DNA methyltransferase expression in the human endometrium: down-regulation by progesterone and estrogen

Uterine ERα epigenetic modifications are induced by the endocrine disruptor endosulfan in female rats with impaired fertility

High ERα activity may disrupt the window of uterine receptivity, causing defective implantation. We investigated whether implantation failures prompted by endosulfan are associated with aberrant ERα uterine expression and DNA methylation status during the pre-implantation period. ERα-dependent target genes that play a crucial role in the uterine receptivity for embryo attachment and implantation were also investigated. Newborn female rats received corn oil (vehicle, Control), 6 μg/kg/d of endosulfan (Endo6) or 600 μg/kg/d of endosulfan (Endo600) on postnatal days (PND) 1, 3, 5, and 7. On PND90, females were made pregnant and on gestational day 5 (GD5, pre-implantation period) uterine samples were collected. ERα expression was assessed at protein and mRNA levels by immunohistochemistry and real time RT-PCR, respectively. ERα transcript variants mRNA containing alternative 5'-untranslated regions (5'UTRs) were also evaluated. We searched for predicted transcription factors binding sites in ERα regulatory regions and assessed their methylation status by Methylation-Sensitive Restriction Enzymes-PCR technique (MSRE-PCR). The expression of the ERα-dependent uterine target genes, i.e. mucin-1 (MUC-1), insulin-like growth factor-1 (IGF-1), and leukemia inhibitory factor (LIF), was assessed by real time RT-PCR. Both doses of endosulfan increased the expression of ERα and its transcript variants ERα-OS, ERα-O, ERα-OT and ERα-E1. Moreover, a decreased DNA methylation levels were detected in some ERα regulatory regions, suggesting an epigenetic up-regulation of it transcription. ERα overexpression was associated with an induction of its downstream genes, MUC-1 and IGF-1, suggesting that endosulfan might alter the uterine estrogenic pathway compromising uterine receptivity. These alterations could account, at least in part, for the endosulfan-induced implantation failures.

Oral Contraceptive Use May Modulate Global Genomic DNA Methylation and Promoter Methylation of APC1 and ESR1

Background:

There are challenging reports in the public health sphere regarding associations between oral contraceptive (OC) use and cancer risk.

Methods:

To evaluate possible effects of OCs on cancer susceptibility, we quantified of global 5-methyl cytosine (5-mC) levels and assessed methylation patterns of CpG islands of two key tumor suppressor genes, APC1 and ESR1, in serum of users by enzyme-linked immunosorbent assay and methylation specific PCR methods, respectively.

Results:

Our results indicated that OCs significantly decrease the level of global DNA methylation in users relative to control non-users. However, our data revealed no significant differences between CpG island methylation patterns for ESR1 and APC1 in healthy control and OC-treated women. However, we did find a trend for hypermethylation of both tumor suppressor genes in OC users.

Conclusion:

Our data suggest that the level of 5-mC but not individual CpG island patterns is significantly influenced by OCs in our cross-section of adult users.

Emerging role for dysregulated decidualization in the genesis of preeclampsia

In normal human placentation, uterine invasion by trophoblast cells and subsequent spiral artery remodeling depend on cooperation among fetal trophoblasts and maternal decidual, myometrial, immune and vascular cells in the uterine wall. Therefore, aberrant function of anyone or several of these cell-types could theoretically impair placentation leading to the development of preeclampsia. Because trophoblast invasion and spiral artery remodeling occur during the first half of pregnancy, the molecular pathology of fetal placental and maternal decidual tissues following delivery may not be informative about the genesis of impaired placentation, which transpired months earlier. Therefore, in this review, we focus on the emerging prospective evidence supporting the concept that deficient or defective endometrial maturation in the late secretory phase and during early pregnancy, i.e., pre-decidualization and decidualization, respectively, may contribute to the genesis of preeclampsia. The first prospectively-acquired data directly supporting this concept were unexpectedly revealed in transcriptomic analyses of chorionic villous samples (CVS) obtained during the first trimester of women who developed preeclampsia 5 months later. Additional supportive evidence arose from investigations of Natural Killer cells in first trimester decidua from elective terminations of women with high resistance uterine artery indices, a surrogate for deficient trophoblast invasion. Last, circulating insulin growth factor binding protein-1, which is secreted by decidual stromal cells was decreased during early pregnancy in women who developed preeclampsia. We conclude this review by making recommendations for further prospectively-designed studies to corroborate the concept of endometrial antecedents of preeclampsia. These studies could also enable identification of women at increased risk for developing preeclampsia, unveil the molecular mechanisms of deficient or defective (pre)decidualization, and lead to preventative strategies designed to improve (pre)decidualization, thereby reducing risk for preeclampsia development.

Epigenetics in endometrial carcinogenesis - part 1: DNA methylation

Carcinogenesis is a multistep multifactorial process that involves the accumulation of genetic and epigenetic alterations. In the past two decades, there has been an exponential growth of knowledge establishing the importance of epigenetic changes in cancer. Our work focused on reviewing the main role of epigenetics in the pathogenesis of endometrial carcinoma, highlighting the reported results concerning each epigenetic mechanistic layer. The present review is the first part of this work, in which we examined the contribution of DNA methylation alterations for endometrial carcinogenesis.

Role of Oxidative Stress in Epigenetic Modification in Endometriosis

Aberrant DNA methylation and histone modification are associated with an increased risk of reproductive disorders such as endometriosis. However, a cause-effect relationship between epigenetic mechanisms and endometriosis development has not been fully determined. This review provides current information based on oxidative stress in epigenetic modification in endometriosis. This article reviews the English-language literature on epigenetics, DNA methylation, histone modification, and oxidative stress associated with endometriosis in an effort to identify epigenetic modification that causes a predisposition to endometriosis. Oxidative stress, secondary to the influx of hemoglobin, heme, and iron during retrograde menstruation, is involved in the expression of CpG demethylases, ten-eleven translocation, and jumonji (JMJ). Ten-eleven translocation and JMJ recognize a wide range of endogenous DNA methyltransferases (DNMTs). The increased expression levels of DNMTs may be involved in the subsequent downregulation of the decidualization-related genes. This review supports the hypothesis that there are at least 2 distinct phases of epigenetic modification in endometriosis: the initial wave of iron-induced oxidative stress would be followed by the second big wave of epigenetic modulation of endometriosis susceptibility genes. We summarize the recent advances in our understanding of the underlying epigenetic mechanisms focusing on oxidative stress in endometriosis.

Associations of LEP, CRH, ICAM-1, and LINE-1 methylation, measured in saliva, with waist circumference, body mass index, and percent body fat in mid-childhood

BACKGROUND

Genetics explains a small proportion of variance in body mass index at the population level. Epigenetics, commonly measured by gene methylation, holds promise for understanding obesity risk factors and mechanisms.

METHODS

Participants were 431 adolescents aged 10-15 years. BMI z-score, waist circumference z-score, and percent body fat were measured. Saliva samples were collected and methylation of promoter regions of four candidate genes or sequences (LEP, ICAM-1, CRH, and LINE-1) were measured in 3-4 CpG sites each. Linear regression was used to identify associations of methylation with obesity-related outcomes.

RESULTS

After adjusting for age, in sex-stratified analysis, the three obesity-related outcomes were negatively associated with LEP methylation in obese boys only. There were no associations of methylation of the other genes or sequences and the obesity-related outcomes.

CONCLUSIONS

Our results are consistent with prior studies that reported sex differences in associations of obesity-related outcomes with LEP methylation, and also as would be expected in adipose tissue, the source of circulating leptin. The findings suggest that saliva might be an acceptable tissue for epigenetics studies in adolescents.

