1 Fertility Centre, Scanian Andrology Centre, 2 Department of Urology, 3 Department of Clinical Chemistry, Malmö University Hospital, Lund University, Malmö and 4 Slottstadens läkarhus, Fågelbacksgatan 11, Malmö, Sweden
5 To whom correspondence should be addressed at: Wallenberg Laboratory, 4th Floor, Entrance 46, Malmö University Hospital, SE-205 02 Malmö, Sweden. Email: yasir.ruhayel{at}kir.mas.lu.se
![]() |
Abstract |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
Key words: androgen receptor/infertility/microdeletion/polymorphism/Y chromosome
![]() |
Introduction |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
The gene encoding the AR is located on the X chromosome and contains eight exons coding for four functional domains: an N-terminal transactivation domain, a DNA-binding domain, a hinge domain and a C-terminal androgen-binding domain (Lubahn et al., 1988b, 1989
). There are two trinucleotide repeat tracts of polymorphic length in the transactivating domain, (CAG)nCAA coding for glutamine residues, and further downstream, (GGT)3GGG(GGT)2(GGC)n (the GGN repeat) coding for glycine (Lubahn et al., 1988a
). Mean CAG repeat length in normal men varies according to ethnicity, with African American men having on average fewer repeats than Caucasians and Far-Eastern Asians (Sleddens et al., 1993
; Irvine et al., 1995
; Sartor et al., 1999
; Correa-Cerro et al., 1999
; Hsing et al., 2000
; Kittles et al., 2001
). The CAG repeat number in healthy men of varying ethnicity ranges from 11 to 35 (Giwercman et al., 1998
; Kittles et al., 2001
), but an abnormal elongation of CAG repeat number >40 has been linked to spinal and bulbar muscular atrophy (SBMA, also known as Kennedy's disease) (La Spada et al., 1991
). In addition to the classical symptoms of slowly progressing proximal muscle weakness and atrophy, affected men sometimes also present with gynaecomastia and reduced or absent reproductive capacity, which is why much attention recently has been paid to this region of the AR gene in relation to idiopathic male infertility. Some reports have indicated associations between longer CAG repeat tracts within the normal range and infertility (Dowsing et al., 1999
) or spermatogenic defects in infertile men (Tut et al., 1997
), whereas others have not found any such correlations (Giwercman et al., 1998
; Dadze et al., 2000
; von Eckardstein et al., 2001
; Rajpert-De Meyts et al., 2002
; Van Golde et al., 2002
). However, von Eckardstein et al. (2001)
did report an inverse correlation between sperm counts and CAG repeat lengths in their control group.
While the CAG repeat tract has received much attention, not much is known about the GGN repeat region. However, the significance of this part of the AR gene for the transactivating capacity of the receptor has been shown in vitro (Gao et al., 1996), underlining the importance of this repeat for optimal receptor function. The association between GGN repeat lengths and male infertility has to our knowledge been investigated in only two previous studies. Tut et al. (1997)
reported no significant differences in distributions of GGN repeat lengths between an infertile cohort and fertile controls. We have recently reported that the distributions of the 23 and 24 GGN repeat alleles did not differ significantly between infertile men with sperm counts <5x106/ml and controls (Lundin et al., 2003
). However, there is no information regarding the possible relationship between different combinations of AR gene repeats and male infertility.
To address this issue, we expanded the analysis performed by Lundin et al. (2003) by investigating whether joint distributions of GGN and CAG repeats differed in a cohort of infertile men with sperm counts <5x106/ml compared to an ethnically matched control group. Additionally, the reproductive parameters of individuals carrying the AR alleles with the most common GGN repeat lengths (23 and 24) were compared. Men were also screened a priori for abnormal karyotypes and Y chromosome microdeletions to avoid confounding by genetic factors known to be associated with infertility.
![]() |
Materials and methods |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
The laboratory participates in external quality control programmes supervised by the Nordic Association of Andrology (NAFA) and the ESHRE.
