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El Hajj N, Schneider E, Lehnen H, Haaf T. Epigenetics and life-long consequences of an adverse nutritional and diabetic intrauterine environment. Reproduction 2014; 148:R111-20. [PMID: 25187623 PMCID: PMC4241689 DOI: 10.1530/rep-14-0334] [Citation(s) in RCA: 128] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
The phenomenon that adverse environmental exposures in early life are associated with increased susceptibilities for many adult, particularly metabolic diseases, is now referred to as ‘developmental origins of health and disease (DOHAD)’ or ‘Barker’ hypothesis. Fetal overnutrition and undernutrition have similar long-lasting effects on the setting of the neuroendocrine control systems, energy homeostasis, and metabolism, leading to life-long increased morbidity. There are sensitive time windows during early development, where environmental cues can program persistent epigenetic modifications which are generally assumed to mediate these gene–environment interactions. Most of our current knowledge on fetal programing comes from animal models and epidemiological studies in humans, in particular the Dutch famine birth cohort. In industrialized countries, there is more concern about adverse long-term consequences of fetal overnutrition, i.e. by exposure to gestational diabetes mellitus and/or maternal obesity which affect 10–20% of pregnancies. Epigenetic changes due to maternal diabetes/obesity may predispose the offspring to develop metabolic disease later in life and, thus, transmit the adverse environmental exposure to the next generation. This vicious cycle could contribute significantly to the worldwide metabolic disease epidemics. In this review article, we focus on the epigenetics of an adverse intrauterine environment, in particular gestational diabetes, and its implications for the prevention of complex disease.
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Affiliation(s)
- Nady El Hajj
- Institute of Human GeneticsJulius-Maximilians-Universität Würzburg, Biozentrum, Am Hubland, 97074 Würzburg, GermanyDepartment of Gynecology and ObstetricsStädtische Kliniken, 41239 Mönchengladbach, Germany
| | - Eberhard Schneider
- Institute of Human GeneticsJulius-Maximilians-Universität Würzburg, Biozentrum, Am Hubland, 97074 Würzburg, GermanyDepartment of Gynecology and ObstetricsStädtische Kliniken, 41239 Mönchengladbach, Germany
| | - Harald Lehnen
- Institute of Human GeneticsJulius-Maximilians-Universität Würzburg, Biozentrum, Am Hubland, 97074 Würzburg, GermanyDepartment of Gynecology and ObstetricsStädtische Kliniken, 41239 Mönchengladbach, Germany
| | - Thomas Haaf
- Institute of Human GeneticsJulius-Maximilians-Universität Würzburg, Biozentrum, Am Hubland, 97074 Würzburg, GermanyDepartment of Gynecology and ObstetricsStädtische Kliniken, 41239 Mönchengladbach, Germany
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102
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Pezic D, Manakov SA, Sachidanandam R, Aravin AA. piRNA pathway targets active LINE1 elements to establish the repressive H3K9me3 mark in germ cells. Genes Dev 2014; 28:1410-28. [PMID: 24939875 PMCID: PMC4083086 DOI: 10.1101/gad.240895.114] [Citation(s) in RCA: 154] [Impact Index Per Article: 15.4] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Transposable elements (TEs) occupy a large fraction of metazoan genomes and pose constant threats to genomic integrity. Small noncoding piwi-interacting RNAs (piRNAs) recognize and silence a diverse set of TEs in germ cells. Pezic et al. show the piRNA pathway is required to maintain a high level of the repressive H3K9me3 histone modification on long interspersed nuclear elements (LINEs) in mammalian germ cells. The analyses reveal that the piRNA pathway targets full-length elements of actively transposing LINE families but not the copious small fragments present throughout the genome. Transposable elements (TEs) occupy a large fraction of metazoan genomes and pose a constant threat to genomic integrity. This threat is particularly critical in germ cells, as changes in the genome that are induced by TEs will be transmitted to the next generation. Small noncoding piwi-interacting RNAs (piRNAs) recognize and silence a diverse set of TEs in germ cells. In mice, piRNA-guided transposon repression correlates with establishment of CpG DNA methylation on their sequences, yet the mechanism and the spectrum of genomic targets of piRNA silencing are unknown. Here we show that in addition to DNA methylation, the piRNA pathway is required to maintain a high level of the repressive H3K9me3 histone modification on long interspersed nuclear elements (LINEs) in germ cells. piRNA-dependent chromatin repression targets exclusively full-length elements of actively transposing LINE families, demonstrating the remarkable ability of the piRNA pathway to recognize active elements among the large number of genomic transposon fragments.
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Affiliation(s)
- Dubravka Pezic
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, California 91125, USA
| | - Sergei A Manakov
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, California 91125, USA
| | - Ravi Sachidanandam
- Genetics and Genomic Sciences, Mount Sinai School of Medicine, New York, New York 10029, USA
| | - Alexei A Aravin
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, California 91125, USA
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103
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Mak KS, Burdach J, Norton LJ, Pearson RCM, Crossley M, Funnell APW. Repression of chimeric transcripts emanating from endogenous retrotransposons by a sequence-specific transcription factor. Genome Biol 2014; 15:R58. [PMID: 24946810 PMCID: PMC4056533 DOI: 10.1186/gb-2014-15-4-r58] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2013] [Accepted: 04/30/2014] [Indexed: 11/10/2022] Open
Abstract
Background Retroviral elements are pervasively transcribed and dynamically regulated during development. While multiple histone- and DNA-modifying enzymes have broadly been associated with their global silencing, little is known about how the many diverse retroviral families are each selectively recognized. Results Here we show that the zinc finger protein Krüppel-like Factor 3 (KLF3) specifically silences transcription from the ORR1A0 long terminal repeat in murine fetal and adult erythroid cells. In the absence of KLF3, we detect widespread transcription from ORR1A0 elements driven by the master erythroid regulator KLF1. In several instances these aberrant transcripts are spliced to downstream genic exons. One such chimeric transcript produces a novel, dominant negative isoform of PU.1 that can induce erythroid differentiation. Conclusions We propose that KLF3 ensures the integrity of the murine erythroid transcriptome through the selective repression of a particular retroelement and is likely one of multiple sequence-specific factors that cooperate to achieve global silencing.
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104
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Abstract
The etiology of many brain diseases remains allusive to date after intensive investigation of genomic background and symptomatology from the day of birth. Emerging evidences indicate that a third factor, epigenetics prior to the birth, can exert profound influence on the development and functioning of the brain and over many neurodevelopmental syndromes. This chapter reviews how aversive environmental exposure to parents might predispose or increase vulnerability of offspring to neurodevelopmental deficit through alteration of epigenetics. These epigenetic altering environmental factors will be discussed in the category of addictive agents, nutrition or diet, prescriptive medicine, environmental pollutant, and stress. Epigenetic alterations induced by these aversive environmental factors cover all aspects of epigenetics including DNA methylation, histone modification, noncoding RNA, and chromatin modification. Next, the mechanisms how these environmental inputs influence epigenetics will be discussed. Finally, how environmentally altered epigenetic marks affect neurodevelopment is exemplified by the alcohol-induced fetal alcohol syndrome. It is hoped that a thorough understanding of the nature of prenatal epigenetic inputs will enable researchers with a clear vision to better unravel neurodevelopmental deficit, late-onset neuropsychiatric diseases, or idiosyncratic mental disorders.
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Affiliation(s)
- Chiao-Ling Lo
- Department of Anatomy and Cell Biology, Stark Neuroscience Research Institute, Indiana Alcohol Research Center, Indiana University School of Medicine, and Department of Psychology, Indiana University Purdue University at Indianapolis, Indianapolis, Indiana, USA
| | - Feng C Zhou
- Department of Anatomy and Cell Biology, Stark Neuroscience Research Institute, Indiana Alcohol Research Center, Indiana University School of Medicine, and Department of Psychology, Indiana University Purdue University at Indianapolis, Indianapolis, Indiana, USA.
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105
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Age-specific locomotor response to nicotine in yellow and mottled yellow A(vy)/a mice. BMC Res Notes 2013; 6:497. [PMID: 24289264 PMCID: PMC4222098 DOI: 10.1186/1756-0500-6-497] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2013] [Accepted: 11/23/2013] [Indexed: 11/25/2022] Open
Abstract
Background Most Agouti viable yellow (Avy) mice display constitutive expression of agouti protein, which acts as an inverse agonist at the melanocortin receptor 4 (Mc4r), resulting in adult-onset obesity as well as an altered sensitivity to some drugs of abuse. We investigated the influence of excessive agouti expression on open-field locomotor response to daily 0.5 mg/kg (-)-freebase nicotine injections in 27 early adolescent and 27 young adult male Avy/a and a/a mice, and assessed the effects of nicotine administration (0.5 mg/kg) followed by open-field testing on serum corticosterone levels in a separate group of 25 young adult male Avy/a and a/a mice. Findings Young adult Avy/a mice displayed pronounced nicotine-induced hypolocomotion (a 24% reduction in distance traveled) compared to their a/a littermates. Early adolescent Avy/a mice did not differ from their a/a littermates or saline-matched controls in locomotion following nicotine administration. Young adult Avy/a mice also displayed increased thigmotaxis (a 5% increase in time spent outside the center of the apparatus) on the first day of nicotine administration as compared to saline-matched controls, while a/a mice did not. An increase in serum corticosterone levels 20 minutes after nicotine injection in a separate group of young adult male mice (n = 25) was proportionally similar between Avy/a and a/a mice. Conclusions Overall, the results suggest an age- and epigenotype- or genotype-specific response to nicotine administration in young adult male Avy/a mice. It appears the Avy/a locomotor and thigmotaxic responses to acute nicotine administration are not mediated solely by hypothalamic-pituitary-adrenal (HPA) axis stimulation.
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106
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Abstract
Much of what we know about the role of epigenetics in the determination of phenotype has come from studies of inbred mice. Some unusual expression patterns arising from endogenous and transgenic murine alleles, such as the Agouti coat color alleles, have allowed the study of variegation, variable expressivity, transgenerational epigenetic inheritance, parent-of-origin effects, and position effects. These phenomena have taught us much about gene silencing and the probabilistic nature of epigenetic processes. Based on some of these alleles, large-scale mutagenesis screens have broadened our knowledge of epigenetic control by identifying and characterizing novel genes involved in these processes.
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Affiliation(s)
- Marnie Blewitt
- Walter and Eliza Hall Institute, Melbourne, 3052 Victoria, Australia
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107
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Baker MS, Li G, Kohorst JJ, Waterland RA. Fetal growth restriction promotes physical inactivity and obesity in female mice. Int J Obes (Lond) 2013; 39:98-104. [PMID: 23924758 PMCID: PMC3872504 DOI: 10.1038/ijo.2013.146] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/20/2013] [Revised: 07/10/2013] [Accepted: 07/20/2013] [Indexed: 01/11/2023]
Abstract
BACKGROUND Environmental exposures during critical periods of prenatal and early postnatal life affect the development of mammalian body weight regulatory mechanisms, influencing lifelong risk of obesity. The specific biological processes that mediate the persistence of such effects, however, remain poorly understood. OBJECTIVE The objectives of this study were to determine the developmental timing and physiological basis of the obesity-promoting effect previously reported in offspring of obese agouti viable yellow (A(vy)/a) mothers. DESIGN Newborn offspring of obese A(vy)/a and lean (a/a) mothers were cross-fostered shortly after birth to study separately the effects of in utero or suckling period exposure to A(vy)/a dams. Body composition, food intake, physical activity and energy expenditure were measured in offspring shortly after weaning and in adulthood. RESULTS Offspring of obese A(vy)/a dams paradoxically experienced fetal growth restriction, which was followed by adult-onset obesity specifically in females. Our main analyses focused on wild-type (a/a) offspring, because a subset of adult A(vy)/a offspring contracted a kidney disease resembling diabetic nephropathy. Detailed physiological characterization demonstrated that, both shortly after weaning and in adulthood, female wild-type mice born to A(vy)/a mothers are not hyperphagic but have reduced physical activity and energy expenditure. No such coordinated changes were detected in male offspring. Mediational regression analysis of our longitudinal data supported a causal pathway in which fetal growth restriction persistently reduces physical activity, leading to adult obesity. CONCLUSIONS Our data are consistent with several recent human epidemiological studies showing female-specific effects of perinatal nutritional restriction on later obesity, and provide the novel mechanistic insight that this may occur via permanent and sex-specific changes in one's inherent propensity for physical activity.
