Widespread enhancer activation via ERα mediates estrogen response in vivo during uterine development

Unexpected nuclear hormone receptor and chromatin dynamics regulate estrous cycle dependent gene expression

Chromatin changes in response to estrogen and progesterone are well established in cultured cells, but how they control gene expression under physiological conditions is largely unknown. To address this question, we examined in vivo estrous cycle dynamics of mouse uterus hormone receptor occupancy, chromatin accessibility and chromatin structure by combining RNA-seq, ATAC-seq, HiC-seq and ChIP-seq. Two estrous cycle stages were chosen for these analyses, diestrus (highest estrogen) and estrus (highest progesterone). Unexpectedly, rather than alternating with each other, estrogen receptor alpha (ERα) and progesterone receptor (PGR) were co-bound during diestrus and lost during estrus. Motif analysis of open chromatin followed by hypoxia inducible factor 2A (HIF2A) ChIP-seq and conditional uterine deletion of this transcription factor revealed a novel role for HIF2A in regulating diestrus gene expression patterns that were independent of either ERα or PGR binding. Proteins in complex with ERα included PGR and cohesin, only during diestrus. Combined with HiC-seq analyses, we demonstrate that complex chromatin architecture changes including enhancer switching are coordinated with ERα and PGR co-binding during diestrus and non-hormone receptor transcription factors such as HIF2A during estrus to regulate most differential gene expression across the estrous cycle.

The influence of estrogen on myocardial post-translational modifications and cardiac function in women

The lifetime risk of heart failure (HF) is comparable in men and women; nevertheless, disparities exist in our understanding of how HF differs between sexes. Several differences in cardiac physiology exist between men and women including the propensity to develop specific HF phenotypes. Men are more likely to be diagnosed with HF failure with reduced ejection fraction, while women have a greater propensity to develop HF with preserved ejection fraction. The mechanisms responsible for these differences remain unclear. Post-translational modifications (PTMs) of myofilament proteins likely contribute to these sex-specific propensities. The role of PTMs in heart disease is an expanding field with immense potential therapeutic targets. However, numerous PTMs remain underexplored, particularly in the context of the female heart. Estrogen, a key gonadal hormone, cardioprotective in pre-menopausal women and its loss with menopause likely contributes to disease in aging women. However, how estrogen regulates PTMs to contribute to HF development is not fully clear. This review outlines key sex differences in HF along with characterizing the contributions of novel myocardial PTMs in cardiac physiology and their regulation by estrogen. Collectively, we highlight the necessity for further investigation into women's heart health and the distinctive mechanisms distinguishing women from men.

Multiple tissue-specific epigenetic alterations regulate persistent gene expression changes following developmental DES exposure in mouse reproductive tissues

Clinically, developmental exposure to the endocrine disrupting chemical, diethylstilboestrol (DES), results in long-term male and female infertility. Experimentally, developmental exposure to DES results in abnormal reproductive tract phenotypes in male and female mice. Previously, we reported that neonatal DES exposure causes ERα-mediated aberrations in the transcriptome and in DNA methylation in seminal vesicles (SVs) of adult mice. However, only a subset of DES-altered genes could be explained by changes in DNA methylation. We hypothesized that alterations in histone modification may also contribute to the altered transcriptome during SV development. To test this idea, we performed a series of genome-wide analyses of mouse SVs at pubertal and adult developmental stages in control and DES-exposed wild-type and ERα knockout mice. Neonatal DES exposure altered ERα-mediated mRNA and lncRNA expression in adult SV, including genes encoding chromatin-modifying proteins that can impact histone H3K27ac modification. H3K27ac patterns, particularly at enhancers, and DNA methylation were reprogrammed over time during normal SV development and after DES exposure. Some of these reprogramming changes were ERα-dependent, but others were ERα-independent. A substantial number of DES-altered genes had differential H3K27ac peaks at nearby enhancers. Comparison of gene expression changes, H3K27ac marks and DNA methylation marks between adult SV and adult uterine tissue from ovariectomized mice neonatally exposed to DES revealed that most of the epigenetic changes and altered genes were distinct in the two tissues. These findings indicate that the effects of developmental DES exposure cause reprogramming of reproductive tract tissue differentiation through multiple epigenetic mechanisms.

