Membrane-Localized Estrogen Receptor 1 Is Required for Normal Male Reproductive Development and Function in Mice

Role for Nongenomic Estrogen Signaling in Male Fertility

Estrogen actions are mediated by both nuclear (n) and membrane (m) localized estrogen receptor 1 (ESR1). Male Esr1 knockout (Esr1KO) mice lacking functional Esr1 are infertile, with reproductive tract abnormalities. Male mice expressing nESR1 but lacking mESR1 (nuclear-only estrogen receptor 1 mice) are progressively infertile due to testicular, rete testis, and efferent ductule abnormalities similar to Esr1KO males, indicating a role for mESR1 in male reproduction. The H2NES mouse expresses only mESR1 but lacks nESR1. The goal of this study was to identify the functions of mESR1 alone in mice where nESR1 was absent. Breeding trials showed that H2NES males are fertile, with decreased litter numbers but normal pup numbers/litter. In contrast to Esr1KO mice, H2NES testicular, and epididymal weights were not reduced, and seminiferous tubule abnormalities were less pronounced. However, Esr1KO and H2NES males both had decreased sperm motility and a high incidence of abnormal sperm morphology. Seminiferous tubule and rete testis dilation and decreased efferent ductule epithelial height characteristic of Esr1KO males were reduced in H2NES. Consistent with this, expression of genes involved in fluid transport and ion movement that were reduced in Esr1KO (Aqp1, Car2, Car14, Cftr) were partially or fully restored to wild-type levels in H2NES. In summary, in contrast to Esr1KO males, H2NES males are fertile and have reduced phenotypic and functional abnormalities in the testis and efferent ductules. Thus, mESR1 alone, in the absence of nESR1, can partially regulate male reproductive tract structure and function, emphasizing its importance for overall estrogen action.

Functions of Steroid Hormones in the Male Reproductive Tract as Revealed by Mouse Models

Steroid hormones are capable of diffusing through cell membranes to bind with intracellular receptors to regulate numerous physiological processes. Three classes of steroid hormones, namely androgens, estrogens and glucocorticoids, contribute to the development of the reproductive system and the maintenance of fertility. During the past 30 years, mouse models have been produced in which the expression of genes encoding steroid hormone receptors has been enhanced, partially compromised or eliminated. These mouse models have revealed many of the physiological processes regulated by androgens, estrogens and to a more limited extent glucocorticoids in the testis and male accessory organs. In this review, advances provided by mouse models that have facilitated a better understanding of the molecular regulation of testis and reproductive tract processes by steroid hormones are discussed.

Maternal exposure of rats to sodium saccharin during gestation and lactation on male offspring†

We investigated the effects of fetal programming in Sprague-Dawley rats through the maternal consumption of sodium saccharin on the testicular structure and function in male offspring. Feed intake and efficiency, organ and fat weight, quantification and expression of androgen receptor (AR), and proliferating cell nuclear antigen (PCNA) proteins, sperm count, and hormone levels were determined. Consumption alterations were found in the final weeks of the experiment. Decreases in AR and PCNA expression and quantification, tubular diameter, and luminal volume, and increases in epithelial and interstitial relative volumes were observed. Lower sperm count and transit, and lower estradiol concentration were also found. Sodium saccharin consumption by dams programmed male offspring by affecting the hypothalamic-pituitary-gonad axis with alterations in the Sertoli cell population, in spermatogonia proliferation, the expression and quantification of AR, and in sperm count. We hypothesized that these changes may be due to an estradiol reduction that caused the loosening of adhesion junctions of the blood-testis barrier, causing cell losses during spermatogenesis, also reflected by a decrease in tubular diameter with an increase in epithelial volume and consequent decrease in luminal volume. We conclude that maternal sodium saccharin consumption during pregnancy and lactation programmed alterations in the reproductive parameters of male offspring, thus influencing spermatogenesis.

Cathepsin B plays a role in spermatogenesis and sperm maturation through regulating autophagy and apoptosis in mice

Spermatogenesis and sperm maturation are complex and highly ordered biological processes. Any failure or disorder in these processes can cause defects in sperm morphology, motility, and fertilization ability. Cathepsin B (CTSB) is involved in the regulation of a variety of pathological processes. In the present study, we found that CTSB was abundantly expressed in the male reproductive system, however, the specific role of CTSB in regulating spermatogenesis and sperm maturation remained elusive. Hence, we generated Ctsb ^-/- mice using CRISPR/Cas9 technology. In Ctsb ^-/- mice, sperm count was significantly decreased while the level of morphologically abnormal sperm was markedly increased. Additionally, these mice had significantly lower levels of progressive motility sperm and elevated levels of immobilized sperm. Histological analysis showed slight vacuolization in the testis epithelium, as well as the loss of epididymal epithelium cells. Further investigation showed that autophagic activity was inhibited and apoptotic activity was increased in both the testis and epididymis of Ctsb ^-/- mice. Together, our findings demonstrate that CTSB plays an important role in spermatogenesis and sperm maturation in mice.

Sirt3 deficiency accelerates ovarian senescence without affecting spermatogenesis in aging mice

Sirtuin-3 (SIRT3), the main deacetylase in the mitochondria, maintains cellular energy metabolism and redox balance by deacetylating mitochondrial proteins in a NAD⁺-dependent manner. Growing evidence indicates that decreased Sirt3 expression is involved in various age-related maladies. However, the role of Sirt3 in ovarian and testicular senescence remains unclear. In this study, we observed that sirt3 expression showed age-dependent decreases in the ovary but not the testis. We generated Sirt3 null mice via CRISPR/Cas9-mediated genome editing. We observed that Sirt3 deletion accelerated ovarian aging, as shown by a decrease in offspring sizes, the follicle reserve and oocytes markers (Bmp15 and Gdf9) as well as increased expression of aging and inflammation-related genes (p16, p21, Il-1α, and Il-1β). Sirt3 deficiency led to an accumulation of superoxide and disruption of spindle assembly accompanied by mitochondrial dysfunction (uneven mitochondria distribution, decreased mitochondrial potential as well as reduced mitochondrial DNA content) in aging oocytes. Meanwhile, in ovaries of Sirt3 null mice, the impaired mitochondrial functions were shown by decreases in mitochondrial respiratory complexes, along with lower levels of mitochondrial fusion (OPA1, MFN2) and fission (DRP1, FIS1) proteins. er levels of mitochondrial fusion (OPA1, MFN2) and fission (DRP1, FIS1) proteins. Interestingly, Sirt3^-/- male mice exhibited no changes on the testicular histology, serum testosterone levels, germ-cell proliferation, and differentiation of spermatogonia. Meiotic prophase I spermatocytes were also normal. Levels of superoxide, mitochondrial potential as well as expression of mitochondrially-encoded genes were unaltered in Sirt3^-/- testes. Collectively, the results indicated that SIRT3 plays a critical role in maintaining the ovarian follicle reserve and oocyte quality in aging mice, suggesting its important role in controlling ovarian senescence.

