Androgen insensitivity syndrome: do trinucleotide repeats in androgen receptor gene have any role?

AIM: To investigate the role of CAG and GGN repeats as genetic background affecting androgen insensitivity syndrome (AIS) phenotype. METHODS: We analyzed lengths of androgen receptor (AR)-CAG and GGN repeats in 69 AIS cases, along with 136 unrelated normal male individuals. The lengths of repeats were analyzed using polymerase chain reaction (PCR) amplification followed by allelic genotyping to determine allele length. RESULTS: Our study revealed significantly shorter mean lengths of CAG repeats in patients (mean 18.25 repeats, range 14-26 repeats) in comparison to the controls (mean 22.57 repeats, range 12-39 repeats) (two-tailed P < 0.0001). GGN repeats, however, did not differ significantly between patients (mean 21.48 repeats) and controls (mean 21.21 repeats) (two-tailed P = 0.474). Among patients' groups, the mean number of CAG repeats in partial androgen insensitivity cases (mean 15.83 repeats) was significantly less than in complete androgen insensitivity cases (mean 19.46 repeats) (two-tailed P < 0.0001). CONCLUSION: The findings suggest that shorter lengths of repeats in the AR gene might act as low penetrance genetic background in varying manifestation of androgen insensitivity.     

CAG repeat expansion in the androgen receptor gene is not associated with male infertility in Indian populations

CAG repeat expansion in exon 1 of the androgen receptor (AR) gene has been reported to be associated with male infertility in some but not all populations. Until now, studies have not been carried out to examine this among Indian populations. For the first time, we have analyzed the CAG repeat motif in the AR gene in 280 men with azoospermia and in 201 men with normal fertility. The mean number of CAG repeats in the AR gene of men with azoospermia was 21.7 +/- 0.18, with a high incidence of repeat number 22. Among fertile-control men, the mean number of CAG repeats was 22.4 +/- 0.19, with a predominance of repeat number 23. The highest number of CAG repeats (32) was found with low frequency in both fertile and azoospermic groups. Comparison of fertile men and those with azoospermia on the basis of CAG repeats revealed that the number of CAG repeats in both groups were similar, as revealed with a paired t test (t = 0.04; P =.967). Expansion of the CAG repeat in the AR gene is therefore not associated with male infertility in Indian populations. This suggests that what is true for one population may not be true for other populations.     

Androgen receptor gene haplotype is associated with male infertility

The purpose of the current study was to evaluate the importance of androgen receptor ( AR ) gene haplotypes and polymorphic CAG/GGN microsatellites in the aetiology of male infertility. We genotyped six haplotype-tagging single nucleotide polymorphisms and CAG/GGN microsatellites of the AR gene in 112 infertile and 212 control Estonian men. A total of 13 AR haplotypes (HAP1–13) were identified, among which HAP4 was found to confer increased risk for male infertility (OR = 5.15, 95% CI = 1.75–15.15, p  = 0.003). However, infertile patients and controls had similar lengths and distributions of both AR CAG (mean ± SD number of repeats 21.1 ± 2.5 vs . 21.2 ± 2.3, respectively) and GGN (mean ± SD number of repeats 22.5 ± 1.5 vs . 22.4 ± 1.9, respectively) repeats. In addition, HAP2 was associated with more CAG repeats ( r  = 1.17, p  = 0.033) and HAP3 with fewer CAG repeats ( r  = −2.93, p  < 0.001) than the major haplotype HAP1. HAP3 and HAP4 were associated with more GGN repeats ( r  = 1.35, p  = 0.001 and r  = 1.36, p  = 0.002, respectively) than HAP1. In conclusion, our results implicated the AR -HAP4 gene haplotype in increased risk for male infertility, while no association was found between AR CAG/GGN microsatellites and impaired spermatogenesis.     