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Affiliation(s)
- M S Baker
- Department of Pediatrics, Baylor College of Medicine, USDA/ARS Children's Nutrition Research Center, Houston, TX, USA
| | - G Li
- Department of Pediatrics, Baylor College of Medicine, USDA/ARS Children's Nutrition Research Center, Houston, TX, USA
| | - J J Kohorst
- Department of Pediatrics, Baylor College of Medicine, USDA/ARS Children's Nutrition Research Center, Houston, TX, USA
| | - R A Waterland
- 1] Department of Pediatrics, Baylor College of Medicine, USDA/ARS Children's Nutrition Research Center, Houston, TX, USA [2] Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX, USA
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108
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Herceg Z, Lambert MP, van Veldhoven K, Demetriou C, Vineis P, Smith MT, Straif K, Wild CP. Towards incorporating epigenetic mechanisms into carcinogen identification and evaluation. Carcinogenesis 2013; 34:1955-67. [PMID: 23749751 DOI: 10.1093/carcin/bgt212] [Citation(s) in RCA: 69] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Remarkable progress in the field of epigenetics has turned academic, medical and public attention to the potential applications of these new advances in medicine and various fields of biomedical research. The result is a broader appreciation of epigenetic phenomena in the a etiology of common human diseases, most notably cancer. These advances also represent an exciting opportunity to incorporate epigenetics and epigenomics into carcinogen identification and safety assessment. Current epigenetic studies, including major international sequencing projects, are expected to generate information for establishing the 'normal' epigenome of tissues and cell types as well as the physiological variability of the epigenome against which carcinogen exposure can be assessed. Recently, epigenetic events have emerged as key mechanisms in cancer development, and while our search of the Monograph Volume 100 revealed that epigenetics have played a modest role in evaluating human carcinogens by the International Agency for Research on Cancer (IARC) Monographs so far, epigenetic data might play a pivotal role in the future. Here, we review (i) the current status of incorporation of epigenetics in carcinogen evaluation in the IARC Monographs Programme, (ii) potential modes of action for epigenetic carcinogens, (iii) current in vivo and in vitro technologies to detect epigenetic carcinogens, (iv) genomic regions and epigenetic modifications and their biological consequences and (v) critical technological and biological issues in assessment of epigenetic carcinogens. We also discuss the issues related to opportunities and challenges in the application of epigenetic testing in carcinogen identification and evaluation. Although the application of epigenetic assays in carcinogen evaluation is still in its infancy, important data are being generated and valuable scientific resources are being established that should catalyse future applications of epigenetic testing.
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Affiliation(s)
- Zdenko Herceg
- International Agency for Research on Cancer (IARC), 150 Cours Albert Thomas, F-69008 Lyon, France
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109
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Chandramohan B, Renieri C, La Manna V, La Terza A. The alpaca agouti gene: Genomic locus, transcripts and causative mutations of eumelanic and pheomelanic coat color. Gene 2013; 521:303-10. [DOI: 10.1016/j.gene.2013.03.060] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2011] [Revised: 02/01/2013] [Accepted: 03/16/2013] [Indexed: 12/01/2022]
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110
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Suto JI, Satou K. Genetic background (DDD/Sgn versus C57BL/6J) strongly influences postnatal growth of male mice carrying the A(y) allele at the agouti locus: identification of quantitative trait loci associated with diabetes and body weight loss. BMC Genet 2013; 14:35. [PMID: 23641944 PMCID: PMC3669036 DOI: 10.1186/1471-2156-14-35] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2012] [Accepted: 04/23/2013] [Indexed: 11/28/2022] Open
Abstract
Background Mice carrying the Ay allele at the agouti locus become obese and are heavier than their non-Ay littermates. However, this does not hold true for the genetic background of the DDD mouse strain. At 22 weeks of age, DDD.Cg-Ay females are heavier than DDD females, whereas DDD.Cg-Ay males are lighter than DDD males. This study aimed to determine the possible cause and identify the genes responsible for the lower body weight of DDD.Cg-Ay males. Results Growth curves of DDD.Cg-Ay mice were analyzed and compared with those of B6.Cg-Ay mice from 5 to 25 weeks. In DDD.Cg-Ay males, body weight gain stopped between 16 and 17 weeks and the body weight gradually decreased; thus, the lower body weight was a consequence of body weight loss. Quantitative trait locus (QTL) mapping was performed in backcrossed (BC) males of DDD × (B6 × DDD.Cg-Ay) F1-Ay mice. For the body weight at 25 weeks, significant QTLs were identified on chromosomes 1 and 4. The DDD allele was associated with a lower body weight at both loci. In particular, the QTL on chromosome 4 interacted with the Ay allele. Furthermore, suggestive QTLs for plasma glucose and high molecular weight adiponectin levels were coincidentally mapped to chromosome 4. The DDD allele was associated with increased glucose and decreased adiponectin levels. When the body weight at 25 weeks and plasma glucose levels were considered as dependent and independent variables, respectively, BC Ay males were classified into two groups according to statistical analysis using the partition method. Mice of one group had significantly higher glucose and lower adiponectin levels than those of the other group and exhibited body weight loss as observed with DDD-Ay males. Conclusions The lower body weight of DDD.Cg-Ay male mice was a consequence of body weight loss. Diabetes mellitus has been suggested to be a possible contributory factor causing body weight loss. The QTL on distal chromosome 4 contained the major responsible genes. This QTL interacted with the Ay allele, implying the reason why body weight loss occurs in DDD.Cg-Ay but not in DDD males.
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Affiliation(s)
- Jun-ichi Suto
- Agrogenomics Research Center, National Institute of Agrobiological Sciences, Tsukuba, Ibaraki 305-8634, Japan.
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111
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Huidobro C, Fernandez AF, Fraga MF. The role of genetics in the establishment and maintenance of the epigenome. Cell Mol Life Sci 2013; 70:1543-73. [PMID: 23474979 PMCID: PMC11113764 DOI: 10.1007/s00018-013-1296-2] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2013] [Revised: 02/05/2013] [Accepted: 02/05/2013] [Indexed: 12/19/2022]
Abstract
Epigenetic mechanisms play an important role in gene regulation during development. DNA methylation, which is probably the most important and best-studied epigenetic mechanism, can be abnormally regulated in common pathologies, but the origin of altered DNA methylation remains unknown. Recent research suggests that these epigenetic alterations could depend, at least in part, on genetic mutations or polymorphisms in DNA methyltransferases and certain genes encoding enzymes of the one-carbon metabolism pathway. Indeed, the de novo methyltransferase 3B (DNMT3B) has been recently found to be mutated in several types of cancer and in the immunodeficiency, centromeric region instability and facial anomalies syndrome (ICF), in which these mutations could be related to the loss of global DNA methylation. In addition, mutations in glycine-N-methyltransferase (GNMT) could be associated with a higher risk of hepatocellular carcinoma and liver disease due to an unbalanced S-adenosylmethionine (SAM)/S-adenosylhomocysteine (SAH) ratio, which leads to aberrant methylation reactions. Also, genetic variants of chromatin remodeling proteins and histone tail modifiers are involved in genetic disorders like α thalassemia X-linked mental retardation syndrome, CHARGE syndrome, Cockayne syndrome, Rett syndrome, systemic lupus erythematous, Rubinstein-Taybi syndrome, Coffin-Lowry syndrome, Sotos syndrome, and facioescapulohumeral syndrome, among others. Here, we review the potential genetic alterations with a possible role on epigenetic factors and discuss their contribution to human disease.
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Affiliation(s)
- Covadonga Huidobro
- Cancer Epigenetics Laboratory, Institute of Oncology of Asturias (IUOPA-HUCA), University of Oviedo, Oviedo, Spain
| | - Agustin F. Fernandez
- Cancer Epigenetics Laboratory, Institute of Oncology of Asturias (IUOPA-HUCA), University of Oviedo, Oviedo, Spain
| | - Mario F. Fraga
- Cancer Epigenetics Laboratory, Institute of Oncology of Asturias (IUOPA-HUCA), University of Oviedo, Oviedo, Spain
- Department of Immunology and Oncology, Centro Nacional de Biotecnología (CNB-CSIC), Madrid, Spain
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112
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Li CCY, Young PE, Maloney CA, Eaton SA, Cowley MJ, Buckland ME, Preiss T, Henstridge DC, Cooney GJ, Febbraio MA, Martin DIK, Cropley JE, Suter CM. Maternal obesity and diabetes induces latent metabolic defects and widespread epigenetic changes in isogenic mice. Epigenetics 2013; 8:602-11. [PMID: 23764993 PMCID: PMC3857340 DOI: 10.4161/epi.24656] [Citation(s) in RCA: 67] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Intrauterine nutrition can program metabolism, creating stable changes in physiology that may have significant health consequences. The mechanism underlying these changes is widely assumed to involve epigenetic changes to the expression of metabolic genes, but evidence supporting this idea is limited. Here we have performed the first study of the epigenomic consequences of exposure to maternal obesity and diabetes. We used a mouse model of natural-onset obesity that allows comparison of genetically identical mice whose mothers were either obese and diabetic or lean with a normal metabolism. We find that the offspring of obese mothers have a latent metabolic phenotype that is unmasked by exposure to a Western-style diet, resulting in glucose intolerance, insulin resistance and hepatic steatosis. The offspring show changes in hepatic gene expression and widespread but subtle alterations in cytosine methylation. Contrary to expectation, these molecular changes do not point to metabolic pathways but instead reside in broadly developmental ontologies. We propose that, rather than being adaptive, these changes may simply produce an inappropriate response to suboptimal environments; maladaptive phenotypes may be avoidable if postnatal nutrition is carefully controlled.
