Time to take epigenetic inheritance seriously

Exploring adolescence as a key life history stage in bioarchaeology

Adolescence is a unique period in the life history of an individual. It is characterized by a myriad of changes that bioarchaeologists are only just coming to appreciate, related to sexual maturation, linear growth, immunological transformation, and emotional and cognitive development. New methods allow us to measure this age of transition through the stages of the adolescent growth, as a proxy for the physical development associated with sexual maturation (puberty). This review outlines ways bioarchaeologists may draw on research developments from the fields of human biology, evolutionary theory and neurobiology to advance a more holistic approach to the study of adolescence in the past. It considers current theoretical and analytical approaches to highlight the research potential of this critical stage of life history. This synthesis integrates the most recent research in the medical sciences concerned with body and brain development, and outlines the biological processes involved with sexual and physical maturation of the adolescent. The goal of this review is to help inform potentially rewarding areas of research that bioarchaeologists can contribute to and draw from, as well as the challenges and limitations, theoretical and methodological questions, and ways in which we can develop the study of adolescence in the discipline going forward.

Building an Asymmetrical Brain: The Molecular Perspective

The brain is one of the most prominent examples for structural and functional differences between the left and right half of the body. For handedness and language lateralization, the most widely investigated behavioral phenotypes, only a small fraction of phenotypic variance has been explained by molecular genetic studies. Due to environmental factors presumably also playing a role in their ontogenesis and based on first molecular evidence, it has been suggested that functional hemispheric asymmetries are partly under epigenetic control. This review article aims to elucidate the molecular factors underlying hemispheric asymmetries and their association with inner organ asymmetries. While we previously suggested that epigenetic mechanisms might partly account for the missing heritability of handedness, this article extends this idea by suggesting possible alternatives for transgenerational transmission of epigenetic states that do not require germ line epigenetic transmission. This is in line with a multifactorial model of hemispheric asymmetries, integrating genetic, environmental, and epigenetic influencing factors in their ontogenesis.

Vitamin-caused faulty perinatal hormonal imprinting and its consequences in adult age

Lipid-soluble vitamins (vitamins A, D, E, and K) are actually hormones (exohormones), as they can be directly bound by hormone receptors or are in connection with molecules, which influence hormone receptors. Vitamin D is a transition between endo- and exohormones and the possibility of similar situation in case of other lipid-soluble hormones is discussed. The perinatal exposition with these “vitamins” can cause faulty perinatal hormonal imprinting with similar consequences as the faulty imprinting by the synthetic endohormones, members of the same hormone family or industrial, communal, or medical endocrine disruptors. The faulty imprinting leads to late (lifelong) consequences with altered hormone binding by receptors, altered sexuality, brain function, immunity, bone development, and fractures, etc. In addition, as hormonal imprinting is an epigenetic process, the effect of a single exposure by fat-soluble vitamins is inherited to the progeny generations. As vitamins are handled differently from hormones; however, perinatal treatments take place frequently and sometimes it is forced, the negative late effect of faulty perinatal vitamin-caused hormonal imprinting must be considered.

Transgenerational effects of childhood conditions on third generation health and education outcomes

This paper examines the extent to which pre-puberty nutritional conditions in one generation affect productivity-related outcomes in later generations. Recent findings from the biological literature suggest that the so-called slow growth period around age 9 is a sensitive period for male germ cell development. We build on this evidence and investigate whether undernutrition at those ages transmits to children and grandchildren. Our findings indicate that third generation males (females) tend to have higher mental health scores if their paternal grandfather (maternal grandmother) was exposed to a famine during the slow growth period. These effects appear to reflect biological responses to adaptive expectations about scarcity in the environment, and as such they can be seen as an economic correctional mechanism in evolution, with marked socio-economic implications for the offspring.

Extending the Developmental Origins of Health and Disease theory: does paternal diet contribute to breast cancer risk in daughters?

The Developmental Origins of Health and Disease (DOHaD) theory focuses on the consequences of periconceptional and in utero exposures. A wide range of environmental conditions during early development are now being investigated as a driving force for epigenetic disruptions that enhance disease risk in later life, including cardiovascular, metabolic, endocrine, and mental disorders and even breast cancer. Most studies involve mother–child dyads, with less focus on environmental influences through the father. Over the last few years, however, new insights have been introduced on paternal effects and the plasticity of the epigenome of developing sperm cells have been proposed to underlie inheritable changes from ancestral exposures. The field is evolving rapidly and study results from animal models are promising. Although caution should be taken in translating animal data to humans, epidemiological findings also suggest a prominent role of the father. Therefore, we here propose an extension to the DOHaD theory to include also paternally inheritable influences.

Obesity: epigenetic regulation – recent observations

Genetic and environmental factors, especially nutrition and lifestyle, have been discussed in the literature for their relevance to epidemic obesity. Gene-environment interactions may need to be understood for an improved understanding of the causes of obesity, and epigenetic mechanisms are of special importance. Consequences of epigenetic mechanisms seem to be particularly important during certain periods of life: prenatal, postnatal and intergenerational, transgenerational inheritance are discussed with relevance to obesity. This review focuses on nutrients, diet and habits influencing intergenerational, transgenerational, prenatal and postnatal epigenetics; on evidence of epigenetic modifiers in adulthood; and on animal models for the study of obesity.

An epigenetic basis for autism spectrum disorder risk and oral contraceptive use

In the United States 1 in 68 children are diagnosed with autism spectrum disorder (ASD). Although the etiology is unknown, many scientists believe ASD is caused by a combination of genetic and environmental factors and/or epigenetic factors. The widespread use of oral contraceptives is one environmental risk factor that has been greatly overlooked in the biomedical literature. Oral contraceptives, synthetic hormones created to imitate natural human hormones and disrupt endogenous endocrine function to inhibit pregnancy, may be causing the harmful neurodevelopmental effects that result in the increased prevalence of ASD. It is conceivable that the synthetic hormones repeatedly assault the oocyte causing persistent changes in expression of the estrogen receptor beta gene. Ethinylestradiol, a known endocrine disruptor, may trigger DNA methylation of the estrogen receptor beta gene causing decreased mRNA resulting in impaired brain estrogen signaling in progeny. In addition, it is possible the deleterious effects are transgenerational as the estrogen receptor gene and many of its targets may be imprinted and the methylation marks protected from global demethylation and preserved through fertilization and beyond to progeny generations. This article will delineate the hypothesis that ethinylestradiol activates DNA methylation of the estrogen receptor beta gene causing decreased mRNA resulting in diminished brain estrogen signaling in offspring of mothers exposed to oral contraceptives. Considering the detrimental epigenetic and transgenerational effects proposed, it calls for further study.