CAG repeat length in androgen receptor gene and male infertility in Egyptian patients

The CAG repeat and its association with infertility has been debatable. Therefore, this study was planned to assess the distribution of CAG repeat expansion in Egyptian patients and to investigate its association with male infertility. Forty-five infertile men were eligible for the study in addition to 20 aged-matched fertile males as control. Semen analysis, scrotal sonography, assay of serum testosterone, follicle-stimulating hormone (FSH) and luteinising hormone (LH), and determination of the CAG repeat number within exon 1 of the androgen receptor (AR) gene were carried out. Statistically significant difference was found between infertile and control groups regarding sperm count, sperm motility, serum FSH level and CAG repeats (P < 0.05); statistically insignificant difference for the CAG repeats (P = 1.0) was found between oligozoospermic and asthenospermic groups; negative correlation was found between CAG repeat length and sperm count, and a positive correlation was found between CAG repeat length and serum FSH (P < 0.05). Our results validate the concept that long stretches of CAG repeat may be associated with lower AR function with derangement of sperm production, and this may contribute to male infertility in Egyptian men.     

Association of oestrogen receptor alpha polymorphisms and androgen receptor CAG trinucleotide repeats with male infertility: a study in 109 Greek infertile men

This study was performed to examine the contribution of genetic polymorphism of oestrogen and androgen receptor (AR) genes in male infertility. We have studied in total 173 Greek men, 109 infertile patients and 64 controls (group A). Patients were divided in to three subgroups: group B (n=29) with idiopathic moderate oligospermia, group C (n=42) with azoospermia or idiopathic severe oligospermia and group D (n=38) with azoospermia or oligospermia of various known aetiologies. All patients and controls were genotyped for two polymorphisms of the oestrogen receptor alpha (ERalpha) gene and also for the (CAG)n repeat length polymorphism of the X-linked androgen receptor (AR)gene. The control group had statistically significant difference from group C regarding the XbaI polymorphism of ERalpha gene. Despite the fact that we did not observe any statistically significant differences in the mean and range of the CAG repeat number, the frequency of the higher repeats of the nucleotide repeat sequence (CAG)n of the AR gene was 2-4 times higher in groups B and C compared with the control group A. Our results indicate that both ERalpha and AR gene play significant role in male fertility. It is possible that a synergy may exist between unfavourable genotypes of these two genes in male infertility.     

Androgen receptor gene polymorphisms and the fat-bone axis in young men and women

Androgen receptor (AR) CAG(n) (polyglutamine) and GGN(n) (polyglycine) repeat polymorphisms determine part of the androgenic effect and may influence adiposity. The association of fat mass, and its regional distribution, with the AR CAG(n) and GGN(n) polymorphisms was studied in 319 and 78 physically active nonsmoker men and women (mean ± SD: 28.3 ± 7.6 and 24.8 ± 6.2 years old, respectively). The length of CAG and GGN repeats was determined by polymerase chain reaction and fragment analysis, and confirmed by DNA sequencing of selected samples. Men were grouped as CAG short (CAG(S)) if harboring repeat lengths ≤ 21, the rest as CAG long (CAG(L)). The corresponding cutoff CAG number for women was 22. GGN was considered short (GGN(S)) if GGN ≤ 23, the rest as GGN long (GGN(L)). No association between AR polymorphisms and adiposity or the hormonal variables was observed in men. Neither was there a difference in the studied variables between men harboring CAG(L) + GGN(L),CAG(S) + GGN(S),CAG(S) + GGN(L), and CAG(L) + GGN(S) combinations. However, in women, GGN(n) was linearly related to the percentage of body fat (r = 0.30, P < .05), the percentage of fat in the trunk (r = 0.28, P < .05), serum leptin concentration (r = 0.40, P < .05), and serum osteocalcin concentration (r = 0.32, P < .05). In men, free testosterone was inversely associated with adiposity and serum leptin concentration, and positively with osteocalcin, even after accounting for differences in CAG(n), GGN(n), or both. In summary, this study shows that the AR repeat polymorphism has little influence on absolute and relative fat mass or its regional distribution in physically active men. In young women, GGN length is positively associated with adiposity, leptin, and osteocalcin.     

