A frame-shift mutation in the androgen receptor gene causes complete androgen insensitivity in the testicular-feminized mouse

Gene Duplication of Androgen Receptor As An Evolutionary Driving Force Underlying the Diversity of Sexual Characteristics in Teleost Fishes

Sexual dimorphism allows species to meet their fitness optima based on the physiological availability of each sex. Although intralocus sexual conflict appears to be a genetic constraint for the evolution of sex-specific traits, sex-linked genes and the regulation of sex steroid hormones contribute to resolving this conflict by allowing sex-specific developments. Androgens and their receptor, androgen receptor (Ar), regulate male-biased phenotypes. In teleost fish, ar ohnologs have emerged as a result of teleost-specific whole genome duplication (TSGD). Recent studies have highlighted the evolutionary differentiation of ar ohnologs responsible for the development of sexual characteristics, which sheds light on the need for comparative studies on androgen regulation among different species. In this review, we discuss the importance of ar signaling as a regulator of male-specific traits in teleost species because teleost species are suitable experimental models for comparative studies owing to their great diversity in male-biased morphological and physiological traits. To date, both in vivo and in vitro studies on teleost ar ohnologs have shown a substantial influence of ars as a regulator of male-specific reproductive traits such as fin elongation, courtship behavior, and nuptial coloration. In addition to these sexual characteristics, ar substantially influences immunity, inducing a sex-biased immune response. This review aims to provide a comprehensive understanding of the current state of teleost ar studies and emphasizes the potential of teleost fishes, given their availability, to find molecular evidence about what gives rise to the spectacular diversity among fish species.

Guidelines on the use of sex and gender in cardiovascular research

In cardiovascular research, sex and gender have not typically been considered in research design and reporting until recently. This has resulted in clinical research findings from which not only all women, but also gender-diverse individuals have been excluded. The resulting dearth of data has led to a lack of sex- and gender-specific clinical guidelines and raises serious questions about evidence-based care. Basic research has also excluded considerations of sex. Including sex and/or gender as research variables not only has the potential to improve the health of society overall now, but it also provides a foundation of knowledge on which to build future advances. The goal of this guidelines article is to provide advice on best practices to include sex and gender considerations in study design, as well as data collection, analysis, and interpretation to optimally establish rigor and reproducibility needed to inform clinical decision-making and improve outcomes. In cardiovascular physiology, incorporating sex and gender is a necessary component when optimally designing and executing research plans. The guidelines serve as the first guidance on how to include sex and gender in cardiovascular research. We provide here a beginning path toward achieving this goal and improve the ability of the research community to interpret results through a sex and gender lens to enable comparison across studies and laboratories, resulting in better health for all.

Androgen action on myogenesis throughout the lifespan; comparison with neurogenesis

Androgens' pleiotropic actions in promoting sex differences present not only a challenge to providing a comprehensive account of their function, but also an opportunity to gain insights by comparing androgenic actions across organ systems. Although often overlooked by neuroscientists, skeletal muscle is another androgen-responsive organ system which shares with the nervous system properties of electrochemical excitability, behavioral relevance, and remarkable capacity for adaptive plasticity. Here we review androgenic regulation of mitogenic plasticity in skeletal muscle with the goal of identifying areas of interest to those researching androgenic mechanisms mediating sexual differentiation of neurogenesis. We use an organizational-activational framework to relate broad areas of similarity and difference between androgen effects on mitogenesis in muscle and brain throughout the lifespan, from early organogenesis, through pubertal organization, adult activation, and aging. The focus of the review is androgenic regulation of muscle-specific stem cells (satellite cells), which share with neural stem cells essential functions in development, plasticity, and repair, albeit with distinct, muscle-specific features. Also considered are areas of paracrine and endocrine interaction between androgen action on muscle and nervous system, including mediation of neural plasticity of innervating and distal neural populations by muscle-produced trophic factors.

Androgen receptor signaling protects male mice from the development of immune response to peanut

OBJECTIVES

Peanut (PN) allergy is a major public health concern. Recent research has brought clarity about how individuals become sensitized to PN allergen with routes known through the skin, as well as the airway. Still unclear, however, is the role of sex hormones on the development of allergic immune responses to PN. This study examines the role of androgen receptor (AR) signaling in regulating PN-specific immune responses.

METHODS

We utilized a 4-week inhalation mouse model of PN allergy that is known to drive the production of PN-specific antibodies and elicit systemic anaphylaxis following PN challenge. Wildtype (WT) male, female, and androgen receptor-deficient testicular feminization mutant (ARTfm) male mice were examined using this model to document sex differences in PN allergy. To determine if sex differences also existed in the cellular immune response, this study utilized a 3-day inhalation mouse model of PN to examine the response of group 2 innate lymphoid cells (ILC2s). WT male and female mice were examined using this model to document sex differences in ILC2 response within the lungs.

RESULTS

AR use is critical in regulating PN-specific antibody levels. We found that ARTfm males have a higher antibody response and significantly worse anaphylactic response following PN challenge relative to WT males. WT males also exhibit a less severe anaphylactic response compared to ARTfm male and female mice. Lastly, we discovered that lung ILC2s from female mice respond more robustly to PN compared to ILC2s within WT male mice.

CONCLUSIONS

Taken together, this study suggests that male sex hormones, namely androgens, negatively regulate allergic immune responses to PN.

The role of androgens and estrogens in social interactions and social cognition

Gonadal hormones are becoming increasingly recognized for their effects on cognition. Estrogens, in particular, have received attention for their effects on learning and memory that rely upon the functioning of various brain regions. However, the impacts of androgens on cognition are relatively under investigated. Testosterone, as well as estrogens, have been shown to play a role in the modulation of different aspects of social cognition. This review explores the impact of testosterone and other androgens on various facets of social cognition including social recognition, social learning, social approach/avoidance, and aggression. We highlight the relevance of considering not only the actions of the most commonly studied steroids (i.e., testosterone, 17β-estradiol, and dihydrotestosterone), but also that of their metabolites and precursors, which interact with a plethora of different receptors and signalling molecules, ultimately modulating behaviour. We point out that it is also essential to investigate the effects of androgens, their precursors and metabolites in females, as prior studies have mostly focused on males. Overall, a comprehensive analysis of the impact of steroids such as androgens on behaviour is fundamental for a full understanding of the neural mechanisms underlying social cognition, including that of humans.

Sex chromosome complement and sex steroid signaling underlie sex differences in immunity to respiratory virus infection

Epidemiological studies have revealed sex differences in the incidence and morbidity of respiratory virus infection in the human population, and often these observations are correlated with sex differences in the quality or magnitude of the immune response. Sex differences in immunity and morbidity also are observed in animal models of respiratory virus infection, suggesting differential dominance of specific immune mechanisms. Emerging research shows intrinsic sex differences in immune cell transcriptomes, epigenomes, and proteomes that may regulate human immunity when challenged by viral infection. Here, we highlight recent research into the role(s) of sex steroids and X chromosome complement in immune cells and describe how these findings provide insight into immunity during respiratory virus infection. We focus on the regulation of innate and adaptive immune cells by receptors for androgen and estrogens, as well as genes with a propensity to escape X chromosome inactivation. A deeper mechanistic knowledge of these pathways will help us to understand the often significant sex differences in immunity to endemic or pandemic respiratory pathogens such as influenza viruses, respiratory syncytial viruses and pathogenic coronaviruses.

