A quiet revolution in genetics is increasingly rendering our milieu strange and artificial. Epigenomics, informatic cousin of epigenetics, is a xenoforming process, giving birth to an alien milieu, replacing the natural with the technical. If epigenetics is understood as the heritable changes in gene expression that do not alter DNA sequence, epigenomics takes as object the set of epigenetic modifications. Environmental, social, even political aspects of life’s variability are re-understood digitally in epigenomic profiles, the previous categories computationally accounted (...) for as potential triggers of epigenesis. Following Gilbert Simondon, the xenoforming procedures of epigenomics can be understood as the concretization and adaptation processes of a technical object, the invention of which gives birth to a technogeographic milieu. In this article, the author examines Simondon’s work, especially, ‘On the Mode of Existence of Technical Objects’, alongside contemporary scholarship on epigenetics. (shrink)

Targeted modifications of the human epigenome, epigenome editing (EE), are around the corner. For EE, techniques similar to genome editing (GE) techniques are used. While in GE the genetic information is changed by directly modifying DNA, intervening in the epigenome requires modifying the configuration of DNA, for example, how it is folded. This does not come with alterations in the base sequence (‘genetic code’). To date, there is almost no ethical debate about EE, whereas the discussions about GE are voluminous. (...) Our article introduces EE into bioethics by translating knowledge from science to ethics and by comparing the risks of EE with those of GE. We, first (I), make the case that a broader ethical debate on EE is due, provide scientific background on EE, compile potential use-cases and recap previous debates. We then (II) compare EE and GE and suggest that the severity of risks of novel gene technologies depends on three factors: (i) the choice of an ex vivo versus an in vivo editing approach, (ii) the time of intervention and intervention windows and (iii) the targeted diseases. Moreover, we show why germline EE is not effective and reject the position of strong epigenetic determinism. We conclude that EE is not always ethically preferable to GE in terms of risks, and end with suggestions for next steps in the current ethical debate on EE by briefly introducing ethical challenges of new areas of preventive applications of EE (III). (shrink)

The information contained within the linear sequence of bases (the genome) must be faithfully replicated in each cell cycle, with a balance of constancy and variation taking place over the course of evolution. Recently, it has become clear that additional information important for genetic regulation is contained within the chromatin proteins associated with DNA (the epigenome). Epigenetic information also must be faithfully duplicated in each cell cycle, with a balance of constancy and variation taking place during the course of development (...) to achieve differentiation while maintaining identity within cell lineages. Both the genome and the epigenome are synthesized at the replication fork, so the events occurring during S‐phase provide a critical window of opportunity for eliciting change or maintaining existing genetic states. Cells discriminate between different states of chromatin through the activities of proteins that selectively modify the structure of chromatin. Several recent studies report the localization of certain chromatin modifying proteins to replication forks at specific times during S‐phase. Since transcriptionally active and inactive chromosome domains generally replicate at different times during S‐phase, this spatiotemporal regulation of chromatin assembly proteins may be an integral part of epigenetic inheritance. BioEssays 25:647–656, 2003. © 2003 Wiley Periodicals, Inc. (shrink)

During mammalian development, maintenance of cell fate through mitotic divisions require faithful replication not only of the DNA but also of a particular epigenetic state. Germline cells have the capacity of erasing this epigenetic memory at crucial times during development, thereby resetting their epigenome. Certain marks, however, appear to escape this reprogramming, which allows their transmission to the offspring and potentially guarantees transgenerational epigenetic inheritance. Here we discuss the molecular requirements for faithful transmission of epigenetic information and our current knowledge (...) about the transmission of epigenetic information through generations. (shrink)

This chapter examines non-genetic, psychophysiological inheritance across generational lines in the context of white domination. Focusing on the effects of racism in black bodies, this chapter draws on the field of epigenetics to show how people of color can biologically inherit the deleterious effects of racism. Examining disparities in preterm birth rates between African American and white women, Chapter 3 details how transgenerational racial health disparities are in fact racist health disparities that can be manifest physiologically, helping constitute the chemicals, (...) hormones, cells, and fibers of the human body. Epigenetics helps demonstrate how racism can have durable effects on the biological constitution of human beings that are not limited to the specific person who is the target of racism, but instead extend to that person’s children and grandchildren. In this way, the field of epigenetics can help philosophers and others understand the transgenerational biological impact of social forces such as racism. (shrink)

In this article, I explore the ethical dimensions of same-sex reproduction achieved through epigenome editing—an innovative and transformative technique. For the first time, I analyse the potential normativity of this disruptive approach for reproductive purposes, focusing on its implications for lesbian couples seeking genetically related offspring. Epigenome editing offers a compelling solution to the complex ethical challenges posed by traditional gene editing, as it sidesteps genome modifications and potential long-term genetic consequences. The focus of this article is to systematically analyse (...) the bioethical issues related to the use of epigenome editing for same-sex reproduction. I critically assess the ethical acceptability of epigenome editing with reproductive purposes from multiple angles, considering harm perspectives, the comparison of ethical issues related to gene and epigenome editing, and feminist theories. This analysis reveals that epigenome editing emerges as an ethically acceptable means for lesbian couples to have genetically related children. Moreover, the experiments of a reproductive use of epigenome editing discussed in this article transcend bioethics, shedding light on the broader societal implications of same-sex reproduction. It challenges established notions of biological reproduction and prompts a reevaluation of how we define the human embryo, while poses some issues in the context of gender self-identification and family structures. In a world that increasingly values inclusivity and diversity, this article aims to reveal a progressive pathway for reproductive medicine and bioethics, as well as underscores the need for further philosophical research in this emerging and fertile domain. (shrink)

