Specific Epigenetic Marks Research Articles

Comparative profiling of epigenetic modifications among individuals living in different high and low air pollution zones: A pilot study from India

Epigenetic modifications act as an important bridge to regulate the complex network of gene-environment interactions. As these mechanisms determine the gene-expression patterns via regulating the transcriptomic machinery, environmental stress induced epigenetic modifications may interrupt distinct cellular functions resulting into generation of diseased phenotypes. In the present study, we used a multi-city approach to compare the epigenomic signatures of individuals living in two tiers of Indian cities categorized as low-risk and high-risk air pollution zones. The high-risk group reported marked changes in the expression levels of epigenetic modifiers (DNMT1, DNMT3a, EZH2, EHMT2 and HAT), that maintains the levels of specific epigenetic marks essential for appropriate gene functioning. These results also coincided with the observed alterations in the levels of DNA methylation (LINE-1 and % 5mC), and histone modifications (H3 and H4), among the high-risk group. In addition, higher degree of changes reported in the expression profile of a selected miRNA panel in the high-risk group indicated the probability of deregulated transcriptional machinery. This was further confirmed by the analysis of a target gene panel involved in various signalling pathways, which revealed differential expression of the gene transcripts regulating cell cycle, inflammation, cell survival, apoptosis and cell adhesion. Together, our results provide first insights of epigenetic modifications among individuals living in different high and low levels of air pollution zones of India. However, further steps to develop a point-of-care epigenomic assay for human bio-monitoring may be immensely beneficial to reduce the health burden of air pollution especially in low and-middle-income countries.

Genomics and epigenomics of addiction.

Recent progress in the genomics and epigenomics of addiction has contributed to improving our understanding of this complex mental disorder's etiology, filling the gap between genes, environment, and behavior. We review the behavioral genetic studies reporting gene and environment interactions that explain the polygenetic contribution to the resilience and vulnerability to develop addiction. We discuss the evidence of polymorphic candidate genes that confer susceptibility to develop addiction as well as the studies of specific epigenetic marks that contribute to vulnerability and resilience to addictive-like behavior. A particular emphasis has been devoted to the miRNA changes that are considered potential biomarkers. The increasing knowledge about the technology required to alter miRNA expression may provide promising novel therapeutic tools. Finally, we give future directions for the field's progress in disentangling the connection between genes, environment, and behavior.

Smchd1 is a maternal effect gene required for genomic imprinting.

Genomic imprinting establishes parental allele-biased expression of a suite of mammalian genes based on parent-of-origin specific epigenetic marks. These marks are under the control of maternal effect proteins supplied in the oocyte. Here we report epigenetic repressor Smchd1 as a novel maternal effect gene that regulates the imprinted expression of ten genes in mice. We also found zygotic SMCHD1 had a dose-dependent effect on the imprinted expression of seven genes. Together, zygotic and maternal SMCHD1 regulate three classic imprinted clusters and eight other genes, including non-canonical imprinted genes. Interestingly, the loss of maternal SMCHD1 does not alter germline DNA methylation imprints pre-implantation or later in gestation. Instead, what appears to unite most imprinted genes sensitive to SMCHD1 is their reliance on polycomb-mediated methylation as germline or secondary imprints, therefore we propose that SMCHD1 acts downstream of polycomb imprints to mediate its function.

Comparative epigenetics in animal physiology: An emerging frontier

The unprecedented access to annotated genomes now facilitates the investigation of the molecular basis of epigenetic phenomena in phenotypically diverse animals. In this critical review, we describe the roles of molecular epigenetic mechanisms in regulating mitotically and meiotically stable spatiotemporal gene expression, phenomena that provide the molecular foundation for the intra-, inter-, and trans-generational emergence of physiological phenotypes. By focusing principally on emerging comparative epigenetic roles of DNA-level and transcriptome-level epigenetic mark dynamics in the emergence of phenotypes, we highlight the relationship between evolutionary conservation and innovation of specific epigenetic pathways, and their interplay as a priority for future study. This comparative approach is expected to significantly advance our understanding of epigenetic phenomena, as animals show a diverse array of strategies to epigenetically modify physiological responses. Additionally, we review recent technological advances in the field of molecular epigenetics (single-cell epigenomics and transcriptomics and editing of epigenetic marks) in order to (1) investigate environmental and endogenous factor dependent epigenetic mark dynamics in an integrative manner; (2) functionally test the contribution of specific epigenetic marks for animal phenotypes via genome and transcript-editing tools. Finally, we describe advantages and limitations of emerging animal models, which under the Krogh principle, may be particularly useful in the advancement of comparative epigenomics and its potential translational applications in animal science, ecotoxicology, ecophysiology, climate change science and wild-life conservation, as well as organismal health.

