251
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Prenatal and Perinatal Environmental Influences on the Human Fetal and Placental Epigenome. Clin Pharmacol Ther 2012; 92:716-26. [DOI: 10.1038/clpt.2012.141] [Citation(s) in RCA: 73] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
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252
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Conserved epigenetic sensitivity to early life experience in the rat and human hippocampus. Proc Natl Acad Sci U S A 2012; 109 Suppl 2:17266-72. [PMID: 23045659 DOI: 10.1073/pnas.1121260109] [Citation(s) in RCA: 232] [Impact Index Per Article: 19.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
Early life experience is associated with long-term effects on behavior and epigenetic programming of the NR3C1 (GLUCOCORTICOID RECEPTOR) gene in the hippocampus of both rats and humans. However, it is unlikely that such effects completely capture the evolutionarily conserved epigenetic mechanisms of early adaptation to environment. Here we present DNA methylation profiles spanning 6.5 million base pairs centered at the NR3C1 gene in the hippocampus of humans who experienced abuse as children and nonabused controls. We compare these profiles to corresponding DNA methylation profiles in rats that received differential levels of maternal care. The profiles of both species reveal hundreds of DNA methylation differences associated with early life experience distributed across the entire region in nonrandom patterns. For instance, methylation differences tend to cluster by genomic location, forming clusters covering as many as 1 million bases. Even more surprisingly, these differences seem to specifically target regulatory regions such as gene promoters, particularly those of the protocadherin α, β, and γ gene families. Beyond these high-level similarities, more detailed analyses reveal methylation differences likely stemming from the significant biological and environmental differences between species. These results provide support for an analogous cross-species epigenetic regulatory response at the level of the genomic region to early life experience.
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253
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Vialou V, Feng J, Robison AJ, Nestler EJ. Epigenetic mechanisms of depression and antidepressant action. Annu Rev Pharmacol Toxicol 2012; 53:59-87. [PMID: 23020296 DOI: 10.1146/annurev-pharmtox-010611-134540] [Citation(s) in RCA: 184] [Impact Index Per Article: 15.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Epigenetic mechanisms, which control chromatin structure and function, mediate changes in gene expression that occur in response to diverse stimuli. Recent research has established that environmental events and behavioral experience induce epigenetic changes at particular gene loci and that these changes help shape neuronal plasticity and function and hence behavior. Some of these changes can be stable and can even persist for a lifetime. Increasing evidence supports the hypothesis that aberrations in chromatin remodeling and subsequent effects on gene expression within limbic brain regions contribute to the pathogenesis of depression and other stress-related disorders such as post-traumatic stress disorder and other anxiety syndromes. Likewise, the gradually developing but persistent therapeutic effects of antidepressant medications may be achieved in part via epigenetic mechanisms. This review discusses recent advances in our understanding of the epigenetic regulation of stress-related disorders and focuses on three distinct aspects of stress-induced epigenetic pathology: the effects of stress and antidepressant treatment during adulthood, the lifelong effects of early-life stress on subsequent stress vulnerability, and the possible transgenerational transmission of stress-induced abnormalities.
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Affiliation(s)
- Vincent Vialou
- Fishberg Department of Neuroscience and Friedman Brain Institute, Mount Sinai School of Medicine, New York, New York 10029, USA
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254
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Niculescu MD, Lupu DS, Craciunescu CN. Perinatal manipulation of α-linolenic acid intake induces epigenetic changes in maternal and offspring livers. FASEB J 2012; 27:350-8. [PMID: 22997227 DOI: 10.1096/fj.12-210724] [Citation(s) in RCA: 74] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Previous studies indicated that the intake of α-linolenic acid (ALA) can alter the concentration of both ω-6 and ω-3 fatty acids in both mother and offspring, with consequences on postnatal brain development. This study describes the association between maternal ALA availability during gestation and lactation, and alterations in the Fads2 DNA methylation in both maternal and offspring livers, at the end of lactation period. Both Fads2 promoter and intron 1 DNA methylation were increased in the groups receiving postnatal flaxseed oil containing 50% ALA (mothers or pups), while bivariate analysis indicated a significant association of the Fads2 epigenetic status in the liver between each mother and its offspring. In addition, Fads2 expression was negatively correlated with promoter methylation at the individual level in maternal livers (P<0.05). This study also indicated that the interplay between ALA availability during gestation and lactation can differentially alter the expression of desaturases and elongases involved in ω-6 and ω-3 metabolic pathways. In summary, when considering the perinatal dietary ALA requirements in mice, both gestation and lactation periods should be considered as having distinct roles in modulating the metabolism of ω-6 and ω-3 fatty acids in maternal mouse livers.
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Affiliation(s)
- Mihai D Niculescu
- University of North Carolina Nutrition Research Institute, Kannapolis, North Carolina 28081, USA.
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255
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Franklin T, Saab B, Mansuy I. Neural Mechanisms of Stress Resilience and Vulnerability. Neuron 2012; 75:747-61. [DOI: 10.1016/j.neuron.2012.08.016] [Citation(s) in RCA: 313] [Impact Index Per Article: 26.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/17/2012] [Indexed: 01/01/2023]
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256
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Hirano K, Kaneko R, Izawa T, Kawaguchi M, Kitsukawa T, Yagi T. Single-neuron diversity generated by Protocadherin-β cluster in mouse central and peripheral nervous systems. Front Mol Neurosci 2012; 5:90. [PMID: 22969705 PMCID: PMC3431597 DOI: 10.3389/fnmol.2012.00090] [Citation(s) in RCA: 66] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2012] [Accepted: 08/14/2012] [Indexed: 11/13/2022] Open
Abstract
The generation of complex neural circuits depends on the correct wiring of neurons with diverse individual characteristics. To understand the complexity of the nervous system, the molecular mechanisms for specifying the identity and diversity of individual neurons must be elucidated. The clustered protocadherins (Pcdh) in mammals consist of approximately 50 Pcdh genes (Pcdh-α, Pcdh-β, and Pcdh-γ) that encode cadherin-family cell surface adhesion proteins. Individual neurons express a random combination of Pcdh-α and Pcdh-γ, whereas the expression patterns for the Pcdh-β genes, 22 one-exon genes in mouse, are not fully understood. Here we show that the Pcdh-β genes are expressed in a 3'-polyadenylated form in mouse brain. In situ hybridization using a pan-Pcdh-β probe against a conserved Pcdh-β sequence showed widespread labeling in the brain, with prominent signals in the olfactory bulb, hippocampus, and cerebellum. In situ hybridization with specific probes for individual Pcdh-β genes showed their expression to be scattered in Purkinje cells from P10 to P150. The scattered expression patterns were confirmed by performing a newly developed single-cell 3'-RACE analysis of Purkinje cells, which clearly demonstrated that the Pcdh-β genes are expressed monoallelically and combinatorially in individual Purkinje cells. Scattered expression patterns of individual Pcdh-β genes were also observed in pyramidal neurons in the hippocampus and cerebral cortex, neurons in the trigeminal and dorsal root ganglion, GABAergic interneurons, and cholinergic neurons. Our results extend previous observations of diversity at the single-neuron level generated by Pcdh expression and suggest that the Pcdh-β cluster genes contribute to specifying the identity and diversity of individual neurons.