The “Encyclopedia of DNA Elements” (ENCODE) project was launched by the US National Human Genome Research Institute in the aftermath of the Human Genome Project (HGP). It aimed to systematically map the human transcriptome, and held the promise that identifying potential regulatory regions and transcription factor binding sites would help address some of the perplexing results of the HGP. Its initial results published in 2012 produced a flurry of high-impact publications as well as criticisms. Here we put the results of (...) ENCODE and the work on epigenomics that followed in a broad theoretical and historical context, focusing on three strands of research. The first is the history of thinking about the organization of genomes, both physical and regulatory. The second is the history of ideas about gene regulation, primarily in eukaryotes. Finally, and connecting these two issues, we suggest how to think about the role of genetic material in physiology and development. (shrink)

Volume 20, Issue 8, August 2020, Page 32-36.

X chromosome inactivation (XCI) is an essential epigenetic process that ensures X‐linked gene dosage equilibrium between sexes in mammals. XCI is dynamically regulated during development in a manner that is intimately linked to differentiation. Numerous studies, which we review here, have explored the dynamics of X inactivation and reactivation in the context of development, differentiation and diseases, and the phenotypic and molecular link between the inactive status, and the cellular context. Here, we also assess whether XCI is a uniform mechanism (...) in mammals by analyzing epigenetic signatures of the inactive X (Xi) in different species and cellular contexts. It appears that the timing of XCI and the epigenetic signature of the inactive X greatly vary between species. Surprisingly, even within a given species, various Xi configurations are found across cellular states. We discuss possible mechanisms underlying these variations, and how they might influence the fate of the Xi. (shrink)

New DNA sequencing technologies have provided novel insights into eukaryotic genomes, epigenomes, and the transcriptome, including the identification of new non‐coding RNA (ncRNA) classes such as promoter‐associated RNAs and long RNAs. Moreover, it is now clear that up to 90% of eukaryotic genomes are transcribed, generating an extraordinary range of RNAs with no coding capacity. Taken together, these new discoveries are modifying the status quo in genomic science by demonstrating that the eukaryotic gene pool is divided into two distinct categories (...) of transcripts: protein‐coding and non‐coding. The function of the majority of ncRNAs produced by the transcriptome is largely unknown; however, it is probable that many are associated with epigenetic mechanisms. The purpose of this review is to describe the most recent discoveries in the ncRNA field that implicate these molecules as key players in the epigenome. (shrink)

Slightly modified excerpt from the section 13.4 Zusammenfassung und Ausblick (translated into englisch): This chapter is based on an analysis of ethical debates on epigenetics and genome editing, debates, in which ethical arguments relating to future generations and justice play a central role. The analysis aims to contextualize new developments in genetic engineering, such as genome and epigenome editing, ethically. At the beginning, the assumptions of "genetic determinism," on which "genetic essentialism" is based, of "epigenetic determinism" as well as "genetic" (...) and "epigenetic exceptionalism" are analyzed and critically discussed. The remarks on the ethical discourse on epigenetics show that the notion of "epigenetic determinism" can sometimes be discerned not only in popular scientific discourse but also in ethical discourse. Ethical debates on epigenetics, however, have distanced themselves from this deterministic understanding. As a result, the focus in the ethical discourse on epigenetics shifts from responsibility for one's own health and that of subsequent generations to justice. What is meant here is justice, for example, in terms of access to healthy environmental conditions, regardless of whether these contribute to health with or without epigenetic agency. An analysis of the discourse on genome editing reveals that it is primarily germline interventions that are being ethically examined, with a concentration on the aspect of inheritance. The question is whether this is accompanied by an implicit "genetic determinism" or even a "genetic essentialism": the determinism could lie in the centrality of the aspect of heritability, since only genetic information is inherited. Does the aspect of heritability and genome modification play a more decisive role in debates on genome editing than the safety issue? Is the problem of embryos and their potential offspring not being able to consent to germline intervention given such a high priority because it is a genetic intervention? Under such a premise of "strong genetic determinism" supplemented by "epigenetic determinism," not only genome editing but also epigenome editing would be ethically relevant precisely because it too would have an influence on the genome. How this influence of genome editing and epigenome editing is ethically evaluated in each case therefore depends initially on whether the assumptions of "genetic" and "epigenetic determinism" are advocated. These assumptions are increasingly viewed critically in ethical discourse because they cannot be confirmed from a scientific perspective. In popular scientific debates in particular, however, they seem to persist, which ultimately also influences the public discussion. Since a broad public discussion is required especially on genome editing, a reflective approach to the various "-isms" analyzed in this chapter is central. DOI: 10.5771/9783748927242. (shrink)

