Estrogen receptor-alpha and beta are differentially distributed, expressed and activated in the fetal genital tubercle

A Genetics Study in the Foreskin of Boys with Hypospadias

Introduction

Hypospadias is a malformation of the genitourinary system in males, characterized by the placement of the urethral opening in the ventral surface of the penis. Although controversies continue about etiology, endocrine disrupting chemicals that disrupt normal endocrine signaling at the receptor or signal transduction level are thought to play an essential role in etiology. This study aimed to investigate the receptor gene expressions of the sex hormones and FGFR2, HOXA13, and TGFB1, which are considered to play an essential role in developing hypospadias.

Methods

The samples from the foreskin of 26 patients with hypospadias and 26 healthy children who underwent circumcision operations were collected. ESR1, AR, FGFR2, HOXA13, and TGFB gene expressions were investigated by real-time PCR in samples obtained during surgery.

Results

In the hypospadias group, ESR1 expression was increased (p = 0.013), and AR and FGFR2 expressions were decreased, which were found to be statistically significant (p = 0.027 and p = 0.003, respectively). There was no statistically significant difference between hypospadias and control groups in TGFBand HOXA13expression levels (p > 0.05).

Discussion

The results suggest that sex hormone receptors and FGFR2 may play an essential role in developing male external genital structures at the gene level. The defects in the expression of these genes can contribute to understanding the development of hypospadias.

Estrogens and development of the mouse and human external genitalia

The Jost hypothesis states that androgens are necessary for normal development of the male external genitalia. In this review, we explore the complementary hypothesis that estrogens can elicit abnormal development of male external genitalia. Herein, we review available data in both humans and mice on the deleterious effects of estrogen on external genitalia development, especially during the "window of susceptibility" to exogenous estrogens. The male and female developing external genitalia in both the human and mouse express ESR1 and ESR2, along with the androgen receptor (AR). Human clinical data suggests that exogenous estrogens can adversely affect normal penile and urethral development, resulting in hypospadias. Experimental mouse data also strongly supports the idea that exogenous estrogens cause penile and urethral defects. Despite key differences, estrogen-induced hypospadias in the mouse displays certain morphogenetic homologies to human hypospadias, including disruption of urethral fusion and preputial abnormalities. Timing of estrogenic exposure, or the "window of susceptibility," is an important consideration when examining malformations of the external genitalia in both humans and mice. In addition to a review of normal human and mouse external genital development, this article aims to review the present data on the role of estrogens in normal and abnormal development of the mouse and human internal and external genitalia. Based on the current literature for both species, we conclude that estrogen-dependent processes may play a role in abnormal genital development.

A critical role for estrogen signaling in penis development

Hypospadias, a developmental defect of the penis, is one of the most common congenital malformations in humans. Its incidence has rapidly increased over recent decades, and this has been largely attributed to our increased exposure to endocrine-disrupting chemicals. Penis development is primarily an androgen-driven process; however, estrogen and xenoestrogens are known to affect penis development in both humans and mice. Here, we investigated the role of estrogen in the developing penis. Using a novel penis culture system, we showed that exogenous estrogen directly targets the developing penis in utero to cause hypospadias. In addition, we also uncovered an unexpected endogenous role for estrogen in normal postnatal penis development and showed that a loss of estrogen signaling results in a mild hypospadias phenotype, the most common manifestation of this disease in humans. Our findings demonstrated that both androgen and estrogen signaling are intrinsically required for normal urethral closure. These findings confirmed that penis development is not an entirely androgen-driven process but one in which endogenous estrogen signaling also plays a critical role.-Govers, L. C., Phillips, T. R., Mattiske, D. M., Rashoo, N., Black, J. R., Sinclair, A., Baskin, L. S., Risbridger, G. P., Pask, A. J. A critical role for estrogen signaling in penis development.