Super-enhancer-driven lncRNA LIMD1-AS1 activated by CDK7 promotes glioma progression

Long non-coding RNAs (lncRNAs) are tissue-specific expression patterns and dysregulated in cancer. How they are regulated still needs to be determined. We aimed to investigate the functions of glioma-specific lncRNA LIMD1-AS1 activated by super-enhancer (SE) and identify the potential mechanisms. In this paper, we identified a SE-driven lncRNA, LIMD1-AS1, which is expressed at significantly higher levels in glioma than in normal brain tissue. High LIMD1-AS1 levels were significantly associated with a shorter survival time of glioma patients. LIMD1-AS1 overexpression significantly enhanced glioma cells proliferation, colony formation, migration, and invasion, whereas LIMD1-AS1 knockdown inhibited their proliferation, colony formation, migration, and invasion, and the xenograft tumor growth of glioma cells in vivo. Mechanically, inhibition of CDK7 significantly attenuates MED1 recruitment to the super-enhancer of LIMD1-AS1 and then decreases the expression of LIMD1-AS1. Most importantly, LIMD1-AS1 could directly bind to HSPA5, leading to the activation of interferon signaling. Our findings support the idea that CDK7 mediated-epigenetically activation of LIMD1-AS1 plays a crucial role in glioma progression and provides a promising therapeutic approach for patients with glioma.

Upregulation of FOXA2 in uterine luminal epithelium and vaginal basal epithelium of epiERα-/- (Esr1fl/flWnt7aCre/+) mice†

Forkhead box protein A2 (FOXA2) is a pioneer transcription factor important for epithelial budding and morphogenesis in different organs. It has been used as a specific marker for uterine glandular epithelial cells (GE). FOXA2 has close interactions with estrogen receptor α (ERα). ERα binding to Foxa2 gene in the uterus indicates its regulation of Foxa2. The intimate interactions between ERα and FOXA2 and their essential roles in early pregnancy led us to investigate the expression of FOXA2 in the female reproductive tract of pre-implantation epiERα-/- (Esr1fl/flWnt7aCre/+) mice, in which ERα is conditionally deleted in the epithelium of reproductive tract. In the oviduct, FOXA2 is detected in the ciliated epithelial cells of ampulla but absent in the isthmus of day 3.5 post-coitum (D3.5) Esr1fl/fl control and epiERα-/- mice. In the uterus, FOXA2 expression in the GE appears to be comparable between Esr1fl/fl and epiERα-/- mice. However, FOXA2 is upregulated in the D0.5 and D3.5 but not PND25-28 epiERα-/- uterine luminal epithelial cells (LE). In the vagina, FOXA2 expression is low in the basal layer and increases toward the superficial layer of the D3.5 Esr1fl/fl vaginal epithelium, but FOXA2 is detected in the basal, intermediate, and superficial layers, with the strongest FOXA2 expression in the intermediate layers of the D3.5 epiERα-/- vaginal epithelium. This study demonstrates that loss of ERα in LE and vaginal basal layer upregulates FOXA2 expression in these epithelial cells during early pregnancy. The mechanisms for epithelial cell-type specific regulation of FOXA2 by ERα remain to be elucidated.

Peptidylarginine deiminase enzymes and citrullinated proteins in female reproductive physiology and associated diseases†

Citrullination, the post-translational modification of arginine residues, is catalyzed by the four catalytically active peptidylarginine deiminase (PAD or PADI) isozymes and alters charge to affect target protein structure and function. PADs were initially characterized in rodent uteri and, since then, have been described in other female tissues including ovaries, breast, and the lactotrope and gonadotrope cells of the anterior pituitary gland. In these tissues and cells, estrogen robustly stimulates PAD expression resulting in changes in levels over the course of the female reproductive cycle. The best-characterized targets for PADs are arginine residues in histone tails, which, when citrullinated, alter chromatin structure and gene expression. Methodological advances have allowed for the identification of tissue-specific citrullinomes, which reveal that PADs citrullinate a wide range of enzymes and structural proteins to alter cell function. In contrast to their important physiological roles, PADs and citrullinated proteins are also involved in several female-specific diseases including autoimmune disorders and reproductive cancers. Herein, we review current knowledge regarding PAD expression and function and highlight the role of protein citrullination in both normal female reproductive tissues and associated diseases.

