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Epigenomes, Volume 5, Issue 2 (June 2021) – 9 articles

Cover Story (view full-size image): Determining DNA methylation is one of the important goals of epigenetics. Another crucial aim is combining bisulfite treatment of associate genetics and epigenetics with phenotypic traits. This has now become possible with genome-wide association studies (GWAS) and epigenome-wide association studies (EWAS). The EpiDiverse EWAS pipeline was implemented based on the GEM R package, including graphical outputs, novel missing data imputation, compatibility with new input types, and was tested on Picea abies (Norway spruce) and Quercus lobata (valley oak) data sets. View this paper
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Review
The Contribution of Epigenetic Inheritance Processes on Age-Related Cognitive Decline and Alzheimer’s Disease
Epigenomes 2021, 5(2), 15; https://0-doi-org.brum.beds.ac.uk/10.3390/epigenomes5020015 - 18 Jun 2021
Viewed by 705
Abstract
During the last years, epigenetic processes have emerged as important factors for many neurodegenerative diseases, such as Alzheimer’s disease (AD). These complex diseases seem to have a heritable component; however, genome-wide association studies failed to identify the genetic loci involved in the etiology. [...] Read more.
During the last years, epigenetic processes have emerged as important factors for many neurodegenerative diseases, such as Alzheimer’s disease (AD). These complex diseases seem to have a heritable component; however, genome-wide association studies failed to identify the genetic loci involved in the etiology. So, how can these changes be transmitted from one generation to the next? Answering this question would allow us to understand how the environment can affect human populations for multiple generations and explain the high prevalence of neurodegenerative diseases, such as AD. This review pays particular attention to the relationship among epigenetics, cognition, and neurodegeneration across generations, deepening the understanding of the relevance of heritability in neurodegenerative diseases. We highlight some recent examples of EI induced by experiences, focusing on their contribution of processes in learning and memory to point out new targets for therapeutic interventions. Here, we first describe the prominent role of epigenetic factors in memory processing. Then, we briefly discuss aspects of EI. Additionally, we summarize evidence of how epigenetic marks inherited by experience and/or environmental stimuli contribute to cognitive status offspring since better knowledge of EI can provide clues in the appearance and development of age-related cognitive decline and AD. Full article
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Review
H3K4 Methylation in Aging and Metabolism
Epigenomes 2021, 5(2), 14; https://0-doi-org.brum.beds.ac.uk/10.3390/epigenomes5020014 - 18 Jun 2021
Viewed by 15335
Abstract
During the process of aging, extensive epigenetic alterations are made in response to both exogenous and endogenous stimuli. Here, we summarize the current state of knowledge regarding one such alteration, H3K4 methylation (H3K4me), as it relates to aging in different species. We especially [...] Read more.
During the process of aging, extensive epigenetic alterations are made in response to both exogenous and endogenous stimuli. Here, we summarize the current state of knowledge regarding one such alteration, H3K4 methylation (H3K4me), as it relates to aging in different species. We especially highlight emerging evidence that links this modification with metabolic pathways, which may provide a mechanistic link to explain its role in aging. H3K4me is a widely recognized marker of active transcription, and it appears to play an evolutionarily conserved role in determining organism longevity, though its influence is context specific and requires further clarification. Interestingly, the modulation of H3K4me dynamics may occur as a result of nutritional status, such as methionine restriction. Methionine status appears to influence H3K4me via changes in the level of S-adenosyl methionine (SAM, the universal methyl donor) or the regulation of H3K4-modifying enzyme activities. Since methionine restriction is widely known to extend lifespan, the mechanistic link between methionine metabolic flux, the sensing of methionine concentrations and H3K4me status may provide a cogent explanation for several seemingly disparate observations in aging organisms, including age-dependent H3K4me dynamics, gene expression changes, and physiological aberrations. These connections are not yet entirely understood, especially at a molecular level, and will require further elucidation. To conclude, we discuss some potential H3K4me-mediated molecular mechanisms that may link metabolic status to the aging process. Full article
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Review
The Placenta as a Target of Epigenetic Alterations in Women with Gestational Diabetes Mellitus and Potential Implications for the Offspring
Epigenomes 2021, 5(2), 13; https://0-doi-org.brum.beds.ac.uk/10.3390/epigenomes5020013 - 10 May 2021
Viewed by 1586
Abstract
Gestational diabetes mellitus (GDM) is a pregnancy complication first detected in the second or third trimester in women that did not show evident glucose intolerance or diabetes before gestation. In 2019, the International Diabetes Federation reported that 15.8% of live births were affected [...] Read more.