Prostate organogenesis

Prostate organogenesis begins during embryonic development and continues through puberty when the prostate becomes an important exocrine gland of the male reproductive system. The specification and growth of the prostate is regulated by androgens and is largely a result of cell-cell communication between the epithelium and mesenchyme. The fields of developmental and cancer biology have long been interested in prostate organogenesis because of its relevance for understanding prostate diseases, and research has expanded in recent years with the advent of novel technologies, including genetic-lineage tracing, single-cell RNA sequencing and organoid culture methods, that have provided important insights into androgen regulation, epithelial cell origins and cellular heterogeneity. We discuss these findings, putting them into context with what is currently known about prostate organogenesis.

Ex vivo development of the entire mouse fetal reproductive tract by using microdissection and membrane-based organ culture techniques

Ex vivo explant culture is an appealing alternative to in vivo studies on fetal reproductive organ development. There is extensive literature on ex vivo methods of growing the fetal gonad. However, a method for culturing the whole fetal reproductive tract that has a different shape and size has not been documented. Here, with careful dissection and proper tissue orientation, we successfully cultured the entire bicornuate reproductive tracts from mouse embryos of both sexes on the Transwell insert membrane. The cultured reproductive tract system undergoes sexually dimorphic establishment and region-specific morphogenesis comparable to in vivo development of their counterparts. To test this culture method's applications, we used chemical treatment (dihydrotestosterone and BMS 564929) and genetic cellular ablation mouse model (Gli1-CreER; Rosa-DTA) to investigate the roles of androgen signaling and Gli1⁺ mesenchyme in Wolffian duct development. Dihydrotestosterone and BMS 564929 promoted the ectopic maintenance of Wolffian ducts in cultured XX tissues. The efficient and specific elimination of Gli1⁺ mesenchyme was successfully achieved in the cultured tissues, resulting in defective coiling of Wolffian ducts. These results demonstrate the amenability of this organ culture method for chemical and genetic manipulations that are otherwise difficult to study in vivo. Taken together, the establishment of this organ culture method provides a valuable tool complementary to in vivo studies for understanding fetal reproductive tract development in mice.

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.

The contradictory role of androgens in cutaneous and major burn wound healing

Wound healing is a complex process involving four overlapping phases: haemostasis, inflammation, cell recruitment and matrix remodeling. In mouse models, surgical, pharmacological and genetic approaches targeting androgen actions in skin have shown that androgens increase interleukin-6 and tumor necrosis factor-α production and reduce wound re-epithelization and matrix deposition, retarding cutaneous wound healing. Similarly, clinical studies have shown that cutaneous wound healing is slower in men compared to women. However, in major burn injury, which triggers not only local wound-healing processes but also systemic hypermetabolism, the role of androgens is poorly understood. Recent studies have claimed that a synthetic androgen, oxandrolone, increases protein synthesis, improves lean body mass and shortens length of hospital stay. However, the possible mechanisms by which oxandrolone regulates major burn injury have not been reported. In this review, we summarize the current findings on the roles of androgens in cutaneous and major burn wound healing, as well as androgens as a potential therapeutic treatment option for patients with major burn injuries.

A tale of two tracts: history, current advances, and future directions of research on sexual differentiation of reproductive tracts†

Alfred Jost's work in the 1940s laid the foundation of the current paradigm of sexual differentiation of reproductive tracts, which contends that testicular hormones drive the male patterning of reproductive tract system whereas the female phenotype arises by default. Once established, the sex-specific reproductive tracts undergo morphogenesis, giving rise to anatomically and functionally distinct tubular organs along the rostral-caudal axis. Impairment of sexual differentiation of reproductive tracts by genetic alteration and environmental exposure are the main causes of disorders of sex development, and infertility at adulthood. This review covers past and present work on sexual differentiation and morphogenesis of reproductive tracts, associated human disorders, and emerging technologies that have made impacts or could radically expand our knowledge in this field.

Prostate Organogenesis

The prostate is a male exocrine gland that secretes components of the seminal fluid. In men, prostate tumors are one of the most prevalent cancers. Studies on the development of the prostate have given a better understanding of the processes and genes that are important in the formation of this organ and have provided insights into the mechanisms of prostate tumorigenesis. These developmental studies have provided evidence that some of the genes and signaling pathways involved in development are reactivated or deregulated during prostate cancer. The prostate goes through a number of different stages during organogenesis, which include organ specification, epithelial budding, branching morphogenesis, canalization, and cytodifferentiation. During development, these processes are tightly regulated, many of which are controlled by the male hormone androgens. The majority of prostate tumors remain hormone regulated, and antiandrogen therapy is a first-line therapy, highlighting the important link between prostate organogenesis and cancer. In this review, we describe some of the data on genes that have important roles during prostate development that also have strong evidence linking them to prostate cancer.

The role of androgen receptors in atherosclerosis

Male disadvantage in cardiovascular health is well recognised. However, the influence of androgens on atherosclerosis, one of the major causes of many life-threatening cardiovascular events, is not well understood. With the dramatic increase in clinical prescription of testosterone in the past decade, concerns about the cardiovascular side-effects of androgen supplementation or androgen deprivation therapy are increasing. Potential atheroprotective effects of testosterone could be secondary to (aromatase-mediated) conversion into oestradiol or, alternatively, to direct activation of androgen receptors (AR). Recent development of animal models with cell-specific AR knockout has indicated a complex role for androgen action in atherosclerosis. Most studies suggest androgens are atheroprotective but the precise role of AR remains unclear. Increased use of AR knockout models should clarify the role of AR in atherogenesis and, thus, lead to exploitation of this pathway as a therapeutic target.

Role of the androgen receptor in the central nervous system

The involvement of gonadal androgens in functions of the central nervous system was suggested for the first time about half a century ago. Since then, the number of functions attributed to androgens has steadily increased, ranging from regulation of the hypothalamic-pituitary-gonadal axis and reproductive behaviors to modulation of cognition, anxiety and other non-reproductive functions. This review focuses on the implication of the neural androgen receptor in these androgen-sensitive functions and behaviors.

Polymorphisms in sex steroid receptors: From gene sequence to behavior

Sex steroid receptors have received much interest as potential mediators of human behaviors and mental disorders. Candidate gene association studies have identified about 50 genetic variants of androgen and estrogen receptors that correlate with human behavioral phenotypes. Because most of these polymorphisms lie outside coding regions, discerning their effect on receptor function is not straightforward. Thus, although discoveries of associations improve our ability to predict risk, they have not greatly advanced our understanding of underlying mechanisms. This article is intended to serve as a starting point for psychologists and other behavioral biologists to consider potential mechanisms. Here, I review associations between polymorphisms in sex steroid receptors and human behavioral phenotypes. I then consider ways in which genetic variation can affect processes such as mRNA transcription, splicing, and stability. Finally, I suggest ways that hypotheses about mechanism can be tested, for example using in vitro assays and/or animal models.

