Molecular and clinical characterization of Y chromosome microdeletions in infertile men: a 10-year experience in Italy

CONTEXT: An explosive growth in Y chromosome long arm (Yq) microdeletion testing demand for male infertility occurred in the past few years. However, despite the progresses in the biology of this chromosome, a number of molecular and clinical concerns are not supported by definitive data. OBJECTIVE: The objective was to provide information on the type and prevalence of microdeletions in infertile males, indication for testing, genotype-phenotype correlation, sperm aneuploidies, and genetic counseling. DESIGN AND SETTING: We performed a prospective study from January 1996 to December 2005 in an academic clinic. PATIENTS: We studied 3073 consecutive infertile men, of which 625 were affected by nonobstructive azoospermia and 1372 were affected by severe oligozoospermia. Ninety-nine patients with microdeletions are described here. MAIN OUTCOME MEASURES: Yq microdeletions, seminal analysis, reproductive hormones, testicular cytology/histology, and sperm sex chromosomes aneuploidies were used as outcome measures. RESULTS: The prevalence of microdeletions was 3.2% in unselected infertile men, 8.3% in men with nonobstructive azoospermia, and 5.5% in men with severe oligozoospermia. Only 2 of 99 deletions were found in men with more than 2 million sperm/ml. No clinical data are useful to identify a priori patients with higher risk of Yq microdeletions. Most deletions are of the AZFc-b2/b4 subtype and are associated with variable spermatogenic phenotype, with sperm present in 72% of the cases. Complete AZFa and AZFb (P5/Proximal P1) deletions are associated with Sertoli cell-only syndrome and alterations in spermatocyte maturation, respectively, whereas partial deletions in these regions are associated with milder phenotype and frequent presence of sperm. Men with AZFc-b2/b4 deletions produce a higher percentage of sperm with nullisomy for the sex chromosomes and XY-disomy. CONCLUSIONS: This extensive clinical research expands the knowledge on genotype-phenotype relationships and confirms that the identification of Yq microdeletions has significant diagnostic and prognostic value, adding useful information for genetic counseling in these patients.     

Approach to the infertile man

INTRODUCTION: Infertility is one of commonest disorders to afflict young men and women. The evaluation of infertility is initiated typically after 1 yr of failure to conceive. DIAGNOSTIC EVALUATION: The couple should be evaluated together to determine whether the problem resides in the male partner, the female partner, or both. The objectives of evaluation are to exclude treatable conditions--gonadotropin deficiency, obstruction, and coital disorders--and identify those who are candidates for assisted reproductive technologies, those who are sterile and should consider adoption or artificial insemination using donor sperm, and those who should undergo genetic screening. All infertile men should undergo several semen analyses according to the World Health Organization manual, as well as measurements of testosterone, LH, and FSH levels. Hormone measurements can help determine whether the patient has gonadotropin deficiency (low testosterone and low or inappropriately normal LH and FSH), primary testicular failure (low testosterone, elevated LH and FSH), spermatogenic failure (normal testosterone and LH, elevated FSH), or androgen resistance (high testosterone, elevated LH). A majority of infertile men have normal testosterone, LH, and FSH levels. Obstruction should be ruled out in azoospermic men with normal testosterone, LH, and FSH levels. GENETICS: Yq microdeletions are the most prevalent cause of spermatogenic failure in men with azoospermia or severe oligozoospermia. Infertile men with azoospermia or severe oligozoospermia should undergo karyotyping and testing for Yq microdeletions. Men with congenital absence of vas should be tested for cystic fibrosis transmembrane conductance regulator mutations. THERAPY: Gonadotropin therapy is highly effective in gonadotropin-deficient men. Intracytoplasmic sperm injection (ICSI) has emerged as the treatment of choice for idiopathic male factor infertility. However, ICSI is expensive and associated with a higher risk of multiple gestation, low birth weight, preterm delivery, perinatal complications, and chromosome aneuploidy than naturally conceived pregnancies. Men considering ICSI should be offered karyotyping, Yq microdeletion testing, and genetic counseling by counselors experienced in reproductive disorders.     