Polymorphic repeats in the androgen receptor gene in high-risk sibships

BACKGROUND: Genetic susceptibility may explain some familial clusters of prostate cancer. The polymorphic androgen receptor (AR) gene, which mediates androgen activity in the prostate, is a candidate gene that may influence predisposition to the disease. METHODS: We analyzed the polymorphic (CAG)n and (GGN)n repeats within the AR gene in men from 51 high-risk prostate cancer sibships, which included at least one affected and one unaffected man (n = 210). We compared repeat lengths of men with prostate cancer (n = 140) to their brothers (n = 70) without disease, stratified by median age at diagnosis of affected men within each sibship. Conditional logistic regression was used to compute odds ratios (OR) and 95% confidence intervals to evaluate associations between prostate cancer and repeat length. RESULTS: The OR for prostate cancer associated with short (CAG)n repeats (< 22) compared to longer repeats (> or =22) was 1.13 (95% CI 0.5-2.4) overall, but was higher in sibships with a median age of <66 years at diagnosis (OR = 1.72, 95% CI 0.5-6.0). The (GGN)n array also was not associated with prostate cancer in general. However, in older men (> or = 66 years), there was a modest elevation in risk (OR = 1.56, 95% CI 0.6-4.1) among those with short repeats (GGN of < or =16). Men with both a short (CAG)n (< 22) and a short (GGN)n (< or =16) array were not at higher risk (OR = 1.06) compared to men with two long repeats [(CAG)n > or =22 and (GGN)n >16)]. CONCLUSIONS: These results suggest that the (CAG)n and (GGN)n repeats in the AR gene do not play a major role in familial prostate cancer.     

雄激素受体基因CAG重复多态性与男性不育关系的Meta分析

目的:采用Meta分析系统评价雄激素受体(AR)基因CAG串联重复多态性与男性不育的关系。方法:检索Medline、CBM等数据库中有关AR基因CAG重复数与男性不育相关性的病例对照研究,并用RevMan4.2软件进行统计分析。结果:共纳入32篇符合条件的文献,累计特发性不育病例3153例、对照2314例。数据合并结果显示,男性不育、无精子症及中度少精子症者其CAG重复数均数均显著高于对照人群(P<0.01),三者与对照间CAG重复数均数的标准均数差分别为0.27,95%CI:0.17～0.37;0.29,95%CI:0.08～0.50;0.27,95%CI:0.13～0.41。而且,敏感性分析结果也与以上研究结果一致。结论:AR基因CAG重复多态性其重复数增多与精子发生障碍的风险相关。     

Male infertility: no evidence of involvement of androgen receptor gene among Indian men

Spermatogenesis is collaboratively controlled by testosterone and follicle stimulating hormone. Testosterone and its immediate metabolite dihydrotestosterone affect their roles through the androgen receptor (AR). Mutations in the AR gene have been shown to cause partial to complete androgen insensitivity or infertility in otherwise normal males. The dependence of germ cells upon Sertoli and Leydig cells for their differentiation into sperms and deletion studies of the AR gene in animal models indicate a direct or indirect role of the AR gene in spermatogenesis. Although a few studies worldwide have reported AR mutations in male infertility, no similar study has been conducted on Indian populations. Therefore, we undertook this study to look at the contribution of AR mutations in male infertility among Indian men. We have sequenced the complete coding region of the AR gene in a total of 399 infertile samples, comprising 277 azoospermic, 100 oligozoospermic, and 22 oligoteratozoospermic samples. A total of 100 healthy males with proven fertility and the same ethnicity as the experimental group served as controls. Sequence analysis revealed no mutation in any of these samples. Our study suggests that mutations in the AR gene are less likely to cause azoospermia and oligozoospermia; however, it was difficult to rule out its effect in oligoteratozoospermia, as the sample size was small.     