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Affiliation(s)
- Keizo Hirano
- KOKORO-Biology Group, Laboratories for Integrated Biology, Graduate School of Frontier Biosciences, Osaka University, 1-3 Yamadaoka, Suita Osaka 565-0871, Japan
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257
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Love OP, McGowan PO, Sheriff MJ. Maternal adversity and ecological stressors in natural populations: the role of stress axis programming in individuals, with implications for populations and communities. Funct Ecol 2012. [DOI: 10.1111/j.1365-2435.2012.02040.x] [Citation(s) in RCA: 152] [Impact Index Per Article: 12.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Affiliation(s)
- Oliver P. Love
- Department of Biological Sciences; University of Windsor; 401 Sunset Avenue; Windsor; Ontario; N9B 3P4; Canada
| | - Patrick O. McGowan
- Department of Biological Sciences; University of Toronto Scarborough; 1265 Military Trail; Toronto; Ontario; M1C 1A4; Canada
| | - Michael J. Sheriff
- Institute of Arctic Biology; University of Alaska Fairbanks; 902 N. Koyukuk Dr; Fairbanks; Alaska; 99775; USA
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258
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Norman JD, Robinson M, Glebe B, Ferguson MM, Danzmann RG. Genomic arrangement of salinity tolerance QTLs in salmonids: a comparative analysis of Atlantic salmon (Salmo salar) with Arctic charr (Salvelinus alpinus) and rainbow trout (Oncorhynchus mykiss). BMC Genomics 2012; 13:420. [PMID: 22916800 PMCID: PMC3480877 DOI: 10.1186/1471-2164-13-420] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2011] [Accepted: 08/16/2012] [Indexed: 11/10/2022] Open
Abstract
Background Quantitative trait locus (QTL) studies show that variation in salinity tolerance in Arctic charr and rainbow trout has a genetic basis, even though both these species have low to moderate salinity tolerance capacities. QTL were observed to localize to homologous linkage group segments within putative chromosomal regions possessing multiple candidate genes. We compared salinity tolerance QTL in rainbow trout and Arctic charr to those detected in a higher salinity tolerant species, Atlantic salmon. The highly derived karyotype of Atlantic salmon allows for the assessment of whether disparity in salinity tolerance in salmonids is associated with differences in genetic architecture. To facilitate these comparisons, we examined the genomic synteny patterns of key candidate genes in the other model teleost fishes that have experienced three whole-genome duplication (3R) events which preceded a fourth (4R) whole genome duplication event common to all salmonid species. Results Nine linkage groups contained chromosome-wide significant QTL (AS-2, -4p, -4q, -5, -9, -12p, -12q, -14q -17q, -22, and −23), while a single genome-wide significant QTL was located on AS-4q. Salmonid genomes shared the greatest marker homology with the genome of three-spined stickleback. All linkage group arms in Atlantic salmon were syntenic with at least one stickleback chromosome, while 18 arms had multiple affinities. Arm fusions in Atlantic salmon were often between multiple regions bearing salinity tolerance QTL. Nine linkage groups in Arctic charr and six linkage group arms in rainbow trout currently have no synteny alignments with stickleback chromosomes, while eight rainbow trout linkage group arms were syntenic with multiple stickleback chromosomes. Rearrangements in the stickleback lineage involving fusions of ancestral arm segments could account for the 21 chromosome pairs observed in the stickleback karyotype. Conclusions Salinity tolerance in salmonids from three genera is to some extent controlled by the same loci. Synteny between QTL in salmonids and candidate genes in stickleback suggests genetic variation at candidate gene loci could affect salinity tolerance in all three salmonids investigated. Candidate genes often occur in pairs on chromosomes, and synteny patterns indicate these pairs are generally conserved in 2R, 3R, and 4R genomes. Synteny maps also suggest that the Atlantic salmon genome contains three larger syntenic combinations of candidate genes that are not evident in any of the other 2R, 3R, or 4R genomes examined. These larger synteny tracts appear to have resulted from ancestral arm fusions that occurred in the Atlantic salmon ancestor. We hypothesize that the superior hypo-osmoregulatory efficiency that is characteristic of Atlantic salmon may be related to these clusters.
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Affiliation(s)
- Joseph D Norman
- Department of Integrative Biology, University of Guelph, Guelph, ON N1G 2W1, Canada.
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259
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Abstract
Although epidemiological data provide evidence that early life experience plays a critical role in human development, the mechanism of how this works remains in question. Recent data from human and animal literature suggest that epigenetic changes, such as DNA methylation, are involved not only in cellular differentiation but also in the modulation of genome function in response to early life experience affecting gene function and the phenotype. Such modulations may serve as a mechanism for life-long genome adaptation. These changes seem to be widely distributed across the genome and to involve central and peripheral systems. Examining the environmental circumstances associated with the onset and reversal of DNA methylation will be critical for understanding risk and resiliency.
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260
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Hoffmann A, Spengler D. The lasting legacy of social stress on the epigenome of the hypothalamic–pituitary–adrenal axis. Epigenomics 2012; 4:431-44. [DOI: 10.2217/epi.12.34] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Social stress is a major factor contributing to early-life adversity that has taken on an epidemic scale. Early social stress leads to long-lasting changes in behavior, cognition, mood and neuroendocrine responses predisposing to or sheltering from stress-related diseases later in life. Epigenetic mechanisms are thought to mediate the effects of early social stress on the epigenome, and can give rise to persistent memories hard coded by DNA methylation. The hypothalamic–pituitary–adrenal axis canalizes early social stress, which leaves its footprints at key regulator sites of this highly plastic system. Thereby, social stress-induced DNA memories mirror the complexity of the stress response and sex differences in brain epigenetics. Timely therapeutic interventions should aim to attenuate early social stress-derived DNA markings and their life-long consequences for mental health.