TFOS DEWS II Sex, Gender, and Hormones Report

One of the most compelling features of dry eye disease (DED) is that it occurs more frequently in women than men. In fact, the female sex is a significant risk factor for the development of DED. This sex-related difference in DED prevalence is attributed in large part to the effects of sex steroids (e.g. androgens, estrogens), hypothalamic-pituitary hormones, glucocorticoids, insulin, insulin-like growth factor 1 and thyroid hormones, as well as to the sex chromosome complement, sex-specific autosomal factors and epigenetics (e.g. microRNAs). In addition to sex, gender also appears to be a risk factor for DED. "Gender" and "sex" are words that are often used interchangeably, but they have distinct meanings. "Gender" refers to a person's self-representation as a man or woman, whereas "sex" distinguishes males and females based on their biological characteristics. Both gender and sex affect DED risk, presentation of the disease, immune responses, pain, care-seeking behaviors, service utilization, and myriad other facets of eye health. Overall, sex, gender and hormones play a major role in the regulation of ocular surface and adnexal tissues, and in the difference in DED prevalence between women and men. The purpose of this Subcommittee report is to review and critique the nature of this role, as well as to recommend areas for future research to advance our understanding of the interrelationships between sex, gender, hormones and DED.

Testosterone differentially regulates targets of lipid and glucose metabolism in liver, muscle and adipose tissues of the testicular feminised mouse

Testosterone deficiency is commonly associated with obesity, metabolic syndrome, type 2 diabetes and their clinical consequences-hepatic steatosis and atherosclerosis. The testicular feminised mouse (non-functional androgen receptor and low testosterone) develops fatty liver and aortic lipid streaks on a high-fat diet, whereas androgen-replete XY littermate controls do not. Testosterone treatment ameliorates these effects, although the underlying mechanisms remain unknown. We compared the influence of testosterone on the expression of regulatory targets of glucose, cholesterol and lipid metabolism in muscle, liver, abdominal subcutaneous and visceral adipose tissue. Testicular feminised mice displayed significantly reduced GLUT4 in muscle and glycolytic enzymes in muscle, liver and abdominal subcutaneous but not visceral adipose tissue. Lipoprotein lipase required for fatty acid uptake was only reduced in subcutaneous adipose tissue; enzymes of fatty acid synthesis were increased in liver and subcutaneous tissue. Stearoyl-CoA desaturase-1 that catalyses oleic acid synthesis and is associated with insulin resistance was increased in visceral adipose tissue and cholesterol efflux components (ABCA1, apoE) were decreased in subcutaneous and liver tissue. Master regulator nuclear receptors involved in metabolism-Liver X receptor expression was suppressed in all tissues except visceral adipose tissue, whereas PPARγ was lower in abdominal subcutaneous and visceral adipose tissue and PPARα only in abdominal subcutaneous. Testosterone treatment improved the expression (androgen receptor independent) of some targets but not all. These exploratory data suggest that androgen deficiency may reduce the buffering capability for glucose uptake and utilisation in abdominal subcutaneous and muscle and fatty acids in abdominal subcutaneous. This would lead to an overspill and uptake of excess glucose and triglycerides into visceral adipose tissue, liver and arterial walls.

Non-Cell-Autonomous Regulation of Retrograde Motoneuronal Axonal Transport in an SBMA Mouse Model

Defects in axonal transport are seen in motoneuronal diseases, but how that impairment comes about is not well understood. In spinal bulbar muscular atrophy (SBMA), a disorder linked to a CAG/polyglutamine repeat expansion in the androgen receptor (AR) gene, the disease-causing AR disrupts axonal transport by acting in both a cell-autonomous fashion in the motoneurons themselves, and in a non-cell-autonomous fashion in muscle. The non-cell-autonomous mechanism is suggested by data from a unique “myogenic” transgenic (TG) mouse model in which an AR transgene expressed exclusively in skeletal muscle fibers triggers an androgen-dependent SBMA phenotype, including defects in retrograde transport. However, motoneurons in this TG model retain the endogenous AR gene, leaving open the possibility that impairments in transport in this model also depend on ARs in the motoneurons themselves. To test whether non-cell-autonomous mechanisms alone can perturb retrograde transport, we generated male TG mice in which the endogenous AR allele has the testicular feminization mutation (Tfm) and, consequently, is nonfunctional. Males carrying the Tfm allele alone show no deficits in motor function or axonal transport, with or without testosterone treatment. However, when Tfm males carrying the myogenic transgene (Tfm/TG) are treated with testosterone, they develop impaired motor function and defects in retrograde transport, having fewer retrogradely labeled motoneurons and deficits in endosomal flux based on time-lapse video microscopy of living axons. These findings demonstrate that non-cell-autonomous disease mechanisms originating in muscle are sufficient to induce defects in retrograde transport in motoneurons.

Non-neural androgen receptor promotes androphilic odor preference in mice

In mice, male-typical preference for female olfactory cues results largely from sexually differentiated testosterone production. It is currently unclear on which cells and tissues testosterone acts to produce male-typical preference for female olfactory cues. To further address the site of androgen action on olfactory preference, we have developed a loxP-based transgenic mouse that overexpresses androgen receptors (AR) only when activated by Cre. We used this transgene to overexpress AR globally in all tissues using a CMV-Cre driver and a Nestin-Cre driver to overexpress AR selectively in neural tissue. We then examined olfactory preference in transgenic and wildtype (Wt) littermates by simultaneously exposing animals to female-soiled, male-soiled and clean bedding. Ubiquitous overexpression of AR in CMV-AR mice increased preference for male bedding, whereas neural-specific AR overexpression in Nestin-AR transgenic mice did not differ from wildtype siblings in olfactory preference. Neural activation of olfactory brain areas in response to female-soiled bedding was also evaluated in these mice by measuring FOS immunoreactivity. This revealed a decrease in neural activity along the accessory olfactory pathway that accompanied the decrease in preference for female odors in CMV-AR males, compared to both Nestin-AR and Wt male siblings. Together, results indicate that androgens act via non-neural AR to mediate olfactory preference and neural responses to olfactory stimuli, and further suggest that AR in non-neural tissues can promote androphilic odor preferences in male mice.In mice, male-typical preference for female olfactory cues results largely from sexually differentiated testosterone production. It is currently unclear on which cells and tissues testosterone acts to produce male-typical preference for female olfactory cues. To further address the site of androgen action on olfactory preference, we have developed a loxP-based transgenic mouse that overexpresses androgen receptors (AR) only when activated by Cre. We used this transgene to overexpress AR globally in all tissues using a CMV-Cre driver and a Nestin-Cre driver to overexpress AR selectively in neural tissue. We then examined olfactory preference in transgenic and wildtype (Wt) littermates by simultaneously exposing animals to female-soiled, male-soiled and clean bedding. Ubiquitous overexpression of AR in CMV-AR mice increased preference for male bedding, whereas neural-specific AR overexpression in Nestin-AR transgenic mice did not differ from wildtype siblings in olfactory preference. Neural activation of olfactory brain areas in response to female-soiled bedding was also evaluated in these mice by measuring FOS immunoreactivity. This revealed a decrease in neural activity along the accessory olfactory pathway that accompanied the decrease in preference for female odors in CMV-AR males, compared to both Nestin-AR and Wt male siblings. Together, results indicate that androgens act via non-neural AR to mediate olfactory preference and neural responses to olfactory stimuli, and further suggest that AR in non-neural tissues can promote androphilic odor preferences in male mice.