DNA Methylation as a Potential Molecular Mechanism in X-linked Dystonia-Parkinsonism.

X-linked dystonia-parkinsonism is a neurodegenerative movement disorder. The underlying molecular basis has still not been completely elucidated, but likely involves dysregulation of TAF1 expression. In X-linked dystonia-parkinsonism, 3 disease-specific single-nucleotide changes (DSCs) introduce (DSC12) or abolish (DSC2 and DSC3) CpG dinucleotides and consequently sites of putative DNA methylation. Because transcriptional regulation tightly correlates with specific epigenetic marks, we investigated the role of DNA methylation in the pathogenesis of X-linked dystonia-parkinsonism. DNA methylation at DSC12, DSC3, and DSC2 was quantified by bisulfite pyrosequencing in DNA from peripheral blood leukocytes, fibroblasts, induced pluripotent stem cell-derived cortical neurons and brain tissue from X-linked dystonia-parkinsonism patients and age- and sex-matched healthy Filipino controls in a prospective study. Compared with controls, X-linked dystonia-parkinsonism patients showed striking differences in DNA methylation at the 3 investigated CpG sites. Using methylation-sensitive luciferase reporter gene assays and immunoprecipitation, we demonstrated (1) that lack of DNA methylation because of DSC2 and DSC3 affects gene promoter activity and (2) that methylation at all 3 investigated CpG sites alters DNA-protein interaction. Interestingly, DSC3 decreased promoter activity per se compared with wild type, and promoter activity further decreased when methylation was present. Moreover, we identified specific binding of proteins to the investigated DSCs that are associated with splicing and RNA and DNA binding. We identified altered DNA methylation in X-linked dystonia-parkinsonism patients as a possible additional mechanism modulating TAF1 expression and putative novel targets for future therapies using DNA methylation-modifying agents. © 2020 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

Unraveling the epigenetic landscape of depression: focus on early life stress .

Depression is a devastating psychiatric disorder caused by a combination of genetic predisposition and life events, mainly exposure to stress. Early life stress (ELS) in particular is known to “scar” the brain, leading to an increased susceptibility to developing depression later in life via epigenetic mechanisms. Epigenetic processes lead to changes in gene expression that are not due to changes in DNA sequence, but achieved via modulation of chromatin modifications, DNA methylation, and noncoding RNAs. Here we review common epigenetic mechanisms including the enzymes that take part in reading, writing, and erasing specific epigenetic marks. We then describe recent developments in understanding how ELS leads to changes in the epigenome that are manifested in increased susceptibility to depression-like abnormalities in animal models. We conclude with highlighting the need for future studies that will potentially enable the utilisation of the understanding of epigenetic changes linked to ELS for the development of much-needed novel therapeutic strategies and biomarker discovery.

Evidence for novel epigenetic marks within plants.

Variation in patterns of gene expression can result from modifications in the genome that occur without a change in the sequence of the DNA; such modifications include methylation of cytosine to generate 5-methylcytosine (5mC) resulting in the generation of heritable epimutation and novel epialleles. This type of non-sequence variation is called epigenetics. The enzymes responsible for generation of such DNA modifications in mammals are named DNA methyltransferases (DNMT) including DNMT1, DNMT2 and DNMT3. The later stages of oxidations to these modifications are catalyzed by Ten Eleven Translocation (TET) proteins, which contain catalytic domains belonging to the 2-oxoglutarate dependent dioxygenase family. In various mammalian cells/tissues including embryonic stem cells, cancer cells and brain tissues, it has been confirmed that these proteins are able to induce the stepwise oxidization of 5-methyl cytosine to 5-hydroxymethylcytosine (5hmC), 5-formylcytosine (5fC), and finally 5-carboxylcytosine (5caC). Each stage from initial methylation until the end of the DNA demethylation process is considered as a specific epigenetic mark that may regulate gene expression. This review discusses controversial evidence for the presence of such oxidative products, particularly 5hmC, in various plant species. Whereas some reports suggest no evidence for enzymatic DNA demethylation, other reports suggest that the presence of oxidative products is followed by the active demethylation and indicate the contribution of possible TET-like proteins in the regulation of gene expression in plants. The review also summarizes the results obtained by expressing the human TET conserved catalytic domain in transgenic plants.