Gestational diabetes mellitus (GDM) is a pregnancy complication first detected in the second or third trimester in women that did not show evident glucose intolerance or diabetes before gestation. In 2019, the International Diabetes Federation reported that 15.8% of live births were affected by hyperglycemia during pregnancy, of which 83.6% were due to gestational diabetes mellitus, 8.5% were due to diabetes first detected in pregnancy, and 7.9% were due to diabetes detected before pregnancy. GDM increases the susceptibility to developing chronic diseases for both the mother and the baby later in life. Under GDM conditions, the intrauterine environment becomes hyperglycemic, while also showing high concentrations of fatty acids and proinflammatory cytokines, producing morphological, structural, and molecular modifications in the placenta, affecting its function; these alterations may predispose the baby to disease in adult life. Molecular alterations include epigenetic mechanisms such as DNA and RNA methylation, chromatin remodeling, histone modifications, and expression of noncoding RNAs (ncRNAs). The placenta is a unique organ that originates only in pregnancy, and its main function is communication between the mother and the fetus, ensuring healthy development. Thus, this review provides up-to-date information regarding two of the best-documented (epigenetic) mechanisms (DNA methylation and miRNA expression) altered in the human placenta under GDM conditions, as well as potential implications for the offspring. Full article
(This article belongs to the Collection Epigenetic Mechanisms in Diabetes Research)
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Article
The EpiDiverse Plant Epigenome-Wide Association Studies (EWAS) Pipeline
Epigenomes 2021, 5(2), 12; https://0-doi-org.brum.beds.ac.uk/10.3390/epigenomes5020012 - 04 May 2021
Viewed by 1418
Abstract
Bisulfite sequencing is a widely used technique for determining DNA methylation and its relationship with epigenetics, genetics, and environmental parameters. Various techniques were implemented for epigenome-wide association studies (EWAS) to reveal meaningful associations; however, there are only very few plant studies available to [...] Read more.
Bisulfite sequencing is a widely used technique for determining DNA methylation and its relationship with epigenetics, genetics, and environmental parameters. Various techniques were implemented for epigenome-wide association studies (EWAS) to reveal meaningful associations; however, there are only very few plant studies available to date. Here, we developed the EpiDiverse EWAS pipeline and tested it using two plant datasets, from P. abies (Norway spruce) and Q. lobata (valley oak). Hence, we present an EWAS implementation tested for non-model plant species and describe its use. Full article
(This article belongs to the Special Issue Advances in Plant Epigenetics and Epigenomics)
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Editorial
Firing up Cold Tumors—Targeting the Epigenetic Machinery to Enhance Cancer Immunotherapy
Epigenomes 2021, 5(2), 11; https://0-doi-org.brum.beds.ac.uk/10.3390/epigenomes5020011 - 03 May 2021
Viewed by 818
Abstract
Cancer immunotherapy using monoclonal antibodies targeting immune checkpoint proteins, such as PD-L1 or PD-1 (i [...] Full article
(This article belongs to the Special Issue Targeting the Epigenetic Machinery to Enhance Cancer Immunotherapy)
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Article
Early-Life Exposure to Environmental Contaminants Perturbs the Sperm Epigenome and Induces Negative Pregnancy Outcomes for Three Generations via the Paternal Lineage
Epigenomes 2021, 5(2), 10; https://0-doi-org.brum.beds.ac.uk/10.3390/epigenomes5020010 - 01 May 2021
Viewed by 1227
Abstract
Due to the grasshopper effect, the Arctic food chain in Canada is contaminated with persistent organic pollutants (POPs) of industrial origin, including polychlorinated biphenyls and organochlorine pesticides. Exposure to POPs may be a contributor to the greater incidence of poor fetal growth, placental [...] Read more.
