Trinucleotide repeats in the human androgen receptor: a molecular basis for disease

CAG and GGN repeat polymorphisms in the androgen receptor gene of a Chilean pediatric cohort with idiopathic inguinal cryptorchidism

BACKGROUND

Cryptorchidism is one of the most common congenital disorders in boys and it is associated with a higher risk of sub-fertility and testicular cancer. Testicular descent occurs during embryo-fetal development in two phases, transabdominal and inguino-scrotal. In the latter process, androgens play a leading role. The androgen receptor has in its N-terminal domain, two aminoacidic repeats encoded by polymorphic nucleotide repetitions: (CAG)nCAA and GGN. The number of repetitions of these trinucleotides has been associated with different transactivation capacities and sensitivities of the androgen receptor response.

OBJECTIVE

To determine whether pediatric Chilean individuals with idiopathic inguinal cryptorchidism have a different number of CAG and/or GGN repeats polymorphisms compared with controls.

MATERIALS AND METHODS

A total of 109 cases with idiopathic inguinal cryptorchidism (26 bilateral and 83 unilateral) were studied by polymerase chain reaction amplification from DNA extracted from peripheral blood, followed by fragment size analysis by capillary electrophoresis, which were compared with 140 controls.

RESULTS

The CAG26 repeats allele was increased in the total cases (8.3% vs. 1.4%; p = 0.012; odds ratio = 6.21, 95% confidence interval 1.31-29.4), and in bilateral cases compared to controls (11.5% vs. 1.4%; p = 0.028; odds ratio = 9 CI 95% 1.43-56.8). Similarly, CAG > 22 alleles were increased in the total cases (62.4% vs. 49.3%, p = 0.041), and more significantly in bilateral cases (73.1% vs. 49.3%; p = 0.032; odds ratio = 2.79, 95% confidence interval 1.1-7.1). In addition, CAG < 18 alleles were not observed among cases, but were present in 5.7% of controls (p = 0.01). Regarding the GGN repeats, no differences were observed between cases and controls either when analyzing separately unilateral and bilateral cryptorchidism. The joint analysis of the distribution of CAG and GGN alleles showed that the CAG26 allele was present with GGN23, hence the combination CAG26/GGN23 alleles was equally increased in bilateral cases compared with controls (11.5% vs. 1.4%). In contrast, CAG < 18 was preferably observed in the combination CAG < 18/GGN≠23 and was absent in the total cases (4.3% vs. 0%; p = 0.037).

DISCUSSION

These results suggest that greater lengths of CAG alleles may contribute to a diminished androgen receptor function. The CAG26 allele alone or in combination with GGN23 was associated with a higher risk of bilateral cryptorchidism. On the other hand, CAG < 18 and the CAG < 18/GGN≠23 allele combination may reduce the probability of cryptorchidism.

Native functions of short tandem repeats

Over a third of the human genome is comprised of repetitive sequences, including more than a million short tandem repeats (STRs). While studies of the pathologic consequences of repeat expansions that cause syndromic human diseases are extensive, the potential native functions of STRs are often ignored. Here, we summarize a growing body of research into the normal biological functions for repetitive elements across the genome, with a particular focus on the roles of STRs in regulating gene expression. We propose reconceptualizing the pathogenic consequences of repeat expansions as aberrancies in normal gene regulation. From this altered viewpoint, we predict that future work will reveal broader roles for STRs in neuronal function and as risk alleles for more common human neurological diseases.

Androgens and Androgen Receptors as Determinants of Vascular Sex Differences Across the Lifespan

Androgens, including testosterone and its more potent metabolite dihydrotestosterone, exert multiple actions in the body. Physiologically, they play a critical role in male sex development. In addition, they influence vascular function, including arterial vasodilation and mediation of myogenic tone. Androgens are produced from 9 weeks' gestation in the human fetal testis, as well as in small amounts by the adrenal glands. Serum concentrations vary according to age and sex. The vasculature is a target for direct actions of androgens, which bind to various sex hormone receptors expressed in endothelial and vascular smooth muscle cells. Androgens exert both vasoprotective and vasoinjurious effects, depending on multiple factors including sex-specific effects of androgens, heterogeneity of the vascular endothelium, differential expression of androgen and sex hormone receptors in endothelial and vascular smooth muscle cells, and the chronicity of androgen administration. Long-term administration of androgens induces vasoconstriction and influences endothelial permeability, whereas acute administration may have opposite effects. At the cellular level, androgens stimulate endothelial cell production of nitric oxide and inhibit proinflammatory signalling pathways, inducing vasorelaxation and vasoprotection. However, androgens also activate endothelial production of vasoconstrictors and stimulate recruitment of endothelial progenitor cells. In humans, both androgen deficiency and androgen excess are associated with increased cardiovascular morbidity and mortality. This review discusses how androgens modulate vascular sex differences across the lifespan by considering the actions and production of androgens in both sexes and describes how cardiovascular risk is altered as levels of androgens change with aging.

The number of androgen receptor CAG repeats and mortality in men

INTRODUCTION

The androgen receptor (AR) mediates peripheral effects of testosterone. Evidence suggests that the number of CAG repeats in exon-1 of the AR gene negatively correlates with AR transcriptional activity. The aim of this analysis was to determine the association between CAG repeat number and mortality in men.

METHODS

Men aged 40-79 years were recruited from primary care for participation in the UK arm of the European Male Aging Study between 2003 and 2005. Cox proportional hazards modelling was used to determine the association between CAG repeat number/mortality. Results were expressed as hazard ratios(HR)/95% confidence intervals (CI).

RESULTS

312 men were followed up. The mean baseline age was 59.5 years. At follow up, 85/312(27%) men had died. CAG repeat length ranged from 14 to 39, with the highest proportion of CAG repeat number at 21 repeats(16.4%). In a multivariable model, using men with CAG repeat numbers of 22-23 as the reference, men with a lower number of CAG repeats(<22) showed a trend for a higher mortality in the follow-up period (HR 1.46 (0.75, 2.81)) as did men with higher number of repeats (>23) (1.37 (0.65, 2.91)).

CONCLUSION

Our data suggest that CAG repeat number may partially influence the risk of mortality in men. Further larger studies are required to quantify the effect.

Influence of gonadal steroids on cortical surface area in infancy

Sex differences in the human brain emerge as early as mid-gestation and have been linked to sex hormones, particularly testosterone. Here, we analyzed the influence of markers of early sex hormone exposure (polygenic risk score (PRS) for testosterone, salivary testosterone, number of CAG repeats, digit ratios, and PRS for estradiol) on the growth pattern of cortical surface area in a longitudinal cohort of 722 infants. We found PRS for testosterone and right-hand digit ratio to be significantly associated with surface area, but only in females. PRS for testosterone at the most stringent P value threshold was positively associated with surface area development over time. Higher right-hand digit ratio, which is indicative of low prenatal testosterone levels, was negatively related to surface area in females. The current work suggests that variation in testosterone levels during both the prenatal and postnatal period may contribute to cortical surface area development in female infants.

Gene variants associated with acne vulgaris presentation and severity: a systematic review and meta-analysis

BACKGROUND

Multiple factors have been attributed to acne vulgaris predisposition and individual variations in the severity of skin symptoms, and genetics stood out as one of the major factors.