Cytogenetic and molecular analysis of the Y chromosome: absence of a significant relationship between CAG repeat length in exon 1 of the androgen receptor gene and infertility in Indian men

The genetic basis of male infertility remains unclear in the majority of cases. Recent studies have indicated an association between microdeletions of the azoospermia factor a (AZFa)-AZFc regions of Yq and severe oligospermia or azoospermia. Increased (CAG)n repeat lengths in the androgen receptor (AR) gene have also been reported in infertile men. Therefore, in order to assess the prevalence of these genetic defects to male infertility, 183 men with non-obstructive azoospermia (n = 70), obstructive azoospermia (n = 33), severe oligospermia (n = 80) and 59 fertile men were examined cytogenetically and at molecular level for Yq deletions, microdeletions, and AR-CAG repeat lengths along with hormonal profiles [luteinizing hormone (LH), follicle-stimulating hormone (FSH) and testosterone (T)]. We used high resolution cytogenetics to detect chromosome deletions and multiplex polymerase chain reaction (PCR) involving 27 sequence-tagged site (STS) markers on Yq to determine the rate and extent of Yq microdeletions. PCR amplification with primers flanking exon 1 of AR gene was used to determine the AR-(CAG)n repeat lengths. Hormonal profiles (LH, FSH and T levels) were also analysed in infertile and fertile men. Testicular biopsies showed Sertoli cell only (SCO) morphology, maturation arrests (MA) and hypospermatogenesis. No chromosome aberrations were found in infertile men but there was a significant increase (p < 0.001) in the association of acrocentric chromosomes including the Y chromosome. Yq microdeletions were found in 16 non-obstructive azoospermic men (16 of 70; 22%) and seven severe oligospermic individuals (seven of 80; 8.7%) and most of them had deletions in the sY240 locus. No Yq microdeletions were detected in patients with obstructive azoospermia. No statistically significant difference in the mean length of CAG repeats in AR gene was observed between infertile and fertile men (22.2 +/- 1.5 and 21.5 +/- 1.4 respectively). No significant increase or decrease in levels of LH, FSH and T was observed in infertile and fertile men. In some infertile men, significantly elevated levels of FSH alone or in combination with LH were found to be indicative of failure of spermatogenesis and/or suggestive of testicular failure. Y-chromosome microdeletions contribute to infertility in some patients but no relationship could be established with the (CAG)n repeat lengths in exon 1 of the AR gene in infertile Indian men.     

Analysis of 6 single-nucleotide polymorphisms in the androgen receptor gene in Chilean patients with primary spermatogenic failure

Androgens are essential for spermatogenesis. It has been postulated that androgen activity is modulated directly or indirectly by genetic variability in the androgen receptor gene sequence, including CAG/GGN polymorphisms and single-nucleotide polymorphisms (SNP). In this study, the frequency of 6 SNPs that constitute a haplotype in the androgen receptor sequence was determined by enzyme restriction assays and allele-specific polymerase chain reactions in 117 secretory azo/oligozoospermic men (93 idiopathic and 24 excryptorchidic), and in 121 controls with normal spermatogenesis (42 obstructive and 79 normozoospermic men) whose hormonal measurements and length of CAG/GGN polymorphisms were previously determined. The frequency of these 6 SNPs was not different between patients and controls. A total of 10 haplotypes (HAPs 1-10) formed by these 6 SNPs were found, and one of these haplotypes was observed with high frequency in the total population (HAP1, 83.2%; P < .001, χ(2) test). The frequency of the 10 haplotypes was not different between patients and controls, except for HAP5, which was only detected in one patient with a history of bilateral cryptorchidism (P = 0.014, Bonferroni test). On the other hand, no associations were found between the haplotypes studied and shorter or longer CAG or GGN polymorphisms. Interestingly, we found that the CAG 21 allele, which was previously correlated with an increased risk of idiopathic spermatogenic impairment, was more frequently found among the less common haplotypes that have higher follicle-stimulating hormone serum levels. In summary, we did not find an increased frequency of particular haplotypes in infertile men with idiopathic spermatogenic impairment compared with control men; however, we found that the CAG 21 allele, which appears to be associated with male infertility, is observed at a significantly higher proportion among the less common androgen receptor haplotypes.     