Due to the grasshopper effect, the Arctic food chain in Canada is contaminated with persistent organic pollutants (POPs) of industrial origin, including polychlorinated biphenyls and organochlorine pesticides. Exposure to POPs may be a contributor to the greater incidence of poor fetal growth, placental abnormalities, stillbirths, congenital defects and shortened lifespan in the Inuit population compared to non-Aboriginal Canadians. Although maternal exposure to POPs is well established to harm pregnancy outcomes, paternal transmission of the effects of POPs is a possibility that has not been well investigated. We used a rat model to test the hypothesis that exposure to POPs during gestation and suckling leads to developmental defects that are transmitted to subsequent generations via the male lineage. Indeed, developmental exposure to an environmentally relevant Arctic POPs mixture impaired sperm quality and pregnancy outcomes across two subsequent, unexposed generations and altered sperm DNA methylation, some of which are also observed for two additional generations. Genes corresponding to the altered sperm methylome correspond to health problems encountered in the Inuit population. These findings demonstrate that the paternal methylome is sensitive to the environment and that some perturbations persist for at least two subsequent generations. In conclusion, although many factors influence health, paternal exposure to contaminants plays a heretofore-underappreciated role with sperm DNA methylation contributing to the molecular underpinnings involved. Full article
(This article belongs to the Special Issue Health and Disease through A Sex and Gender Lens)
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Article
A Pilot Study Investigating the Role of Gender in the Intergenerational Relationships between Gene Expression, Chronic Pain, and Adverse Childhood Experiences in a Clinical Sample of Youth with Chronic Pain
Epigenomes 2021, 5(2), 9; https://0-doi-org.brum.beds.ac.uk/10.3390/epigenomes5020009 - 15 Apr 2021
Viewed by 1227
Abstract
Chronic pain is a highly prevalent and costly issue that often emerges during childhood or adolescence and persists into adulthood. Adverse childhood experiences (ACEs) increase risk for several adverse health conditions, including chronic pain. Recent evidence suggests that parental trauma (ACEs, post-traumatic stress [...] Read more.
Chronic pain is a highly prevalent and costly issue that often emerges during childhood or adolescence and persists into adulthood. Adverse childhood experiences (ACEs) increase risk for several adverse health conditions, including chronic pain. Recent evidence suggests that parental trauma (ACEs, post-traumatic stress disorder (PTSD) symptoms) confers risk of poor health outcomes in their children. Intergenerational relationships between parental trauma and child chronic pain may be mediated by epigenetic mechanisms. A clinical sample of youth with chronic pain and their parents completed psychometrically sound questionnaires assessing ACEs, PTSD symptoms, and chronic pain, and provided a saliva sample. These were used to investigate the intergenerational relationships between four epigenetic biomarkers (COMT, DRD2, GR, and SERT), trauma, and chronic pain. The results indicated that the significant biomarkers were dependent upon the gender of the child, wherein parental ACEs significantly correlated with changes in DRD2 expression in female children and altered COMT expression in the parents of male children. Additionally, the nature of the ACE (maltreatment vs. household dysfunction) was associated with the specific epigenetic changes. There may be different pathways through which parental ACEs confer risk for poor outcomes for males and females, highlighting the importance of child gender in future investigations. Full article
(This article belongs to the Special Issue Health and Disease through A Sex and Gender Lens)
Review
Cell-Free DNA Methylation as Blood-Based Biomarkers for Pancreatic Adenocarcinoma—A Literature Update
Epigenomes 2021, 5(2), 8; https://0-doi-org.brum.beds.ac.uk/10.3390/epigenomes5020008 - 09 Apr 2021
Cited by 1 | Viewed by 986
Abstract
Pancreatic adenocarcinoma has a horrible prognosis, which is partly due to difficulties in diagnosing the disease in an early stage. Additional blood-born biomarkers for pancreatic adenocarcinoma are needed. Epigenetic modifications, as changes in DNA methylation, is a fundamental part of carcinogenesis. The aim [...] Read more.