Subjects
Infertile men
We created a cohort of 144 consecutive, infertile men who had been referred to the Scanian Andrology Centre at Malmö University Hospital, Sweden and who were clinically evaluated in a work-up before performing IVF or ICSI. Patients were included in the cohort if they had a minimum of 1 year of infertility and sperm counts 5.0x106/ml as determined by at least two consecutive semen analyses. Patients were excluded a priori if they had: (i) endocrine disturbances due to hypogonadotropic hypogonadism or abuse of androgenic (anabolic) steroids, (ii) obstructive syndromes of the urogenital tract, or (iii) undergone treatment with chemotherapeutic agents.
We thereafter selected the 99 patients whose mothers were of Swedish origin from the cohort of 144 men for AR gene sequencing because the gene is known to exhibit racial variation and it is inherited on the X chromosome. The cohort was screened for Y chromosome microdeletions and chromosomal aberrations.
In order to avoid confounding by other genetic factors known to affect fertility status, we thereafter excluded the 10 men who were found to carry Y chromosome microdeletions or karyotypic abnormalities from the cohort of 99 men. Of the remaining 89 patients, sequencing of the CAG and GGN tracts was performed in 85 and 81 patients respectively.
The median age of the 99 patients was 31 years (range: 2351). Data from the andrological physical examination and history are presented in Table I. Testicular volumes measured by orchidometer were available for 97 men. Of the 99 infertile patients, 36 were azoospermic (no sperm in the ejaculate), 28 were extremely oligozoospermic (>0 and 1.0x106 sperm/ml) and 35 were severely oligozoospermic (>1.0 and
5.0x106 sperm/ml). Of the men with azoospermia, extreme oligozoospermia and severe oligozoospermia, 18, 18 and 21 respectively had idiopathic infertility. For the purposes of the present study, the term idiopathic infertility (prior to screening for Y chromosome microdeletions) was defined as infertility in an included patient with the absence of the following: varicocele, cryptorchidism, retractile testis, male accessory gland infections (MAGI), mumps orchitis, and chromosomal aberrations.
|
Semen and seminal plasma analyses
Assessment of sperm concentration was performed according to World Health Organization (1999) guidelines. Concentrations of seminal Prostate Specific Antigen (PSA), zinc and fructose were assessed using methods described previously (Elzanaty et al., 2002
). The levels of these seminal parameters were available for 83 of the 89 (93%) men with no detected genetic abnormality.
Hormone assays
Inhibin B levels were analysed in 65 of the 89 patients with no detected genetic anomaly and in all 223 conscripts. All analyses were performed at Malmö University Hospital, Malmö, Sweden using immunometric enzyme-linked immunosorbent assays with a commercially available kit (Oxford Bio-Innovation Ltd, UK). Laboratory total assay variation was 12.4% at 25 ng/l and 12.8% at 305 ng/l, and the lower limit of detection was 15 pg/ml. Testosterone levels were measured in 87 patients using an immunoassay (Access®; Beckman Coulter Inc., USA). Laboratory total assay variation was 2.8% at 2.9 nmol/l and 3.2% at 8.1 nmol/l. Plasma FSH and LH concentrations were measured in 87 patients by means of immunoassays (Immuno 1®; Bayer Diagnostics Division, USA). Laboratory total assay variation for FSH was 2.5% at 2.9 IU/l and 1.4% at 15 IU/l, and for LH it was 2.6% at 3.0 IU/l and 1.7% at 15 IU/l. Serum sex hormone-binding globulin (SHBG) was measured in 86 patients using an immunoassay (Immulite® 2000; Diagnostic Products Corp., USA). Total assay variation was 3.7% at 29 nmol/l and 6.7% at 85 nmol/l.
Genetic analyses
Y chromosome microdeletions
Patient genomic DNA was prepared from peripheral venous blood leukocytes. Screening for microdeletions was performed in duplex PCR using previously published STS primers specific to the Y chromosome euchromatin (Vollrath et al., 1992; Reijo et al., 1995
; Kent-First et al., 1999
; Sun et al., 1999
). All 144 patients were screened in a first round using recommended PCR methodology (Simoni et al., 1999
). The extent and location of microdeletions detected in the first round were assessed in a second higher resolution round utilizing 44 Y chromosome-specific primer pairs.