Periconceptional undernutrition affects in utero methyltransferase expression and steroid hormone concentrations in uterine flushings and blood plasma during the peri-implantation period in domestic pigs

Female undernutrition during early pregnancy may affect the physiological pattern of genomic DNA methylation. We hypothesised that in utero DNA methylation may be impaired in females fed a restrictive diet in early pregnancy. In this study we evaluated whether poor maternal nutritional status, induced by applying a restricted diet during the peri-conceptional period, may influence: (1) the potential for in utero DNA methylation, expressed as changes in the mRNA expression and protein abundance of methyltransferases: DNA methyltransferase 1 (DNMT1) and DNMT3a in the endometrium and the myometrium, (2) the intrauterine microenvironment, measured as oestradiol 17β (E2) and progesterone (P4) concentrations in uterine flushings and (3) plasma concentration of E2 and P4 during the peri-implantation period. Our results indicate that maternal peri-conceptional undernutrition affects maintenance and de novo DNA methylation in the endometrium, de novo methylation in the myometrium and a results in a decrease in intrauterine E2 concentration during the peri-implantation period. The intrauterine concentration of P4 and plasma concentrations of E2 and P4 did not change. These findings suggest that undernutrition during the earliest period of pregnancy, and perhaps the pre-pregnancy period, may create changes in epigenetic mechanisms in the uterus and intrauterine milieu of E2 during the peri-implantation period.

Imprinted and DNA methyltransferase gene expression in the endometrium during the pre- and peri-implantation period in cattle

The endometrium plays a key role in providing an optimal environment for attachment of the preimplantation embryo during the early stages of pregnancy. Investigations over the past 2 decades have demonstrated that vital epigenetic processes occur in the embryo during the preimplantation stages of development. However, few studies have investigated the potential role of imprinted genes and their associated modulators, the DNA methyltransferases (DNMTs), in the bovine endometrium during the pre- and peri-implantation period. Therefore, in the present study we examined the expression profiles of the DNMT genes (3A, 3A2 and 3B) and a panel of the most comprehensively studied imprinted genes in the endometrium of cyclic and pregnant animals. Intercaruncular (Days 5, 7, 13, 16 and 20) and caruncular (Days 16 and 20) regions were analysed for gene expression changes, with protein analysis also performed for DNMT3A, DNMT3A2 and DNMT3B on Days 16 and 20. An overall effect of day was observed for expression of several of the imprinted genes. Tissue-dependent gene expression was detected for all genes at Day 20. Differences in DNMT protein abundance were mostly observed in the intercaruncular regions of pregnant heifers at Day 16 when DNMT3A, DNMT3A2 and DNMT3B were all lower when compared with cyclic controls. At Day 20, DNMT3A2 expression was lower in the pregnant caruncular samples compared with cyclic animals. This study provides evidence that epigenetic mechanisms in the endometrium may be involved with implantation of the embryo during the early stages of pregnancy in cattle.

Abnormal Uterine Bleeding Is Associated With Increased BMP7 Expression in Human Endometrium

Abnormal uterine bleeding (AUB), a common health concern of women, is a heterogeneous clinical entity that is traditionally categorized into organic and nonorganic causes. Despite varied pharmacologic treatments, few offer sustained efficacy, as most are empiric, unfocused, and do not directly address underlying dysregulated molecular mechanisms. Characterization of such molecular derangements affords the opportunity to develop and use novel, more successful treatments for AUB. Given its implication in other organ systems, we hypothesized that bone morphogenetic protein (BMP) expression is altered in patients with AUB and hence comprehensively investigated dysregulation of BMP signaling pathways by systematically screening 489 samples from 365 patients for differences in the expression of BMP2, 4, 6, and 7 ligands, BMPR1A and B receptors, and downstream SMAD4, 6, and 7 proteins. Expression analysis was correlated clinically with data abstracted from medical records, including bleeding history, age at procedure, ethnicity, body mass index, hormone treatment, and histological diagnosis of fibroids, polyps, adenomyosis, hyperplasia, and cancer. Expression of BMP7 ligand was significantly increased in patients with AUB (H-score: 18.0 vs 26.7; P < .0001). Patients reporting heavy menstrual bleeding (menorrhagia) as their specific AUB pattern demonstrated significantly higher BMP7 expression. Significantly, no differences in the expression of any other BMP ligands, receptors, or SMAD proteins were observed in this large patient cohort. However, expression of BMPR1A, BMPR1B, and SMAD4 was significantly decreased in cancer compared to benign samples. Our study demonstrates that BMP7 is a promising target for future investigation and pharmacologic treatment of AUB.

Gene Methylation and Cytological Atypia in Random Fine-Needle Aspirates for Assessment of Breast Cancer Risk

Methods to determine individualized breast cancer risk lack sufficient sensitivity to select women most likely to benefit from preventive strategies. Alterations in DNA methylation occur early in breast cancer. We hypothesized that cancer-specific methylation markers could enhance breast cancer risk assessment. We evaluated 380 women without a history of breast cancer. We determined their menopausal status or menstrual cycle phase, risk of developing breast cancer (Gail model), and breast density and obtained random fine-needle aspiration (rFNA) samples for assessment of cytopathology and cumulative methylation index (CMI). Eight methylated gene markers were identified through whole-genome methylation analysis and included novel and previously established breast cancer detection genes. We performed correlative and multivariate linear regression analyses to evaluate DNA methylation of a gene panel as a function of clinical factors associated with breast cancer risk. CMI and individual gene methylation were independent of age, menopausal status or menstrual phase, lifetime Gail risk score, and breast density. CMI and individual gene methylation for the eight genes increased significantly (P < 0.001) with increasing cytological atypia. The findings were verified with multivariate analyses correcting for age, log (Gail), log (percent density), rFNA cell number, and body mass index. Our results demonstrate a significant association between cytological atypia and high CMI, which does not vary with menstrual phase or menopause and is independent of Gail risk and mammographic density. Thus, CMI is an excellent candidate breast cancer risk biomarker, warranting larger prospective studies to establish its utility for cancer risk assessment. Cancer Prev Res; 9(8); 673-82. ©2016 AACR.

A mass spectrometric insight into the origins of benign gynecological disorders

Applications of mass spectrometry (MS) are rapidly expanding and encompass molecular and cellular biology. MS aids in the analysis of in vivo global molecular alterations, identifying potential biomarkers which may improve diagnosis and treatment of various pathologies. MS has added new dimensionality to medical research. Pioneering gynecologists now study molecular mechanisms underlying female reproductive pathology with MS-based tools. Although benign gynecologic disorders including endometriosis, adenomyosis, leiomyoma, and polycystic ovarian syndrome (PCOS) carry low mortality rates, they cause significant physical, mental, and social detriments. Additionally, some benign disorders are unfortunately associated with malignancies. MS-based technology can detect malignant changes in formerly benign proteomes and metabolomes with distinct advantages of speed, sensitivity, and specificity. We present the use of MS in proteomics and metabolomics, and summarize the current understanding of the molecular pathways concerning female reproductive anatomy. Highlight discoveries of novel protein and metabolite biomarkers via MS-based technology, we underscore the clinical application of these techniques in the diagnosis and management of benign gynecological disorders. © 2015 Wiley Periodicals, Inc. Mass Spec Rev 36:450-470, 2017.

Epigenetic regulations through DNA methylation and hydroxymethylation: clues for early pregnancy in decidualization

DNA methylation at cytosines is an important epigenetic modification that participates in gene expression regulation without changing the original DNA sequence. With the rapid progress of high-throughput sequencing techniques, whole-genome distribution of methylated cytosines and their regulatory mechanism have been revealed gradually. This has allowed the uncovering of the critical roles played by DNA methylation in the maintenance of cell pluripotency, determination of cell fate during development, and in diverse diseases. Recently, rediscovery of 5-hydroxymethylcytosine, and other types of modification on DNA, have uncovered more dynamic aspects of cell methylome regulation. The interaction of DNA methylation and other epigenetic changes remodel the chromatin structure and determine the state of gene transcription, not only permanently, but also transiently under certain stimuli. The uterus is a reproductive organ that experiences dramatic hormone stimulated changes during the estrous cycle and pregnancy, and thus provides us with a unique model for studying the dynamic regulation of epigenetic modifications. In this article, we review the current findings on the roles of genomic DNA methylation and hydroxymethylation in the regulation of gene expression, and discuss the progress of studies for these epigenetic changes in the uterus during implantation and decidualization.