Pharmacological Inhibition of Inositol Hexakisphosphate Kinase 1 Protects Mice against Obesity-Induced Bone Loss

Obesity and type II diabetes mellitus (T2DM) are prominent risk factors for secondary osteoporosis due to the negative impacts of hyperglycemia and excessive body fat on bone metabolism. While the armamentarium of anti-diabetic drugs is expanding, their negative or unknown impacts on bone metabolism limits effectiveness. The inactivation of inositol hexakisphosphate kinase 1 (IP6K1) protects mice from high-fat-diet (HFD)-induced obesity (DIO) and insulin resistance by enhancing thermogenic energy expenditure, but the role of this kinase and the consequences of its inhibition on bone metabolism are unknown. To determine if IP6K1 inhibition in obese mice affords protection against obesity-induced metabolic derangements and bone loss, we maintained 2-month-old mice on a normal chow control diet or HFD under thermal neutral conditions for 100 d. Beginning on day 40, HFD-fed mice were divided into two groups and administered daily injections of vehicle or the pan-IP6K inhibitor TNP [N2-(m-Trifluorobenzyl), N6-(p-nitrobenzyl) purine]. HFD-fed mice developed obesity, hyperglycemia, hyperlipidemia, and secondary osteoporosis, while TNP administration protected mice against HFD-induced metabolic and lipid derangements and preserved bone mass, mineral density, and trabecular microarchitecture, which correlated with reduced serum leptin levels, reduced marrow adiposity, and preservation of marrow resident skeletal stem/progenitor cells (SSPCs). TNP also exhibited hypotensive activity, an unrealized benefit of the drug, and its prolonged administration had no adverse impacts on spermatogenesis. Together, these data indicate that the inhibition of IP6K1 using selective inhibitors, such as TNP, may provide an effective strategy to manage obesity and T2DM due to its bone sparing effects.

Estrogens: Two nuclear receptors, multiple possibilities

Much is known about estrogen action in experimental animal models and in human physiology. This article reviews the mechanisms of estrogen activity in animals and humans and the role of its two receptors α and β in terms of structure and mechanisms of action in various tissues in health and in relationship with human pathologies (e.g., osteoporosis). Recently, the spectrum of clinical pictures of estrogen resistance caused by estrogen receptors gene variants has been widened by our description of a woman with β-receptor defect, which could be added to the already known descriptions of α-receptor defect in women and men and β-receptor defect in men. The essential role of the β-receptor in the development of the gonad stands out. We summarize the clinical pictures due to estrogen resistance in men and women and focus on long-term follow-up of two women, one with α- and the other with β-receptor resistance. Some open questions remain on the complex interactions between the two receptors on bone metabolism and hypothalamus-pituitary-gonadal axis, which need further deepening and research.

Prenatal exposure to bisphenol S and bisphenol A differentially affects male reproductive system in the adult offspring

Early exposure to bisphenol may result in adverse reproductive health in later life. The use of bisphenol S (BPS) has increased considerably after bisphenol A (BPA) is regulated worldwide. However, little is known about the fetal exposure to BPS compared with BPA and its effects on the reproductive system in the adult male offspring. Here, we investigated the effects of orally administered BPS and BPA (0.4, 4.0, 40.0 μg/kg bw/d) during gestation (gD4-21) on testicular development by evaluating the sperm DNA damage & methylation and testicular functions in the 90 d Wistar rats. Male offspring prenatally exposed to BPS (0.4 μg/kg) had higher plasma testosterone than BPA and control. The testis histology reveals thickened membrane by producing a wide interstitial gap between seminiferous tubules, increased testicular inflammation, oxidative stress, TIMP-1 expression, and decreased VCAM-1 expression. BPS promotes apoptosis by up-regulating IL-6, cleaved caspases, and a spike in sperm DNA fragmentation. Prenatal BPS exposure reduces sperm motility mediated via impaired PI3K-AKT signaling and increases testicular TEX11 expression in the offspring. Exposure of the fetus to BPS interferes developmental programming of the male reproductive system in the offspring. BPS could be an equally potent endocrine disruptor affecting male reproductive functions.

Membrane-Initiated Estrogen, Androgen, and Progesterone Receptor Signaling in Health and Disease

Rapid effects of steroid hormones were discovered in the early 1950s, but the subject was dominated in the 1970s by discoveries of estradiol and progesterone stimulating protein synthesis. This led to the paradigm that steroid hormones regulate growth, differentiation, and metabolism via binding a receptor in the nucleus. It took 30 years to appreciate not only that some cellular functions arise solely from membrane-localized steroid receptor (SR) actions, but that rapid sex steroid signaling from membrane-localized SRs is a prerequisite for the phosphorylation, nuclear import, and potentiation of the transcriptional activity of nuclear SR counterparts. Here, we provide a review and update on the current state of knowledge of membrane-initiated estrogen (ER), androgen (AR) and progesterone (PR) receptor signaling, the mechanisms of membrane-associated SR potentiation of their nuclear SR homologues, and the importance of this membrane-nuclear SR collaboration in physiology and disease. We also highlight potential clinical implications of pathway-selective modulation of membrane-associated SR.

Paternal alcohol consumption has intergenerational consequences in male offspring

PURPOSE

Alcoholism is a heterogeneous set of disorders caused by ethanol intake. Harmful effects of paternal consumption on the offspring are poorly explored and not fully understood. We analyzed the effect of paternal alcohol consumption on both their own reproductive capacity and that of their male offspring.

METHODS

We used a model of ethanol consumption (15% v/v in drinking water) for 12 days in adult CF-1 male mice. DNA integrity and post-translational modifications of histones were assessed in sperm; testicular weight, histology, and DNA fragmentation were analyzed. Treated or untreated male mice were mated with non-treated females to obtain two cell embryos that were cultured for 7 days; morphology and embryonic cell death were evaluated. Males of both groups were mated with non-treated females. Adult male offspring was euthanized, and sperm and testicular parameters determined.

RESULTS

Paternal ethanol consumption caused histological and epigenetic changes, as well as damage in DNA integrity in the testicular germline and sperm. These alterations gave rise to deleterious effects on embryonic development and to testicular and spermatic changes in the offspring.

CONCLUSION

This study provides critical information on reproductive disturbances brought about by paternal alcohol consumption and the profound impact these could have on the male progeny. The need to explore the effects of paternal alcohol consumption in detail and warn about the importance of controlling alcohol intake for the well-being of future generations should not be underscored.

Regulation of AKT Signaling in Mouse Uterus

17β-estradiol (E2) treatment of ovariectomized adult mice stimulates the uterine PI3K-AKT signaling pathway and epithelial proliferation through estrogen receptor 1 (ESR1). However, epithelial proliferation occurs independently of E2/ESR1 signaling in neonatal uteri. Similarly, estrogen-independent uterine epithelial proliferation is seen in adulthood in mice lacking Ezh2, critical for histone methylation, and in wild-type (WT) mice treated neonatally with estrogen. The role of AKT in estrogen-independent uterine epithelial proliferation was the focus of this study. Expression of the catalytically active phosphorylated form of AKT (p-AKT) and epithelial proliferation were high in estrogen receptor 1 knockout and WT mice at postnatal day 6, when E2 concentrations were low, indicating that neither ESR1 nor E2 are essential for p-AKT expression and epithelial proliferation in these mice. However, p-AKT levels and proliferation remained estrogen responsive in preweaning WT mice. Expression of p-AKT and proliferation were both high in uterine luminal epithelium of mice estrogenized neonatally and ovariectomized during adulthood. Increased expression of phosphorylated (inactive) EZH2 was also observed. Consistent with this, Ezh2 conditional knockout mice show ovary-independent uterine epithelial proliferation and high epithelial p-AKT. Thus, adult p-AKT expression is constitutive and E2/ESR1 independent in both model systems. Finally, E2-induced p-AKT expression and normal uterine proliferation did not occur in mice lacking membrane (m)ESR1, indicating a key role for membrane ESR1 in AKT activation. These findings emphasize the importance of AKT activation in promoting uterine epithelial proliferation even when that proliferation is not E2/ESR1 dependent and further indicate that p-AKT can be uncoupled from E2/ESR1 signaling in several experimental scenarios.