AR gene repeat tracts
The repeat tracts were amplified using a nested PCR amplification procedure with cycling conditions and primers as previously described (Lundin et al., 2003). The numbers of GGN and CAG repeats were obtained by direct sequencing externally on a Beckman Coulter CEQTM 2000XL DNA sequencer (Beckman Coulter Inc.) (Lundin et al., 2003
). Material was available for sequencing of the CAG and GGN tracts in 85/89 (96%) and 81/89 (91%) of the patients respectively. Both tracts were sequenced in 79 of the patients (89%) and in all 223 conscripts.
Statistical analysis
Statistical calculations were performed using SPSS 11.0 for Windows (SPSS Inc., USA). Confidence intervals of proportions were calculated by the modified Wald method. Fisher's exact test was applied for testing differences in proportions between groups. Distributions of parameters in the two groups were compared by the KruskalWallis test. Correlation coefficients were calculated by Spearman's method. A significance level of at least P<0.05 (two-sided) was used throughout.
In order to evaluate the impact of the GGN repeat length on the phenotype of the infertile men, binary logistic regression analysis was used to calculate the odds ratios (OR) of having reduced prostatic glandular function and low testicular volume. Therefore, a prostate function variable defined by seminal zinc and seminal PSA concentrations was created. The medians for these values were calculated for the entire group of infertile men. Men having seminal zinc or seminal PSA concentrations below the medians for the whole group were categorized as having subnormal prostate function, whereas the remainder was classified as having normal prostate function. The men with 23 GGN repeats served as the reference group. Prostate function was entered as a dependent variable with GGN length (alleles 23 and 24 pre-selected) defined as a categorical covariate and plasma testosterone levels and CAG length as continuous covariates in order to avoid confounding by variations in these factors. The OR of having low total testicular volume was calculated in an analogous fashion, with a total testicular volume group being created. Men having a total testicular volume <30 ml (equal to the median in our material) were classified as having low total testicular volume, with the remainder having normal total testicular volume. Binary logistic regression analysis was also carried out for the conscripts using the medians of the relevant values for that group.
![]() |
Results |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
Chromosomal aberrations
Karyotyping revealed that five patients (5.1%; 95% CI: 1.912%), carried chromosomal aberrations, 46,XY,t(X;1)(p22;q25); 46,X,der(X)t(X;Y)(p22;p11); 47,XXY[46]/48,XXXY[1]/46,XY[3]; 46,X,r(Y)(p11q11) and 47,XXY. All these patients except the Klinefelter mosaic were azoospermic.
Y chromosome microdeletions
AZFc microdeletions were found in five patients, one of whom also carried microdeletions of the AZFa and AZFb regions. Thus, this genetic aberration was detected in 5/99 (5.1%; 95% CI: 1.912) and among patients with idiopathic infertility (as defined prior to screening for genetic defects), 3/57 (5.3%; 95% CI: 1.215). Three patients with Y chromosome microdeletions had azoospermia, one had extreme oligozoospermia and one had severe oligozoospermia.
CAG and GGN repeat tracts in the AR
Distributions of the CAG and GGN alleles
The distributions of CAG and GGN repeats in the two groups of subjects are presented in Figures 1 and 2. Comparison of the repeat lengths in the infertile men and the conscripts by the KruskalWallis test revealed that neither GGN (P=0.19) nor CAG (P=0.16) repeat lengths differed significantly between groups. As previously published, the two by far most common GGN alleles, 23 and 24, occurred with similar frequencies in both controls and patients (53 versus 52%, P=0.90 and 37 versus 32%, P=0.41, for 23 and 24 GGN repeats respectively) (Figure 2). Conversely, the proportion of not 23 or 24 GGN repeats did not differ significantly between groups (10 versus 16%, P=0.20).
|
|
The median of the distributions of CAG lengths was 22 in the patient group and 21 in the conscripts, whereas the lower quartiles were respectively 21 and 20. The proportion of AR alleles with short (<21) CAG repeats among the infertile men [15/85 (18%)], was significantly (P=0.005) lower than in the controls [76/223 (34%)]. However, the proportion of short CAG alleles was not significantly higher (P=0.07) in the controls compared to the patients with idiopathic infertility [11/53 (21%)]. All threshold levels >21 repeats were associated with non-significant differences in the whole group of infertile men, as well as in the men with idiopathic infertility.