FOXA2 suppresses endometrial carcinogenesis and epithelial-mesenchymal transition by regulating enhancer activity

FOXA2 encodes a transcription factor mutated in 10% of endometrial cancers (ECs), with a higher mutation rate in aggressive variants. FOXA2 has essential roles in embryonic and uterine development. However, FOXA2’s role in EC is incompletely understood. Functional investigations using human and mouse EC cell lines revealed that FOXA2 controls endometrial epithelial gene expression programs regulating cell proliferation, adhesion, and endometrial-epithelial transition. In live animals, conditional inactivation of Foxa2 or Pten alone in endometrial epithelium did not result in ECs, but simultaneous inactivation of both genes resulted in lethal ECs with complete penetrance, establishing potent synergism between Foxa2 and PI3K signaling. Studies in tumor-derived cell lines and organoids highlighted additional invasion and cell growth phenotypes associated with malignant transformation and identified key mediators, including Myc and Cdh1. Transcriptome and cistrome analyses revealed that FOXA2 broadly controls gene expression programs through modification of enhancer activity in addition to regulating specific target genes, rationalizing its tumor suppressor functions. By integrating results from our cell lines, organoids, animal models, and patient data, our findings demonstrated that FOXA2 is an endometrial tumor suppressor associated with aggressive disease and with shared commonalities among its roles in endometrial function and carcinogenesis.

Elucidating the estrogen-like effects and biocompatibility of the herbal components in the Qing' E formula

ETHNOPHARMACOLOGICAL RELEVANCE

The Qing' E Formula (QEF) is a compound preparation that was originally recorded in the 'Prescriptions of the Bureau of Taiping People's Welfare Pharmacy' during the Song Dynasty (10th century CE). It consists of four Chinese medicinal herbs, Eucommiae Cortex (Eucommia ulmoides), Psoraleae Fructus (Psoralea corylifolium), Juglandis Semen (Juglans regia), and Garlic Rhizoma. According to traditional Chinese medicine (TCM), QEF has the ability to tonify the kidney and strengthen muscle and bone. According to the 'kidney governing bone' theory in TCM, QEF is also used to treat the symptoms of climacteric syndrome, especially osteoporosis caused by reduced production of estrogen during the perimenopausal period; however, the therapeutic roles of the individual components of the QEF and their compatibility within the formula has not been investigated.

AIM OF THE STUDY

In this study, the compatibility mechanism and estrogen-like action properties of the four herbal components in the QEF was elucidated according to the organizing principle of Chinese medicine formulas using both in vitro and in vivo models.

MATERIALS AND METHODS

The estrogen-like effects of QEF and its herbal components were investigated in MCF7 and HEK293 cells as well as ovariectomized (OVX) rats. The estrogen-like effects of the QEF and its components were analyzed in vitro using Cell Counting Kit-8 and Luciferase reporter gene assays. In the in vivo studies, the blood plasma levels of hormones, lipids, neurotransmitters, aromatase, superoxide dismutase (SOD), and malondialdehyde (MDA) were measured through enzyme-linked immunosorbent assays (ELISAs). The histological morphologies of the target organs after exposure to QEF were investigated by HE staining and immunohistochemical methods. The expression levels of estrogen pathway-related proteins and genes in the OVX rats were measured by Western blotting and real time quantitative PCR (RT-qPCR), respectively.

RESULTS

The in vitro results showed that the QEF, Eucommia (EC) and Psoralea (PF) promoted the proliferation of MCF-7 cells and upregulated the expression of ERα, ERβ and pS2 genes in the MCF-7 cells. Notably, the QEF demonstrated the most active estrogen-like effects compared to the individual ingredients. The in vivo results showed that the QEF, EC, and PF increased the uterine coefficient, upregulated the expression of both ERs (ERα and ERβ) in the uterus, and increased blood serum hormone levels. QEF and its individual components ameliorated menopausal-derived lipid metabolism dysfunction, increased neurotransmitter production by stimulating the adrenal glands, enhanced the antioxidant activity in the serum by increasing the concentration of SOD, reversed ovariectomy-derived atrophy in the uterus, and reduced the weight gain associated with estrogen reduction in the OVX rats. The QEF also antagonize the loss of appetite of OVX animals caused by feeding Psoralea alone, which could explain the compatibility mechanism of Qing' E Formula with reducing toxicity and increasing efficiency.