Segregation of nuclear and membrane-initiated actions of estrogen receptor using genetically modified animals and pharmacological tools

Estrogen receptor alpha (ERα) and beta (ERβ) are members of the nuclear receptor superfamily, playing widespread functions in reproductive and non-reproductive tissues. Beside the canonical function of ERs as nuclear receptors, in this review, we summarize our current understanding of extra-nuclear, membrane-initiated functions of ERs with a specific focus on ERα. Over the last decade, in vivo evidence has accumulated to demonstrate the physiological relevance of this ERα membrane-initiated-signaling from mouse models to selective pharmacological tools. Finally, we discuss the perspectives and future challenges opened by the integration of extra-nuclear ERα signaling in physiology and pathology of estrogens.

The Rete Testis: Development and Role in Testis Function

Abstract

The rete testis connects seminiferous tubules in which germ cells develop to the efferent ducts and the epididymis, where gametes mature and gain mobility. Several recent studies have thoroughly explored the morphogenesis of this structure in mice during embryonic and postnatal periods. A part of the rete testis has been shown to derive from the precursors of gonad somatic cells before sex determination. The other part forms from embryonal Sertoli cells of testis cords adjacent to the mesonephros. The transformation of Sertoli cells into rete testis cells is apparently not limited to the embryonic stage of development and continues during postnatal testis development. Recently, it was found that the rete testis participates in the formation and maintenance of specialized Sertoli cells in terminal segments of seminiferous tubules, transitional zones. Current views suggest that the transitional zones of the seminiferous tubules may represent a niche for spermatogonial stem cells, the site of the prolonged proliferation of Sertoli cells in the pubertal and postpubertal periods of testis development, and also could be a generator of spermatogenic waves. To sum up, the rete testis transports gametes from the testis to the epididymis, maintains pressure within seminiferous tubules, regulates the composition of the testicular fluid, and impacts the spermatogenic process itself.

The extra-nuclear interactome of the estrogen receptors: implications for physiological functions

Over the last decades, a great body of evidence has defined a novel view of the cellular mechanism of action of the steroid hormone 17β-estradiol (E2) through its estrogen receptors (i.e., ERα and ERβ). It is now clear that the E2-activated ERs work both as transcription factors and extra-nuclear plasma membrane-localized receptors. The activation of a plethora of signal transduction cascades follows the E2-dependent engagement of plasma membrane-localized ERs and is required for the coordination of gene expression, which ultimately controls the occurrence of the pleiotropic effects of E2. The definition of the molecular mechanisms by which the ERs locate at the cell surface (i.e., palmitoylation and protein association) determined the quest for understanding the specificity of the extra-nuclear E2 signaling. The use of mice models lacking the plasma membrane ERα localization unveiled that the extra-nuclear E2 signaling is operational in vivo but tissue-specific. However, the underlying molecular details for such ERs signaling diversity in the perspective of the E2 physiological functions in the different cellular contexts are still not understood. Therefore, to gain insights into the tissue specificity of the extra-nuclear E2 signaling to physiological functions, here we reviewed the known ERs extra-nuclear interactors and tried to extrapolate from available databases the ERα and ERβ extra-nuclear interactomes. Based on literature data, it is possible to conclude that by specifically binding to extra-nuclear localized proteins in different sub-cellular compartments, the ERs fine-tune their molecular activities. Moreover, we report that the context-dependent diversity of the ERs-mediated extra-nuclear E2 actions can be ascribed to the great flexibility of the physical structures of ERs and the spatial-temporal organization of the logistics of the cells (i.e., the endocytic compartments). Finally, we provide lists of proteins belonging to the potential ERα and ERβ extra-nuclear interactomes and propose that the systematic experimental definition of the ERs extra-nuclear interactomes in different tissues represents the next step for the research in the ERs field. Such characterization will be fundamental for the identification of novel druggable targets for the innovative treatment of ERs-related diseases.

Weighted gene coexpression network analysis reveals ESR1, FLNA and Furin as hub genes for DEHP-induced prepubertal testicular injury

Di-(2-ethylhexyl) phthalate (DEHP) is an environmental endocrine disruptor that accumulates in organisms in various ways and induces male reproductive system disorders. In this study, we established a testicular injury model by gavage with different concentrations of DEHP. The testes were then collected for RNA sequencing (RNA-seq), and the results were analyzed by bioinformatics and verified by experiments. Our research results show that different concentrations of DEHP interfere with testicular development differently. Weighted gene coexpression network analysis (WGCNA) generated sixteen modules and identified the turquoise module as key. Then, estrogen receptor 1 (ESR1), filamin A (Flna) and Furin were identified as hub genes. qPCR and immunohistochemistry results revealed that all three hub genes were upregulated. We detected the locations of these genes by immunohistochemistry. ESR1 was mainly located in Leydig cells; Flna immunostaining is observed in the Leydig and some germ cells and Furin staining was seen in almost all types of testicular cells. Furthermore, Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analyses showed enrichment mainly in MAPK signaling pathways, p53 signaling pathways, HIF-1 signaling pathways, protein processing in the endoplasmic reticulum, apoptosis, the cell cycle, RNA degradation, etc. This is the first study using WGCNA to investigate the mechanism of DEHP-induced injury in the prepubertal testis, providing new research angles to further understand the mechanism of DEHP-induced injury in the prepubertal testis.

Multiple Lesions Contribute to Infertility in Males Lacking Autoimmune Regulator

Male factors, including those of autoimmune origin, contribute to approximately 50% of infertility cases in humans. However, the mechanisms underlying autoimmune male infertility are poorly understood. Deficiency in autoimmune regulator (AIRE) impairs central immune tolerance because of diminished expression of self-antigens in the thymus. Humans with AIRE mutations and mice with engineered ablation of Aire develop multiorgan autoimmunity and infertility. To determine the immune targets contributing to infertility in male Aire-deficient (-/-) mice, Aire-/- or wild-type (WT) males were paired with WT females. Aire-/- males exhibited dramatically reduced mating frequency and fertility, hypogonadism, and reduced serum testosterone. Approximately 15% of mice exhibited lymphocytic infiltration into the testis, accompanied by atrophy, azoospermia, and reduced numbers of mitotically active germ cells; the remaining mice showed normal testicular morphology, sperm counts, and motility. However, spermatozoa from all Aire-/- mice were defective in their ability to fertilize WT oocytes in vitro. Lymphocytic infiltration into the epididymis, seminal vesicle, and prostate gland was evident. Aire-/- male mice generated autoreactive antibodies in an age-dependent manner against sperm, testis, epididymis, prostate gland, and seminal vesicle. Finally, expression of Aire was evident in the seminiferous epithelium in an age-dependent manner, as well as in the prostate gland. These findings suggest that Aire-dependent central tolerance plays a critical role in maintaining male fertility by stemming autoimmunity against multiple reproductive targets.

Male fertility in mice requires classical and nonclassical androgen signaling

Molecular mechanisms by which androgens signal through the androgen receptor (AR) to maintain male fertility are poorly understood. Transgenic mice were produced expressing mutant ARs that can only (1) alter gene transcription through the classical response pathway (AR-C) or (2) activate kinase signaling cascades via the nonclassical pathway (AR-NC). AR-C is sufficient to produce sperm and fertility. Haploid germ cell production, the blood-testis barrier, and spermatid migration are supported by AR-NC. Gene expression essential for chromosome synapsis during meiosis requires AR-C. We identify targets of androgen signaling required for male fertility and provide a mechanistic explanation for meiotic germ cell arrest in the absence of androgen signaling. Prostate differentiation occurs with AR-C alone, but full development requires synergistic nonclassical signaling. Both AR signaling pathways are necessary for normal male reproductive tract development and function, validating our mouse models for studies of AR functions in other target tissues.