Environmental endocrine disruptors: Effects on the human male reproductive system

Incidences of altered development and neoplasia of male reproductive organs have increased during the last 50 years, as shown by epidemiological data. These data are associated with the increased presence of environmental chemicals, specifically "endocrine disruptors," that interfere with normal hormonal action. Much research has gone into testing the effects of specific endocrine disrupting chemicals (EDCs) on the development of male reproductive organs and endocrine-related cancers in both in vitro and in vivo models. Efforts have been made to bridge the accruing laboratory findings with the epidemiological data to draw conclusions regarding the relationship between EDCs, altered development and carcinogenesis. The ability of EDCs to predispose target fetal and adult tissues to neoplastic transformation is best explained under the framework of the tissue organization field theory of carcinogenesis (TOFT), which posits that carcinogenesis is development gone awry. Here, we focus on the available evidence, from both empirical and epidemiological studies, regarding the effects of EDCs on male reproductive development and carcinogenesis of endocrine target tissues. We also critique current research methodology utilized in the investigation of EDCs effects and outline what could possibly be done to address these obstacles moving forward.

Testosterone suppresses the expression of regulatory enzymes of fatty acid synthesis and protects against hepatic steatosis in cholesterol-fed androgen deficient mice

AIMS

Non-alcoholic fatty liver disease and its precursor hepatic steatosis is common in obesity and type-2 diabetes and is associated with cardiovascular disease (CVD). Men with type-2 diabetes and/or CVD have a high prevalence of testosterone deficiency. Testosterone replacement improves key cardiovascular risk factors. The effects of testosterone on hepatic steatosis are not fully understood.

MAIN METHODS

Testicular feminised (Tfm) mice, which have a non-functional androgen receptor (AR) and very low serum testosterone levels, were used to investigate testosterone effects on high-cholesterol diet-induced hepatic steatosis.

KEY FINDINGS

Hepatic lipid deposition was increased in Tfm mice and orchidectomised wild-type littermates versus intact wild-type littermate controls with normal androgen physiology. Lipid deposition was reduced in Tfm mice receiving testosterone treatment compared to placebo. Oestrogen receptor blockade significantly, but only partially, reduced the beneficial effects of testosterone treatment on hepatic lipid accumulation. Expression of key regulatory enzymes of fatty acid synthesis, acetyl-CoA carboxylase alpha (ACACA) and fatty acid synthase (FASN) were elevated in placebo-treated Tfm mice versus placebo-treated littermates and Tfm mice receiving testosterone treatment. Tfm mice on normal diet had increased lipid accumulation compared to littermates but significantly less than cholesterol-fed Tfm mice and demonstrated increased gene expression of hormone sensitive lipase, stearyl-CoA desaturase-1 and peroxisome proliferator-activated receptor-gamma but FASN and ACACA were not altered.

SIGNIFICANCE

An action of testosterone on hepatic lipid deposition which is independent of the classic AR is implicated. Testosterone may act in part via an effect on the key regulatory lipogenic enzymes to protect against hepatic steatosis.

Genetic background determines if Stat5b suppresses or enhances murine hepatocarcinogenesis

Murine hepatocarcinogenesis requires growth hormone (GH). To determine if the GH-responsive transcription factor STAT5b (signal transducer and activator of transcription 5b) is also required, we compared the hepatic gene expression profiles of global Stat5b null mice to cancer-resistant mice mutant in the GH pathway-GH-deficient little and androgen receptor-null Tfm males. We found a high degree of overlap among Tfm, little, and Stat5b null males. The liver cancer susceptibility of global Stat5b null mice was assessed on three distinct genetic backgrounds: BALB/cJ (BALB), C57BL/6J (B6), and C3H/HeJ (C3H). The effect of Stat5b on hepatocarcinogenesis depended on the genetic background. B6 Stat5b null congenic males and females developed 2.4 times as many tumors as wild-type (WT) controls (P < 0.002) and the tumors were larger (P < 0.003). In BALB/c congenics, loss of STAT5b had no effect on either sex. C3H Stat5b null congenic males and females were resistant to liver cancer, developing 2.7- and 6-fold fewer tumors, respectively (P < 0.02, 0.01). These results provide the first example of a single gene behaving as both oncogene and tumor suppressor in a given tissue, depending only on the endogenous modifier alleles carried by different genetic backgrounds.

Sex hormones and the dry eye

The greater prevalence of dry eye in women compared to men suggests that sex hormones may have a role in this condition. This review aims to present evidence for how sex hormones may affect the ocular structures involved in the production, regulation and maintenance of the normal tear film. It is hypothesised that hormone changes alter the homeostasis of the ocular surface and contribute to dry eye. Androgens impact on the structure and function of the meibomian and lacrimal glands and therefore androgen deficiency is, at least in part, associated with the aetiology of dry eye. In contrast, reports of the effects of oestrogen and progesterone on these ocular structures and on the conjunctiva are contradictory and the mechanisms of action of these female-specific sex hormones in the eye are not well understood. The uncertainty of the effects of oestrogen and progesterone on dry eye symptoms is reflected in the controversial relationship between hormone replacement therapy and the signs and symptoms of dry eye. Current understanding of sex hormone influences on the immune system suggests that oestrogen may modulate a cascade of inflammatory events, which underlie dry eye.

Androgen insensitive male rats display increased anxiety-like behavior on the elevated plus maze

Male rats carrying the testicular feminization mutation (Tfm-affected males) are insensitive to androgens, resulting in a female-typical peripheral phenotype despite possession of inguinal testes that are androgen secretory. Androgen-dependent neural and behavioral processes may likewise show atypical sexual differentiation. Interestingly, these mutant rats display elevated serum corticosterone, suggesting a chronic anxiety phenotype and dysregulated hypothalamic-pituitary-adrenal axis. In order to understand if elevated anxiety-like behavior is a possible mediating variable affecting the display of certain androgen-dependent behaviors, we compared the performance of Tfm-affected males to wild type males and females in the elevated plus maze (EPM). Two well-established indicators of anxiety-like behavior in the EPM were analyzed: total percentage of time spent on the open arms, and the percentage of open arm entries. We also analyzed the total number of open arm entries. Interestingly, Tfm-affected males spent less percentage of time on the open arms than both males and females, suggesting increased anxiety-like behavior. Percentage of open arm entries and the total number of arm entries was comparable between the groups, indicating that the observed decrease in the percentage of time spent on the open arms was not due to a global reduction in exploratory behavior. These data, in contrast to earlier reports, thus implicate androgen receptor-mediated functions in the expression of anxiety behaviors in male rats. Given that anxiety is widely reported as a precipitating factor in depression, studying the role of the androgen receptor in anxiety may give insights into the pathogenesis of major depressive disorder.

