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.     

Androgen receptor-CAG repeats in infertile Egyptian men

This study aimed to assess the androgen receptor (AR) codon amino acids glutamine (CAG) repeats in 185 Egyptian men divided into fertile controls (n = 30), oligoasthenoteratozoospermic (OAT) men (n = 35), nonobstructive azoospermic (NOA) men (n = 120; 18 successful testicular sperm extraction (TESE) and 102 unsuccessful TESE cases). They were subjected to history taking, genital examination, semen analysis, testicular biopsies for NOA cases, serum hormones and CAG repeats by PCR. The mean AR-CAG repeats showed significant difference between NOA group compared with fertile controls or OAT groups. Nonsignificant difference was elicited between OAT group and fertile controls. In NOA cases, CAG repeats demonstrated nonsignificant difference between unsuccessful and successful TESE. AR-CAG repeats elicited significant negative correlation with sperm count, significant positive correlation with sperm normal forms percentage and nonsignificant correlations with sperm motility per cent, tested serum hormones or testicular volume. It is concluded that AR-CAG repeats in Egyptian infertile men are in the range of other international or regional studies. AR-CAG repeats have demonstrated nonsignificant difference regarding TESE outcome in NOA cases.     

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.     

No association of androgen receptor GGN repeat length polymorphism with infertility in Indian men

Androgens, acting through the androgen receptor (AR), play a role in secondary sexual differentiation from the prenatal stage to adulthood, including spermatogenesis. The AR gene has 2 polymorphic trinucleotide repeats (CAG and GGN) in exon 1. The CAG repeat length polymorphism has been well studied in a variety of medical conditions, including male infertility. Many of these studies have shown an association of the expanded CAG repeats with male infertility, although this is not true for all populations. The GGN repeat, in contrast, has been less thoroughly studied. Thus far, only 4 reports worldwide have analyzed the GGN repeat, alone or in combination with the CAG repeat, in male infertility cases. No such study has been undertaken on infertile Indian men. Therefore, we have analyzed AR-GGN repeats in a total of 595 Indian males, including 277 azoospemric, 97 oligozoospermic, and 21 oligoteratozoospermic cases, along with 200 normozoospermic controls. The analysis revealed no difference in the mean number or the range of the repeat between cases (mean = 21.51 repeats, range 15-26 repeats) and controls (mean 21.58 repeats, range 15-26 repeats). Furthermore, no difference was observed when azoospermic (mean = 21.53 repeats, range 15-26 repeats), oligozoospermic (mean = 21.46 repeats, range 15-26 repeats), and oligoteratozoospermic cases (mean = 21.48, range 19-26 repeats) were compared individually with the controls.     

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。     

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.     

The CAG repeat polymorphism of mitochondrial polymerase gamma (POLG) is associated with male infertility in Tunisia

Male fertility largely depends on sperm quality, which may be affected by environmental and genetic factors. Recent data emphasised the implication of the polymorphism of mitochondrial DNA polymerase gamma (POLG) CAG repeats in male infertility. In this report, we explored a possible role of the (POLG) gene polymorphism in male infertility in Tunisian men. The polymorphic CAG repeat in the nuclear POLG gene was studied in 339 male subjects (216 patients with infertility (69 azoospermic, 115 oligoasthenoteratospermic and 32 normospermic) and 123 fertile) after DNA amplification by PCR, followed by genotyping using an automatic sequencer. The heterozygous and the homozygous mutant genotypes (10/ ≠ 10 and ≠ 10/ ≠ 10) were significantly more frequent among infertile patients than among fertile controls (11.2% versus 1.6%, P = 1.3 × 10(-3) and 4.6% versus 0.8%, P = 4.2 × 10(-7) respectively). We also found a significant difference between the frequencies of 10/ ≠ 10 genotype in azoospermic (4.4%) and in oligoasthenoteratospermic (15.6%) infertile patients (P = 2.6 × 10(-2) ). However, the homozygous mutant genotype (≠ 10/ ≠ 10) was seen at similar frequencies in azoospermic, normospermic and oligoasthenospermic men (4.4%, 3.1% and 5.2% respectively). Under our conditions, the findings showed an association between POLG CAG repeat polymorphism and male infertility in Tunisian population.     