CONCLUSIONS

The estrogen-like effects of Eucommia and Psoralea were mainly mediated through activation of ERα and ERβ. The phytoestrogen components regulated hormone production and the expression of related proteins and genes, which indicated that these components exhibited estrogen-like therapeutic effects. However, the QEF showed the greatest estrogen-like effects compared to the individual components. Overall, this corroborated the therapeutic prowess of the QEF and clarified the pharmacodynamic interactions between the different components extracts in the QEF.

The Potential Relationship Between Environmental Endocrine Disruptor Exposure and the Development of Endometriosis and Adenomyosis

Women with endometriosis, the growth of endometrial glands and stroma outside the uterus, commonly also exhibit adenomyosis, the growth of endometrial tissues within the uterine muscle. Each disease is associated with functional alterations in the eutopic endometrium frequently leading to pain, reduced fertility, and an increased risk of adverse pregnancy outcomes. Although the precise etiology of either disease is poorly understood, evidence suggests that the presence of endometriosis may be a contributing factor to the subsequent development of adenomyosis as a consequence of an altered, systemic inflammatory response. Herein, we will discuss the potential role of exposure to environmental toxicants with endocrine disrupting capabilities in the pathogenesis of both endometriosis and adenomyosis. Numerous epidemiology and experimental studies support a role for environmental endocrine disrupting chemicals (EDCs) in the development of endometriosis; however, only a few studies have examined the potential relationship between toxicant exposures and the risk of adenomyosis. Nevertheless, since women with endometriosis are also frequently found to have adenomyosis, discussion of EDC exposure and development of each of these diseases is relevant. We will discuss the potential mechanisms by which EDCs may act to promote the co-development of endometriosis and adenomyosis. Understanding the disease-promoting mechanisms of environmental toxicants related to endometriosis and adenomyosis is paramount to designing more effective treatment(s) and preventative strategies.

ZNF382 controls mouse neuropathic pain via silencer-based epigenetic inhibition of Cxcl13 in DRG neurons

Nerve injury-induced changes of gene expression in dorsal root ganglion (DRG) are critical for neuropathic pain genesis. However, how these changes occur remains elusive. Here we report the down-regulation of zinc finger protein 382 (ZNF382) in injured DRG neurons after nerve injury. Rescuing this down-regulation attenuates nociceptive hypersensitivity. Conversely, mimicking this down-regulation produces neuropathic pain symptoms, which are alleviated by C-X-C motif chemokine 13 (CXCL13) knockdown or its receptor CXCR5 knockout. Mechanistically, an identified cis-acting silencer at distal upstream of the Cxcl13 promoter suppresses Cxcl13 transcription via binding to ZNF382. Blocking this binding or genetically deleting this silencer abolishes the ZNF382 suppression on Cxcl13 transcription and impairs ZNF382-induced antinociception. Moreover, ZNF382 down-regulation disrupts the repressive epigenetic complex containing histone deacetylase 1 and SET domain bifurcated 1 at the silencer-promoter loop, resulting in Cxcl13 transcriptional activation. Thus, ZNF382 down-regulation is required for neuropathic pain likely through silencer-based epigenetic disinhibition of CXCL13, a key neuropathic pain player, in DRG neurons.

Superenhancer-transcription factor regulatory network in malignant tumors

Objective

This study aims to identify superenhancer (SE)-transcriptional factor (TF) regulatory network related to eight common malignant tumors based on ChIP-seq data modified by histone H3K27ac in the enhancer region of the SRA database.

Methods

H3K27ac ChIP-seq data of eight common malignant tumor samples were downloaded from the SRA database and subjected to comparison with the human reference genome hg19. TFs regulated by SEs were screened with HOMER software. Core regulatory circuitry (CRC) in malignant tumor samples was defined through CRCmapper software and validated by RNA-seq data in TCGA. The findings were substantiated in bladder cancer cell experiments.

Results

Different malignant tumors could be distinguished through the H3K27ac signal. After SE identification in eight common malignant tumor samples, 35 SE-regulated genes were defined as malignant tumor-specific. SE-regulated specific TFs effectively distinguished the types of malignant tumors. Finally, we obtained 60 CRC TFs, and SMAD3 exhibited a strong H3K27ac signal in eight common malignant tumor samples. In vitro experimental data verified the presence of a SE-TF regulatory network in bladder cancer, and SE-TF regulatory network enhanced the malignant phenotype of bladder cancer cells.

Conclusion

The SE-TF regulatory network with SMAD3 as the core TF may participate in the carcinogenesis of malignant tumors.