METHODS

We performed a systematic review on the genes and their variants that have been investigated for association with acne presentation and severity. A random-effect meta-analysis using the allele model (minor allele vs. major allele) was also conducted to provide an overall estimation of risk effects of frequently reported gene variants. This included a subset data of 982 acne cases and 846 controls extracted from our existing GWAS database on various allergic and skin diseases among Singapore Chinese.

RESULTS

Systematic review of 51 articles covering Asians and Caucasians found 60 genes/loci and their 100 variants implicated in acne; majority of them were in the intron, coding region/missense, and promoter regions. The commonly studied candidate genes/gene families include tumor necrosis factor (TNF), and the interleukin (IL) and cytochrome P450 (CYP) gene families. Our meta-analysis showed that most of the analyzed gene variants exhibited insignificant pooled odds ratio (pOR) and significant heterogeneity between studies. Nevertheless, we found that TNF rs1800629 A allele carriers and CYP17A1 rs743572 T allele carriers had significantly reduced mild acne risk [pOR: 0.60; 95% Confidence Interval (CI): 0.33-0.86] and severe acne risk (pOR: 0.59; 95% CI: 0.40-0.79), respectively, across populations. Overall, FST (follistatin) rs629725 A allele poses a significantly modest increased risk for acne presentation (pOR: 1.19, 95% CI: 1.14, 1.23), but neither TIMP2 (TIMP metallopeptidase inhibitor 2) rs8179090 nor CYP1A1 rs4646903 (pOR: 0.96, 95% CI: 0.80-1.12; pOR: 0.95, 95% CI: 0.83, 1.08), respectively. We discovered 15 novel SNPs in the 3' UTR region of the Toll-like Receptor 4 gene (TLR4) associated with acne presentation.

CONCLUSIONS

This systematic review and meta-analysis suggest that genes influencing inflammatory responses, specifically TNF, and genes influencing the function and activity of sebaceous glands, specifically CYP17A1 and FST, have potential risk variants for acne presentation and severity across populations. Understanding the genetic susceptibility factors and biological pathways involved in the pathogenesis of acne will help us to gain insights into developing effective acne treatments.

Assessing COVID-19 susceptibility through analysis of the genetic and epigenetic diversity of ACE2-mediated SARS-CoV-2 entry

There is considerable variation in disease course among individuals infected with SARS-CoV-2. Many of them do not exhibit any symptoms, while some others proceed to develop COVID-19; however, severity of COVID-19 symptoms greatly differs among individuals. Focusing on the early events related to SARS-CoV-2 entry to cells through the ACE2 pathway, we describe how variability in (epi)genetic factors can conceivably explain variability in disease course. We specifically focus on variations in ACE2, TMPRSS2 and FURIN genes, as central components for SARS-CoV-2 infection, and on other molecules that modulate their expression such as CALM, ADAM-17, AR and ESRs. We propose a genetic classifier for predicting SARS-CoV-2 infectivity potential as a preliminary tool for identifying the at-risk-population. This tool can serve as a dynamic scaffold being updated and adapted to validated (epi)genetic data. Overall, the proposed approach holds potential for better personalization of COVID-19 handling.

Genetic Variation in the Androgen Receptor Modifies the Association Between Testosterone and Vitality in Middle-Aged Men

BACKGROUND

Low vitality is a common symptom of testosterone deficiency; however, clinical trial results remain inconclusive regarding the responsiveness of this symptom to hormone replacement.

AIM

The aim of the present study was to determine if the relationship between circulating testosterone levels and vitality would be moderated by the CAG repeat length in the androgen receptor (AR) gene, which influences the receptor's sensitivity to testosterone.

METHODS

We examined 676 men in the Vietnam Era Twin Study of Aging when they were, on average, 55.4 years old (SD = 2.5). Salivary testosterone levels were measured by using 3 samples collected at waking on 3 nonconsecutive days. The average testosterone level was classified as low, normal, or high based on 1-SD cutoffs. Analyses were conducted using multilevel, mixed linear models, which accounted for the nonindependence of the twin data, and adjusted for the effects of age, ethnicity, BMI, chronic health conditions, depressive symptoms, and sleep quality.

OUTCOMES

Vitality was measured using the 36-item Short Form (SF-36) vitality subscale.

RESULTS

We observed a significant interaction between salivary testosterone and the AR-CAG repeat length. When the repeat length was short, men with low testosterone had significantly lower vitality. As the AR-CAG repeat length increased, the magnitude of the testosterone effect decreased.

CLINICAL TRANSLATION

The observed interaction between testosterone and variation in the AR gene suggests that men with more sensitive ARs, as indicated by a shorter AR-CAG repeat, are more likely to experience symptoms of age-related testosterone deficiency.

STRENGTHS & LIMITATIONS

Strengths of the present study include our use of a large community-based sample, the use of multiple testosterone measurements, and the availability of a comprehensive set of covariates that may impact the association of interest. Limitations include the homogeneous nature of the sample with respect to ethnicity, the brevity of the 36-item Short Form vitality subscale, and our inability to establish change in testosterone levels because of the cross-sectional nature of data.

CONCLUSIONS

The association between testosterone and vitality appears to be clinically meaningful and is in part dependent on variation in the AR gene. Panizzon MS, Bree K, Hsieh T-C, et al. Genetic Variation in the Androgen Receptor Modifies the Association Between Testosterone and Vitality in Middle-Aged Men. J Sex Med 2020;17:2351-2361.

Functional Expression of Choline Transporter-Like Protein 1 in LNCaP Prostate Cancer Cells: A Novel Molecular Target

Prostate cancer is one of the most common cancers in men. Choline PET or PET/CT has been used to visualize prostate cancer, and high levels of choline accumulation have been observed in tumors. However, the uptake system for choline and the functional expression of choline transporters in prostate cancer are not completely understood. In this study, the molecular and functional aspects of choline uptake were investigated in the LNCaP prostate cancer cell line along with the correlations between choline uptake and cell viability in drug-treated cells. Choline transporter-like protein 1 (CTL1) and CTL2 mRNA were highly expressed in LNCaP cells. CTL1 and CTL2 were located in the plasma membrane and mitochondria, respectively. [³H]Choline uptake was mediated by a single Na⁺-independent, intermediate-affinity transport system in the LNCaP cells. The anticancer drugs, flutamide and bicalutamide, inhibited cell viability and [³H]choline uptake in a concentration-dependent manner. The correlations between the effects of these drugs on cell viability and [³H]choline uptake were significant. Caspase-3/7 activity was significantly increased by both flutamide and bicalutamide. Furthermore, these drugs decreased CTL1 expression in the prostate cancer cell line. These results suggest that CTL1 is functionally expressed in prostate cancer cells and are also involved in abnormal proliferation. Identification of this CTL1-mediated choline transport system in prostate cancer cells provides a potential new therapeutic target for the treatment of this disease.