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Affiliation(s)
- Anke Hoffmann
- Max Planck Institute of Psychiatry, Molecular Neuroendocrinology, Kraepelinstrasse 2–10, D-80804 Munich, Germany
| | - Dietmar Spengler
- Max Planck Institute of Psychiatry, Molecular Neuroendocrinology, Kraepelinstrasse 2–10, D-80804 Munich, Germany
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261
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Relton CL, Davey Smith G. Two-step epigenetic Mendelian randomization: a strategy for establishing the causal role of epigenetic processes in pathways to disease. Int J Epidemiol 2012; 41:161-76. [PMID: 22422451 DOI: 10.1093/ije/dyr233] [Citation(s) in RCA: 327] [Impact Index Per Article: 27.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
The burgeoning interest in the field of epigenetics has precipitated the need to develop approaches to strengthen causal inference when considering the role of epigenetic mediators of environmental exposures on disease risk. Epigenetic markers, like any other molecular biomarker, are vulnerable to confounding and reverse causation. Here, we present a strategy, based on the well-established framework of Mendelian randomization, to interrogate the causal relationships between exposure, DNA methylation and outcome. The two-step approach first uses a genetic proxy for the exposure of interest to assess the causal relationship between exposure and methylation. A second step then utilizes a genetic proxy for DNA methylation to interrogate the causal relationship between DNA methylation and outcome. The rationale, origins, methodology, advantages and limitations of this novel strategy are presented.
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Affiliation(s)
- Caroline L Relton
- Institute of Genetic Medicine, Newcastle University, Newcastle upon Tyne, UK.
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262
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Drury SS, Theall K, Gleason MM, Smyke AT, De Vivo I, Wong JYY, Fox NA, Zeanah CH, Nelson CA. Telomere length and early severe social deprivation: linking early adversity and cellular aging. Mol Psychiatry 2012; 17:719-27. [PMID: 21577215 PMCID: PMC3518061 DOI: 10.1038/mp.2011.53] [Citation(s) in RCA: 244] [Impact Index Per Article: 20.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/19/2011] [Revised: 03/22/2011] [Accepted: 03/28/2011] [Indexed: 12/25/2022]
Abstract
Accelerated telomere length attrition has been associated with psychological stress and early adversity in adults; however, no studies have examined whether telomere length in childhood is associated with early experiences. The Bucharest Early Intervention Project is a unique randomized controlled trial of foster care placement compared with continued care in institutions. As a result of the study design, participants were exposed to a quantified range of time in institutional care, and represented an ideal population in which to examine the association between a specific early adversity, institutional care and telomere length. We examined the association between average relative telomere length, telomere repeat copy number to single gene copy number (T/S) ratio and exposure to institutional care quantified as the percent of time at baseline (mean age 22 months) and at 54 months of age that each child lived in the institution. A significant negative correlation between T/S ratio and percentage of time was observed. Children with greater exposure to institutional care had significantly shorter relative telomere length in middle childhood. Gender modified this main effect. The percentage of time in institutional care at baseline significantly predicted telomere length in females, whereas the percentage of institutional care at 54 months was strongly predictive of telomere length in males. This is the first study to demonstrate an association between telomere length and institutionalization, the first study to find an association between adversity and telomere length in children, and contributes to the growing literature linking telomere length and early adversity.
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Affiliation(s)
- S S Drury
- Department of Psychiatry, Tulane University, New Orleans, LA, USA.
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263
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McGowan PO. Epigenetic clues to the biological embedding of early life adversity. Biol Psychiatry 2012; 72:4-5. [PMID: 22682394 DOI: 10.1016/j.biopsych.2012.04.017] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/23/2012] [Accepted: 04/23/2012] [Indexed: 11/27/2022]
Affiliation(s)
- Patrick O McGowan
- Centre for the Neurobiology of Stress, Department of Biological Sciences, University of Toronto Scarborough, Canada.
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264
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Peripheral SLC6A4 DNA methylation is associated with in vivo measures of human brain serotonin synthesis and childhood physical aggression. PLoS One 2012; 7:e39501. [PMID: 22745770 PMCID: PMC3379993 DOI: 10.1371/journal.pone.0039501] [Citation(s) in RCA: 142] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2011] [Accepted: 05/21/2012] [Indexed: 12/16/2022] Open
Abstract
The main challenge in addressing the role of DNA methylation in human behaviour is the fact that the brain is inaccessible to epigenetic analysis in living humans. Using positron emission tomography (PET) measures of brain serotonin (5-HT) synthesis, we found in a longitudinal sample that adult males with high childhood-limited aggression (C-LHPA) had lower in vivo 5-HT synthesis in the orbitofrontal cortex (OBFC). Here we hypothesized that 5-HT alterations associated with childhood aggression were linked to differential DNA methylation of critical genes in the 5-HT pathway and these changes were also detectable in peripheral white blood cells. Using pyrosequencing, we determined the state of DNA methylation of SLC6A4 promoter in T cells and monocytes isolated from blood of cohort members (N = 25) who underwent a PET scan, and we examined whether methylation status in the blood is associated with in vivo brain 5-HT synthesis. Higher levels of methylation were observed in both T cells and monocytes at specific CpG sites in the C-LHPA group. DNA methylation of SLC6A4 in monocytes appears to be associated more reliably with group membership than T cells. In both cell types the methylation state of these CpGs was associated with lower in vivo measures of brain 5-HT synthesis in the left and right lateral OBFC (N = 20) where lower 5-HT synthesis in C-LHPA group was observed. Furthermore, in vitro methylation of the SLC6A4 promoter in a luciferase reporter construct suppresses its transcriptional activity supporting a functional role of DNA methylation in SLC6A4 promoter regulation. These findings indicate that state of SLC6A4 promoter methylation is altered in peripheral white blood cells of individuals with physical aggression during childhood. This supports the relevance of peripheral DNA methylation for brain function and suggests that peripheral SLC6A4 DNA methylation could be a marker of central 5-HT function.