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Affiliation(s)
- Cheryl C Y Li
- Molecular Genetics Division; Victor Chang Cardiac Research Institute; Darlinghurst, NSW Australia
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113
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Rowe HM, Friedli M, Offner S, Verp S, Mesnard D, Marquis J, Aktas T, Trono D. De novo DNA methylation of endogenous retroviruses is shaped by KRAB-ZFPs/KAP1 and ESET. Development 2013; 140:519-29. [PMID: 23293284 DOI: 10.1242/dev.087585] [Citation(s) in RCA: 128] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Endogenous retroviruses (ERVs) undergo de novo DNA methylation during the first few days of mammalian embryogenesis, although the factors that control the targeting of this process are largely unknown. We asked whether KAP1 (KRAB-associated protein 1) is involved in this mechanism because of its previously defined role in maintaining the silencing of ERVs through the histone methyltransferase ESET and histone H3 lysine 9 trimethylation. Here, we demonstrate that introduced ERV sequences are sufficient to direct rapid de novo methylation of a flanked promoter in embryonic stem (ES) cells. This mechanism requires the presence of an ERV sequence-recognizing KRAB zinc-finger protein (ZFP) and both KAP1 and ESET. Furthermore, this process can also take place on a strong cellular promoter and leads to methylation signatures that are subsequently maintained in vivo throughout embryogenesis. Finally, we show that methylation of ERVs residing in the genome is affected by knockout of KAP1 in early embryos. KRAB-ZFPs, KAP1 and ESET are thus likely to be responsible for the early embryonic instatement of stable epigenetic marks at ERV-containing loci.
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Affiliation(s)
- Helen M Rowe
- School of Life Sciences and Frontiers in Genetics Program, Ecole Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland
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114
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Rowe HM, Kapopoulou A, Corsinotti A, Fasching L, Macfarlan TS, Tarabay Y, Viville S, Jakobsson J, Pfaff SL, Trono D. TRIM28 repression of retrotransposon-based enhancers is necessary to preserve transcriptional dynamics in embryonic stem cells. Genome Res 2013; 23:452-61. [PMID: 23233547 PMCID: PMC3589534 DOI: 10.1101/gr.147678.112] [Citation(s) in RCA: 110] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2012] [Accepted: 12/06/2012] [Indexed: 02/03/2023]
Abstract
TRIM28 is critical for the silencing of endogenous retroviruses (ERVs) in embryonic stem (ES) cells. Here, we reveal that an essential impact of this process is the protection of cellular gene expression in early embryos from perturbation by cis-acting activators contained within these retroelements. In TRIM28-depleted ES cells, repressive chromatin marks at ERVs are replaced by histone modifications typical of active enhancers, stimulating transcription of nearby cellular genes, notably those harboring bivalent promoters. Correspondingly, ERV-derived sequences can repress or enhance expression from an adjacent promoter in transgenic embryos depending on their TRIM28 sensitivity in ES cells. TRIM28-mediated control of ERVs is therefore crucial not just to prevent retrotransposition, but more broadly to safeguard the transcriptional dynamics of early embryos.
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Affiliation(s)
- Helen M. Rowe
- School of Life Sciences and Frontiers in Genetics Program, Ecole Polytechnique Fédérale de Lausanne (EPFL), 1015 Lausanne, Switzerland
| | - Adamandia Kapopoulou
- School of Life Sciences and Frontiers in Genetics Program, Ecole Polytechnique Fédérale de Lausanne (EPFL), 1015 Lausanne, Switzerland
- Swiss Bioinformatics Institute, Ecole Polytechnique Fédérale de Lausanne (EPFL), 1015 Lausanne, Switzerland
| | - Andrea Corsinotti
- School of Life Sciences and Frontiers in Genetics Program, Ecole Polytechnique Fédérale de Lausanne (EPFL), 1015 Lausanne, Switzerland
| | - Liana Fasching
- Wallenberg Neuroscience Center, Lund University, BMC A11, 221 84 Lund, Sweden
| | - Todd S. Macfarlan
- Gene Expression Laboratory and the Howard Hughes Medical Institute, The Salk Institute for Biological Studies, La Jolla, California 92037, USA
| | - Yara Tarabay
- Institute of Genetics and Molecular and Cellular Biology (IGBMC), University of Strasbourg, BP10142, Illkirch Cedex, France
| | - Stéphane Viville
- Institute of Genetics and Molecular and Cellular Biology (IGBMC), University of Strasbourg, BP10142, Illkirch Cedex, France
| | - Johan Jakobsson
- Wallenberg Neuroscience Center, Lund University, BMC A11, 221 84 Lund, Sweden
| | - Samuel L. Pfaff
- Gene Expression Laboratory and the Howard Hughes Medical Institute, The Salk Institute for Biological Studies, La Jolla, California 92037, USA
| | - Didier Trono
- School of Life Sciences and Frontiers in Genetics Program, Ecole Polytechnique Fédérale de Lausanne (EPFL), 1015 Lausanne, Switzerland
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115
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Suto JI. QTL mapping of genes controlling plasma insulin and leptin concentrations: metabolic effect of obesity QTLs identified in an F2 intercross between C57BL/6J and DDD.Cg-A(y) inbred mice. J Vet Med Sci 2013; 75:895-907. [PMID: 23439608 DOI: 10.1292/jvms.12-0504] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
DDD.Cg-A(y) female mice developed massive obesity as compared with B6.Cg-A(y) female mice. We previously identified quantitative trait loci (QTLs) for obesity on chromosomes 1, 6, 9 and 17 in F2 female mice, including F2A(y) (F2 mice with the A(y) allele) and F2 non- A(y) mice (F2 mice without the A(y) allele), produced by crossing C57BL/6J and DDD.Cg-A(y) strains. We here addressed the question whether the obesity QTLs share genetic bases with putative QTLs for plasma glucose, insulin and leptin concentrations. We performed QTL analyses for the first principal component (PC1) extracted from these metabolic measurements to identify the genes that contributed to the comprehensive evaluation of metabolic traits. By single QTL scans, we identified two significant QTLs for insulin concentration on chromosomes 6 and 12, three for leptin concentration on chromosomes 1, 6 and 17, and five for PC1 on chromosomes 1, 6, 12 (two loci) and 17. Although insulin and leptin concentrations and PC1 were not normally distributed in combined F2 mice, results of single QTL scans by parametric and non-parametric methods were very similar. Therefore, QTL scan by the parametric method was performed with the agouti locus genotype as a covariate. A significant QTL × covariate interaction was found for PC1 on chromosome 9. All obesity QTLs had significant metabolic effects. Thus, obesity- and diabetes-related traits in DDD.Cg-A(y) mice were largely controlled by QTLs on chromosomes 1, 6, 9, 12 and 17.
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Affiliation(s)
- Jun-ichi Suto
- Agrogenomics Research Center, National Institute of Agrobiological Sciences, Tsukuba, Ibaraki 305-8634, Japan.
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Suto JI. Y chromosome of the inbred mouse KK/Ta strain is associated with reduced body size in Y-consomic strains. BMC Res Notes 2013; 6:64. [PMID: 23418893 PMCID: PMC3598876 DOI: 10.1186/1756-0500-6-64] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2013] [Accepted: 02/11/2013] [Indexed: 11/17/2022] Open
Abstract
Background We have established 17 Y chromosome consomic (Y-consomic) mouse strains in an inbred DH/Sgn strain. In this study, based on investigations in four different genetic backgrounds, we proved that the Y chromosome of the inbred mouse KK/Ta strain is associated with reduced body size. Findings In the DH-Chr Y-+/+ background, Y chromosome substitution significantly decreased the body weight in DH-Chr YKK-+/+ and DH-Chr YSJL-+/+ strains, and the DH-Chr YKK-+/+ strain was the lightest among the 17 Y-consomic strains. In the DH-Chr Y-Dh/+ background (Dh/+ mice have skeletal malformations and are usually lighter than +/+ mice), although Y chromosome substitution did not significantly alter the body weight, the DH-Chr YKK-Dh/+ strain was the lightest among the 17 Y-consomic-Dh/+ strains. In the (B6.Cg-Ay × DH-Chr Y) F1-+/+ background, Y chromosome substitution significantly decreased the body weight and length in the (B6.Cg-Ay × DH-Chr YKK) F1 hybrids. In the (B6.Cg-Ay × DH-Chr Y) F1-Ay/+ background (Ay causes obesity and promotes linear growth), Y chromosome substitution significantly decreased body weight and length in the (B6.Cg-Ay × DH-Chr YKK) F1-Ay/+ hybrids. Conclusion A body-size-reducing effect of the Y chromosome of the KK/Ta mouse strain was observed irrespective of genetic background. The effect was observed in the presence of Dh and Ay, the autosomal dominant mutations, both of which are known to have substantial effects on body size. These results suggest that there are Y-linked genes that control the body size in mice.
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Affiliation(s)
- Jun-ichi Suto
- Agrogenomics Research Center, National Institute of Agrobiological Sciences, Tsukuba, Ibaraki 305-8634, Japan.
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Abstract
Epigenetic medicine is still in its infancy. To date, only a handful of diseases have documented epigenetic correlates upstream of gene regulation including cancer, developmental syndromes and late-onset diseases. The finding that epigenetic markers are dynamic and heterogeneous at tissue and cellular levels, combined with recent identification of a new form of functionally distinct DNA methylation has opened a wider window for investigators to pry into the epigenetic world. It is anticipated that many diseases will be elucidated through this epigenetic inquiry. In this review, we discuss the normal course of DNA methylation during development, taking alcohol as a demonstrator of the epigenetic impact of environmental factors in disease etiology, particularly the growth retardation and neurodevelopmental deficits of fetal alcohol spectrum disorders.
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Affiliation(s)
- Marisol Resendiz
- Stark Neuroscience Research Institute, Indiana University School of Medicine, Indianapolis, IN 46202, USA
| | - Yuanyuan Chen
- Department of Anatomy & Cell Biology, MS508, Indiana University School Medicine, Indianapolis, IN 46202, USA
| | - Nail C Öztürk
- Department of Anatomy & Cell Biology, MS508, Indiana University School Medicine, Indianapolis, IN 46202, USA
- Department of Anatomy, Mersin University School of Medicine, Turkey
| | - Feng C Zhou
- Stark Neuroscience Research Institute, Indiana University School of Medicine, Indianapolis, IN 46202, USA
- Department of Anatomy & Cell Biology, MS508, Indiana University School Medicine, Indianapolis, IN 46202, USA
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Laska MJ, Nissen KK, Nexø BA. (Some) cellular mechanisms influencing the transcription of human endogenous retrovirus, HERV-Fc1. PLoS One 2013; 8:e53895. [PMID: 23382858 PMCID: PMC3557288 DOI: 10.1371/journal.pone.0053895] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2012] [Accepted: 12/06/2012] [Indexed: 11/18/2022] Open
Abstract
DNA methylation and histone acetylation are epigenetic modifications that act as regulators of gene expression. DNA methylation is considered an important mechanism for silencing of retroelements in the mammalian genome. However, the methylation of human endogenous retroviruses (HERVs) is not well investigated. The aim of this study was to investigate the transcriptional potential of HERV-Fc1 proviral 5'LTR in more detail, and examined the specific influence of CpG methylation on this LTR in number of cell lines. Specifically, the role of demethylating chemicals e.g. 5-aza-2' deoxycytidine and Trichostatin-A, in inducing or reactivating expression of HERV-Fc1 specific sequences and the mechanisms were investigated. In our present study, 5-aza-dC is shown to be a powerful inducer of HERV-Fc1, and at the same time it strongly inhibits methylation of DNA. Treatment with this demethylating agent 5-aza-dC, results in significantly increased levels of HERV-Fc1 expression in cells previously not expressing HERV-Fc1, or with a very low expression level. The extent of expression of HERV-Fc1 RNAs precisely correlates with the apparent extent of demethylation of the related DNA sequences. In conclusion, the results suggest that inhibition of DNA methylation/histone deacetylase can interfere with gene silencing mechanisms affecting HERV-Fc1 expression in human cells.