Aberrant expression and localization of deoxyribonucleic acid methyltransferase 3B in endometriotic stromal cells

OBJECTIVE

To define the expression and function of DNA methyltransferases (DNMTs) in response to decidualizing stimuli in endometriotic cells compared with healthy endometrial stroma.

DESIGN

Basic science.

SETTING

University research center.

PATIENT(S)

Premenopausal women with or without endometriosis.

INTERVENTION(S)

Primary cultures of stromal cells from healthy endometrium (E-IUM) or endometriomas (E-OSIS) were subjected to in vitro decidualization (IVD) using 1 μM medroxyprogesterone acetate, 35 nM 17β-estradiol, and 0.05 mM 8-Br-cAMP.

MAIN OUTCOME MEASURE(S)

Expression of DNMT1, DNMT3A, and DNMT3B in E-IUM and E-OSIS were assessed by quantitative real-time polymerase chain reaction and immunoblotting. Recruitment of DNMT3B to the promoters of steroidogenic factor 1 (SF-1) and estrogen receptor α (ESR1) was examined by chromatin immunoprecipitation.

RESULT(S)

IVD treatment reduced DNMT3B messenger RNA (74%) and protein levels (81%) only in E-IUM; DNMT1 and DNMT3A were unchanged in both cell types. Significantly more DNMT3B bound to the SF-1 promoter in E-IUM compared with E-OSIS, and IVD treatment reduced binding in E-IUM to levels similar to those in E-OSIS. Enrichment of DNMT3B across 3 ESR1 promoters was reduced in E-IUM after IVD, although the more-distal promoter showed increased DNMT3B enrichment in E-OSIS after IVD.

CONCLUSION(S)

The inability to downregulate DNMT3B expression in E-OSIS may contribute to an aberrant epigenetic fingerprint that misdirects gene expression in endometriosis and contributes to its altered response to steroid hormones.

Sex-specific associations of arsenic exposure with global DNA methylation and hydroxymethylation in leukocytes: results from two studies in Bangladesh

BACKGROUND

Depletion of global 5-hydroxymethylcytosine (5-hmC) is observed in human cancers and is strongly implicated in skin cancer development. Although arsenic (As)-a class I human carcinogen linked to skin lesion and cancer risk-is known to be associated with changes in global %5-methylcytosine (%5-mC), its influence on 5-hmC has not been widely studied.

METHODS

We evaluated associations of As in drinking water, urine, and blood with global %5-mC and %5-hmC in two studies of Bangladeshi adults: (i) leukocyte DNA in the Nutritional Influences on Arsenic Toxicity study (n = 196; 49% male, 19-66 years); and (ii) peripheral blood mononuclear cell DNA in the Folate and Oxidative Stress study (n = 375; 49% male, 30-63 years).

RESULTS

Overall, As was not associated with global %5-mC or %5-hmC. Sex-specific analyses showed that associations of As exposure with global %5-hmC were positive in males and negative in females (P for interaction < 0.01). Analyses examining interactions by elevated plasma total homocysteine (tHcys), an indicator of B-vitamin deficiency, found that tHcys also modified the association between As and global %5-hmC (P for interaction < 0.10).

CONCLUSION

In two samples, we observed associations between As exposure and global %5-hmC in blood DNA that were modified by sex and tHcys.

IMPACT

Our findings suggest that As induces sex-specific changes in 5-hmC, an epigenetic mark that has been associated with cancer. Future research should explore whether altered %5-hmC is a mechanism underlying the sex-specific influences of As on skin lesion and cancer outcomes.

DNA methylation as a dynamic regulator of development and disease processes: spotlight on the prostate

Prostate development, benign hyperplasia and cancer involve androgen and growth factor signaling as well as stromal-epithelial interactions. We review how DNA methylation influences these and related processes in other organ systems such as how proliferation is restricted to specific cell populations during defined temporal windows, how androgens elicit their actions and how cells establish, maintain and remodel DNA methylation in a time and cell specific fashion. We also discuss mechanisms by which hormones and endocrine disrupting chemicals reprogram DNA methylation in the prostate and elsewhere and examine evidence for a reawakening of developmental epigenetic pathways as drivers of prostate cancer and benign prostate hyperplasia.

Folate deficiency impairs decidualization and alters methylation patterns of the genome in mice

Existing evidence suggests that adverse pregnancy outcomes are closely related with dietary factors. Previous studies in mice have focused on the harm of folate deficiency (FD) on development of embryo, while the effect of low maternal folate levels on maternal intrauterine environment during early pregnancy remains unclear. Since our previous study found that FD treatment of mice causes no apparent defects in embryo implantation but is accompanied by female subfertility, we next chose to investigate a potential role of FD on molecular events after implantation. We observed that the decidual bulges began to be stunted on pregnancy day 6. The results of functional experiments in vivo and in vitro showed that FD inhibited the process of endometrial decidualization. It has been confirmed that DNA methylation participates in decidualization, and folate as a methyl donor could change the methylation patterns of genes. Thus, we hypothesized that FD impairs maternal endometrial decidualization by altering the methylation profiles of related genes. Reduced representation bisulphite sequencing was carried out to detect the methylation profiles of endometrium on pregnancy day 6-8, which is equivalent to the decidualization period in mice. The results confirmed that FD changes the methylation patterns of genome, and GO analysis of the differentially methylated regions revealed that the associated genes mainly participate in biological adhesion, biological regulation, cell proliferation, development, metabolism and signalling. In addition, we found some candidates for regulators of decidual transformation, such as Nr1h3 and Nr5a1. The data indicate that FD inhibits decidualization, possibly by altering methylation patterns of the genome in mice.

Retinoic acid has the potential to suppress endometriosis development

Background

Despite endometriosis is common estrogen dependent disease afflicting women in reproductive age, the pathogenesis has not been fully elucidated. Retinoic acid has various functions in cells as biologic modulator, and aberrant retinoid metabolism seems to be involved in the lesions of endometriosis. In order to evaluate the potential of all-trans retinoic acid (ATRA) for therapeutic treatment, a transcriptome analysis and estradiol measurements in cultured endometriotic cells and tissues were conducted.

Methods

The mRNA expression levels in ATRA-treated endometriotic stromal cells (ESC) isolated from ovarian endometrial cysts (OEC) were investigated. Estradiol production in OEC tissues was also investigated.

Results

In the isolated ESC culture supplemented with ATRA for four days, total RNA was extracted followed by a transcriptome analysis using GeneChip. Forty-nine genes were upregulated and four genes were down-regulated by the ATRA treatment. Many upregulated genes were associated with the negative regulation of cellular proliferation. In addition, ATRA treatment decreased the mRNA expression of 17-beta-dehydrogenase 2 (HSD17B2) which converts estradiol into estrone in a dose-dependent manner, and the ELISA measurements indicated that estradiol production in the OEC tissue was inhibited by ATRA treatment.

Conclusions

Retinoic acid has the potential to suppress endometriosis development.

Hypoxia mimetic deferoxamine influences the expression of histone acetylation- and DNA methylation-associated genes in osteoblasts

PURPOSE OF THE STUDY

Sufficient oxygen supply to bone tissue is essential for normal bone development and efficient bone repair. Hypoxia and hypoxia-inducible factor 1α (HIF1α) signaling pathway have been shown to exhibit profound effects on proliferation, differentiation as well as gene and protein expression in osteoblasts, osteoclasts and mesenchymal stem cells; however, as epigenetic mechanisms also perform an important regulatory role in these cells, our aim was to elucidate whether hypoxia mimetic deferoxamine could influence epigenetic mechanisms in bone cells by modulating the gene expression levels of chromatin-modifying enzymes.