Sexual fate of murine external genitalia development: Conserved transcriptional competency for male-biased genes in both sexes

Testicular androgen is a master endocrine factor in the establishment of external genital sex differences. The degree of androgenic exposure during development is well known to determine the fate of external genitalia on a spectrum of female- to male-specific phenotypes. However, the mechanisms of androgenic regulation underlying sex differentiation are poorly defined. Here, we show that the genomic environment for the expression of male-biased genes is conserved to acquire androgen responsiveness in both sexes. Histone H3 at lysine 27 acetylation (H3K27ac) and H3K4 monomethylation (H3K4me1) are enriched at the enhancer of male-biased genes in an androgen-independent manner. Specificity protein 1 (Sp1), acting as a collaborative transcription factor of androgen receptor, regulates H3K27ac enrichment to establish conserved transcriptional competency for male-biased genes in both sexes. Genetic manipulation of MafB, a key regulator of male-specific differentiation, and Sp1 regulatory MafB enhancer elements disrupts male-type urethral differentiation. Altogether, these findings demonstrate conservation of androgen responsiveness in both sexes, providing insights into the regulatory mechanisms underlying sexual fate during external genitalia development.

Super-enhancers: a new frontier for epigenetic modifiers in cancer chemoresistance

Although new developments of surgery, chemotherapy, radiotherapy, and immunotherapy treatments for cancer have improved patient survival, the emergence of chemoresistance in cancer has significant impacts on treatment effects. The development of chemoresistance involves several polygenic, progressive mechanisms at the molecular and cellular levels, as well as both genetic and epigenetic heterogeneities. Chemotherapeutics induce epigenetic reprogramming in cancer cells, converting a transient transcriptional state into a stably resistant one. Super-enhancers (SEs) are central to the maintenance of identity of cancer cells and promote SE-driven-oncogenic transcriptions to which cancer cells become highly addicted. This dependence on SE-driven transcription to maintain chemoresistance offers an Achilles' heel for chemoresistance. Indeed, the inhibition of SE components dampens oncogenic transcription and inhibits tumor growth to ultimately achieve combined sensitization and reverse the effects of drug resistance. No reviews have been published on SE-related mechanisms in the cancer chemoresistance. In this review, we investigated the structure, function, and regulation of chemoresistance-related SEs and their contributions to the chemotherapy via regulation of the formation of cancer stem cells, cellular plasticity, the microenvironment, genes associated with chemoresistance, noncoding RNAs, and tumor immunity. The discovery of these mechanisms may aid in the development of new drugs to improve the sensitivity and specificity of cancer cells to chemotherapy drugs.

Endocrine-Disrupting Chemicals' (EDCs) Effects on Tumour Microenvironment and Cancer Progression: Emerging Contribution of RACK1

Endocrine disruptors (EDCs) can display estrogenic and androgenic effects, and their exposure has been linked to increased cancer risk. EDCs have been shown to directly affect cancer cell regulation and progression, but their influence on tumour microenvironment is still not completely elucidated. In this context, the signalling hub protein RACK1 (Receptor for Activated C Kinase 1) could represent a nexus between cancer and the immune system due to its roles in cancer progression and innate immune activation. Since RACK1 is a relevant EDCs target that responds to steroid-active compounds, it could be considered a molecular bridge between the endocrine-regulated tumour microenvironment and the innate immune system. We provide an analysis of immunomodulatory and cancer-promoting effects of different EDCs in shaping tumour microenvironment, with a final focus on the scaffold protein RACK1 as a pivotal molecular player due to its dual role in immune and cancer contexts.

The histone methyltransferase EZH2 is required for normal uterine development and function in mice†

