Barbelivien A, Pereira de Vasconcelos A, Schneider A, Loeffler JP, Cassel JC, Boutillier AL. Detection of histone acetylation levels in the dorsal hippocampus reveals early tagging on specific residues of H2B and H4 histones in response to learning. PLoS One 2013; 8:e57816. [PMID: 23469244 PMCID: PMC3587615 DOI: 10.1371/journal.pone.0057816] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2012] [Accepted: 01/26/2013] [Indexed: 12/21/2022] Open
Abstract
The recent literature provides evidence that epigenetic mechanisms such as DNA methylation and histone modification are crucial to gene transcription linked to synaptic plasticity in the mammalian brain--notably in the hippocampus--and memory formation. We measured global histone acetylation levels in the rat hippocampus at an early stage of spatial or fear memory formation. We found that H3, H4 and H2B underwent differential acetylation at specific sites depending on whether rats had been exposed to the context of a task without having to learn or had to learn about a place or fear therein: H3K9K14 acetylation was mostly responsive to any experimental conditions compared to naive animals, whereas H2B N-terminus and H4K12 acetylations were mostly associated with memory for either spatial or fear learning. Altogether, these data suggest that behavior/experience-dependent changes differently regulate specific acetylation modifications of histones in the hippocampus, depending on whether a memory trace is established or not: tagging of H3K9K14 could be associated with perception/processing of testing-related manipulations and context, thereby enhancing chromatin accessibility, while tagging of H2B N-terminus tail and H4K12 could be more closely associated with the formation of memories requiring an engagement of the hippocampus.
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Affiliation(s)
- Olivier Bousiges
- Laboratoire de Neurosciences Cognitives et Adaptatives, UMR7364, Université de Strasbourg-CNRS, GDR CNRS 2905, Faculté de Psychologie, Strasbourg, France
| | - Romain Neidl
- Laboratoire de Neurosciences Cognitives et Adaptatives, UMR7364, Université de Strasbourg-CNRS, GDR CNRS 2905, Faculté de Psychologie, Strasbourg, France
| | - Monique Majchrzak
- Laboratoire de Neurosciences Cognitives et Adaptatives, UMR7364, Université de Strasbourg-CNRS, GDR CNRS 2905, Faculté de Psychologie, Strasbourg, France
| | - Marc-Antoine Muller
- Laboratoire de Neurosciences Cognitives et Adaptatives, UMR7364, Université de Strasbourg-CNRS, GDR CNRS 2905, Faculté de Psychologie, Strasbourg, France
| | - Alexandra Barbelivien
- Laboratoire de Neurosciences Cognitives et Adaptatives, UMR7364, Université de Strasbourg-CNRS, GDR CNRS 2905, Faculté de Psychologie, Strasbourg, France
| | - Anne Pereira de Vasconcelos
- Laboratoire de Neurosciences Cognitives et Adaptatives, UMR7364, Université de Strasbourg-CNRS, GDR CNRS 2905, Faculté de Psychologie, Strasbourg, France
| | - Anne Schneider
- Laboratoire de Neurosciences Cognitives et Adaptatives, UMR7364, Université de Strasbourg-CNRS, GDR CNRS 2905, Faculté de Psychologie, Strasbourg, France
| | - Jean-Philippe Loeffler
- Inserm, U692, Laboratoire de Signalisations Moléculaires et Neurodégénérescence, Université de Strasbourg, Faculté de Médecine, UMRS692, Strasbourg, France
| | - Jean-Christophe Cassel
- Laboratoire de Neurosciences Cognitives et Adaptatives, UMR7364, Université de Strasbourg-CNRS, GDR CNRS 2905, Faculté de Psychologie, Strasbourg, France
| | - Anne-Laurence Boutillier
- Laboratoire de Neurosciences Cognitives et Adaptatives, UMR7364, Université de Strasbourg-CNRS, GDR CNRS 2905, Faculté de Psychologie, Strasbourg, France
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152
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Haettig J, Sun Y, Wood MA, Xu X. Cell-type specific inactivation of hippocampal CA1 disrupts location-dependent object recognition in the mouse. Learn Mem 2013; 20:139-46. [PMID: 23418393 DOI: 10.1101/lm.027847.112] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
The allatostatin receptor (AlstR)/ligand inactivation system enables potent regulation of neuronal circuit activity. To examine how different cell types participate in memory formation, we have used this system through Cre-directed, cell-type specific expression in mouse hippocampal CA1 in vivo and examined functional effects of inactivation of excitatory vs. inhibitory neurons on memory formation. We chose to use a hippocampus-dependent behavioral task involving location-dependent object recognition (LOR). The double transgenic mice, with the AlstRs selectively expressed in excitatory pyramidal neurons or inhibitory interneurons, were cannulated, targeting dorsal hippocampus to allow the infusion of the receptor ligand (the allatostatin [AL] peptide) in a time dependent manner. Compared to control animals, AL-infused animals showed no long-term memory for object location. While inactivation of excitatory or inhibitory neurons produced opposite effects on hippocampal circuit activity in vitro, the effects in vivo were similar. Both types of inactivation experiments resulted in mice exhibiting no long-term memory for object location. Together, these results demonstrate that the Cre-directed, AlstR-based system is a powerful tool for cell-type specific manipulations in a behaving animal and suggest that activity of either excitatory neurons or inhibitory interneurons is essential for proper long-term object location memory formation.