Androgen receptor with short polyglutamine tract preferably enhances Wnt/β-catenin-mediated prostatic tumorigenesis

Polyglutamine (polyQ) tract polymorphism within the human androgen receptor (AR) shows population heterogeneity. African American men possess short polyQ tracts significantly more frequently than Caucasian American men. The length of polyQ tracts is inversely correlated with the risk of prostate cancer, age of onset, and aggressiveness at diagnosis. Aberrant activation of Wnt signaling also reveals frequently in advanced prostate cancer, and an enrichment of androgen and Wnt signaling activation has been observed in African American patients. Here, we assessed aberrant expression of AR bearing different polyQ tracts and stabilized β-catenin in prostate tumorigenesis using newly generated mouse models. We observed an early onset oncogenic transformation, accelerated tumor cell growth, and aggressive tumor phenotypes in the compound mice bearing short polyQ tract AR and stabilized β-catenin. RNA sequencing analysis showed a robust enrichment of Myc-regulated downstream genes in tumor samples bearing short polyQ AR versus those with longer polyQ tract AR. Upstream regulator analysis further identified Myc as the top candidate of transcriptional regulators in tumor cells from the above mouse samples with short polyQ tract AR and β-catenin. Chromatin immunoprecipitation analyses revealed increased recruitment of β-catenin and AR on the c-Myc gene regulatory locus in the tumor tissues expressing stabilized β-catenin and shorter polyQ tract AR. These data demonstrate a promotional role of aberrant activation of Wnt/β-catenin in combination with short polyQ AR expression in prostate tumorigenesis and suggest a potential mechanism underlying aggressive prostatic tumor development, which has been frequently observed in African American patients.

The effect of GGC and CAG repeat polymorphisms on the androgen receptor gene in response to finasteride therapy in men with androgenetic alopecia

Background:

It should be assessed whether the polymorphisms on androgen receptor gene can affect therapeutic response to androgenetic alopecia (AGA) medications. We aimed to find a link between polymorphisms on the androgen receptor gene (including the number of triple sequences of cytosine, adenine, and guanine [CAG] and guanine-guanine-cytosine [GGC]) and response to treatment with finasteride in male patients.

Materials and Methods:

This case–control study was performed on 25 consecutive male patients with hereditary AGA and 25 sex-matched healthy individuals without AGA. The complete sequence of the gene was extracted from the NCBI database. To replicate the samples, real-time polymerase chain reaction technique was used for the pointed gene and the results were confirmed by the sequencing technique.

Results:

The mean number of CAG sequences in two groups with and without baldness, was 23.16 ± 0.47 and 23.04 ± 0.67. For GGC sequencing with and without baldness, mean count was 22.22 ± 1.45 and 19.92 ± 81.2, respectively, which was significantly higher in the group with baldness. There was no association between number of CAG sequence and improvement in hair loss or the level of patients' satisfaction, but lower number of GGC sequences was associated with higher rate of stopping hair loss, more new hair growth, higher level of satisfaction, and more clinical response to finasteride and clinical improvement in AGA patients.

Conclusion:

Counting of GGC sequence in the gene encoding the androgen receptor is associated with an increase in odds of baldness and a decrease in the response rate to finasteride in AGA patients.

CAG polymorphism in the androgen receptor gene in women may be associated with nodulocystic acne

Introduction

Acne vulgaris (AV) is a multifactorial, inflammatory disease of the pilosebaceous unit. Hormones play a major role in the pathogenesis of acne. In cases of hyperandrogenism; hirsutism, acne, seborrhoea and alopecia appear in women. However, severe acne can also be seen without evidence of hyperandrogenism. In this case, hypersensitivity of the androgen receptor gene (ARG) encoded in the X chromosome, which is the only receptor for androgens, can be considered. ARG contains a polymorphic CAG triple loop encoding the polyglutamine pathway at the 5'end of exon 1.

Aim

To investigate CAG repeat polymorphism in the ARG in nodulocystic acne patients in Turkish population.

Material and methods

This prospective clinical study was conducted between 2016 and 2017 in accordance with the tenets of the Declaration of Helsinki. DNA isolation from blood was performed using the RTA^® Genomic DNA Isolation Kit. The fragment lengths obtained from the device to determine CAG repeat numbers were analysed based on -288 bp length 22 CAG repeat content.

Results

A total of 199 subjects; 100 patients (51 males, 49 females) and 99 controls (49 males, 50 females) were included in the study. The mean allele length in the patient group was 19.34; and 19.7 in the control group. There was a statistically significant difference between female patients and the control group, when the patients and control groups were compared by gender (p = 0.0059).

Conclusions

The CAG trinucleotide repeat count in the ARG may be associated with acne, without hirsutism findings.

Genetic Link Between Gender Dysphoria and Sex Hormone Signaling

CONTEXT

There is a likely genetic component to gender dysphoria, but association study data have been equivocal.

OBJECTIVE

We explored the specific hypothesis that gender dysphoria in transgender women is associated with variants in sex hormone-signaling genes responsible for undermasculinization and/or feminization.

DESIGN

Subject-control analysis included 380 transgender women and 344 control male subjects. Associations and interactions were investigated between functional variants in 12 sex hormone-signaling genes and gender dysphoria in transgender women.

SETTING

Patients were recruited from the Monash Gender Clinic, Monash Health, Melbourne, Australia, and the University of California, Los Angeles.

PATIENTS

Caucasian (non-Latino) transgender women were recruited who received a diagnosis of transsexualism [Diagnostic and Statistical Manual of Mental Disorders (DSM)-IV) or gender dysphoria (DSM-V)] pre- or postoperatively. Most were receiving hormone treatment at the time of recruitment.

MAIN OUTCOME MEASURED

Genomic DNA was genotyped for repeat length polymorphisms or single nucleotide polymorphisms.

RESULTS

A significant association was identified between gender dysphoria and ERα, SRD5A2, and STS alleles, as well as ERα and SULT2A1 genotypes. Several allele combinations were also overrepresented in transgender women, most involving AR (namely, AR-ERβ, AR-PGR, AR-COMT, CYP17-SRD5A2). Overrepresented alleles and genotypes are proposed to undermasculinize/feminize on the basis of their reported effects in other disease contexts.

CONCLUSION

Gender dysphoria may have an oligogenic component, with several genes involved in sex hormone-signaling contributing.

Size matters: Associations between the androgen receptor CAG repeat length and the intrafollicular hormone milieu

Granulosa cell (GC) expressed androgen receptors (AR) and intrafollicular androgens are central to fertility. The transactivating domain of the AR contains a polymorphic CAG repeat sequence, which is linked to the transcriptional activity of AR and may influence the GC function. This study aims to evaluate the effects of the AR CAG repeat length on the intrafollicular hormone profiles, and the gene expression profiles of GC from human small antral follicles. In total, 190 small antral follicles (3-11 mm in diameter) were collected from 58 women undergoing ovarian cryopreservation for fertility preservation. The biallelic mean of the CAG repeat lengths were calculated for each woman, and grouped in three groups: Long CAG repeats (23-26 mean CAG); medium CAG repeats (20.5-22.5 mean CAG) and short CAG repeats (17.5-20.0 mean CAG). The following parameters were measured: follicle diameter, intrafollicular levels of Anti-Müllerian Hormone (AMH), progesterone, oestradiol, testosterone and androstenedione, and GC gene expression levels of FSHR, LHR, AR, CYP19A1, and AMH. The long CAG repeat lengths were associated with significantly decreased testosterone levels, as compared to medium CAG repeats (P = 0.05) and short CAG repeats (P = 0.003). Furthermore, in follicles 3-6 mm in diameter, the long CAG repeats were associated with significantly increased LHR and CYP19A1 gene expression levels compared to short CAG repeat lengths (P = 0.004 and P = 0.04 respectively), and significantly increased LHR expression compared to medium CAG repeat lengths (P = 0.03). In conclusion, long CAG repeat lengths in the AR were associated to significant attenuated levels of androgens and an increased conversion of testosterone into oestradiol, in human small antral follicles.

