Table of Contents

Volume 6, Issue 7

  July 2011

  Pages 789 - 952

Special Focus Issue: Environmental Epigenetics

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EDITOR'S PREVIEW

Open Access Article

In this issue of Epigenetics: Special issue on environmental epigenetics

Barbara P. Rattner
Pages 789 - 790
http://dx.doi.org/10.4161/epi.6.7.16674
PDF




REVIEWS

Open Access Article

Timing is everything: The when and how of environmentally induced changes in the epigenome of animals

Christopher Faulk and Dana C. Dolinoy
Pages 791 - 797
http://dx.doi.org/10.4161/epi.6.7.16209
Abstract | PDF

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.

Biological memories of past environments: Epigenetic pathways to health disparities

Zaneta M. Thayer and Christopher W. Kuzawa
Pages 798 - 803
http://dx.doi.org/10.4161/epi.6.7.16222
Abstract | PDF

Human health tends to mirror gradients in social standing related to class, ethnicity and race. Past research in the social sciences suggests that environmental experiences related to social status contribute to these disparities, but the underlying biological mechanisms are only partially understood. Here, we review research related to three domains of environmental exposure that point to epigenetic contributions to health disparities: nutrition, psychosocial stress, and environmental toxicant exposure. Each exposure has effects that may persist across the life course and in some instances may be transmitted to offspring via epigenetic inheritance. Since epigenetic markings provide a "memory" of past experiences, minimizing future disparities in health will be partially contingent upon our ability to address inequality in the current environment. We suggest that future research in environmental epigenetics focus on establishing the reversibility of stress-induced epigenetic modifications, and also on identifying positive epigenetic effects of environmental enrichment.

Epigenetic mechanisms and cancer: An interface between the environment and the genome

Zdenko Herceg and Thomas Vaissière
Pages 804 - 819
http://dx.doi.org/10.4161/epi.6.7.16262
Abstract | PDF

Although epidemiological studies support the role of environment in a wide range of human cancers, the precise mechanisms by which environmental exposures promote cancer development and progression remain poorly understood. Environmental factors have been proposed to promote the development of malignancies by eliciting epigenetic changes; however, it is only with recent advances in epigenetics and epigenomics that target genes and the mechanisms underlying environmental influences are beginning to be elucidated. Because epigenetic mechanisms may function as an interface between environmental factors and the genome, deregulation of the epigenome by environmental stressors is likely to disrupt different cellular processes and contribute to cancer risk. In addition, the early appearance and ubiquity of epigenetic changes in virtually all steps of tumor development and progression in most, if not all, human neoplasms, make them attractive targets for biomarker discovery and targeted prevention. At the cellular level, aberrant epigenetic changes associated with environmental exposures may deregulate key cellular processes (including transcriptional control, DNA repair, cell cycle control, and carcinogen detoxification), which can be further modulated by environmental stressors, thus defining not only the phenotype of the disease but also potential biomarkers. This review summarizes recent progress in our understanding of the epigenetic mechanisms through which environmental factors may promote tumor development, with a particular focus on human lung cancer.

Environmental epigenetics in metal exposure

Ricardo Martinez-Zamudio and Hyo Chol Ha
Pages 820 - 827
http://dx.doi.org/10.4161/epi.6.7.16250
Abstract | PDF

Although it is widely accepted that chronic exposure to arsenite, nickel, chromium and cadmium increases cancer incidence in individuals, the molecular mechanisms underlying their ability to transform cells remain largely unknown. Carcinogenic metals are typically weak mutagens, suggesting that genetic-based mechanisms may not be primarily responsible for metal-induced carcinogenesis. Growing evidence shows that environmental metal exposure involves changes in epigenetic marks, which may lead to a possible link between heritable changes in gene expression and disease susceptibility and development. Here, we review recent advances in the understanding of metal exposure affecting epigenetic marks and discuss establishment of heritable gene expression in metal-induced carcinogenesis.