In addition, the AR genes containing CAG repeat tracts with <21 repeats in combination with the GGN tract containing 23 repeats (<21 CAG/23 GGN) occurred more frequently (P=0.003) in the conscripts [36/223 (16%)] than in the infertile men, [3/79 (4%).] The occurrence of the <21 CAG/23 GGN combination was also significantly higher (P=0.02) in the conscripts compared to the patients with idiopathic infertility, [2/51 (4%).] The <21 CAG/24 GGN combinations did not differ significantly (P=0.56) in prevalence between the conscripts [29/223 (13%)] and the infertile men [8/79 (10%)].
Comparison of AR alleles with 23 and 24 GGN repeats
Scatter graphs of the concentrations of zinc and PSA in seminal fluid, total testicular volumes and CAG repeat lengths plotted against GGN lengths in the infertile group seemed to indicate that the bulk of the differences in the values of these variables were accounted for by the two most common AR alleles (data not shown). Infertile men carrying 23 GGN repeats had significantly higher values of total testicular volume (P=0.04) and CAG repeat lengths (P=0.002) than men carrying 24 repeats (Table II and Figure 3). Among patients with idiopathic infertility, comparison of carriers of the 23 and 24 GGN repeat alleles revealed that the difference in total testicular volume was not significant (P=0.21), whereas the difference in CAG repeat lengths was significant (P=0.008). When analysed in the same way, the conscripts did not exhibit significant differences in total testicular volume (P=0.46), while differences in CAG repeat lengths were close to significant (P=0.08).
|
|
There was no statistically significant difference regarding any of the reproductive outcomes, when the 10% of the infertile men having <23 or >24 GGN repeats were compared to the men carrying the 23 GGN repeat allele. In the infertile patients, CAG repeat lengths did not correlate significantly with total testicular volume, levels of the prostatic markers, or any other of the seminal or endocrine parameters (data not shown).
![]() |
Discussion |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
Although the finding that short CAG repeat tracts were less common among the infertile men is in accordance with previous reports (Tut et al., 1997; Yong et al., 1998
), the only available studies on the relationship between polymorphism of the GGN tract and male infertility (Tut et al., 1997
; Lundin et al., 2003
) did not provide information regarding the combinations of AR gene repeats of the subjects.
Assuming that the number of GGN repeats directly corresponds to the length of the polyglycine tract in the AR in vivo, the data on gene repeat lengths may be interpreted in terms of AR function. It is conceivable that the AR coded for by the 23 GGN allele has greater activation capacity than the 24 repeat AR. Since the conscripts did not exhibit this difference, one may reason that this hypothesized GGN-regulated fine-tuning of the activating capacity of the AR manifests itself phenotypically only if the androgen levels are decreased, as in the infertile group in this study. Furthermore, differences in GGN repeat length seemed only to be associated with differences in testicular volume and prostatic secretory products, possibly indicating that polymorphism of this part of the AR predominantly affects the function in organs exposed to very high levels of androgens. Seminal zinc and PSA are secreted by the prostate, where dihydrotestosterone (DHT) occurs at high concentrations (Mooradian et al., 1987) and testosterone concentrations in the testis are
100-fold higher than in peripheral blood (Maddocks et al., 1993
). Prostate size has been shown to increase significantly in hypogonadal men receiving testosterone replacement therapy (Behre et al., 1994
; Snyder et al., 2000
). Levels of seminal zinc are low among hypogonadal patients (Canale et al., 1986
), and stimulation of testosterone secretion in normogonadotropic subfertile men has been shown to raise levels of prostatic secretions including zinc in semen (Ronnberg et al., 1981
). The degree of correlation between seminal concentrations of PSA and zinc has also been shown to be very high (Elzanaty et al., 2002
). It may therefore be reasoned that androgen receptor activity, as well as androgen concentrations, influences prostatic secretions.
Since an inverse correlation has previously been reported between CAG repeat number and resultant AR activity (Tut et al., 1997) it seems plausible to conclude that the <21 CAG/23 GGN combinations are associated with superior androgen receptor function, which may explain why they occurred less frequently among the infertile patients.