Nonclassical androgen and estrogen signaling is essential for normal spermatogenesis

Signaling by androgens through androgen receptor (AR) is essential to complete spermatogenesis in the testis. Similarly, loss of the main estrogen receptor, estrogen receptor 1 (ESR1; also known as ERα), results in male infertility, due in part to indirect deleterious effects on the seminiferous epithelium and spermatogenesis. Effects of steroid hormones are induced primarily through genomic changes induced by hormone-mediated activation of their intracellular receptors and subsequent effects on nuclear gene transcription. However, androgens and estrogens also signal through rapid nonclassical pathways involving actions initiated at the cell membrane. Here we review the data that nonclassical androgen and estrogen signaling pathways support processes essential for male fertility in the testis and reproductive tract. The recent development of transgenic mice lacking nonclassical AR or ESR1 signaling but retaining genomic nuclear signaling has provided a powerful tool to elucidate the function of nonclassical signaling in the overall response to androgens and estrogens. Results from these mice have emphasized that nonclassical signaling is essential for full responses to these hormones, and absence of either nonclassical or classical AR or ESR1 pathways produces abnormalities in spermatogenesis and the male reproductive tract. Although additional work is required to fully understand how classical and nonclassical receptor signaling synergize to produce full steroid hormone responses, here we summarize the known physiological functions of the classical and nonclassical androgen and estrogen signaling pathways in the testis and reproductive tract.

Anatomy, Endocrine Regulation, and Embryonic Development of the Rete Testis

Reproduction in males requires the transfer of spermatozoa from testis tubules via the rete system to the efferent ductules, epididymis, and vas deferens. The rete therefore forms an essential bridging system between the testis and excurrent ducts. Yet the embryonic origin and molecular regulation of rete testis development is poorly understood. This review examines the anatomy, endocrine control, and development of the mammalian rete testis, focusing on recent findings on its molecular regulation, identifying gaps in our knowledge, and identifying areas for future research. The rete testis develops in close association with Sertoli cells of the seminiferous cords, although unique molecular markers are sparce. Most recently, modern molecular approaches such as global RNA-seq have revealed the transcriptional signature of rete cell precursors, pointing to at least a partial common origin with Sertoli cells. In the mouse, genes involved in Sertoli cell development or maintenance, such as Sox9, Wt1, Sf1, and Dmrt1, are also expressed in cells of the rete system. Rete progenitor cells also express unique markers, such as Pax8, E-cadherin, and keratin 8. These must directly or indirectly regulate the physical joining of testis tubules to the efferent duct system and confer other physiological functions of the rete. The application of technologies such as single-cell RNA-seq will clarify the origin and developmental trajectory of this essential component of the male reproductive tract.

A Potential Relationship Between Estrogen Receptors Polymorphisms, Sperm Function and in vitro Fertilization Success: A Preliminary Study*

Background: Estrogen receptor 1 (ESR1) and 2 (ESR2) play an important role in regulating fertility in the human reproductive system. Polymorphisms of these receptor genes have been implicated in male infertility in both Chinese and Caucasian populations. However, studies have produced inconsistent results. Spermatozoa defects that result in conception deficiencies could be related to estrogens, their receptors, or genes involved in estrogen-related pathways. This study aims to explore the potential association between the ESR1 and the ESR2 polymorphisms in relation to semen parameters of Caucasian males as well as fertilization success. Materials/Methods: A total of 116 males were included in this study. Forty couples underwent conventional in vitro fertilization, while 76 couples were treated by intracytoplasmic sperm injection. Standard semen analyses were performed according to the World Health Organization criteria. Polymerase chain reaction and restriction fragment length polymorphisms were used to determine genotype and allele distributions. Results: A strong association between the ESR1 rs2234693 recognized by PvuII enzyme, genotype/allele distribution and fertilization success was shown. The T allele occurrence was significantly lower in the case of fertilization failure (p = 0.02). Additionally, the TT genotype was absent in the same group (p=0.02). In the case of the remaining analyzed polymorphisms, little to no interdependence of genotype/allele distribution and fertilization success was noted. Conclusions: Apart from ESR1 rs2234693, the study failed to demonstrate that fertilization success was associated with the selected polymorphisms. In most cases, we did not discover a relationship between both estrogen receptors polymorphisms and sperm function.

Deficiency for Lcn8 causes epididymal sperm maturation defects in mice

Lipocalin family members, LCN8 and LCN9, are specifically expressed in the initial segment of mouse caput epididymis. However, the biological functions of the molecules in vivo are yet to be clarified. In this study, CRISPR/Cas9 technology was used to generate Lcn8 and Lcn9 knockout mice, respectively. Lcn8-/- and Lcn9-/- male mice showed normal spermatogenesis and fertility. In the cauda epididymis of Lcn8-/- male mice, morphologically abnormal sperm was increased significantly, the proportion of progressive motility sperm was decreased, the proportion of immobilized sperm was elevated, and the sperm spontaneous acrosome reaction (AR) frequency was increased. Conversely, the knockout of Lcn9 did not have any effect on the ratio of morphologically abnormal sperm, sperm motility, and sperm spontaneous AR frequencies. These results demonstrated the role of LCN8 in maintaining the sperm quality in the epididymis, and suggested that the deficiency of LCN8 leads to epididymal sperm maturation defects.

Sexual hormones and diabetes: The impact of estradiol in pancreatic β cell

Diabetes is one of the most prevalent metabolic diseases and its incidence is increasing throughout the world. Data from World Health Organization (WHO) point-out that diabetes is a major cause of blindness, kidney failure, heart attacks, stroke and lower limb amputation and estimated 1.6 million deaths were directly caused by it in 2016. Population studies show that the incidence of this disease increases in women after menopause, when the production of estrogen is decreasing in them. Knowing the impact that estrogenic signaling has on insulin-secreting β cells is key to prevention and design of new therapeutic targets. This chapter explores the role of estrogen and their receptors in the regulation of insulin secretion and biosynthesis, proliferation, regeneration and survival in pancreatic β cells. In addition, delves into the genetic animal models developed and its application for the specific study of the different estrogen signaling pathways. Finally, discusses the impact of menopause and hormone replacement therapy on pancreatic β cell function.

Dose-related morphological changes in the epididymal region of sexually active adult male Japanese quail treated with di-n-butyl phthalate (DBP) commencing during the pre-pubertal stage

Di-n-butyl phthalate (DBP) is widely used as a plasticizer in personal care and medical products and is known to induce toxicity in the male reproductive organs in both mammals and birds. In this study, there was investigation of the effects of DBP on the epithelium of the rete testis, proximal, and distal efferent ductules and epididymal duct of adult Japanese quail (Coturnix japonica) following treatment with varying doses during the pre-pubertal and peri-pubertal periods. Pre-pubertal quail (n = 25) 4 weeks post-hatching were dosed orally with 10, 50, 200 and 400 mg DBP/kg/d, for 30 days and control birds were administered corn-oil only (n = 5 per group). Histo-metrically, there was lesser (P <  0.001) epithelial heights of the rete testis and efferent ductules in all quail DBP-treated groups, but not in the epididymal duct epithelium. There were no morphological change effects as a result of DBP treatments in the rete testis epithelium, while there were epithelial cytoplasmic vacuoles detected in the distal efferent ductule and epididymal duct of birds treated with 50, 200 and 400 mg DPB/kg/d. There were several lesions, including degenerative changes, cytoplasmic vacuoles, apoptosis and autophagy in the epithelium of the proximal efferent ductule in quail treated with 200 and 400 mg DBP/kg/d. Overall, the results indicate that treatment with DBP during the pre-pubertal period induced dose-dependent histometric and morphological changes in the epithelium of the epididymal region. It is concluded that the proximal efferent ductule was a highly sensitive component of the epididymal tissues of Japanese quail following treatment with DBP during the pre-pubertal period.