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Akagi K, Li J, Symer DE. How do mammalian transposons induce genetic variation? A conceptual framework: the age, structure, allele frequency, and genome context of transposable elements may define their wide-ranging biological impacts. Bioessays 2013; 35:397-407. [PMID: 23319453 DOI: 10.1002/bies.201200133] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
In this essay, we discuss new insights into the wide-ranging impacts of mammalian transposable elements (TE) on gene expression and function. Nearly half of each mammalian genome is comprised of these mobile, repetitive elements. While most TEs are ancient relics, certain classes can move from one chromosomal location to another even now. Indeed, striking recent data show that extensive transposition occurs not only in the germline over evolutionary time, but also in developing somatic tissues and particular human cancers. While occasional germline TE insertions may contribute to genetic variation, many other, similar TEs appear to have little or no impact on neighboring genes. However, the effects of somatic insertions on gene expression and function remain almost completely unknown. We present a conceptual framework to understand how the ages, allele frequencies, molecular structures, and especially the genomic context of mammalian TEs each can influence their various possible functional consequences.
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Affiliation(s)
- Keiko Akagi
- Human Cancer Genetics Program and Department of Molecular Virology, Immunology, and Medical Genetics, The Ohio State University Comprehensive Cancer Center, Columbus, OH, USA
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Rosenfeld CS, Sieli PT, Warzak DA, Ellersieck MR, Pennington KA, Roberts RM. Maternal exposure to bisphenol A and genistein has minimal effect on A(vy)/a offspring coat color but favors birth of agouti over nonagouti mice. Proc Natl Acad Sci U S A 2013; 110:537-42. [PMID: 23267115 PMCID: PMC3545749 DOI: 10.1073/pnas.1220230110] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
Reports that maternal diet influences coat color in mouse offspring carrying the agouti A(vy) allele have received considerable attention because the range, from pseudoagouti (brown) to yellow, predicts adult health outcomes, especially disposition toward obesity and diabetes, in yellower mice. Bisphenol A (BPA), an endocrine-disrupting compound with estrogenic properties, fed to a/a dams harboring A(vy)/a conceptuses has been reported to induce a significant shift toward yellower mice, whereas consumption of either genistein (G) alone or in combination with BPA led to greater numbers of healthy, brown offspring. Groups of C57/B6 a/a females, which are nonagouti, were fed either a phytoestrogen-free control diet or one of six experimental diets: diets 1-3 contained BPA (50 mg, 5 mg, and 50 μg BPA/kg food, respectively); diet 4 contained G (250 mg/kg food); diet 5 contained G plus BPA (250 and 50 mg/kg food, respectively); and diet 6 contained 0.1 μg of ethinyl estradiol (EE)/kg food. Mice were bred to A(vy)/a males over multiple parities. In all, 2,824 pups from 426 litters were born. None of the diets provided any significant differences in relative numbers of brown, yellow, or intermediate coat color A(vy)/a offspring. However, BPA plus G (P < 0.0001) and EE diets (P = 0.005), but not the four others, decreased the percentage of black (a/a) to A(vy)/a offspring from the expected Mendelian ratio of 1:1. Data suggest that A(vy)/a conceptuses, which may possess a so-called "thrifty genotype," are at a competitive advantage over a/a conceptuses in certain uterine environments.
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Affiliation(s)
| | | | | | | | - Kathleen A. Pennington
- Division of Reproductive and Perinatal Research, Department of Obstetrics Gynecology and Women's Health, University of Missouri, Columbia, MO 65212
| | - R. Michael Roberts
- Bond Life Sciences Center
- Animal Sciences
- Department of Biochemistry, University of Missouri, Columbia, MO 65211; and
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Epigenetics: How Genes and Environment Interact. ENVIRONMENTAL EPIGENOMICS IN HEALTH AND DISEASE 2013. [DOI: 10.1007/978-3-642-23380-7_1] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
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Rietjens IMCM, Sotoca AM, Vervoort J, Louisse J. Mechanisms underlying the dualistic mode of action of major soy isoflavones in relation to cell proliferation and cancer risks. Mol Nutr Food Res 2013; 57:100-13. [PMID: 23175102 DOI: 10.1002/mnfr.201200439] [Citation(s) in RCA: 76] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2012] [Revised: 09/25/2012] [Accepted: 10/08/2012] [Indexed: 12/12/2022]
Abstract
Isoflavones are phytoestrogens that have been linked to both beneficial as well as adverse effects in relation to cell proliferation and cancer risks. The present article presents an overview of these seemingly contradicting health effects and of mechanisms that could be involved in this dualistic mode of action. One mechanism relates to the different ultimate cellular effects of activation of estrogen receptor (ER) α, promoting cell proliferation, and of ERβ, promoting apoptosis, with the major soy isoflavones genistein and daidzein activating especially ERβ. A second mode of action includes the role of epigenetics, including effects of isoflavones on DNA methylation, histone modification and miRNA expression patterns. The overview presented reveals that we are only at the start of unraveling the complex underlying mode of action for effects of isoflavones, both beneficial or adverse, on cell proliferation and cancer risks. It is evident that whatever model system will be applied, its relevance to human tissues with respect to ERα and ERβ levels, co-repressor and co-activator characteristics as well as its relevance to human exposure regimens, needs to be considered and defined.
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Liu L, Aronson J, Lecka-Czernik B. Rosiglitazone disrupts endosteal bone formation during distraction osteogenesis by local adipocytic infiltration. Bone 2013; 52:247-58. [PMID: 23069375 PMCID: PMC3513662 DOI: 10.1016/j.bone.2012.09.038] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/03/2012] [Revised: 09/13/2012] [Accepted: 09/19/2012] [Indexed: 01/14/2023]
Abstract
Rosiglitazone (Rosi) is a drug in the thiazolidinedione class for treatment of type 2 diabetes mellitus (T2DM), which binds and activates PPARγ nuclear receptor in fat cells, sensitizing them to insulin. Despite proven antidiabetic efficacy, Rosi therapy may be associated with trabecular bone loss and an increased risk of fractures. To examine the potential side effects of Rosi treatment on bone formation, we delivered Rosi to mice using a combined model of distraction osteogenesis (DO) and type 2 diabetes mellitus (T2DM). DO provides a unique method to isolate the sequence of intramembranous bone formation, an important component of both fracture healing and bone homeostasis. Four groups of n=6 mice were used to compare the effects of Rosi on bone formation and cellular composition in both diabetic (Avy/a strain) and non-diabetic mice (a/a strain). New bone formation was examined by high resolution radiographs, micro-computed tomography, and histology. Precursor cells in the distraction gap were quantitated using immunohistochemical stains for proliferating cell nuclear antigen. Committed osteoblasts and adipocytes in the gap were identified and quantitated by immunostaining for osteocalcin and FABP4/aP2, respectively. The diabetic model developed obesity, hyperglycemia, hyperinsulinemia and insulin resistance, while the control littermates remained lean, normoglycemic and insulin sensitive. Rosi treatment decreased levels of non-fasted glucose and insulin and improved insulin sensitivity in the A(vy)/a mice, but had no effect in a/a mice, indicating antidiabetic efficacy of Rosi at the tested dose. Despite the diabetic, obese mice having twice the number of fat cells in their marrow than the non-diabetic mice, bone formation using DO was not adversely affected by the diabetes itself. However, Rosi treatment significantly diminished intramembranous endosteal bone formation, while increasing adipogenesis in and adjacent to the distraction gap up to 3.5- to 3.8-fold in both diabetic and non-diabetic models. This effect was independent of the anti-diabetic therapeutic response. These results raise the question of whether osteoblast precursors are inhibited in their development or actually converted to adipocytic phenotypes, possibly via marrow fat PPARγ nuclear receptor.
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Affiliation(s)
- Lichu Liu
- Laboratory for Limb Regeneration Research Arkansas Children’s Hospital Research Institute, 3 Children’s Way, Little Rock, AR 72202
| | - James Aronson
- Laboratory for Limb Regeneration Research Arkansas Children’s Hospital Research Institute, 3 Children’s Way, Little Rock, AR 72202
- Department of Orthopaedic Surgery, Arkansas Children’s Hospital and the University of Arkansas for Medical Sciences, 1 Children’s Way, Little Rock, AR 72202
- Corresponding Author: , Phone (501) 364-1469, Fax (501) 364-1522
| | - Beata Lecka-Czernik
- Departments of Orthopaedic Surgery, Physiology and Pharmacology, University of Toledo Medical Center, 3000 Arlington Ave. Toledo, OH 34614
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Abstract
DNA methylation is a key epigenetic mark when occurring in the promoter and enhancer regions regulates the accessibility of the binding protein and gene transcription. DNA methylation is inheritable and can be de novo-synthesized, erased and reinstated, making it arguably one of the most dynamic upstream regulators for gene expression and the most influential pacer for development. Recent progress has demonstrated that two forms of cytosine methylation and two pathways for demethylation constitute ample complexity for an instructional program for orchestrated gene expression and development. The forum of the current discussion and review are whether there is such a program, if so what the DNA methylation program entails, and what environment can change the DNA methylation program. The translational implication of the DNA methylation program is also proposed.
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Affiliation(s)
- Feng C Zhou
- Department of Anatomy and Cell Biology, Stark Neuroscience Research Institute, Indiana University School Medicine, Indianapolis, IN 46202, USA
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125
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Lemmers RJLF, Tawil R, Petek LM, Balog J, Block GJ, Santen GWE, Amell AM, van der Vliet PJ, Almomani R, Straasheijm KR, Krom YD, Klooster R, Sun Y, den Dunnen JT, Helmer Q, Donlin-Smith CM, Padberg GW, van Engelen BGM, de Greef JC, Aartsma-Rus AM, Frants RR, de Visser M, Desnuelle C, Sacconi S, Filippova GN, Bakker B, Bamshad MJ, Tapscott SJ, Miller DG, van der Maarel SM. Digenic inheritance of an SMCHD1 mutation and an FSHD-permissive D4Z4 allele causes facioscapulohumeral muscular dystrophy type 2. Nat Genet 2012; 44:1370-4. [PMID: 23143600 PMCID: PMC3671095 DOI: 10.1038/ng.2454] [Citation(s) in RCA: 437] [Impact Index Per Article: 36.4] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2012] [Accepted: 10/04/2012] [Indexed: 12/11/2022]
Abstract
Facioscapulohumeral dystrophy (FSHD) is characterized by chromatin relaxation of the D4Z4 macrosatellite array on chromosome 4 and expression of the D4Z4-encoded DUX4 gene in skeletal muscle. The more common form, autosomal dominant FSHD1, is caused by a contraction of the D4Z4 array, whereas the genetic determinants and inheritance of D4Z4 array contraction-independent FSHD2 are unclear. Here we show that mutations in SMCHD1 (structural maintenance of chromosomes flexible hinge domain containing 1) on chromosome 18 reduce SMCHD1 protein levels and segregate with genome-wide D4Z4 CpG hypomethylation in human kindreds. FSHD2 occurs in individuals who inherited both the SMCHD1 mutation and a normal-sized D4Z4 array on a chromosome 4 haplotype permissive for DUX4 expression. Reducing SMCHD1 levels in skeletal muscle results in contraction-independent DUX4 expression. Our study identifies SMCHD1 as an epigenetic modifier of the D4Z4 metastable epiallele and as a causal genetic determinant of FSHD2 and possibly other human diseases subject to epigenetic regulation.