Relationships of maternal and paternal anthropometry with neonatal body size, proportions and adiposity in an Australian cohort

The patterns of association between maternal or paternal and neonatal phenotype may offer insight into how neonatal characteristics are shaped by evolutionary processes, such as conflicting parental interests in fetal investment and obstetric constraints. Paternal interests are theoretically served by maximizing fetal growth, and maternal interests by managing investment in current and future offspring, but whether paternal and maternal influences act on different components of overall size is unknown. We tested whether parents' prepregnancy height and body mass index (BMI) were related to neonatal anthropometry (birthweight, head circumference, absolute and proportional limb segment and trunk lengths, subcutaneous fat) among 1,041 Australian neonates using stepwise linear regression. Maternal and paternal height and maternal BMI were associated with birthweight. Paternal height related to offspring forearm and lower leg lengths, maternal height and BMI to neonatal head circumference, and maternal BMI to offspring adiposity. Principal components analysis identified three components of variability reflecting neonatal “head and trunk skeletal size,” “adiposity,” and “limb lengths.” Regression analyses of the component scores supported the associations of head and trunk size or adiposity with maternal anthropometry, and limb lengths with paternal anthropometry. Our results suggest that while neonatal fatness reflects environmental conditions (maternal physiology), head circumference and limb and trunk lengths show differing associations with parental anthropometry. These patterns may reflect genetics, parental imprinting and environmental influences in a manner consistent with parental conflicts of interest. Paternal height may relate to neonatal limb length as a means of increasing fetal growth without exacerbating the risk of obstetric complications. Am J Phys Anthropol 156:625–636, 2015.

Environmental enrichment mitigates the sex-specific effects of gestational inflammation on social engagement and the hypothalamic pituitary adrenal axis-feedback system

Modest environmental enrichment (EE) is well recognized to protect and rescue the brain from the consequences of a variety of insults. Although animal models of maternal immune activation (MIA) are associated with several neurodevelopmental impairments in both the behavioral and cognitive functioning of offspring, the impact of EE in protecting or reversing these effects has not been fully evaluated. In the present study, female Sprague-Dawley rats were randomized into EE (pair-housed in a large multi-level cage with toys, tubes and ramps) or animal care control (ACC; pair-housed in standard cages) conditions. Each pair was bred, following assignment to their housing condition, and administered 100μg/kg of lipopolysaccharide (LPS) on gestational day 11. After birth, and until the end of the study, offspring were maintained in their respective housing conditions. EE protected against both the social and hypothalamic pituitary adrenal axis consequences of MIA in juvenile male rats, but surprisingly not against the spatial discrimination deficits or accompanying decrease in glutamate levels within the hippocampus (as measured via LCMS-MS). Based on these preliminary results, the mechanisms that underlie the sex-specific consequences that follow MIA appear to be dependent on environmental context. Together, this work highlights the importance of environmental complexity in the prevention of neurodevelopmental deficits following MIA.

Scrutinizing the epigenetics revolution

Epigenetics is one of the most rapidly expanding fields in the life sciences. Its rise is frequently framed as a revolutionary turn that heralds a new epoch both for gene-based epistemology and for the wider discourse on life that pervades knowledge-intensive societies of the molecular age. The fundamentals of this revolution remain however to be scrutinized, and indeed the very contours of what counts as 'epigenetic' are often blurred. This is reflected also in the mounting discourse on the societal implications of epigenetics, in which vast expectations coexist with significant uncertainty about what aspects of this science are most relevant for politics or policy alike. This is therefore a suitable time to reflect on the directions that social theory could most productively take in the scrutiny of this revolution. Here we take this opportunity in both its scholarly and normative dimension, that is, proposing a roadmap for social theorizing on epigenetics that does not shy away from, and indeed hopefully guides, the framing of its most socially relevant outputs. To this end, we start with an epistemological reappraisal of epigenetic discourse that valorizes the blurring of meanings as a critical asset for the field and privileged analytical entry point. We then propose three paths of investigation. The first looks at the structuring elements of controversies and visions around epigenetics. The second probes the mutual constitution between the epigenetic reordering of living phenomena and the normative settlements that orient individual and collective responsibilities. The third highlights the material import of epigenetics and the molecularization of culture that it mediates. We suggest that these complementary strands provide both an epistemically and socially self-reflective framework to advance the study of epigenetics as a molecular juncture between nature and nurture and thus as the new critical frontier in the social studies of the life sciences.

Epigenetics in adaptive evolution and development: the interplay between evolving species and epigenetic mechanisms: extract from Trygve Tollefsbol (ed.) (2011) Handbook of epigenetics--the new molecular and medical genetics. Chapter 26. Amsterdam, USA: Elsevier, pp. 423-446

By comparing epigenetics of current species with fossil records across evolutionary transitions, we can gauge the moment of emergence of some novel mechanisms in evolution, and recognize that epigenetic mechanisms have a bearing on mutation. Understanding the complexity and changeability of these mechanisms, as well as the changes they can effect, is both fascinating and of vital practical benefit. Our most serious pandemics of so-called 'non-communicable' diseases - mental and cardiovascular disorders, obesity and diabetes, rooted in the 'metabolic syndrome' - are evidently related to effects on our evolutionary mechanisms of agricultural and food industrialization, modern lifestyle and diet. Pollution affects us directly as well as indirectly by its destruction of ecologically essential biosystems. Evidently such powerful conditions of existence have epigenetic effects on both our health and our continuing evolution. Such effects are most profound during reproductive and developmental processes, when levels of hormones, as affected by stress particularly, may be due to modern cultures in childbearing such as excessive intervention, separation, maternal distress and disruption of bonding. Mechanisms of genomic imprinting seem likely to throw light on problems in assisted reproductive technology, among other transgenerational effects.