Estrogens and development of the rete testis, efferent ductules, epididymis and vas deferens

Estrogen has always been considered the female hormone and testosterone the male hormone. However, estrogen's presence in the testis and deleterious effects of estrogen treatment during development have been known for nearly 90 years, long before estrogen receptors (ESRs) were discovered. Eventually it was learned that testes actually synthesize high levels of estradiol (E2) and sequester high concentrations in the reproductive tract lumen, which seems contradictory to the overwhelming number of studies showing reproductive pathology following exogenous estrogen exposures. For too long, the developmental pathology of estrogen has dominated our thinking, even resulting in the "estrogen hypothesis" as related to the testicular dysgenesis syndrome. However, these early studies and the development of an Esr1 knockout mouse led to a deluge of research into estrogen's potential role in and disruption of development and function of the male reproductive system. What is new is that estrogen action in the male cannot be divorced from that of androgen. This paper presents what is known about components of the estrogen pathway, including its synthesis and target receptors, and the need to achieve a balance between androgen- and estrogen-action in male reproductive tract differentiation and adult functions. The review focuses on what is known regarding development of the male reproductive tract, from the rete testis to the vas deferens, and examines the expression of estrogen receptors and presence of aromatase in the male reproductive system, traces the evidence provided by estrogen-associated knockout and transgenic animal models and discusses the effects of fetal and postnatal exposures to estrogens. Hopefully, there will be enough here to stimulate discussions and new investigations of the androgen:estrogen balance that seems to be essential for development of the male reproductive tract.

Role of nuclear and membrane estrogen signaling pathways in the male and female reproductive tract

Estrogen signaling through the main estrogen receptor, estrogen receptor 1 (ESR1; also known as ERα), is essential for normal female and male reproductive function. Historically, studies of estrogen action have focused on the classical genomic pathway. Although this is clearly the major pathway for steroid hormone actions, these hormones also signal through rapid non-classical effects involving cell membrane actions. Reports of rapid effects of estrogens extend for more than half a century, but recent results have expanded understanding of the identity, structure, function and overall importance of membrane receptors in estrogen responses. Key findings in this field were the immunohistochemical detection of ESR1 in cell membranes and demonstration that a portion of newly synthesized ESR1 is routed to the membrane by palmitoylation. These receptors in the membrane can then signal through protein kinases and other mechanisms following ligand binding to alter cell function. Another crucial advance in the field was development of transgenic mice expressing normal amounts of functional nuclear ESR1 (nESR1) but lacking membrane ESR1 (mESR1). Both male and female transgenic mice lacking mESR1 were infertile as adults, and both sexes had extensive reproductive abnormalities. Transgenic mice lacking mESR1 were highly protected from deleterious effects of neonatal estrogen administration, and estrogen effects on the histone methyltransferase Enhancer of Zeste homolog 2 that are mediated through mESR1 could have significant effects on epigenetic imprinting. In summary, signaling through mESR1 is essential for normal male and female reproductive function and fertility, and is a critical enabler of normal estrogen responses in vivo. Although the precise role of mESR1 in estrogen responses remains to be established, future research in this area should clarify its mechanism of action and lead to a better understanding of how mESR1 signaling works with classical genomic signaling through nESR1 to promote full estrogenic responses.

Transportin-2 plays a critical role in nucleocytoplasmic shuttling of oestrogen receptor-α

Oestrogen receptor-α (ERα) shuttles continuously between the nucleus and the cytoplasm, and functions as an oestrogen-dependent transcription factor in the nucleus and as an active mediator of signalling pathways, such as phosphatidylinositol 3-kinase (PI3K)/AKT, in the cytoplasm. However, little is known regarding the mechanism of ERα nucleocytoplasmic shuttling. In this study, we found that ERα is transported into the nucleus by importin-α/β1. Furthermore, we found that Transportin-2 (TNPO2) is involved in 17β-oestradiol (E2)-dependent cytoplasmic localisation of ERα. Interestingly, it was found that TNPO2 does not mediate nuclear export, but rather is involved in the cytoplasmic retention of ERα via the proline/tyrosine (PY) motifs. Moreover, we found that TNPO2 competitively binds to the basic nuclear localisation signal (NLS) of ERα with importin-α to inhibit importin-α/β-dependent ERα nuclear import. Finally, we confirmed that TNPO2 knockdown enhances the nuclear localisation of wild-type ERα and reduces PI3K/AKT phosphorylation in the presence of E2. These results reveal that TNPO2 regulates nucleocytoplasmic shuttling and cytoplasmic retention of ERα, so that ERα has precise functions depending on the stimulation.

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.

Mice lacking membrane estrogen receptor 1 are protected from reproductive pathologies resulting from developmental estrogen exposure†

Both membrane and nuclear fractions of estrogen receptor 1 (ESR1) mediate 17β-estradiol (E2) actions. Mice expressing nuclear (n)ESR1 but lacking membrane (m)ESR1 (nuclear-only estrogen receptor 1 [NOER] mice) show reduced E2 responsivity and reproductive abnormalities culminating in adult male and female infertility. Using this model, we investigated whether reproductive pathologies caused by the synthetic estrogen diethylstilbestrol (DES) are mitigated by mESR1 ablation. Homozygous and heterozygous wild-type (WT and HET, respectively) and NOER male and female mice were subcutaneously injected with DES (1 mg/kg body weight [BW]) or vehicle daily from postnatal day (PND) 1-5. Uterine histology was assessed in select DES-treated females at PND 5, whereas others were ovariectomized at PND 60 and treated with E2 (10 μg/kg BW) or vehicle 2 weeks later. Neonatal DES exposure resulted in ovary-independent epithelial proliferation in the vagina and uterus of WT but not NOER females. Neonatal DES treatment also induced ovary-independent adult expression of classical E2-induced transcripts (e.g., lactoferrin [Ltf] and enhancer of zeste homolog 2 [Ezh2]) in WT but not NOER mice. At PND 90, DES-treated WT and HET males showed smaller testes and a high incidence of bacterial pyogranulomatous inflammation encompassing the testes, epididymis and occasionally the ductus deferens with spread to lumbar lymph nodes; such changes were largely absent in NOER males. Results indicate that male and female NOER mice are protected from deleterious effects of neonatal DES, and thus mESR1 signaling is required for adult manifestation of DES-induced reproductive pathologies in both sexes.

Cdc14a has a role in spermatogenesis, sperm maturation and male fertility

Cdc14a is an evolutionarily conserved dual-specific protein phosphatase, and it plays different roles in different organisms. Cdc14a mutations in human have been reported to cause male infertility, while the specific role of Cdc14a in regulation of the male reproductive system remains elusive. In the present study, we established a knockout mouse model to study the function of Cdc14a in male reproductive system. Cdc14a^-/- male mice were subfertile and they could only produce very few offspring. The number of sperm was decreased, the sperm motility was impaired, and the proportion of sperm with abnormal morphology was elevated in Cdc14a^-/- mice. When we mated Cdc14a^-/- male mice with wild-type (WT) female mice, fertilized eggs could be found in female fallopian tubes, however, the majority of these embryos died during development. Some empty spaces were observed in seminiferous tubule of Cdc14a^-/- testes. Compared with WT male mice, the proportions of pachytene spermatocytes were increased and germ cells stained with γH2ax were decreased in Cdc14a^-/- male mice, indicating that knockout of Cdc14a inhibited meiotic initiation. Subsequently, we analyzed the expression levels of some substrate proteins of Cdc14a, including Cdc25a, Wee1, and PR-Set7, and compared those with WT testes, in which the expression levels of these proteins were significantly increased in Cdc14a^-/- testes. Our results revealed that Cdc14a^-/- male mice are highly subfertile, and Cdc14a is essential for normal spermatogenesis and sperm function.