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Affiliation(s)
- Jakob Haettig
- Department of Neurobiology and Behavior, University of California Irvine, Irvine, CA 92697-3800, USA
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153
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Malvaez M, McQuown SC, Rogge GA, Astarabadi M, Jacques V, Carreiro S, Rusche JR, Wood MA. HDAC3-selective inhibitor enhances extinction of cocaine-seeking behavior in a persistent manner. Proc Natl Acad Sci U S A 2013; 110:2647-52. [PMID: 23297220 PMCID: PMC3574934 DOI: 10.1073/pnas.1213364110] [Citation(s) in RCA: 314] [Impact Index Per Article: 28.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
Nonspecific histone deacetylase (HDAC) inhibition has been shown to facilitate the extinction of drug-seeking behavior in a manner resistant to reinstatement. A key open question is which specific HDAC is involved in the extinction of drug-seeking behavior. Using the selective HDAC3 inhibitor RGFP966, we investigated the role of HDAC3 in extinction and found that systemic treatment with RGFP966 facilitates extinction in mice in a manner resistant to reinstatement. We also investigated whether the facilitated extinction is related to the enhancement of extinction consolidation during extinction learning or to negative effects on performance or reconsolidation. These are key distinctions with regard to any compound being used to modulate extinction, because a more rapid decrease in a defined behavior is interpreted as facilitated extinction. Using an innovative combination of behavioral paradigms, we found that a single treatment of RGFP966 enhances extinction of a previously established cocaine-conditioned place preference, while simultaneously enhancing long-term object-location memory within subjects. During extinction consolidation, HDAC3 inhibition promotes a distinct pattern of histone acetylation linked to gene expression within the infralimbic cortex, hippocampus, and nucleus accumbens. Thus, the facilitated extinction of drug-seeking cannot be explained by adverse effects on performance. These results demonstrate that HDAC3 inhibition enhances the memory processes involved in extinction of drug-seeking behavior.
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Affiliation(s)
- Melissa Malvaez
- Department of Neurobiology and Behavior, Center for the Neurobiology of Learning and Memory, University of California, Irvine, CA 92697
| | - Susan C. McQuown
- Department of Neurobiology and Behavior, Center for the Neurobiology of Learning and Memory, University of California, Irvine, CA 92697
- Dart NeuroScience, San Diego, CA 92121; and
| | - George A. Rogge
- Department of Neurobiology and Behavior, Center for the Neurobiology of Learning and Memory, University of California, Irvine, CA 92697
| | - Mariam Astarabadi
- Department of Neurobiology and Behavior, Center for the Neurobiology of Learning and Memory, University of California, Irvine, CA 92697
| | | | | | | | - Marcelo A. Wood
- Department of Neurobiology and Behavior, Center for the Neurobiology of Learning and Memory, University of California, Irvine, CA 92697
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154
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Gräff J, Tsai LH. Histone acetylation: molecular mnemonics on the chromatin. Nat Rev Neurosci 2013; 14:97-111. [PMID: 23324667 DOI: 10.1038/nrn3427] [Citation(s) in RCA: 446] [Impact Index Per Article: 40.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Long-lasting memories require specific gene expression programmes that are, in part, orchestrated by epigenetic mechanisms. Of the epigenetic modifications identified in cognitive processes, histone acetylation has spurred considerable interest. Whereas increments in histone acetylation have consistently been shown to favour learning and memory, a lack thereof has been causally implicated in cognitive impairments in neurodevelopmental disorders, neurodegeneration and ageing. As histone acetylation and cognitive functions can be pharmacologically restored by histone deacetylase inhibitors, this epigenetic modification might constitute a molecular memory aid on the chromatin and, by extension, a new template for therapeutic interventions against cognitive frailty.
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Affiliation(s)
- Johannes Gräff
- Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
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155
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Social defeat induces changes in histone acetylation and expression of histone modifying enzymes in the ventral hippocampus, prefrontal cortex, and dorsal raphe nucleus. Neuroscience 2013; 264:88-98. [PMID: 23370319 DOI: 10.1016/j.neuroscience.2013.01.024] [Citation(s) in RCA: 57] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2012] [Revised: 01/09/2013] [Accepted: 01/14/2013] [Indexed: 12/12/2022]
Abstract
Chronic exposure to stress is associated with a number of psychiatric disorders, but little is known about the epigenetic mechanisms that underlie the stress response or resilience to chronic stress. We investigated histone acetylation in seven different brain regions of rats exposed to chronic social defeat stress: the dorsal hippocampus (dHPC), ventral hippocampus (vHPC), medial prefrontal cortex (mPFC), basolateral amygdala (BLA), locus coeruleus (LC), paraventricular thalamus (PVT), and dorsal raphe (DR) nucleus. This stress paradigm was unique in that it allowed rats to display resilience in the form of an active coping mechanism. We found that there was an increase in acetylation of H3K9/14 (H3K9/14ac) and bulk acetylation of H4K5,8,12,16 (H4K5,8,12,16ac) in the DR nucleus of rats that were less resilient. Less resilient rats also displayed increased levels of H3K18 acetylation (H3K18ac) in the mPFC when compared to non-stressed controls. In the vHPC, there was an increase in H3K18ac and H4K12 (H4K12ac) in rats that were less resilient when compared to non-stressed control rats. In addition, there was a decrease in levels of H4K8 acetylation (H4K8ac) in both resilient and non-resilient rats as compared to controls. We assessed expression of histone modifying enzymes in the vHPC and the mPFC using quantitative real-time polymerase chain reaction (PCR) and found changes in expression of a number of targets. These included changes in Sirt1 and Sirt2 in the vHPC and changes in Kat5 in the mPFC. Overall, these results suggest that changes in histone acetylation and expression of histone modifying enzymes in these regions correlate with the behavioral response to stress in socially defeated rats.