Another explanation for the differences in these parameters is linkage disequilibrium with other unidentified genetic factors. However, it appears that at least linkage with CAG repeat length cannot account for the postulated increase in AR activation capacity, since repeat lengths were significantly longer among bearers of the 23 GGN allele. This is clearly at odds with the proposal laid forth by a number of researchers that longer CAG repeat tracts are linked to a decrease in AR function (Tut et al., 1997; Dowsing et al., 1999
). A crucial step in clarifying whether there is a difference in activating capacity between the AR containing 23 or 24 repeats will be the construction of expression vectors and in vitro expression of AR genes containing 23 and 24 GGN repeats in combination with CAG tracts of different lengths.
While the <21 CAG/23 GGN combinations were found to be less frequent among the infertile men, there was also a considerable overlap between the CAG and GGN lengths in the groups studied. Therefore, the AR gene polymorphisms per se can hardly solely be the cause of male infertility. Instead, certain lengths or combinations of repeats might increase susceptibility to impairment of sperm production caused by other genetic, environmental or lifestyle-related factors (Skakkebaek et al., 2001). We have previously found that FSH and inhibin B levels do not correlate with CAG repeat length (Giwercman et al., 2004
). Additionally, high inhibin B levels have been found in men with impairment of spermatogenesis due to mild androgen receptor mutations (Giwercman et al., 2000
). This might imply that androgens mainly exert their effects on late stages of spermatogenesis (Zhang et al., 2003
) and that impairment of sperm production associated with AR gene polymorphism does not manifest itself with high FSH and low inhibin B levels, as found in the infertile group in the present study. Thus, in accordance with this hypothesis, future efforts to establish to what extent polymorphism of the AR gene repeat tract influences male fertility should be directed towards patient groups with normal FSH and inhibin B levels, i.e. without endocrine signs of early spermatogenic defects.
In the present study, an abnormal karyotype or Y chromosome microdeletion was detected in only 10% of the patients, AZF microdeletions accounting for half this number, which is in accordance with another study of a similar population (Osterlund et al., 2000). Three patients carrying microdeletions also had additional conditions that could explain their infertility, including cryptorchidism and varicocele. The differing prevalences of microdeletions reported in various papers probably depend mainly on study design including patient selection criteria, sample size and molecular detection technique and possibly also ethnic composition of the population studied (i.e. Y chromosome background).
In our study, repeat length was determined by direct sequencing, which is more accurate and less prone to interpretational errors than assessment using indirect methods such as comparison with product size markers. Furthermore, because the AR gene repeats are known to exhibit ethnic variation (Kittles et al., 2001), we matched the ethnicity of the infertile men and conscripts (controls), thereby eliminating stratification bias and its potentially confounding effect.
Our control group consisted of young military conscripts, considered from a reproductive point of view to be representative of the general population of young Swedish males (Andersen et al., 2000). Theoretically, the proportion of the conscripts that might in the future be affected by infertility should be
10%. Furthermore, the inclusion of potentially sub-fertile individuals in the control group ought rather to reduce the power to detect any differences between the cases and the controls. Therefore, using conscripts as a control group cannot explain the finding of a significantly lower proportion of the <21 CAG/23 GGN combinations among the infertile men.
In summary, our results suggest that the AR allele with 24 GGN repeats seems, at least in infertile men, to be associated with a higher odds ratio of having low testicular volume and low prostatic secretory function in comparison to the 23 GGN allele. The AR genes containing CAG repeat lengths shorter than 21 in combination with 23 GGN repeats may confer a lower risk of infertility to the bearers. This study provides novel information regarding the association between AR gene polymorphisms and male infertility, but in vitro expression studies on the effect of varying GGN length on AR transactivation capacity are necessary in order to better judge the significance of varying length in vivo.
![]() |
Acknowledgements |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
![]() |
References |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
Andersen AG, Jensen TK, Carlsen E, Jorgensen N, Andersson AM, Krarup T, Keiding N and Skakkebaek NE (2000) High frequency of sub-optimal semen quality in an unselected population of young men. Hum Reprod 15, 366372.