Open Access Article

DNA methylation in white blood cells: Association with risk factors in epidemiologic studies

Mary Beth Terry, Lissette Delgado-Cruzata, Neomi Vin-Raviv, Hui Chen Wu and Regina M. Santella
Pages 828 - 837
http://dx.doi.org/10.4161/epi.6.7.16500
Abstract | PDF

Alterations in DNA methylation patterns, both at specific loci and overall in the genome, have been associated with many different health outcomes. In cancer and other diseases, most of these changes have been observed at the tissue level. Data on whether DNA methylation changes in white blood cells (WBC) can serve as a useful biomarker for different health outcomes are much more limited, but rapidly emerging. Epidemiologic studies have reported associations between global WBC methylation and several different cancers including cancers of the colon, bladder, stomach, breast and head and neck, as well as schizophrenia and myelodysplastic syndrome. Evidence for WBC methylation at specific loci and disease risk is more limited, but increasing. Differences in WBC DNA methylation by selected risk factors including demographic (age, gender, race), environmental exposures (benzene, persistent organic pollutants, lead, arsenic, and air pollution), and other risk factors (cigarette smoke, alcohol drinking, body size, physical activity and diet) have been observed in epidemiologic studies though the patterns are far from consistent. Challenges in inferences from the existing data are primarily due to the cross-sectional and small size of most studies to date as well as the differences in results across assay type and source of DNA. Large, prospective studies will be needed to understand whether changes in risk factors are associated with changes in DNA methylation patterns, and if changes in DNA methylation patterns are associated with changes in disease endpoints.




POINTS-OF-VIEW

Open Access Article

Environmental epigenetic transgenerational inheritance and somatic epigenetic mitotic stability

Michael K. Skinner
Pages 838 - 842
http://dx.doi.org/10.4161/epi.6.7.16537
Abstract | PDF

The majority of environmental factors can not modify DNA sequence, but can influence the epigenome. The mitotic stability of the epigenome and ability of environmental epigenetics to influence phenotypic variation and disease, suggests environmental epigenetics will have a critical role in disease etiology and biological areas such as evolutionary biology. The current review presents the molecular basis of how environment can promote stable epigenomes and modified phenotypes, and distinguishes the difference between epigenetic transgenerational inheritance through the germ line versus somatic cell mitotic stability.

Epigenetics in disease: Leader or follower?

David I.K. Martin, Jennifer E. Cropley and Catherine M. Suter
Pages 843 - 848
http://dx.doi.org/10.4161/epi.6.7.16498
Abstract | PDF

Epigenetic silencing is a pervasive mode of gene regulation in multicellular eukaryotes: stable differentiation of somatic cell types requires the maintenance of subsets of genes in an active or silent state. The variety of molecules involved, and the requirement for active maintenance of epigenetic states, creates the potential for errors on a large scale. When epigenetic errors - or epimutations - activate or inactivate a critical gene, they may cause disease. An epimutation that occurs in the germline or early embryo can affect all, or most, of the soma and phenocopy genetic disease. But the stochastic and reversible nature of epigenetic phenomena predicts that epimutations are likely to be mosaic and inherited in a nonmendelian manner; epigenetic diseases will thus rarely behave in the comfortably predictable manner of genetic diseases but will display variable expressivity and complex patterns of inheritance. Much phenotypic variation and common disease might be explained by epigenetic variation and aberration. The known examples of true epigenetic disease are at present limited, but this may reflect only the difficulty in distinguishing causal epigenetic aberrations from those that are merely consequences of disease, a challenge further extended by the impact of environmental agents on epigenetic mechanisms. The rapidly developing molecular characterization of epigenomes, and the new ability to survey epigenetic marks on whole genomes, may answer many questions about the causal role of epigenetics in disease; these answers have the potential to transform our understanding of human disease.