Effect of Testosterone on Inflammatory Markers in the Development of Early Atherogenesis in the Testicular-Feminized Mouse Model

BACKGROUND

Low levels of serum testosterone in men are associated with cardiovascular disease. Clinical studies show that testosterone replacement therapy (TRT) can improve symptoms of cardiovascular disease and reduce the inflammatory burden evident in atherosclerosis.

AIM

We used an in vivo animal model to determine whether testosterone influences mediators of vascular inflammation as part of its beneficial effects on atherogenesis.

METHODS

Testicular-feminized (Tfm) mice, which express low endogenous testosterone and a non-functional androgen receptor (AR), were used to assess the effect of androgen status on atheroma formation, serum lipids, and inflammatory mediators. Tfm mice were fed a high-cholesterol diet, received saline or physiological (TRT), and were compared to saline-treated XY littermates.

RESULTS

A total of 28 weeks of high-cholesterol diet caused fatty streak formation in the aortic root of XY littermates and Tfm mice, an effect significantly amplified in Tfm mice. Tfm mice on normal diet showed elevated serum tumor necrosis factor-α (TFN-α) and interleukin-6 compared to XY littermates. High-cholesterol diet induced increased monocyte chemoattractant protein-1 (MCP-1) in Tfm mice, and TFN-α and MCP-1 in XY littermates. TRT reduced fatty streak formation and serum interleukin-6 in Tfm mice but had no significant effects on lipid profiles. Monocyte/macrophage staining indicated local inflammation in aortic root fatty streak areas of all mice, with TRT reducing local inflammation through plaque reduction in Tfm mice. Fractalkine (CX₃CL1) and its receptor (CX₃CR1) were present in fatty streaks of all mice fed a high-cholesterol diet, independent of androgen status.

CONCLUSION

These results are consistent with AR-dependent and AR-independent anti-inflammatory actions of testosterone in atheroprotection, although the local anti-inflammatory mechanisms via which testosterone acts remain unknown.

Interaction between microRNAs and actin-associated protein Arpc5 regulates translational suppression during male germ cell differentiation

Decoupling of transcription and translation during postmeiotic germ cell differentiation is critical for successful spermatogenesis. Here we establish that the interaction between microRNAs and actin-associated protein Arpc5 sets the stage for an elaborate translational control mechanism by facilitating the sequestration of germ cell mRNAs into translationally inert ribonucleoprotein particles until they are later translated. Our studies reveal that loss of microRNA-dependent regulation of Arpc5, which controls the distribution of germ cell mRNAs between translationally active and inactive pools, results in abnormal round spermatid differentiation and impaired fertility. Interestingly, Arpc5 functions as a broadly acting translational suppressor, as it inhibits translation initiation by blocking 80S formation and facilitates the transport of mRNAs to chromatoid/P bodies. These findings identify a unique role for actin-associated proteins in translational regulation, and suggest that mRNA-specific and general translational control mechanisms work in tandem to regulate critical germ cell differentiation events and diverse somatic cell functions.

The role of Pax2 in mouse prostate development

BACKGROUND

Loss-of-function of Pax2 results in severe defects of the male reproductive system, and Pax2 expression is detected in mouse prostate lobes and human prostatic cancers. However, the role for Pax2 in prostate development remains poorly understood.

METHODS

The expression of Pax2 was examined by in situ hybridization at various developmental stages. Urogenital sinuses were dissected out at E18.5 from mouse Pax2 mutants and controls, cultured in vitro or grafted under the renal capsule of CD1 nude mice. The expression of prostate developmental regulatory factors was analyzed by semi-quantitative real-time PCR or immuohistochemistry.

RESULTS

Pax2 is expressed in the epithelial cells of prostate buds. Loss-of-function of Pax2 does not affect the initiation of prostatic buds, but in vitro culture assays show that the prostates of Pax2 mutants are hypomorphic and branching is severely disrupted compared to controls. RT-PCR data from Pax2 mutant prostates demonstrate increased expression levels of dorsolateral prostate marker MSMB and ventral prostate marker SBP and dramatically reduced expression levels of anterior prostate marker TGM4.

CONCLUSIONS

Pax2 is essential for mouse prostate development and regulates prostatic ductal growth, branching, and lobe-specific identity. These findings are important for understanding the molecular regulatory mechanisms in prostate development.

The role of the androgen receptor in anabolic androgenic steroid-induced aggressive behavior in C57BL/6J and Tfm mice

Humans self-administer anabolic androgenic steroids (AAS) at superphysiological doses for the purpose of building muscle mass and enhancing physique whereas considerably lower doses of AAS are prescribed in the clinic to treat a variety of disorders. A number of studies have demonstrated that individual AAS influence aggressive behavior in rats and mice, but few studies have examined the aggression-enhancing effects of combinations of AAS. Using the resident-intruder paradigm, Experiment 1 determined whether a cocktail of commonly abused AAS increased aggressive behavior in gonadally-intact male C57BL/6J mice and examined whether the androgen receptor (AR) was involved. Mice given either AAS cocktail or the cocktail and the AR antagonist, flutamide, for 6 weeks were subject to three weekly tests in which the percentage of mice that fought, the latency to initiate an aggressive event and the number of aggressive events per 5-min-fight session were recorded. In C57BL/6J mice, 6 weeks of AAS administration increased the likelihood of fighting, however, within the subset of mice that engaged in aggression, AAS did not specifically modulate the latency to fight or the number of aggressive events per fight. In addition, co-administration of flutamide only slightly altered the likelihood that mice given AAS will initiate a fight. Experiment 2 examined the aggression-promoting effects of AAS in gonadally-intact adult testicular feminization mutant (Tfm) mice, which are deficient in functional ARs. Overall, fewer Tfm mice compared to C57BL/6J mice fought in both drug conditions (vehicle or AAS). Taken together, these data suggest that given the presence of AR during development, AAS enhance adult male aggression in C57BL/6J mice through AR-independent and AR-dependent pathways. In contrast, in adult Tfm mice, the likelihood of AAS-enhanced aggression in adulthood is significantly reduced.

Androgen receptors, sex behavior, and aggression

Androgens are intricately involved in reproductive and aggressive behaviors, but the role of the androgen receptor in mediating these behaviors is less defined. Further, activity of the hypothalamic-pituitary-gonadal axis and hypothalamic-pituitary-adrenal axis can influence each other at the level of the androgen receptor. Knowledge of the mechanisms for androgens' effects on behaviors through the androgen receptor will guide future studies in elucidating male reproductive and aggressive behavior repertoires.