CAG repeat length in the androgen receptor gene affects the risk of male infertility

During recent years several studies have suggested that a slight increase in the number of CAG repeat sequences in exon 1 of the androgen receptor gene causes idiopathic oligozoospermia. We tested whether CAG repeats are more numerous in men with idiopathic infertility compared to those with known causes of oligozoospermia. CAG repeats were analysed in a consecutive sample of 217 infertile men covering a wide range of diagnoses and sperm counts. Data were compared with those of a control group of 131 normozoospermic men including 62 fathers. CAG repeats (x +/- SD) did not differ between idiopathically (21.4 +/- 2.9) and non-idiopathically infertile men (21.6 +/- 2.8) or normozoospermic men of unproven fertility (20.6 +/- 3.0). Only fathers had significantly fewer repeats (19.4 +/- 3.1; p < 0.001). Different from controls, no correlation between CAG repeats and any semen parameter existed in patients. Comparison of our and published studies showed that odds ratios for infertility in men with CAG repeat length in the upper quartile of the normal range increased when the controls were selected by proven fertility. We conclude that more numerous CAG repeats do not directly cause oligozoospermia and propose that men with longer CAG repeats might be more prone to develop infertility in response to any pathogen/epigenetic factors.     

An increased CAG repeat length in the androgen receptor gene in azoospermic ICSI candidates

The androgen receptor gene has a polymorphic trinucleotide repeat that encodes a polyglutamine tract in its N-terminal transactivation domain. We started this study in order to find out whether a correlation existed between the length of this polymorphic tract and the presence of azoospermia in candidates for intracytoplasmic sperm injection (ICSI). The CAG repeat length in exon 1 of the androgen receptor (AR) gene was directly sequenced in 102 patients with azoospermia and in 96 fertile controls. Hormone levels were also measured in patients with azoospermia. The mean AR gene CAG repeat length was significantly larger in azoospermic subjects than it was in control fertile men (23.25 +/- 2.7 versus 22.42 +/- 2.8; P =.033). A receiver operating characteristic analysis evidenced a cutoff point at 22/23 CAG repeats at which the probability of being azoospermic increased 2.2 times. Subsequent logistic regression analysis of the data showed that the odds for azoospermia increased with the number of CAG repeats. Men with more than 26 CAG repeats have a 4.09 greater risk of being azoospermic. Therefore, in our candidates for ICSI, a direct correlation exists between the CAG repeat length in the exon 1 of the AR gene and the risk of being azoospermic.     

Phenotypic heterogeneity of mutations in androgen receptor gene

Androgen receptor （AR） gene has been extensively studied in diverse clinical conditions. In addition to the point mutations, trinucleotide repeat （CAG and GGN） length polymorphisms have been an additional subject of interest and controversy among geneticists. The polymorphic variations in triplet repeats have been associated with a number of disorders, but at the same time contradictory findings have also been reported. Further, studies on the same disorder in different populations have generated different results. Therefore, combined analysis or review of the published studies has been of much value to extract information on the significance of variations in the gene in various clinical conditions. AR genetics has been reviewed extensively but until now review articles have focused on individual clinical categories such as androgen insensitivity, male infertility, prostate cancer, and so on. We have made the first effort to review most the aspects of AR genetics. The impact of androgens in various disorders and polymorphic variations in the AR gene is the main focus of this review. Additionally, the correlations observed in various studies have been discussed in the light of in vitro evidences available for the effect of AR gene variations on the action of androgens.     

Androgen receptor CAG repeat lengths in ductal carcinoma in situ of breast, longest in apocrine variety

CAG repeat number in the androgen receptor (AR) has been associated with decreased prostate cancer risk, and AR expression has been found in female breast cancer, often associated with apocrine differentiation. Because trinucleotide expansion can alter gene expression and protein function, we hypothesized that it might occur in breast neoplasms. We used a repeat expansion detection technique to determine CAG repeat lengths in DNA from breast biopsies. Three lesion types were microdissected: fibroadenoma (48 cases), ductal carcinoma in situ (DCIS, 24 cases), and invasive mammary carcinoma (18 cases). The maximum number of CAG repeats in either allele of each patient in these three groups was compared. Microsatellite repeat lengths in DCIS were longer than in fibroadenomas or invasive carcinomas (P= 0.017 comparing DCIS vs invasive carcinomas). Two cases of apocrine DCIS had very long repeat lengths, both exhibiting microsatellite lengths at the longest range of normal (32 and 33). Inherited differences in AR CAG length might influence the transition from DCIS to invasive breast cancer, perhaps by modulating function of AR in breast tissue. AR microsatellite polymorphisms could influence cellular differentiation in DCIS lesions, promoting formation of the apocrine subtype in the presence of longer CAG repeats.     