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Affiliation(s)
- Richard J L F Lemmers
- Department of Human Genetics, Leiden University Medical Center, Leiden, The Netherlands
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Suto JI. Quantitative trait locus mapping of genes associated with vacuolation in the adrenal X-zone of the DDD/Sgn inbred mouse. BMC Genet 2012; 13:95. [PMID: 23131041 PMCID: PMC3511235 DOI: 10.1186/1471-2156-13-95] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2012] [Accepted: 11/01/2012] [Indexed: 11/22/2022] Open
Abstract
Background Adrenal gland of mice contains a transient zone between the adrenal cortex and the adrenal medulla: the X-zone. There are clear strain differences in terms of X-zone morphology. Nulliparous females of the inbred mouse DDD strain develop adrenal X-zones containing exclusively vacuolated cells, whereas females of the inbred mouse B6 strain develop X-zones containing only non-vacuolated cells. The X-zone vacuolation is a physiologic process associated with the X-zone degeneration and is tightly regulated by genetic factors. Identification of the genetic factors controlling such strain differences should help analyze the X-zone function. In this study, a quantitative trait locus (QTL) analysis for the extent of X-zone vacuolation was performed for two types of F2 female mice: F2Ay mice (F2 mice with the Ay allele) and F2 non-Ay mice (F2 mice without the Ay allele). These were produced by crossing B6 females and DDD.Cg-Ay males. DDD.Cg-Ay is a congenic mouse strain for the Ay allele at the agouti locus and is used for this study because a close association between the X-zone morphology and the agouti locus genotype has been suggested. The Ay allele is dominant and homozygous lethal; therefore, living Ay mice are invariably heterozygotes. Results Single QTL scans identified significant QTLs on chromosomes 1, 2, 6, and X for F2 non-Ay mice, and on chromosomes 2, 6, and 12 for F2Ay mice. The QTL on chromosome 2 was considered to be because of the agouti locus, which has been suggested to be associated with X-zone vacuolation. A significant QTL that interacted with the agouti locus was identified on chromosome 8. Conclusions The extent of X-zone vacuolation in DDD females was controlled by multiple genes with complex interactions. The murine X-zone is considered analogous structure to the human fetal zone. Therefore, the results of this study will aid in understanding function of not only of the X-zone but also of the human fetal zone. Identifying the genes responsible for the QTLs will be essential for understanding the molecular basis of X-zone function, which is currently unclear.
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Affiliation(s)
- Jun-Ichi Suto
- Agrogenomics Research Center, National Institute of Agrobiological Sciences, Tsukuba, Ibaraki, 305-8634, Japan.
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Bernal AJ, Dolinoy DC, Huang D, Skaar DA, Weinhouse C, Jirtle RL. Adaptive radiation-induced epigenetic alterations mitigated by antioxidants. FASEB J 2012; 27:665-71. [PMID: 23118028 DOI: 10.1096/fj.12-220350] [Citation(s) in RCA: 85] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Humans are exposed to low-dose ionizing radiation (LDIR) from a number of environmental and medical sources. In addition to inducing genetic mutations, there is concern that LDIR may also alter the epigenome. Such heritable effects early in life can either be positively adaptive or result in the enhanced formation of diseases, including cancer, diabetes, and obesity. Herein, we show that LDIR significantly increased DNA methylation at the viable yellow agouti (A(vy)) locus in a sex-specific manner (P=0.004). Average DNA methylation was significantly increased in male offspring exposed to doses between 0.7 and 7.6 cGy, with maximum effects at 1.4 and 3.0 cGy (P<0.01). Offspring coat color was concomitantly shifted toward pseudoagouti (P<0.01). Maternal dietary antioxidant supplementation mitigated both the DNA methylation changes and coat color shift in the irradiated offspring. Thus, LDIR exposure during gestation elicits epigenetic alterations that lead to positive adaptive phenotypic changes that are negated with antioxidants, indicating they are mediated in part by oxidative stress. These findings provide evidence that in the isogenic A(vy) mouse model, epigenetic alterations resulting from LDIR play a role in radiation hormesis, bringing into question the assumption that every dose of radiation is harmful.
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Affiliation(s)
- Autumn J Bernal
- Department of Radiation Oncology, Duke University Medical Center, Durham, North Carolina,, USA
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Oliver KR, Greene WK. Transposable elements and viruses as factors in adaptation and evolution: an expansion and strengthening of the TE-Thrust hypothesis. Ecol Evol 2012; 2:2912-33. [PMID: 23170223 PMCID: PMC3501640 DOI: 10.1002/ece3.400] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2012] [Revised: 09/11/2012] [Accepted: 09/17/2012] [Indexed: 12/17/2022] Open
Abstract
In addition to the strong divergent evolution and significant and episodic evolutionary transitions and speciation we previously attributed to TE-Thrust, we have expanded the hypothesis to more fully account for the contribution of viruses to TE-Thrust and evolution. The concept of symbiosis and holobiontic genomes is acknowledged, with particular emphasis placed on the creativity potential of the union of retroviral genomes with vertebrate genomes. Further expansions of the TE-Thrust hypothesis are proposed regarding a fuller account of horizontal transfer of TEs, the life cycle of TEs, and also, in the case of a mammalian innovation, the contributions of retroviruses to the functions of the placenta. The possibility of drift by TE families within isolated demes or disjunct populations, is acknowledged, and in addition, we suggest the possibility of horizontal transposon transfer into such subpopulations. “Adaptive potential” and “evolutionary potential” are proposed as the extremes of a continuum of “intra-genomic potential” due to TE-Thrust. Specific data is given, indicating “adaptive potential” being realized with regard to insecticide resistance, and other insect adaptations. In this regard, there is agreement between TE-Thrust and the concept of adaptation by a change in allele frequencies. Evidence on the realization of “evolutionary potential” is also presented, which is compatible with the known differential survivals, and radiations of lineages. Collectively, these data further suggest the possibility, or likelihood, of punctuated episodes of speciation events and evolutionary transitions, coinciding with, and heavily underpinned by, intermittent bursts of TE activity.
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Affiliation(s)
- Keith R Oliver
- School of Biological Science and Biotechnology, Faculty of Science and Engineering, Murdoch University Perth, W.A., 6150, Australia
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Suto JI. Quantitative trait locus mapping of genes that control body length and plasma insulin-like growth factor 1 level in mice. BMC Res Notes 2012; 5:547. [PMID: 23031221 PMCID: PMC3517383 DOI: 10.1186/1756-0500-5-547] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2012] [Accepted: 09/20/2012] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND The Ay allele at the agouti locus causes obesity and promotes linear growth in mice. The effect of the Ay allele on obesity has been extensively investigated, whereas its effect on body length is only poorly analyzed. To gain insight into the genetic control of body length, quantitative trait locus (QTL) analysis was performed in F2 female mice produced by crossing C57BL/6 J females and DDD.Cg-Ay males. A congenic DDD.Cg-Ay strain was established by introgressing the Ay allele from the B6.Cg-Ay strain by backcrossing for 12 generations. DDD.Cg-Ay females were longer than B6.Cg-Ay females; therefore, QTLs that interact with the Ay allele may be identified for body length. In addition, QTL analysis was also performed for plasma insulin-like growth factor 1 (IGF1) levels because IGF1 is known to play essential roles in growth and development. If QTLs for IGF1 levels coincide with those for body length, we can gain endocrinological insight into the QTLs for body length. RESULTS Correlations between body length and IGF1 levels were statistically significant in F2 populations. For body length, two significant QTLs were identified on chromosomes 15 and 17. For IGF1 levels, three significant QTLs were identified on chromosomes 10, 12, and 19. QTLs on chromosomes 12 and 19 appeared to be novel, and the latter interacted with the Ay allele. CONCLUSION QTLs for body length and IGF1 levels contained candidate genes that were components of the growth hormone/insulin-like growth factor axis. However, there was no overlap between QTLs for these two traits. Contrary to our expectations, QTLs that interacted with the Ay allele were identified not for body length but for IGF1 levels. Body length and IGF1 levels were, thus, controlled by different sets of genes.
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Affiliation(s)
- Jun-Ichi Suto
- Agrogenomics Research Center, National Institute of Agrobiological Sciences, Tsukuba, Ibaraki 305-8634, Japan.
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Epigenetics: a possible role in acute and transgenerational regulation of dairy cow milk production. Animal 2012; 6:375-81. [PMID: 22436216 DOI: 10.1017/s1751731111002564] [Citation(s) in RCA: 60] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
A potential role for epigenetic mechanisms in the regulation of mammary function in the dairy cow is emerging. Epigenetics is the study of heritable changes in genome function that occur because of chemical changes rather than DNA sequence changes. DNA methylation is an epigenetic event that results in the silencing of gene expression and may be passed on to the next generation. However, recent studies investigating different physiological states and changes in milk protein gene expression suggest that DNA methylation may also play an acute, regulatory, role in gene transcription. This overview will highlight the role of DNA methylation in the silencing of milk protein gene expression during mastitis and mammary involution. Moreover, environmental factors such as nutrition may induce epigenetic modifications of gene expression. The current research investigating the possibility of in utero, hence cross-generational, epigenetic modifications in dairy cows will also be discussed. Understanding how the mammary gland responds to environmental cues provides a potential to enhance milk production not only of the dairy cow but also of her daughter.
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Liu L, Aronson J, Huang S, Lu Y, Czernik P, Rahman S, Kolli V, Suva LJ, Lecka-Czernik B. Rosiglitazone inhibits bone regeneration and causes significant accumulation of fat at sites of new bone formation. Calcif Tissue Int 2012; 91:139-48. [PMID: 22752619 PMCID: PMC3630993 DOI: 10.1007/s00223-012-9623-4] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/02/2012] [Accepted: 06/11/2012] [Indexed: 10/28/2022]
Abstract
Thiazolidinediones (TZDs), peroxisome proliferator-activated receptor gamma activators, and insulin sensitizers represent drugs used to treat hyperglycemia in diabetic patients. Type 2 diabetes mellitus (T2DM) is associated with a twofold increase in fracture risk, and TZDs use increases this risk by an additional twofold. In this study, we analyzed the effect of systemic administration of the TZD rosiglitazone on new bone formation in two in vivo models of bone repair, a model of drilled bone defect regeneration (BDR) and distraction osteogenesis (DO) and a model of extended bone formation. Rosiglitazone significantly inhibited new endosteal bone formation in both models. This effect was correlated with a significant accumulation of fat cells, specifically at sites of bone regeneration. The diminished bone regeneration in the DO model in rosiglitazone-treated animals was associated with a significant decrease in cell proliferation measured by the number of cells expressing proliferating cell nuclear antigen and neovascularization measured by both the number of vascular sinusoids and the number of cells producing proangiogenic vascular endothelial growth factor at the DO site. In summary, rosiglitazone decreased new bone formation in both BDR and DO models of bone repair by mechanisms which include both intrinsic changes in mesenchymal stem cell proliferation and differentiation and changes in the local environment supporting angiogenesis and new bone formation. These studies suggest that bone regeneration may be significantly compromised in T2DM patients on TZD therapy.