Role of autonomous androgen receptor signaling in prostate cancer initiation is dichotomous and depends on the oncogenic signal

The steroid hormone signaling axis is thought to play a central role in initiation and progression of many hormonally regulated epithelial tumors. It is unclear whether all cancer-initiating signals depend on an intact hormone receptor signaling machinery. To ascertain whether cell autonomous androgen receptor (AR) is essential for initiation of prostate intraepithelial neoplasia (PIN), the response of AR-null prostate epithelia to paracrine and cell autonomous oncogenic signals was assessed in vivo by using the prostate regeneration model system. Epithelial-specific loss of AR blocked paracrine FGF10-induced PIN, whereas the add back of exogenous AR restored this response. In contrast, PIN initiated by cell-autonomous, chronic-activated AKT developed independent of epithelial AR signaling. Our findings demonstrate a selective role for AR in the initiation of PIN, dependent on the signaling pathways driving tumor formation. Insights into the role of hormone receptor signaling in the initiation of epithelial tumors may help define this axis as a target for chemoprevention of carcinomas.

Essential roles of androgen signaling in Wolffian duct stabilization and epididymal cell differentiation

The epididymis is a male accessory organ and functions for sperm maturation and storage under the control of androgen. The development of the epididymis is also androgen dependent. The Wolffian duct (WD), anlagen of the epididymis, is formed in both male and female embryos; however, it is stabilized only in male embryos by testicular androgen. Androgen drives subsequent differentiation of the WD into the epididymis. Although the essential roles of androgen in WD masculinization and epididymal function have been established, little is known about cellular events regulated precisely by androgen signaling during these processes. It is also unclear whether androgen signaling, especially in the epithelia, has further function for epididymal epithelial cell differentiation. In this study we examined the cellular death and proliferation controlled by androgen signaling via the androgen receptor (AR) in WD stabilization. Analyses using AR knockout mice revealed that androgen signaling inhibits epithelial cell death in this process. Analysis of AP2α-Cre;AR(flox/Y) mice, in which AR function is deleted in the WD epithelium, revealed that epithelial AR is not required for the WD stabilization but is required for epithelial cell differentiation in the epididymis. Specifically, loss of epithelial AR significantly reduced expression of p63 that is essential for differentiation of basal cells in the epididymal epithelium. We also interrogated the possibility of regulation of the p63 gene (Trp63) by AR in vitro and found that p63 is a likely direct target of AR regulation.

Androgen receptor expression in the caput epididymal epithelium is essential for development of the initial segment and epididymal spermatozoa transit

The epididymis plays an essential role in male fertility, and disruption of epididymal function can lead to obstructive azoospermia. Formation and function of the epididymis is androgen-dependent. The androgen receptor (AR) is expressed in both the stromal and epithelial compartments of the epididymis, and androgen action mediated via stromal cells is vital for its normal development and function. However the impact of epithelial specific AR-dependent signaling in the epididymis remains underexplored. To address this, we used conditional gene-targeting in mice to selectively ablate AR from the caput epididymal epithelium, and characterized the resulting phenotype at multiple postnatal ages. Caput epithelium androgen receptor knock-out mice have normal serum testosterone concentrations at day (d) 21 and d100, but do not develop an epididymal initial segment. The remaining caput epithelium displays a significant decrease in epithelial cell height from d11 and lumen diameter from d21 and disruption of the smooth muscle layer of the caput epididymis at d100. From d21, caput epithelium androgen receptor knock-out mice accumulate cell debris, proteinaceous material, and, at later ages, spermatozoa in their efferent ducts, which prevents normal passage of spermatozoa from the testis into the cauda epididymis resulting in infertility when tested at d100. This efferent duct obstruction leads to fluid back-pressure and disruption of the seminiferous epithelium of the adult testis. We conclude that epithelial AR signaling is essential for postnatal development and function of the epididymal epithelium and that disruption of this signaling can contribute to obstructive azoospermia.

Membrane androgen receptors may mediate androgen reinforcement

Anabolic-androgenic steroid (AAS) abuse is widespread. Moreover, AAS are reinforcing, as shown by self-administration in rodents. However, the receptors that transduce the reinforcing effects of AAS are unclear. AAS may bind to classical nuclear androgen receptors (ARs) or membrane receptors. We used two approaches to examine the role of nuclear ARs in AAS self-administration. First, we tested androgen self-administration in rats with the testicular feminization mutation (Tfm), which interferes with androgen binding. If nuclear ARs are essential for AAS self-administration, Tfm males should not self-administer androgens. Tfm males and wild-type (WT) littermates self-administered the non-aromatizable androgen dihydrotestosterone (DHT) or vehicle intracerebroventricularly (ICV) at fixed-ratio (FR) schedules up to FR5. Both Tfm and WT rats acquired a preference for the active nose-poke during DHT self-administration (66.4+/-9.6 responses/4 h for Tfm and 79.2+/-11.5 for WT responses/4 h), and nose-pokes increased as the FR requirement increased. Preference scores were significantly lower in rats self-administering vehicle (42.3+/-5.3 responses/4 h for Tfm and 19.1+/-4.0 responses/4 h for WT). We also tested self-administration of DHT conjugated to bovine serum albumin (BSA) at C3 and C17, which is limited to actions at the cell surface. Hamsters were allowed to self-administer DHT, BSA and DHT-BSA conjugates for 15 days at FR1. The hamsters showed a significant preference for DHT (18.0+/-4.1 responses/4 h) or DHT-BSA conjugates (10.0+/-3.7 responses/4 h and 21.0+/-7.2 responses/4 h), but not for BSA (2.5+/-2.4 responses/4 h). Taken together, these data demonstrate that nuclear ARs are not required for androgen self-administration. Furthermore, androgen self-administration may be mediated by plasma membrane receptors.

Local signalling environments and human male infertility: what we can learn from mouse models

Infertility is one of the most prevalent public health problems facing young adult males in today's society. A clear, treatable cause of infertility cannot be determined in a large number of these patients, and a growing body of evidence suggests that infertility in many of these men may be due to genetic causes. Studies using mouse knockout technology have been integral for examination of normal spermatogenesis and to identify proteins essential for this process, which in turn are candidate genes for human male infertility. Successful spermatogenesis depends on a delicate balance of local signalling factors, and this review focuses on the genes that encode these factors. Normal functioning of all testicular cell types is essential for fertility and might also be crucial to prevent germ cell oncogenesis. Analysis of these signalling processes in spermatogenesis using mouse models has provided investigators with an invaluable tool to effectively translate basic science research to the research of human disease and infertility.

Androgenic regulation of ventral epithelial bud number and pattern in mouse urogenital sinus

The ventral urogenital sinus (UGS) of control male mice has two rows of 3-4 prostatic buds at birth, but how androgens regulate ventral bud (VB) number and patterning is unclear. VBs in both sexes appeared to be a mixture of prostatic and urethral buds. UGSs from Tfm male and antiandrogen (flutamide)-exposed mice had small VBs, suggesting that initiation of some VBs is androgen independent. Tfm male mice are widely considered completely androgen insensitive yet their UGSs were 5alpha-dihydrotestosterone (DHT)- responsive. VBs (6-8) were generally distributed bimodally on the left-right axis at both minimal and normal male androgen signaling. Yet control females and DHT-exposed Tfm males had 13-14 VBs, whose left-right distribution was fairly uniform. These results suggest that VB number and distribution respond biphasically as androgen signaling increases from minimal, and that androgens regulate bud specification. Complete VB agenesis by the selective budding inhibitor 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) required high androgen signaling.