Y chromosome microdeletions and alterations of spermatogenesis

Three different spermatogenesis loci have been mapped on the Y chromosome and named "azoospermia factors" (AZFa, b, and c). Deletions in these regions remove one or more of the candidate genes (DAZ, RBMY, USP9Y, and DBY) and cause severe testiculopathy leading to male infertility. We have reviewed the literature and the most recent advances in Y chromosome mapping, focusing our attention on the correlation between Y chromosome microdeletions and alterations of spermatogenesis. More than 4,800 infertile patients were screened for Y microdeletions and published. Such deletions determine azoospermia more frequently than severe oligozoospermia and involve especially the AZFc region including the DAZ gene family. Overall, the prevalence of Y chromosome microdeletions is 4% in oligozoospermic patients, 14% in idiopathic severely oligozoospermic men, 11% in azoospermic men, and 18% in idiopathic azoospermic subjects. Patient selection criteria appear to substantially influence the prevalence of microdeletions. No clear correlation exists between the size and localization of the deletions and the testicular phenotype. However, it is clear that larger deletions are associated with the most severe testicular damage. Patients with Y chromosome deletions frequently have sperm either in the ejaculate or within the testis and are therefore suitable candidates for assisted reproduction techniques. This possibility raises a number of medical and ethical concerns, since the use of spermatozoa carrying Y chromosome deletions may produce pregnancies, but in such cases the genetic anomaly will invariably be passed on to male offspring.     

Y chromosome microdeletions in cryptorchidism and idiopathic infertility.

To clarify whether cryptorchidism might be the expression of an intrinsic congenital testicular abnormality, we investigated the frequency of Y chromosome long arm (Yq) microdeletions in unilateral excryptorchid subjects manifesting an important bilateral testiculopathy. Microdeletion analysis of Yq was performed by polymerase chain reaction in the following subjects: 40 unilateral excryptorchid patients with azoospermia or severe oligozoospermia due to a bilateral severe testiculopathy (Sertoli cell-only syndrome or severe hypospermatogenesis); 20 unilateral excryptorchid men with moderate oligozoospermia and a normal testicular cytological picture in the contralateral testis; 110 patients affected by idiopathic severe primary testiculopathies; 20 patients affected by idiopathic moderate testiculopathy; and, as controls, 50 patients affected by known causes of testiculopathy and 100 fertile men. Eleven of 40 (27.5%) unilateral excryptorchid patients affected by bilateral testiculopathy and 28 of 110 (25.4%) patients affected by idiopathic severe primary testiculopathy showed Yq microdeletions, whereas no microdeletions were found in all the other subjects, nor in male relatives of patients with deletions. Microdeletions were located in different parts of Yq, including known regions involved in spermatogenesis (DAZ and RBM, AZFa, b, and c) and other loci still poorly defined. No difference in localization of deletions was evident between cryptorchid and idiopathic patients. Microdeletions in Yq may be responsible for severe bilateral testicular damage that could be phenotypically expressed by unilateral cryptorchidism, as well as by idiopathic infertility.     

Effects of transmission of Y chromosome AZFc deletions

Deletions of specific regions on the Y chromosome cause male infertility. Recent advances in infertility treatment allow Y chromosome deletions to be transmitted to male offspring with the assumption that there will be no clinical consequences other than infertility in adult life. We screened 12 patients, who had a 45X/46XY karyotype and presented with Turner stigmata or sexual ambiguities, or both, for Y chromosome microdeletions with PCR. A third of these patients had Y chromosome microdeletions of distal Yq, the most common microdeletion seen in infertile men with azoospermia or severe oligozoospermia. Transmission of Y chromosome microdeletions could potentially have severe clinical consequences other than male infertility, such as the development of sexual ambiguities and Turner stigmata.     