Transgenerational healing: Educating children in genesis of healthy children, with focus on nutrition, emotion, and epigenetic effects on brain development

Although our continuing evolution can never achieve our perfection, we long for our children's birth and health to be near-perfect. Many children are born healthy, though fewer than is possible. Birthing and health rapidly improved generally due to modern housing, sanitation and medicine, as well as birth interventions. Arguably interventions have exceeded the optimal level, without enough regard for natural physical and intuitive resources. Conception, often too easy, receives too little personal preparation unless a couple has problems. Nurturing the health of sperm and ovum seems hard to focus on, yet is needed by both parents - and even by the four grandparents. What are the key factors? Positive: The fields of hormones/emotions and of nutrition/metabolism. Negative: stress, poor nutrition, toxins, diseases; much being due to poverty. Positive and negative both have structural and also epigenetic effects. Interventions, essential or inessential, are seldom without negative side effects. Health can best, and most economically, be generated at the beginning of life, through healthy conception, gestation and birth. Understanding prime needs improves initial health. It also informs therapy of any early-life problems. Healing is therefore more efficient when transgenerational, and much more powerful than individual healing. My vision of healing is safeguarding our evolution in progress. Children's choices - eating, exercise, emotional attitudes and relationships - are already profoundly affecting any children they may have, their mental and physical health. The most practical starting point seems to be educating boys as well as girls. Childhood is therefore the time to educate them in choices. The correction of often unnoticed problems- nutrient deficits, toxins, uro-genital disease - has enabled nearly nine out of ten couples to bear fully healthy babies, even following severe problems - infertility, miscarriages, stillbirths and malformations. Correcting problems before conception prevents both structural faults and wrong setting of gene-switches. Children's habits set. Once courting most are preoccupied and many pregnant unintentionally. Childhood is the time to be adopting a healthy lifestyle, the way to healthy babies The mother's nutritional and emotional status throughout pregnancy continues to affect her child's future physical and mental health, behaviour and ability. Before conception a woman needs to build her appropriate body stores - vitamins and minerals, proteins, docosahexaenoic acid. Before bearing another child, a replenishment time of 3 years is desirable. A return to childbearing in the 20s and early 30s could reduce risks that have risen with the recent shift towards conception by school children and by women in their late 30s or more. Governments, schoolteachers, health professionals, need to adopt this policy of transgenerational health. Empowerment with knowledge is the one way to fend off the growing pandemic of mental ill health and related disorders and to make the most of a nation's genetic potential. Financially there could be no better investment, let alone in enhancing people's lives. Childhood is the most appropriate time for education in this way to generating a healthy, able and peaceful human race. Essential to our amazing genetic systems are the resources of land, sea and air. We are one with our biosphere. We need urgently to follow up the vital work of Developmental Origins of Health and Disease, and of Far East initiatives in sea-bed and sea husbandry.

Adaptive aging in the context of evolutionary theory

Compelling evidence for an adaptive origin of aging has clashed with traditional evolutionary theory based on exclusively individual selection. The consensus view has been to try to understand aging in the context of a narrow, restrictive evolutionary paradigm, called the Modern Synthesis, or neo-Darwinism. But neo-Darwinism has shown itself to be inadequate in other ways, failing to account for stable ecosystems, for the evolution of sex and the maintenance of diversity and the architecture of the genome, which appears to be optimized for evolvability. Thus aging is not the only reason to consider overhauling the standard theoretical framework. Selection for stable ecosystems is rapid and efficient, and so it is the easiest modification of the neo-Darwinian paradigm to understand and to model. Aging may be understood in this context. More profound and more mysterious are the ways in which the process of evolution itself has been transformed in a bootstrapping process of selection for evolvability. Evolving organisms have learned to channel their variation in ways that are likely to enhance their long-term prospects. This is an expanded notion of fitness. Only in this context can the full spectrum of sophisticated adaptations be understood, including aging, sex, diversity, ecological interdependence, and the structure of the genome.

Epigenetics and primary care

Epigenetics, the study of functionally relevant chemical modifications to DNA that do not involve a change in the DNA nucleotide sequence, is at the interface between research and clinical medicine. Research on epigenetic marks, which regulate gene expression independently of the underlying genetic code, has dramatically changed our understanding of the interplay between genes and the environment. This interplay alters human biology and developmental trajectories, and can lead to programmed human disease years after the environmental exposure. In addition, epigenetic marks are potentially heritable. In this article, we discuss the underlying concepts of epigenetics and address its current and potential applicability for primary care providers.

Age-associated epigenetic drift: implications, and a case of epigenetic thrift?

It is now well established that the genomic landscape of DNA methylation (DNAm) gets altered as a function of age, a process we here call ‘epigenetic drift’. The biological, functional, clinical and evolutionary significance of this epigenetic drift, however, remains unclear. We here provide a brief review of epigenetic drift, focusing on the potential implications for ageing, stem cell biology and disease risk prediction. It has been demonstrated that epigenetic drift affects most of the genome, suggesting a global deregulation of DNAm patterns with age. A component of this drift is tissue-specific, allowing remarkably accurate age-predictive models to be constructed. Another component is tissue-independent, targeting stem cell differentiation pathways and affecting stem cells, which may explain the observed decline of stem cell function with age. Age-associated increases in DNAm target developmental genes, overlapping those associated with environmental disease risk factors and with disease itself, notably cancer. In particular, cancers and precursor cancer lesions exhibit aggravated age DNAm signatures. Epigenetic drift is also influenced by genetic factors. Thus, drift emerges as a promising biomarker for premature or biological ageing, and could potentially be used in geriatrics for disease risk prediction. Finally, we propose, in the context of human evolution, that epigenetic drift may represent a case of epigenetic thrift, or bet-hedging. In summary, this review demonstrates the growing importance of the ‘ageing epigenome’, with potentially far-reaching implications for understanding the effect of age on stem cell function and differentiation, as well as for disease prevention.