[Sex hormones and dry eye]

Among ophthalmic diseases dry eye in its various forms, represents an entity with one of the highest prevalences and at the same time the lowest chance for causal therapy. Since some years there is growing evidence that sex hormones play a key role in the formation and course of the disease and thus provide potentially promising approaches for therapy. The objective of this article is to briefly outline current scientific knowledge on the relationship between androgens, estrogens,and progesterones on the one hand and the lacrimal gland and Meibomian glands respectively.

Androgen-induced Rhox homeobox genes modulate the expression of AR-regulated genes

Rhox5, the founding member of the reproductive homeobox on the X chromosome (Rhox) gene cluster, encodes a homeodomain-containing transcription factor that is selectively expressed in Sertoli cells, where it promotes the survival of male germ cells. To identify Rhox5-regulated genes, we generated 15P-1 Sertoli cell clones expressing physiological levels of Rhox5 from a stably transfected expression vector. Microarray analysis identified many genes altered in expression in response to Rhox5, including those encoding proteins controlling cell cycle regulation, apoptosis, metabolism, and cell-cell interactions. Fifteen of these Rhox5-regulated genes were chosen for further analysis. Analysis of Rhox5-null male mice indicated that at least nine of these are Rhox5-regulated in the testes in vivo. Many of them have distinct postnatal expression patterns and are regulated by Rhox5 at different postnatal time points. Most of them are expressed in Sertoli cells, indicating that they are candidates to be directly regulated by Rhox5. Transfection analysis with expression vectors encoding different mouse and human Rhox family members revealed that the regulatory response of a subset of these Rhox5-regulated genes is both conserved and redundant. Given that Rhox5 depends on androgen receptor (AR) for expression in Sertoli cells, we examined whether some Rhox5-regulated genes are also regulated by AR. We provide several lines of evidence that this is the case, leading us to propose that RHOX5 serves as a key intermediate transcription factor that directs some of the actions of AR in the testes.

Partner preference and mount latency are masculinized in androgen insensitive rats

The sexual motivation of male rats may be inferred from a preference to stay in proximity to estrous female partners, and also from a short latency to show mounting behavior. Here, partner preference was assessed in rats carrying the testicular feminization mutation (TFM), and compared to wild type (WT) males in one version of this paradigm, and WT females and males in another version. Additionally, mount latency was quantified in the TFMs and compared to WT males in order to assess arousal levels, as this has not been previously reported. When presented with a choice between proximity to an estrous or non-estrous female, WT males and TFMs demonstrated similar preferences for the estrous female. Estrous females, conversely, preferred to spend time with the WT male. In agreement with previous reports we observed several sexual performance deficits in the TFMs, but mount latencies were in the male range. Given that the TFMs reliably choose to spend time with the estrous female in the partner preference tests, and that they display normal arousal levels (reflected in masculinized mount latencies), the data suggest the motivation to engage in sexual behavior is masculine in the TFM rat and that possession of functional androgen receptors is not crucial in these behaviors.

Androgen insensitivity syndrome

Over the past four years, major advances in the understanding of the aetiology and pathogenesis of the androgen insensitivity syndrome (AIS) have occurred. This review aims to summarize current information on clinical, diagnostic, therapeutic and molecular aspects of AIS.

A role for the androgen metabolite, 5alpha-androstane-3beta,17beta-diol, in modulating oestrogen receptor beta-mediated regulation of hormonal stress reactivity

Activation of the hypothalamic-pituitary-adrenal (HPA) axis is a basic response of animals to environmental perturbations that threaten homeostasis. These responses are regulated by neurones in the paraventricular nucleus of the hypothalamus (PVN) that synthesise and secrete corticotrophin-releasing hormone (CRH). Other PVN neuropeptides, such as arginine vasopressin and oxytocin, can also modulate activity of CRH neurones in the PVN and enhance CRH secretagogue activity of the anterior pituitary gland. In rodents, sex differences in HPA reactivity are well established; females exhibit a more robust activation of the HPA axis after stress than do males. These sex differences primarily result from opposing actions of sex steroids, testosterone and oestrogen, on HPA function. Ostreogen enhances stress activated adrenocorticotrophic hormone (ACTH) and corticosterone (CORT) secretion, whereas testosterone decreases the gain of the HPA axis and inhibits ACTH and CORT responses to stress. Data show that androgens can act directly on PVN neurones in the male rat through a novel pathway involving oestrogen receptor (ER)beta, whereas oestrogen acts predominantly through ERalpha. Thus, we examined the hypothesis that, in males, testosterone suppresses HPA function via an androgen metabolite that binds ERbeta. Clues to the neurobiological mechanisms underlying such a novel action can be gleaned from studies showing extensive colocalisation of ERbeta in oxytocin-containing cells of the PVN. Hence, in this review, we address the possibility that testosterone inhibits HPA reactivity by metabolising to 5alpha-androstane-3beta,17beta-diol, a compound that binds ERbeta and regulates oxytocin containing neurones of the PVN. These findings suggest a re-evaluation of studies examining pathways for androgen receptor signalling.

Does prostate cancer co-opt the developmental program?

The hypothesis that cancer is a caricature of normal development and tissue renewal was originally based on descriptive studies of normal tissues and cancers. The concepts that arose from these studies were that both normal tissues and tumors are sustained by a self-renewing population of stem cells that initially gives rise to undifferentiated and highly proliferative progeny. Eventually, derivatives of these proliferating cells become growth quiescent and express differentiation markers characteristic of the organs within which they reside. A major difference between normal tissues and tumors is the impairment of differentiation in tumors such that undifferentiated, mitotically active cells accumulate in tumors. An important feature of the model is the idea that the biology of the undifferentiated and proliferating cell populations in tumors is governed by the same pathways that regulate normal development and tissue renewal. At the time these ideas were formulated, we lacked sufficient understanding of the molecular and cellular basis of prostate development and cancer progression to evaluate the validity of these ideas for understanding prostate cancer. Research in recent years has validated the prediction that cells with stem cell-like properties are a critical source of new cells both during prostate development and during prostate cancer progression. It is also the case that many of the genes that regulate prostatic development re-appear during prostate cancer progression. A closer examination of the best understood of these developmental regulatory pathways, the androgen-signaling pathway, reveals important differences between normal development and tumors. This pathway is co-opted in prostate cancer by genetic and epigenetic changes that alter the molecular details of how signaling is initiated and alter the transcriptional outcome of signaling by silencing key targets of androgen signaling and fusing androgen-responsive promoters to new genes to create new targets for androgen signaling. Future research is needed to understand if other developmental regulatory pathways are altered during prostate progression in a manner analogous to the androgen signaling pathway.