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265
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Dahmen B, Pütz V, Herpertz-Dahlmann B, Konrad K. Early pathogenic care and the development of ADHD-like symptoms. J Neural Transm (Vienna) 2012; 119:1023-36. [PMID: 22661337 DOI: 10.1007/s00702-012-0809-8] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2012] [Accepted: 04/16/2012] [Indexed: 01/09/2023]
Abstract
Early pathogenic care that is characterised by disregard for the child's basic emotional needs can lead to severe global psychosocial and cognitive dysfunction and deviant developmental trajectories of brain maturation. Reactive attachment disorder (RAD) is a developmental disorder associated with early pathogenic care that is characterised by markedly disturbed ways of relating socially in most contexts. In addition to other severe emotional dysfunctions, children suffering from RAD often display a high number of comorbid attention deficit/hyperactivity disorder (ADHD) symptoms such as inattention, impulsivity and hyperactivity. It is not yet clear whether ADHD-like symptoms in children exposed to pathogenic care represent a true comorbidity of ADHD or similarities in behavioural dysfunction with a different neurodevelopmental pathway in terms of a phenocopy. In this review, we summarise the findings on the neurobiological consequences of early pathogenic care. Pathogenic care is considered a form of care by a primary caretaker involving a lack or a loss of expectable care, e.g., by early separation, frequent change in caregivers, institutionalisation or neglect. The reviewed studies suggest that a primary dysfunction of limbic brain circuits after early pathogenic care might lead to an interference by motivational or emotional cues impinging on prefrontal executive functions resulting in behavioural similarities with ADHD. Thus, the complex phenotype observed after early pathogenic care might be best described by a dimensional approach with behavioural and neurobiological similarities to ADHD coinciding to a certain degree as a function of early experience. Based on this evidence, suggestions for the treatment of ADHD-like symptoms in children after adverse early life experiences are provided.
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Affiliation(s)
- Brigitte Dahmen
- Department of Child and Adolescent Psychiatry, Psychosomatics and Psychotherapy, Medical Faculty, RWTH Aachen University, Neuenhofer Weg 21, 52074 Aachen, Germany.
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266
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Hoffmann A, Spengler D. DNA memories of early social life. Neuroscience 2012; 264:64-75. [PMID: 22575695 DOI: 10.1016/j.neuroscience.2012.04.003] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2011] [Revised: 03/05/2012] [Accepted: 04/05/2012] [Indexed: 12/21/2022]
Abstract
The foundations of brain architecture are established early in life through a continuous series of dynamic interactions in which environmental conditions and personal experiences have a significant impact on how genetic predispositions are expressed. New scientific research shows that early social experiences can actually influence how genes are expressed. Thus, the old-school concepts that genes are "chiseled in stone" or that they alone determine development have been disproven. The discovery of the epigenome provides an explanation, at the molecular level, for why and how early positive and negative social experiences give rise to a biological memory that can have lifelong impacts. Signatures associated with the epigenome can be temporary or permanent, affect multiple organ systems, and increase the risk not only for poor physical and mental health outcomes but also for impairments in future learning capacity and behavior. Here, we focus on recent evidence for a role of epigenetic DNA modifications as a potential mechanism that explains how early social life experiences become embedded in the circuitry of the developing brain and are associated with lifelong consequences.
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Affiliation(s)
- A Hoffmann
- Max Planck Institute of Psychiatry, Molecular Neuroendocrinology, Kraepelinstr. 2-10, D-80804 Munich, Germany.
| | - D Spengler
- Max Planck Institute of Psychiatry, Molecular Neuroendocrinology, Kraepelinstr. 2-10, D-80804 Munich, Germany.
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267
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Abstract
DNA methylation and chromatin modifications regulate gene expression and contribute to changes in brain transcriptomes underlying neurodevelopmental and psychiatric disorders. Clinical genetics and preclinical animal models highlight the crucial importance of the correct establishment of epigenetic marks during sensitive windows of development for normal brain function. On the same side of the coin, some of the concerned factors also appear engaged in the programming of experience-dependent long-term effects on mental health following exposure to relevant early-life events. Delineating the particular role of genetic variations in these players could provide new insights into the molecular basis of vulnerability and resilience and advance tailored therapies.
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268
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Castellano JF, Fletcher BR, Kelley-Bell B, Kim DH, Gallagher M, Rapp PR. Age-related memory impairment is associated with disrupted multivariate epigenetic coordination in the hippocampus. PLoS One 2012; 7:e33249. [PMID: 22438904 PMCID: PMC3305324 DOI: 10.1371/journal.pone.0033249] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2012] [Accepted: 02/12/2012] [Indexed: 11/24/2022] Open
Abstract
Mounting evidence linking epigenetic regulation to memory-related synaptic plasticity raises the possibility that altered chromatin modification dynamics might contribute to age-dependent cognitive decline. Here we show that the coordinated orchestration of both baseline and experience-dependent epigenetic regulation seen in the young adult hippocampus is lost in association with cognitive aging. Using a well-characterized rat model that reliably distinguishes aged individuals with significant memory impairment from others with normal memory, no single epigenetic mark or experience-dependent modification in the hippocampus uniquely predicted differences in the cognitive outcome of aging. The results instead point to a multivariate pattern in which modification-specific, bidirectional chromatin regulation is dependent on recent behavioral experience, chronological age, cognitive status, and hippocampal region. Whereas many epigenetic signatures were coupled with memory capacity among young adults and aged rats with preserved cognitive function, such associations were absent among aged rats with deficits in hippocampal memory. By comparison with the emphasis in current preclinical translational research on promoting chromatin modifications permissive for gene expression, our findings suggest that optimally successful hippocampal aging may hinge instead on enabling coordinated control across the epigenetic landscape.