Transgenerational epigenetic inheritance: how important is it?

Much attention has been given to the idea of transgenerational epigenetic inheritance, but fundamental questions remain regarding how much takes place and the impact that this might have on organisms. We asked five leading researchers in this area--working on a range of model organisms and in human disease--for their views on these topics. Their responses highlight the mixture of excitement and caution that surrounds transgenerational epigenetic inheritance and the wide gulf between species in terms of our knowledge of the mechanisms that may be involved.

Intergenerational health responses to adverse and enriched environments

Health consequences of relative or absolute poverty constitute a definitive area of study in social medicine. As demonstrated in the extreme example of the Dutch Hunger Winter from 1944 to 1945, prenatal hunger can lead to adult schizophrenia and depression. A Norwegian study showed how childhood poverty resulted in a heightened risk of myocardial infarction in adulthood. In England, a study of extended impaired prenatal nutrition indicated three different types of increased cardiovascular risk at older ages. Current animal and human studies link both adverse and enriched environmental exposures to intergenerational transmission. We do not fully understand the molecular mechanisms for it; however, studies that follow up epigenetic marks within a generation combined with exploration of gametic epigenetic inheritance may help explain the prevalence of certain conditions such as cardiovascular disease, schizophrenia, and alcoholism, which have complex etiologies. Insights from these studies will be of great public health importance.

Lower birth weight and diet in Taiwanese girls more than boys predicts learning impediments

Possible links between lower birth weight, childhood diet, and learning in Taiwan are evaluated. The population representative Elementary School Children's Nutrition and Health Survey in Taiwan 2001-2002 and the national birth registry were used to examine school and social performance using the modified Scale for Assessing Emotional Disturbance questionnaires in relation to diet quality by the Youth Healthy Eating Index-Taiwan and birth weight of children aged 6-13 years (n=2283). Lower birth weight (≤15th percentile: ≤2850 g for boys and ≤2700 g for girls) children were mostly from mountainous areas and of indigenous descent. Compared to normal birth weight, lower birth weight girls experienced greater inability to learn and weaker overall competence. Better diet quality predicted more favorable emotional and behavioral outcomes in lower birth weight girls, and this persisted with adjustment for covariates. None of these findings were evident among boys. Girls' cognitive and social development appears to be susceptible to diet quality and birth weight, such that the adverse risk of lower birth weight on school performance may be offset by improved diet.

Advantages of stress process approaches for measuring historical trauma

Despite growing attention to historical trauma (HT) as a key mechanism for documented Indigenous health disparities like alcohol abuse, the complexities of conceptualizing and measuring HT-related constructs have limited empirical tests of these relationships. In this article, we review the current evidence surrounding one HT measure: the Historical Loss Scale. In addition, we provide examples of the benefits of treating historical cultural losses as stressors within sociological and Indigenous stress process models of health.

Complex interactions between paternal and maternal effects: parental experience and age at reproduction affect fecundity and offspring performance in a butterfly

Parental effects can greatly affect offspring performance and are thus expected to impact population dynamics and evolutionary trajectories. Most studies have focused on maternal effects, whereas fathers are also likely to influence offspring phenotype, for instance when males transfer nutrients to females during mating. Moreover, although the separate effects of maternal age and the environment have been documented as a source of parental effects in many species, their combined effects have not been investigated. In the present study, we analyzed the combined effects of maternal and paternal age at reproduction and a mobility treatment in stressful conditions on offspring performance in the butterfly Pieris brassicae. Both paternal and maternal effects affected progeny traits but always via interactions between age and mobility treatment. Moreover, parental effects shifted from male effects expressed at the larval stage to maternal effects at the adult stage. Indeed, egg survival until adult emergence significantly decreased with father age at mating only for fathers having experienced the mobility treatment, whereas offspring adult life span decreased with increasing mother age at laying only for females that did not experience the mobility treatment. Overall, our results demonstrate that both parents' phenotypes influence offspring performance through nongenetic effects, their relative contribution varying over the course of progeny's life.

Assisted reproduction treatment and epigenetic inheritance

BACKGROUND

The subject of epigenetic risk of assisted reproduction treatment (ART), initiated by reports on an increase of children with the Beckwith–Wiedemann imprinting disorder, is very topical. Hence, there is a growing literature, including mouse studies.

METHODS

In order to gain information on transgenerational epigenetic inheritance and epigenetic effects induced by ART, literature databases were searched for papers on this topic using relevant keywords.

RESULTS

At the level of genomic imprinting involving CpG methylation, ART-induced epigenetic defects are convincingly observed in mice, especially for placenta, and seem more frequent than in humans. Data generally provide a warning as to the use of ovulation induction and in vitro culture. In human sperm from compromised spermatogenesis, sequence-specific DNA hypomethylation is observed repeatedly. Transmittance of sperm and oocyte DNA methylation defects is possible but, as deduced from the limited data available, largely prevented by selection of gametes for ART and/or non-viability of the resulting embryos. Some evidence indicates that subfertility itself is a risk factor for imprinting diseases. As in mouse, physiological effects from ART are observed in humans.

In the human, indications for a broader target for changes in CpG methylation than imprinted DNA sequences alone have been found. In the mouse, a broader range of CpG sequences has not yet been studied. Also, a multigeneration study of systematic ART on epigenetic parameters is lacking.

CONCLUSIONS

The field of epigenetic inheritance within the lifespan of an individual and between generations (via mitosis and meiosis, respectively) is growing, driven by the expansion of chromatin research. ART can induce epigenetic variation that might be transmitted to the next generation.