GPRC6A null mice exhibit osteopenia, feminization and metabolic syndrome

Background

GPRC6A is a widely expressed orphan G-protein coupled receptor that senses extracellular amino acids, osteocalcin and divalent cations in vitro. The physiological functions of GPRC6A are unknown.

Methods/Principal Findings

In this study, we created and characterized the phenotype of GPRC6A^−/− mice. We observed complex metabolic abnormalities in GPRC6A^−/− mice involving multiple organ systems that express GPRC6A, including bone, kidney, testes, and liver. GPRC6A^−/− mice exhibited hepatic steatosis, hyperglycemia, glucose intolerance, and insulin resistance. In addition, we observed high expression of GPRC6A in Leydig cells in the testis. Ablation of GPRC6A resulted in feminization of male GPRC6A^−/− mice in association with decreased lean body mass, increased fat mass, increased circulating levels of estradiol, and reduced levels of testosterone. GPRC6A was also highly expressed in kidney proximal and distal tubules, and GPRC6A^−/− mice exhibited increments in urine Ca/Cr and PO₄/Cr ratios as well as low molecular weight proteinuria. Finally, GPRC6A^−/− mice exhibited a decrease in bone mineral density (BMD) in association with impaired mineralization of bone.

Conclusions/Significance

GPRC6A^−/− mice have a metabolic syndrome characterized by defective osteoblast-mediated bone mineralization, abnormal renal handling of calcium and phosphorus, fatty liver, glucose intolerance and disordered steroidogenesis. These findings suggest the overall function of GPRC6A may be to coordinate the anabolic responses of multiple tissues through the sensing of extracellular amino acids, osteocalcin and divalent cations.

Antagonistic effects of testosterone and the endocrine disruptor mono-(2-ethylhexyl) phthalate on INSL3 transcription in Leydig cells

Insulin-like 3 (INSL3) is a small peptide produced by testicular Leydig cells throughout embryonic and postnatal life and by theca and luteal cells of the adult ovary. During fetal life, INSL3 regulates testicular descent in males, whereas in adults, it acts as an antiapoptotic factor for germ cells in males and as a follicle selection and survival factor in females. Despite its considerable roles in the reproductive system, the mechanisms that regulate Insl3 expression remain poorly understood. There is accumulating evidence suggesting that androgens might regulate Insl3 expression in Leydig cells, but transcriptional data are still lacking. We now report that testosterone does increase Insl3 mRNA levels in a Leydig cell line and primary Leydig cells. We also show that testosterone activates the activity of the Insl3 promoter from different species. In addition, the testosterone-stimulating effects on Insl3 mRNA levels and promoter activity require the androgen receptor. We have mapped the testosterone-responsive element to the proximal Insl3 promoter region. This region, however, lacks a consensus androgen response element, suggesting an indirect mechanism of action. Finally we show that mono-(2-ethylhexyl) phthalate, a widely distributed endocrine disruptor with antiandrogenic activity previously shown to inhibit Insl3 expression in vivo, represses Insl3 transcription, at least in part, by antagonizing testosterone/androgen receptor action. All together our data provide important new insights into the regulation of Insl3 transcription in Leydig cells and the mode of action of phthalates.

Classical androgen receptors in non-classical sites in the brain

Androgen receptors are expressed in many different neuronal populations in the central nervous system where they often act as transcription factors in the cell nucleus. However, recent studies have detected androgen receptor immunoreactivity in neuronal and glial processes of the adult rat neocortex, hippocampal formation, and amygdala as well as in the telencephalon of eastern fence and green anole lizards. This review discusses previously published findings on extranuclear androgen receptors, as well as new experimental results that begin to establish a possible functional role for androgen receptors in axons within cortical regions. Electron microscopic studies have revealed that androgen receptor immunoreactive processes in the rat brain correspond to axons, dendrites and glial processes. New results show that lesions of the dorsal CA1 region by local administration of ibotenic acid reduce the density of androgen receptor immunoreactive axons in the cerebral cortex and the amygdala, suggesting that these axons may originate in the hippocampus. Androgen receptor immunoreactivity in axons is also decreased by the intracerebroventricular administration of colchicine, suggesting that androgen receptor protein is transported from the perikaryon to the axons by fast axonal transport. Androgen receptors in axons located in the cerebral cortex and amygdala and originating in the hippocampus may play an important role in the rapid behavioral effects of androgens.

The role of androgen receptors in the masculinization of brain and behavior: what we've learned from the testicular feminization mutation

Many studies demonstrate that exposure to testicular steroids such as testosterone early in life masculinizes the developing brain, leading to permanent changes in behavior. Traditionally, masculinization of the rodent brain is believed to depend on estrogen receptors (ERs) and not androgen receptors (ARs). According to the aromatization hypothesis, circulating testosterone from the testes is converted locally in the brain by aromatase to estrogens, which then activate ERs to masculinize the brain. However, an emerging body of evidence indicates that the aromatization hypothesis cannot fully account for sex differences in brain morphology and behavior, and that androgens acting on ARs also play a role. The testicular feminization mutation (Tfm) in rodents, which produces a nonfunctional AR protein, provides an excellent model to probe the role of ARs in the development of brain and behavior. Tfm rodent models indicate that ARs are normally involved in the masculinization of many sexually dimorphic brain regions and a variety of behaviors, including sexual behaviors, stress response and cognitive processing. We review the role of ARs in the development of the brain and behavior, with an emphasis on what has been learned from Tfm rodents as well as from related mutations in humans causing complete androgen insensitivity.

Hypogonadal Mouse, a Model to Study the Effects of the Endogenous Lack of Gonadotropins on Apoptosis1

Testicular apoptosis is involved in the regulation of germ cell numbers, allowing optimal sperm production. Apoptosis has been described to occur in response to the absence of hormonal stimulation of the testis. Here we investigate the effect of the physiological lack of gonadotropins from birth using the hypogonadal (homozygous for the mutant allele Gnrh1(hpg)) mouse as a model. We pursued a concerted strategy using microarray analysis and RT-PCR to assess transcript levels, TUNEL to quantify the incidence of apoptosis, and Western blotting to assess the respective contribution of the extrinsic and intrinsic apoptotic pathways. Our results indicate a large increase in apoptosis of both somatic and germ cell compartments in the hpg testis, affecting Sertoli cells as well as germ cells of all ages. We confirmed our observations of Sertoli cell apoptosis using anti-Mullerian inhibiting substance staining and staining for cleaved fodrin alpha. In the somatic compartment, apoptosis is primarily regulated via the membrane receptor (extrinsic) apoptotic pathway, while in the germ cell compartment, regulation occurs via both the mitochondrial (intrinsic) and membrane receptor (extrinsic) apoptotic pathways, the latter potentially in a stage-specific manner. This study is the first report of spermatogonial apoptosis in response to gonadotropin deficiency as well as the first report of Sertoli cell apoptosis in response to gonadotropin deficiency in the mouse.