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156
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A naturally-occurring histone acetyltransferase inhibitor derived from Garcinia indica impairs newly acquired and reactivated fear memories. PLoS One 2013; 8:e54463. [PMID: 23349897 PMCID: PMC3549978 DOI: 10.1371/journal.pone.0054463] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2012] [Accepted: 12/11/2012] [Indexed: 01/31/2023] Open
Abstract
The study of the cellular and molecular mechanisms underlying the consolidation and reconsolidation of traumatic fear memories has progressed rapidly in recent years, yet few compounds have emerged that are readily useful in a clinical setting for the treatment of anxiety disorders such as post-traumatic stress disorder (PTSD). Here, we use a combination of biochemical, behavioral, and neurophysiological methods to systematically investigate the ability of garcinol, a naturally-occurring histone acetyltransferase (HAT) inhibitor derived from the rind of the fruit of the Kokum tree (Garcina indica), to disrupt the consolidation and reconsolidation of Pavlovian fear conditioning, a widely studied rodent model of PTSD. We show that local infusion of garcinol into the rat lateral amygdala (LA) impairs the training and retrieval-related acetylation of histone H3 in the LA. Further, we show that either intra-LA or systemic administration of garcinol within a narrow window after either fear conditioning or fear memory retrieval significantly impairs the consolidation and reconsolidation of a Pavlovian fear memory and associated neural plasticity in the LA. Our findings suggest that a naturally-occurring compound derived from the diet that regulates chromatin function may be useful in the treatment of newly acquired or recently reactivated traumatic memories.
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157
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Maddox SA, Watts CS, Schafe GE. p300/CBP histone acetyltransferase activity is required for newly acquired and reactivated fear memories in the lateral amygdala. Learn Mem 2013; 20:109-19. [PMID: 23328899 DOI: 10.1101/lm.029157.112] [Citation(s) in RCA: 68] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Modifications in chromatin structure have been widely implicated in memory and cognition, most notably using hippocampal-dependent memory paradigms including object recognition, spatial memory, and contextual fear memory. Relatively little is known, however, about the role of chromatin-modifying enzymes in amygdala-dependent memory formation. Here, we use a combination of biochemical, behavioral, and neurophysiological methods to systematically examine the role of p300/CBP histone acetyltransferase (HAT) activity in the consolidation and reconsolidation of auditory Pavlovian fear memories. We show that local infusions of c646, a selective pharmacological inhibitor of p300/CBP activity, shortly following either fear conditioning or fear memory retrieval impair training and retrieval-related regulation of histone acetylation in the lateral nucleus of the amygdala (LA). Furthermore, we show that intra-LA infusion of c646 significantly impairs fear memory consolidation, reconsolidation, and associated neural plasticity in the LA. Our findings collectively suggest that p300/CBP HAT activity is critical for the consolidation and reconsolidation of amygdala-dependent Pavlovian fear memories.
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Affiliation(s)
- Stephanie A Maddox
- Department of Psychology, Yale University, New Haven, Connecticut 06520, USA
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158
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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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159
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Rudenko A, Tsai LH. Epigenetic regulation in memory and cognitive disorders. Neuroscience 2013; 264:51-63. [PMID: 23291453 DOI: 10.1016/j.neuroscience.2012.12.034] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2012] [Revised: 12/18/2012] [Accepted: 12/19/2012] [Indexed: 01/29/2023]
Abstract
While the importance of epigenetic mechanisms is well established for numerous aspects of cell differentiation and development, recent findings have shown epigenetic processes to be a critical regulatory component in postmitotic neurons. Particularly intriguing, and potentially significant, are data demonstrating epigenetic regulation of cognitive behaviors. Different aspects of learning and memory appear to be regulated at the level of epigenetic chromatin modifications. Furthermore, it is becoming clear that the dysfunction of epigenetic mechanisms can lead to various disorders accompanied by significant mental impairment. Here, we review the evidence for the epigenetic control of cognition and the role of epigenetic dysregulation in mental disorders. A better understanding of epigenetic mechanisms will increase our fundamental knowledge of cognition and also provide new and exciting avenues of treatment for various mental disorders.
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Affiliation(s)
- A Rudenko
- Picower Institute for Learning and Memory, Department of Brain and Cognitive Sciences, Howard Hughes Medical Institute, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139, USA.
| | - L-H Tsai
- Picower Institute for Learning and Memory, Department of Brain and Cognitive Sciences, Howard Hughes Medical Institute, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139, USA
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160
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Abstract
Long-term memory formation requires transcription and protein synthesis. Over the past few decades, a great amount of knowledge has been gained regarding the molecular players that regulate the transcriptional program linked to memory consolidation. Epigenetic mechanisms have been shown to be essential for the regulation of neuronal gene expression, and histone acetylation has been one of the most studied and best characterized. In this review, we summarize the lines of evidence that have shown the relevance of histone acetylation in memory in both physiological and pathological conditions. Great advances have been made in identifying the writers and erasers of histone acetylation marks during learning. However, the identities of the upstream regulators and downstream targets that mediate the effect of changes in histone acetylation during memory consolidation remain restricted to a handful of molecules. We outline a general model by which corepressors and coactivators regulate histone acetylation during memory storage and discuss how the recent advances in high-throughput sequencing have the potential to radically change our understanding of how epigenetic control operates in the brain.
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Affiliation(s)
- Lucia Peixoto
- Department of Biology, School of Arts and Sciences, University of Pennsylvania, Philadelphia, PA, USA
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161
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Abstract
How do drugs of abuse, such as cocaine, cause stable changes in neural plasticity that in turn drive long-term changes in behavior? What kind of mechanism can underlie such stable changes in neural plasticity? One prime candidate mechanism is epigenetic mechanisms of chromatin regulation. Chromatin regulation has been shown to generate short-term and long-term molecular memory within an individual cell. They have also been shown to underlie cell fate decisions (or cellular memory). Now, there is accumulating evidence that in the CNS, these same mechanisms may be pivotal for drug-induced changes in gene expression and ultimately long-term behavioral changes. As these mechanisms are also being found to be fundamental for learning and memory, an exciting new possibility is the extinction of drug-seeking behavior by manipulation of epigenetic mechanisms. In this review, we critically discuss the evidence demonstrating a key role for chromatin regulation via histone acetylation in cocaine action.