BORIS in human cancers -- a review

Brother of the regulator of the imprinted site (BORIS) or CTCFL is an 11 zinc finger (ZF) protein, which is considered to be a new oncogene. It is a paralogue of CCCTC-binding factor (CTCF), generated by a duplication event. BORIS is highly expressed in primary spermatocytes, although it is silenced at later stages of spermatogenesis. BORIS has either not been found in normal human tissues or cells or has been detected at very low levels. The expression of the BORIS gene is predominantly controlled by DNA-methylation, while its activation requires the demethylation of its promoter. Re-expression of BORIS in cancers is due to the hypomethylation of its promoter. High expression of BORIS protein and RNA correlates with the tumour size and grade in cancer patients. High percentages of BORIS transcripts were detected in breast, endometrial, prostatic and colon cancer patients. Lower percentages of BORIS were found in patients with melanoma and cancers of the head and neck. The expression of BORIS varied from low to high in lung, colon and ovarian cancer, melanoma and leukaemic cell lines. Lower expressions of BORIS were found in head and neck, breast, kidney, bladder, testicular and prostate carcinoma cell lines. An inhibitor of DNA methylation, 5-aza-2'deoxy-cytidine (5-azadC), and histone deacetylase inhibitors induced or enhanced the expression of BORIS in various carcinoma cell lines. The silencing of BORIS induced apoptosis in tumorous cell lines. BORIS antitumor vaccines have been tested in mice with several cancers, based on the deletion of the DNA-binding ZF-region of the BORIS.

The biological basis and clinical significance of hormonal imprinting, an epigenetic process

The biological phenomenon, hormonal imprinting, was named and defined by us (Biol Rev, 1980, 55, 47-63) 30 years ago, after many experimental works and observations. Later, similar phenomena were also named to epigenetic imprinting or metabolic imprinting. In the case of hormonal imprinting, the first encounter between a hormone and its developing target cell receptor-usually at the perinatal period-determines the normal receptor-hormone connection for life. However, in this period, molecules similar to the target hormone (members of the same hormone family, synthetic drugs, environmental pollutants, etc), which are also able to bind to the receptor, provoke faulty imprinting also with lifelong-receptorial, behavioral, etc.,-consequences. Faulty hormonal imprinting could also be provoked later in life in continuously dividing cells and in the brain. Faulty hormonal imprinting is a disturbance of gene methylation pattern, which is epigenenetically inherited to the further generations (transgenerational imprinting). The absence of the normal or the presence of false hormonal imprinting predispose to or manifested in different diseases (e.g., malignant tumors, metabolic syndrome) long after the time of imprinting or in the progenies.

Food as exposure: Nutritional epigenetics and the new metabolism

Nutritional epigenetics seeks to explain the effects of nutrition on gene expression. For social science, it is an area of life science whose analysis reveals a concentrated form of a wider shift in the understanding of food and metabolism. Rather than the chemical conversion of food to energy and body matter of classic metabolism, food is now also a conditioning environment that shapes the activity of the genome and the physiology of the body. It is thought that food in prenatal and early postnatal life impacts adult-onset diseases such as diabetes and heart disease; exposure to food is seen as a point of potential intervention in long-term health of individuals and populations. This article analyzes how food has become environment in nutritional epigenetics, with a focus on the experimental formalization of food. The experimental image of human life generated in rodent models, it is argued, generates concepts of food as a form of molecular exposure. This scientific discourse has profound implications for how food is perceived, manufactured and regulated, as well as for social theories and analyses of the social body that have a long history of imbrication with scientific models of metabolism.

Genetics of tardive dyskinesia

Tardive dyskinesia (TD) is one of the most serious adverse side effects of antipsychotic drugs and is an important topic of pharmacogenetic studies. Since there is a genetic susceptibility for developing this adverse reaction, and given that it is hard to predict its development prior to or during the early period of medication, the genetic study of TD is a promising research topic that has a direct clinical application. Moreover, such studies would improve our understanding of the genetic mechanism(s) underlying abnormal dyskinetic movement. A substantial number of case-control association studies of TD have been performed, with numbers of studies focusing on the genes involved in antipsychotic drug metabolism, such as those for cytochrome P450 (CYP) and oxidative stress related genes as well as various neurotransmitter related genes. These studies have produced relatively consistent though controversial findings for certain polymorphisms such as CYP2D6*10, DRD2 Taq1A, DRD3 Ser9Gly, HTR2A T102C, and MnSOD Ala9Val. Moreover, the application of the genome-wide association study (GWAS) to the susceptibility of TD has revealed certain associated genes that previously were never considered to be associated with TD, such as the rs7669317 on 4q24, GLI2 gene, GABA pathway genes, and HSPG2 gene. Although a substantial number of genetic studies have investigated TD, many of the positive findings have not been replicated or are inconsistent, which could be due to differences in study design, sample size, and/or subject ethnicity. We expect that more refined research will be performed in the future to resolve these issues, which will then enable the genetic prediction of TD and clinical application thereof.

[Hormonal imprinting--the unforeseeable future]

Hormonal imprinting takes place at the first encounter between the developing receptor and the target hormone, perinatally, causing life-long changes in the binding capacity of the receptor and the indexes influenced by it. Perinatal hormonal imprinting is absolutely needed for the maturation of receptor, however, at the same time, molecules similar to the target hormone (related hormones, synthetic drugs acting at receptor level, chemicals, environmental pollutants etc.) can cause faulty imprinting, also with (morphological, biochemical, receptorial, behavioral) consequences for life. Although imprinting is characteristic and inevitable perinatally, it can be provoked in any period of life in developing cells, especially at the weanling and adolescent age (late imprinting). There is no gene mutation during imprinting, however, the methylation pattern of the genes changes and that inherits epigenetically the imprinting, which is manifested in disposition to diseases or in diseases (e.g. tumor formation, metabolic syndrome). Imprinting is inherited between generations that could cause--in the present chemical world--evolutionary consequences. Thus, medicaments or preventive drugs, e.g. pregnancy protecting drugs or oral contraceptive pills should be given cautiously, especially in the critical periods, considering that consequences are manifested always after a long period (sometimes decades) or in the next generations.

Review and hypothesis: syndromes with severe intrauterine growth restriction and very short stature--are they related to the epigenetic mechanism(s) of fetal survival involved in the developmental origins of adult health and disease?