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Affiliation(s)
- James F. Castellano
- Laboratory of Experimental Gerontology, National Institute on Aging, Baltimore, Maryland, United States of America
- Graduate Program in Neuroscience, Mount Sinai School of Medicine, New York, New York, United States of America
| | - Bonnie R. Fletcher
- Laboratory of Experimental Gerontology, National Institute on Aging, Baltimore, Maryland, United States of America
| | - Bennett Kelley-Bell
- Laboratory of Experimental Gerontology, National Institute on Aging, Baltimore, Maryland, United States of America
| | - David H. Kim
- Laboratory of Experimental Gerontology, National Institute on Aging, Baltimore, Maryland, United States of America
| | - Michela Gallagher
- Department of Psychological and Brain Sciences, Johns Hopkins University, Baltimore, Maryland, United States of America
| | - Peter R. Rapp
- Laboratory of Experimental Gerontology, National Institute on Aging, Baltimore, Maryland, United States of America
- * E-mail:
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269
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Relton CL, Groom A, St. Pourcain B, Sayers AE, Swan DC, Embleton ND, Pearce MS, Ring SM, Northstone K, Tobias JH, Trakalo J, Ness AR, Shaheen SO, Davey Smith G. DNA methylation patterns in cord blood DNA and body size in childhood. PLoS One 2012; 7:e31821. [PMID: 22431966 PMCID: PMC3303769 DOI: 10.1371/journal.pone.0031821] [Citation(s) in RCA: 115] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2011] [Accepted: 01/16/2012] [Indexed: 12/18/2022] Open
Abstract
Background Epigenetic markings acquired in early life may have phenotypic consequences later in development through their role in transcriptional regulation with relevance to the developmental origins of diseases including obesity. The goal of this study was to investigate whether DNA methylation levels at birth are associated with body size later in childhood. Principal Findings A study design involving two birth cohorts was used to conduct transcription profiling followed by DNA methylation analysis in peripheral blood. Gene expression analysis was undertaken in 24 individuals whose biological samples and clinical data were collected at a mean ± standard deviation (SD) age of 12.35 (0.95) years, the upper and lower tertiles of body mass index (BMI) were compared with a mean (SD) BMI difference of 9.86 (2.37) kg/m2. This generated a panel of differentially expressed genes for DNA methylation analysis which was then undertaken in cord blood DNA in 178 individuals with body composition data prospectively collected at a mean (SD) age of 9.83 (0.23) years. Twenty-nine differentially expressed genes (>1.2-fold and p<10−4) were analysed to determine DNA methylation levels at 1–3 sites per gene. Five genes were unmethylated and DNA methylation in the remaining 24 genes was analysed using linear regression with bootstrapping. Methylation in 9 of the 24 (37.5%) genes studied was associated with at least one index of body composition (BMI, fat mass, lean mass, height) at age 9 years, although only one of these associations remained after correction for multiple testing (ALPL with height, pCorrected = 0.017). Conclusions DNA methylation patterns in cord blood show some association with altered gene expression, body size and composition in childhood. The observed relationship is correlative and despite suggestion of a mechanistic epigenetic link between in utero life and later phenotype, further investigation is required to establish causality.
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Affiliation(s)
- Caroline L. Relton
- HNRC, Institute of Genetic Medicine, Newcastle University, Newcastle upon Tyne, United Kingdom
| | - Alexandra Groom
- HNRC, Institute of Genetic Medicine, Newcastle University, Newcastle upon Tyne, United Kingdom
- * E-mail:
| | - Beate St. Pourcain
- MRC Centre for Causal Analyses in Translational Epidemiology, University of Bristol, Bristol, United Kingdom
| | - Adrian E. Sayers
- Musculoskeletal Research Unit, School of Clinical Sciences, University of Bristol, Bristol, United Kingdom
| | - Daniel C. Swan
- Bioinformatic Support Unit, Newcastle University, Newcastle upon Tyne, United Kingdom
| | - Nicholas D. Embleton
- Newcastle Neonatal Service, Royal Victoria Infirmary, Newcastle upon Tyne, United Kingdom
- Institute of Health and Society, Newcastle University, Newcastle upon Tyne, United Kingdom
| | - Mark S. Pearce
- Institute of Health and Society, Newcastle University, Newcastle upon Tyne, United Kingdom
| | - Susan M. Ring
- School of Social and Community Medicine, University of Bristol, Bristol, United Kingdom
| | - Kate Northstone
- MRC Centre for Causal Analyses in Translational Epidemiology, University of Bristol, Bristol, United Kingdom
| | - Jon H. Tobias
- Musculoskeletal Research Unit, School of Clinical Sciences, University of Bristol, Bristol, United Kingdom
| | - Joseph Trakalo
- Wellcome Trust Centre for Human Genetics, University of Oxford, Oxford, United Kingdom
| | - Andy R. Ness
- School of Dental Sciences, University of Bristol, Bristol, United Kingdom
| | - Seif O. Shaheen
- Barts and the London School of Medicine and Dentistry, Queen Mary University of London, London, United Kingdom
| | - George Davey Smith
- MRC Centre for Causal Analyses in Translational Epidemiology, University of Bristol, Bristol, United Kingdom
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270
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Matrisciano F, Tueting P, Maccari S, Nicoletti F, Guidotti A. Pharmacological activation of group-II metabotropic glutamate receptors corrects a schizophrenia-like phenotype induced by prenatal stress in mice. Neuropsychopharmacology 2012; 37:929-38. [PMID: 22089319 PMCID: PMC3280642 DOI: 10.1038/npp.2011.274] [Citation(s) in RCA: 94] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Prenatal exposure to restraint stress causes long-lasting changes in neuroplasticity that likely reflect pathological modifications triggered by early-life stress. We found that the offspring of dams exposed to repeated episodes of restraint stress during pregnancy (here named 'prenatal restraint stress mice' or 'PRS mice') developed a schizophrenia-like phenotype, characterized by a decreased expression of brain-derived neurotrophic factor and glutamic acid decarboxylase 67, an increased expression of type-1 DNA methyl transferase (DNMT1) in the frontal cortex, and a deficit in social interaction, locomotor activity, and prepulse inhibition. PRS mice also showed a marked decrease in metabotropic glutamate 2 (mGlu2) and mGlu3 receptor mRNA and protein levels in the frontal cortex, which was manifested at birth and persisted in adult life. This decrease was associated with an increased binding of DNMT1 to CpG-rich regions of mGlu2 and mGlu3 receptor promoters and an increased binding of MeCP2 to the mGlu2 receptor promoter. Systemic treatment with the selective mGlu2/3 receptor agonist LY379268 (0.5 mg/kg, i.p., twice daily for 5 days), corrected all the biochemical and behavioral abnormalities shown in PRS mice. Our data show for the first time that PRS induces a schizophrenia-like phenotype in mice, and suggest that epigenetic changes in mGlu2 and mGlu3 receptors lie at the core of the pathological programming induced by early-life stress.