Inhibin B: a marker for the functional state of the seminiferous epithelium in patients with azoospermia factor C microdeletions

Testicular production of inhibin B is believed to be dependent on the presence of germ cells within the seminiferous tubules. However, this association has recently been questioned in patients with deletions of azoospermia factor (AZF) on the Y chromosome. We have addressed this problem in 442 unselected infertile/subfertile patients (excluding obstructive and iatrogenic forms) who were analyzed for Yq microdeletions. AZFc microdeletions were found in 16 patients (3.8% of the total infertile group, but 9% of the subgroup with azoospermia or severe oligozoospermia with sperm concentration <1 x 10(6)/ml). The reproductive hormone profiles in patients with AZFc microdeletions were analyzed and compared with those in infertile patients without microdeletions and those in fertile control individuals. The mean serum inhibin B concentration in the patients with AZFc microdeletions (39.5 +/- 36.0 pg/ml) was significantly lower than that in the group of infertile patients without microdeletions (134.6 +/- 88.5 pg/ml). However, no significant difference was found compared with that in a matched group of infertile patients with comparably low sperm counts (72.6 +/- 75.5 pg/ml). Bilateral testicular biopsies in the AZFc-deleted patients revealed a variable histological pattern suggestive of a progressive depletion of seminiferous epithelium. An association between testicular pathology and the reproductive hormone profile was found; the more severe forms had lower inhibin B and higher FSH levels. Importantly, if Sertoli cell-only tubules were prevalent in the biopsy, inhibin B was invariably undetectable. In patients with bilateral spermatocytic arrest, inhibin B remained within the normal range, which is consistent with a role of spermatocytes in the maintenance of inhibin B secretion. Our data support the view that, in contrast to recently published data, in patients with AZF microdeletions the serum concentration of inhibin B is dependent upon the functional interaction between Sertoli cells and spermatocytes and/or spermatids.     

Sertoli cell function in infertile patients with and without microdeletions of the azoospermia factors on the Y chromosome long arm

Deletions of the azoospermia factors on the Y chromosome long arm are an important cause of male infertility, and they may involve germ cell-specific genes or ubiquitously expressed genes. To date, no clinical or hormonal parameters have yet been found to distinguish patients with and without Yq microdeletions. In particular, Sertoli cell function, as evaluated by inhibin B, has not yet been described. Our hypothesis was that microdeletions involving genes specifically expressed in germ cells should not alter Sertoli cell function. To do this, we have evaluated the testicular hormonal function in infertile patients affected by severe testiculopathies with and without Yq microdeletions, with particular emphasis on Sertoli cell function. We studied 102 well-characterized infertile patients; 27 had Yq microdeletions, and 75 were classified as idiopathic infertiles. Patients with Yq microdeletions had lower FSH and higher inhibin B plasma concentrations with respect to patients without microdeletions, suggesting that Sertoli cell function in Yq-deleted men is only partially altered. Furthermore, patients with deletions involving germ cell-specific genes had higher concentrations of inhibin B with respect to patients with deletions of ubiquitously expressed genes. These results suggested that a specific alteration of germ cells only partially influences Sertoli cell function. Hormonal status of patients without deletions suggested that in such cases the cause that has determined the spermatogenic defect may have damaged both Sertoli and germ cells. Inhibin B production in patients with Yq deletions was about 70% higher than the nondeleted patients, and the functional relationship between FSH and inhibin B was normally preserved. This study elucidated the multifactorial mechanisms underlying spermatogenic defects, where Sertoli cells may be normally functioning or damaged depending on the primary cause that has determined the testicular damage.     

Genetic abnormalities among severely oligospermic men who are candidates for intracytoplasmic sperm injection