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162
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Selvi BR, Chatterjee S, Modak R, Eswaramoorthy M, Kundu TK. Histone acetylation as a therapeutic target. Subcell Biochem 2013; 61:567-596. [PMID: 23150268 DOI: 10.1007/978-94-007-4525-4_25] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
The recent developments in the field of epigenetics have changed the way the covalent modifications were perceived from mere chemical tags to important biological recruiting platforms as well as decisive factors in the process of transcriptional regulation and gene expression. Over the years, the parallel investigations in the area of epigenetics and disease have also shown the significance of the epigenetic modifications as important regulatory nodes that exhibit dysfunction in disease states. In the present scenario where epigenetic therapy is also being considered at par with the conventional therapeutic strategies, this article reviews the role of histone acetylation as an epigenetic mark involved in different biological processes associated with normal as well as abnormal gene expression states, modulation of this acetylation by small molecules and warrants the possibility of acetylation as a therapeutic target.
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Affiliation(s)
- B Ruthrotha Selvi
- Transcription and Disease Laboratory, Molecular Biology and Genetics Unit, Jawaharlal Nehru Centre for Advanced Scientific Research, Jakkur, P.O., Bangalore, 560 064, India
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163
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Zheng F, Zhou X, Moon C, Wang H. Regulation of brain-derived neurotrophic factor expression in neurons. INTERNATIONAL JOURNAL OF PHYSIOLOGY, PATHOPHYSIOLOGY AND PHARMACOLOGY 2012; 4:188-200. [PMID: 23320132 PMCID: PMC3544221] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Subscribe] [Scholar Register] [Received: 12/03/2012] [Accepted: 12/22/2012] [Indexed: 06/01/2023]
Abstract
Brain-derived neurotrophic factor (BDNF) plays critical roles in many aspects of brain functions, including cell survival, differentiation, development, learning and memory. Aberrant BDNF expression has also been implicated in numerous neurological disorders. Thus, significant effort has been made to understand how BDNF transcription as well as translation is regulated. Interestingly, the BDNF gene structure suggests that multiple promoters control its transcription, leading to the existence of distinct mRNA species. Further, the long- and short-tail of the 3'un-translated region may dictate different sub-cellular BDNF mRNA targeting and translational responses following neuronal stimulation. This review aims to summarize the main findings that demonstrate how neuronal activities specifically up-regulate the transcription and translation of unique BDNF transcripts. We also discuss some of the recent reports that emphasize the epigenetic regulation of BDNF transcription.
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Affiliation(s)
- Fei Zheng
- Department of Biochemistry, St. Jude Children’s Research HospitalMemphis, TN38105, USA
| | - Xianju Zhou
- Department of Neurology, Changzhou No. 2 People’s Hospital, The affiliated Hospital of Nanjing Medical University29 Xinglong Alley, Changzhou, 213003, People’s Republic of China
| | - Changjong Moon
- College of Veterinary Medicine, Chonnam National University and Animal Medical InstituteGwangju 500-757, South Korea
| | - Hongbing Wang
- Department of Physiology, Neuroscience Program, Michigan State UniversityEast Lansing, MI 48824, USA
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164
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Millan MJ. An epigenetic framework for neurodevelopmental disorders: from pathogenesis to potential therapy. Neuropharmacology 2012; 68:2-82. [PMID: 23246909 DOI: 10.1016/j.neuropharm.2012.11.015] [Citation(s) in RCA: 151] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2012] [Revised: 11/11/2012] [Accepted: 11/22/2012] [Indexed: 12/12/2022]
Abstract
Neurodevelopmental disorders (NDDs) are characterized by aberrant and delayed early-life development of the brain, leading to deficits in language, cognition, motor behaviour and other functional domains, often accompanied by somatic symptoms. Environmental factors like perinatal infection, malnutrition and trauma can increase the risk of the heterogeneous, multifactorial and polygenic disorders, autism and schizophrenia. Conversely, discrete genetic anomalies are involved in Down, Rett and Fragile X syndromes, tuberous sclerosis and neurofibromatosis, the less familiar Phelan-McDermid, Sotos, Kleefstra, Coffin-Lowry and "ATRX" syndromes, and the disorders of imprinting, Angelman and Prader-Willi syndromes. NDDs have been termed "synaptopathies" in reference to structural and functional disturbance of synaptic plasticity, several involve abnormal Ras-Kinase signalling ("rasopathies"), and many are characterized by disrupted cerebral connectivity and an imbalance between excitatory and inhibitory transmission. However, at a different level of integration, NDDs are accompanied by aberrant "epigenetic" regulation of processes critical for normal and orderly development of the brain. Epigenetics refers to potentially-heritable (by mitosis and/or meiosis) mechanisms controlling gene expression without changes in DNA sequence. In certain NDDs, prototypical epigenetic processes of DNA methylation and covalent histone marking are impacted. Conversely, others involve anomalies in chromatin-modelling, mRNA splicing/editing, mRNA translation, ribosome biogenesis and/or the regulatory actions of small nucleolar RNAs and micro-RNAs. Since epigenetic mechanisms are modifiable, this raises the hope of novel therapy, though questions remain concerning efficacy and safety. The above issues are critically surveyed in this review, which advocates a broad-based epigenetic framework for understanding and ultimately treating a diverse assemblage of NDDs ("epigenopathies") lying at the interface of genetic, developmental and environmental processes. This article is part of the Special Issue entitled 'Neurodevelopmental Disorders'.