RDNA Clusters Make Contact with Genes that Are Involved in Differentiation and Cancer and Change Contacts after Heat Shock Treatment.

Human rDNA clusters form numerous contacts with different chromosomal regions as evidenced by chromosome conformation capture data. Heterochromatization of rDNA genes leads to heterochromatization in different chromosomal regions coupled with the activation of the transcription of genes related to differentiation. These data suggest a role for rDNA clusters in the regulation of many human genes. However, the genes that reside within the rDNA-contacting regions have not been identified. The purpose of this study was to detect and characterize the regions where rDNA clusters make frequent contacts and to identify and categorize genes located in these regions. We analyzed the regions that contact rDNA using 4C data and show that these regions are enriched with genes specifying transcription factors and non-coding RNAs involved in differentiation and development. The rDNA-contacting genes are involved in neuronal development and are associated with different cancers. Heat shock treatment led to dramatic changes in the pattern of rDNA-contacting sites, especially in the regions possessing long stretches of H3K27ac marks. Whole-genome analysis of rDNA-contacting sites revealed specific epigenetic marks and the transcription sites of 20–100 nt non-coding RNAs in these regions. The rDNA-contacting genes jointly regulate many genes that are involved in the control of transcription by RNA polymerase II and the development of neurons. Our data suggest a role for rDNA clusters in the differentiation of human cells and carcinogenesis.

125 - Altered DNA Methylation and Serum Levels of Metabolites is Associated With Type 2 Diabetes in Adolescents

Worldwide, it is currently estimated that 425 million adults have type 2 diabetes (T2D) and rates of T2D are also increasing among adolescents. Exposure to diabetes during pregnancy is strongly associated with early onset obesity, dysglycemia and T2D in the offspring. One current theory for the trend of rising T2D among children is that more women in their childbearing years are overweight and at risk of diabetes during pregnancy. The mechanisms involved are not understood, but the development of T2D in the offspring years after the initial exposure to diabetes in utero suggests the possible involvement of epigenetics, a form of cellular memory. One specific epigenetic mark, DNA methylation, is established in utero. Thus, DNA methylation could link in utero exposure to diabetes during pregnancy to gene expression patterns that affect the risk of T2D development in the offspring.

The Preliminary Study of Pesticide Mospilan Effect on the GSTP1 Gene Methylation in Bovine Lymphocytes

Abstract The epigenetic mechanisms represent a dynamic, reversible and heritable manner modulating gene expression during the life cycle of an animal organism. They generate the specific epigenetic marks which constitute so-called epigenome. One of the most studied epigenetic mechanisms/marks is DNA methylation which is, similarly as the whole epigenome, susceptible to environmental and nutritional influences. The aberrations of the DNA methylation profile may alter gene expression leading to pathologic consequences. Pesticides along with their pest-reducing effects may also negatively affect non-target organisms. In our preliminary study, we investigated an effect of the pesticide Mospilan on the DNA methylation of the bovine GSTP1 gene which plays an important role in the cell detoxification processes. The specific primers for the GSTP1 Methylation-specific PCR (MSP) analysis were proposed and tested with the DNA from the Mospilan-treated bovine lymphocytes. It seems that the pesticide with the concentration of 100 µg.ml−1 did not induce DNA methylation changes in GSTP1 gene in bovine lymphocytes.

Identification of epilepsy related pathways using genome-wide DNA methylation measures: A trio-based approach.