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Affiliation(s)
- Francesco Matrisciano
- The Psychiatric Institute, Department of Psychiatry, College of Medicine, The University of Illinois at Chicago, Chicago, IL 60612, USA.
| | - Patricia Tueting
- The Psychiatric Institute, Department of Psychiatry, College of Medicine, The University of Illinois at Chicago, Chicago, IL, USA
| | - Stefania Maccari
- Neuroplasticity Team – CNRS UMR 8576/UGSF, North University of Lille1, Lille, France
| | - Ferdinando Nicoletti
- Department of Physiology and Pharmacology, University of Rome ‘Sapienza', Rome, Italy,INM Neuromed, Pozzilli, Italy
| | - Alessandro Guidotti
- The Psychiatric Institute, Department of Psychiatry, College of Medicine, The University of Illinois at Chicago, Chicago, IL, USA
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271
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Understanding behavioral effects of early life stress using the reactive scope and allostatic load models. Dev Psychopathol 2012; 23:1001-16. [PMID: 22018078 DOI: 10.1017/s0954579411000460] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
The mechanisms through which early life stress leads to psychopathology are thought to involve allostatic load, the "wear and tear" an organism is subjected to as a consequence of sustained elevated levels of glucocorticoids caused by repeated/prolonged stress activations. The allostatic load model described this phenomenon, but has been criticized as inadequate to explain alterations associated with early adverse experience in some systems, including behavior, which cannot be entirely explained from an energy balance perspective. The reactive scope model has been more recently proposed and focuses less on energy balance and more on dynamic ranges of physiological and behavioral mediators. In this review we examine the mechanisms underlying the behavioral consequences of early life stress in the context of both these models. We focus on adverse experiences that involve mother-infant relationship disruption, and dissect those mechanisms involving maternal care as a regulator of development of neural circuits that control emotional and social behaviors in the offspring. We also discuss the evolutionary purpose of the plasticity in behavioral development, which has a clear adaptive value in a changing environment.
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272
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273
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274
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Turecki G, Ernst C, Jollant F, Labonté B, Mechawar N. The neurodevelopmental origins of suicidal behavior. Trends Neurosci 2011; 35:14-23. [PMID: 22177979 DOI: 10.1016/j.tins.2011.11.008] [Citation(s) in RCA: 183] [Impact Index Per Article: 14.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2011] [Revised: 10/28/2011] [Accepted: 11/21/2011] [Indexed: 12/30/2022]
Abstract
Suicide and related behaviors are complex phenomena associated with different risk factors. Although most individuals who display suicidal behavior do not have a history of early-life adversity, a significant minority does. Recent animal and human data have suggested that early-life adversity leads to epigenetic regulation of genes involved in stress-response systems. Here, we review this evidence and suggest that early-life adversity increases risk of suicide in susceptible individuals by influencing the development of stable emotional, behavioral and cognitive phenotypes that are likely to result from the epigenetic regulation of the hypothalamic-pituitary-adrenal axis and other systems involved in responses to stress.
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Affiliation(s)
- Gustavo Turecki
- McGill Group for Suicide Studies, Department of Psychiatry, McGill University, Montreal, Canada.
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275
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Increased methylation of glucocorticoid receptor gene (NR3C1) in adults with a history of childhood maltreatment: a link with the severity and type of trauma. Transl Psychiatry 2011; 1:e59. [PMID: 22832351 PMCID: PMC3309499 DOI: 10.1038/tp.2011.60] [Citation(s) in RCA: 376] [Impact Index Per Article: 28.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Childhood maltreatment, through epigenetic modification of the glucocorticoid receptor gene (NR3C1), influences the hypothalamic-pituitary-adrenal axis (HPA axis). We investigated whether childhood maltreatment and its severity were associated with increased methylation of the exon 1(F) NR3C1 promoter, in 101 borderline personality disorder (BPD) and 99 major depressive disorder (MDD) subjects with, respectively, a high and low rate of childhood maltreatment, and 15 MDD subjects with comorbid post-traumatic stress disorder (PTSD). Childhood sexual abuse, its severity and the number of type of maltreatments positively correlated with NR3C1 methylation (P=6.16 × 10(-8), 5.18 × 10(-7) and 1.25 × 10(-9), respectively). In BPD, repetition of abuses and sexual abuse with penetration correlated with a higher methylation percentage. Peripheral blood might therefore serve as a proxy for environmental effects on epigenetic processes. These findings suggest that early life events may permanently impact on the HPA axis though epigenetic modifications of the NR3C1. This is a mechanism by which childhood maltreatment may lead to adulthood psychopathology.
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276
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Heim C, Binder EB. Current research trends in early life stress and depression: review of human studies on sensitive periods, gene-environment interactions, and epigenetics. Exp Neurol 2011; 233:102-11. [PMID: 22101006 DOI: 10.1016/j.expneurol.2011.10.032] [Citation(s) in RCA: 626] [Impact Index Per Article: 48.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2011] [Revised: 10/17/2011] [Accepted: 10/30/2011] [Indexed: 12/16/2022]
Abstract
Early life stress, such as childhood abuse, neglect and loss, is a well established major risk factor for developing depressive disorders later in life. We here summarize and discuss current developments in human research regarding the link between early life stress and depression. Specifically, we review the evidence for the existence of sensitive periods for the adverse effects of early life stress in humans. We further review the current state of knowledge regarding gene×environment (G×E) interactions in the effects of early life stress. While multiple genes operate in multiple environments to induce risk for depression after early life stress, these same genes also seem to enhance the beneficial effects of a positive early environment. Also, we discuss the epigenetic mechanisms that might underlie these G×E interactions. Finally, we discuss the potential importance of identifying sensitive time periods of opportunity, as well as G×E interactions and epigenetic mechanisms, for early interventions that might prevent or reverse the detrimental outcomes of early life stress and its transmission across generations.
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Affiliation(s)
- Christine Heim
- Institute of Medical Psychology, Charité University Medicine Berlin, Berlin, Germany.