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Affiliation(s)
- Mark J Millan
- Unit for Research and Discovery in Neuroscience, IDR Servier, 125 chemin de ronde, 78290 Croissy sur Seine, Paris, France.
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165
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Integrin dynamics produce a delayed stage of long-term potentiation and memory consolidation. J Neurosci 2012; 32:12854-61. [PMID: 22973009 DOI: 10.1523/jneurosci.2024-12.2012] [Citation(s) in RCA: 73] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Memory consolidation theory posits that newly acquired information passes through a series of stabilization steps before being firmly encoded. We report here that in rat and mouse, hippocampus cell adhesion receptors belonging to the β1-integrin family exhibit dynamic properties in adult synapses and that these contribute importantly to a previously unidentified stage of consolidation. Quantitative dual immunofluorescence microscopy showed that induction of long-term potentiation (LTP) by theta burst stimulation (TBS) activates β1 integrins, and integrin-signaling kinases, at spine synapses in adult hippocampal slices. Neutralizing antisera selective for β1 integrins blocked these effects. TBS-induced integrin activation was brief (<7 min) and followed by an ∼45 min period during which the adhesion receptors did not respond to a second application of TBS. Brefeldin A, which blocks integrin trafficking to the plasma membrane, prevented the delayed recovery of integrin responses to TBS. β1 integrin-neutralizing antisera erased LTP when applied during, but not after, the return of integrin responsivity. Similarly, infusions of anti-β1 into rostral mouse hippocampus blocked formation of long-term, object location memory when started 20 min after learning but not 40 min later. The finding that β1 integrin neutralization was effective in the same time window for slice and behavioral experiments strongly suggests that integrin recovery triggers a temporally discrete, previously undetected second stage of consolidation for both LTP and memory.
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166
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Blaze J, Roth TL. Epigenetic mechanisms in learning and memory. WILEY INTERDISCIPLINARY REVIEWS. COGNITIVE SCIENCE 2012; 4:105-115. [DOI: 10.1002/wcs.1205] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
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167
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Fass DM, Reis SA, Ghosh B, Hennig KM, Joseph NF, Zhao WN, Nieland TJF, Guan JS, Kuhnle CEG, Tang W, Barker DD, Mazitschek R, Schreiber SL, Tsai LH, Haggarty SJ. Crebinostat: a novel cognitive enhancer that inhibits histone deacetylase activity and modulates chromatin-mediated neuroplasticity. Neuropharmacology 2012; 64:81-96. [PMID: 22771460 DOI: 10.1016/j.neuropharm.2012.06.043] [Citation(s) in RCA: 69] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2012] [Revised: 06/06/2012] [Accepted: 06/21/2012] [Indexed: 12/16/2022]
Abstract
Long-term memory formation is known to be critically dependent upon de novo gene expression in the brain. As a consequence, pharmacological enhancement of the transcriptional processes mediating long-term memory formation provides a potential therapeutic strategy for cognitive disorders involving aberrant neuroplasticity. Here we focus on the identification and characterization of small molecule inhibitors of histone deacetylases (HDACs) as enhancers of CREB (cAMP response element-binding protein)-regulated transcription and modulators of chromatin-mediated neuroplasticity. Using a CREB reporter gene cell line, we screened a library of small molecules structurally related to known HDAC inhibitors leading to the identification of a probe we termed crebinostat that produced robust activation of CREB-mediated transcription. Further characterization of crebinostat revealed its potent inhibition of the deacetylase activity of recombinant class I HDACs 1, 2, 3, and class IIb HDAC6, with weaker inhibition of the class I HDAC8 and no significant inhibition of the class IIa HDACs 4, 5, 7, and 9. In cultured mouse primary neurons, crebinostat potently induced acetylation of both histone H3 and histone H4 as well as enhanced the expression of the CREB target gene Egr1 (early growth response 1). Using a hippocampus-dependent, contextual fear conditioning paradigm, mice systemically administered crebinostat for a ten day time period exhibited enhanced memory. To gain insight into the molecular mechanisms of memory enhancement by HDAC inhibitors, whole genome transcriptome profiling of cultured mouse primary neurons treated with crebinostat, combined with bioinformatic analyses of CREB-target genes, was performed revealing a highly connected protein-protein interaction network reflecting modules of genes important to synaptic structure and plasticity. Consistent with these findings, crebinostat treatment increased the density of synapsin-1 punctae along dendrites in cultured neurons. Finally, crebinostat treatment of cultured mouse primary neurons was found to upregulate Bdnf (brain-derived neurotrophic factor) and Grn (granulin) and downregulate Mapt (tau) gene expression-genes implicated in aging-related cognitive decline and cognitive disorders. Taken together, these results demonstrate that crebinostat provides a novel probe to modulate chromatin-mediated neuroplasticity and further suggests that pharmacological optimization of selective of HDAC inhibitors may provide an effective therapeutic approach for human cognitive disorders. This article is part of a Special Issue entitled 'Cognitive Enhancers'.