Genetic generalized epilepsies (GGE) are genetically determined, as their name implies and they are clinically characterized by generalized seizures involving both sides of the brain in the absence of detectable brain lesions or other known causes. GGEs are yet complex and are influenced by many different genetic and environmental factors. Methylation specific epigenetic marks are one of the players of the complex epileptogenesis scenario leading to GGE. In this study, we have set out to perform genome-wide methylation profiling to analyze GGE trios each consisting of an affected parent-offspring couple along with an unaffected parent. We have developed a novel scoring scheme within trios to categorize each locus analyzed as hypo or hypermethylated. This stringent approach classified differentially methylated genes in each trio and helped us to produce trio specific and pooled gene lists with inherited and aberrant methylation levels. In order to analyze the methylation differences from a boarder perspective, we performed enrichment analysis with these lists using the PANOGA software. This collective effort has led us to detect pathways associated with the GGE phenotype, including the neurotrophin signaling pathway. We have demonstrated a trio based approach to genome-wide DNA methylation analysis that identified individual and possibly minor changes in methylation marks that could be involved in epileptogenesis leading to GGE.

Data Access and Interactive Visualization of Whole Genome Sequence of Sickle Cell Patients within the St. Jude Cloud

With the increase in availability of high depth whole genome sequencing (WGS) data of individuals with sickle cell disease (SCD), easy access to the raw sequencing data remains an issue due to technical and regulatory challenges. A compliant system that can provide facile data access would accelerate scientific discovery of genetic variants associated with clinical phenotypes. Cloud storage and computing provide an ultimate solution to this data access, which we have shown through the St. Jude Cloud (https://stjude.cloud) where over 5000 whole genome sequences for pediatric cancer patients are being shared in collaboration with DNANexus and Microsoft. Here we expand the St. Jude Cloud to sickle cell disease data through the Sickle Genome Project (SGP) Data Portal (https://pecan.stjude.org/permalink/sgp) to allow instantaneous raw data access (following data access committee approval), as well as visualization of genotype calls at individual level in a novel genome. The SGP WGS data was generated from 871 patients from St. Jude Children's Research Hospital (St. Jude) through the Sickle Cell Clinical Research and Intervention Program (SCCRIP, Pediatr Blood Cancer. 2018 May 24: e27228) and from Baylor College of Medicine (BCM). All study participants provided informed consent for genomic study and data sharing on IRB-approved research protocols.The SGP data portal will have multi-tiered access. All users will have access to a general heat map view which shows anonymized patient clinical values (e.g., fetal hemoglobin (HbF), mean corpuscular volume (MCV), hemoglobin concentration (Hb)) and relevant SCD modifying variants (e.g., Beta-globin locus, MYB, BCL11A, HBA). The GenomePaint bowser allows for viewing coding and noncoding variants. Displayed with each variant will be a visual indication of the median fetal hemoglobin values for patients homozygous for the reference allele, heterozygous, or homozygous for the alternative allele. The browser also displays erythroid specific DNA-accessibility and epigenetic marks and indicates variant that may disrupt erythroid specific transcription factor binding sites (GATA1 and BCL11A). For anonymization purposes, within the genome browser and heat map views, clinical values and the patients age will be binned into ranges when displayed as single or low count values. Lastly, the ProteinPaint tool (Zhang and Zhou, Nature Gen, Dec 29, 2015) will enable visualization and filtering of variants with reference to protein domain and amino acid sequence.To access processed data such as BAM and VCF files for downstream analyses, a user will be required to apply for access which will be adjudicated by a data access committee. Verified researchers will be granted access to clinical data in a manner consistent with the protocol specific informed consent documentation and protocol under which the sequencing was performed. This may include coded clinical and demographic data when specified by the research protocol and informed consentThe SGP data set will be one of the first WGS datasets from primarily African American Sickle cell patients to be made available to clinicians and researchers worldwide. In addition, no SCD-centric data portal exists that contains controlled access to data and provides graphical tools for visual analysis. The combination of the visual tools and ability to download tools provides the scientific community an invaluable resource for studying sickle cell disease. DisclosuresEstepp:Daiichi Sankyo: Consultancy; NHLBI: Research Funding; Global Blood Therapeutics: Consultancy, Research Funding; ASH Scholar: Research Funding. Hankins:Global Blood Therapeutics: Research Funding; bluebird bio: Consultancy; NCQA: Consultancy; Novartis: Research Funding.

From 1D sequence to 3D chromatin dynamics and cellular functions: a phase separation perspective.