Contrasting mechanisms of penile urethral formation in mouse and human

This paper addresses the developmental mechanisms of formation of the mouse and human penile urethra and the possibility that two disparate mechanisms are at play. It has been suggested that the entire penile urethra of the mouse forms via direct canalization of the endodermal urethral plate. While this mechanism surely accounts for development of the proximal portion of the mouse penile urethra, we suggest that the distal portion of the mouse penile urethra forms via a series of epithelial fusion events. Through review of the recent literature in combination with new data, it is unlikely that the entire mouse urethra is formed from the endodermal urethral plate due in part to the fact that from E14 onward the urethral plate is not present in the distal aspect of the genital tubercle. Formation of the distal portion of the mouse urethra receives substantial contribution from the preputial swellings that form the preputial-urethral groove and subsequently the preputial-urethral canal, the later of which is subdivided by a fusion event to form the distal portion of the mouse penile urethra. Examination of human penile development also reveals comparable dual morphogenetic mechanisms. However, in the case of human, direct canalization of the urethral plate occurs in the glans, while fusion events are involved in formation of the urethra within the penile shaft, a pattern exactly opposite to that of the mouse. The highest incidence of hypospadias in humans occurs at the junction of these two different developmental mechanisms. The relevance of the mouse as a model of human hypospadias is discussed.

Do endocrine disruptors cause hypospadias?

Introduction

Endocrine disruptors or environmental agents, disrupt the endocrine system, leading to various adverse effects in humans and animals. Although the phenomenon has been noted historically in the cases of diethylstilbestrol (DES) and dichlorodiphenyltrichloroethane (DDT), the term “endocrine disruptor” is relatively new. Endocrine disruptors can have a variety of hormonal activities such as estrogenicity or anti-androgenicity. The focus of this review concerns on the induction of hypospadias by exogenous estrogenic endocrine disruptors. This has been a particular clinical concern secondary to reported increased incidence of hypospadias. Herein, the recent literature is reviewed as to whether endocrine disruptors cause hypospadias.

Methods

A literature search was performed for studies involving both humans and animals. Studies within the past 5 years were reviewed and categorized into basic science, clinical science, epidemiologic, or review studies.

Results

Forty-three scientific articles were identified. Relevant sentinel articles were also reviewed. Additional pertinent studies were extracted from the reference of the articles that obtained from initial search results. Each article was reviewed and results presented. Overall, there were no studies which definitely stated that endocrine disruptors caused hypospadias. However, there were multiple studies which implicated endocrine disruptors as one component of a multifactorial model for hypospadias.

Conclusions

Endocrine disruption may be one of the many critical steps in aberrant development that manifests as hypospadias.

Genetic polymorphisms in ESR1 and ESR2 genes, and risk of hypospadias in a multiethnic study population

PURPOSE

Estrogenic endocrine disruptors acting via estrogen receptors α (ESR1) and β (ESR2) have been implicated in the etiology of hypospadias, a common congenital malformation of the male external genitalia. We determined the association of single nucleotide polymorphisms in ESR1 and ESR2 genes with hypospadias in a racially/ethnically diverse study population of California births.

MATERIALS AND METHODS

We investigated the relationship between hypospadias and 108 ESR1 and 36 ESR2 single nucleotide polymorphisms in 647 cases and 877 population based nonmalformed controls among infants born in selected California counties from 1990 to 2003. Subgroup analyses were performed by race/ethnicity (nonHispanic white and Hispanic subjects) and by hypospadias severity (mild to moderate and severe).

RESULTS

Odds ratios for 33 of the 108 ESR1 single nucleotide polymorphisms had p values less than 0.05 (p = 0.05 to 0.007) for risk of hypospadias. However, none of the 36 ESR2 single nucleotide polymorphisms was significantly associated. In stratified analyses the association results were consistent by disease severity but different sets of single nucleotide polymorphisms were significantly associated with hypospadias in nonHispanic white and Hispanic subjects. Due to high linkage disequilibrium across the single nucleotide polymorphisms, haplotype analyses were conducted and identified 6 haplotype blocks in ESR1 gene that had haplotypes significantly associated with an increased risk of hypospadias (OR 1.3 to 1.8, p = 0.04 to 0.00001). Similar to single nucleotide polymorphism analysis, different ESR1 haplotypes were associated with risk of hypospadias in nonHispanic white and Hispanic subjects. No significant haplotype association was observed for ESR2.