Androgen receptor gene polymorphism in zebra species

Androgen receptor genes (AR) have been found to have associations with reproductive development, behavioral traits, and disorders in humans. However, the influence of similar genetic effects on the behavior of other animals is scarce. We examined the loci AR glutamine repeat (ARQ) in 44 Grevy's zebras, 23 plains zebras, and three mountain zebras, and compared them with those of domesticated horses. We observed polymorphism among zebra species and between zebra and horse. As androgens such as testosterone influence aggressiveness, AR polymorphism among equid species may be associated with differences in levels of aggression and tameness. Our findings indicate that it would be useful to conduct further studies focusing on the potential association between AR and personality traits, and to understand domestication of equid species.

Influence of CAG Repeat Polymorphism on the Targets of Testosterone Action

In the last decade, ample evidence has demonstrated the growing importance of androgen receptor (AR) CAG repeat polymorphism in andrology. This genetic parameter is able to condition the peripheral effects of testosterone and therefore to influence male sexual function and fertility, cardiovascular risk, body composition, bone metabolism, the risk of prostate and testicular cancer, the psychiatric status, and the onset of neurodegenerative disorders. In this review, we extensively discuss the literature data and identify a role for AR CAG repeat polymorphism in conditioning the systemic testosterone effects. In particular, our main purpose was to provide an updated text able to shed light on the many and often contradictory findings reporting an influence of CAG repeat polymorphism on the targets of testosterone action.

CAG repeat testing of androgen receptor polymorphism: is this necessary for the best clinical management of hypogonadism?

INTRODUCTION

It is controversial whether or not testing the length of the androgen receptor polymorphism in clinical practice is useful for correct diagnosis and treatment of hypogonadism.

AIM

To describe the molecular and clinical implications of testing the length of the androgen receptor polymorphism for treatment of hypogonadism in both male and female subjects.

METHODS

A systematic Medline search was conducted using several terms related to and including the terms "androgen receptor," "CAG-repeat polymorphism," "male hypogonadism," "female hypogonadism," and "neurodegenerative disease."

MAIN OUTCOME MEASURES

Clinical evidence that demonstrates the importance of CAG repeat number investigation in male and female hypogonadism.

RESULTS

A thorough review of the clinical utility of CAG repeat polymorphism investigation in men and women with hypogonadism is presented.

CONCLUSIONS

The role of AR CAG repeat number investigation in hypogonadism (male and female) is not yet established in the clinical practice. In both sexes, a role during clinical management of hormonal replacement therapies may be hypothesized, but the CAG repeat number's relationship with the presence or absence of hypogonadal symptoms remains unclear. Pharmacogenomic investigations of the AR polymorphism may be a future option to tailor testosterone titration individually and to better identify subjects as potentially more or less responsive to treatments; also, investigation may be important to individually predict beneficial and side effects in special subpopulations, specifically, obese men and postmenopausal women.

Androgen receptor antagonists: a patent review (2008-2011)

INTRODUCTION

Androgen receptor (AR) antagonists are predominantly used as chemical castration to treat prostate cancer (i.e., in conjunction with androgen deprivation therapy (ADT)). Unfortunately, castration-resistant prostate cancer (CRPC) typically develops that is refractory to targeted therapy. Insights into CRPC biology have led to the emergence of a promising clinical candidate MDV3100 (1) and a resurgence in this field. A pipeline of preclinical competitive (C-terminally directed) antagonists was discovered using a variety of innovative screening paradigms. Some inhibit nuclear translocation, selectively downregulate or degrade AR (SARD), antagonize wild-type and escape mutant AR (pan-antagonists) and/or antagonize AR target organs in vivo. Separately, the N-terminal domain has emerged as a promising novel target for noncompetitive antagonists.

AREAS COVERED

AR antagonists whose patents published between 2008 and 2011 are reviewed. Antagonists are organized based on the screening paradigm reported as discussed above.

EXPERT OPINION

Novel mechanisms provide a more informed basis for selecting a competitive antagonist; however, high potency and favorable in vivo properties remain paramount. Noncompetitive antagonists have theoretical advantages suggestive of improved clinical efficacy, but no clinical proof of concept as of yet.

Characteristics of androgenetic alopecia in asian

Androgenetic alopecia (AGA), or pattern hair loss, is a common disorder in Asian men and women, with a reported incidence of up to 73% among general population. There are several descriptions regarding the characteristics of AGA in patients of European descent. Asian patients with AGA have different types of hair loss and family histories from Europeans, which may affect treatment response. Therefore, in this review, prevalence, hair loss patterns, familial factors, androgen receptor gene polymorphisms of Asian AGA patients, and management based on algorithmic guidelines for AGA are discussed. This review may be useful for dermatologists in clinical practice for diagnosing and designing management approaches for Asian patients with AGA.

Toward a mechanistic understanding of how variability in neurobiology shapes individual differences in behavior

Research has begun to identify how variability in brain function contributes to individual differences in complex behavioral traits. Examining variability in molecular signaling pathways with emerging and established methodologies such as pharmacologic fMRI, multimodal PET/fMRI, and hormonal assays are beginning to provide a mechanistic understanding of how individual differences in brain function arise. Against this background, functional genetic polymorphisms are being utilized to understand the origins of variability in signaling pathways as well as to efficiently model how such emergent variability impacts behaviorally relevant brain function and health outcomes. This chapter provides an overview of a research strategy that integrates these complimentary levels of analysis; existing empirical data is used to illustrate the effectiveness of this approach in illuminating the mechanistic neurobiology of individual differences in complex behavioral traits. This chapter also discusses how such efforts can contribute to the identification of predictive risk markers that interact with unique environmental factors to precipitate psychopathology.

ZMIZ1 preferably enhances the transcriptional activity of androgen receptor with short polyglutamine tract

The androgen receptor (AR) is a ligand-induced transcription factor and contains the polyglutamine (polyQ) tracts within its N-terminal transactivation domain. The length of polyQ tracts has been suggested to alter AR transcriptional activity in prostate cancer along with other endocrine and neurologic disorders. Here, we assessed the role of ZMIZ1, an AR co-activator, in regulating the activity of the AR with different lengths of polyQ tracts as ARQ9, ARQ24, and ARQ35 in prostate cancer cells. ZMIZ1, but not ZMIZ2 or ARA70, preferably augments ARQ9 induced androgen-dependent transcription on three different androgen-inducible promoter/reporter vectors. A strong protein-protein interaction between ZMIZ1 and ARQ9 proteins was shown by immunoprecipitation assays. In the presence of ZMIZ1, the N and C-terminal interaction of the ARQ9 was more pronounced than ARQ24 and ARQ35. Both Brg1 and BAF57, the components of SWI/SNF complexes, were shown to be involved in the enhancement of ZMIZ1 on AR activity. Using the chromatin immunoprecipitation assays (ChIP), we further demonstrated a strong recruitment of ZMIZ1 by ARQ9 on the promoter of the prostate specific antigen (PSA) gene. These results demonstrate a novel regulatory role of ZMIZ1 in modulating the polyQ tract length of AR in prostate cancer cells.