The high-order chromatin structure plays a non-negligible role in gene regulation. However, the mechanism, especially the sequence dependence for the formation of varied chromatin structures in different cells remains to be elucidated. As the nucleotide distributions in human and mouse genomes are highly uneven, we identified CGI (CpG island) forest and prairie genomic domains based on CGI densities of a species, dividing the genome into two sequentially, epigenetically, and transcriptionally distinct regions. These two megabase-sized domains also spatially segregate to different extents in different cell types. Forests and prairies show enhanced segregation from each other in development, differentiation, and senescence, meanwhile the multi-scale forest-prairie spatial intermingling is cell-type specific and increases in differentiation, helping to define cell identity. We propose that the phase separation of the 1D mosaic sequence in space serves as a potential driving force, and together with cell type specific epigenetic marks and transcription factors, shapes the chromatin structure in different cell types. The mosaicity in genome of different species in terms of forests and prairies could relate to observations in their biological processes like development and aging. In this way, we provide a bottoms-up theory to explain the chromatin structural and epigenetic changes in different processes.

Abstract 480: Injury-Activated Vascular Cells Share a Common Photonic Fingerprint with Stem Cell-Derived Myogenic Progeny Following Interrogation Using a Lab-on-a-Disc (Load) Platform

The accumulation of vascular smooth muscle (SMC)-like cells within the intima contributes significantly to intimal medial thickening (IMT) and vascular remodeling typical of arteriosclerotic disease. Light has emerged as a powerful tool to interrogate cells label-free and facilitates discriminant observations both in vitro and in vivo . The auto-fluorescence (AF) profile of individual cells isolated from arteriosclerotic vessels, captured on V-cup array and interrogated across five wavelengths using a novel Lab-on-a-Disc platform, was significantly increased at the 565 ± 20nm wavelength concomitant with a reduction in Myh11 expression, when compared to differentiated vascular smooth muscle (SMC) cells from control vessels. In vitro, TGF-β1 promoted myogenic differentiation of murine bone-marrow derived Sca1 + /CD44 + mesenchymal stem cells (MSC) and murine Sca1 + C3H 10T1/2 cells concomitant with enrichment of the specific SMC epigenetic histone mark, H3K4me2 at the Myh11 promoter, Myh11 promoter transactivation and increased SMC differentiation marker mRNA and protein expression. Myogenic differentiation resulted in a significant increase in the AF intensity across 565 ± 20nm wavelength, an effect not observed for TGF-β1 treated RAMOS human B lymphocytes but mimicked by Notch activation of resident Sca1 + multipotent vascular stem cells (MVSCs) with Jagged1 and inhibited following elastin and collagen III depletion, respectively. Moreover, the temporal increase in the AF intensity at 565 ± 20nm wavelength during myogenic differentiation was similar to the AF profile of dissociated cells from arteriosclerotic vessels at this same wavelength. These data suggest that an AF photonic fingerprint of stem cell-derived myogenic progeny in vitro mimics that of vascular cells ex vivo following injury.

Studying X chromosome inactivation in the single-cell genomic era.

Single-cell genomics is set to revolutionise our understanding of how epigenetic silencing works; by studying specific epigenetic marks or chromatin conformations in single cells, it is possible to ask whether they cause transcriptional silencing or are instead a consequence of the silent state. Here, we review what single-cell genomics has revealed about X chromosome inactivation, perhaps the best characterised mammalian epigenetic process, highlighting the novel findings and important differences between mouse and human X inactivation uncovered through these studies. We consider what fundamental questions these techniques are set to answer in coming years and propose that X chromosome inactivation is an ideal model to study gene silencing by single-cell genomics as technical limitations are minimised through the co-analysis of hundreds of genes.

Epigenetic regulation of neural stem cell differentiation towards spinal cord regeneration.

Severe spinal cord injury (SCI) leads to almost complete neural cell loss at the injured site, causing the irreversible disruption of neuronal circuits. The transplantation of neural stem or precursor cells (NS/PCs) has been regarded as potentially effective for SCI treatment because NS/PCs can compensate for the injured sites by differentiating into neurons and glial cells (astrocytes and oligodendrocytes). An understanding of the molecular mechanisms that regulate the proliferation, fate specification and maturation of NS/PCs and their progeny would facilitate the establishment of better therapeutic strategies for regeneration after SCI. In recent years, several studies of SCI animal models have demonstrated that the modulation of specific epigenetic marks by histone modifiers and non-coding RNAs directs the setting of favorable cellular environments that promote the neuronal differentiation of NS/PCs and/or the elongation of the axons of the surviving neurons at the injured sites. In this review, we provide an overview of recent progress in the epigenetic regulation/manipulation of neural cells for the treatment of SCI.