Epigenetic modifications of metastasis suppressor genes in colon cancer metastasis

Qian Li and Hong Chen
Pages 849 - 852
http://dx.doi.org/10.4161/epi.6.7.16314
Abstract | PDF

Colon and rectal cancer (colorectal cancer, CRC) is the third most common cancer worldwide. Deaths from CRC account for around 8% of all cancer deaths, making it the fourth most common cause of death from cancer. The high mortality rate of colon cancer is mainly attributable to its metastasis. Efforts have been made to identify metastasis suppressor genes, which encode proteins responsible for inhibiting the metastasis but not suppressing the growth of primary tumors. Studies on metastasis suppressor genes demonstrated that epigenetic modifications, such as DNA promoter methylation and histone modification, play crucial roles in regulating the expression of many metastasis suppressor genes, which indicates the association between aberrant epigenetic alterations and cancer metastasis. This review will focus on the recent findings regarding metastasis suppressors regulated by epigenetic modifications, particularly DNA methylation and histone modification, in CRC metastasis. Also discussed will be recent progress on the suppression of CRC metastasis by genistein, a soy isoflavone, with a focus on epigenetic mechanisms.

Hypothesis: Environmental regulation of 5-hydroxymethylcytosine by oxidative stress

Nancy Chia, Luan Wang, Xiangyi Lu, Mary-Claude Senut, Carol A. Brenner and Douglas M. Ruden
Pages 853 - 856
http://dx.doi.org/10.4161/epi.6.7.16461
Abstract | PDF

Many environmental toxins, such as heavy metals, air particles, and ozone, induce oxidative stress and decrease the levels of NADH and NADPH, cofactors that drive anabolic biochemical reactions and provide reducing capacity to combat oxidative stress. Recently, it was found that the Ten-eleven translocation (TET) protein family members, which oxidize 5-methylcytosine (5mC) to 5-hydroxymethylcytosine (5hmC) in the DNA, is activated under high oxygen conditions by alpha ketoglutarate (-KG), a cofactor produced by aerobic metabolism in the citric acid cycle. TET, Jumonji-family histone demethylases, and prolyl hydroxylase, a repressor of HIF1a under high oxygen conditions, all require alpha ketoglutarate (a-KG) as cofactors for their activation. The impact of the HIF1a and TET proteins, which appear to have opposing functions, reaches several aspects of human life-including cell growth regulation, embryonic stem cell maintenance, cell differentiation, and tumorigenesis. The role of metabolism on regulating global DNA methylation and chromatin organization is recently demanding greater attention from the biomedical research community. This article will discuss the possible role of TET activation and the regulation of 5hmC and 5mC levels in response to environmental stress. We will also discuss how 5hmC and 5mC levels at the promoters of specific genes might be a useful biomarker for exposure to environmental toxins.

Open Access Article

Sex differences in epigenetic mechanisms may underlie risk and resilience for mental health disorders

Heather M. Jessen and Anthony P. Auger
Pages 857 - 861
http://dx.doi.org/10.4161/epi.6.7.16517
Abstract | PDF

Alterations in the epigenetic programming of sex differences in the brain may underlie sexually dimorphic neurodevelopmental disorders. Sex differences have been found in DNA methyltransferases 3a, DNA methylation patterns, MeCP2, and nuclear corepressor within the developing brain. Natural variations in these epigenetic mechanisms have profound consequences on gene expression and brain function. Exogenous or endogenous perturbations during development may impact these epigenetic processes and alter the trajectory of the developing brain and confer sexually dimorphic risk and resilience for developing a neurological or mental health disorder.

A genomic point-of-view on environmental factors influencing the human brain methylome

Janine M. LaSalle
Pages 862 - 869
http://dx.doi.org/10.4161/epi.6.7.16353
Abstract | PDF

The etiologic paradigm of complex human disorders such as autism is that genetic and environmental risk factors are independent and additive, but the interactive effects at the epigenetic interface are largely ignored. Genomic technologies have radically changed perspective on the human genome and how the epigenetic interface may impact complex human disorders. Here, I review recent genomic, environmental, and epigenetic findings that suggest a new paradigm of “integrative genomics” in which genetic variation in genomic size may be impacted by dietary and environmental factors that influence the genomic saturation of DNA methylation. Human genomes are highly repetitive, but the interface of large-scale genomic differences with environmental factors that alter the DNA methylome such as dietary folate is under-explored. In addition to obvious direct effects of some environmental toxins on the genome by causing chromosomal breaks, non-mutagenic toxin exposures correlate with DNA hypomethylation that can lead to rearrangements between repeats or increased retrotransposition. Since human neurodevelopment appears to be particularly sensitive to alterations in epigenetic pathways, a further focus will be on how developing neurons may be particularly impacted by even subtle alterations to DNA methylation and proposing new directions towards understanding the quixotic etiology of autism by integrative genomic approaches.