How epigenetic mechanisms regulate genome output and response to stimuli is a fundamental question in development and disease. Past decades have made tremendous progress in deciphering the regulatory relationships involved by correlating aggregated (epi)genomics profiles with global perturbations. However, the recent development of epigenetic editing technologies now enables researchers to move beyond inferred conclusions, towards explicit causal reasoning, through 'programing’ precise chromatin perturbations in single cells. Here, we first discuss the major unresolved questions in the epigenetics field that can be (...) addressed by programable epigenome editing, including the context‐dependent function and memory of chromatin states. We then describe the epigenetic editing toolkit focusing on CRISPR‐based technologies, and highlight its achievements, drawbacks and promise. Finally, we consider the potential future application of epigenetic editing to the study and treatment of specific disease conditions. (shrink)

All animals have evolved solutions to manage their genomes, enabling the efficient organization of meters of DNA strands in the nucleus and allowing for nuanced regulation of gene expression while keeping transposable elements suppressed. Epigenetic modifications are central to accomplishing all these. Recent advances in sequencing technologies and the development of techniques that profile epigenetic marks and chromatin accessibility using reagents that can be used in any species has catapulted epigenomic studies in diverse animal species, shedding light on the multitude (...) of epigenomic mechanisms utilized across the evolutionary tree. Now, comparative epigenomics is a rapidly growing field that is uncovering mechanistic aspects of epigenetic modifications and chromatin organization in non‐model invertebrates, ranging from octopus to sponges. This review puts recent discoveries in the epigenetics of non‐model invertebrates in historical context, and describes new insight into the patterning and functions of DNA methylation and other highly conserved epigenetic modifications. (shrink)

Sex‐specific transcriptional and epigenomic profiles are detectable in the embryo very soon after fertilization. I propose that in male (XY) and female (XX) pre‐implantation embryos sex chromosomes establish sexually dimorphic interactions with the autosomes, before overt differences become apparent and long before gonadogenesis. Lineage determination restricts expression biases between the sexes, but the epigenetic differences are less constrained and can be perpetuated, accounting for dimorphisms that arise later in life. In this way, sexual identity is registered in the epigenome very (...) early in development. As development progresses, sex‐specific regulatory modules are harbored within shared transcriptional networks that delineate common traits. In reviewing this field, I propose that analyzing the mechanisms for sexual dimorphisms at the molecular and biochemical level and incorporating developmental and environmental factors will lead to a greater understanding of sex differences in health and disease. (shrink)

Our understanding of genomic reorganization, the mechanics of genomic transmission to offspring during germ line formation, and how these structural changes contribute to the speciation process, and genetic disease is far from complete. Earlier attempts to understand the mechanism(s) and constraints that govern genome remodeling suffered from being too narrowly focused, and failed to provide a unified and encompassing view of how genomes are organized and regulated inside cells. Here, we propose a new multidisciplinary Integrative Breakage Model for the study (...) of genome evolution. The analysis of the high‐level structural organization of genomes (nucleome), together with the functional constrains that accompany genome reshuffling, provide insights into the origin and plasticity of genome organization that may assist with the detection and isolation of therapeutic targets for the treatment of complex human disorders. (shrink)

The science of genetics is undergoing a paradigm shift. Recent discoveries, including the activity of retrotransposons, the extent of copy number variations, somatic and chromosomal mosaicism, and the nature of the epigenome as a regulator of DNA expressivity, are challenging a series of dogmas concerning the nature of the genome and the relationship between genotype and phenotype. According to three widely held dogmas, DNA is the unchanging template of heredity, is identical in all the cells and tissues of the body, (...) and is the sole agent of inheritance. Rather than being an unchanging template, DNA appears subject to a good deal of environmentally induced change. Instead of identical DNA in all the cells of the body, somatic mosaicism appears to be the normal human condition. And DNA can no longer be considered the sole agent of inheritance. We now know that the epigenome, which regulates gene expressivity, can be inherited via the germline. These developments are particularly significant for behavior genetics for at least three reasons: First, epigenetic regulation, DNA variability, and somatic mosaicism appear to be particularly prevalent in the human brain and probably are involved in much of human behavior; second, they have important implications for the validity of heritability and gene association studies, the methodologies that largely define the discipline of behavior genetics; and third, they appear to play a critical role in development during the perinatal period and, in particular, in enabling phenotypic plasticity in offspring. I examine one of the central claims to emerge from the use of heritability studies in the behavioral sciences, the principle of minimal shared maternal effects, in light of the growing awareness that the maternal perinatal environment is a critical venue for the exercise of adaptive phenotypic plasticity. This consideration has important implications for both developmental and evolutionary biology. (shrink)

Evolution is frequently concentrated in bursts of rapid morphological change and speciation followed by long‐term stasis. We propose that this pattern of punctuated equilibria results from an evolutionary tug‐of‐war between host genomes and transposable elements (TEs) mediated through the epigenome. According to this hypothesis, epigenetic regulatory mechanisms (RNA interference, DNA methylation and histone modifications) maintain stasis by suppressing TE mobilization. However, physiological stress, induced by climate change or invasion of new habitats, disrupts epigenetic regulation and unleashes TEs. With their capacity (...) to drive non‐adaptive host evolution, mobilized TEs can restructure the genome and displace populations from adaptive peaks, thus providing an escape from stasis and generating genetic innovations required for rapid diversification. This “epi‐transposon hypothesis” can not only explain macroevolutionary tempo and mode, but may also resolve other long‐standing controversies, such as Wright's shifting balance theory, Mayr's peripheral isolates model, and McClintock's view of genome restructuring as an adaptive response to challenge. (shrink)