MATERIALS AND METHODS

Osteoblast cell line HOS was exposed to deferoxamine, a widely used hypoxia mimetic, and expression profile of 40 genes associated with histone acetylation, deacetylation and DNA methylation was determined using quantitative real time polymerase chain reaction (qPCR) array followed by individual qPCR analyses. In addition, genes associated with hypoxia response, RANK/RANKL/OPG system, WNT/β-catenin signaling pathway and oxidative stress were also analyzed.

RESULTS

We observed induced expression of histone deacetylase 9 (HDAC9) and suppressed expression of K(lysine) acetyltransferase 5 (KAT5) and DNA methyltransferase 3A (DNMT3A) demonstrating for the first time that expression of genes encoding chromatin-modifying enzymes could be influenced by hypoxia mimetic in HOS cells.

CONCLUSIONS

Based on our results we can conclude that hypoxia mimetic deferoxamine influences expression of histone acetylation- and DNA methylation-associated genes in osteoblasts and that further studies of hypoxia-induced epigenetic changes in bone cells should be undertaken.

Effects of atrazine and chlorpyrifos on DNA methylation in the brain and gonad of the common carp

DNA methylation is known to play an important role in the regulation of gene expression in animal. The purpose of the present study was to examine the effect of atrazine (ATR), chlorpyrifos (CPF) and combined ATR/CPF exposure on DNA methylation in the brain and gonad of common carp (Cyprinus carpio L.). The carp were sampled after a 40-d exposure to CPF and ATR, individually or in combination, followed by a 40-d recovery to measure the levels of global DNA methylation and the expression of methylation enzymes (DNA methyltransferases (DNMTs) and methylcytosine binding domain 2 (MBD2)) in the brain and gonad tissues. The results revealed that a significant global DNA hypomethylation in the common carp exposed to ATR, CPF and their mixture was observed compared to the control fish. The MBD2 mRNA expression was up-regulated in the brain and gonad of the common carp exposed to ATR, CPF and their mixture, in contrast, the DNMTs mRNA expression was down-regulated. The information regarding the effects of ATR and CPF on DNA methylation status generated in this study is important for pesticides toxicology evaluation. However, the effect of ATR and CPF on the methylation status of specific genes, as well as its detailed mechanism requires further investigation.

17β-oestradiol enhances global DNA hypomethylation in CD4-positive T cells from female patients with lupus, through overexpression of oestrogen receptor-α-mediated downregulation of DNMT1

BACKGROUND

Systemic lupus erythematosus (SLE) affects primarily women, and oestrogen appears to play a significant role in SLE development. Our previous studies showed that inhibition of DNA methyltransferase 1 (DNMT1) enhanced global DNA hypomethylation in CD4+ T cells isolated from patients with SLE, and exacerbated SLE. However, the effects of 17β-oestradiol on global DNA hypomethylation and DNMT1 expression in CD4+ T cells of female patients with SLE remain largely unknown.

AIM

To investigate the ability of 17β-oestradiol to affect global DNA methylation in female SLE CD4+ T cells and the mechanism(s) underlying this ability.

METHODS

We enrolled 30 women with SLE and 15 controls. CD4+ T cells exposed to 17β-oestradiol were analysed by global DNA methylation measurements, western blotting and real-time PCR. Plasma 17β-oestradiol levels were measured by ELISA.

RESULTS

In female SLE CD4+ T cells, 17β-oestradiol downregulated DNMT1 expression at both the mRNA and protein levels, and enhanced global DNA hypomethylation. Plasma 17β-oestradiol levels were similar in patients with SLE and controls. The mRNA expression of oestrogen receptor (ER)α, but not of ERβ, was upregulated in SLE CD4+ T cells. Furthermore, the 17β-oestradiol-induced downregulation of DNMT1 expression and global DNA hypomethylation were rescued by an ER antagonist.

CONCLUSIONS

17β-oestradiol enhances global DNA hypomethylation in female SLE CD4+ T cells via downregulation of DNMT1 mediated by ERα overexpression.

GnRH analogues may increase endometrial Hoxa10 promoter methylation and affect endometrial receptivity

The present study aimed to investigate whether gonadotropin-releasing hormone analogues (GnRH-as), including GnRH agonists and antagonists, affect endometrial homeobox (Hox) a10 DNA methylation during the implantation window in mice. GnRH analogue mouse models were used and were treated with either human menopausal gonadotropin (HMG) and a GnRH agonist or HMG and a GnRH antagonist. Uterus samples were collected 48 h after GnRH analogue treatment or ovulation. Bisulfite sequencing polymerase chain reaction (PCR), quantitative-PCR and western blot analysis were performed to assess Hoxa10 and integrin β3 expression. Scanning electron microscope analyses were conducted to analyze pinopode development. Compared with the natural cycle control mice, mice in the GnRH analogue groups were found to exhibit increased levels of methylation at the Hoxa10 promoter, decreased Hoxa10 mRNA and protein expression and disrupted pinopode development. These findings suggest that GnRH-as may be associated with altered Hoxa10 DNA methylation, thus GnRH-as may affect uterine Hoxa10 expression and endometrial receptivity.

The many faces of estrogen signaling

Estrogens have long been known as important regulators of the female reproductive functions; however, our understanding of the role estrogens play in the human body has changed significantly over the past years. It is now commonly accepted that estrogens and androgens have important functions in both female and male physiology and pathology. This is in part due to the local synthesis and action of estrogens that broadens the role of estrogen signaling beyond that of the endocrine system. Furthermore, there are several different mechanisms through which the three estrogen receptors (ERs), ERα, ERβ and G protein-coupled estrogen receptor 1 (GPER1) are able to regulate target gene transcription. ERα and ERβ are mostly associated with the direct and indirect genomic signaling pathways that result in target gene expression. Membrane-bound GPER1 is on the other hand responsible for the rapid non-genomic actions of estrogens that activate various protein-kinase cascades. Estrogen signaling is also tightly connected with another important regulatory entity, i.e. epigenetic mechanisms. Posttranslational histone modifications, microRNAs (miRNAs) and DNA methylation have been shown to influence gene expression of ERs as well as being regulated by estrogen signaling. Moreover, several coregulators of estrogen signaling also exhibit chromatin-modifying activities further underlining the importance of epigenetic mechanisms in estrogen signaling. This review wishes to highlight the newer aspects of estrogen signaling that exceed its classical endocrine regulatory role, especially emphasizing its tight intertwinement with epigenetic mechanisms.

Effects of atrazine and chlorpyrifos on DNA methylation in the liver, kidney and gill of the common carp (Cyprinus carpio L.)

Pesticide exposure has repeatedly been associated with cancers, although the molecular mechanisms behind this association are largely undetermined. Abnormal DNA methylation plays a key role in the process of some disease. However, little was known about the effect of pesticides on DNA methylation in the common carp. In this study, we investigated the mRNA levels of DNA methyltransferases (DNMTs) and methyl-CpG-binding protein DNA-binding domain protein 2 (MBD2) as well as the DNA methylation levels in the liver, kidney and gill of the common carp (Cyprinus carpio L.) after 40-d exposure to atrazine (ATR) and chlorpyrifos (CPF) alone or in combination, and a 40-d recovery period. Juvenile common carp were exposed to various concentrations of ATR (at concentrations of 4.28, 42.8 and 428μg/L), CPF (1.16, 11.6 and 116μg/L), and an ATR/CPF mixture (at concentrations of 1.13, 11.3 and 113μg/L). The results revealed that the levels of genomic DNA methylation decreased in all tissues after 40d of exposure to ATR and CPF either individually or in combination. Moreover, the mRNA expression of DNMTs was down-regulated in all treatment groups. In contrast, the mRNA expression of MBD2 was up-regulated. These results demonstrated that long-term exposure to ATR, CPF and ATR/CPF mixtures could disrupt genomic DNA. It might imply that DNA methylation is involved in the toxicity caused by ATR and CPF in the common carp.