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Affiliation(s)
- Lichu Liu
- Arkansas Children’s Hospital Research Institute, University of Arkansas for Medical Sciences, Little Rock, AR, USA
| | - James Aronson
- Arkansas Children’s Hospital Research Institute, University of Arkansas for Medical Sciences, Little Rock, AR, USA
- Department of Orthopaedic Surgery, Center for Orthopaedic Research, University of Arkansas for Medical Sciences, Little Rock, AR, USA
| | - Shilong Huang
- Department of Orthopaedic Surgery, University of Toledo Health Sciences Campus, Toledo, OH, USA
| | - Yalin Lu
- Department of Orthopaedic Surgery, University of Toledo Health Sciences Campus, Toledo, OH, USA
| | - Piotr Czernik
- Department of Orthopaedic Surgery, University of Toledo Health Sciences Campus, Toledo, OH, USA
| | - Sima Rahman
- Department of Orthopaedic Surgery, University of Toledo Health Sciences Campus, Toledo, OH, USA
- Center for Diabetes and Endocrine Research, University of Toledo Health Sciences Campus, Toledo, OH, USA
| | - Vipula Kolli
- Department of Orthopaedic Surgery, University of Toledo Health Sciences Campus, Toledo, OH, USA
| | - Larry J. Suva
- Department of Orthopaedic Surgery, Center for Orthopaedic Research, University of Arkansas for Medical Sciences, Little Rock, AR, USA
| | - Beata Lecka-Czernik
- Department of Orthopaedic Surgery, University of Toledo Health Sciences Campus, Toledo, OH, USA
- Center for Diabetes and Endocrine Research, University of Toledo Health Sciences Campus, Toledo, OH, USA
- Departments of Orthopaedic Surgery, Physiology and Pharmacology, University of Toledo Health Sciences Campus, 3000 Arlington Avenue, Toledo, OH 34614, USA
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132
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Anderson OS, Sant KE, Dolinoy DC. Nutrition and epigenetics: an interplay of dietary methyl donors, one-carbon metabolism and DNA methylation. J Nutr Biochem 2012; 23:853-9. [PMID: 22749138 DOI: 10.1016/j.jnutbio.2012.03.003] [Citation(s) in RCA: 477] [Impact Index Per Article: 39.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2011] [Revised: 03/19/2012] [Accepted: 03/29/2012] [Indexed: 01/17/2023]
Abstract
DNA methylation is the most extensively studied mechanism of epigenetic gene regulation. Increasing evidence indicates that DNA methylation is labile in response to nutritional and environmental influences. Alterations in DNA methylation profiles can lead to changes in gene expression, resulting in diverse phenotypes with the potential for increased disease risk. The primary methyl donor for DNA methylation is S-adenosylmethionine (SAM), a species generated in the cyclical cellular process called one-carbon metabolism. One-carbon metabolism is catalyzed by several enzymes in the presence of dietary micronutrients, including folate, choline, betaine and other B vitamins. For this reason, nutrition status, particularly micronutrient intake, has been a focal point when investigating epigenetic mechanisms. Although animal evidence linking nutrition and DNA methylation is fairly extensive, epidemiological evidence is less comprehensive. This review serves to integrate studies of the animal in vivo with human epidemiological data pertaining to nutritional regulation of DNA methylation and to further identify areas in which current knowledge is limited.
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Affiliation(s)
- Olivia S Anderson
- Department of Environmental Health Sciences, University of Michigan, Ann Arbor, MI 48109-2029, USA
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133
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Isbel L, Whitelaw E. Endogenous retroviruses in mammals: an emerging picture of how ERVs modify expression of adjacent genes. Bioessays 2012; 34:734-8. [PMID: 22736292 DOI: 10.1002/bies.201200056] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Endogenous retrovirsuses (ERVs) have long been known to influence gene expression in plants in important ways, but what of their roles in mammals? Our relatively sparse knowledge in that area was recently increased with the finding that ERVs can influence the expression of mammalian resident genes by disrupting transcriptional termination. For many mammalian biologists, retrotransposition is considered unimportant except when it disrupts the reading frame of a gene, but this view continues to be challenged. It has been known for some time that integration into an intron can create novel transcripts and integration upstream of a gene can alter the expression of the transcript, in many cases producing phenotypic consequences and disease. The new findings on transcriptional termination extend the opportunities for retrotransposons to play a role in human disease.
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Affiliation(s)
- Luke Isbel
- Queensland Institute of Medical Research, PO Royal Brisbane Hospital, Brisbane, Queensland, Australia
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134
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Nellåker C, Keane TM, Yalcin B, Wong K, Agam A, Belgard TG, Flint J, Adams DJ, Frankel WN, Ponting CP. The genomic landscape shaped by selection on transposable elements across 18 mouse strains. Genome Biol 2012; 13:R45. [PMID: 22703977 PMCID: PMC3446317 DOI: 10.1186/gb-2012-13-6-r45] [Citation(s) in RCA: 127] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2012] [Revised: 05/25/2012] [Accepted: 06/15/2012] [Indexed: 12/20/2022] Open
Abstract
Background Transposable element (TE)-derived sequence dominates the landscape of mammalian genomes and can modulate gene function by dysregulating transcription and translation. Our current knowledge of TEs in laboratory mouse strains is limited primarily to those present in the C57BL/6J reference genome, with most mouse TEs being drawn from three distinct classes, namely short interspersed nuclear elements (SINEs), long interspersed nuclear elements (LINEs) and the endogenous retrovirus (ERV) superfamily. Despite their high prevalence, the different genomic and gene properties controlling whether TEs are preferentially purged from, or are retained by, genetic drift or positive selection in mammalian genomes remain poorly defined. Results Using whole genome sequencing data from 13 classical laboratory and 4 wild-derived mouse inbred strains, we developed a comprehensive catalogue of 103,798 polymorphic TE variants. We employ this extensive data set to characterize TE variants across the Mus lineage, and to infer neutral and selective processes that have acted over 2 million years. Our results indicate that the majority of TE variants are introduced though the male germline and that only a minority of TE variants exert detectable changes in gene expression. However, among genes with differential expression across the strains there are twice as many TE variants identified as being putative causal variants as expected. Conclusions Most TE variants that cause gene expression changes appear to be purged rapidly by purifying selection. Our findings demonstrate that past TE insertions have often been highly deleterious, and help to prioritize TE variants according to their likely contribution to gene expression or phenotype variation.
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Affiliation(s)
- Christoffer Nellåker
- MRC Functional Genomics Unit, Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, UK.
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135
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136
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Anderson OS, Nahar MS, Faulk C, Jones TR, Liao C, Kannan K, Weinhouse C, Rozek LS, Dolinoy DC. Epigenetic responses following maternal dietary exposure to physiologically relevant levels of bisphenol A. ENVIRONMENTAL AND MOLECULAR MUTAGENESIS 2012; 53:334-42. [PMID: 22467340 PMCID: PMC3570056 DOI: 10.1002/em.21692] [Citation(s) in RCA: 91] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/23/2011] [Revised: 02/28/2012] [Accepted: 02/29/2012] [Indexed: 05/18/2023]
Abstract
Animal studies have linked perinatal bisphenol A (BPA) exposure to altered DNA methylation, but little attention is given to analyzing multiple physiologically relevant doses. Utilizing the viable yellow agouti (A(vy)) mouse, we examine the effects of developmental exposure through maternal diet to 50 ng BPA/kg (n = 14 litters), 50 μg BPA/kg (n = 9 litters), or 50 mg BPA/kg (n = 13 litters) on global and candidate gene methylation at postnatal day 22. Global methylation analysis reveals hypermethylation in tail tissue of a/a and A(vy)/a offspring across all dose groups compared with controls (n = 11 litters; P < 0.02). Analysis of coat color phenotype replicates previous work showing that the distribution of 50 mg BPA/kg A(vy)/a offspring shifts toward yellow (P = 0.006) by decreasing DNA methylation in the retrotransposon upstream of the Agouti gene (P = 0.03). Maternal exposure to 50 μg or 50 ng BPA/kg, however, results in altered coat color distributions in comparison with control (P = 0.04 and 0.02), but no DNA methylation effects at the Agouti gene are noted. DNA methylation at the CDK5 activator-binding protein (Cabp(IAP)) metastable epiallele shows hypermethylation in the 50 μg BPA/kg offspring, compared with controls (P = 0.02). Comparison of exposed mouse liver BPA levels to human fetal liver BPA levels indicates that the three experimental exposures are physiologically relevant. Thus, perinatal BPA exposure affects offspring phenotype and epigenetic regulation across multiple doses, indicating the need to evaluate dose effects in human clinical and population studies.
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Affiliation(s)
- Olivia S. Anderson
- Department of Environmental Health Sciences, University of Michigan, Ann Arbor, Michigan
| | - Muna S. Nahar
- Department of Environmental Health Sciences, University of Michigan, Ann Arbor, Michigan
| | - Christopher Faulk
- Department of Environmental Health Sciences, University of Michigan, Ann Arbor, Michigan
| | - Tamara R. Jones
- Department of Environmental Health Sciences, University of Michigan, Ann Arbor, Michigan
| | - Chunyang Liao
- Wadsworth Center, New York State Department of Health and Department of Environmental Health Sciences, State University of New York at Albany, Albany, New York
| | - Kurunthachalam Kannan
- Wadsworth Center, New York State Department of Health and Department of Environmental Health Sciences, State University of New York at Albany, Albany, New York
| | - Caren Weinhouse
- Department of Environmental Health Sciences, University of Michigan, Ann Arbor, Michigan
| | - Laura S. Rozek
- Department of Environmental Health Sciences, University of Michigan, Ann Arbor, Michigan
- Department of Otolaryngology, University of Michigan, Ann Arbor, Michigan
| | - Dana C. Dolinoy
- Department of Environmental Health Sciences, University of Michigan, Ann Arbor, Michigan
- Correspondence to: Dana C. Dolinoy, 1415 Washington Heights, Ann Arbor, MI 48109-2029, USA.
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137
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Albrecht E, Komolka K, Kuzinski J, Maak S. Agouti revisited: transcript quantification of the ASIP gene in bovine tissues related to protein expression and localization. PLoS One 2012; 7:e35282. [PMID: 22530003 PMCID: PMC3328439 DOI: 10.1371/journal.pone.0035282] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2011] [Accepted: 03/14/2012] [Indexed: 02/07/2023] Open
Abstract
Beside its role in melanogenesis, the agouti signaling protein (ASIP) has been related to obesity. The potentially crucial role in adipocyte development makes it a tempting candidate for economic relevant, fat related traits in farm animals. The objective of our study was to characterize the mRNA expression of different ASIP transcripts and of putative targets in different bovine tissues, as well as to study consequences on protein abundance and localization. ASIP mRNA abundance was determined by RT-qPCR in adipose and further tissues of cattle representing different breeds and crosses. ASIP mRNA was up-regulated more than 9-fold in intramuscular fat of Japanese Black cattle compared to Holstein (p<0.001). Further analyses revealed that a transposon-derived transcript was solely responsible for the increased ASIP mRNA abundance. This transcript was observed in single individuals of different breeds indicating a wide spread occurrence of this insertion at the ASIP locus in cattle. The protein was detected in different adipose tissues, skin, lung and liver, but not in skeletal muscle by Western blot with a bovine-specific ASIP antibody. However, the protein abundance was not related to the observed ASIP mRNA over-expression. Immuno-histochemical analyses revealed a putative nuclear localization of ASIP additionally to the expected cytosolic signal in different cell types. The expression of melanocortin receptors (MCR) 1 to 5 as potential targets for ASIP was analyzed by RT-PCR in subcutaneous fat. Only MC1R and MC4R were detected indicating a similar receptor expression like in human adipose tissue. Our results provide evidence for a widespread expression of ASIP in bovine tissues at mRNA and, for the first time, at protein level. ASIP protein is detectable in adipocytes as well as in further cells of adipose tissue. We generated a basis for a more detailed investigation of ASIP function in peripheral tissues of various mammalian species.