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277
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Afonso VM, King SJ, Novakov M, Burton CL, Fleming AS. Accumbal dopamine function in postpartum rats that were raised without their mothers. Horm Behav 2011; 60:632-43. [PMID: 21964046 DOI: 10.1016/j.yhbeh.2011.08.016] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/09/2011] [Revised: 08/20/2011] [Accepted: 08/24/2011] [Indexed: 11/21/2022]
Abstract
Postpartum rats that had been previously raised in an artificial rearing (AR) apparatus, without their mothers or siblings during the preweaning period, show altered maternal responses towards their own offspring in adulthood. In mother-reared (MR) rats, nucleus accumbens (NAC) dopamine (DA) responses to pups evoke a robust sustained rise during the postpartum period and following treatment with estrogen/progesterone parturient-like hormones (Afonso et al., 2009). These MR females had siblings that received AR rearing with varying amounts of preweaning tactile stimulation (ARmin; ARmax). The present study examined NACshell DA responses to pup and food stimuli in these AR rats, and statistically compared them to their MR siblings. Microdialysis samples were collected from adult (90 days postnatal) AR females in different parity states (cycling vs. postpartum, Exp. 1), or after ovariectomy with different hormone treatments (sham vs. hormone, Exp. 2. After basal sample collection, pup and then food stimuli were individually presented to the females in the dialysis chamber. As with their MR siblings, basal DA concentrations were lower and pup-evoked DA responses greater in hormonally-primed AR females than in non-primed AR controls. Compared to their postpartum MR sisters (Exp. 1), AR rats had increased basal DA levels, reduced pup related DA elevations, and disrupted maternal behavior. The postpartum AR impairment in pup-evoked DA was reversed by additional pre-weaning tactile stimulation. Exogenous hormones (Exp. 2) eliminated AR impairments on pup-evoked DA responses. Although MR and AR siblings had comparable DA responses to food stimuli, upon reanalyzing MR data it was found that only postpartum dams had DA responses to pups greater than to food. These data suggest that that the hormonally induced suppression of basal DA levels may reflect saliency of pups which was greater in MR than in AR dams. Preweaning tactile stimulation could partially reverse these effects only in naturally cycling or parturient animals.
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Affiliation(s)
- Veronica M Afonso
- Department of Psychology, University of Toronto at Mississauga, 3359 Mississauga Rd N, Mississauga, ON, Canada L5L 1C6.
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278
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Borghol N, Suderman M, McArdle W, Racine A, Hallett M, Pembrey M, Hertzman C, Power C, Szyf M. Associations with early-life socio-economic position in adult DNA methylation. Int J Epidemiol 2011; 41:62-74. [PMID: 22422449 DOI: 10.1093/ije/dyr147] [Citation(s) in RCA: 336] [Impact Index Per Article: 25.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
BACKGROUND Disadvantaged socio-economic position (SEP) in childhood is associated with increased adult mortality and morbidity. We aimed to establish whether childhood SEP was associated with differential methylation of adult DNA. METHODS Forty adult males from the 1958 British Birth Cohort Study were selected from SEP extremes in both early childhood and mid-adulthood. We performed genome-wide methylation analysis on blood DNA taken at 45 years using MeDIP (methylated DNA immunoprecipitation). We mapped in triplicate the methylation state of promoters of approximately 20,000 genes and 400 microRNAs. Probe methylation scores were averaged across triplicates and differential methylation between groups of individuals was determined. Differentially methylated promoter sites of selected genes were validated using pyrosequencing of bisulfite-converted DNA. RESULTS Variably methylated probes (9112 from n = 223,359 on the microarray) corresponded to 6176 gene promoters with at least one variable probe. Unsupervised hierarchical clustering of probes obtained from the 500 most variable promoters revealed a cluster enriched with high SEP individuals confirming that SEP differences contribute to overall epigenetic variation. Methylation levels for 1252 gene promoters were associated with childhood SEP vs 545 promoters for adulthood SEP. Functionally, associations with childhood SEP appear in promoters of genes enriched in key cell signalling pathways. The differentially methylated promoters associated with SEP cluster in megabase-sized regions of the genome. CONCLUSIONS Adult blood DNA methylation profiles show more associations with childhood SEP than adult SEP. Organization of these associations across the genome suggests a well-defined epigenetic pattern linked to early socio-economic environment.
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Affiliation(s)
- Nada Borghol
- Sackler Program for Epigenetics & Developmental Psychobiology, McGill University, Montreal, Quebec, Canada
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279
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Rymer T, Pillay N. Transmission of parental care behavior in African striped mice, Rhabdomys Pumilio. ACTA ACUST UNITED AC 2011; 315:631-8. [DOI: 10.1002/jez.712] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2011] [Revised: 08/16/2011] [Accepted: 08/29/2011] [Indexed: 12/27/2022]
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280
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Szyf M. The early life social environment and DNA methylation: DNA methylation mediating the long-term impact of social environments early in life. Epigenetics 2011; 6:971-8. [PMID: 21772123 DOI: 10.4161/epi.6.8.16793] [Citation(s) in RCA: 127] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
Although epidemiological data provides evidence that there is an interaction between genetics (nature) and the social and physical environments (nurture) in human development; the main open question remains the mechanism. The pattern of distribution of methyl groups in DNA is different from cell-type to cell type and is conferring cell specific identity on DNA during cellular differentiation and organogenesis. This is an innate and highly programmed process. However, recent data suggests that DNA methylation is not only involved in cellular differentiation but that it is also involved in modulation of genome function in response to signals from the physical, biological and social environments. We propose that modulation of DNA methylation in response to environmental cues early in life serves as a mechanism of life-long genome "adaptation" that molecularly embeds the early experiences of a child ("nurture") in the genome ("nature"). There is an emerging line of data supporting this hypothesis in rodents, non-human primates and humans that will be reviewed here. However, several critical questions remain including the identification of mechanisms that transmit the signals from the social environment to the DNA methylation/demethylation enzymes.
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Affiliation(s)
- Moshe Szyf
- Department of Pharmacology and Therapeutics, McGill University Montreal CA, USA.
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281
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Faulk C, Dolinoy DC. Timing is everything: the when and how of environmentally induced changes in the epigenome of animals. Epigenetics 2011; 6:791-7. [PMID: 21636976 DOI: 10.4161/epi.6.7.16209] [Citation(s) in RCA: 211] [Impact Index Per Article: 16.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Abstract
Environmental influence on developmental plasticity impacts a wide diversity of animal life from insects to humans. We now understand the epigenetic basis for many of these altered phenotypes. The five environmental factors of nutrition, behavior, stress, toxins, and stochasticity work individually and in concert to affect the developing epigenome. During early embryogenesis, epigenetic marks, such as DNA methylation, are reset at specific times. Two waves of global demethylation and reestablishment of methylation frame the sensitive times for early environmental influences and will be the focus of this review. Gene transcription, translation, and post-translational modification of chromatin remodeling complexes are three mechanisms affected by developmental exposure to environmental factors. To illustrate how changes in the early environment profoundly affect these mechanisms, we provide examples throughout the animal kingdom. Herein we review the history, time points, and mechanisms of epigenetic gene-environment interaction.