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.     

Testicular follicle-stimulating hormone receptors in idiopathic male infertility

To ascertain whether abnormalities in testicular binding of follicle-stimulating hormone (FSH) are related with spermatogenic impairment found in idiopathic male infertility, we measured FSH receptors in testicular tissues obtained by biopsy from 48 infertile men. The 48 infertile men were divided into 3 groups by histological grading using Johnsen's score count, and testicular FSH receptors among these groups were compared. Although 9 of the 18 infertile men with low Johnsen's score count and 5 of the 15 men with middle score count had no obvious FSH binding sites with high affinity, all 15 men with a high score count had high affinity FSH binding sites. In connection with high affinity binding sites for FSH, maximum binding number (Bmax) decreased significantly with the degree of spermatogenic impairment, but the association constant (Ka) was similar among the 3 groups. The present findings demonstrate that the decrease in testicular high affinity binding sites for FSH is related with the degree of spermatogenic impairment found in idiopathic male infertility.     

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.     

The association of androgen- and oestrogen-receptor gene polymorphisms with urolithiasis in men

OBJECTIVE: To evaluate the association of urolithiasis with polymorphic microsatellite (encoding cytosine, adenine, and guanine, CAG) repeats in the exon 1 region of the androgen receptor (AR) gene and thymine/adenine (TA) repeats in the oestrogen receptor (ER). PATIENTS AND METHODS: Patients with urolithiasis (149) and a group of normal controls (102) were examined and compared. The CAG repeats of the AR gene and TA repeats of the ER gene were detected by polymerase chain reaction. The CAG repeats ranged from 171 bp (10 CAG repeats with 141 bp of amplified flanking sequences) to 270 bp (43 CAG repeats). The TA repeats ranged from 160 bp to 194 bp. Associations between calcium oxalate stone disease and the CAG repeats in AR gene and TA repeats in ER gene were then evaluated. The results were classified according to sex and peaks in allelic frequency distribution. RESULTS: There was a significant difference between the male stone patients and the normal controls in the distribution of CAG repeats in the AR gene. Both groups showed a high percentage of 21-repeats in the allelic distribution, at 17 (16%) and 20 (37%) in stone patients and normal controls, respectively. The results indicate that 21-CAG repeats might be related to a lower risk of stone formation in men (P < 0.05). In the ER gene, the peak allelic distribution of TA repeats was 14, showing a significant difference between male stone patients and the normal control subjects (P < 0.01). There were no statistical differences between female stone patients and the control subjects in either the AR or the ER gene. CONCLUSION: Urolithiasis among men appears to be associated with AR gene CAG repeat and ER gene TA repeat polymorphisms, whereas there was no significant association among female stone patients. These sex hormone receptors seem to be related to the higher incidence of stone formation among 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.     

CAG repeat length analysis and mutation screening of the androgen receptor gene in Japanese men with idiopathic azoospermia.

Because androgens are required for normal spermatogenesis, we are investigating abnormalities in the androgen receptor as a possible cause of impaired spermatogenesis in patients with idiopathic male infertility. The CAG repeat length in exon 1 and mutations of the androgen receptor gene were studied in 30 men with idiopathic azoospermia and in 51 fertile men. In men with azoospermia, plasma luteinizing hormone (LH), follicle-stimulating hormone (FSH), and testosterone levels were measured and testicular biopsies were performed. The CAG repeat length ranged from 19 to 30 (mean 23.4 +/- 2.9) and from 17 to 28 (mean 23.7 +/- 3.2) in men with azoospermia and in controls, respectively. There was no significant difference between the 2 groups. In men with azoospermia, the Johnsen testicular biopsy score negatively correlated with plasma FSH (P < .01). However, the Johnsen testicular biopsy score did not correlate with plasma LH and testosterone levels. The CAG repeat length did not correlate with the Johnsen testicular biopsy score, or with plasma concentrations of LH, FSH, and testosterone. No abnormalities in the androgen receptor gene were detected. These facts suggest that the CAG repeat length and alterations in the androgen receptor gene are not associated with the etiology of idiopathic azoospermia.     