Diagnosing the specific type of severe intrauterine growth restriction (IUGR) that also has post-birth growth restriction is often difficult. Eight relatively common syndromes are discussed identifying their unique distinguishing features, overlapping features, and those features common to all eight syndromes. Many of these signs take a few years to develop and the lifetime natural history of the disorders has not yet been completely clarified. The theory behind developmental origins of adult health and disease suggests that there are mammalian epigenetic fetal survival mechanisms that downregulate fetal growth, both in order for the fetus to survive until birth and to prepare it for a restricted extra-uterine environment, and that these mechanisms have long lasting effects on the adult health of the individual. Silver-Russell syndrome phenotype has recently been recognized to be related to imprinting/methylation defects. Perhaps all eight syndromes, including those with single gene mutation origin, involve the mammalian mechanism(s) of fetal survival downsizing. Insights into those mechanisms should provide avenues to understanding the natural history, the heterogeneity and possible therapy not only for these eight syndromes, but for the common adult diseases with which IUGR is associated.

Gene expression in the placenta: maternal stress and epigenetic responses

Successful placental development is crucial for optimal growth, development, maturation and survival of the embryo/fetus into adulthood. Numerous epidemiologic and experimental studies have demonstrated the profound influence of intrauterine environment on life, and the diseases to which one is subject as an adult. For the most part, these invidious influences, whether maternal hypoxia, protein or caloric deficiency or excess, and others, represent types of maternal stress. In the present review, we examine certain aspects of gene expression in the placenta as a consequence of maternal stressors. To examine these issues in a controlled manner, and in a species in which the genome has been sequenced, most of these reported studies have been performed in the mouse. Although each individual maternal stress is characterized by up- or down-regulation of specific genes in the placenta, functional analysis reveals some patterns of gene expression common to the several forms of stress. Of critical importance, these genes include those involved in DNA methylation and histone modification, cell cycle regulation, and related global pathways of great relevance to epigenesis and the developmental origins of adult health and disease.

The importance of a genetic component in longitudinal birth cohorts

The risks of most common health and developmental outcomes are contributed to by a combination of genetic and environmental factors. Understanding of ways in which genes influence such outcomes, and especially of how their interaction with environmental factors affects health and development should lead to the identification of causal pathways and thence appropriate intervention strategies.

Epigenetic mechanisms for nutrition determinants of later health outcomes

Epigenetic marking on genes can determine whether or not genes are expressed. Epigenetic regulation is mediated by the addition of methyl groups to DNA cytosine bases, of methyl and acetyl groups to proteins (histones) around which DNA is wrapped, and by small interfering RNA molecules. Some components of epigenetic regulation have evolved to permit control of whether maternal or paternal genes are expressed. The epigenetic imprinting of IGF2 expression is an example of maternal and paternal epigenetic marking that modulates fetal growth and fetal size. However, epigenetic regulation also permits the fetus and the infant to adapt gene expression to the environment in which it is growing; sometimes when this adjustment goes awry, the risk of chronic disease is increased. Recent progress in the understanding of nutritional influences on epigenetics suggests that nutrients that are part of methyl-group metabolism can significantly influence epigenetics. During critical periods in development, dietary methyl-group intake (choline, methionine, and folate) can alter DNA and histone methylation, which results in lifelong changes in gene expression. In rodent models, pregnant dams that were fed diets high in methionine, folic acid, and choline produced offspring with different coat colors or with kinked tails. A number of syndromes in humans can be caused by defective epigenetic regulation, including Rett syndrome. There are interesting examples of the effects of nutrition in early life that result in altered health in adults, and some of these could be the result of altered epigenetic regulation of gene expression.

Epigenetics and obesity

Common DNA sequence variants inadequately explain variability in fat mass among individuals. Abnormal body weights are characteristic of specific imprinted-gene disorders. However, the relevance of imprinted genes to our understanding of obesity among the general population is uncertain. Hitherto unidentified imprinted genes and epigenetic mosaicism are two of the challenges for this emerging field of epigenetics. Subtle epigenetic differences in imprinted genes and gene networks are likely to be present among cells, tissues and individuals. In order to advance obesity research it will be necessary to use genome-wide, next-generation sequencing approaches that allow the detection of such epigenetic differences.

Perinatal caffeine, acting on maternal adenosine A(1) receptors, causes long-lasting behavioral changes in mouse offspring

BACKGROUND

There are lingering concerns about caffeine consumption during pregnancy or the early postnatal period, partly because there may be long-lasting behavioral changes after caffeine exposure early in life.

METHODOLOGY/PRINCIPAL FINDINGS

We show that pregnant wild type (WT) mice given modest doses of caffeine (0.3 g/l in drinking water) gave birth to offspring that as adults exhibited increased locomotor activity in an open field. The offspring also responded to cocaine challenge with greater locomotor activity than mice not perinatally exposed to caffeine. We performed the same behavioral experiments on mice heterozygous for adenosine A(1) receptor gene (A(1)RHz). In these mice signaling via adenosine A(1) receptors is reduced to about the same degree as after modest consumption of caffeine. A(1)RHz mice had a behavioral profile similar to WT mice perinatally exposed to caffeine. Furthermore, it appeared that the mother's genotype, not offspring's, was critical for behavioral changes in adult offspring. Thus, if the mother partially lacked A(1) receptors the offspring displayed more hyperactivity and responded more strongly to cocaine stimulation as adults than did mice of a WT mother, regardless of their genotype. This indicates that long-term behavioral alterations in the offspring result from the maternal effect of caffeine, and not a direct effect on fetus. WT offspring from WT mother but having a A(1)R Hz grandmother preserved higher locomotor response to cocaine.

CONCLUSIONS/SIGNIFICANCE

We suggest that perinatal caffeine, by acting on adenosine A(1) receptors in the mother, causes long-lasting behavioral changes in the offspring that even manifest themselves in the second generation.