Fine-mapping inflammatory bowel disease loci to single-variant resolution.

SummaryThe inflammatory bowel diseases (IBD) are chronic gastrointestinal inflammatory disorders that affect millions worldwide. Genome-wide association studies have identified 200 IBD-associated loci, but few have been conclusively resolved to specific functional variants. Here we report fine-mapping of 94 IBD loci using high-density genotyping in 67,852 individuals. We pinpointed 18 associations to a single causal variant with >95% certainty, and an additional 27 associations to a single variant with >50% certainty. These 45 variants are significantly enriched for protein-coding changes (n=13), direct disruption of transcription factor binding sites (n=3) and tissue specific epigenetic marks (n=10), with the latter category showing enrichment in specific immune cells among associations stronger in CD and in gut mucosa among associations stronger in UC. The results of this study suggest that high-resolution fine-mapping in large samples can convert many GWAS discoveries into statistically convincing causal variants, providing a powerful substrate for experimental elucidation of disease mechanisms.

80 EFFECT OF BOVINE OVIDUCTAL FLUID ON DNA METHYLATION OF BOVINE BLASTOCYSTS PRODUCED IN VITRO

During the transit through the oviduct, the early embryo undergoes an epigenetic reprogramming of its genome, which induces changes in DNA methylation pattern. Given that epigenetic modifications are susceptible to environmental influence, the oviducal milieu may affects DNA methylation marks in the developing embryo. The aim of this study was to evaluate whether bovine oviducal fluid (OF) exerts an effect on methylation status of genomic regions at different time points of embryo development. In vitro-produced zygotes were cultured in SOF + 3 mg mL−1 BSA (control, C) or in SOF + 1.25% OF at 3 different time points: until 98 h post-insemination (hpi) (OF1–16: 1–16 cell), 52 hpi (OF1–8: 1–8 cell), or from 52 until 98 hpi (OF8–16: 8–16 cell). The OF used was acquired from Embryocloud (Murcia, Spain) from cow oviducts at the early luteal phase (Day 1–4). After, embryo culture took place in control medium up to Day 8. For all the groups, the speed of development was considered, and normal developing embryos that reached ≥6 cells at 52 hpi and ≥16 cells at 98 hpi were selected and separately cultured from slow developing embryos. Cleavage (52 hpi) and blastocyst yield (Day 7–8) were analysed by ANOVA (8 replicates). Expanding blastocysts (Day 7–8) from the normal developing groups were collected for bisulfite sequencing analysis. The DNA bisulfite conversion was performed with a MethylEdge Bisulfite Conversion System kit (Promega, WI, USA) in groups of 20 blastocysts obtained from 5 replicates. Methylation status was analysed on regions localised in 4 developmental important genes (MTERF2, ABCA7, OLFM1, and GMDS) and within 2 LINE L1 elements located on chromosomes 9 (L9) and 29 (L29). Methylation percentages (10 sequenced clones/group) were compared using statistical z-test. No significant differences were found on cleavage rate (C: 89.7 ± 1.0, OF1–16: 84.9 ± 1.7; OF1–8: 85.4 ± 1.9; OF8–16: 89.1 ± 1.9%) and blastocyst yield between normal developing embryos (C: 36.8 ± 5.3; OF1–16: 34.7 ± 3.7; OF1–8: 41.0 ± 3.8; OF8–16: 43.9 ± 5.1%). Blastocysts derived from all OF groups showed the CpG region of MTERF2 hypomethylated compared with C group (20.0, 26.2, and 32.9% v. 56.2%, respectively; P < 0.001). The CpG sequence of ABCA7 exhibited significant hypomethylation in embryos from OF1–16 group compared with OF1–8, OF8–16, and C groups (31.1 v. 56.8, 57.9, and 65.8%, respectively; P < 0.001). Although the methylation of the CpG region within OLFM1 did not differ between OF1–16 and C groups (24.1 v. 19.4%, respectively), embryos from OF1–8 group showed a highly methylated region (47.1%) compared with OF1–16 and C groups (P < 0.001). The CpG sequence on L9 showed a high methylation level in blastocysts derived from OF1–16 group compared with OF8–16 and C groups (36.4 v. 14.5 and 20.0%, respectively; P < 0.05). There were no differences in methylation marks between groups examined for CpG regions of GMDS and L29. These results indicated that embryos exhibit a temporal sensitivity to OF at early embryonic stages, which is reflected by DNA methylation changes of specific genes at blastocyst stage. This is the first report describing that OF could modify specific epigenetic marks of the bovine embryonic genome.