Genetic screening in infertile Mexican men: chromosomal abnormalities, Y chromosome deletions, and androgen receptor CAG repeat length

In our study, we analyzed chromosomal abnormalities, Y chromosome deletions, androgen receptor CAG repeat length and their association with defective spermatogenesis in infertile Mexican men. Eighty-two infertile patients and 40 controls were screened for karyotypic abnormalities, Y chromosome microdeletions, and CAG repeats. Nine infertile males (11%) carried chromosomal abnormalities and 10 (12.2%) presented Y chromosome microdeletions. The mean CAG repeat length was 21.6 and 20.88 base pairs in idiopathic infertile males and controls, respectively. Our results suggest that chromosomal aberrations and Y-chromosomal microdeletions are related to male infertility in Mexican men. In addition, expansion of the CAG repeat segments of the androgen receptor is not correlated with male idiopathic infertility.     

CAG repeat variation in the mtDNA polymerase gamma is not associated with oligoasthenozoospermia

Variations in the trinucleotide-CAG repeat number of the catalytic subunit of the mitochondrial DNA polymerase gamma (POLG) have been speculated to be associated with male infertility. The ten CAG repeats (10/10) were found to be the most common allele (88%), absence of which was found to be associated with male infertility. As no study on Indian population was conducted so far to support this view, we investigated the distribution of the POLG -CAG repeats in 509 oligoasthenozoospermic and 241 normozoospermic control Indian men from the same ethnic background. Our study suggested that the distribution of common allele (10/10) was almost similar in both infertile (75%) and normozoospermic (75.5%) men. Further, we had analysed the CAG repeat number in as many as 1306 Indian men belonging to different ethnic, geographical and linguistic backgrounds and found the common allele 10/10 at a frequency of 78.4%. Our study, therefore, suggests that the 10-CAG repeat is the most common allele present in Indian populations, but its absence and the occurrence of the other mutant homozygous (non 10/non 10) genotype should not be understood as being specific to infertility. It, thus, suggests that the POLG -CAG repeat variation is not associated with male infertility in Indian populations, and hence is not a useful marker for screening infertile men.     

The relationship between anogenital distance and the androgen receptor CAG repeat length

Anogenital distance (AGD) is used to define degree of virilization of genital development, with shorter length being associated with feminization and male infertility. The first exon of the androgen receptor (AR) consists of a polymorphic sequence of cytosine–adenine–guanine (CAG) repeats, with longer CAG repeat lengths being associated with decreased receptor function. We sought to determine if there is an association between AGD and AR CAG repeat length. A cross-sectional, prospective cohort of men evaluated at a urology clinic at a single institution was recruited. AGD (the distance from the posterior scrotum to the anal verge) and penile length (PL) were measured. Sanger DNA sequence analysis was used to define CAG repeat length. AGD and CAG repeat lengths in 195 men were determined. On unadjusted analysis, there was no linear relationship between CAG repeat length and PL (P=0.17) or AGD (P=0.31). However, on sub-population analyses, those men with longer CAG repeat lengths (>26) had significantly shorter AGDs compared to men with shorter CAG repeat lengths. For example, the mean AGD was 41.9 vs. 32.4 mm with a CAG repeat length ≤26 vs. >26 (P=0.01). In addition, when stratifying the cohort based on AGD, those with AGD less than the median (i.e. 40 mm) had a longer CAG repeat length compared to men with an AGD >40 mm (P=0.02). In summary, no linear relationship was found between AGD and AR CAG repeat length overall.