Epigenetic heredity of human height

Genome‐wide SNP analyses have identified genomic variants associated with adult human height. However, these only explain a fraction of human height variation, suggesting that significant information might have been systematically missed by SNP sequencing analysis. A candidate for such non‐SNP‐linked information is DNA methylation. Regulation by DNA methylation requires the presence of CpG islands in the promoter region of candidate genes. Seventy two of 87 (82.8%), height‐associated genes were indeed found to contain CpG islands upstream of the transcription start site (USC CpG island searcher; validation: UCSC Genome Browser), which were shown to correlate with gene regulation. Consistent with this, DNA hypermethylation modules were detected in 42 height‐associated genes, versus 1.5% of control genes (P = 8.0199e⁻¹⁷), as were dynamic methylation changes and gene imprinting. Epigenetic heredity thus appears to be a determinant of adult human height. Major findings in mouse models and in human genetic diseases support this model. Modulation of DNA methylation are candidate to mediate environmental influence on epigenetic traits. This may help to explain progressive height changes over multiple generations, through trans‐generational heredity of progressive DNA methylation patterns.

Epigenetic heredity appears to be a determinant of adult human height. Major findings in mouse models and in human genetic diseases support this model. Modulation of DNA methylation is candidate to mediate environmental influence on epigenetic traits.

Molecular mechanisms of luteinization

Dynamic changes in steroidogenesis occur in ovarian granulosa cells during ovulation after the LH surge. The ovulatory LH surge induces rapid up-regulation of steroidogenic acute regulatory (StAR) protein and rapid down-regulation of aromatase (Cyp19a1) in granulosa cells undergoing luteinization during ovulation. These rapid changes in StAR and Cyp19a1 gene expression after the LH surge efficiently facilitate progesterone production, which plays a crucial role in ovulation and the following luteinization. Recently, it has become clear that epigenetic regulation such as histone modifications and DNA methylation play a key role in gene expression through the chromatin remodeling of the promoter region. This study reports the in vivo evidence that epigenetic mechanisms including histone modifications, DNA methylation and chromatin remodeling are involved in the rapid changes of StAR and Cyp19a1 gene expression in granulosa cells undergoing luteinization during ovulation.

Genome-wide DNA methylation analysis predicts an epigenetic switch for GATA factor expression in endometriosis

Endometriosis is a gynecological disease defined by the extrauterine growth of endometrial-like cells that cause chronic pain and infertility. The disease is limited to primates that exhibit spontaneous decidualization, and diseased cells are characterized by significant defects in the steroid-dependent genetic pathways that typify this process. Altered DNA methylation may underlie these defects, but few regions with differential methylation have been implicated in the disease. We mapped genome-wide differences in DNA methylation between healthy human endometrial and endometriotic stromal cells and correlated this with gene expression using an interaction analysis strategy. We identified 42,248 differentially methylated CpGs in endometriosis compared to healthy cells. These extensive differences were not unidirectional, but were focused intragenically and at sites distal to classic CpG islands where methylation status was typically negatively correlated with gene expression. Significant differences in methylation were mapped to 403 genes, which included a disproportionally large number of transcription factors. Furthermore, many of these genes are implicated in the pathology of endometriosis and decidualization. Our results tremendously improve the scope and resolution of differential methylation affecting the HOX gene clusters, nuclear receptor genes, and intriguingly the GATA family of transcription factors. Functional analysis of the GATA family revealed that GATA2 regulates key genes necessary for the hormone-driven differentiation of healthy stromal cells, but is hypermethylated and repressed in endometriotic cells. GATA6, which is hypomethylated and abundant in endometriotic cells, potently blocked hormone sensitivity, repressed GATA2, and induced markers of endometriosis when expressed in healthy endometrial cells. The unique epigenetic fingerprint in endometriosis suggests DNA methylation is an integral component of the disease, and identifies a novel role for the GATA family as key regulators of uterine physiology-aberrant DNA methylation in endometriotic cells correlates with a shift in GATA isoform expression that facilitates progesterone resistance and disease progression.

Genome-wide DNA methylation profiling in cultured eutopic and ectopic endometrial stromal cells

The objective of this study was to characterize the genome-wide DNA methylation profiles of isolated endometrial stromal cells obtained from eutopic endometria with (euESCa) and without endometriosis (euESCb) and ovarian endometrial cysts (choESC). Three samples were analyzed in each group. The infinium methylation array identified more hypermethylated and hypomethylated CpGs in choESC than in euESCa, and only a few genes were methylated differently in euESCa and euESCb. A functional analysis revealed that signal transduction, developmental processes, immunity, etc. were different in choESC and euESCa. A clustering analysis and a principal component analysis performed based on the methylation levels segregated choESC from euESC, while euESCa and euESCb were identical. A transcriptome analysis was then conducted and the results were compared with those of the DNA methylation analysis. Interestingly, the hierarchical clustering and principal component analyses showed that choESC were segregated from euESCa and euESCb in the DNA methylation analysis, while no segregation was recognized in the transcriptome analysis. The mRNA expression levels of the epigenetic modification enzymes, including DNA methyltransferases, obtained from the specimens were not significantly different between the groups. Some of the differentially methylated and/or expressed genes (NR5A1, STAR, STRA6 and HSD17B2), which are related with steroidogenesis, were validated by independent methods in a larger number of samples. Our findings indicate that different DNA methylation profiles exist in ectopic ESC, highlighting the benefits of genome wide DNA methylation analyses over transcriptome analyses in clarifying the development and characterization of endometriosis.

DNA methyltransferases and TETs in the regulation of differentiation and invasiveness of extra-villous trophoblasts

Specialized cell types of trophoblast cells form the placenta in which each cell type has particular properties of proliferation and invasion. The placenta sustains the growth of the fetus throughout pregnancy and any aberrant trophoblast differentiation or invasion potentially affects the future health of the child and adult. Recently, the field of epigenetics has been applied to understand differentiation of trophoblast lineages and embryonic stem cells (ESC), from fertilization of the oocyte onward. Each trophoblast cell-type has a distinctive epigenetic profile and we will concentrate on the epigenetic mechanism of DNA methyltransferases and TETs that regulate DNA methylation. Environmental factors affecting the mother potentially regulate the DNA methyltransferases in trophoblasts, and so do steroid hormones, cell cycle regulators, such as p53, and cytokines, especially interlukin-1β. There are interesting questions of why trophoblast genomes are globally hypomethylated yet specific genes can be suppressed by hypermethylation (in general, tumor suppressor genes, such as E-cadherin) and how invasive cell-types are liable to have condensed chromatin, as in metastatic cancer cells. Future work will attempt to understand the interactive nature of all epigenetic mechanisms together and their effect on the complex biological system of trophoblast differentiation and invasion in normal as well as pathological conditions.

Epigenetic regulation of hepatocellular carcinoma in non-alcoholic fatty liver disease

Emerging evidence that epigenetics converts alterations in nutrient and metabolism into heritable pattern of gene expression has profound implications in understanding human physiology and diseases. Non-alcoholic fatty liver disease (NAFLD) is the hepatic manifestation of metabolic syndrome including obesity and diabetes which elevate the risk of hepatocellular carcinoma (HCC) especially in male. This review focuses on the molecular connections between metabolic dysfunction and aberrant epigenetic alterations in the development of HCC in NAFLD. The metabolites derived from excessive insulin, glucose and lipid may perturb epigenetic gene regulation through DNA methylation, histone modifications, and RNA interference, leading to activation of pro-inflammatory signaling and deregulation of metabolic pathways. The interplay and crosstalk of chromatin-modifying enzymes, microRNAs, signaling pathways and the downstream transcription factors result in epigenomic reprogramming that drives hepatocellular transformation. The interactions between sex hormone pathways and the epigenetic machineries that influence chromatin states in NAFLD provide potential molecular mechanisms of gender disparity in HCC. A deeper understanding of these connections and comprehensive molecular catalog of hepatocarcinogenesis may shed light in the identification of druggable epigenetic targets for the prevention and treatment of HCC in obese or diabetic patients.