The effects of the dietary polyphenol resveratrol on human healthy aging and lifespan

Agustín F. Fernández and Mario F. Fraga
Pages 870 - 874
http://dx.doi.org/10.4161/epi.6.7.16499
Abstract | PDF

The physiological effects of the dietary polyphenol resveratrol are being extensively studied. Resveratrol has been proposed to promote healthy aging and to increase lifespan primarily through the activation of the class III histone deacetylases (sirtuins). Although its positive effects are evident in yeast and mice they still have to be confirmed in humans. The molecular mechanisms involved in the processes are not fully understood because resveratrol may have other targets than sirtuins and the direct activation of sirtuins by resveratrol is under debate.

The emerging role of epigenetic mechanisms in the etiology of neural tube defects

Nicholas D.E. Greene, Philip Stanier and Gudrun E. Moore
Pages 875 - 883
http://dx.doi.org/10.4161/epi.6.7.16400
Abstract | PDF

The molecular requirements for neural tube closure are complex. This is illustrated by the occurrence of neural tube defects (NTDs) in many genetic mouse mutants, which implicate a variety of genes, pathways and cellular functions. NTDs are also prevalent birth defects in humans, affecting around 1 per 1000 pregnancies worldwide. In humans the causation is thought to involve the interplay of fetal genes and the effect of environmental factors. Recent studies on the aetiology of human NTDs, as well as analysis of mouse models, have raised the question of the possible involvement of epigenetic factors in determining susceptibility. A consideration of potential causative factors in human NTDs must now include both alterations in the regulation of gene expression, through mutation of promoter or regulatory elements, and the additional analysis of epigenetic regulation. Alterations in the epigenetic status can be directly modified by various environmental insults or maternal dietary factors.

Remodeling is at the heart of chromatin

Assam El-Osta
Pages 884 - 887
http://dx.doi.org/10.4161/epi.6.7.16551
Abstract | PDF

Chromatin modifications are integral elements of chromosome structure and its function and the vasculature depends on tissue-specific genome regulation for its development. A general concept for the de-regulation of chromatin modifications in cardiac and vascular disease is also emerging. The recognition that metabolic memory contributes to disease persistence highlights the benefit of early and aggressive treatment. As for the importance of memory, we do know that good metabolic control delays the onset of long-term diabetic complications. There are striking parallels between the timing of disease and the development of complications. Landmark multicenter clinical trials on diabetes patients have popularized the concept that glucose is also a demonstrable determinant for the development of complications, indicating the prolonged benefit of intensive therapy and the lasting damage of conventional therapy. Each cell type experiences thousands of modifications to the epigenome in response to environmental changes it is exposed to. Therefore, history is neither lost nor forgotten and previous experiences and exposure may form future memories. There is now a strong resurgence in research trying to understand gene-environment interactions and to determine what commits specific vascular cell types to specific memories. Recent insights show that cardiac gene expression is distinguished by specific chromatin remodeling events and histone modifications that are associated with heart disease.

Genistein, an epigenome modifier during cancer prevention

Yukun Zhang and Hong Chen
Pages 888 - 891
http://dx.doi.org/10.4161/epi.6.7.16315
Abstract | PDF

Dietary compounds have been observed to have a great potential to regulate the epigenome, which is disrupted and reprogrammed during carcinogenesis. Because of their close association with cancer development, DNA methylation patterns have been used as a crucial marker for the study of cancer-related epigenetics. There is immense evidence indicating that dietary components play a critical role in cancer development. Genistein, one of the soy-derived bioactive isoflavones, affects tumorigenesis through epigenetic regulations. By modulating chromatin configuration and DNA methylation, genistein activates tumor suppressor genes and affects cancer cell survival. Here, we summarize and discuss both in vitro and in vivo studies in the field that investigate the effect of genistein on histone modifications and DNA methylation. The promising role of genistein in cancer prevention and therapeutic applications will be discussed from an epigenetic point of view.