Studying the genetic predisposing factors in the pathogenesis of acne vulgaris

Acne is one of the most common dermatologic diseases in the developed regions of the world, affecting a large percentage of the population. Despite the great improvement in the number and quality of studies of the molecular etiology of this disease in the past 3 decades, the detailed molecular pathogenesis and the cause of the large individual variations in severity of skin symptoms remain unknown. The roles of genetic inheritance and special genetic susceptibility and protective factors have been suggested for over 100 years, but their identification and determination started only in the 1990s. To date, only a small number of genetic polymorphisms affecting the expression and/or function of a handful of genes have been investigated. This review surveys the major findings of the classic and molecular genetic studies that have been conducted in this field, draws conclusions, and indicates how the available data help our current understanding of the pathogenesis of this common skin disease.

Predictors of pilosebaceous unit responsiveness to testosterone therapy in patients with hypogonadotrophic hypogonadism

Testosterone replacement therapy is the mainstay of treatment in male patients with isolated hypogonadotrophic hypogonadism (HH) to achieve virilisation. However, responsiveness of pilosebaceous unit (PSU) to testosterone replacement therapy in these patients is quite variable. Androgen action is inversely proportional to the number of CAG repeats in exon 1 of androgen receptor gene; therefore, we hypothesised that CAG repeat length contributes to testosterone responsiveness in patients with HH. The CAG repeat length in 21 well-virilised men (hair score > 30, responders) and 25 poorly virilised men (hair score ≤ 30, non-responders) with HH on optimal testosterone replacement therapy at least for a period of 1 year was analysed. Serum LH, FSH, testosterone and 17 β oestradiol were estimated. Polymerase chain reaction (PCR) amplification of exon 1 of androgen receptor gene was performed from genomic DNA, and these PCR-amplified products were sequenced for the number of CAG repeats. The difference between number of CAG repeats in responders and non-responders was statistically significant (19.19 ± 3.25 and 22.24 ± 2.65, P = 0.001) and showed a strong negative correlation with total body hair score (r = -0.538 and P = 0.0001). In conclusion, these results suggest that the number of CAG repeats influences the responsiveness of PSU to testosterone treatment in patients with HH.

Androgen receptor gene polymorphisms are associated with aggression in Japanese Akita Inu

We tested for an association between variable number of tandem repeats in the canine androgen receptor (AR) gene and personality differences in Japanese Akita Inu dogs. The polymorphic trinucleotide (CAG) repeat region coding for glutamine in exon 1 of the AR gene was genotyped using genomic DNA obtained from 171 dogs. Three alleles (23, 24 and 26 repeats) were detected, and the allele frequency differed with the coat colour. We assessed the personality profiles of 100 fawn-coloured dogs (54 males and 46 females) based on a questionnaire answered by each dog's owner. The questionnaire consisted of five sub-scales (sociability, playfulness, neuroticism, aggressiveness, distractibility), and the psychometric properties were acceptable based upon internal consistency of the subscales. We found that male dogs with a short allele conferring increased AR function had higher aggressiveness scores than male dogs with longer alleles. By contrast, no evidence was found for a relationship between AR gene variants and personality in females. To our knowledge, our findings provide the first evidence of polymorphism in the AR gene being associated with canine aggression.

Association of androgen receptor CAG repeat polymorphism with VO₂max response to hypoxic training in North China Han men

The purposes of this study were to investigate the distribution characteristics of CAG repeat polymorphism in exon 1 of androgen receptor gene and the association of CAG polymorphism with VO₂max response to hypoxic training in North China Han men. Sixty-five healthy young men completed a 30-day HiHiLo training (living high, exercise high and training low) in a simulated normobaric hypoxic environment. All subjects slept in 14.3-14.8% O₂ concentration, and participated in hypoxic training three times a week in 15.4% O₂ concentration. VO₂max (peak oxygen consumption) and body weight were measured before and after hypoxic training. A total of 15 repeat alleles were observed by CAG genotype analyze, in which (CAG)22 was most common. When using 21 and 22 alleles, respectively, as cut-off points, we found that the baseline body weight of two shorter genotype groups was significantly lower than that of longer ones, and that the ΔVO₂max and ΔrVO₂max (Δrelative value of VO₂max) of two shorter genotype groups were significantly higher than those of longer ones after hypoxic training. These findings indicated that AR CAG repeat polymorphism was associated with the exercise performance after simulated normobaric hypoxic HiHiLo training in North China Han men, and that the shorter genotypes had a better individual response to hypoxic training.

Role of the androgen receptor CAG repeat polymorphism in prostate cancer, and spinal and bulbar muscular atrophy

Androgens are involved in the development of several tissues, including prostate, skeletal muscle, bone marrow, hair follicles, and brain. Most of the biological effects of the androgens are mediated through an intracellular transcription factor, the androgen receptor (AR) at the level of gene regulation. Several types of mutations in the AR gene have been linked to endocrine dysfunctions. The expansion of CAG codon repeat, coding for a polyglutamine (PolyQ) tract in the N-terminal domain is one such mutation. The polyQ chain length impacts AR's ability to interact with critical coregulators, which in turn modulates its transcriptional efficacy. Pathologic manifestations of variations in polyQ chain length have been associated with prostate cancer susceptibility, and the Spinal and Bulbar Muscular Atrophy (SBMA), a neurodegenerative disease. In this review article, we discuss multiple aspects of the role of polyQ chain length in the actions of the AR, their importance in prostate cancer development and progression, and SBMA with an aim to understand the underlying mechanisms involved in these diseases, which can be targeted for future therapeutic approaches.

Analysis of interdomain interactions of the androgen receptor

High-affinity binding of testosterone or dihydrotestosterone to the androgen receptor (AR) triggers the androgen-dependent AR NH2- and carboxyl-terminal (N/C) interaction between the AR NH2-terminal FXXLF motif and the activation function 2 (AF2) hydrophobic binding surface in the ligand-binding domain. The functional importance of the AR N/C interaction is supported by naturally occurring loss-of-function AR AF2 mutations where AR retains high-affinity androgen binding but is defective in AR FXXLF motif binding. Ligands with agonist activity in vivo such as testosterone, dihydrotestosterone, and the synthetic anabolic steroids induce the AR N/C interaction and increase AR transcriptional activity in part by slowing the dissociation rate of bound ligand and stabilizing AR against degradation. AR ligand-binding domain competitive antagonists inhibit the agonist-dependent AR N/C interaction. Although the human AR N/C interaction is important for transcriptional activity, it has an inhibitory effect on transcriptional activity from AF2 by competing for p160 coactivator LXXLL motif binding. The primate-specific AR coregulatory protein, melanoma antigen gene protein-A11 (MAGE-A11), modulates the AR N/C interaction through a direct interaction with the AR FXXLF motif. Inhibition of AF2 transcriptional activity by the AR N/C interaction is relieved by AR FXXLF motif binding to the F-box region of MAGE-11. Described here are methods to measure the androgen-dependent AR N/C interdomain interaction and the influence of transcriptional coregulators.