Computational inference of a genomic pluripotency signature in human and mouse stem cells.

Recent analyses of next-generation sequencing datasets have shown that cell-specific regulatory elements in stem cells are marked with distinguishable patterns of transcription factor (TF) binding and epigenetic marks. For example, we recently demonstrated that promoters of cell-specific genes are covered with expanded trimethylation of histone H3 at lysine 4 (H3K4me3) marks (i.e., broad H3K4me3 domains). Moreover, binding of specific TFs, such as OCT4, NANOG, and SOX2, have been shown to play a critical role in maintaining the pluripotency of stem cells. Despite these observations, a systematic exploration of genomic and epigenomic features of stem-cell-specific gene promoters has not been conducted. Advanced machine-learning models can capture distinguishable genomic and epigenomic characteristics of stem-cell-specific promoters by taking advantage of the wealth of publicly available datasets. Here, we propose a three-step framework to discover novel data characteristics of high-throughput next generation sequencing datasets that distinguish pluripotency genes in human and mouse embryonic stem cells (ESCs). Our framework involves: i) feature extraction to identify novel features of genomic datasets; ii) feature selection using a logistic regression model combined with the Least Absolute Shrinkage and Selection Operator (LASSO) method to find the most critical datasets and features; and iii) cross validation with features selected using LASSO method to assess the predictive power of selected data features in distinguishing pluripotency genes. We show that specific epigenetic marks, and specific features of these marks, are enriched at pluripotency gene promoters. Moreover, we also assess both the individual and combined effect of TF binding, epigenetic mark deposition, gene expression datasets for marking pluripotency genes. Our findings are consistent with the existence of a conserved, complex and integrative genomic signature in ESCs that can be exploited to flag important candidate pluripotency genes. They also validate our computational framework for fostering a deeper understanding of genomic datasets in stem cells, in the future, could be extended to study cell-type-specific genomic landscapes in other cell types.Reviewers: This article was reviewed by Zoltan Gaspari and Piotr Zielenkiewicz.Electronic supplementary materialThe online version of this article (doi:10.1186/s13062-016-0148-z) contains supplementary material, which is available to authorized users.

Punctuated chromatin states regulate Plasmodium falciparum antigenic variation at the intron and 2kb upstream regions.

BackgroundUnderstanding the regulation mechanism of var gene expression is crucial for explaining antigenic variation in Plasmodium falciparum. Recent work observed that while all var genes produce transcripts, only a few var genes exhibit high expression levels. However, the global regulation of var expression and the relationship between epigenetic and genetic control remains to be established.ResultWe have systematically reanalyzed the existing genomic data including chromatin configurations and gene expressions; and for the first time used robust statistical methods to show that the intron and 2 kb upstream regions of each endogenous var gene always maintain high chromatin accessibility, with high potential to bind transcription factors (TFs). The levels of transcripts for different var gene family members are associated with this chromatin accessibility. Any given var gene thus shows punctuated chromatin states throughout the asexual life cycle. This is demonstrated by three independent transcript datasets. Chromatin accessibility in the var intron and 2 kb upstream regions are also positively correlated with their GC content, suggesting the level of var genes silencing might be encoded in their intron sequences. Interestingly, both var intron and 2 kb upstream regions exhibit higher chromatin accessibility when the genes have relatively lower transcription levels, suggesting a punctuated repressive function for these regulatory elements.ConclusionBy integrating and analyzing epigenomic, genomic and transcriptomic data, our work reveals a novel distal element in var control. We found dynamic modulations of specific epigenetic marks around the var intron and distal upstream regions are involved in the general var gene expression patterns in malarial antigenic variation.Electronic supplementary materialThe online version of this article (doi:10.1186/s12864-016-3005-7) contains supplementary material, which is available to authorized users.