Age‐related and cancer‐related epigenomic modifications have been associated with enhanced cell‐to‐cell gene expression variability that characterizes increased cellular stochasticity. Since gene expression variability appears to be highly reduced by—and epigenetic and phenotypic stability acquired through—direct or long‐range cellular interactions during cell differentiation, we propose a common origin for aging and cancer in the failure to control cellular stochasticity by cell–cell interactions. Tissue‐disruption‐induced cellular stochasticity associated with epigenetic drift would be at the origin of organ dysfunction because of an increase in (...) phenotypic variation among cells, ultimately leading to cell death and organ failure through a loss of coordination in cellular functions, and eventually to cancerization. We propose mechanistic research perspectives to corroborate this hypothesis and explore its evolutionary consequences, highlighting a positive correlation between the median age of mass loss onset (a proxy for the onset of organ aging) and the median age at cancer diagnosis. (shrink)

This article develops a media philosophical framework for addressing the intersection of epigenetics and complex dynamical systems in theoretical biology. In particular, it argues that the theoretical humanities need to think critically about the computability of epigenomic regulation, as well as speculatively about the possibility of an epigenomics beyond complexity. The fact that such a conceptual framework does not exist suggests not only a failure to engage with the mathematics of complexity, but also a failure to engage with its (...) history. Both epigenetics and the application of complex dynamical systems to biology originate in the mid-twentieth-century work of Conrad Hal Waddington. The article demonstrates how this genealogy of epigenetic complexity reveals the need for a speculative conception of epigenomic mediation beyond mathematical complexity. Using Whitehead’s philosophy as a conceptual anchor, the “epimedial landscape” serves as a first pass at a media philosophical revision of the complex dynamical systems view of the epigenetic landscape. (shrink)

Sperm, eggs and embryos are made up of more than genes, and there are indications that changes to non‐genetic structures in these elements of the germline can also be inherited. It is, therefore, a mistake to treat phrases like ‘germline inheritance’ and ‘genetic inheritance’ as simple synonyms, and bioethical discussion should expand its focus beyond alterations to the genome when considering the ethics of germline modification. Moreover, additional research on non‐genetic inheritance draws attention to a variety of means whereby differences (...) can be inherited in offspring generations that do not rely on differences in germline structures. Research on these diverse forms of inheritance challenges the notion that there is some special form of ethical concern that falls on germline interventions in general, and on interventions to the nuclear genome within the germline in particular. (shrink)

We have all become used to the rapid change around us, and with it, the shifting landscape of medical ethics. It appears, however, that the acceleration phase of change in biomedical sciences is only just beginning, and we need to be prepared for new challenges ahead. This issue of the journal considers several of them: in epigenome editing, 1 in bioprinting 2 and in cryonics. 3 With all of these developments, we need to be doing our ethical thinking proactively rather (...) than reactively; and we need to consider not only what we think the ethical problems might be but what frameworks we have for arguing how we should address them. There are several approaches that could be taken 4 each with their own advantages and limitations. The most fun—and the one we are perhaps best at—is to consider hypothetical scenarios, the ethical controversies associated with... (shrink)

Coral reefs have been challenged by the current rate and severity of environmental change that might outpace their ability to adapt and survive. Current research focuses on understanding how microbial communities and epigenetic changes separately affect phenotypes and gene expression of corals. Here, we provide the hypothesis that coral‐associated microorganisms may directly or indirectly affect the coral's phenotypic response through the modulation of its epigenome. Homologs of ankyrin‐repeat protein A and internalin B, which indirectly cause histone modifications in humans, as (...) well as Rv1988 histone methyltransferase, and the DNA methyltransferases Rv2966c, Mhy1, Mhy2, and Mhy3 found in coral‐associated bacteria indicate that there are potential host epigenome‐modifying proteins in the coral microbiome. With the ideas presented here, we suggest that microbiome manipulation may be a means to alter a coral's epigenome, which could aid the current efforts to protect coral reefs. Also see the video abstract here: https://youtu.be/CW9GbChjKM4. (shrink)

Child maltreatment not only leads to epigenetic changes, but also increases the risk of related behavioral deficits and mental disorders. These issues presumably are most closely associated with epigenetic changes in the brain, but epigenetic changes in peripheral tissues like blood are often examined instead, due to their accessibility. As such, the reliability of using the peripheral epigenome as a proxy for that of the brain is imperative. Previously, our lab has found aberrant methylation at the Brain-derived neurotrophic factor gene (...) in the prefrontal cortex of rats following aversive caregiving. The current study examined whether aversive caregiving alters Bdnf DNA methylation in the blood compared to the prefrontal cortex. It was revealed that DNA methylation associated with adversity increased in both tissues, but this methylation was not correlated between tissues. These findings indicate that group trends in Bdnf methylation between blood and the brain are comparable, but variation exists among individual subjects. (shrink)