Recent reports suggest that children born after intracytoplasmic sperm injection performed for male factor infertility are at increased risk of congenital malformations and chromosome aberrations. To explain these observations, we hypothesized that infertile men may be more likely than fertile men to have genetic abnormalities. We studied 750 severely oligozoospermic men (sperm count <5 million/ml) who were candidates for intracytoplasmic sperm injection, and 303 fertile men. We analyzed the peripheral blood karyotype, the Y chromosome long arm for detection of microdeletions in the azoospermia factors, and mutations in the cystic fibrosis gene and the androgen receptor gene. We also analyzed sperm for chromosome aneuploidies among the 421 men who subsequently entered the in vitro fertilization program. A total of 104 genetic abnormalities were diagnosed, corresponding to a frequency of 13.9% (104 of 750). Chromosomal aberrations were present in 5.6% (42 of 750) of infertile men and 0.3% of controls (one of 295), and they were in most cases alterations of the sex chromosomes. Y chromosome long-arm microdeletions were detected in 6.0% (45 of 750) of infertile men and most frequently included the azoospermia factor c, whereas no cases were found in controls (zero of 210). Mutations in the cystic fibrosis gene were diagnosed in 1.2% (nine of 750) of infertile men and 1.0% of controls (three of 303), and mutations in the androgen receptor gene were found in 1.1% (eight of 750) of infertile men and none of the 188 controls. Sperm sex chromosome aneuploidies were increased in men with karyotype anomalies and Y chromosome microdeletions as well as in subjects without constitutional genetic abnormalities. This study shows that the frequency of genetic alterations is increased among men with severe spermatogenic impairment. Genetic tests and genetic counseling should therefore be considered in oligozoospermic men who are candidates for intracytoplasmic sperm injection.     

Relationship of serum inhibin levels to serum follicle stimulating hormone and sperm production in normal men and men with varicoceles.

The purpose of this study was to examine the relationships between serum inhibin levels as measured by RIA and serum FSH and sperm concentration. Three groups of men were used for this study: group I, normal fertile men (n = 67); group II, fertile men with a varicocele (n = 57); and group III, infertile men with a varicocele (n = 21). There were no differences in mean serum inhibin levels between the three groups. The two groups of men with varicoceles exhibited higher serum FSH levels and FSH responses to GnRH than the normal men. Sperm counts in both groups II and III were significantly lower than group I. In the normal men there was an inverse correlation between baseline serum inhibin and serum FSH levels and GnRH stimulated FSH levels, r = -0.415 and 0.422, P less than 0.005, respectively. Furthermore, the normal men exhibited a positive correlation between serum inhibin measurements and sperm concentration and testicular volume, r = 0.35 and 0.26, P less than 0.01 and less than 0.05, respectively. In neither group of men with a varicocele were these relationships found. These data demonstrate that serum inhibin does correlate with FSH in a negative fashion, when the reproductive system is normal, as would be expected for a negative feedback factor. Finally, the relationship of serum inhibin levels to testicular size and sperm count in the normal men suggests that serum inhibin levels reflect to some extent the integrity of seminiferous tubule function.     

Analysis of sperm aneuploidy in infertile subjects after chemotherapy treatment

The continuing search for a cure for cancer has developed more aggressive therapies that may damage germ cells, leading to clinical disease in offspring of survivors. Standard therapy for the majority of cancer today consists in combinations of high doses of radiation and chemotherapy drugs. We investigated the effect of cancer treatments on the reproductive potential of men. Multicolor fluorescence in situ hybridization has been used to recognize chromosomes X, Y and 8 in sperm of 10 severely oligozoospermic subjects (sperm concentration < 5,000,000/mL) treated for cancer at least 5 years before the beginning of this study. As controls, we analyzed sperm aneuploidies in 20 fertile men (sperm concentration > 20,000,000/mL) and in 20 severe idiopathic oligozoospermic subjects (sperm concentration < 5,000,000/mL). In all subjects, X- and Y-bearing spermatozoa were present in a normal 1:1 ratio; nevertheless the frequency of 24,XY, 24,XX and 24,YY disomic sperm was significantly higher in patients treated for cancer and in idiopathic oligozoospermic subjects with respect to normozoospermic men. These results suggest that the increase in sperm aneuploidies in treated patients cannot be reported directly to precedent chemotherapy, but reflects the alteration of testicular structure, as in the case of severe idiopathic oligozoospermic subjects. With the advent of intra-cytoplasmic sperm injection, it is possible to offer the opportunity to conceive in men affected by severe oligozoospermia but it is also possible, when the spermatozoa of these subjects are used, to pass sex chromosome abnormalities on to the children. We therefore suggest caution before application of an artificial reproductive technique in severe oligozoospermic patients.     