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Affiliation(s)
- Daniel M Fass
- Center for Human Genetic Research, Massachusetts General Hospital, Department of Neurology, Harvard Medical School, 185 Cambridge Street, Boston, MA 02114, USA
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168
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Stafford JM, Raybuck JD, Ryabinin AE, Lattal KM. Increasing histone acetylation in the hippocampus-infralimbic network enhances fear extinction. Biol Psychiatry 2012; 72:25-33. [PMID: 22290116 PMCID: PMC3352991 DOI: 10.1016/j.biopsych.2011.12.012] [Citation(s) in RCA: 121] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/22/2011] [Revised: 12/13/2011] [Accepted: 12/15/2011] [Indexed: 10/14/2022]
Abstract
BACKGROUND A key finding from recent studies of epigenetic mechanisms of memory is that increasing histone acetylation after a learning experience enhances memory consolidation. This has been demonstrated in several preparations, but little is known about whether excitatory and inhibitory memories are equally sensitive to drugs that promote histone acetylation and how transcriptional changes in the hippocampal-medial prefrontal cortex network contribute to these drug effects. METHODS We compare the long-term behavioral consequences of systemic, intrahippocampal and intra-medial prefrontal cortex administration of the histone deacetylase inhibitor sodium butyrate (NaB) after contextual fear conditioning and extinction 1 and/or 14 days later in male c57BL/6J mice (n = 302). Levels of histone acetylation and expression of the product of the immediate-early gene c-Fos were assessed by immunohistochemistry following infusion of NaB into the hippocampus (n = 26). RESULTS Across a variety of conditions, the effects of NaB on extinction were larger and more persistent compared to the effects on initial memory formation. NaB administered following weak extinction induced behavioral extinction, infralimbic histone acetylation and c-Fos expression consistent with strong extinction. No similar effect was seen in the prelimbic cortex. The involvement of the infralimbic cortex was confirmed as infusions of NaB into the infralimbic, but not prelimbic cortex, induced extinction enhancements. CONCLUSIONS These studies show that the memory modulating ability of drugs that enhance acetylation is sensitive to a variety of behavioral and molecular conditions. We further identify transcriptional changes in the hippocampal-infralimbic circuit associated with extinction enhancements induced by the histone deacetylase inhibitor NaB.
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169
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Frick KM. Building a better hormone therapy? How understanding the rapid effects of sex steroid hormones could lead to new therapeutics for age-related memory decline. Behav Neurosci 2012; 126:29-53. [PMID: 22289043 DOI: 10.1037/a0026660] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
A wealth of data collected in recent decades has demonstrated that ovarian sex-steroid hormones, particularly 17β-estradiol (E2), are important trophic factors that regulate the function of cognitive regions of the brain such as the hippocampus. The loss of hormone cycling at menopause is associated with cognitive decline and dementia in women, and the onset of memory decline in animal models. However, hormone therapy is not currently recommended to prevent or treat cognitive decline, in part because of its detrimental side effects. In this article, it is proposed that investigations of the rapid effects of E2 on hippocampal function be used to further the design of new drugs that mimic the beneficial effects of E2 on memory without the side effects of current therapies. A conceptual model is presented for elucidating the molecular and biochemical mechanisms through which sex-steroid hormones modulate memory, and a specific hypothesis is proposed to account for the rapid memory-enhancing effects of E2. Empirical support for this hypothesis is discussed as a means of stimulating the consideration of new directions for the development of hormone-based therapies to preserve memory function in menopausal women.
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Affiliation(s)
- Karyn M Frick
- Department of Psychology, University of Wisconsin-Milwaukee, 2441 East Hartford Avenue, Milwaukee, WI 53211, USA.
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170
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He R, Eggert JA. The finger of an angel: memory return with epigenetic manipulation. Epigenomics 2012; 4:295-302. [DOI: 10.2217/epi.12.19] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
Scientists have been trying to crack the memory code for hundreds of years; however, centuries later, even the simplest elements of memory formation are still not fully understood. Recent studies in epigenetics indicate neuronal activity can induce transient reprogramming of epigenetic codes required for long-term memory consolidation. This suggests epigenetics as a basic mechanism in the regulation of long-term memory; and highlights the possibility that epigenetic modifications, as well as environmental factors, can change certain gene expression of brain neurons to restore the ability to remember, even with an aging brain or innate mental deficits. This article is an overview of basic knowledge and current research on epigenetic regulation of long-term memory, and prospects for future research.
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Affiliation(s)
- Ran He
- Healthcare Genetics Program, College of Health, Education & Human Development, Clemson University, Clemson, SC 29634, USA
| | - Julia A Eggert
- Healthcare Genetics Program, College of Health, Education & Human Development, Clemson University, Clemson, SC 29634, USA
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171
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Hippocampal histone acetylation regulates object recognition and the estradiol-induced enhancement of object recognition. J Neurosci 2012; 32:2344-51. [PMID: 22396409 DOI: 10.1523/jneurosci.5819-11.2012] [Citation(s) in RCA: 97] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Histone acetylation has recently been implicated in learning and memory processes, yet necessity of histone acetylation for such processes has not been demonstrated using pharmacological inhibitors of histone acetyltransferases (HATs). As such, the present study tested whether garcinol, a potent HAT inhibitor in vitro, could impair hippocampal memory consolidation and block the memory-enhancing effects of the modulatory hormone 17β-estradiol E2. We first showed that bilateral infusion of garcinol (0.1, 1, or 10 μg/side) into the dorsal hippocampus (DH) immediately after training impaired object recognition memory consolidation in ovariectomized female mice. A behaviorally effective dose of garcinol (10 μg/side) also significantly decreased DH HAT activity. We next examined whether DH infusion of a behaviorally subeffective dose of garcinol (1 ng/side) could block the effects of DH E2 infusion on object recognition and epigenetic processes. Immediately after training, ovariectomized female mice received bilateral DH infusions of vehicle, E2 (5 μg/side), garcinol (1 ng/side), or E2 plus garcinol. Forty-eight hours later, garcinol blocked the memory-enhancing effects of E2. Garcinol also reversed the E2-induced increase in DH histone H3 acetylation, HAT activity, and levels of the de novo methyltransferase DNMT3B, as well as the E2-induced decrease in levels of the memory repressor protein histone deacetylase 2. Collectively, these findings suggest that histone acetylation is critical for object recognition memory consolidation and the beneficial effects of E2 on object recognition. Importantly, this work demonstrates that the role of histone acetylation in memory processes can be studied using a HAT inhibitor.