Intracrine oestrogen production and action in breast cancer: an epigenetic focus

Epigenome changes have been widely demonstrated to contribute to the initiation and progression of a vast array of cancers including breast cancer. The reversible process of many epigenetic modifications is thus an attractive feature for the development of novel therapeutic measures. In oestrogen receptor α (hereinafter referred to as ER) positive tumours, endocrine therapies have proven beneficial in patient care, particularly in postmenopausal women where two-thirds of tumours are oestrogen dependent. However, resistance to such therapies is a common feature amongst individuals. In the current review, we discuss the influence that epigenetics has on oestrogen dependent breast cancers, in particular (i) the production of intracrine oestrogen in postmenopausal women, (ii) the action of oestrogen on epigenetic processes, and (iii) the links between epigenetics and endocrine resistance and the current advancements in epigenetic therapy that target this process. This article is part of a Special Issue entitled 'CSR 2013'.

Catalog of mRNA expression patterns for DNA methylating and demethylating genes in developing mouse lower urinary tract

The mouse prostate develops from a component of the lower urinary tract (LUT) known as the urogenital sinus (UGS). This process requires androgens and signaling between mesenchyme and epithelium. Little is known about DNA methylation during prostate development, including which factors are expressed, whether their expression changes over time, and if DNA methylation contributes to androgen signaling or influences signaling between mesenchyme and epithelium. We used in situ hybridization to evaluate the spatial and temporal expression pattern of mRNAs which encode proteins responsible for establishing, maintaining or remodeling DNA methylation. These include DNA methyltransferases, DNA deaminases, DNA glycosylases, base excision repair and mismatch repair pathway members. The mRNA expression patterns were compared between male and female LUT prior to prostatic bud formation (14.5 days post coitus (dpc)), during prostatic bud formation (17.5 dpc) and during prostatic branching morphogenesis (postnatal day (P) 5). We found dramatic changes in the patterns of these mRNAs over the course of prostate development and identified examples of sexually dimorphic mRNA expression. Future investigation into how DNA methylation patterns are established, maintained and remodeled during the course of embryonic prostatic bud formation may provide insight into prostate morphogenesis and disease.

Maternal low-protein diet affects epigenetic regulation of hepatic mitochondrial DNA transcription in a sex-specific manner in newborn piglets associated with GR binding to its promoter

Mitochondrial oxidative phosphorylation (OXPHOS) plays an important role in energy homeostasis by controlling electron transfer and ATP generation. Maternal malnutrition during pregnancy affects mitochondrial (mt) DNA-encoded OXPHOS activity in offspring, yet it is unknown whether epigenetic mechanism is involved in the transcriptional regulation of mtDNA-encoded OXPHOS genes. In this study, 14 primiparous purebred Meishan sows were fed either standard- (SP, 12% crude protein) or low-protein (LP; 6% crude protein) diets throughout gestation, and the hepatic expression and transcriptional regulation of mtDNA-encoded OXPHOS genes were analyzed in newborn piglets. Maternal low protein diet decreased hepatic mtDNA copy number in males, but not in females. LP male piglets had significantly higher hepatic AMP concentration and low energy charge, which was accompanied by enhanced mRNA expression of NADH dehydrogenase subunits 6, cytochrome c oxidase subunit 1, 2, 3 and cytochrome b, as well as increased cytochrome c oxidase enzyme activity. In contrast, LP female piglets showed significantly lower hepatic AMP concentrations and higher energy charge with no alterations in OXPHOS gene expression. Moreover, LP males demonstrated higher glucocorticoid receptor (GR) binding to the mtDNA promoter compared with SP males, which was accompanied by lower cytosine methylation and hydroxymethylation on mtDNA promoter. Interestingly, opposite changes were seen in females, which showed diminished GR binding and enriched cytosine methylation and hydroxymethylation on mtDNA promoter. These results suggest that maternal low protein diet during pregnancy causes sex-dependent epigenetic alterations in mtDNA-encoded OXPHOS gene expression, possibly GR is involved in mtDNA transcription regulation.

Effect of cyclic AMP and estrogen/progesterone on the transcription of DNA methyltransferases during the decidualization of human endometrial stromal cells

Progesterone, estrogen and cyclic adenosine monophosphate (cAMP) together regulate the decidualization of human endometrial stromal cells in a time-dependent manner. The role of DNA methylation and the three active DNA methyltransferases (DNMTs) in the regulation of decidualization is gaining interest but the exact role of this epigenetic mechanism during decidualization is largely unknown. We aimed to understand the effect of the main regulators of decidualization on the expression of the DNMTs and in turn on the expression of steroid hormone receptors during the decidualization. We conducted a time-course analysis from 6 h to 10 days to examine the change in gene expression of the DNMTs and the steroid hormone receptors over time in response to estradiol, medroxy-progesterone acetate (MPA) and dibutyryl-cAMP (db-cAMP) in a human endometrial stromal cells (HESC) cell line. Only the combination treatment with MPA-mix (estradiol + MPA + db-cAMP) up-regulated ERα, PGR, progesterone receptor B (PRB) and androgen receptor at 24 h. Both decidualization pathways of db-cAMP and estradiol/MPA, independently and combined, consistently down-regulated DNMT3B mRNA expression from 6 h till 10 days, whereas DNMT1 and DNMT3A mRNA expression were down-regulated transiently. Forced expression of DNMT3B in HESC for 10 days attenuated IGFBP1 mRNA and protein expression; and forced expression of DNMT3B combined with MPA-mix treatment synergistically increased the expression of PRB at 24 h. The HESC morphology and proliferation remained unchanged in response to forced expression of DNMT3B. In conclusion, mRNA expression of the DNMTs during decidualization is dynamic, so that expression varies according to the cAMP or estradiol/MPA pathway treatments that regulate them in a time-dependent manner. Although forced expression of DNMT3B by itself is insufficient to inhibit decidualization, forced expression of DNMT3B in combination with MPA-mix synergistically up-regulated PRB, as well as attenuated the expression of IGFBP1, the decidualization marker.

Epigenetic regulation of estrogen signaling in breast cancer

Estrogen signaling is mediated by ERα and ERβ in hormone dependent, breast cancer (BC). Over the last decade the implication of epigenetic pathways in BC tumorigenesis has emerged: cancer-related epigenetic modifications are implicated in both gene expression regulation, and chromosomal instability. In this review, the epigenetic-mediated estrogen signaling, controlling both ER level and ER-targeted gene expression in BC, are discussed: (1) ER silencing is frequently observed in BC and is often associated with epigenetic regulations while chemical epigenetic modulators restore ER expression and increase response to treatment;(2) ER-targeted gene expression is tightly regulated by co-recruitment of ER and both coactivators/corepressors including HATs, HDACs, HMTs, Dnmts and Polycomb proteins.

Life-course origins of the ages at menarche and menopause

A woman's age at menarche (first menstrual period) and her age at menopause are the alpha and omega of her reproductive years. The timing of these milestones is critical for a woman's health trajectory over her lifespan, as they are indicators of ovarian function and aging. Both early and late timing of either event are associated with risk for adverse health and psychosocial outcomes. Thus, the search for a relationship between age at menarche and menopause has consequences for chronic disease prevention and implications for public health. This article is a review of evidence from the fields of developmental biology, epidemiology, nutrition, demography, sociology, and psychology that examine the menarche-menopause connection. Trends in ages at menarche and menopause worldwide and in subpopulations are presented; however, challenges exist in constructing trends. Among 36 studies that examine the association between the two sentinel events, ten reported a significant direct association, two an inverse association, and the remainder had null findings. Multiple factors, including hormonal and environmental exposures, socioeconomic status, and stress throughout the life course are hypothesized to influence the tempo of growth, including body size and height, development, menarche, menopause, and the aging process in women. The complexity of these factors and the pathways related to their effects on each sentinel event complicate evaluation of the relationship between menarche and menopause. Limitations of past investigations are discussed, including lack of comparability of socioeconomic status indicators and biomarker use across studies, while minority group differences have received scant attention. Suggestions for future directions are proposed. As research across endocrinology, epidemiology, and the social sciences becomes more integrated, the confluence of perspectives will yield a richer understanding of the influences on the tempo of a woman's reproductive life cycle as well as accelerate progress toward more sophisticated preventive strategies for chronic disease.