Diagnostic value of bioactive FSH in male infertility

Bioactive FSH and immunoreactive FSH were determined in 193 infertile men and in 23 men with proven fertility using the Sertoli cell aromatase bioassay for bioactive FSH measurement and a two-site fluoroimmunoassay for immunoreactive FSH measurement. Overall bioactive and immunoreactive FSH levels correlated well (r = 0.74, p less than 0.001) but were significantly different from fertile men (bioactive FSH: 6.2 +/- 0.3 U/l; immunoreactive FSH: 4.1 +/- 0.4 U/l) in patients with Klinefelter's syndrome (24.1 +/- 6.1; 26.9 +/- 3.0), non-obstructive azoospermia (25.1 +/- 4.3; 22.2 +/- 4.0), maldescended testes (12.5 +/- 4.6; 14.6 +/- 1.6), and patients with severe oligozoospermia (11.9 +/- 1.2; 11.2 +/- 1.0). Infertile men with moderate oligozoospermia (8.9 +/- 1.5; 8.0 +/- 1.1) and normal sperm counts (9.6 +/- 1.1; 7.6 +/- 1.0) had insignificantly elevated bioactive FSH and immunoreactive FSH levels. Bioactive to immunoreactive FSH ratios were significantly reduced in all patient groups except for patients with normal sperm counts when compared with fertile men. A considerable number of patients exhibited elevated immunoreactive FSH concomitant with normal bioactive FSH levels. We conclude that 1. determination of immunoreactive FSH suffices for classification of patients; 2. bioactive to immunoreactive FSH ratios are reduced in infertile men; 3. some men might secrete immunoreactive FSH with reduced bioactivity.     

Y chromosome microdeletions and alterations of spermatogenesis,patient approach and genetic counseling

Infertility affects 15% of couples at reproductive age and human male infertility appears frequently idiopathic. The main genetic causes of spermatogenesis defect responsible for non-obstructive azoospermia and severe oligozoospermia are constitutional chromosomal abnormalities and microdeletions in the azoospermia factor region of the Y chromosome. The improvement of the Yq microdeletion screening method gave new insights in the mechanism responsible for the genesis of Yq microdeletions and for the consequences of the management of male infertility and genetic counselling in case of assisted reproductive technology.     

Spontaneous transmission from a father to his son of a Y chromosome microdeletion involving the deleted in azoospermia (DAZ) gene

Microdeletions of the so-called azoospermia factor (AZF) locus of the Y chromosome long arm (Yq) have been recognized as an etiological factor of severe oligozoospermia or azoospermia. Because of this, patients affected are generally infertile unless assisted reproductive techniques are used. We report the case of an oligozoospermic patient (proband) who inherited an extensive Yq microdeletion from his father through a spontaneous pregnancy. Leukocyte DNA was extracted using a commercially available kit. A total of 22 pairs of sequence-tagged site (STSs) based primers, spanning the entire AZF region, were used for the screening. Both the proband and his father carried a Yq microdeletion of the most distal AZF subregion (AZFc) where the deleted in azoospermia (DAZ) gene is located. The proband's father was a sixty-nine-yr-old man who had 3 other children, 2 females and 1 male. This case adds further evidence that the deletion of the DAZ gene is associated with different phenotypic expressions, including normal fertility.     

The pituitary-testicular axis in Klinefelter's syndrome and in oligo-azoospermic patients with and without deletions of the Y chromosome long arm