Pancreatic adenocarcinoma has a horrible prognosis, which is partly due to difficulties in diagnosing the disease in an early stage. Additional blood-born biomarkers for pancreatic adenocarcinoma are needed. Epigenetic modifications, as changes in DNA methylation, is a fundamental part of carcinogenesis. The aim of this paper is to do an update on cell-free DNA methylation as blood-based biomarkers for pancreatic adenocarcinoma. The current literature including our studies clearly indicates that cell-free DNA methylation has the potential as blood-based diagnostic and prognostic biomarkers for pancreatic adenocarcinoma. However, still no clinical applicable biomarker for pancreatic adenocarcinoma based on DNA methylation do exist. Further well-designed validation studies are needed. Full article
(This article belongs to the Special Issue Epigenetics of Pancreatic Cancer 2.0)
Communication
Enhancement of the Antileukemic Action of the Inhibitors of DNA and Histone Methylation: 5-Aza-2′-Deoxycytidine and 3-Deazaneplanocin-A by Vitamin C
Epigenomes 2021, 5(2), 7; https://0-doi-org.brum.beds.ac.uk/10.3390/epigenomes5020007 - 24 Mar 2021
Viewed by 1016
Abstract
Epigenetic gene silencing by DNA methylation and histone methylation by EZH2 play an important role in the development of acute myeloid leukemia (AML). EZH2 catalyzes the trimethylation of histone H3-lysine 27-trimethylated (H3K27me3). These epigenetic alterations silence the expression of the genes that suppress [...] Read more.
Epigenetic gene silencing by DNA methylation and histone methylation by EZH2 play an important role in the development of acute myeloid leukemia (AML). EZH2 catalyzes the trimethylation of histone H3-lysine 27-trimethylated (H3K27me3). These epigenetic alterations silence the expression of the genes that suppress leukemogenesis. Reversal of this gene silencing by 5-aza-2′-deoxycytidine (5-Aza-CdR), an inhibitor of DNA methylation, and by 3-deazaneplanocin-A (DZNep), an inhibitor of EZH2, results in synergistic gene reactivation and antileukemic interaction. The objective of this study is to determine if the addition of another epigenetic agent could further enhance the antileukemic action of these inhibitors of DNA and histone methylation. Vitamin C (Vit C) is reported to enhance the antineoplastic action of 5-Aza-CdR on AML cells. The mechanism responsible for this action of Vit C is due to its function as a cofactor of alpha-ketoglutarate-dependent dioxygenases (α-KGDD). The enhancement by Vit C of the catalytic activity of α-KGDD of the ten eleven translocation (TET) pathway, as well as of the Jumonji C histone demethylases (JHDMs), is shown to result in demethylation of DNA and histones, leading to reactivation of tumor suppressor genes and an antineoplastic effect. This action of Vit C has the potential to complement the antileukemic action of 5-Aza-CdR and DZNep. We observe that Vit C remarkably increases the antineoplastic activity of 5-Aza-CdR and DZNep against myeloid leukemic cells. An important step to bring this novel epigenetic therapy to clinical trial in patients with AML is the determination of its optimal dose schedule. Full article
(This article belongs to the Special Issue Epigenetic Cancer Therapy: Targeting DNA and Histone Methylation)
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