Epigenetic changes through DNA methylation contribute to uterine stromal cell decidualization

Embryo-uterine interaction during early pregnancy critically depends on the coordinated expression of numerous genes at the site of implantation. The epigenetic mechanism through DNA methylation (DNM) plays a major role in the control of gene expression, although this regulatory event remains unknown in uterine implantation sites. Our analysis revealed the presence of DNA methyltransferase 1 (Dnmt1) in mouse endometrial cells on the receptive d 4 of pregnancy and early postattachment (d 5) phase, whereas Dnmt3a had lower abundant expression. Both Dnmt1 and Dnmt3a were coordinately expressed in decidual cells on d 6-8. 5-Methycytosine showed a similar expression pattern to that of Dnmt1. The preimplantation inhibition of DNM by 5-aza-2'-deoxycytodine was not antagonistic for embryonic attachment, although endometrial stromal cell proliferation at the site of implantation was down-regulated, indicating a disturbance with the postattachment decidualization event. Indeed, the peri- or postimplantation inhibition of DNM caused significant abrogation of decidualization, with concomitant loss of embryos. We next identified decidual genes undergoing alteration of DNM using methylation-sensitive restriction fingerprinting. One such gene, Chromobox homolog 4, an epigenetic regulator in the polycomb group protein family, exhibited hypomethylation in promoter DNA and increased expression with the onset of decidualization. Furthermore, inhibition of DNM resulted in enhanced expression of hypermethylated genes (Bcl3 and Slc16a3) in the decidual bed as compared with control, indicating aberration of gene expression may be associated with DNM-inhibition-induced decidual perturbation. Overall, these results suggest that uterine DNM plays a major role for successful decidualization and embryo development during early pregnancy.

Effects of Chinese medicines for tonifying the kidney on DNMT1 protein expression in endometrium of infertile women during implantation period

OBJECTIVES

The purpose of this study was to explore the effects of Erzhi Tiangui Granule (ETG) on DNA methyltransferases (DNMT) 1 protein expression in endometrium of infertile women with Kidney-yin Deficiency syndrome.

METHODS

A randomized, double-blinded, placebo-controlled clinical trial was conducted. Sixty-six (66) infertile patients who had Kidney-yin Deficiency syndrome and who were to undergo in vitro fertilization-embryo transfer (IVF-ET) were randomly assigned to either a treatment group or a control group according to a random table. Besides gonadotropin (Gn) therapy in both groups, the treatment group received ETG for 3 menstrual cycles before IVF, and the control group received placebo granules. The ETG and the placebo granules were made with similar color and shape, as well as in the same packaging. The scores of the Kidney-yin Deficiency syndrome were assessed. Other outcome measures included the dosage and duration of Gn, the number of retrieved oocytes, the rate of high-quality oocytes, the rate of high-quality embryos, the fertilization rate, and the clinical pregnancy rate. DNMT1 protein expression in the endometrium was measured in the midluteal phase.

RESULTS

The difference in the syndrome score change before and after treatment between the two groups was statistically significant (p<0.05). The dosage and duration of Gn were significantly lower in the treatment group than those in the control group (p<0.05). The high-quality oocyte and embryo rates, and clinical pregnancy rate were all higher in the treatment group than those in the control group (p<0.05). The fertilization rate was not significant when compared to the placebo group. No difference was found in the number of retrieved oocytes between the two groups. The DNMT1 protein expression in the endometrium was much more abundant in the treatment group than that in the control group (p<0.05).

CONCLUSIONS

For the infertile patients undergoing IVF, the Chinese recipe for tonifying the Kidney as an adjunct treatment could reduce Gn dosage and treatment duration, alleviate clinical symptoms, and improve the clinical pregnancy rate. The increased level of DNMT1 protein expression after treatment may lead to enhanced endometrial receptivity. This finding may explain the improvement in clinical pregnancy rate.

5-aza-2'-deoxycytidine leads to reduced embryo implantation and reduced expression of DNA methyltransferases and essential endometrial genes

BACKGROUND

The DNA demethylating agent 5-aza-2'-deoxycytidine (5-aza-CdR) incorporates into DNA and decreases DNA methylation, sparking interest in its use as a potential therapeutic agent. We aimed to determine the effects of maternal 5-aza-CdR treatment on embryo implantation in the mouse and to evaluate whether these effects are associated with decreased levels of DNA methyltransferases (Dnmts) and three genes (estrogen receptor α [Esr1], progesterone receptor [Pgr], and homeobox A10 [Hoxa10]) that are vital for control of endometrial changes during implantation.

METHODS AND PRINCIPAL FINDINGS

Mice treated with 5-aza-CdR had a dose-dependent decrease in number of implantation sites, with defected endometrial decidualization and stromal cell proliferation. Western blot analysis on pseudo-pregnant day 3 (PD3) showed that 0.1 mg/kg 5-aza-CdR significantly repressed Dnmt3a protein level, and 0.5 mg/kg 5-aza-CdR significantly repressed Dnmt1, Dnmt3a, and Dnmt3b protein levels in the endometrium. On PD5, mice showed significantly decreased Dnmt3a protein level with 0.1 mg/kg 5-aza-CdR, and significantly decreased Dnmt1 and Dnmt3a with 0.5 mg/kg 5-aza-CdR. Immunohistochemical staining showed that 5-aza-CdR repressed DNMT expression in a cell type-specific fashion within the uterus, including decreased expression of Dnmt1 in luminal and/or glandular epithelium and of Dnmt3a and Dnmt3b in stroma. Furthermore, the 5' flanking regions of the Esr1, Pgr, and Hoxa10 were hypomethylated on PD5. Interestingly, the higher (0.5 mg/kg) dose of 5-aza-CdR decreased protein expression of Esr1, Pgr, and Hoxa10 in the endometrium on PD5 in both methylation-dependent and methylation-independent manners.

CONCLUSIONS

The effects of 5-aza-CdR on embryo implantation in mice were associated with altered expression of endometrial Dnmts and genes controlling endometrial changes, suggesting that altered gene methylation, and not cytotoxicity alone, contributes to implantation defects induced by 5-aza-CdR.

Polymorphic variants of DNMT3A and the risk of endometriosis

OBJECTIVE

Overexpression of DNA methyltransferase 3A (DNMT3A) and aberrant methylation of various genes in eutopic endometrium have been demonstrated in women with endometriosis. We aimed to study whether DNMT3A polymorphisms could be a genetic risk factor for endometriosis and endometriosis-related infertility.

STUDY DESIGN

We studied 5 SNPs (rs2289195, rs7590760, rs13401241, rs749131 and rs1550117) located in the DNMT3A gene in 357 women with endometriosis and 640 controls.

RESULTS

We did not observe significant differences between genotype and allele frequencies of rs2289195, rs7590760, rs13401241, rs749131 and rs1550117 SNPs in women with endometriosis, endometriosis-related infertility, and controls. The lowest p values of the trend test were observed for DNMT3A rs1550117 in endometriosis and endometriosis-related infertility (p(trend)=0.049 and p(trend)=0.055, respectively).

CONCLUSIONS

Our results did not supply evidence for the contribution of SNPs located in DNMT3A to either endometriosis or endometriosis-related infertility.