The role of holocarboxylase synthetase in genome stability is mediated partly by epigenomic synergies between methylation and biotinylation events

Janos Zempleni, Yong Li, Jing Xue and Elizabeth L. Cordonier
Pages 892 - 894
http://dx.doi.org/10.4161/epi.6.7.15544
Abstract | PDF

Holocarboxylase synthetase (HLCS) catalyzes the covalent binding of biotin to histones. Biotinylated histones are gene repression marks and are particularly enriched in long terminal repeats, telomeres, and other repeat regions. The effects of HLCS in gene regulation are mediated by its physical interactions with chromatin proteins such as histone H3, DNMT1, MeCP2, and EHMT-1. It appears that histone biotinylation depends on prior methylation of cytosines. De-repression of long terminal repeats in biotin- or HLCS-deficient cell cultures and organisms is associated with genome instability.




BRIEF REPORT

Heritability and role for the environment in DNA methylation in AXL receptor tyrosine kinase

Carrie V. Breton, Muhammad T. Salam and Frank D. Gilliland
Pages 895 - 898
http://dx.doi.org/10.4161/epi.6.7.15768
Abstract | PDF

DNA methylation in AXL, a receptor tyrosine kinase relevant in cancer and immune function, is reportedly highly heritable. We present evidence to suggest that heritability of DNA methylation in AXL is variable, dependent on population characteristics and cell type studied. Moreover, environmental exposures in utero, particularly exposure to maternal smoking, contributes to variation in DNA methylation of select CpG loci that can affect calculations of heritability. Children exposed to maternal smoking in utero had a 2.3% increase (95 % CI 0.3, 4.2) in DNA methylation in AXL, which was magnified in girls as compared to boys. These results present compelling evidence that environmental exposure to tobacco smoke during pregnancy may alter DNA methylation levels in subtle but potentially important ways, and that these changes are persistent years after birth.




RESEARCH PAPERS

Maternal dietary protein affects transcriptional regulation of myostatin gene distinctively at weaning and finishing stages in skeletal muscle of Meishan pigs

Xiujuan Liu, Jinquan Wang, Runsheng Li, Xiaojing Yang, Qinwei Sun, Elke Albrecht and Ruqian Zhao
Pages 899 - 907
http://dx.doi.org/10.4161/epi.6.7.16005
Abstract | PDF

Myostatin (MSTN) is suggested to mediate the effect of maternal nutrition on offspring phenotype, yet the mechanisms underlying such adaptive gene regulation is elusive. In this study, we determined the effects of maternal dietary protein on transcriptional regulation of MSTN in skeletal muscle of pig offspring. Fourteen Meishan sows were fed either low-protein (LP) or standard-protein (SP) diets throughout gestation and lactation. MSTN expression in the longissimus dorsi muscle was determined both at weaning and finishing stages. Myostatin mRNA abundance was downregulated at weaning, but upregulated at finishing in LP pigs, indicating stage-specific transcriptional regulation. At weaning, CCAAT/enhancer-binding protein beta (C/EBPβ) in muscle nuclear lysate was decreased in LP piglets, associated with diminished binding of C/EBPβ to all the 3 putative binding sites in MSTN promoter. None of the four histone modification marks investigated showed differences between SP and LP piglets. Among 12 microRNAs predicted to target MSTN, none was differently expressed. At finishing stage, C/EBPβ content remained unchanged, but the binding of C/EBPβ to two of the 3 putative binding sites increased in LP pigs. Histone H3 acetylation and histone H3 lysine 27 trimethylation on MSTN promoter were increased, while histone H3 lysine 9 monomethylation was decreased in LP pigs. Moreover, expression of ssc-miR-136 and ssc-miR-500 was significantly reduced. These results indicate that maternal dietary protein affects MSTN expression through distinct regulatory mechanisms at different stages. The immediate effect at weaning is mediated by C/EBPβ binding without epigenetic modifications, whereas the long-term effect at finishing stage involves both C/EBPβ binding and epigenetic regulations, including histone modification and microRNA expression.