OBJECTIVE: The most frequent known genetic causes of severe oligospermia (< 5 million sperm/ml) or azoospermia in men are Klinefelter's syndrome (KS), and deletions in the Y chromosome long arm (Yq). We aimed to compare the function of the pituitary-testicular axis in patients with severe oligospermia or azoospermia, idiopathic or associated with Y chromosome deletions or Klinefelter's syndrome (KS) and in control subjects. PATIENTS: We studied 47 men with idiopathic oligo-azoospermia, 42 with Yq deletions (27 AZFc, 13 AZFb and two AZFa) and oligo-azoospermia, 14 with KS and 39 control subjects (total 143). MEASUREMENTS: We analysed levels of FSH, inhibin-B, LH, free testosterone and oestradiol in all subjects, and we calculated indexes based on those hormones. RESULTS: Inhibin-B levels were indistinguishable between patients with idiopathic and Y deletion-associated oligo-azoospermia, lowest in the Klinefelter's patients and highest in controls. FSH levels followed the reverse pattern: indistinguishable between patients with idiopathic and deletion-associated oligo-azoospermia, highest in Klinefelter's patients and lowest in controls. Oestradiol, free testosterone and the derived indeces were not different in subjects with Yq deletions compared to those with idiopathic oligo-azoospermia. Among the Yq-deleted patients, no measured or derived parameter differed between the subjects with AZFc deletion and those with AZFb deletion. When non-KS oligo-azoospermic patients were classified according to histology [Sertoli cell-only (SCO), n = 18 or non-Sertoli cell only (non-SCO), n= 18] and compared to KS patients, the hormonal pattern did not differ between SCO and non-SCO subjects, but levels in KS patients were significantly different for FSH, inhibin-B and the FSH/inhibin-B ratio. KS patients not only had lower inhibin-B than SCO and non-SCO oligo-azoospermic men, but also higher FSH levels for any given inhibin-B concentration. CONCLUSION: Our data show that Y-deleted patients do not have a lesser impairment of Sertoli cell function than patients with idiopathic oligo-azoospermia, and support the concept that the main determinant of inhibin-B production is the germ cell mass. Also, our results suggest that one or more other factors, apart from inhibin-B, may contribute to increased pituitary secretion of FSH in KS patients.     

PULSATILE GnRH-THERAPY IN OLIGOZOOSPERMIC MEN DOES NOT IMPROVE SEMINAL PARAMETERS DESPITE DECREASED FSH LEVELS

In order to evaluate GnRH administration for the treatment of infertile men with elevated serum FSH levels we administered GnRH in pulses via portable electronic infusion pumps initially to seven patients with low sperm counts and high FSH values over 12 weeks and later to nine further patients over 24 weeks who also underwent testicular biopsies. Fifty microlitres containing 5 micrograms GnRH were infused subcutaneously for 1 min every 120 min in the short-term study and every 90 min in the long-term study. Although FSH levels could be lowered in both groups of patients, none showed any improvement in sperm count or other seminal parameters. Therefore, pulsatile GnRH treatment cannot be recommended for therapy of severe oligozoospermia with elevated FSH levels.     

Y chromosome microdeletion screening in infertile men

Molecular analysis of Y-chromosomal microdeletions is routinely performed in the work-up of male infertility, in order to establish a diagnosis and for genetic counseling of the couple, since such microdeletions are transmitted to the male offspring. The review of published data shows that microdeletions are relatively common in patients with azoospermia or severe oligozoospermia, with wide variations in the reported deletion frequency depending mainly on the selection criteria. In general, patients with proximal deletions, involving the AZFa and/or the AZFb region show severe defects of spermatogenesis with a high prevalence of Sertoli cell only syndrome, while deletions of the distal AZFb and of the AZFc region can be compatible with residual spermatogenesis. Microdeletions have been only sporadically found in normozoospermic patients. For the time being the molecular analysis of microdeletions of the Y chromosome is indicated in infertile patients with sperm concentration <5 x 10(6)/ml and in men undergoing assisted reproduction techniques, since the genetic defect and, most probably, the related infertility problem will be transmitted to the sons.     

A clinical trial of 7 alpha-methyl-19-nortestosterone implants for possible use as a long-acting contraceptive for men

