Transmission of de novo mutations of the deleted in azoospermia genes from a severely oligozoospermic male to a son via intracytoplasmic sperm injection

EAA/EMQN best practice guidelines for molecular diagnosis of Y-chromosomal microdeletions: State of the art 2023

Testing for AZoospermia Factor (AZF) deletions of the Y chromosome is a key component of the diagnostic workup of azoospermic and severely oligozoospermic men. This revision of the 2013 European Academy of Andrology (EAA) and EMQN CIC (previously known as the European Molecular Genetics Quality Network) laboratory guidelines summarizes recent clinically relevant advances and provides an update on the results of the external quality assessment program jointly offered by both organizations. A basic multiplex PCR reaction followed by a deletion extension analysis remains the gold-standard methodology to detect and correctly interpret AZF deletions. Recent data have led to an update of the sY84 reverse primer sequence, as well as to a refinement of what were previously considered as interchangeable border markers for AZFa and AZFb deletion breakpoints. More specifically, sY83 and sY143 are no longer recommended for the deletion extension analysis, leaving sY1064 and sY1192, respectively, as first-choice markers. Despite the transition, currently underway in several countries, toward a diagnosis based on certified kits, it should be noted that many of these commercial products are not recommended due to an unnecessarily high number of tested markers, and none of those currently available are, to the best of our knowledge, in accordance with the new first-choice markers for the deletion extension analysis. The gr/gr partial AZFc deletion remains a population-specific risk factor for impaired sperm production and a predisposing factor for testicular germ cell tumors. Testing for this deletion type is, as before, left at the discretion of the diagnostic labs and referring clinicians. Annual participation in an external quality control program is strongly encouraged, as the 22-year experience of the EMQN/EAA scheme clearly demonstrates a steep decline in diagnostic errors and an improvement in reporting practice.

Y-microdeletions: a review of the genetic basis for this common cause of male infertility

The human Y-chromosome contains genetic material responsible for normal testis development and spermatogenesis. The long arm (Yq) of the Y-chromosome has been found to be susceptible to self-recombination during spermatogenesis predisposing this area to deletions. The incidence of these deletions is estimated to be 1/4,000 in the general population but has been found to be much higher in infertile men. Currently, Y-microdeletions are the second most commonly identified genetic cause of male infertility after Klinefelter syndrome. This has led to testing for these deletions becoming standard practice in men with azoospermia and severe oligospermia. There are three commonly identified Y-microdeletions in infertile males, termed azoospermia factor (AZF) microdeletions AZFa, AZFb and AZFc. With increased understanding and investigation of this genetic basis for infertility a more comprehensive understanding of these deletions has evolved, with several other deletion subtypes being identified. Understanding the genetic basis and pathology behind these Y-microdeletions is essential for any clinician involved in reproductive medicine. In this review we discuss the genetic basis of Y-microdeletions, the various subtypes of deletions, and current technologies available for testing. Our understanding of this issue is evolving in many areas, and in this review we highlight future testing opportunities that may allow us to stratify men with Y-microdeletion associated infertility more accurately

EAA/EMQN best practice guidelines for molecular diagnosis of Y-chromosomal microdeletions: state-of-the-art 2013

The molecular diagnosis of Y-chromosomal microdeletions is a common routine genetic test which is part of the diagnostic workup of azoospermic and severe oligozoospermic men. Since 1999, the European Academy of Andrology (EAA) and the European Molecular Genetics Quality Network (EMQN) have been actively involved in supporting the improvement of the quality of the diagnostic assays by publication of the laboratory guidelines for molecular diagnosis of Y-chromosomal microdeletions and by offering external quality assessment trials. The present revision of the 2004 laboratory guidelines summarizes all the clinical novelties related to the Y chromosome (classic, partial and gene-specific deletions, genotype-phenotype correlations, methodological issues) and provides an update on the results of the quality control programme. These aspects also reflect the consensus of a large group of specialists present at a round table session during the recent Florence-Utah-Symposium on 'Genetics of male infertility' (Florence, 19-21 September, 2013). During the last 10 years the gr/gr deletion has been demonstrated as a significant risk factor for impaired sperm production. However, the screening for this deletion type in the routine diagnostic setting is still a debated issue among experts. The original basic protocol based on two multiplex polymerase chain reactions remains fully valid and appropriate for accurate diagnosis of complete AZF deletions and it requires only a minor modification in populations with a specific Y chromosome background. However, in light of novel data on genotype-phenotype correlations, the extension analysis for the AZFa and AZFb deletions is now routinely recommended. Novel methods and kits with excessively high number of markers do not improve the sensitivity of the test, may even complicate the interpretation of the results and are not recommended. Annual participation in an external quality control programme is strongly encouraged. The 12-year experience with the EMQN/EAA scheme has shown a steep decline in diagnostic (genotyping) error rate and a simultaneous improvement on reporting practice.