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172
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CBP in the nucleus accumbens regulates cocaine-induced histone acetylation and is critical for cocaine-associated behaviors. J Neurosci 2012; 31:16941-8. [PMID: 22114264 DOI: 10.1523/jneurosci.2747-11.2011] [Citation(s) in RCA: 88] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
Cocaine exposure triggers molecular events that lead to long-lasting changes in brain structure and function. These changes can lead to the development of persistent and robust behavioral adaptations that characterize addiction. Recent evidence suggests the regulation of transcription via chromatin modification, such as histone acetylation, has an important role in the development of addictive behavior. Histone acetylation is regulated by histone acetyltransferases (HATs), which acetylate histones and promote transcription, and histone deacetylases (HDACs), which remove acetyl groups and silence transcription. Studies have demonstrated that HDACs may negatively regulate cocaine-induced behaviors, but very little is known about the role of specific HATs in long-lasting drug-induced plasticity. The histone acetyltransferase CREB-binding protein (CBP) mediates transcriptional activation by recruiting basal transcription machinery and acetylating histones. CBP is a critically important chromatin-modifying enzyme involved in regulating gene expression required for long-term plasticity and memory. However, the role of CBP in cocaine-induced behaviors remains largely unknown. We examined the role of CBP in drug-induced plasticity using CBP-FLOX genetically modified mice in combination with adeno-associated virus expressing Cre-recombinase to generate focal homozygous deletions of Cbp in the nucleus accumbens (NAc). A complete loss of CBP in NAc neurons results in decreased histone acetylation and significantly altered c-fos expression in response to cocaine. Furthermore, the deletion of CBP in the NAc correlates with significant impairments in cocaine sensitivity and context-cocaine associated memory. This is the first study to demonstrate a definitive role for CBP in modulating gene expression that may subserve drug-seeking behaviors.
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173
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Vogel-Ciernia A, Wood MA. Molecular brake pad hypothesis: pulling off the brakes for emotional memory. Rev Neurosci 2012; 23:607-26. [PMID: 23096102 PMCID: PMC4605538 DOI: 10.1515/revneuro-2012-0050] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2012] [Accepted: 07/05/2012] [Indexed: 12/31/2022]
Abstract
Under basal conditions histone deacetylases(HDACs) and their associated co-repressor complexes serve as molecular 'brake pads' to prevent the gene expression required for long-term memory formation. Following a learning event, HDACs and their co-repressor complexes are removed from a subset of specific gene promoters, allowing the histone acetylation and active gene expression required for long-term memory formation.Inhibition of HDACs increases histone acetylation,extends gene expression profiles, and allows for the formation of persistent long-term memories for training events that are otherwise forgotten. We propose that emotionally salient experiences have utilized this system to form strong and persistent memories for behaviorally significant events. Consequently, the presence or absence of HDACs at a selection of specific gene promoters could serve as a critical barrier for permitting the formation of long-term memories.
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Affiliation(s)
- Annie Vogel-Ciernia
- Department of Neurobiology and Behavior, Center for the Neurobiology of Learning and Memory, University of California Irvine Irvine, CA 92697–3800, USA
| | - Marcelo A. Wood
- Department of Neurobiology and Behavior, Center for the Neurobiology of Learning and Memory, University of California Irvine Irvine, CA 92697–3800, USA
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174
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Fitzsimons HL, Scott MJ. Genetic modulation of Rpd3 expression impairs long-term courtship memory in Drosophila. PLoS One 2011; 6:e29171. [PMID: 22195015 PMCID: PMC3240647 DOI: 10.1371/journal.pone.0029171] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2011] [Accepted: 11/22/2011] [Indexed: 12/18/2022] Open
Abstract
There is increasing evidence that regulation of local chromatin structure is a critical mechanism underlying the consolidation of long-term memory (LTM), however considerably less is understood about the specific mechanisms by which these epigenetic effects are mediated. Furthermore, the importance of histone acetylation in Drosophila memory has not been reported. The histone deacetylase (HDAC) Rpd3 is abundant in the adult fly brain, suggesting a post-mitotic function. Here, we investigated the role of Rpd3 in long-term courtship memory in Drosophila. We found that while modulation of Rpd3 levels predominantly in the adult mushroom body had no observed impact on immediate recall or one-hour memory, 24-hour LTM was severely impaired. Surprisingly, both overexpression as well as RNAi-mediated knockdown of Rpd3 resulted in impairment of long-term courtship memory, suggesting that the dose of Rpd3 is critical for normal LTM.
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Affiliation(s)
- Helen L Fitzsimons
- Institute of Molecular BioSciences, Massey University, Palmerston North, New Zealand.