What are the effects of our environment on human development and the next generation? Numerous studies have provided ample evidence that a healthy environment and lifestyle of the mother is important for her offspring. Biological mechanisms underlying these environmental influences have been proposed to involve alterations in the epigenome. Is there enough evidence to suggest a similar contribution from the part of the father? Animal models provide proof of a transgenerational epigenetic effect through the paternal germ line, but can this (...) be translated to humans? To date, literature on fathers is scarce. Human studies do not always incorporate appropriate tools to evaluate paternal influences or epigenetic effects. In reviewing the literature, I stress the need to explore and recognize paternal contributions to offspring's health within the Developmental Origins of Health and Disease hypothesis, and coin this new concept the Paternal Origins of Health and Disease paradigm. A better understanding of preconceptional origins of disease through the totality of paternal exposures, or the paternal exposome, will provide evidence-based public health recommendations for future fathers. A father's hereditary contribution exceeds that of his DNA sequence. The environment can regulate systems such as the sperm epigenome, which is inheritable as well and may steer the genome and health status of his offspring. We here suggest a new concept, the Paternal Origins of Health and Disease, as part of the DOHaD theory. (shrink)

The molecular mechanism of temperature‐dependent sex determination (TSD) is a long‐standing mystery. How is the thermal signal sensed, captured and transduced to regulate key sex genes? Although there is compelling evidence for pathways via which cells capture the temperature signal, there is no known mechanism by which cells transduce those thermal signals to affect gene expression. Here we propose a novel hypothesis we call 3D‐TSD (the three dimensions of thermolabile sex determination). We postulate that the genome has capacity to remodel (...) in response to temperature by changing 3D chromatin conformation, perhaps via temperature‐sensitive transcriptional condensates. This could rewire enhancer–promoter interactions to alter the expression of key sex‐determining genes. This hypothesis can accommodate monogenic or multigenic thermolabile sex‐determining systems, and could be combined with upstream thermal sensing and transduction to the epigenome to commit gonadal fate. (shrink)

The mammalian egg employs a wide spectrum of epigenome modification machinery to reprogram the sperm nucleus shortly after fertilization. This event is required for transcriptional activation of the paternal/zygotic genome and progression through cleavage divisions. Reprogramming of paternal nuclei requires replacement of sperm protamines with canonical and non‐canonical histones, covalent modification of histone tails, and chemical modification of DNA (notably oxidative demethylation of methylated cytosines). In this essay we highlight the role maternal histone variants play during developmental reprogramming following fertilization. (...) We discuss how reduced maternal histone variant incorporation in somatic nuclear transfer experiments may explain the reduced viability of resulting embryos and how knowledge of repressive and activating maternal factors may be used to improve somatic cell reprogramming. (shrink)

Dupras and Bunnik take on the particular privacy risks of multi-omics, in particular via a contrast and comparison of genomics and epigenomics, followed by a consideration of the issues in r...

Thomas Kuhn described the progress of science as comprising occasional paradigm shifts separated by interludes of ‘normal science’. The paradigm that has held sway since the inception of molecular biology is that genes (mainly) encode proteins. In parallel, theoreticians posited that mutation is random, inferred that most of the genome in complex organisms is non‐functional, and asserted that somatic information is not communicated to the germline. However, many anomalies appeared, particularly in plants and animals: the strange genetic phenomena of paramutation (...) and transvection; introns; repetitive sequences; a complex epigenome; lack of scaling of (protein‐coding) genes and increase in ‘noncoding’ sequences with developmental complexity; genetic loci termed ‘enhancers’ that control spatiotemporal gene expression patterns during development; and a plethora of ‘intergenic’, overlapping, antisense and intronic transcripts. These observations suggest that the original conception of genetic information was deficient and that most genes in complex organisms specify regulatory RNAs, some of which convey intergenerational information. Also see the video abstract here: https://youtu.be/qxeGwahBANw. (shrink)

Epigenetic and transcriptional variability contribute to the vast diversity of cellular and organismal phenotypes and are key in human health and disease. In this review, we describe different types, sources, and determinants of epigenetic and transcriptional variability, enabling cells and organisms to adapt and evolve to a changing environment. We highlight the latest research and hypotheses on how chromatin structure and the epigenome influence gene expression variability. Further, we provide an overview of challenges in the analysis of biological variability. An (...) improved understanding of the molecular mechanisms underlying epigenetic and transcriptional variability, at both the intra- and inter-individual level, provides great opportunity for disease prevention, better therapeutic approaches, and personalized medicine. Epigenetic and transcriptional variability mediate phenotypic plasticity, enabling adaptation to changing environments. In this review, we describe the sources of inter- and intra-individual variability and discuss epigenetic regulators of gene expression variability, including DNA methylation and chromatin structure. Understanding these molecular mechanisms will improve therapeutic approaches and personalized medicine. (shrink)