From human genetics and genomics to pharmacogenetics and pharmacogenomics: past lessons, future directions

A brief history of human genetics and genomics is provided, comparing recent progress in those fields with that in pharmacogenetics and pharmacogenomics, which are subsets of genetics and genomics, respectively. Sequencing of the entire human genome, the mapping of common haplotypes of single-nucleotide polymorphisms (SNPs), and cost-effective genotyping technologies leading to genome-wide association (GWA) studies - have combined convincingly in the past several years to demonstrate the requirements needed to separate true associations from the plethora of false positives. While research in human genetics has moved from monogenic to oligogenic to complex diseases, its pharmacogenetics branch has followed, usually a few years behind. The continuous discoveries, even today, of new surprises about our genome cause us to question reviews declaring that "personalized medicine is almost here" or that "individualized drug therapy will soon be a reality." As summarized herein, numerous reasons exist to show that an "unequivocal genotype" or even an "unequivocal phenotype" is virtually impossible to achieve in current limited-size studies of human populations. This problem (of insufficiently stringent criteria) leads to a decrease in statistical power and, consequently, equivocal interpretation of most genotype-phenotype association studies. It remains unclear whether personalized medicine or individualized drug therapy will ever be achievable by means of DNA testing alone.

The contribution of parental and grandparental childhood social disadvantage to circulatory disease diagnosis in young Swedish men

Men born out of wedlock in early twentieth century Sweden who never married have previously been shown to have a doubled mortality risk from ischaemic heart disease compared to the corresponding group of men born to married parents. This study further explores the question of childhood social disadvantage and its long-term consequences for cardiovascular health by examining the two subsequent generations. The question posed is whether the sons and grandsons of men and women born out of wedlock in early twentieth century Sweden have an increased risk of circulatory disease compared with the corresponding descendants of those born inside marriage. We examined this by use of military conscription data. The material used is the Uppsala Birth Cohort Multigenerational database consisting of individuals born at Uppsala University Hospital between 1915 and 1929 (UG1), their children (UG2) and grandchildren (UG3). Conscription data were available for UG2s born between 1950 and 1982 (n=5,231) and UG3s born between 1953 and 1985 (n=10,074) corresponding to 72.1% and 73.6%, respectively, of all males born in each time-period. Logistic regression showed that significant excess risk of circulatory disease diagnoses was present only among descendants of men born outside marriage, with sons and grandsons demonstrating odds ratios of 1.64 and 1.83, respectively, when BMI and height at the time of conscription, father's social class in mid-life and father's or grandfather's history of circulatory disease had been adjusted for. Separate analyses showed that the effect of the maternal and paternal grandfather was of approximately the same magnitude. Further analyses revealed an interaction between the father's social class and the grandfather's legitimacy status at birth on UG3-men's likelihood of having a circulatory disease, with elevated odds only among those whose fathers were either manual workers or self-employed. The results of this study suggest that social disadvantage in one generation can be linked to health disadvantage in the subsequent two generations.

Flaws in the theory of predictive adaptive responses

Human foetuses have been proposed to make 'predictive adaptive responses' during pregnancy, to adapt metabolic profile in anticipation of conditions expected in adulthood. Predictive adaptive responses are invoked in particular to explain associations between early-life experience and risk of the metabolic syndrome, although the concept is problematic on theoretical grounds and fits poorly with empirical data. In ecosystems, as in economics, the future cannot be predicted with confidence. It is likely to be the case that human offspring look not to the future but back to the past, and align their developmental trajectory with maternal phenotype, the key factor in determining their nutritional supply. This debate has important implications, potentially offering a robust theoretical basis for designing public health interventions and guiding the nutritional management of individual infants.

Nutrigenomics and metabolomics will change clinical nutrition and public health practice: insights from studies on dietary requirements for choline

Science is beginning to understand how genetic variation and epigenetic events alter requirements for, and responses to, nutrients (nutrigenomics). At the same time, methods for profiling almost all of the products of metabolism in a single sample of blood or urine are being developed (metabolomics). Relations between diet and nutrigenomic and metabolomic profiles and between those profiles and health have become important components of research that could change clinical practice in nutrition. Most nutrition studies assume that all persons have average dietary requirements, and the studies often do not plan for a large subset of subjects who differ in requirements for a nutrient. Large variances in responses that occur when such a population exists can result in statistical analyses that argue for a null effect. If nutrition studies could better identify responders and differentiate them from nonresponders on the basis of nutrigenomic or metabolomic profiles, the sensitivity to detect differences between groups could be greatly increased, and the resulting dietary recommendations could be appropriately targeted. It is not certain that nutrition will be the clinical specialty primarily responsible for nutrigenomics or metabolomics, because other disciplines currently dominate the development of portions of these fields. However, nutrition scientists' depth of understanding of human metabolism can be used to establish a role in the research and clinical programs that will arise from nutrigenomic and metabolomic profiling. Investments made today in training programs and in research methods could ensure a new foundation for clinical nutrition in the future.

Diet-induced hypermethylation at agouti viable yellow is not inherited transgenerationally through the female

The effects of nonmutagenic environmental exposures can sometimes be transmitted for several generations, suggesting transgenerational inheritance of induced epigenetic variation. Methyl donor supplementation of female mice during pregnancy induces CpG hypermethylation at the agouti viable yellow (A(vy)) allele in A(vy)/a offspring. Epigenetic inheritance occurs at A(vy); when passed through the female germ line, A(vy) epigenotype is not completely "reset." We therefore tested whether diet-induced epigenetic alterations at A(vy) are inherited transgenerationally. Female A(vy)/a mice were weaned onto either control (n=6) or a methyl-supplemented diet (n=5). These F0 dams were mated with a/a males. All F1 and F2 A(vy)/a females were weaned onto the same diet as their mothers, then mated with a/a males. F1, F2, and F3 A(vy)/a offspring were classified for coat color, an indicator of A(vy) methylation. In total, 62 F1, 98 F2, and 209 F3 A(vy)/a mice were studied. As expected, average A(vy)/a coat color was darker in the supplemented group (P<0.01). However, there was no cumulative effect of supplementation across successive generations. These results suggest that, in the female germ line, diet-induced A(vy) hypermethylation occurs in the absence of additional epigenetic modifications that normally confer transgenerational epigenetic inheritance at the locus.