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175
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Flici H, Erkosar B, Komonyi O, Karatas OF, Laneve P, Giangrande A. Gcm/Glide-dependent conversion into glia depends on neural stem cell age, but not on division, triggering a chromatin signature that is conserved in vertebrate glia. Development 2011; 138:4167-78. [PMID: 21852399 DOI: 10.1242/dev.070391] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Neurons and glia differentiate from multipotent precursors called neural stem cells (NSCs), upon the activation of specific transcription factors. In vitro, it has been shown that NSCs display very plastic features; however, one of the major challenges is to understand the bases of lineage restriction and NSC plasticity in vivo, at the cellular level. We show here that overexpression of the Gcm transcription factor, which controls the glial versus neuronal fate choice, fully and efficiently converts Drosophila NSCs towards the glial fate via an intermediate state. Gcm acts in a dose-dependent and autonomous manner by concomitantly repressing the endogenous program and inducing the glial program in the NSC. Most NSCs divide several times to build the embryonic nervous system and eventually enter quiescence: strikingly, the gliogenic potential of Gcm decreases with time and quiescent NSCs are resistant to fate conversion. Together with the fact that Gcm is able to convert mutant NSCs that cannot divide, this indicates that plasticity depends on temporal cues rather than on the mitotic potential. Finally, NSC plasticity involves specific chromatin modifications. The endogenous glial cells, as well as those induced by Gcm overexpression display low levels of histone 3 lysine 9 acetylation (H3K9ac) and Drosophila CREB-binding protein (dCBP) Histone Acetyl-Transferase (HAT). Moreover, we show that dCBP targets the H3K9 residue and that high levels of dCBP HAT disrupt gliogenesis. Thus, glial differentiation needs low levels of histone acetylation, a feature shared by vertebrate glia, calling for an epigenetic pathway conserved in evolution.
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Affiliation(s)
- Hakima Flici
- Institut de Génétique et de Biologie Moléculaire et Cellulaire, IGBMC/CNRS/INSERM/UDS, BP 10142, 67404 ILLKIRCH, CU de Strasbourg, France
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176
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CBP is required for environmental enrichment-induced neurogenesis and cognitive enhancement. EMBO J 2011; 30:4287-98. [PMID: 21847097 DOI: 10.1038/emboj.2011.299] [Citation(s) in RCA: 80] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2011] [Accepted: 07/25/2011] [Indexed: 12/18/2022] Open
Abstract
The epigenetic changes of the chromatin represent an attractive molecular substrate for adaptation to the environment. We examined here the role of CREB-binding protein (CBP), a histone acetyltransferase involved in mental retardation, in the genesis and maintenance of long-lasting systemic and behavioural adaptations to environmental enrichment (EE). Morphological and behavioural analyses demonstrated that EE ameliorates deficits associated to CBP deficiency. However, CBP-deficient mice also showed a strong defect in environment-induced neurogenesis and impaired EE-mediated enhancement of spatial navigation and pattern separation ability. These defects correlated with an attenuation of the transcriptional programme induced in response to EE and with deficits in histone acetylation at the promoters of EE-regulated, neurogenesis-related genes. Additional experiments in CBP restricted and inducible knockout mice indicated that environment-induced adult neurogenesis is extrinsically regulated by CBP function in mature granule cells. Overall, our experiments demonstrate that the environment alters gene expression by impinging on activities involved in modifying the epigenome and identify CBP-dependent transcriptional neuroadaptation as an important mediator of EE-induced benefits, a finding with important implications for mental retardation therapeutics.
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177
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Lester BM, Tronick E, Nestler E, Abel T, Kosofsky B, Kuzawa CW, Marsit CJ, Maze I, Meaney MJ, Monteggia LM, Reul JMHM, Skuse DH, Sweatt JD, Wood MA. Behavioral epigenetics. Ann N Y Acad Sci 2011; 1226:14-33. [PMID: 21615751 DOI: 10.1111/j.1749-6632.2011.06037.x] [Citation(s) in RCA: 107] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Sponsored by the New York Academy of Sciences, the Warren Alpert Medical School of Brown University and the University of Massachusetts Boston, "Behavioral Epigenetics" was held on October 29-30, 2010 at the University of Massachusetts Boston Campus Center, Boston, Massachusetts. This meeting featured speakers and panel discussions exploring the emerging field of behavioral epigenetics, from basic biochemical and cellular mechanisms to the epigenetic modulation of normative development, developmental disorders, and psychopathology. This report provides an overview of the research presented by leading scientists and lively discussion about the future of investigation at the behavioral epigenetic level.
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Affiliation(s)
- Barry M Lester
- Department of Psychiatry, Warren Alpert Medical School, Brown University, Women and Infants Hospital, Providence, Rhode Island 02908, USA.
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178
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179
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McQuown SC, Wood MA. HDAC3 and the molecular brake pad hypothesis. Neurobiol Learn Mem 2011; 96:27-34. [PMID: 21521655 DOI: 10.1016/j.nlm.2011.04.005] [Citation(s) in RCA: 101] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2010] [Revised: 03/25/2011] [Accepted: 04/08/2011] [Indexed: 12/26/2022]
Abstract
Successful transcription of specific genes required for long-term memory processes involves the orchestrated effort of not only transcription factors, but also very specific enzymatic protein complexes that modify chromatin structure. Chromatin modification has been identified as a pivotal molecular mechanism underlying certain forms of synaptic plasticity and memory. The best-studied form of chromatin modification in the learning and memory field is histone acetylation, which is regulated by histone acetyltransferases and histone deacetylases (HDACs). HDAC inhibitors have been shown to strongly enhance long-term memory processes, and recent work has aimed to identify contributions of individual HDACs. In this review, we focus on HDAC3 and discuss its recently defined role as a negative regulator of long-term memory formation. HDAC3 is part of a corepressor complex and has direct interactions with Class II HDACs that may be important for its molecular and behavioral consequences. And last, we propose the "molecular brake pad" hypothesis of HDAC function. The HDACs and associated corepressor complexes may function in neurons, in part, as "molecular brake pads." HDACs are localized to promoters of active genes and act as a persistent clamp that requires strong activity-dependent signaling to temporarily release these complexes (or brake pads) to activate gene expression required for long-term memory formation. Thus, HDAC inhibition removes the "molecular brake pads" constraining the processes necessary for long-term memory and results in strong, persistent memory formation.
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Affiliation(s)
- Susan C McQuown
- University of California, Irvine, Department of Neurobiology and Behavior, Center for the Neurobiology of Learning and Memory, Institute for Memory Impairments and Neurological Disorders, United States
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