Salivary testosterone and a trinucleotide (CAG) length polymorphism in the androgen receptor gene predict amygdala reactivity in men

In studies employing functional magnetic resonance imaging (fMRI), reactivity of the amygdala to threat-related sensory cues (viz., facial displays of negative emotion) has been found to correlate positively with interindividual variability in testosterone levels of women and young men and to increase on acute administration of exogenous testosterone. Many of the biological actions of testosterone are mediated by intracellular androgen receptors (ARs), which exert transcriptional control of androgen-dependent genes and are expressed in various regions of the brain, including the amygdala. Transactivation potential of the AR decreases (yielding relative androgen insensitivity) with expansion a polyglutamine stretch in the N-terminal domain of the AR protein, as encoded by a trinucleotide (CAG) repeat polymorphism in exon 1 of the X-chromosome AR gene. Here we examined whether amygdala reactivity to threat-related facial expressions (fear, anger) differs as a function of AR CAG length variation and endogenous (salivary) testosterone in a mid-life sample of 41 healthy men (mean age=45.6 years, range: 34-54 years; CAG repeats, range: 19-29). Testosterone correlated inversely with participant age (r=-0.39, p=0.012) and positively with number of CAG repeats (r=0.45, p=0.003). In partial correlations adjusted for testosterone level, reactivity in the ventral amygdala was lowest among men with largest number of CAG repeats. This inverse association was seen in both the right (r(p)=-0.34, p<0.05) and left (r(p)=-0.32, p<0.05) hemisphere. Activation of dorsal amygdala, correlated positively with individual differences in salivary testosterone, also in right (r=0.40, p<0.02) and left (r=0.32, p<0.05) hemisphere, but was not affected by number of CAG repeats. Hence, androgenic influences on threat-related reactivity in the ventral amygdala may be moderated partially by CAG length variation in the AR gene. Because individual differences in salivary testosterone also predicted dorsal amygdala reactivity and did so independently of CAG repeats, it is suggested that androgenic influences within this anatomically distinct region may be mediated, in part, by non-genomic or AR-independent mechanisms.

Functional AR signaling is evident in an in vitro mouse follicle culture bioassay that encompasses most stages of folliculogenesis

Androgens have distinct physiological functions within the ovary. The biological action of androgens is primarily exerted through transcriptional regulation by the nuclear androgen receptor (AR), but the molecular cascades governed by AR remain largely unknown. At present, there is imminent concern that environmental man-made chemicals with antiandrogenic properties, among others, are capable of modulating hormonal responses, thereby interfering with normal physiological processes that are critical to fertility. In the present study, we aimed to further characterize a standardized and reproducible follicle culture system in terms of AR expression during in vitro folliculogenesis to be able to use it as a bioassay to study effects of antiandrogens on follicular and oocyte growth, steroid secretion profile, and oocyte meiotic maturation capacity. Immunohistochemical analysis revealed that cytoplasmic AR protein was translocated to the nucleus of granulosa and theca cells in response to endogenous androgen production in theca cells during preantral follicular development. During the antral phase in vitro, AR was differentially expressed in mural and cumulus cells, implying an oocyte-mediated regulation. Treatment of follicles with hydroxyflutamide or bicalutamide, two model antiandrogenic compounds, resulted in reduced follicular growth during the preantral phase, altered steroidogenic environment, and arrest in oocyte meiotic maturation in response to human chorionic gonadotropin. Androgen receptor expression in the culture model corresponded well to what is described in vivo, and this system revealed several ovarian functions targeted by AR antagonists that can be further investigated using more in-depth molecular techniques.

Advances in male contraception

Despite significant advances in contraceptive options for women over the last 50 yr, world population continues to grow rapidly. Scientists and activists alike point to the devastating environmental impacts that population pressures have caused, including global warming from the developed world and hunger and disease in less developed areas. Moreover, almost half of all pregnancies are still unwanted or unplanned. Clearly, there is a need for expanded, reversible, contraceptive options. Multicultural surveys demonstrate the willingness of men to participate in contraception and their female partners to trust them to do so. Notwithstanding their paucity of options, male methods including vasectomy and condoms account for almost one third of contraceptive use in the United States and other countries. Recent international clinical research efforts have demonstrated high efficacy rates (90-95%) for hormonally based male contraceptives. Current barriers to expanded use include limited delivery methods and perceived regulatory obstacles, which stymie introduction to the marketplace. However, advances in oral and injectable androgen delivery are cause for optimism that these hurdles may be overcome. Nonhormonal methods, such as compounds that target sperm motility, are attractive in their theoretical promise of specificity for the reproductive tract. Gene and protein array technologies continue to identify potential targets for this approach. Such nonhormonal agents will likely reach clinical trials in the near future. Great strides have been made in understanding male reproductive physiology; the combined efforts of scientists, clinicians, industry and governmental funding agencies could make an effective, reversible, male contraceptive an option for family planning over the next decade.

Androgen receptor functions in male and female physiology

The biological actions of androgens are mediated by transcriptional control of target genes through binding to the androgen receptor (AR). The AR belongs to the nuclear receptor superfamily and acts as a ligand-inducible transcriptional factor. Androgens/AR system is thought to be central to male physiology and behaviors to the development of clinical pathology. The physiological importance of AR function currently recognized in female reproduction also has been verified in mouse genetic model. Here we review functions of AR in male and female physiology as revealed by mice lacking AR.

Androgen receptor variants and prostate cancer in humanized AR mice

Androgen, acting via the androgen receptor (AR), is central to male development, differentiation and hormone-dependent diseases such as prostate cancer. AR is actively involved in the initiation of prostate cancer, the transition to androgen independence, and many mechanisms of resistance to therapy. To examine genetic variation of AR in cancer, we created mice by germ-line gene targeting in which human AR sequence replaces that of the mouse. Since shorter length of a polymorphic N-terminal glutamine (Q) tract has been linked to prostate cancer risk, we introduced alleles with 12, 21 or 48 Qs to test this association. The three "humanized" AR mouse strains (h/mAR) are normal physiologically, as well as by cellular and molecular criteria, although slight differences are detected in AR target gene expression, correlating inversely with Q tract length. However, distinct allele-dependent differences in tumorigenesis are evident when these mice are crossed to a transgenic prostate cancer model. Remarkably, Q tract variation also differentially impacts disease progression following androgen depletion. This finding emphasizes the importance of AR function in androgen-independent as well as androgen-dependent disease. These mice provide a novel genetic paradigm in which to dissect opposing functions of AR in tumor suppression versus oncogenesis.

Androgen receptor function in folliculogenesis and its clinical implication in premature ovarian failure

The action of estrogen in the female reproductive organs is well known in terms of the expression pattern and gene regulation of the estrogen receptor (ER). The significance of ERs in female reproduction is undisputed. The role of the androgen receptor (AR) is less clear. Clinical hyperandrogenism, a typical feature of polycystic ovary syndrome (PCOS), highlights pathological androgen production by the ovary. By contrast, the physiological impact of androgen action in female reproductive organs remains elusive. Androgens affect folliculogenesis in a variety of experimental approaches and ARs are expressed in developing follicles. Recent observations have discovered that inactivation of ARs in female mice results in premature ovarian failure (POF), indicating that normal folliculogenesis requires AR-mediated androgen action. Moreover, these results imply that POF might be caused by impairment of AR-mediated androgen action.

Steroid hormone receptor gene polymorphisms and osteoporosis: a pharmacogenomic review

Osteoporosis is a common skeletal disorder with a strong genetic component. In recent years, significant progress has been made in understanding the genetic basis of osteoporosis. Given the biological significance of signalling through steroid hormone receptors, bone biology and calcium homeostasis, alleles of steroid hormone receptor genes have been postulated to contribute to the well-documented genetic predisposition to osteoporosis; and in different studies, these alleles have been associated with variation in bone mass and fracture risk. Even though results are still conflicting and the molecular mechanisms by which these polymorphisms influence receptor activity remain, in part, to be investigated, an additional important issue is represented by potential pharmacogenomic (the investigation of variations of DNA or RNA characteristics as related to drug response) or pharmacogenetic (the influence of variations of DNA sequence on drug response) implications. In fact, steroid hormone receptors actually mediate the action of several compounds known to positively or negatively affect bone homeostasis, such as vitamin D, estrogen and glucocorticoids. This review analyses major pharmacogenetic studies of polymorphisms in steroid hormone receptor genes.