CONCLUSIONS

The data provide evidence that ESR1 single nucleotide polymorphisms and haplotypes influence the risk of hypospadias in white and Hispanic subjects, and warrant further examination in other study populations.

Specific morphogenetic events in mouse external genitalia sex differentiation are responsive/dependent upon androgens and/or estrogens

The objective of this study was to perform a comprehensive morphologic analysis of developing mouse external genitalia (ExG) and to determine specific sexual differentiation features that are responsive to androgens or estrogens. To eliminate sex steroid signaling postnatally, male and female mice were gonadectomized on the day of birth, and then injected intraperitoneally every other day with DES (200 ng/g), DHT (1 μg/g), or oil. On day-10 postnatal male and female ExG were dissected, fixed, embedded, serially sectioned and analyzed. We identified 10 sexually dimorphic anatomical features indicative of normal penile and clitoral differentiation in intact mice. Several (but not all) penile features were impaired or abolished as a result of neonatal castration. Those penile features remaining after neonatal castration were completely abolished with attendant clitoral development in androgen receptor (AR) mutant male mice (X(Tfm)/Y and X/Y AR-null) in which AR signaling is absent both pre- and postnatally. Administration of DHT to neonatally castrated males restored development of all 10 masculine features to almost normal levels. Neonatal ovariectomy of female mice had little effect on clitoral development, whereas treatment of ovariectomized female mice with DHT induced partial masculinization of the clitoris. Administration of DES to neonatally gonadectomized male and female mice elicited a spectrum of development abnormalities. These studies demonstrate that the presence or absence of androgen prenatally specifies penile versus clitoral identity. Differentiated penile features emerge postnatally and are sensitive to and dependent upon prenatal or pre- and postnatal androgen. Emergence of differentiated clitoral features occurs postnatally in either intact or ovariectomized females. It is likely that each penile and clitoral feature has a unique time-course of hormonal dependency/sensitivity.

Morphology of the external genitalia of the adult male and female mice as an endpoint of sex differentiation

Adult external genitalia (ExG) are the endpoints of normal sex differentiation. Detailed morphometric analysis and comparison of adult mouse ExG has revealed 10 homologous features distinguishing the penis and clitoris that define masculine vs. feminine sex differentiation. These features have enabled the construction of a simple metric to evaluate various intersex conditions in mutant or hormonally manipulated mice. This review focuses on the morphology of the adult mouse penis and clitoris through detailed analysis of histologic sections, scanning electron microscopy, and three-dimensional reconstruction. We also present previous results from evaluation of "non-traditional" mammals, such as the spotted hyena and wallaby to demonstrate the complex process of sex differentiation that involves not only androgen-dependent processes, but also estrogen-dependent and hormone-independent mechanisms.

Androgen receptor is overexpressed in boys with severe hypospadias, and ZEB1 regulates androgen receptor expression in human foreskin cells

INTRODUCTION

ZEB1 is overexpressed in patients with severe hypospadias. We examined the interaction between ZEB1 and the androgen receptor (AR) in vitro and the expression of AR in boys with hypospadias.

RESULTS

ZEB1 and AR colocalize to the nucleus. Estrogen upregulated ZEB1 and AR expression. Chromatin immunoprecipitation (ChIP) demonstrated that ZEB1 binds to an E-box sequence in the AR gene promoter. AR expression is higher in subjects with severe hypospadias than those with mild hypospadias and control subjects (P < 0.05). ZEB1 physically interacts with AR in human foreskin cells.

DISCUSSION

AR is overexpressed in patients with severe hypospadias. Environmental estrogenic compounds may increase the risk of hypospadias by facilitating the interaction between ZEB1 and AR.

METHODS

Hs68 cells, a fibroblast cell line derived from neonatal human foreskin, were exposed to 0, 10, and 100 nmol/l of estrogen, after which the cellular localization of ZEB1 and AR was assessed using immunocytochemistry. To determine if ZEB1 interacted with the AR gene, ChIP was performed using ZEB1 antibody and polymerase chain reaction (PCR) for AR. Second, AR expression was quantified using real-time PCR and western blot in normal subjects (n = 32), and subjects with mild (n = 16) and severe hypospadia (n = 16).