Behre HM, Bohmeyer J and Nieschlag E (1994) Prostate volume in testosterone-treated and untreated hypogonadal men in comparison to age-matched normal controls. Clin Endocrinol (Oxf) 40, 341349.[Medline]
Bruckert E (1991) How frequent is unintentional childlessness in Germany? Andrologia 23, 245250.[Medline]
Canale D, Bartelloni M, Negroni A, Meschini P, Izzo PL, Bianchi B and Menchini-Fabris GF (1986) Zinc in human semen. Int J Androl 9, 477480.[Medline]
Chandley AC, Gosden JR, Hargreave TB, Spowart G, Speed RM and McBeath S (1989) Deleted Yq in the sterile son of a man with a satellited Y chromosome (Yqs). J Med Genet 26, 145153.[Abstract]
Correa-Cerro L, Wohr G, Haussler J, Berthon P, Drelon E, Mangin P, Fournier G, Cussenot O, Kraus P, Just W et al. (1999) (CAG)nCAA and GGN repeats in the human androgen receptor gene are not associated with prostate cancer in a FrenchGerman population. Eur J Hum Genet 7, 357362.[CrossRef][Medline]
Dadze S, Wieland C, Jakubiczka S, Funke K, Schroder E, Royer-Pokora B, Willers R and Wieacker PF (2000) The size of the CAG repeat in exon 1 of the androgen receptor gene shows no significant relationship to impaired spermatogenesis in an infertile Caucasoid sample of German origin. Mol Hum Reprod 6, 207214.
Dowsing AT, Yong EL, Clark M, McLachlan RI, de Kretser DM and Trounson AO (1999) Linkage between male infertility and trinucleotide repeat expansion in the androgen-receptor gene. Lancet 354, 640643.[CrossRef][Medline]
Elzanaty S, Richthoff J, Malm J and Giwercman A (2002) The impact of epididymal and accessory sex gland function on sperm motility. Hum Reprod 17, 29042911.
Gao T, Marcelli M and McPhaul MJ (1996) Transcriptional activation and transient expression of the human androgen receptor. J Steroid Biochem Mol Biol 59, 920.[CrossRef][Medline]
Giwercman YL, Xu C, Arver S, Pousette A and Reneland R (1998) No association between the androgen receptor gene CAG repeat and impaired sperm production in Swedish men. Clin Genet 54, 435436.[Medline]
Giwercman A, Kledal T, Schwartz M, Giwercman YL, Leffers H, Zazzi H, Wedell A and Skakkebaek NE (2000) Preserved male fertility despite decreased androgen sensitivity caused by a mutation in the ligand-binding domain of the androgen receptor gene. J Clin Endocrinol Metab 85, 22532259.
Giwercman YL, Nikoshkov A, Bystrom B, Pousette A, Arver S and Wedell A (2001) A novel mutation (N233K) in the transactivating domain and the N756S mutation in the ligand binding domain of the androgen receptor gene are associated with male infertility. Clin Endocrinol (Oxf) 54, 827834.[CrossRef][Medline]
Giwercman YL, Richthoff J, Lilja H, Anderberg C, Abrahamsson PA and Giwercman A (2004) Androgen receptor CAG repeat length correlates with semen PSA levels in adolescence. Prostate, 59, 227223.[CrossRef][Medline]
Hiort O, Holterhus PM, Horter T, Schulze W, Kremke B, Bals-Pratsch M, Sinnecker GH and Kruse K (2000) Significance of mutations in the androgen receptor gene in males with idiopathic infertility. J Clin Endocrinol Metab 85, 28102815.
Hsing AW, Gao YT, Wu G, Wang X, Deng J, Chen YL, Sesterhenn IA, Mostofi FK, Benichou J and Chang C (2000) Polymorphic CAG and GGN repeat lengths in the androgen receptor gene and prostate cancer risk: a population-based case-control study in China. Cancer Res 60, 51115116.