Replacing the mouse androgen receptor with human alleles demonstrates glutamine tract length-dependent effects on physiology and tumorigenesis in mice

Polymorphism in the length of the N-terminal glutamine (Q) tract in the human androgen receptor (AR) has been implicated in affecting aspects of male health ranging from fertility to cancer. Extreme expansion of the tract underlies Kennedy disease, and in vitro the AR Q tract length correlates inversely with transactivation capacity. However, whether normal variation influences physiology or the etiology of disease has been controversial. To assess directly the functional significance of Q tract variation, we converted the mouse AR to the human sequence by germline gene targeting, introducing alleles with 12, 21, or 48 glutamines. These three "humanized" AR (h/mAR) mouse lines were grossly normal in growth, behavior, fertility, and reproductive tract morphology. Phenotypic analysis revealed traits that varied subtly with Q tract length, including body fat amount and, more notably, seminal vesicle weight. Upon molecular analysis, tissue-specific differences in AR levels and target gene expression were detected between mouse lines. In the prostate, probasin, Nkx3.1, and clusterin mRNAs trended in directions predicted for inverse correlation of Q tract length with AR activation. Remarkably, when crossed with transgenic adenocarcinoma of mouse prostate (TRAMP) mice, striking genotype-dependent differences in prostate cancer initiation and progression were revealed. This link between Q tract length and prostate cancer, likely due to differential activation of AR targets, corroborates human epidemiological studies. This h/mAR allelic series in a homogeneous mouse genetic background allows examination of numerous physiological traits for Q tract influences and provides an animal model to test novel drugs targeted specifically to human AR.

Comparison of androgen receptor CAG and GGN repeat length polymorphism in humans and apes

Two polymorphic trinucleotide repeats of human androgen receptor gene (hAR), CAG and GGN which encode glutamine and glycine, have been shown to be associated with human diseases. The number of repeats ranges from 8 to 35 for the CAG and from 10 to 30 for the GGN in human populations. Longer CAG repeats are associated with reduced hAR transcriptional activity, spinal bulbar muscular atrophy and lower cognitive function in older men, whereas shorter CAG repeats are associated with increased risk of prostate cancer and infertility in men. The functional roles of the CAG and GGN repeats have not been clarified. In order to compare the sequence of the CAG and GGN regions in apes, we analyzed 57 chimpanzees, 18 gorillas, 20 orangutans, 16 agile gibbons, and 17 siamangs by PCR and electrophoresis. Two bonobos and one long-tailed macaque were also sequenced and the sequences of all species were aligned, respectively, with one human registered sequence. Seventeen different alleles (4, 7, 8, 9, 12, 14, 15, and 17-26 repeats) and 11 alleles (11-14 and 16-22 repeats) were detected at the CAG and the GGN loci, respectively. Although the repeat tract was conserved among apes, chimpanzees had alleles with a wide range of repeat lengths: (CAG)(14-26) and (GGN)(14-22). Gorillas were less polymorphic with the (CAG)(8) and (GGN)(19) alleles being most common, and orangutans exhibited monomorphic (CAG)(11) and (GGN)(22) alleles. On the other hand, agile gibbons and siamangs had the shortest (CAG)(4) allele, but showed variable length of GGN repeats (11-13 in agile gibbons and 16-21 in siamangs). In chimpanzees, frequent haplotypes consisting of short CAG repeats and long GGN repeats or vice versa was observed as in humans.

Influence of Number of CAG Repeats on Local Control in the RTOG 86-10 Protocol

OBJECTIVES

The number of CAG repeats on the androgen receptor (AR) gene is inversely proportional to transcriptional activity. The purpose of this study was to determine if short-term androgen deprivation therapy (RT + HT) can improve outcome in patients with tumors with short CAG repeats (<19).

MATERIALS AND METHODS

Prostate cancer patients were randomized to receive either radiotherapy (RT) alone or (RT + HT) in the RTOG 86-10 study. CAG repeats were measured in 94 tumor specimens (21%; test cohort) of the 456 (parent cohort) analyzable cases. AR flow cytometry measurements were done on 13 patients. The effect on local failure (LF), distant metastases (DM), prostate cancer survival (PSS), and overall survival (OS) was studied.

RESULTS

Pretreatment characteristics and assigned treatment arm were not significantly different between the parent and test groups except for a significantly higher risk of death (P = 0.049) in the test group. The median CAG repeat was 19. There were no significant differences in stage, or Gleason score between high (19 or greater) and low CAG (<19) patients within each treatment group. Number of CAG repeats alone did not significantly influence LF, DM, PSS, and OS. However, when the CAG repeat outcome was studied in conjunction with androgen deprivation therapy, patients with CAG <19 who received H + RT had improved local control as compared with patients who received RT alone (P = 0.026, 5-year rates 4.6% versus 36.4%) and improved local control over patients with CAG > or =19 that received H + RT (P = 0.028).

CONCLUSIONS

Patients with short CAG repeats show a local control benefit with short-term androgen deprivation therapy, but no improvement in survival.

Genetic Analysis of a Family with 46, XY “Female” Associated with Infertility

Genetic analysis of a family with 46,XY "female" associated with infertility was performed using the conventional G-banding and gene mutation screening. The karyotypes of the two female patients were 46,XY and those of their parents were normal. The mutation screenings in sex-determining region Y (SRY) gene and androgen receptor (AR) gene were carried out. No mutation has been found in the whole coding sequence of SRY gene. The mutation of codon 840 CGT (arginine) to CAT (histidine) of AR gene led to the infertility in the patients. The patients showed androgen insensitivity. The clinical phenotype of theirs presented more deleteriously than and different from the one reported before, though they had the same mutation of codon 840 CGT (arginine) to CAT (histidine) of AR gene, which was very different from the mutation of 840 CGT (arginine) to TGT (cysteine) at the same codon.

Human expanded polyglutamine androgen receptor mutants in neurodegeneration as a novel ligand target

Androgen receptor (AR) plays key roles in various biological events, including pathological processes such as prostate cancer, androgen-insensitive syndrome, and spinal and bulbar muscular atrophy (SBMA). SBMA is caused by mutation of the expanded polyglutamine (polyQ) stretches in the AR gene. Recently, we established a Drosophila SBMA model that expresses the expanded polyQ hAR mutant in eyes, which monitors neurodegeneration as a rough eye phenotype. In addition, we showed that androgen binding to the mutant hAR causes structural alterations, leading to the onset of neurodegeneration in the fly eyes. In the present study, we examined whether the ligand-induced neurodegeneration via the hAR mutant is coupled with the known ligand-induced transactivation function of hAR. By testing several known AR antagonists and several of their structure-related compounds, we unexpectedly found that none of the AR ligands antagonized the hAR mutant neurodegeneration function, and surprisingly, compound 4-(4,4-dimethyl-2,5-dioxo-1-imidazolidinyl)-2-trifluoromethylbenzonitrile (RU56279) was more potent in inducing neurodegeneration. However, in vitro and in vivo mammalian assays showed that RU56279 exhibited the expected antagonistic activity with the same potency as those of the other compounds. Thus, these findings suggest the presence of a novel ligand-induced function of the polyQ hAR mutant in neurodegeneration that could not be prevented by known antagonists for the hAR transactivation function.