Expression of estrogen receptor alpha and beta is decreased in hypospadias

PURPOSE

Estrogenic endocrine disruptors acting via estrogen receptors α and β have been implicated in the etiology of hypospadias. However, the expression and distribution of estrogen receptors α and β in normal and hypospadiac human foreskins is unknown. We characterized the location and expression of estrogen receptors α and β in normal and hypospadiac foreskins.

MATERIALS AND METHODS

We prospectively collected excess foreskin from 35 patients undergoing hypospadias repair and 15 patients undergoing elective circumcision. Hypospadias was classified as severe in 18 patients and mild in 17 based on the ectopic position of the meatus. mRNA expression levels in estrogen receptors α and β were quantified using reverse transcriptase polymerase chain reaction. Receptor location was characterized by immunohistochemical analysis. Additionally immunohistochemical analysis was performed in 4 archived human fetal penises.

RESULTS

Mean ± SD ages were similar for the circumcision (9.5±3 months) and hypospadias repair groups (9±3 months, p=0.75). mRNA expression levels in estrogen receptors α and β were significantly decreased in hypospadiac foreskin cases compared to controls (p<0.001), while no statistically significant differences were seen between foreskins with severe and mild hypospadias. Estrogen receptor β immunostaining was strong in normal foreskin but weak in hypospadiac foreskin. Estrogen receptor β immunoreactivity was most intense in the stratum basale and stratum spinosum. Estrogen receptor α immunostaining was weak in normal and mild hypospadias foreskin, and undetectable in severe hypospadias. Fetal penises expressed strong estrogen receptor β immunopositivity in the urethral plate epithelium, corpus spongiosum, corpora cavernosa and penile skin, while estrogen receptor α immunostaining was not detected.

CONCLUSIONS

These data demonstrate a difference in estrogen receptor α and β expression and location in the foreskin of patients with hypospadias compared to controls. These findings are consistent with aberrant estrogenic effects having a role in the etiology of hypospadias.

Molecular mechanisms of induction of persistent changes by estrogenic chemicals on female reproductive tracts and external genitalia

The effects of environmental endocrine-disrupting chemicals (EDCs) are a great and growing concern for human and animal development and life. The reproductive organs are considered as a primary target of EDCs, yet the effects on reproductive organs can extend to other body systems. Perinatal diethylstilbestrol (DES)-exposed mice exhibit various reproductive organ abnormalities. The perinatal DES-exposure model has allowed insight into our understanding of the mechanisms of persistent reproductive organ abnormalities elicited by exposure to estrogens and/or estrogenic EDCs. The persistent changes in the vagina of neonatally DES-exposed mice result from sustained expression of growth factors by ligand-independent transcriptional activation of the estrogen receptor. Developmental regulatory genes, such as Wnt and Hox genes, are also targets of DES during fetal stages and altered gene expression can induce malformations of the reproductive organs. In this review, we focus on the development of female reproductive tracts and external genitalia, and discuss the recent progress in understanding the disruptive effects of estrogens and EDCs on these organs.

Hypospadias: interactions between environment and genetics

Hypospadias is one of the most common congenital malformations. It is considered to be a mild form of the 46,XY disorders of sex development (DSD), but its precise etiology remains to be elucidated. Compromised androgen synthesis or effects can cause this frequent malformation, although the mutational analyses of the genes involved in androgen actions have identified abnormalities in only a very small portion of patients. The overwhelming majority of cases remain unexplained and hypospadias may be a highly heterogeneous condition subject to multiple genetic and environmental factors. We here review the recent advances in this field and discuss the potential interactions between the environment and genetics.

Altered expression and localization of estrogen receptors alpha and beta in the testes of a cryptorchid rat model

OBJECTIVES

To assess the involvement of estrogen in spermatogenesis, we evaluated the expression of estrogen receptors (ERs) alpha (ERalpha) and beta (ERbeta) in the cryptorchid testes in model rats exposed to flutamide during the fetal stage.