Estrogens in Human Male Gonadotropin Secretion and Testicular Physiology From Infancy to Late Puberty

Several reports in humans as well as transgenic mouse models have shown that estrogens play an important role in male reproduction and fertility. Estrogen receptor alpha (ERα) and beta (ERβ) are expressed in different male tissues including the brain. The estradiol-binding protein GPER1 also mediates estrogen action in target tissues. In human testes a minimal ERα expression during prepuberty along with a marked pubertal up-regulation in germ cells has been reported. ERβ expression was detected mostly in spermatogonia, primary spermatocytes, and immature spermatids. In Sertoli cells ERβ expression increases with age. The aromatase enzyme (cP450arom), which converts androgens to estrogens, is widely expressed in human tissues (including gonads and hypothalamus), even during fetal life, suggesting that estrogens are also involved in human fetal physiology. Moreover, cP450arom is expressed in the early postnatal testicular Leydig cells and spermatogonia. Even though the aromatase complex is required for estrogen synthesis, its biological relevance is also related to the regulation of the balance between androgens and estrogens in different tissues. Knockout mouse models of aromatase (ArKO) and estrogen receptors (ERKOα, ERKOβ, and ERKOαβ) provide an important tool to study the effects of estrogens on the male reproductive physiology including the gonadal axis. High basal serum FSH levels were reported in adult aromatase-deficient men, suggesting that estrogens are involved in the negative regulatory gonadotropin feedback. However, normal serum gonadotropin levels were observed in an aromatase-deficient boy, suggesting a maturational pattern role of estrogen in the regulation of gonadotropin secretion. Nevertheless, the role of estrogens in primate testis development and function is controversial and poorly understood. This review addresses the role of estrogens in gonadotropin secretion and testicular physiology in male humans especially during childhood and puberty.

Estrogen in the male: a historical perspective

Estrogens have traditionally been considered female hormones. Nevertheless, the presence of estrogen in males has been known for over 90 years. Initial studies suggested that estrogen was deleterious to male reproduction because exogenous treatments induced developmental abnormalities. However, demonstrations of estrogen synthesis in the testis and high concentrations of 17β-estradiol in rete testis fluid suggested that the female hormone might have a function in normal male reproduction. Identification of estrogen receptors and development of biological radioisotope methods to assess estradiol binding revealed that the male reproductive tract expresses estrogen receptor extensively from the neonatal period to adulthood. This indicated a role for estrogens in normal development, especially in efferent ductules, whose epithelium is the first in the male reproductive tract to express estrogen receptor during development and a site of exceedingly high expression. In the 1990s, a paradigm shift occurred in our understanding of estrogen function in the male, ushered in by knockout mouse models where estrogen production or expression of its receptors was not present. These knockout animals revealed that estrogen's main receptor (estrogen receptor 1 [ESR1]) is essential for male fertility and development of efferent ductules, epididymis, and prostate, and that loss of only the membrane fraction of ESR1 was sufficient to induce extensive male reproductive abnormalities and infertility. This review provides perspectives on the major discoveries and developments that led to our current knowledge of estrogen's importance in the male reproductive tract and shaped our evolving concept of estrogen's physiological role in the male.

Impact of estrogens in males and androgens in females

Androgens and estrogens are known to be critical regulators of mammalian physiology and development. While these two classes of steroids share similar structures (in general, estrogens are derived from androgens via the enzyme aromatase), they subserve markedly different functions via their specific receptors. In the past, estrogens such as estradiol were thought to be most important in the regulation of female biology, while androgens such as testosterone and dihydrotestosterone were believed to primarily modulate development and physiology in males. However, the emergence of patients with deficiencies in androgen or estrogen hormone synthesis or actions, as well as the development of animal models that specifically target androgen- or estrogen-mediated signaling pathways, have revealed that estrogens and androgens regulate critical biological and pathological processes in both males and females. In fact, the concept of "male" and "female" hormones is an oversimplification of a complex developmental and biological network of steroid actions that directly impacts many organs. In this Review, we will discuss important roles of estrogens in males and androgens in females.

Endocrine disruption through membrane estrogen receptors and novel pathways leading to rapid toxicological and epigenetic effects

Estrogen binding to estrogen receptors (ESR) triggers signaling cascades within cells. Historically, a major emphasis has been characterizing estrogen-induced genomic actions resulting from binding to nuclear estrogen receptor 1 (nESR1). However, recent evidence indicates the first receptors estrogens encounter as they enter a cell, membrane ESR1 (mESR1), also play crucial roles. Membrane and nuclear ESR are derived from the same transcripts but the former are directed to the membrane via palmitoylation. Binding and activation of mESR1 leads to rapid fluctuations in cAMP and Ca+2 and stimulation of protein kinase pathways. Endocrine disrupting chemicals (EDC) that mimic 17β-estradiol can signal through mESR1 and elicit non-genomic effects. Most current EDC studies have focused on genomic actions via nESR1. However, increasing number of studies have begun to examine potential EDC effects mediated through mESR1, and some EDC might have higher potency for signaling through mESR1 than nESR1. The notion that such chemicals might also affect mESR1 signaling via palmitoylation and depalmitoylation pathways has also begun to gain currency. Recent development of transgenic mice that lack either mESR1 or nESR1, while retaining functional ESR1 in the other compartment, will allow more precise in vivo approaches to determine EDC effects through nESR1 and/or mESR1. It is increasingly becoming apparent in this quickly evolving field that EDC directly affect mESR and estrogen signaling, but such chemicals can also affect proportion of ESR reaching the membrane. Future EDC studies should be designed to consider the full range of effects through mESR alone and in combination with nESR.

History of Estrogen: Its Purification, Structure, Synthesis, Biologic Actions, and Clinical Implications

This mini-review summarizes key points from the Clark Sawin Memorial Lecture on the History of Estrogen delivered at Endo 2018 and focuses on the rationales and motivation leading to various discoveries and their clinical applications. During the classical period of antiquity, incisive clinical observations uncovered important findings; however, extensive anatomical dissections to solidify proof were generally lacking. Initiation of the experimental approach followed later, influenced by Claude Bernard's treatise "An Introduction to the Study of Experimental Medicine." With this approach, investigators began to explore the function of the ovaries and their "internal secretions" and, after intensive investigations for several years, purified various estrogens. Clinical therapies for hot flashes, osteoporosis, and dysmenorrhea were quickly developed and, later, methods of hormonal contraception. Sophisticated biochemical methods revealed the mechanisms of estrogen synthesis through the enzyme aromatase and, after discovery of the estrogen receptors, their specific biologic actions. Molecular techniques facilitated understanding of the specific transcriptional and translational events requiring estrogen. This body of knowledge led to methods to prevent and treat hormone-dependent neoplasms as well as a variety of other estrogen-related conditions. More recently, the role of estrogen in men was uncovered by prismatic examples of estrogen deficiency in male patients and by knockout of the estrogen receptor and aromatase in animals. As studies became more extensive, the effects of estrogen on nearly every organ were described. We conclude that the history of estrogen illustrates the role of intellectual reasoning, motivation, and serendipity in advancing knowledge about this important sex steroid.

Loss of Nuclear and Membrane Estrogen Receptor-α Differentially Impairs Insulin Secretion and Action in Male and Female Mice

Estrogens favor glucose homeostasis primarily through the estrogen receptor-α (ERα), but the respective importance of nuclear ERα (NOER) and membrane ERα (MOER) pools to glucose homeostasis are unknown. We studied glucose homeostasis, insulin secretion, and insulin sensitivity in male and female mice expressing either the NOER or the MOER. Male and female MOER mice exhibited fasting and fed hyperglycemia and glucose intolerance. Female MOER mice displayed impaired central insulin signaling associated with hyperinsulinemia and insulin resistance due to unrestrained hepatic gluconeogenesis, without alterations in glucose-stimulated insulin secretion (GSIS). In contrast, male MOER mice did not exhibit detectable insulin resistance, but showed impaired GSIS associated with reduced brain glucose sensing. Female NOER mice exhibited milder hepatic insulin resistance and glucose intolerance. In conclusion, nuclear ERα signaling is predominant in maintaining glucose homeostasis in mice of both sexes. Lack of nuclear ERα alters the central control of insulin sensitivity in females and predominantly impairs the central regulation of insulin secretion in males.