Enhancer of zeste homolog 2 (EZH2) is a rate-limiting catalytic subunit of a histone methyltransferase, polycomb repressive complex, which silences gene activity through the repressive histone mark H3K27me3. EZH2 is critical for epigenetic effects of early estrogen treatment, and may be involved in uterine development and pathologies. We investigated EZH2 expression, regulation, and its role in uterine development/function. Uterine epithelial EZH2 expression was associated with proliferation and was high neonatally then declined by weaning. Pre-weaning uterine EZH2 expression was comparable in wild-type and estrogen receptor 1 knockout mice, showing neonatal EZH2 expression is ESR1 independent. Epithelial EZH2 was upregulated by 17β-estradiol (E2) and inhibited by progesterone in adult uteri from ovariectomized mice. To investigate the uterine role of EZH2, we developed a EZH2 conditional knockout (Ezh2cKO) mouse using a cre recombinase driven by the progesterone receptor (Pgr) promoter that produced Ezh2cKO mice lacking EZH2 in Pgr-expressing tissues (e.g. uterus, mammary glands). In Ezh2cKO uteri, EZH2 was deleted neonatally. These uteri had reduced H3K27me3, were larger than WT, and showed adult cystic endometrial hyperplasia. Ovary-independent uterine epithelial proliferation and increased numbers of highly proliferative uterine glands were seen in adult Ezh2cKO mice. Female Ezh2cKO mice were initially subfertile, and then became infertile by 9 months. Mammary gland development in Ezh2cKO mice was inhibited. In summary, uterine EZH2 expression is developmentally and hormonally regulated, and its loss causes aberrant uterine epithelial proliferation, uterine hypertrophy, and cystic endometrial hyperplasia, indicating a critical role in uterine development and function.

Uterine Patterning, Endometrial Gland Development, and Implantation Failure in Mice Exposed Neonatally to Genistein

BACKGROUND

Embryo implantation relies on precise hormonal regulation, associated gene expression changes, and appropriate female reproductive tract tissue architecture. Female mice exposed neonatally to the phytoestrogen genistein (GEN) at doses similar to those in infants consuming soy-based infant formulas are infertile due in part to uterine implantation defects.

OBJECTIVES

Our goal was to determine the mechanisms by which neonatal GEN exposure causes implantation defects.

METHODS

Female mice were exposed to GEN on postnatal days (PND)1-5 and uterine tissues collected on PND5, PND22-26, and during pregnancy. Analysis of tissue weights, morphology, and gene expression was performed using standard histology, confocal imaging with three-dimensional analysis, real-time reverse transcription polymerase chain reaction (real-time RT-PCR), and microarrays. The response of ovariectomized adults to 17 β -estradiol (E2) and artificial decidualization were measured. Leukemia inhibitory factor (LIF) injections were given intraperitoneally and implantation sites visualized. Gene expression patterns were compared with curated data sets to identify upstream regulators.

RESULTS

GEN-exposed mice exhibited reduced uterine weight gain in response to E2 treatment or artificial decidualization compared with controls; however, expression of select hormone responsive genes remained similar between the two groups. Uteri from pregnant GEN-exposed mice were posteriorized and had reduced glandular epithelium. Implantation failure was not rescued by LIF administration. Microarray analysis of GEN-exposed uteri during early pregnancy revealed significant overlap with several conditional uterine knockout mouse models, including Foxa2, Wnt4, and Sox17. These models exhibit reduced endometrial glands, features of posteriorization and implantation failure. Expression of Foxa2, Wnt4, and Sox17, as well as genes important for neonatal uterine differentiation (Wnt7a, Hoxa10, and Msx2), were severely disrupted on PND5 in GEN-exposed mice.

DISCUSSION

Our findings suggest that neonatal GEN exposure in mice disrupts expression of genes important for uterine development, causing posteriorization and diminished gland function during pregnancy that contribute to implantation failure. These findings could have implications for women who consumed soy-based formulas as infants. https://doi.org/10.1289/EHP6336.

Consensus on the key characteristics of endocrine-disrupting chemicals as a basis for hazard identification

Endocrine-disrupting chemicals (EDCs) are exogenous chemicals that interfere with hormone action, thereby increasing the risk of adverse health outcomes, including cancer, reproductive impairment, cognitive deficits and obesity. A complex literature of mechanistic studies provides evidence on the hazards of EDC exposure, yet there is no widely accepted systematic method to integrate these data to help identify EDC hazards. Inspired by work to improve hazard identification of carcinogens using key characteristics (KCs), we have developed ten KCs of EDCs based on our knowledge of hormone actions and EDC effects. In this Expert Consensus Statement, we describe the logic by which these KCs are identified and the assays that could be used to assess several of these KCs. We reflect on how these ten KCs can be used to identify, organize and utilize mechanistic data when evaluating chemicals as EDCs, and we use diethylstilbestrol, bisphenol A and perchlorate as examples to illustrate this approach.