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Affiliation(s)
- Elke Albrecht
- Research Unit Muscle Biology and Growth, Leibniz Institute for Farm Animal Biology, Dummerstorf, Germany
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138
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Li CCY, Maloney CA, Cropley JE, Suter CM. Epigenetic programming by maternal nutrition: shaping future generations. Epigenomics 2012; 2:539-49. [PMID: 22121973 DOI: 10.2217/epi.10.33] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
Within the Western world's aging and increasingly overweight population, we are seeing an increasing prevalence of adult-onset, lifestyle-related disease such as diabetes, hypertension and atherosclerosis. There is significant evidence that suboptimal nutrition in pregnancy can lead to an increased risk of these diseases developing in offspring, and that this increased risk can be heritable. Thus, poor in utero nutrition may be a major contributor to the current cycle of obesity. While the molecular basis of this phenomenon is unknown, available evidence suggests that it can be mediated by epigenetic changes to gene expression. Here, we discuss epigenetics as a mediator of disease risk in response to nutritional cues. The potential for maternal nutrition to heritably alter epigenetic states may have implications for population health and adaptive evolution.
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Affiliation(s)
- Cheryl Chui Ying Li
- Victor Chang Cardiac Research Institute, Lowy Packer Building, 405 Liverpool Street, Darlinghurst, NSW 2010, Australia
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139
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Priestley CC, Anderton M, Doherty AT, Duffy P, Mellor HR, Powell H, Roberts R. Epigenetics – relevance to drug safety science. Toxicol Res (Camb) 2012. [DOI: 10.1039/c2tx00003b] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Abstract
Epigenetics describes the study of heritable changes in gene expression that occur in the absence of a change to the DNA sequence. Specific patterns of epigenetic signatures can be stably transmitted through mitosis and cell division and form the molecular basis for developmental stage- and cell type-specific gene expression. Associations have been observed that endogenous and exogenous stimuli can change the epigenetic control of both somatic and stem cell differentiation and thus influence phenotypic behaviours and/or disease progression. In relation to drug safety, DNA methylation changes have been identified in many stages of tumour development following exposure to non-genotoxic carcinogens. However, it is not clear whether DNA methylation changes cause cancer, or arise as a consequence of the transformed state. Toxic agents could act at different levels, by directly modifying the epigenome or indirectly by altering signalling pathways. These alterations in chromatin structure may or may not be heritable but are probably reversible. That said, there is currently insufficient data to support inclusion of epigenetic profiling into pre-clinical evaluation studies. Several international collaborations aim to generate data to determine whether epigenetic modifications are causal links in disease and/or tumour progression. It will only be when an understanding of chemical mode-of-action is required that evaluation of epigenetic changes might be considered. The current toxicological testing battery is expected to identify any potential adverse effects regardless of the mechanism, epigenetic or otherwise. It is recommended that toxicologists keep a close watch of new developments in this field, in particular identification of early epigenetic markers for non-genotoxic carcinogenicity. Scientific collaborations between academia and industry will help to understand inter-individual variations in response to drug and toxin exposure to be able to distinguish between adverse and non-adverse epigenetic changes.
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Affiliation(s)
- Catherine C. Priestley
- Safety Assessment, AstraZeneca R&D, Alderley Park, Macclesfield, Cheshire, SK10 4TG, UK. Fax: +44 1625 231281; Tel: +44 1625 232435
| | - Mark Anderton
- Safety Assessment, AstraZeneca R&D, Alderley Park, Macclesfield, Cheshire, SK10 4TG, UK. Fax: +44 1625 231281; Tel: +44 1625 232435
| | - Ann T. Doherty
- Safety Assessment, AstraZeneca R&D, Alderley Park, Macclesfield, Cheshire, SK10 4TG, UK. Fax: +44 1625 231281; Tel: +44 1625 232435
| | - Paul Duffy
- Safety Assessment, AstraZeneca R&D, Alderley Park, Macclesfield, Cheshire, SK10 4TG, UK. Fax: +44 1625 231281; Tel: +44 1625 232435
| | - Howard R. Mellor
- Safety Assessment, AstraZeneca R&D, Alderley Park, Macclesfield, Cheshire, SK10 4TG, UK. Fax: +44 1625 231281; Tel: +44 1625 232435
| | - Helen Powell
- Safety Assessment, AstraZeneca R&D, Alderley Park, Macclesfield, Cheshire, SK10 4TG, UK. Fax: +44 1625 231281; Tel: +44 1625 232435
| | - Ruth Roberts
- Safety Assessment, AstraZeneca R&D, Alderley Park, Macclesfield, Cheshire, SK10 4TG, UK. Fax: +44 1625 231281; Tel: +44 1625 232435
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140
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Cropley JE, Dang THY, Martin DIK, Suter CM. The penetrance of an epigenetic trait in mice is progressively yet reversibly increased by selection and environment. Proc Biol Sci 2012; 279:2347-53. [PMID: 22319121 DOI: 10.1098/rspb.2011.2646] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
Natural selection acts on variation that is typically assumed to be genetic in origin. But epigenetic mechanisms, which are interposed between the genome and its environment, can create diversity independently of genetic variation. Epigenetic states can respond to environmental cues, and can be heritable, thus providing a means by which environmentally responsive phenotypes might be selectable independent of genotype. Here, we have tested the possibility that environment and selection can act together to increase the penetrance of an epigenetically determined phenotype. We used isogenic A(vy) mice, in which the epigenetic state of the A(vy) allele is sensitive to dietary methyl donors. By combining methyl donor supplementation with selection for a silent A(vy) allele, we progressively increased the prevalence of the associated phenotype in the population over five generations. After withdrawal of the dietary supplement, the shift persisted for one generation but was lost in subsequent generations. Our data provide the first demonstration that selection for a purely epigenetic trait can result in cumulative germline effects in mammals. These results present an alternative to the paradigm that natural selection acts only on genetic variation, and suggest that epigenetic changes could underlie rapid adaptation of species in response to natural environmental fluctuations.
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Affiliation(s)
- Jennifer E Cropley
- Victor Chang Cardiac Research Institute, Darlinghurst, New South Wales 2010, Australia
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141
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Krings A, Rahman S, Huang S, Lu Y, Czernik P, Lecka-Czernik B. Bone marrow fat has brown adipose tissue characteristics, which are attenuated with aging and diabetes. Bone 2012; 50:546-52. [PMID: 21723971 PMCID: PMC3214232 DOI: 10.1016/j.bone.2011.06.016] [Citation(s) in RCA: 199] [Impact Index Per Article: 16.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/14/2011] [Revised: 06/12/2011] [Accepted: 06/15/2011] [Indexed: 11/28/2022]
Abstract
Fat occupies a significant portion of bone cavity however its function is largely unknown. Marrow fat expands during aging and in conditions which affect energy metabolism, indicating that fat in bone is under similar regulatory mechanisms as other fat depots. On the other hand, its location may determine specific functions in the maintenance of the environment for bone remodeling and hematopoiesis. We have demonstrated that marrow fat has a distinctive phenotype, which resembles both, white and brown adipose tissue (WAT and BAT, respectively). Marrow adipocytes express gene markers of brown adipocytes at levels characteristic for the BAT, including transcription factor Prdm16, and regulators of thermogenesis such as deiodinase 2 (Dio2) and PGC1α. The levels of expression of BAT-specific gene markers are decreased in bone of 24 mo old C57BL/6 and in diabetic yellow agouti A(vy)/a mice implicating functional changes of marrow fat occurring with aging and diabetes. Administration of antidiabetic TZD rosiglitazone, which sensitizes cells to insulin and increases adipocyte metabolic functions, significantly increased both, BAT (UCP1, PGC1α, Dio2, β3AR, Prdm16, and FoxC2) and WAT (adiponectin and leptin) gene expression in marrow of normoglycemic C57BL/6 mice, but failed to increase the expression of BAT, but not WAT, gene markers in diabetic mice. In conclusion, the metabolic phenotype of marrow fat combines both BAT and WAT characteristics. Decrease in BAT-like characteristics with aging and diabetes may contribute to the negative changes in the marrow environment supporting bone remodeling and hematopoiesis.
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Affiliation(s)
- A. Krings
- Department of Orthopaedic Surgery, University of Toledo Health Sciences Campus, Toledo, OH 43614
| | - S. Rahman
- Department of Orthopaedic Surgery, University of Toledo Health Sciences Campus, Toledo, OH 43614
| | - S. Huang
- Department of Orthopaedic Surgery, University of Toledo Health Sciences Campus, Toledo, OH 43614
| | - Y. Lu
- Department of Orthopaedic Surgery, University of Toledo Health Sciences Campus, Toledo, OH 43614
| | - P.J. Czernik
- Department of Orthopaedic Surgery, University of Toledo Health Sciences Campus, Toledo, OH 43614
| | - B. Lecka-Czernik
- Department of Orthopaedic Surgery, University of Toledo Health Sciences Campus, Toledo, OH 43614
- Department of Physiology and Pharmacology, University of Toledo Health Sciences Campus, Toledo, OH 43614
- Center for Diabetes and Endocrine Research, University of Toledo Health Sciences Campus, Toledo, OH 43614
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142
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Understanding transgenerational epigenetic inheritance via the gametes in mammals. Nat Rev Genet 2012; 13:153-62. [PMID: 22290458 DOI: 10.1038/nrg3188] [Citation(s) in RCA: 430] [Impact Index Per Article: 35.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
It is known that information that is not contained in the DNA sequence - epigenetic information - can be inherited from the parent to the offspring. However, many questions remain unanswered regarding the extent and mechanisms of such inheritance. In this Review, we consider the evidence for transgenerational epigenetic inheritance via the gametes, including cases of environmentally induced epigenetic changes. The molecular basis of this inheritance remains unclear, but recent evidence points towards diffusible factors, in particular RNA, rather than DNA methylation or chromatin. Interestingly, many cases of epigenetic inheritance seem to involve repeat sequences.
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143
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Su LJ, Mahabir S, Ellison GL, McGuinn LA, Reid BC. Epigenetic Contributions to the Relationship between Cancer and Dietary Intake of Nutrients, Bioactive Food Components, and Environmental Toxicants. Front Genet 2012; 2:91. [PMID: 22303385 PMCID: PMC3266615 DOI: 10.3389/fgene.2011.00091] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2011] [Accepted: 12/06/2011] [Indexed: 12/21/2022] Open
Abstract
Epigenetics is the study of heritable changes in gene expression that occur without a change in DNA sequence. Cancer is a multistep process derived from combinational crosstalk between genetic alterations and epigenetic influences through various environmental factors. The observation that epigenetic changes are reversible makes them an attractive target for cancer prevention. Until recently, there have been difficulties studying epigenetic mechanisms in interactions between dietary factors and environmental toxicants. The development of the field of cancer epigenetics during the past decade has been advanced rapidly by genome-wide technologies - which initially employed microarrays but increasingly are using high-throughput sequencing - which helped to improve the quality of the analysis, increase the capacity of sample throughput, and reduce the cost of assays. It is particularly true for applications of cancer epigenetics in epidemiologic studies that examine the relationship among diet, epigenetics, and cancer because of the issues of tissue heterogeneity, the often limiting amount of DNA samples, and the significant cost of the analyses. This review offers an overview of the state of the science in nutrition, environmental toxicants, epigenetics, and cancer to stimulate further exploration of this important and developing area of science. Additional epidemiologic research is needed to clarify the relationship between these complex epigenetic mechanisms and cancer.