An increase of estrogen receptor α protein level regulates BDE-209-mediated blood-testis barrier disruption during spermatogenesis in F1 mice

Deca-bromodiphenyl ether (BDE-209) regulates various aspects of spermatogenesis and male fertility through its effect on estrogen receptor α (ERα), but the underlying mechanism remains unclear. Because molecular mechanisms such as remodeling of the blood-testis barrier (BTB) play crucial roles in spermatogenesis, we investigated the disruptive effects of ERα agonists on the BTB in spermatogenesis. In this study, 0, 300, and 500 mg/kg/day of BDE-209 were administered to pregnant adult mice by oral gavage from gestation day 7 to postnatal day 21. SerW3 cells were treated with methylpiperidino pyrazole (MPP) for 30 min before being treated with 50 μg/mL of BDE-209. BDE-209 increases ERα in time- and dose-dependent manners and decreases formin 1 and BTB-associated protein in F1 male mice. Furthermore, BDE-209 impairs the structure and function of the BTB. Activation of ERα signaling could disrupt the BTB, leading to spermatogenesis dysfunction. The results identified the role of ERα in BTB disruption during spermatogenesis and suggested that BTB disruption occurs because of exposure to BDE-209, which could potentially affect spermatogenesis. In conclusion, Sertoli cells seem to be the primary target of BDE-209 in the perinatal period, and this period constitutes a critical window of susceptibility to BDE-209. Also, the SerW3 cell model may not be a particularly useful cell model for studying the function of the cytoskeleton.

G Protein-Coupled Estrogen Receptor: A Potential Therapeutic Target in Cancer

The G protein-coupled estrogen receptor (GPER) is a seven-transmembrane-domain receptor that mediates non-genomic estrogen related signaling. After ligand activation, GPER triggers multiple downstream pathways that exert diverse biological effects on the regulation of cell growth, migration and programmed cell death in a variety of tissues. A significant correlation between GPER and the progression of multiple cancers has likewise been reported. Therefore, a better understanding of the role GPER plays in cancer biology may lead to the identification of novel therapeutic targets, especially among estrogen-related cancers. Here, we review cell signaling and detail the functions of GPER in malignancies.

Membrane estrogen receptor α is essential for estrogen signaling in the male skeleton

The importance of estrogen receptor α (ERα) for the regulation of bone mass in males is well established. ERα mediates estrogenic effects both via nuclear and membrane-initiated ERα (mERα) signaling. The role of mERα signaling for the effects of estrogen on bone in male mice is unknown. To investigate the role of mERα signaling, we have used mice (Nuclear-Only-ER; NOER) with a point mutation (C451A), which results in inhibited trafficking of ERα to the plasma membrane. Gonadal-intact male NOER mice had a significantly decreased total body areal bone mineral density (aBMD) compared to WT littermates at 3, 6 and 9 months of age as measured by dual-energy X-ray absorptiometry (DEXA). High-resolution microcomputed tomography (µCT) analysis of tibia in 3-month-old males demonstrated a decrease in cortical and trabecular thickness in NOER mice compared to WT littermates. As expected, estradiol (E2) treatment of orchidectomized (ORX) WT mice increased total body aBMD, trabecular BV/TV and cortical thickness in tibia compared to placebo treatment. E2 treatment increased these skeletal parameters also in ORX NOER mice. However, the estrogenic responses were significantly decreased in ORX NOER mice compared with ORX WT mice. In conclusion, mERα is essential for normal estrogen signaling in both trabecular and cortical bone in male mice. Increased knowledge of estrogen signaling mechanisms in the regulation of the male skeleton may aid in the development of new treatment options for male osteoporosis.

Estrogen Receptors: New Directions in the New Millennium

Nineteen years have passed since our previous review in this journal in 1999 regarding estrogen receptors. At that time, we described the current assessments of the physiological activities of estrogen and estrogen receptors. Since that time there has been an explosion of progress in our understanding of details of estrogen receptor-mediated processes from the molecular and cellular level to the whole organism. In this review we discuss the basic understanding of estrogen signaling and then elaborate on the progress and current understanding of estrogen receptor actions that have developed using new models and continuing clinical studies.

Estrogens regulate life and death in mitochondria

Estrogens coordinate and integrate cellular metabolism and mitochondrial activities by direct and indirect mechanisms mediated by differential expression and localization of estrogen receptors (ER) in a cell-specific manner. Estrogens regulate transcription and cell signaling pathways that converge to stimulate mitochondrial function- including mitochondrial bioenergetics, mitochondrial fusion and fission, calcium homeostasis, and antioxidant defense against free radicals. Estrogens regulate nuclear gene transcription by binding and activating the classical genomic estrogen receptors α and β (ERα and ERβ) and by activating plasma membrane-associated mERα, mERβ, and G-protein coupled ER (GPER, GPER1). Localization of ERα and ERβ within mitochondria and in the mitochondrial membrane provides additional mechanisms of regulation. Here we review the mechanisms of rapid and longer-term effects of estrogens and selective ER modulators (SERMs, e.g., tamoxifen (TAM)) on mitochondrial biogenesis, morphology, and function including regulation of Nuclear Respiratory Factor-1 (NRF-1, NRF1) transcription. NRF-1 is a nuclear transcription factor that promotes transcription of mitochondrial transcription factor TFAM (mtDNA maintenance factorFA) which then regulates mtDNA-encoded genes. The nuclear effects of estrogens on gene expression directly controlling mitochondrial biogenesis, oxygen consumption, mtDNA transcription, and apoptosis are reviewed.

Peripubertal serum dioxin concentrations and subsequent sperm methylome profiles of young Russian adults

BACKGROUND

The association of exposure to endocrine disrupting chemicals in the peripubertal period with subsequent sperm DNA methylation is unknown.

OBJECTIVE

We examined the association of peripubertal serum 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) concentrations with whole-genome bisulfite sequencing (WGBS) of sperm collected in young adulthood.

METHODS

The Russian Children's Study is a prospective cohort of 516 boys who were enrolled at 8-9 years of age and provided semen samples at 18-19 years of age. WGBS of sperm was conducted to identify differentially methylated regions (DMR) between highest (n = 4) and lowest (n = 4) peripubertal TCDD groups.

RESULTS

We found 52 DMRs that distinguished lowest and highest peripubertal serum TCDD concentrations. One of the top scoring networks, "Cellular Assembly and Organization, Cellular Function and Maintenance, Carbohydrate Metabolism", identified estrogen receptor alpha as its central regulator.

CONCLUSION

Findings from our limited sample size suggest that peripubertal environmental exposures are associated with sperm DNA methylation in young adults.

Immunolocalization of G Protein-Coupled Estrogen Receptor in the Pig Epididymis

The presence of estrogen in the genital ducts of different mammalian species has been extensively studied and the estrogen influence on the functional activity of the male genital tract has been hypothesized. Conversely, very few data have been reported on pig excurrent ducts: the localization of classical estrogen receptors (ERα and ERβ) is scarcely known, while the expression of the G protein-coupled receptor (GPER1), a membrane estrogen receptor, is still unknown in pig. The aim of the present study was to evaluate GPER1 expression in the different regions of the mature pig epididymis, using immunohistochemistry, western blot and RT-PCR analyses. The results showed that GPER1 is mainly expressed in the epithelial cells of the corpus epididymis compared to the caput and the cauda, while muscle cells are moderately immunostained and stromal cells are unstained. The presence of GPER1 was confirmed by Western blot and RT-PCR analyses. In our study, we have demonstrated for the first time the GPER1 expression in male porcine epididymis, revealing a new mediator of estrogen signaling at this site. In conclusion, these new data suggest that estrogen action via GPER1 may contribute to sperm maturation in the corpus and sperm protection/storage in the cauda. Interestingly, the presence of GPER1 in the muscle layer may be indicative of a possible GPER1 involvement in the estrogen regulation of duct contractility. Anat Rec, 2018. © 2018 Wiley Periodicals, Inc.