Irvine RA, Yu MC, Ross RK and Coetzee GA (1995) The CAG and GGC microsatellites of the androgen receptor gene are in linkage disequilibrium in men with prostate cancer. Cancer Res 55, 19371940.[Abstract]
Kent-First M, Muallem A, Shultz J, Pryor J, Roberts K, Nolten W, Meisner L, Chandley A, Gouchy G, Jorgensen L et al. (1999) Defining regions of the Y-chromosome responsible for male infertility and identification of a fourth AZF region (AZFd) by Y-chromosome microdeletion detection. Mol Reprod Dev 53, 2741.[CrossRef][Medline]
Kittles RA, Young D, Weinrich S, Hudson J, Argyropoulos G, Ukoli F, Adams-Campbell L and Dunston GM (2001) Extent of linkage disequilibrium between the androgen receptor gene CAG and GGC repeats in human populations: implications for prostate cancer risk. Hum Genet 109, 253261.[CrossRef][Medline]
Kuroda-Kawaguchi T, Skaletsky H, Brown LG, Minx PJ, Cordum HS, Waterston RH, Wilson RK, Silber S, Oates R, Rozen S et al. (2001) The AZFc region of the Y chromosome features massive palindromes and uniform recurrent deletions in infertile men. Nat Genet 29, 279286.[CrossRef][Medline]
La Spada AR, Wilson EM, Lubahn DB, Harding AE and Fischbeck KH (1991) Androgen receptor gene mutations in X-linked spinal and bulbar muscular atrophy. Nature 352, 7779.[CrossRef][Medline]
Lubahn DB, Joseph DR, Sar M, Tan J, Higgs HN, Larson RE, French FS and Wilson EM (1988a) The human androgen receptor: complementary deoxyribonucleic acid cloning, sequence analysis and gene expression in prostate. Mol Endocrinol 2, 12651275.[Abstract]
Lubahn DB, Joseph DR, Sullivan PM, Willard HF, French FS and Wilson EM (1988b) Cloning of human androgen receptor complementary DNA and localization to the X chromosome. Science 240, 327330.[Medline]
Lubahn DB, Brown TR, Simental JA, Higgs HN, Migeon CJ, Wilson EM and French FS (1989) Sequence of the intron/exon junctions of the coding region of the human androgen receptor gene and identification of a point mutation in a family with complete androgen insensitivity. Proc Natl Acad Sci USA 86, 95349538.[Abstract]
Lundin KB, Giwercman A, Richthoff J, Abrahamsson PA and Giwercman YL (2003) No association between mutations in the human androgen receptor GGN repeat and inter-sex conditions. Mol Hum Reprod 9, 375379.
Ma K, Sharkey A, Kirsch S, Vogt P, Keil R, Hargreave TB, McBeath S and Chandley AC (1992) Towards the molecular localisation of the AZF locus: mapping of microdeletions in azoospermic men within 14 subintervals of interval 6 of the human Y chromosome. Hum Mol Genet 1, 2933.[Abstract]
Ma K, Inglis JD, Sharkey A, Bickmore WA, Hill RE, Prosser EJ, Speed RM, Thomson EJ, Jobling M, Taylor K et al. (1993) A Y chromosome gene family with RNA-binding protein homology: candidates for the azoospermia factor AZF controlling human spermatogenesis. Cell 75, 12871295.[Medline]
Maddocks S, Hargreave TB, Reddie K, Fraser HM, Kerr JB and Sharpe RM (1993) Intratesticular hormone levels and the route of secretion of hormones from the testis of the rat, guinea pig, monkey and human. Int J Androl 16, 272278.[Medline]
Mooradian AD, Morley JE and Korenman SG (1987) Biological actions of androgens. Endocr Rev 8, 128.[Abstract]
Osterlund C, Segersteen E, Arver S and Pousette A (2000) Low number of Y-chromosome deletions in infertile azoospermic men at a Swedish andrology centre. Int J Androl 23, 225229.[CrossRef][Medline]
Rajpert-De Meyts E, Leffers H, Petersen JH, Andersen AG, Carlsen E, Jorgensen N and Skakkebaek NE (2002) CAG repeat length in androgen-receptor gene and reproductive variables in fertile and infertile men. Lancet 359, 4446.[CrossRef][Medline]
Reijo R, Lee TY, Salo P, Alagappan R, Brown LG, Rosenberg M, Rozen S, Jaffe T, Straus D, Hovatta O et al. (1995) Diverse spermatogenic defects in humans caused by Y chromosome deletions encompassing a novel RNA-binding protein gene. Nat Genet 10, 383393.[Medline]
Richthoff J, Rylander L, Hagmar L, Malm J and Giwercman A (2002) Higher sperm counts in Southern Sweden compared with Denmark. Hum Reprod 17, 24682473.