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Affiliation(s)
- L. Joseph Su
- Modifiable Risk Factors Branch, Division of Cancer Control and Population Sciences, National Cancer InstituteBethesda, MD, USA
| | - Somdat Mahabir
- Modifiable Risk Factors Branch, Division of Cancer Control and Population Sciences, National Cancer InstituteBethesda, MD, USA
| | - Gary L. Ellison
- Modifiable Risk Factors Branch, Division of Cancer Control and Population Sciences, National Cancer InstituteBethesda, MD, USA
| | - Laura A. McGuinn
- Modifiable Risk Factors Branch, Division of Cancer Control and Population Sciences, National Cancer InstituteBethesda, MD, USA
| | - Britt C. Reid
- Modifiable Risk Factors Branch, Division of Cancer Control and Population Sciences, National Cancer InstituteBethesda, MD, USA
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144
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Biebermann H, Kühnen P, Kleinau G, Krude H. The neuroendocrine circuitry controlled by POMC, MSH, and AGRP. Handb Exp Pharmacol 2012:47-75. [PMID: 22249810 DOI: 10.1007/978-3-642-24716-3_3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Obesity is one of the most challenging health problems worldwide. Over the past few decades, our knowledge concerning mechanisms of weight regulation has increased tremendously leading to the identification of the leptin-melanocortin pathway. The filling level of energy stores is signaled to the brain, and the information is integrated by hypothalamic nuclei, resulting in a well-orchestrated response to food intake and energy expenditure to ensure constant body weight. One of the key players in this system is proopiomelanocortin (POMC), a precursor of a variety of neuropeptides. POMC-derived alpha- and beta-MSH play an important role in energy homeostasis by activating melanocortin receptors expressed in the arcuate nucleus (MC3R) and in the nucleus paraventricularis (MC4R). Activation of these two G protein-coupled receptors is antagonized by agouti-related peptide (AgRP). Naturally occurring mutations in this system were identified in patients suffering from common obesity as well as in patients demonstrating a phenotype of severe early-onset obesity, adrenal insufficiency, red hair, and pale skin. Detailed understanding of the complex system of POMC-AgRP-MC3R-MC4R and their interaction with other hypothalamic as well as peripheral signals is a prerequisite to combat the obesity epidemic.
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Affiliation(s)
- Heike Biebermann
- Institut für Experimentelle Pädiatrische Endokrinologie, Charité Universitätsmedizin Berlin, Augustenburger Platz 1, 13353 Berlin, Germany.
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145
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Abstract
During preimplantation development, major epigenetic reprogramming occurs, erasing gametic modifications, and establishing embryonic epigenetic modifications. Given the plasticity of these modifications, they are susceptible to disruption by assisted reproductive technologies, including embryo culture. The current state of evidence is presented for the effects of embryo culture on global DNA methylation and histone modifications, retroviral silencing, X-inactivation, and genomic imprinting. Several salient points emerge from the literature; that culture in the absence of other procedures can lead to epigenetic perturbations; that all media are suboptimal; and that embryo response to in vitro culture is stochastic. We propose that embryos adapt to the suboptimal environment generated by embryo culture, including epigenetic adaptations, and that "quiet" embryos may be the least epigenetically compromised by in vitro culture.
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146
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Suto JI. Quantitative trait loci that control plasma lipid levels in an F2 intercross between C57BL/6J and DDD.Cg-A(y) inbred mouse strains. J Vet Med Sci 2011; 74:449-56. [PMID: 22123309 DOI: 10.1292/jvms.11-0430] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The objectives of this study were to characterize plasma lipid phenotypes and dissect the genetic basis of plasma lipid levels in an obese DDD.Cg-A(y) mouse strain. Plasma triglyceride (TG) levels were significantly higher in the DDD.Cg-A(y) strain than in the B6.Cg-A(y) strain. In contrast, plasma total-cholesterol (CHO) levels did not substantially differ between the two strains. As a rule, the A(y) allele significantly increased TG levels, but did not increase CHO levels. Quantitative trait locus (QTL) analyses for plasma TG and CHO levels were performed in two types of F(2) female mice [F(2)A(y) (F(2) mice carrying the A(y) allele) and F(2) non- A(y) mice (F(2) mice without the A(y) allele)] produced by crossing C57BL/6J females and DDD.Cg-A(y) males. Single QTL scan identified one significant QTL for TG levels on chromosome 1, and two significant QTLs for CHO levels on chromosomes 1 and 8. When the marker nearest to the QTL on chromosome 1 was used as covariates, four additional significant QTLs for CHO levels were identified on chromosomes 5, 6, and 17 (two loci). In contrast, consideration of the agouti locus genotype as covariates did not detect additional QTLs. DDD.Cg-A(y) showed a low CHO level, although it had Apoa2(b), which was a CHO-increasing allele at the Apoa2 locus. This may have been partly due to the presence of multiple QTLs, which were associated with decreased CHO levels, on chromosome 8.
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Affiliation(s)
- Jun-ichi Suto
- Agrogenomics Research Center, National Institute of Agrobiological Sciences, Tsukuba, Ibaraki 305-8634, Japan.
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147
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Maternal nutritional status, C(1) metabolism and offspring DNA methylation: a review of current evidence in human subjects. Proc Nutr Soc 2011; 71:154-65. [PMID: 22124338 PMCID: PMC3491641 DOI: 10.1017/s0029665111003338] [Citation(s) in RCA: 120] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Evidence is growing for the long-term effects of environmental factors during early-life on later disease susceptibility. It is believed that epigenetic mechanisms (changes in gene function not mediated by DNA sequence alteration), particularly DNA methylation, play a role in these processes. This paper reviews the current state of knowledge of the involvement of C1 metabolism and methyl donors and cofactors in maternal diet-induced DNA methylation changes in utero as an epigenetic mechanism. Methyl groups for DNA methylation are mostly derived from the diet and supplied through C1 metabolism by way of choline, betaine, methionine or folate, with involvement of riboflavin and vitamins B6 and B12 as cofactors. Mouse models have shown that epigenetic features, for example DNA methylation, can be altered by periconceptional nutritional interventions such as folate supplementation, thereby changing offspring phenotype. Evidence of early nutrient-induced epigenetic change in human subjects is scant, but it is known that during pregnancy C1 metabolism has to cope with high fetal demands for folate and choline needed for neural tube closure and normal development. Retrospective studies investigating the effect of famine or season during pregnancy indicate that variation in early environmental exposure in utero leads to differences in DNA methylation of offspring. This may affect gene expression in the offspring. Further research is needed to examine the real impact of maternal nutrient availability on DNA methylation in the developing fetus.
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148
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Yamamuro Y, Shiraishi A. Genotype-dependent participation of coat color gene loci in the behavioral traits of laboratory mice. Behav Processes 2011; 88:81-7. [PMID: 21854838 DOI: 10.1016/j.beproc.2011.08.004] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2011] [Revised: 07/21/2011] [Accepted: 08/02/2011] [Indexed: 10/17/2022]
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149
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Weinhouse C, Anderson OS, Jones TR, Kim J, Liberman SA, Nahar MS, Rozek LS, Jirtle RL, Dolinoy DC. An expression microarray approach for the identification of metastable epialleles in the mouse genome. Epigenetics 2011; 6:1105-13. [PMID: 21829099 DOI: 10.4161/epi.6.9.17103] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
Genetic loci displaying environmentally responsive epigenetic marks, termed metastable epialleles, offer a solution to the paradox presented by genetically identical yet phenotypically distinct individuals. The murine viable yellow agouti (A (vy) ) metastable epiallele exhibits stochastic DNA methylation and histone modifications associated with coat color variation in isogenic individuals. The distribution of A (vy) variable expressivity shifts following maternal nutritional and environmental exposures. To characterize additional murine metastable epialleles, we utilized genome-wide expression arrays (N = 10 male individuals, 3 tissues per individual) and identified candidates displaying large variability in gene expression among individuals (Vi = inter-individual variance), concomitant with a low variability in gene expression across tissues from the three germ layers (Vt = inter-tissue variance), two features characteristic of the A (vy) metastable epiallele. The CpG island in the promoter of Dnajb1 and two contraoriented ERV class II repeats in Glcci1 were validated to display underlying stochasticity in methylation patterns common to metastable epialleles. Furthermore, liver DNA methylation in mice exposed in utero to 50 mg bisphenol A (BPA)/kg diet (N = 91) or a control diet (N = 79) confirmed environmental lability at validated candidate genes. Significant effects of exposure on mean CpG methylation were observed at the Glcci1 Repeat 1 locus (p < 0.0001). Significant effects of BPA also were observed at the first and fifth CpG sites studied in Glcci1 Repeat 2 (p < 0.0001 and p = 0.004, respectively). BPA did not affect methylation in the promoter of Dnajb1 (p = 0.59). The characterization of metastable epialleles in humans is crucial for the development of novel screening and therapeutic targets for human disease prevention.
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Affiliation(s)
- Caren Weinhouse
- Department of Environmental Health Sciences; University of Michigan, Ann Arbor, MI, USA
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150
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Karimi MM, Goyal P, Maksakova IA, Bilenky M, Leung D, Tang JX, Shinkai Y, Mager DL, Jones S, Hirst M, Lorincz MC. DNA methylation and SETDB1/H3K9me3 regulate predominantly distinct sets of genes, retroelements, and chimeric transcripts in mESCs. Cell Stem Cell 2011; 8:676-87. [PMID: 21624812 PMCID: PMC3857791 DOI: 10.1016/j.stem.2011.04.004] [Citation(s) in RCA: 370] [Impact Index Per Article: 28.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2010] [Revised: 02/18/2011] [Accepted: 04/04/2011] [Indexed: 01/14/2023]
Abstract
DNA methylation and histone H3 lysine 9 trimethylation (H3K9me3) play important roles in silencing of genes and retroelements. However, a comprehensive comparison of genes and repetitive elements repressed by these pathways has not been reported. Here we show that in mouse embryonic stem cells (mESCs), the genes upregulated after deletion of the H3K9 methyltransferase Setdb1 are distinct from those derepressed in mESC deficient in the DNA methyltransferases Dnmt1, Dnmt3a, and Dnmt3b, with the exception of a small number of primarily germline-specific genes. Numerous endogenous retroviruses (ERVs) lose H3K9me3 and are concomitantly derepressed exclusively in SETDB1 knockout mESCs. Strikingly, ~15% of upregulated genes are induced in association with derepression of promoter-proximal ERVs, half in the context of "chimeric" transcripts that initiate within these retroelements and splice to genic exons. Thus, SETDB1 plays a previously unappreciated yet critical role in inhibiting aberrant gene transcription by suppressing the expression of proximal ERVs.
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Affiliation(s)
- Mohammad M Karimi
- Department of Medical Genetics, Life Sciences Institute, The University of British Columbia, Vancouver, British Columbia, V6T 1Z3, Canada
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