METHODS

Cryptorchid model rats were produced by administering flutamide to pregnant Sprague-Dawley rats. To evaluate the sequential change in the expression of ERalpha and ERbeta genes, real-time reverse transcriptase-polymerase chain reaction (RT-PCR) was performed using specific primers. Immunohistochemistry with ERalpha and ERbeta antibodies was performed, and the results were evaluated to determine the influences of orchiopexy.

RESULTS

Real-time RT-PCR revealed that ERalpha expression in control testes increases with growth and peaks value at 7 weeks and significantly decreases in cryptorchid testes. ERbeta expression was low, and there were no significant differences between both the cryptorchid and control testes groups. Immunohistochemistry revealed that ERalpha protein was present in the spermatids and Sertoli cells of descended testes, and that this protein was strongly expressed in the Leydig cells of cryptorchid testes. ERbeta was detected in multiple cells in both groups. After orchiopexy, ERalpha expression was detected in the spermatids of cryptorchid testes.

CONCLUSIONS

Spermatogenesis in cryptorchid rats is disrupted. Because the expression of ERbeta was unchanged in both control and cryptorchid testes, we supposed that alteration in ERalpha levels is more closely related to spermatogenic failure than ERbeta levels in the cryptorchid testes. We considered that increased expression of ERalpha in Leydig cells of cryptorchid testes is associated with estradiol level in the testicular tissue, and androgen-estrogen imbalance deteriorates spermatogenesis in cryptorchidism.

A comparison of the effects of three GM corn varieties on mammalian health

We present for the first time a comparative analysis of blood and organ system data from trials with rats fed three main commercialized genetically modified (GM) maize (NK 603, MON 810, MON 863), which are present in food and feed in the world. NK 603 has been modified to be tolerant to the broad spectrum herbicide Roundup and thus contains residues of this formulation. MON 810 and MON 863 are engineered to synthesize two different Bt toxins used as insecticides. Approximately 60 different biochemical parameters were classified per organ and measured in serum and urine after 5 and 14 weeks of feeding. GM maize-fed rats were compared first to their respective isogenic or parental non-GM equivalent control groups. This was followed by comparison to six reference groups, which had consumed various other non-GM maize varieties. We applied nonparametric methods, including multiple pairwise comparisons with a False Discovery Rate approach. Principal Component Analysis allowed the investigation of scattering of different factors (sex, weeks of feeding, diet, dose and group). Our analysis clearly reveals for the 3 GMOs new side effects linked with GM maize consumption, which were sex- and often dose-dependent. Effects were mostly associated with the kidney and liver, the dietary detoxifying organs, although different between the 3 GMOs. Other effects were also noticed in the heart, adrenal glands, spleen and haematopoietic system. We conclude that these data highlight signs of hepatorenal toxicity, possibly due to the new pesticides specific to each GM corn. In addition, unintended direct or indirect metabolic consequences of the genetic modification cannot be excluded.

Steroid receptor expression in the developing copulatory system of the green anole lizard (Anolis carolinensis)

In adulthood, the copulatory system in male green anole lizards is characterized by the presence of two hemipenes, each controlled by ipsilateral muscles. These structures are present in both sexes early in development, but prior to hatching regress completely in females. Embryonic treatment with steroid hormones alters the morphology of the copulatory system, suggesting active roles for both androgens and estrogens in sexual differentiation. To elucidate the timing and sites of steroid hormone action in the embryonic copulatory system, the distributions of androgen receptor (AR) and estrogen receptor-alpha (ER alpha) mRNA expression were examined. In situ hybridization was conducted on the rostral tail of anoles at three stages spanning differentiation of the copulatory structures: embryonic days (E) 13, 18, and 24 (hatching occurs at approximately E34). At E13, males expressed significantly higher levels of AR mRNA in both hemipenes and muscles than did females, while females at the same age tended to express higher levels of ER alpha mRNA in these structures. By E18, hemipenes and copulatory muscles were regressed in most females, and were not present in any females at E24. In males, no effect of age was detected on the expression of either AR or ER alpha. These data suggest that peripheral copulatory structures in the embryonic anole are direct targets for the actions of both androgens and estrogens in sexual differentiation, consistent with the idea that estradiol facilitates regression in females and androgen promotes survival in males. However, the issue of whether or not a critical period exists remains open.