Transcriptome sequencing has identified more than a thousand potentially imprinted genes in the mouse brain. This comes as a revelation to someone who cut his teeth on the identification of imprinted genes when only a handful was known. Genomic imprinting, an epigenetic mechanism that determines expression of alleles according to sex of transmitting parent, was discovered over 25 years ago in mice but remains an enigmatic phenomenon. Why do these genes disobey the normal Mendelian logic of inheritance, do they function (...) in specific processes, and how is their imprinting conferred? Next generation sequencing technologies are providing an unprecedented opportunity to survey the whole genome for imprinted genes and are beginning to reveal that imprinting may be more pervasive than we had come to believe. Such advances should lay the foundation for a definitive account of imprinting, but may also challenge accepted views on what it means to be imprinted.Editor's suggested further reading in BioEssays RNA as the substrate for epigenome‐environment interactions Abstract. (shrink)

Excerpt: 1. Introduction This chapter provides insight into the diverse ethical debates on genetics and epigenetics. Much controversy surrounds debates about intervening into the germline genome of human embryos, with catchwords such as genome editing, designer baby, and CRISPR/Cas. The idea that it is possible to design a child according to one’s personal preferences is, however, a quite distorted view of what is actually possible with new gene technologies and gene therapies. These are much more limited than the editing and (...) design metaphors suggest. Such metaphors are therefore highly problematic phrases in the context of new gene technologies, for two reasons. On one hand, to design a child of choice by modifying the genome would require modifying any gene of choice, which is more than can be done with current gene technologies, such as CRISPR/Cas. On the other hand, a modification of genes would need to be enough to create any characteristic of choice in the future child. The latter presupposes the assumption of genetic determinism. Moreover, the CRISPR/Cas technology can not only be used in a potentially therapeutic manner at the germline level. In addition, there is the (more likely) scenario of a future clinical therapeutic use of these new gene technologies for modifying the DNA sequence of other cells of the body (somatic genome editing). There is also the option of modifying the epigenome, that is, the spatial configuration of DNA (epigenome editing) (see table 1). Like genetics and genome editing, epigenetics has been at the center of recent popular scientific and ethical discourse as well as scientific debates. The concept of epigenetics has given rise to very different notions of inheritability and responsibility for health, which, however, are oftentimes based on scientifically controversial basic assumptions. That there continues to be covert genetic determinism in the form of epigenetic determinism (see table 2) in debates about epigenetics has been pointed out in ethical analyses of epigenetics. Neither genetic determinism nor epigenetic determinism has been confirmed scientifically. It is therefore important to recognize the concepts that are discussed (and sometimes harshly criticized) in debates about genome editing and epigenetics—for example, concepts about the causal role of DNA for our own life course. This importance is based on the fact that if we understand such controversial concepts, we will be able to remain critical when evaluating scientific knowledge and ethical arguments about genome editing and epigenetics. This chapter, therefore, explains some of these concepts. For an ethical analysis of epigenetics as well as of genome editing, it is necessary to understand and critically reflect upon the underlying concepts of genetic determinism and other, related -isms. The following section offers a detailed introduction to these -isms (section 2; see also table 2). Section 3 provides an ethical analysis of genome editing and epigenetics based on the explanations in section 2. Section 3 focuses on inheritability and responsibility, justice, safety, the problem of consent, and the effects of genome editing and epigenetics on embryos and future generations. This section does not discuss in detail further points that can be found in ethical debates about epigenetics as well as in ethical debates about genome editing. These points include (among others): • fear that the findings of epigenetics and that the methods of genome editing are misused—this also with respect to eugenics and enhancement; • naturalness—an issue we mention in passing a few times in the following analysis; • a possible connection between the genome/epigenome and the concept of human dignity, and the derived danger of instrumentalization and infringement of autonomy when intervening in the genome or epigenome. Since current discourse about ethical issues associated with genome editing focuses mainly on germline interventions, which are, for instance, interventions into a human embryo’s genome, we mainly focus on germline interventions when comparing the debates on genome editing and on epigenetics in section 3. (shrink)

Several metabolites serve as substrates for histone modifications and communicate changes in the metabolic environment to the epigenome. Technologies such as metabolomics and proteomics have allowed us to reconstruct the interactions between metabolic pathways and histones. These technologies have shed light on how nutrient availability can have a dramatic effect on various histone modifications. This metabolism–epigenome cross talk plays a fundamental role in development, immune function, and diseases like cancer. Yet, major challenges remain in understanding the interactions between cellular metabolism (...) and the epigenome. How the levels and fluxes of various metabolites impact epigenetic marks is still unclear. Discussed herein are recent applications and the potential of systems biology methods such as flux tracing and metabolic modeling to address these challenges and to uncover new metabolic–epigenetic interactions. These systems approaches can ultimately help elucidate how nutrients shape the epigenome of microbes and mammalian cells. (shrink)

The success of the Human Genome Project has prompted interest in advancing the nascent field of exposomics. The exposome, which is dynamic and variable and changes over time, consists of all the internal and external exposures an individual has over a lifetime beginning with the prenatal period and early childhood. Efforts are underway to decipher the human epigenome by identifying the effects of all deleterious environmental exposures according to duration of exposure and time period. In this article, we argue that (...) the deciphering of the human exposome should be accompanied by sustained efforts to address the ethical, social and legal implications (ELSI) of exposomics. This will require financial investments from the National Institutes of Health (NIH), the European Union and other public and private funding agencies, analogous to support provided by NIH to address ELSI issues in genomics. (shrink)