Effects of chronic exposure to arsenic and estrogen on epigenetic regulatory genes expression and epigenetic code in human prostate epithelial cells

Chronic exposures to arsenic and estrogen are known risk factors for prostate cancer. Though the evidence suggests that exposure to arsenic or estrogens can disrupt normal DNA methylation patterns and histone modifications, the mechanisms by which these chemicals induce epigenetic changes are not fully understood. Moreover, the epigenetic effects of co-exposure to these two chemicals are not known. Therefore, the objective of this study was to evaluate the effects of chronic exposure to arsenic and estrogen, both alone and in combination, on the expression of epigenetic regulatory genes, their consequences on DNA methylation, and histone modifications. Human prostate epithelial cells, RWPE-1, chronically exposed to arsenic and estrogen alone and in combination were used for analysis of epigenetic regulatory genes expression, global DNA methylation changes, and histone modifications at protein level. The result of this study revealed that exposure to arsenic, estrogen, and their combination alters the expression of epigenetic regulatory genes and changes global DNA methylation and histone modification patterns in RWPE-1 cells. These changes were significantly greater in arsenic and estrogen combination treated group than individually treated group. The findings of this study will help explain the epigenetic mechanism of arsenic- and/or estrogen-induced prostate carcinogenesis.

Gene expression and DNA-methylation of bovine pretransfer endometrium depending on its receptivity after in vitro-produced embryo transfer

Embryonic implantation to establish a pregnancy is a complex process that requires appropriate communication between the embryo and the maternal endometrium. Inadequate uterine receptivity may contribute to the majority of implantation failures. To provide a comprehensive inventory of genes and functional networks that represent the maternal input of the embryo-maternal cross-talk, a longitudinal, holistic study of the endometrial transcriptome in relation to the days of estrous and to the receptivity of the endometrium was performed in bovine. At day 3 of estrous, genes related to cell communication and mitochondrial energy metabolism were differentially expressed among high- and low-receptive endometria (HR, LR); at day 7, transcripts functioning in immune and inflammatory pathways, oxidative stress, and angiogenesis had different abundances. Additionally, temporal transcriptional changes between days 3 and 7 differed considerably among HR and LR. Further, several transcription factors were predicted as relevant for receptivity because they were either differentially expressed among HR and LR animals or are known to be associated with genes we detected to have differential expression. Finally, global DNA methylation varied according to the interaction of receptivity group and day of estrous, and a divergent trend, which correlated with abundance of DNMT1 transcript, was observed in LR and HR along the estrous cycle days. The study revealed that, even in early estrous, transcripts related to cell communication and response to exogenous stimuli, vascularization, and energy supply show divergent expression and longitudinal temporal regulation in HR and LR. Key components of these molecular pathways are known to be dependent on ovarian hormones that promote uterine receptivity.

The endometrial epigenome and its response to steroid hormones

The human endometrium undergoes cyclic morphological and functional changes during the menstrual cycle. These changes are driven mainly by steroid hormones and orchestrated by a myriad of genes - many of which have been identified recently as being epigenetically regulated. Epigenetic modifications, including DNA methylation and histone acetylations, are shown recently to be involved in functional changes in endometrium and endometrial diseases. Since epigenetics itself is a rapidly evolving field, this review starts with an overview of epigenetics and its intrinsic connections with endometrial response to steroid hormones, highlighting its various levels of complexities. This is followed by a review of published and unpublished work on "writers", "erasers", and other players of endometrial epigenome. In the end, areas in need for future research in this area will be exposed.

Dietary folate deficiency in pseudopregnant mice has no effect on homeobox A10 promoter methylation or expression

During the reproductive cycle, a number of genes controlling endometrial changes are regulated by DNA methylation, a common epigenetic modification. Because dietary folate affects DNA methylation, we determined whether a folate-deficient diet (FDD) alters DNA methylation in endometria of pseudopregnant mice, focusing on the homeobox A10 (Hoxa10) promoter. Mice were given an FDD or control diet for 40 to 45 days and examined on day 5 of pseudopregnancy. Compared to control mice, FDD mice had lower folate levels in liver and serum (P = .004). However, the FDD did not significantly affect DNA methylation within the cytosine-guanine dinucleotide (CpG)-rich Hoxa10 promoter, even when specific CpG sites were examined (P > .05). In endometrial tissue sections, the localization of anti-Hoxa10 staining was unchanged in FDD mice. Therefore, folate deficiency did not significantly affect promoter methylation or expression of Hoxa10.

Aging epigenetics: causes and consequences

Growth and development of higher organisms are regulated by the orchestrated change of epigenetic marks over time. In addition, there is also an epigenetic variation without any apparent role in development that is thought to be the result of the stochastic accumulation of epigenetic errors. The process depends on genetic and environmental factors and, when it takes place in adult stem cells, it could play an important role in aging, although the underlying molecular mechanisms are still largely unknown.

Expression of DNA methyltransferases in the mouse uterus during early pregnancy and susceptibility to dietary folate deficiency

We have characterized the uterine expression of DNA methyltransferases (DNMTs) during early pregnancy in mice and determined whether a folate-deficient diet (FDD) can affect DNMTs in this context. Within endometrial cells, expressions of DNMT (cytosine-5) 1 (Dnmt1), Dnmt3a, and Dnmt3b were significantly elevated during the prereceptive phase of pregnancy but generally returned to baseline levels during receptive and postimplantation periods. As such, the transcription of DNMT genes is temporally regulated during early pregnancy. When comparisons were made between implantation sites (IS) and inter-IS on day 5 of pregnancy, lower levels of Dnmt3a were detected at IS. Comparisons between IS and inter-IS did not reveal significant expression differences for other DNMT genes. When tissue sections were examined, DNMT3A was specifically lower in the stroma of IS. Reduced DNMT1 and DNMT3B levels were also observed in the luminal and glandular epithelia of IS, whereas no obvious differences in the stroma were detected. In pseudo-pregnant mice subjected to a FDD, levels of Dnmt1 and Dnmt3a (but not Dnmt3b) were significantly upregulated in endometrial tissues, as compared with controls. When tissues from these folate-deficient mice were examined, DNMT1 levels were elevated in both the luminal and glandular epithelia, whereas DNMT3A was upregulated in the luminal epithelium and the stroma. A slight increase in DNMT3B levels was detected in the glandular epithelium. These results indicate that DNMTs may regulate the transcription of endometrial genes associated with embryo implantation and that levels of DNMTs are affected by dietary folate in mice.

Influence of prenatal arsenic exposure and newborn sex on global methylation of cord blood DNA

Background

An emerging body of evidence indicates that early-life arsenic (As) exposure may influence the trajectory of health outcomes later in life. However, the mechanisms underlying these observations are unknown.

Objective

The objective of this study was to investigate the influence of prenatal As exposure on global methylation of cord blood DNA in a study of mother/newborn pairs in Matlab, Bangladesh.

Design

Maternal and cord blood DNA were available from a convenience sample of 101 mother/newborn pairs. Measures of As exposure included maternal urinary As (uAs), maternal blood As (mbAs) and cord blood As (cbAs). Several measures of global DNA methylation were assessed, including the [3H]-methyl-incorporation assay and three Pyrosequencing assays: Alu, LINE-1 and LUMA.

Results

In the total sample, increasing quartiles of maternal uAs were associated with an increase in covariate-adjusted means of newborn global DNA methylation as measured by the [3H]-methyl-incorporation assay (quartile 1 (Q1) and Q2 vs. Q4; p = 0.06 and 0.04, respectively). Sex-specific linear regression analyses, while not reaching significance level of 0.05, indicated that the associations between As exposures and Alu, LINE-1 and LUMA were positive among male newborns (N = 58) but negative among female newborns (N = 43); tests for sex differences were borderline significant for the association of cbAs and mbAs with Alu (p = 0.05 and 0.09, respectively) and for the association between maternal uAs and LINE-1 (p = 0.07). Sex-specific correlations between maternal urinary creatinine and newborn methyl-incorporation, Alu and LINE-1 were also evident (p<0.05).

Conclusions

These results suggest that prenatal As exposure is associated with global DNA methylation in cord blood DNA, possibly in a sex-specific manner. Arsenic-induced epigenetic modifications in utero may potentially influence disease outcomes later in life. Additional studies are needed to confirm these findings and to examine the persistence of DNA methylation marks over time.