Evidence for association of sex hormone-binding globulin and androgen receptor genes with semen quality

The roles of androgen receptor AR(CAG)n gene polymorphisms and sex hormone-binding globulin SHBG(TAAAA)n gene polymorphisms on semen quality were studied. One hundred fourteen men were included in the study: 85 with normal sperm count and 29 oligospermic. The genotype analysis, on DNA extracted from spermatozoa, revealed five SHBG(TAAAA)n alleles with 6–10 repeats and 18 AR(CAG)n alleles with 12–32 repeats. The SHBG allelic distribution showed that in men with normal sperm count and motility, those with short SHBG alleles had higher sperm concentration than men with long SHBG alleles ( P  = 0.039). As concerns AR(CAG)n polymorphisms, men with short AR alleles had lower sperm motility compared to those with long AR alleles ( P  < 0.001) in both total study population and normal sperm count men. The synergistic effect analysis of the two polymorphisms revealed an association between sperm motility ( P  = 0.036), because of the effect of AR(CAG)n polymorphism on sperm motility. In conclusion, long AR alleles were found to be associated with higher sperm motility, while short SHBG alleles were associated with higher sperm concentration, supporting the significance of these genes in spermatogenesis and semen quality.     

雄激素受体基因CAG多态性对男性激素避孕有效性影响的研究

目的:分析应用肌注十一酸睾酮酯(TU)进行激素避孕的男性志愿者中起反应者与不起反应者雄激素受体(AR)基因(CAG)n微卫星多态性,并探讨该多态性对激素避孕效果的影响。方法:29例TU不起反应者和34例起反应者分别作为试验组和对照组,应用PCR和DNA测序技术对两组外周血标本进行CAG重复数测定,分析该微卫星多态性对激素避孕效果的影响。结果:试验组和对照组CAG重复数的均数分别为23.62和22.97,均数比较差异无显著性(P>0.05)。短组CAG(n≤22)在试验组和对照组的分布分别为51.7%、50.0%;长组CAG(n>22)在试验组和对照组分布分别为48.3%、50.0%,长短组分布相同。CAG重复数与精子密度之间未见相关性。在FSH浓度>0.2IU/L组中,CAG重复数>22的受试者达到无精子症的机会是其他受试者的1.5倍。结论:受试者AR基因(CAG)n重复数呈多态性,但不反应组与反应组之间不具有显著性差异,AR基因CAG重复数或其他因素与男性激素避孕效果之间的关系有待进一步探讨。     

Testicular follicle-stimulating hormone receptors and effectiveness of human menopausal gonadotropin-human chorionic gonadotropin treatment in idiopathic male infertility

To investigate the relationship between testicular follicle stimulating hormone (FSH) receptors and the effectiveness of human menopausal gonadotropin (hMG-hCG) treatment in idiopathic male infertility, 48 infertile men were examined. Most of the 14 patients without detectable testicular high affinity FSH receptors did not show any increase in sperm count after the hMG-hCG treatment, whereas 23 of the 34 patients with FSH receptors responded to the treatment. In patients with FSH receptors, patients with a middle or high Johnsen's score count responded more than those with a low score count did. From the above results, it seems that both the presence or absence of testicular FSH receptors and the histological appearance of spermatogenesis predict responsiveness to hMG-hCG treatment in infertile men.     

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.     

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.