Histone variants are specialized histones which replace their canonical counterparts in specific nucleosomes. Together with histone post‐translational modifications and DNA methylation, they contribute to the epigenome. Histone variants are incorporated at specific locations by the concerted action of histone chaperones and ATP‐dependent chromatin remodelers. Recent studies have shown that the histone chaperone FACT plays key roles in preventing pervasive incorporation of two histone variants: H2A.Z and CenH3/CENP‐A. In addition, Spt6, another histone chaperone, was also shown to be important for appropriate (...) H2A.Z localization. FACT and Spt6 are both associated with elongating RNA polymerase II. Based on these two examples, we propose that the establishment and maintenance of histone variant genomic distributions depend on a transcription‐coupled epigenome editing (or surveillance) function of histone chaperones. (shrink)

Les approches pour lutter contre le fléau des maladies chroniques qui augmentent dans le monde entier se révèlent infructueuses et très coûteuses. Il est maintenant possible de corriger les chiffres alarmants et d’envisager une prévention efficace en adoptant le nouveau paradigme des Origines du Développement de la Santé et des Maladies (DOHaD), à condition d’intervenir très tôt en agissant sur le risque et non lorsque la maladie est déjà apparue. Ce concept est largement reconnu grâce à des études épidémiologiques et (...) des études animales. Les influences des facteurs environnementaux – nutrition, stress, psycho-affectifs, toxiques, bactériens et physiques – sur les processus épigénétiques représentent une révolution. En effet, les DMR modifications épigénétiques conservent la mémoire des impacts de facteurs environnementaux auxquels un individu est soumis tout au long de sa vie. Une période cruciale est le développement précoce, pré et postnatal, les 1000 jours ; cruciale parce que l’épigénome est particulièrement sensible aux effets de l’environnement, et aussi parce que l’individu construit son capital santé pour répondre plus ou moins bien aux aléas de la vie. En outre, l’existence de mécanismes non génétiques et non culturels capables de transférer la mémoire des expériences/expositions à des facteurs environnementaux parentaux et qui conditionnent la réactivité des générations suivantes à différents environnements au cours de leur vie suscite un intérêt grandissant. L’idée selon laquelle des marques épigénétiques non effacées lors des phases de reprogrammation est actuellement très en vogue, voire considérée à tort comme acquise malgré la rareté des exemples probants. Cependant, des questions fondamentales subsistent quant à la nature, aux rôles et à l’impact des marques et des mécanismes épigénétiques, des ARN non codants ou d’autres mécanismes et à leur persistance au cours des générations. Un modèle intégrant ces différents systèmes, leurs interactions avec l’environnement et les fenêtres de développement de la sensibilité selon le sexe du parent et de l’enfant reste à construire. Sur la base de la malléabilité des mécanismes épigénétiques sous-jacents, la réversibilité des marques environnementales ouvre de nouvelles perspectives. Cependant, comment les facteurs conférant une susceptibilité accrue ou une résilience vis-à-vis du développement des maladies agissent et influencent les mécanismes épigénétiques reste à élucider. Si la mémoire des expériences/expositions à des facteurs environnementaux est effectivement transmissible, le principal défi pour l’individu, et surtout pour les pouvoirs publics, est d’être en mesure d’éviter ceux qui posent des risques pour la descendance. Ces données peuvent déplacer le curseur des responsabilités en matière de soins de santé, de la sphère privée à la sphère socio-géographico-politique. (shrink)

In this review, we discuss the application of mouse models to the identification and pre‐clinical validation of novel therapeutic targets in colorectal cancer, and to the search for early disease biomarkers. Large‐scale genomic, transcriptomic and epigenomic profiling of colorectal carcinomas has led to the identification of many candidate genes whose direct contribution to tumourigenesis is yet to be defined; we discuss the utility of cross‐species comparative ‘omics‐based approaches to this problem. We highlight recent progress in modelling late‐stage disease using mice, (...) and discuss ways in which mouse models could better recapitulate the complexity of human cancers to tackle the problem of therapeutic resistance and recurrence after surgical resection. (shrink)

Bone‐marrow mesenchymal stem cell (BM‐MSC) proliferation and lineage commitment are under the coordinated control of metabolism and epigenetics; the MSC niche contains low oxygen, which is an important determinant of the cellular metabolic state. In turn, metabolism drives stem cell fate decisions via alterations of the chromatin landscape. Due to the fundamental role of BM‐MSCs in the development of adipose tissue, bones and cartilage, age‐associated changes in metabolism and the epigenome perturb the balance between stem cell proliferation and differentiation leading (...) to stem cell depletion, fat accumulation and bone‐quality related diseases. Therefore, understanding the dynamics of the metabolism‐chromatin interplay is crucial for maintaining the stem cell pool and delaying the development and progression of ageing. This review summarizes the current knowledge on the role of metabolism in stem cell identity and highlights the impact of the metabolic inputs on the epigenome, with regards to stemness and pluripotency. (shrink)