Characterization of the human RFX transcription factor family by regulatory and target gene analysis

BACKGROUND

Evolutionarily conserved RFX transcription factors (TFs) regulate their target genes through a DNA sequence motif called the X-box. Thereby they regulate cellular specialization and terminal differentiation. Here, we provide a comprehensive analysis of all the eight human RFX genes (RFX1-8), their spatial and temporal expression profiles, potential upstream regulators and target genes.

RESULTS

We extracted all known human RFX1-8 gene expression profiles from the FANTOM5 database derived from transcription start site (TSS) activity as captured by Cap Analysis of Gene Expression (CAGE) technology. RFX genes are broadly (RFX1-3, RFX5, RFX7) and specifically (RFX4, RFX6) expressed in different cell types, with high expression in four organ systems: immune system, gastrointestinal tract, reproductive system and nervous system. Tissue type specific expression profiles link defined RFX family members with the target gene batteries they regulate. We experimentally confirmed novel TSS locations and characterized the previously undescribed RFX8 to be lowly expressed. RFX tissue and cell type specificity arises mainly from differences in TSS architecture. RFX transcript isoforms lacking a DNA binding domain (DBD) open up new possibilities for combinatorial target gene regulation. Our results favor a new grouping of the RFX family based on protein domain composition. We uncovered and experimentally confirmed the TFs SP2 and ESR1 as upstream regulators of specific RFX genes. Using TF binding profiles from the JASPAR database, we determined relevant patterns of X-box motif positioning with respect to gene TSS locations of human RFX target genes.

CONCLUSIONS

The wealth of data we provide will serve as the basis for precisely determining the roles RFX TFs play in human development and disease.

Atrazine affects the morphophysiology, tissue homeostasis and aromatase expression in the efferent ductules of adult rats with mild alterations in the ventral prostate

The widely used herbicide atrazine is a potent endocrine disruptor known to cause increased aromatase expression and transient increase in testicular weight followed by remarkable testis atrophy. However, whether the effects of atrazine on the testes are primary or secondary to dysfunctions in other components of male reproductive tract remains unknown. Given the high sensitivity of the efferent ductules to estrogen imbalance and the similarity to alterations previously described for other disruptors of these ductules function, and the testicular alterations observed after atrazine exposure, we hypothesized that the efferent ductules could be a target for atrazine. Herein we characterized the efferent ductules and the ventral prostate of adult Wistar rats treated with 200 mg/kg/day of atrazine for 7, 15, and 40 days. Additionally, we evaluated if the effects of atrazine in these organs could be reduced after discontinuation of the treatment. Atrazine exposure resulted in mild effects on the ventral prostate, but remarkable alterations on the efferent ductules, including luminal dilation, reduced epithelial height, and disruption of the epithelial homeostasis, which coincides with increased aromatase expression. Together with our previous data, these results suggest that at least part of the testicular effects of atrazine may be secondary to the alterations in the efferent ductules.

Xenoestrogen regulation of ERα/ERβ balance in hormone-associated cancers

The hormone 17β-estradiol (E2) contributes to body homeostasis maintenance by regulating many different physiological functions in both male and female organs. E2 actions in reproductive and non-reproductive tissues rely on a complex net of nuclear and extra-nuclear signal transduction pathways triggered by at least two estrogen receptor subtypes (ERα and ERβ). Consequently, the de-regulation of E2:ER signaling contributes to the pathogenesis of many diseases including cancer. Among other factors, the ERα/ERβ ratio is considered one of the pivotal mechanisms at the root of E2 action in cancer progression. Remarkably, several natural or synthetic exogenous chemicals, collectively called xenoestrogens, bind to ERs and interfere with their signals and intracellular functions. In this review, the molecular mechanism(s) through which xenoestrogens influence ERα and ERβ intracellular concentrations and the consequences of this influence on E2-related cancer will be discussed.

Expression of oestrogen receptors (GPER, ESR1, ESR2) in human ductuli efferentes and proximal epididymis

Oestrogen targeting in the human genital ducts is still not well-known. In fact, to date, the localization of oestrogen receptors, ESR1 and ESR2, is controversial and the presence of the membrane oestrogen receptor GPER (G protein-coupled oestrogen receptor) is unexplored. This study has investigated the expression of GPER, ESR1, ESR2 in human ductuli efferentes and proximal caput epididymis by immunohistochemistry and Western blot analysis. Furthermore, the presence of PELP1 (proline-glutamic acid-leucine-rich protein 1), a co-regulator of the oestrogen receptors, was also evaluated. In ductuli efferentes, GPER and ESR1 were clearly localized in all epithelial cells, while ESR2 was evidenced only in ciliated cells. Conversely, the epithelial cells of proximal caput epididymis revealed moderate GPER immunoreactivity, the absence of ERS1 and the occasional presence of ESR2. Furthermore, PELP1 was observed in ciliated cells of ductuli efferentes and in principal cells of proximal caput epididymis. Therefore, this study firstly demonstrated the expression of GPER in human male genital ducts, revealing a new mediator of oestrogen action in these anatomical sites. ESR1 and ESR2 were differentially localized in the two genital tracts together with PELP1, but cell sites of ERs and their co-regulator were not homogeneous. So, a different regional/cellular association of GPER with the classical oestrogen receptors was highlighted, suggesting that oestrogen action could be mediated by GPER, ESR1, ESR2 in ductuli efferentes, while by GPER and, occasionally by ESR2, in proximal caput epididymis. This study suggests that the specific oestrogen-mediated functions in human genital ducts might result from the different local interactions of oestrogens with oestrogen receptors and their co-regulators.

Genome-Wide Mapping of In Vivo ERα-Binding Sites in Male Mouse Efferent Ductules

As an important nuclear hormone receptor, estrogen receptor α (ERα), which is encoded by the Esr1 gene, regulates the expression of hundreds of genes in a stimulus-specific, temporal, and tissue-specific fashion, mainly by binding to specific DNA sequences called estrogen response elements (EREs). As an important estrogen target tissue in males, the function of the efferent ductules relies on the presence of the ERα protein, but the underlying regulatory mechanisms are poorly illustrated. In this study, genome-wide ERα-binding sites in mouse efferent ductules were mapped by chromatin immunoprecipitation sequencing. In total, 12,105 peaks were identified, and a majority of them were located far from the annotated gene transcription start site. Motif analysis revealed that ∼80% of the ERα-binding peaks harbored at least one ERE, whereas androgen response element-like sequences were the most overrepresented motif in the peaks without any EREs. A number of candidate transcription factor motifs adjacent to the EREs were significantly enriched, including AP2 and GRE, implying the involvement of these putative adjacent factors in the global regulation of ERα target genes. Unexpectedly, more than 50% of the ERα-binding peaks in mouse efferent ductules overlapped with those binding peaks previously identified in mouse uterus, suggesting the conserved mechanism of ERα action in these two tissues. Cobinding of ERα target genes by androgen receptor was further confirmed for Slc9a3 gene, which was responsible for fluid resorption in the efferent ductules. Taken together, our study provides a useful reference set for future work aimed at exploring the mechanism of ERα action in physiological conditions.