Ronnberg L, Vihko P, Sajanti E and Vihko R (1981) Clomiphene citrate administration to normogonadotropic subfertile men: blood hormone changes and activation of acid phosphatase in seminal fluid. Int J Androl 4, 372378.[Medline]
Sartor O, Zheng Q and Eastham JA (1999) Androgen receptor gene CAG repeat length varies in a race-specific fashion in men without prostate cancer. Urology 53, 378380.[CrossRef][Medline]
Simoni M, Bakker E, Eurlings MC, Matthijs G, Moro E, Muller CR and Vogt PH (1999) Laboratory guidelines for molecular diagnosis of Y-chromosomal microdeletions. Int J Androl 22, 292299.[CrossRef][Medline]
Skakkebaek NE, Rajpert-De Meyts E and Main KM (2001) Testicular dysgenesis syndrome: an increasingly common developmental disorder with environmental aspects. Hum Reprod 16, 972978.
Sleddens HF, Oostra BA, Brinkmann AO and Trapman J (1993) Trinucleotide (GGN) repeat polymorphism in the human androgen receptor (AR) gene. Hum Mol Genet 2, 493.[Medline]
Snyder PJ, Peachey H, Berlin JA, Hannoush P, Haddad G, Dlewati A, Santanna J, Loh L, Lenrow DA, Holmes JH et al. (2000) Effects of testosterone replacement in hypogonadal men. J Clin Endocrinol Metab 85, 26702677.
Sun C, Skaletsky H, Birren B, Devon K, Tang Z, Silber S, Oates R and Page DC (1999) An azoospermic man with a de novo point mutation in the Y-chromosomal gene USP9Y. Nat Genet 23, 429432.[CrossRef][Medline]
Thonneau P, Marchand S, Tallec A, Ferial ML, Ducot B, Lansac J, Lopes P, Tabaste JM and Spira A (1991) Incidence and main causes of infertility in a resident population (1 850 000) of three French regions (19881989). Hum Reprod 6, 811816.[Abstract]
Tiepolo L and Zuffardi O (1976) Localization of factors controlling spermatogenesis in the nonfluorescent portion of the human Y chromosome long arm. Hum Genet 34, 119124.[Medline]
Tut TG, Ghadessy FJ, Trifiro MA, Pinsky L and Yong EL (1997) Long polyglutamine tracts in the androgen receptor are associated with reduced trans-activation, impaired sperm production, and male infertility. J Clin Endocrinol Metab 82, 37773782.
Van Golde R, Van Houwelingen K, Kiemeney L, Kremer J, Tuerlings J, Schalken J and Meuleman E (2002) Is increased CAG repeat length in the androgen receptor gene a risk factor for male subfertility? J Urol 167, 621623.[Medline]
Vogt PH, Edelmann A, Kirsch S, Henegariu O, Hirschmann P, Kiesewetter F, Kohn FM, Schill WB, Farah S, Ramos C et al. (1996) Human Y chromosome azoospermia factors (AZF) mapped to different subregions in Yq11. Hum Mol Genet 5, 933943.
Vollrath D, Foote S, Hilton A, Brown LG, Beer-Romero P, Bogan JS and Page DC (1992) The human Y chromosome: a 43-interval map based on naturally occurring deletions. Science 258, 5259.[Medline]
von Eckardstein S, Syska A, Gromoll J, Kamischke A, Simoni M and Nieschlag E (2001) Inverse correlation between sperm concentration and number of androgen receptor CAG repeats in normal men. J Clin Endocrinol Metab 86, 25852590.
World Health Organization (1999) Laboratory Manual for the Examination of Human Semen and SemenCervical Mucus Interaction, 4th edn. Cambridge University Press, Cambridge, UK.
Yong EL, Ghadessy F, Wang Q, Mifsud A and Ng SC (1998) Androgen receptor transactivation domain and control of spermatogenesis. Rev Reprod 3, 141144.
Zhang FP, Pakarainen T, Poutanen M, Toppari J and Huhtaniemi I (2003) The low gonadotropin-independent constitutive production of testicular testosterone is sufficient to maintain spermatogenesis. Proc Natl Acad Sci USA 100, 1369213697.
Submitted on December 19, 2003; accepted on May 11, 2004.
|