Non-genomic transgenerational inheritance of disease risk

That there is a heritable or familial component of susceptibility to chronic non-communicable diseases such as type 2 diabetes, obesity and cardiovascular disease is well established, but there is increasing evidence that some elements of such heritability are transmitted non-genomically and that the processes whereby environmental influences act during early development to shape disease risk in later life can have effects beyond a single generation. Such heritability may operate through epigenetic mechanisms involving regulation of either imprinted or non-imprinted genes but also through broader mechanisms related to parental physiology or behaviour. We review evidence and potential mechanisms for non-genomic transgenerational inheritance of 'lifestyle' disease and propose that the 'developmental origins of disease' phenomenon is a maladaptive consequence of an ancestral mechanism of developmental plasticity that may have had adaptive value in the evolution of generalist species such as Homo sapiens.

DEVELOPMENTAL PROGRAMMING OF OBESITY AND TYPE 2 DIABETES

Obesity and type 2 diabetes are serious health issues in the developed world and are becoming increasingly important on a global scale. Furthermore, the marked increases in both childhood obesity and type 2 diabetes will translate to further increases in adult obesity, diabetes and associated co-morbidities in the near future; as such it has been ranked as a critical public health threat. It is a widely held view that the primary cause of obesity is the development of an obesogenic environment, due to ease of access to highly calorific food and reduced energy expenditure in work and leisure activities. In addition there is strong evidence for a genetic component to human obesity with the identification of a number of genes associated with human obesity. However, on its own the genetic component of this condition cannot account for the dramatic increase in the prevalence of obesity in recent years. Of relevance and as highlighted by epidemiological and experimental studies, is the relationship between the periconceptual, fetal and early infant phases of life and the subsequent development of adult obesity. The terms “developmental programming” and the “Developmental Origins of Adult Health and Disease” are preferentially used to describe these relationships. Despite initial controversy when these relationships were first suggested, both prospective clinical and experimental studies have clearly shown that the propensity to develop abnormalities of cardiovascular, endocrine and metabolic homeostasis in adulthood are increased when fetal development has been adversely affected. This pathogenesis is not based on genetic defects but on altered gene expression seen as a result of fetal adaptation to an adverse intrauterine environment. The relative role of genetic versus environmental factors and the mechanisms underlying developmental programming remain speculative. It is generally argued that in response to an adverse intrauterine environment, the fetus adapts its physiological development to maximise its immediate chances for survival. Owing to the plasticity of the fetus, these adaptations may include resetting of metabolic homeostasis and endocrine systems and the down-regulation of growth, commonly reflected in an altered birth phenotype. It is thought that whilst these changes in fetal physiology (i.e. the prenatal environment) may be beneficial for short term survivalin uterothey may be maladaptive in postnatal life, contributing to poor health outcomes when offspring are exposed to catch-up growth, diet-induced obesity and other factors. The “predictive adaptive response” hypothesis proposes that the degree of mismatch between the pre- and postnatal environments is a major determinant of subsequent disease. This review will address recent work in animal models and observations in the clinical and epidemiological settings onin uteroadaptations and subsequent development of obesity and type 2 diabetes.

Sex-specific, male-line transgenerational responses in humans

Transgenerational effects of maternal nutrition or other environmental 'exposures' are well recognised, but the possibility of exposure in the male influencing development and health in the next generation(s) is rarely considered. However, historical associations of longevity with paternal ancestors' food supply in the slow growth period (SGP) in mid childhood have been reported. Using the Avon Longitudinal Study of Parents and Children (ALSPAC), we identified 166 fathers who reported starting smoking before age 11 years and compared the growth of their offspring with those with a later paternal onset of smoking, after correcting for confounders. We analysed food supply effects on offspring and grandchild mortality risk ratios (RR) using 303 probands and their 1818 parents and grandparents from the 1890, 1905 and 1920 Overkalix cohorts, northern Sweden. After appropriate adjustment, early paternal smoking is associated with greater body mass index (BMI) at 9 years in sons, but not daughters. Sex-specific effects were also shown in the Overkalix data; paternal grandfather's food supply was only linked to the mortality RR of grandsons, while paternal grandmother's food supply was only associated with the granddaughters' mortality RR. These transgenerational effects were observed with exposure during the SGP (both grandparents) or fetal/infant life (grandmothers) but not during either grandparent's puberty. We conclude that sex-specific, male-line transgenerational responses exist in humans and hypothesise that these transmissions are mediated by the sex chromosomes, X and Y. Such responses add an entirely new dimension to the study of gene-environment interactions in development and health.

Environmental and nutritional effects on the epigenetic regulation of genes

Major efforts have been directed towards the identification of genetic mutations, their use as biomarkers, and the understanding of their consequences on human health and well-being. There is an emerging interest, however, in the possibility that environmentally-induced changes at levels other than the genetic information could have long-lasting consequences as well. This review summarises our current knowledge of how the environment, nutrition, and ageing affect the way mammalian genes are organised and transcribed, without changes in the underlying DNA sequence. Admittedly, the link between environment and epigenetics remains largely to be explored. However, recent studies indicate that environmental factors and diet can perturb the way genes are controlled by DNA methylation and covalent histone modifications. Unexpectedly, and not unlike genetic mutations, aberrant epigenetic alterations and their phenotypic effects can sometimes be passed on to the next generation.

Epigenetics and phenotypic variation in mammals

What causes phenotypic variation? By now it is clear that phenotype is a result of the interaction between genotype and environment, in addition to variation not readily attributable to either. Epigenetic phenomena associated with phenotypic variation at the biochemical, cellular, tissue, and organism level are now well recognized and are likely to contribute to the "intangible variation" alluded to. While it is clear that epigenetic modifications are mitotically heritable, the fidelity of this process is not well understood. Inheritance through more than one generation of meioses is even less well studied. So it remains unclear to what extent epigenetic changes contribute to phenotypic variation in natural populations. How might such evidence be obtained? What are the features of phenotypes that might suggest an epigenetic component? How much of the epigenetic component is truly independent of genetic changes? The answers to such questions must come from studies designed specifically to detect subtle, stochastically determined phenotypic variation in suitable animal models.