Endocrine Disruption and Reproductive Pathology

During the past 20 years, investigations involving endocrine active substances (EAS) and reproductive toxicity have dominated the landscape of ecotoxicological research. This has occurred in concert with heightened awareness in the scientific community, general public, and governmental entities of the potential consequences of chemical perturbation in humans and wildlife. The exponential growth of experimentation in this field is fueled by our expanding knowledge into the complex nature of endocrine systems and the intricacy of their interactions with xenobiotic agents. Complicating factors include the ever-increasing number of novel receptors and alternate mechanistic pathways that have come to light, effects of chemical mixtures in the environment versus those of single EAS laboratory exposures, the challenge of differentiating endocrine disruption from direct cytotoxicity, and the potential for transgenerational effects. Although initially concerned with EAS effects chiefly in the thyroid glands and reproductive organs, it is now recognized that anthropomorphic substances may also adversely affect the nervous and immune systems via hormonal mechanisms and play substantial roles in metabolic diseases, such as type 2 diabetes and obesity.

Identification of a pituitary ERα-activated enhancer triggering the expression of Nr5a1, the earliest gonadotrope lineage-specific transcription factor

Background

Gonadotrope lineage differentiation is a stepwise process taking place during pituitary development. The early step of gonadotrope lineage specification is characterized by the expression of the Nr5a1 transcription factor, a crucial factor for gonadotrope cell fate determination. Abnormalities affecting Nr5a1 expression lead to hypogonadotropic hypogonadism and infertility. Although significant knowledge has been gained on the signaling and transcriptional events controlling gonadotrope differentiation, epigenetic mechanisms regulating Nr5a1 expression during early gonadotrope lineage specification are still poorly understood.

Results

Using ATAC chromatin accessibility analyses on three cell lines recapitulating gradual stages of gonadotrope differentiation and in vivo on developing pituitaries, we demonstrate that a yet undescribed enhancer is transiently recruited during gonadotrope specification. Using CRISPR/Cas9, we show that this enhancer is mandatory for the emergence of Nr5a1 during gonadotrope specification. Furthermore, we identify a highly conserved estrogen-binding element and demonstrate that the enhancer activation is dependent upon estrogen acting through ERα. Lastly, we provide evidence that binding of ERα is crucial for chromatin remodeling of Nr5a1 enhancer and promoter, leading to RNA polymerase recruitment and transcription.

Conclusion

This study identifies the earliest regulatory sequence involved in gonadotrope lineage specification and highlights the key epigenetic role played by ERα in this differentiation process.

Electronic supplementary material

The online version of this article (10.1186/s13072-019-0291-8) contains supplementary material, which is available to authorized users.

A distal super enhancer mediates estrogen-dependent mouse uterine-specific gene transcription of Igf1 (insulin-like growth factor 1)

Insulin-like growth factor 1 (IGF1) is primarily synthesized in and secreted from the liver; however, estrogen (E2), through E2 receptor α (ERα), increases uterine Igf1 mRNA levels. Previous ChIP-seq analyses of the murine uterus have revealed a potential enhancer region distal from the Igf1 transcription start site (TSS) with multiple E2-dependent ERα-binding regions. Here, we show E2-dependent super enhancer-associated characteristics and suggest contact between the distal enhancer and the Igf1 TSS. We hypothesized that this distal super-enhancer region controls E2-responsive induction of uterine Igf1 transcripts. We deleted 430 bp, encompassing one of the ERα-binding sites, thereby disrupting interactions of the enhancer with gene-regulatory factors. As a result, E2-mediated induction of mouse uterine Igf1 mRNA is completely eliminated, whereas hepatic Igf1 expression remains unaffected. This highlights the central role of a distal enhancer in the assembly of the factors necessary for E2-dependent interaction with the Igf1 TSS and induction of uterus-specific Igf1 transcription. Of note, loss of the enhancer did not affect fertility or uterine growth responses. Deletion of uterine Igf1 in a PgrCre;Igf1f/f model decreased female fertility but did not impact the E2-induced uterine growth response. Moreover, E2-dependent activation of uterine IGF1 signaling was not impaired by disrupting the distal enhancer or by deleting the coding transcript. This indicated a role for systemic IGF1, suggested that other growth mediators drive uterine response to E2, and suggested that uterine-derived IGF1 is essential for reproductive success. Our findings elucidate the role of a super enhancer in Igf1 regulation and uterine growth.