The lysine demethylase KDM5A collaborates with PARP1 and the histone variant macroH2A1.2 to modulate chromatin to promote DNA repair. Indeed, KDM5A engages poly(ADP‐ribose) (PAR) chains at damage sites through a previously uncharacterized coiled‐coil domain, a novel binding mode for PAR interactions. While KDM5A is a well‐known transcriptional regulator, its function in DNA repair is only now emerging. Here we review the molecular mechanisms that regulate this PARP1‐macroH2A1.2‐KDM5A axis in DNA damage and consider the potential involvement of this pathway in transcription (...) regulation and cancer. Using KDM5A as an example, we discuss how multifunctional chromatin proteins transition between several DNA‐based processes, which must be coordinated to protect the integrity of the genome and epigenome. The dysregulation of chromatin and loss of genome integrity that is prevalent in human diseases including cancer may be related and could provide opportunities to target multitasking proteins with these pathways as therapeutic strategies. (shrink)

Every cell, tissue, organ and organism is competent to use signs to exchange information reaching common coordinations and organisations of both single cell and group behavior. These sign-mediated interactions we term biological communication. The regulatory system that works in development, morphology, cell fate and identity, physiology, genetic instructions, immunity, memory/learning, physical and mental disease depends on epigenetic marks. The communication of cells, persistent viruses and their defectives such as mobile genetic elements and RNA networks ensures both the transport of regulatory (...) instructions and the reprogramming of these instructions. But how are the different states of the epigenome orchestrated? The epigenetic pathways respond to various signaling cues such as DNA methylation, histone variants, histone modifications, chromatin structure, nucleosome remodeling, and epigenetic interactions. Epigenetic signals are responsible for the establishment, maintenance and reversal of transcriptional states that are fundamental for the cell's ability to memorize past events, such as changes in the external environment, socio-sphere or developmental cues. External signals trigger changes in the epigenome, allowing cells to respond dynamically. Internal signals direct activities that are necessary for body maintenance, and repairing damaged tissues and organs. With the emergence of epigenetic memory, organisms can fix historical and context dependent impressive experiences. Evolution from now on learnt to learn. Learning means organisms can avoid reproduction of always the same. This is key to adaptation. However, inheritance of acquired characteristics is only one of the many examples of the explanatory power of epigenetics. Behavioral epigenetics demonstrates the way in which environmental and social experiences produce individual differences in behaviour, cognition, personality, and mental health. This book assembles experts to outline the various motifs of all kinds of epigenetic regulation of cells throughout their lives. (shrink)

With the advent of gene editing technologies like CRISPR/Cas9, it has become possible to edit genomic regions of interest for research and therapeutic purposes. These technologies have also been adapted to alter gene expression without changing their DNA sequence, allowing epigenetic edits. While genetic editors make edits by cutting the genome at specified regions, epigenetic editors leverage the same targeting mechanism but act based on the epigenetic modifier fused to them, such as a methyltransferase. Here, we discuss two recently employed (...) epigenetic editors (epi‐editors) that silenced target genes involved in disease to mitigate their effects. Neumann et al. reported the construction of an epigenetic editor called CHARM that could methylate and silence the prion gene in mouse brains and subsequently switch itself off. Additionally, Capelluti et al. developed an epi‐editor called EvoETR that knocked down Pcsk9 in the murine liver to reduce LDL levels. We aim to highlight the design principles underlying the design of these epi‐editors to inform future editor designs. (shrink)

Genetic epidemiology is a rapidly advancing field due to the recent availability of large amounts of omics data. In recent years, it has become possible to obtain omics information at the single‐cell level, so genetic epidemiological models need to be updated to integrate with single‐cell expression data. In this perspective paper, we propose a cell population‐based framework for genetic epidemiology in the single‐cell era. In this framework, genetic diversity influences phenotypic diversity through the diversity of cell population profiles, which are (...) defined as high‐dimensional probability distributions of the state spaces of biomolecules of each omics layer. We discuss how biomolecular experimental measurement data can capture the different properties of this distribution. In particular, single‐cell data constitute a sample from this population distribution where only some coordinate values are observable. From a data analysis standpoint, we introduce methodology for feature extraction from cell population profiles. Finally, we discuss how this framework can be applied not only to genetic epidemiology but also to systems biology. (shrink)

There is increasing evidence that dynamic changes to chromatin, chromosomes and nuclear architecture are regulated by RNA signalling. Although the precise molecular mechanisms are not well understood, they appear to involve the differential recruitment of a hierarchy of generic chromatin modifying complexes and DNA methyltransferases to specific loci by RNAs during differentiation and development. A significant fraction of the genome-wide transcription of non-protein coding RNAs may be involved in this process, comprising a previously hidden layer of intermediary genetic information that (...) underpins developmental ontogeny and the differences between species, ecotypes and individuals. It is also evident that RNA editing is a primary means by which hardwired genetic information in animals can be altered by environmental signals, especially in the brain, indicating a dynamic RNA-mediated interplay between the transcriptome, the environment and the epigenome. Moreover, RNA-directed regulatory processes may also transfer epigenetic information not only within cells but also between cells and organ systems, as well as across generations. (shrink)