Sex steroid-related genes and male-to-female transsexualism

Transsexualism is characterised by lifelong discomfort with the assigned sex and a strong identification with the opposite sex. The cause of transsexualism is unknown, but it has been suggested that an aberration in the early sexual differentiation of various brain structures may be involved. Animal experiments have revealed that the sexual differentiation of the brain is mainly due to an influence of testosterone, acting both via androgen receptors (ARs) and--after aromatase-catalyzed conversion to estradiol--via estrogen receptors (ERs). The present study examined the possible importance of three polymorphisms and their pairwise interactions for the development of male-to-female transsexualism: a CAG repeat sequence in the first exon of the AR gene, a tetra nucleotide repeat polymorphism in intron 4 of the aromatase gene, and a CA repeat polymorphism in intron 5 of the ERbeta gene. Subjects were 29 Caucasian male-to-female transsexuals and 229 healthy male controls. Transsexuals differed from controls with respect to the mean length of the ERbeta repeat polymorphism, but not with respect to the length of the other two studied polymorphisms. However, binary logistic regression analysis revealed significant partial effects for all three polymorphisms, as well as for the interaction between the AR and aromatase gene polymorphisms, on the risk of developing transsexualism. Given the small number of transsexuals in the study, the results should be interpreted with the utmost caution. Further study of the putative role of these and other sex steroid-related genes for the development of transsexualism may, however, be worthwhile.

Study of Androgen Receptor Functions by Genetic Models

Androgens exert most of their biological activities through binding to the androgen receptor (AR). The AR belongs to the nuclear receptor superfamily and acts as a ligand-inducible transcriptional factor. AR dysfunction causes a diverse range of clinical conditions, such as testicular mutation (Tfm) syndrome, prostate cancer, and spinal and bulbar muscular atrophy (SBMA). However, the molecular basis of the AR function underlying these AR-related disorders remains largely unknown due to the lack of stable genetic models. Here we review recent results of our studies into genetic models of the loss of AR function in mice and the gain of AR function in Drosophila.

X-chromosome inactivation patterns and androgen receptor functionality influence phenotype and social characteristics as well as pharmacogenetics of testosterone therapy in Klinefelter patients

Klinefelter syndrome is characterized by a vast range of phenotypes related to androgen effects. Testosterone (T) acts via the X-linked androgen receptor gene carrying the CAG repeat (CAGn) polymorphism, the length of which is inversely associated with androgen action and might account for the marked variation in phenotypes. In 77 newly diagnosed and untreated Klinefelter patients with a 47,XXY karyotype we assessed phenotype and social traits in relation to X-weighted biallelic CAGn length using X-chromosome inactivation analysis after digestion of leukocyte DNA with methylation-sensitive HpaII. Forty-eight men were hypogonadal and received T substitution therapy; in these, pharmacogenetic effects were investigated. The shorter CAGn allele was preferentially inactive. CAGn length was positively associated with body height. Bone density and the relation of arm span to body height were inversely related to CAGn length. The presence of long CAGn was predictive for gynecomastia and smaller testes, whereas short CAGn were associated with a stable partnership and professions requiring higher standards of education also when corrected for family background. There was a trend for men with longer CAGn to be diagnosed earlier in life. Under T substitution, men with shorter CAGn exhibited a more profound suppression of LH levels, augmented prostate growth, and higher hemoglobin concentrations. A significant genotype-phenotype association exists in Klinefelter patients: androgen effects on appearance and social characteristics are modulated by the androgen receptor CAGn polymorphism. The effects of T substitution are pharmacogenetically modified. This finding is magnified by preferential inactivation of the more functional short CAGn allele.

Intranuclear organization and function of the androgen receptor

We have entered an exciting era for androgen-receptor (AR) research that should provide a detailed description of how the AR functions as a ligand-regulated transcription factor. That AR activity is regulated by subcellular compartmentalization was first established a decade ago with the finding that binding of androgen to the AR induces its translocation from the cytoplasm to the nucleus. The contribution of compartmentalization to AR activity is, however, likely to extend beyond simple delivery to the nucleus. Defects in AR and coregulator compartmentalization in the nucleus have been demonstrated in prostate cancer, androgen-insensitivity syndrome, and spinal and bulbar muscular atrophy. A complete understanding of AR function and dysfunction in disease requires integrating transcription with the spatial and temporal regulation imposed by subnuclear organization and nuclear transport.

How Strong Is the Association Between CAG and GGN Repeat Length Polymorphisms in the Androgen Receptor Gene and Prostate Cancer Risk?

Objective: Although narrative reviews have suggested an association between (CAG)n and (GGN)n polymorphisms in the AR gene and prostate cancer, it has never been quantified systematically. The purpose of this meta-analysis was to provide relative and absolute quantitative summary estimates with sufficient power.

Method: Publications were identified through database searches for epidemiologic studies published until February 2004. For each study, mean differences in repeat length between cases and controls were calculated as well as continuous odds ratios (OR) per one CAG or GGN repeat decrement and discrete ORs to compare prostate cancer risk in men with short CAG repeats (≤21 repeats) versus long CAG repeats (&gt;21 repeats) and short GGN repeats (≤16 repeats) versus long GGN repeats (&gt;16 repeats). The study-specific estimates were combined by random effects metaregression analyses.

Results: Nineteen case-control studies were included in this review comprising a total of 4,274 cases and 5,275 controls. Prostate cancer cases had on average 0.26 fewer CAG repeats and 0.09 fewer GGN repeats than controls. The continuous ORs of prostate cancer per one repeat decrement were 1.02 and 1.01 for CAG and GGN repeats, respectively. The summary discrete OR (95% confidence interval) were 1.19 (1.07-1.31) and 1.31 (1.06-1.61) for CAG and GGN repeat polymorphisms, respectively.

Conclusion: Although the presence of shorter repeats seemed to be modestly associated with prostate cancer risk, the absolute difference in number of repeats between cases and controls is &lt;1 repeat. We question whether such a small difference is enough to yield measurable biological impact in prostate carcinogenesis.

The androgen receptor mRNA

Androgens (testosterone), acting via the androgen receptor (AR) a nuclear transcription factor, regulate male sexual development and body composition. In addition, AR expression plays an important role in the proliferation of human prostate cancer and confers a better prognosis in breast cancer. AR mRNA stability is central to the regulation of AR expression in prostate and breast cancer cells, and recent studies have demonstrated binding by members of the ELAV/Hu and poly(C) RNA-binding protein families to a highly conserved UC-rich element in the 3'-untranslated region of AR mRNA, with functional impact on AR protein expression. Remarkably, a CAG trinucleotide repeat in exon 1 of the AR, the length of which has been linked to prostate cancer survival, is also a target for multiple RNA-binding proteins from a variety of human and murine tissues. In this review, we will detail the current knowledge of the mechanisms involved in regulating AR mRNA stability, the nature, potential role and structural biology of several novel AR mRNA-protein interactions, and the implications for novel therapeutics in human prostate cancer.