The influence of aging, environmental exposures and local sequence features on the variation of DNA methylation in blood

Scott M. Langevin, E. Andres Houseman, Brock C. Christensen, John K. Wiencke, Heather H. Nelson, Margaret R. Karagas, Carmen J. Marsit and Karl T. Kelsey
Pages 908 - 919
http://dx.doi.org/10.4161/epi.6.7.16431
Abstract | PDF

In order to properly comprehend the epigenetic dysregulation that occurs during the course of disease, there is a need to characterize the epigenetic variability in healthy individuals that arises in response to aging and exposures, and to understand such variation within the biological context of the DNA sequence. We analyzed the methylation of 26,486 autosomal CpG loci in blood from 205 healthy subjects, using three complementary approaches to assess the association between methylation, age or exposures, and local sequence features, such as CpG island status, repeat sequences, location within a polycomb target gene or proximity to a transcription factor binding site. We clustered CpGs (1) using unsupervised recursively partitioned mixture modeling (RPMM) and (2) bioinformatically-informed methods, and (3) also employed a marginal model-based (non-clustering) approach. We observed associations between age and methylation and hair dye use and methylation, where the direction and magnitude was contingent on the local sequence features of the CpGs. Our results demonstrate that CpGs are differentially methylated dependent upon the genomic features of the sequence in which they are embedded, and that CpG methylation is associated with age and hair dye use in a CpG context-dependent manner in healthy individuals.

Infant growth restriction is associated with distinct patterns of DNA methylation in human placentas

Carolyn E. Banister, Devin C. Koestler, Matthew A. Maccani, James F. Padbury, E. Andres Houseman and Carmen J. Marsit
Pages 920 - 927
http://dx.doi.org/10.4161/epi.6.7.16079
Abstract | PDF

The placenta acts not only as a conduit of nutrient and waste exchange between mother and developing fetus, but also functions as a regulator of the intrauterine environment. Recent work has identified changes in the expression of candidate genes, often through epigenetic alteration, which alter the placenta's function and impact fetal growth. In this study, we used the Illumina Infinium HumanMethylation27 BeadChip array to examine genome-wide DNA methylation patterns in 206 term human placentas. Semi-supervised recursively partitioned mixture modeling was implemented to identify specific patterns of placental DNA methylation that could differentially classify intrauterine growth restriction (IUGR) and small for gestational age (SGA) placentas from appropriate for gestational age (AGA) placentas, and these associations were validated in a masked testing series of samples. Our work demonstrates that patterns of DNA methylation in human placenta are reliably and significantly associated with infant growth and serve as a proof of principle that methylation status in the human term placenta can function as a marker for the intrauterine environment, and could potentially play a critical functional role in fetal development.

Open Access Article

Methylation variation at IGF2 differentially methylated regions and maternal folic acid use before and during pregnancy

Cathrine Hoyo, Amy P. Murtha, Joellen M. Schildkraut, Randy L. Jirtle, Wendy Demark-Wahnefried, Michele R. Forman, Edwin S. Iversen, Joanne Kurtzberg, Francine Overcash, Zhiqing Huang and Susan K. Murphy
Pages 928 - 936
http://dx.doi.org/10.4161/epi.6.7.16263
Abstract | PDF