Effect of single-nucleotide polymorphisms on specific reproduction parameters in Hungarian Large White sows

The aim of this study was to reveal the effect of single-nucleotide polymorphisms (SNPs) on the total number of piglets born (TNB), the litter weight born alive (LWA), the number of piglets born dead (NBD), the average litter weight on the 21st day (M21D) and the interval between litters (IBL). Genotypes were determined on a high-density Illumina Porcine SNP 60K BeadChip. Data screening and data identification were performed by a multi-locus mixed-model. Statistical analyses were carried out to find associations between individual genotypes of 290 Hungarian Large White sows and the investigated reproduction parameters. According to the analysis outcome, three SNPs were identified to be associated with TNB. These loci are located on chromosomes 1, 6 and 13 (-log₁₀P = 6.0, 7.86 and 6.22, the frequencies of their minor alleles, MAF, were 0.298, 0.299 and 0.364, respectively). Two loci showed considerable association (-log₁₀P = 10.35 and 10.46) with LWA on chromosomes 5 and X, the MAF were 0.425 and 0.446, respectively. Seven loci were found to be associated with NBD. These loci are located on chromosomes 5, 6, 13, 14, 15, 16 and 18 (-log₁₀P = 10.95, 5.43, 8.29, 6.72, 6.81, 5.90, and 5.15, respectively). One locus showed association (-log₁₀P = 5.62) with M21D on chromosome 1 (the MAF was 0.461). Another locus was found to be associated with IBL on chromosome 8 (-log₁₀P = 7.56; the MAF was 0.438). The above-mentioned loci provide a straightforward possibility to assist selection by molecular tools and, consequently, to improve the competitiveness of the Hungarian Large White (HLW) breed.

Estrogenic Effect of the Extract of QingYan Formula on Reproductive Tissues in Immature Mice

A Chinese herbal preparation, QingYan formula (QYF), has been used clinically for kidney-invigorating. However, no evidence base links QYF to estrogen replacement therapy. In this study, the estrogenic effects of QingYan formula 70% ethanol extract (QYFE) were investigated in immature mice. Immature mice were treated with QYFE at doses of 1, 2, and 4g/kg for 7 days. QYFE treatments promoted vaginal cornification and prolonged the estrus status of the immature mice, promoted the growth and development of uterus and vagina, upregulated ERα and ERβ expression at protein level in uterus and vagina, increased the level of estradiol (E₂), and decreased concentration of luteinizing hormone (LH) and follicle-stimulating hormone (FSH) in serum. This study demonstrated that QYFE exerts estrogenic effects by stimulating biosynthesis of estrogen and increasing estrogen receptors (ERs) in target tissues and provided an evidence base for QYFE treatment instead of estrogen replacement therapy.

Epigenetic disruption of estrogen receptor alpha is induced by a glyphosate-based herbicide in the preimplantation uterus of rats

Previously, we have shown that perinatal exposure to a glyphosate-based herbicide (GBH) induces implantation failures in rats. Estrogen receptor alpha (ERα) is critical for successful implantation. ERα transcription is under the control of five promoters (E1, OT, O, ON, and OS), which yield different transcripts. Here, we studied whether perinatal exposure to a GBH alters uterine ERα gene expression and prompts epigenetic modifications in its regulatory regions during the preimplantation period. Pregnant rats (F0) were orally treated with 350 mg glyphosate/kg bw/day through food from gestational day (GD) 9 until weaning. F1 females were bred, and uterine samples were collected on GD5 (preimplantation period). ERα mRNA levels and its transcript variants were evaluated by RT-qPCR. Enzyme-specific restriction sites and predicted transcription factors were searched in silico in the ERα promoter regions to assess the methylation status using the methylation-sensitive restriction enzymes-PCR technique. Post-translational modifications of histones were studied by the chromatin immunoprecipitation assay. GBH upregulated the expression of total ERα mRNA by increasing the abundance of the ERα-O transcript variant. In addition, different epigenetic changes were detected in the O promoter. A decrease in DNA methylation was observed in one of the three sites evaluated in the O promoter. Moreover, histone H4 acetylation and histone H3 lysine 9 trimethylation (H3K9me3) were enriched in the O promoter in GBH-exposed rats, whereas H3K27me3 was decreased. All these alterations could account for the increase in ERα gene expression. Our findings show that perinatal exposure to a GBH causes long-term epigenetic disruption of the uterine ERα gene, which could be associated with the GBH-induced implantation failures.