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Affiliation(s)
- Christopher Faulk
- Department of Environmental Health Sciences, University of Michigan, Ann Arbor, MI, USA
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282
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Iraola-Guzmán S, Estivill X, Rabionet R. DNA methylation in neurodegenerative disorders: a missing link between genome and environment? Clin Genet 2011; 80:1-14. [PMID: 21542837 DOI: 10.1111/j.1399-0004.2011.01673.x] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
The risk of developing neurodegenerative disorders such as Alzheimer's disease or Parkinson's disease is influenced by genetic and environmental factors. Environmental events occurring during development or later in life can be related to disease susceptibility. One way by which the environment may exert its effect is through epigenetic modifications, which might affect the functioning of genes. These include nucleosome positioning, post-translational histone modifications, and DNA methylation. In this review we will focus in the potential role of DNA methylation in neurodegenerative disorders and in the approaches to explore such epigenetic changes. Advances in deciphering the role of epigenetic modifications in phenotype are being uncovered for a variety of diseases, including cancer, autoimmune, neurodevelopmental and cognitive disorders. Epigenetic modifications are now being also associated with cardiovascular and metabolic traits, and they are expected to be especially involved in learning and memory processes, as well as in neurodegenerative disease. The study of the role of methylation and other epigenetic modifications in disease development will provide new insights in the etiopathogenesis of neurodegenerative disorders, and should hopefully shape new avenues in the development of therapeutic strategies.
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Affiliation(s)
- S Iraola-Guzmán
- Center for Genomic Regulation and UPF, Dr Aiguader 88, 08003 Barcelona, Spain
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283
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Szyf M. DNA methylation, the early-life social environment and behavioral disorders. J Neurodev Disord 2011; 3:238-49. [PMID: 21484196 PMCID: PMC3261271 DOI: 10.1007/s11689-011-9079-2] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/21/2010] [Accepted: 02/14/2011] [Indexed: 01/12/2023] Open
Abstract
One of the outstanding questions in behavioral disorders is untangling the complex relationship between nurture and nature. Although epidemiological data provide evidence that there is an interaction between genetics (nature) and the social and physical environments (nurture) in a spectrum of behavioral disorders, the main open question remains the mechanism. Emerging data support the hypothesis that DNA methylation, a covalent modification of the DNA molecule that is a component of its chemical structure, serves as an interface between the dynamic environment and the fixed genome. We propose that modulation of DNA methylation in response to environmental cues early in life serves as a mechanism of life-long genome adaptation. Under certain contexts, this adaptation can turn maladaptive resulting in behavioral disorders. This hypothesis has important implications on understanding, predicting, preventing, and treating behavioral disorders including autism that will be discussed.
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Affiliation(s)
- Moshe Szyf
- Department of Pharmacology and Therapeutics, McGill University, Montreal, QC, H3G 1Y6, Canada,
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284
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Szyf M. The implications of DNA methylation for toxicology: toward toxicomethylomics, the toxicology of DNA methylation. Toxicol Sci 2011; 120:235-55. [PMID: 21297083 DOI: 10.1093/toxsci/kfr024] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Identifying agents that have long-term deleterious impact on health but exhibit no immediate toxicity is of prime importance. It is well established that long-term toxicity of chemicals could be caused by their ability to generate changes in the DNA sequence through the process of mutagenesis. Several assays including the Ames test and its different modifications were developed to assess the mutagenic potential of chemicals (Ames, B. N., Durston, W. E., Yamasaki, E., and Lee, F. D. (1973a). Carcinogens are mutagens: a simple test system combining liver homogenates for activation and bacteria for detection. Proc. Natl. Acad. Sci. U.S.A. 70, 2281-2285; Ames, B. N., Lee, F. D., and Durston, W. E. (1973b). An improved bacterial test system for the detection and classification of mutagens and carcinogens. Proc. Natl. Acad. Sci. U.S.A. 70, 782-786). These tests have also been employed for assessing the carcinogenic potential of compounds. However, the DNA molecule contains within its chemical structure two layers of information. The DNA sequence that bears the ancestral genetic information and the pattern of distribution of covalently bound methyl groups on cytosines in DNA. DNA methylation patterns are generated by an innate program during gestation but are attuned to the environment in utero and throughout life including physical and social exposures. DNA function and health could be stably altered by exposure to environmental agents without changing the sequence, just by changing the state of DNA methylation. Our current screening tests do not detect agents that have long-range impact on the phenotype without altering the genotype. The realization that long-range damage could be caused without changing the DNA sequence has important implications on the way we assess the safety of chemicals, drugs, and food and broadens the scope of definition of toxic agents.
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Affiliation(s)
- Moshe Szyf
- Department of Pharmacology and Therapeutics, McGill University, McGill University, Montreal, Quebec H3G 1Y6, Canada.
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285
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Meijer OC. Corticosteroid receptor signalling modes and stress adaptation in the brain. Horm Mol Biol Clin Investig 2011; 7:317-26. [PMID: 25961270 DOI: 10.1515/hmbci.2011.114] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2011] [Accepted: 07/11/2011] [Indexed: 11/15/2022]
Abstract
Adrenal glucocorticoid hormones modulate neuronal activity to support an adaptive response to stress. They modulate brain circuitry mediating physiological responses, emotion and cognitive processing. Chronically elevated glucocorticoid exposure is however linked to the development of mental disease. Glucocorticoid effects depend on mineralo- and glucocorticoid receptors, which are powerful transcription factors, but also can act via a diversity of non-genomic mechanisms. Here, I review generic factors that determine neuronal glucocorticoid sensitivity, in relation to brain function. First, pre-receptor mechanisms determine ligand availability. Second, there may be considerable variation in the receptor splice- and translation variants. Third, other transcription factors and many transcriptional coregulators interact with steroid receptors, determining nature and magnitude of steroid responses, in part through epigenetic regulation of DNA accessibility. Which factors underlie adaptive and pathogenic effects of stress hormones is largely unknown. Genome-wide identification of the receptor-DNA interactions in specific behavioural and physiological contexts provides a way of assessing the complete genomic range of glucocorticoid modes of action. Novel ligands that induce selective activation of particular receptor signalling modes will aid our understanding of receptor signalling and may allow selective targeting of glucocorticoid effects in emotional or cognitive domains, in research and, hopefully, in clinical settings.
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