Folic acid (FA) supplementation before and during pregnancy has been associated with decreased risk of neural tube defects although recent reports suggest it may also increase the risk of other chronic diseases. We evaluated exposure to maternal FA supplementation before and during pregnancy in relation to aberrant DNA methylation at two differentially methylated regions (DMRs) regulating Insulin-like Growth Factor 2 (IGF2) expression in infants. Aberrant methylation at these regions has been associated with IGF2 deregulation and increased susceptibility to several chronic diseases. Using a self-administered questionnaire, we assessed FA intake before and during pregnancy in 438 pregnant women. Pyrosequencing was used to measure methylation at two IGF2 DMRs in umbilical cord blood leukocytes. Mixed models were used to determine relationships between maternal FA supplementation before or during pregnancy and DNA methylation levels at birth. Average methylation at the H19 DMR was 61.2%. Compared to infants born to women reporting no FA intake before or during pregnancy, methylation levels at the H19 DMR decreased with increasing FA intake (2.8%, p=0.03, and 4.9%, p=0.04, for intake before and during pregnancy, respectively). This methylation decrease was most pronounced in male infants (p=0.01). Methylation alterations at the H19 DMR are likely an important mechanism by which FA risks and/or benefits are conferred in utero. Because stable methylation marks at DMRs regulating imprinted genes are acquired before gastrulation, they may serve as archives of early exposures with the potential to improve our understanding of developmental origins of adult disease.

Open Access Article

Effects of endocrine disruptors on imprinted gene expression in the mouse embryo

Eun-Rim Kang, Khursheed Iqbal, Diana A. Tran, Guillermo E. Rivas, Purnima Singh, Gerd P. Pfeifer and Piroska E. Szabó
Pages 937 - 950
http://dx.doi.org/10.4161/epi.6.7.16067
Abstract | PDF

Environmental endocrine disruptors (EDs) are synthetic chemicals that resemble natural hormones and are known to cause epigenetic perturbations. EDs have profound effects on development and fertility. Imprinted genes had been identified as susceptible loci to environmental insults by EDs because they are functionally haploid, and because the imprints undergo epigenetic resetting between generations. To screen for possible epigenetic perturbations caused by EDs at imprinted loci, we treated pregnant mice daily between 8.5 and 12.5 days post coitum (dpc) with di-(2-ethylhexyl)-phthalate (DEHP), bisphenol A (BPA), vinclozolin (VZ), or control oil vehicle. After isolating RNA from the placenta, yolk sac, amnion, head, body, heart, liver, lung, stomach, and intestines of 13.5 dpc embryos we measured the allele-specific expression of 38 imprinted transcripts using multiplex single nucleotide primer extension (SNuPE) assays. In this representative data set we identified only a small number of transcripts that exhibited a substantial relaxation of imprinted expression with statistical significance: Slc22a18 with 10% relaxation in the embryo after BPA treatment; Rtl1as with 11 and 16% relaxation in the lung and placenta, respectively after BPA treatment; and Rtl1 with 12% relaxation in the yolk sac after DEHP treatment. Additionally, the standard deviation of allele-specificity increased in various organs after ED treatment for several transcripts including Igf2r, Rasgrf1, Usp29, Slc38a4, and Xist. Our data suggest that the maintenance of strongly biased monoallelic expression of imprinted genes is generally insensitive to EDs in the 13.5 dpc embryo and extra-embryonic organs, but is not immune to those effects.




ERRATA

Open Access Article

Erratum to: An S/MAR-based L1 retrotransposition cassette mediates sustained levels of insertional mutagenesis without suffering from epigenetic silencing of DNA methylation

Danny Rangasamy
Page 951
http://dx.doi.org/10.4161/epi.6.7.16675
Abstract | PDF

This is an erratum to:
An S/MAR-based L1 retrotransposition cassette mediates sustained levels of insertional mutagenesis without suffering from epigenetic silencing of DNA methylation
DOI: 10.4161/epi.5.7.12647
Danny Rangasamy
Volume 5, Issue 7
Pages 601 - 611

Open Access Article

Erratum to: Ubiquitin-dependent distribution of the transcriptional coactivator p300 in cytoplasmic Inclusion bodies

Jihong Chen, Sabina Halappanavar, John Th’ng and Qiao Li
Page 952
http://dx.doi.org/10.4161/epi.6.7.16676
Abstract | PDF

This is an erratum to: Ubiquitin-dependent distribution of the transcriptional coactivator p300 in cytoplasmic Inclusion bodies
DOI: 10.4161/epi.2.2.4326
Jihong Chen, Sabina Halappanavar, John Th’ng and Qiao Li
Volume 2, Issue 2
Pages 92 - 99