Several preparations of testosterone and its esters are being investigated alone or in combination with other gonadotropin-suppressing agents as possible antifertility agents for men. We studied the effectiveness of 7 alpha-methyl-19-nortestosterone (MENT) as an antispermatogenic agent in men. MENT has been shown to be more potent than testosterone and to be resistant to 5 alpha-reduction. For sustained delivery of MENT, we used a system consisting of ethylene vinyl acetate implants containing MENT acetate (Ac), administered subdermally. Thirty-five normal volunteers were recruited in 3 clinics and were randomly assigned to 1 of 3 doses: 1 (12 men), 2 (11 men), or 4 (12 men) MENT Ac implants. The initial average in vitro release rate of MENT Ac from each implant was approximately 400 micro g/day. Implants were inserted subdermally in the medial aspect of the upper arm under local anesthesia. The duration of treatment was initially designed to be 6 months. However, in 2 clinics the duration of treatment was extended to 9 months for the 2-implant group and to 12 months for the 4-implant group. Dose-related increases in serum MENT levels and decreases in testosterone, LH, and FSH levels were observed. Effects on sperm counts were also dose related. None of the subjects in the 1-implant group exhibited oligozoospermia (sperm count, <3 million/ml). Four subjects in the 2-implant group became oligozoospermic, 2 of whom reached azoospermia. Eight subjects in the 4-implant group reached azoospermia, with 1 exhibiting oligozoospermia, whereas 2 were nonresponders. Side effects generally seen with androgen administration, such as increases in erythrocyte count, hematocrit, and hemoglobin and a decrease in SHBG, were also seen in this study and were reversible. Changes in lipid parameters were moderate and transient. Liver enzymes showed small changes. This study demonstrates that MENT Ac, when administered in a sustained release fashion via subdermal implants, can inhibit spermatogenesis over a prolonged period after a single administration and has the potential to be used as a male contraceptive.     

Microdeletions of the Y chromosome in cryptorchidism and in idiopathic male infertility

We investigated the possible role of Y chromosome microdeletions in regions previously shown to be important for male germ cell development in unilateral ex-cryptorchid subjects manifesting important bilateral testiculopathy, in order to clarify whether cryptorchidism could be the expression of an intrinsic congenital testicular abnormality. Microdeletion analysis of the Y chromosome long arm was performed by polymerase chain reaction and confirmed by Southern blot in 40 selected unilateral ex-cryptorchid patients with azoospermia or severe oligozoospermia sustained by severe bilateral testiculopathy (Sertoli cell-only syndrome and severe hypospermatogenesis, respectively), 20 unilateral ex-cryptorchid men with moderate oligozoospermia and normal function of the descended testis, 110 patients affected by severe idiopathic primary testiculopathies, 20 patients affected by moderate idiopathic testiculopathy and, as controls, 50 patients affected by known causes of testiculopathy and 50 fertile controls. Eleven out of the 40 (27.5%) unilateral ex-cryptorchid patients affected by bilateral testiculopathy and 28 out of 110 (25.4%) patients affected by severe idiopathic primary testiculopathy showed microdeletions in the Y chromosome long arm, while all other subjects were normal. Male relatives of patients with deletions were also normal. Microdeletions were distributed in different regions of the Y chromosome long arm, including known regions involved in spermatogenesis (DAZ and RBM genes, AZFa, b and c regions) and other still poorly defined loci. No difference in localization of deletions was evident between ex-cryptorchid and idiopathic patients. Microdeletions in the Y chromosome may be responsible for bilateral severe testicular damage: the clinical consequence, other than idiopathic azoospermia and severe oligozoospermia, may also be unilateral cryptorchidism, probably due to altered testicular responses to mechanisms regulating testicular descent.     

A high frequency of Y chromosome deletions in males with nonidiopathic infertility.

Microdeletions of the long arm of the human Y chromosome are associated with spermatogenic failure and have been used to define three regions of Yq (AZFa, AZFb, and AZFc) that are recurrently deleted in infertile males. In a blind study we screened 131 infertile males (46 idiopathic and 85 nonidiopathic) for Y chromosome microdeletions. Nineteen percent of idiopathic males, with an apparently normal 46,XY chromosome complement had microdeletions of either the AZFa, AZFb, or AZFc region. There was no strict correlation between the extent or location of the deletion and the phenotype. The AZFb deletions did not include the active RBM gene. Significantly, a high frequency of microdeletions (7%) was found in patients with known causes of infertility and a 46,XY chromosome complement. These included deletions of the AZFb and AZFc regions, with no significant difference in the location or extent of the deletion compared with the former group. It is recommended that all males with reduced or absence sperm counts seeking assisted reproductive technologies be screened for deletions of the Y chromosome.