Genomics and genetics of human and primate y chromosomes

In mammals, the Y chromosome plays the pivotal role in male sex determination and is essential for normal sperm production. Yet only three Y chromosomes have been completely sequenced to date--those of human, chimpanzee, and rhesus macaque. While Y chromosomes are notoriously difficult to sequence owing to their highly repetitive genomic landscapes, these dedicated sequencing efforts have generated tremendous yields in medical, biological, and evolutionary insight. Knowledge of the complex structural organization of the human Y chromosome and a complete catalog of its gene content have provided a deeper understanding of the mechanisms that generate disease-causing mutations and large-scale rearrangements. Variation among human Y-chromosome sequences has been an invaluable tool for understanding relationships among human populations. Comprehensive comparisons of the human Y-chromosome sequence with those of other primates have illuminated aspects of Y-chromosome evolutionary dynamics over much longer timescales (>25 million years compared with 100,000 years). The future sequencing of additional Y chromosomes will provide a basis for a more comprehensive understanding of the evolution of Y chromosomes and their roles in reproductive biology.

AZFc deletions and spermatogenic failure: a population-based survey of 20,000 Y chromosomes

Deletions involving the Y chromosome's AZFc region are the most common known genetic cause of severe spermatogenic failure (SSF). Six recurrent interstitial deletions affecting the region have been reported, but their population genetics are largely unexplored. We assessed the deletions' prevalence in 20,884 men in five populations and found four of the six deletions (presented here in descending order of prevalence): gr/gr, b2/b3, b1/b3, and b2/b4. One of every 27 men carried one of these four deletions. The 1.6 Mb gr/gr deletion, found in one of every 41 men, almost doubles the risk of SSF and accounts for ∼2% of SSF, although <2% of men with the deletion are affected. The 1.8 Mb b2/b3 deletion, found in one of every 90 men, does not appear to be a risk factor for SSF. The 1.6 Mb b1/b3 deletion, found in one of every 994 men, appears to increase the risk of SSF by a factor of 2.5, although <2% of men with the deletion are affected, and it accounts for only 0.15% of SSF. The 3.5 Mb b2/b4 deletion, found in one of every 2,320 men, increases the risk of SSF 145 times and accounts for ∼6% of SSF; the observed prevalence should approximate the rate at which the deletion arises anew in each generation. We conclude that a single rare variant of major effect (the b2/b4 deletion) and a single common variant of modest effect (the gr/gr deletion) are largely responsible for the AZFc region's contribution to SSF in the population.

SCREENING OF Y CHROMOSOME MICRODELETIONS IN TUNISIAN INFERTILE MEN

The aim of this study was to establish the prevalence of Y chromosomal microdeletions in infertile Tunisian men. Three groups of infertile men, 65 normospermic, 53 oligozoospermic and 45 azoospermic, were tested for Yq microdeletions detection by multiplex polymerase chain reaction (PCR) using specific Y chromosome AZF regions tagged site markers (STS). One group of 13 healthy men was used as the control group. Six STS were tested (2 in each AZF region). The general prevalence of AZF microdeletions was 16%; in azoospermia and severe oligospermia groups, it was higher (29% and 30.5%, respectively). Significant differences were found with moderate oligospermic and normospermic groups (p < 0,05). AZFc microdeletions were the most frequent, and 55% of AZFc deleted patients were oligospermic. No deletions were detected in the control group. These results add to the growing literature data, showing that microdeletions of the Y chromosome is an important cause of severe spermatogenetic defect and confirm that deletion in AZFc region is the most common and is compatible with residual spermatogenesis.

Male infertility: role of genetic background

Male infertility represents one of the clearest examples of a complex disease with a substantial genetic basis. Numerous male mouse models, mutation screening and association studies reported over the last few years reveal the high prevalence of genetic causes of spermatogenic impairment, accounting for 10-15% of severe male infertility, including chromosomal aberrations and single gene mutations. Natural selection prevents the transmission of mutations causing infertility, but this protective mechanism may be overcome by assisted reproduction techniques. Consequently, the identification of genetic factors is important for appropriate management of the infertile couple. However, a large proportion of infertile males are diagnosed as idiopathic, reflecting poor understanding of the basic mechanisms regulating spermatogenesis and sperm function. Furthermore, the molecular mechanisms underlying spermatogenic damage in cases of genetic infertility (for example Yq microdeletions) are not known. These problems can be addressed only by large scale association studies and testicular or spermatozoal expression studies in well-defined alterations of spermatogenesis. It is conceivable that these studies will have important diagnostic and therapeutic implications in the future. This review discusses the genetic causes of male infertility known to date, the genetic polymorphisms possibly associated with male infertility, and reports novel results of global gene expression profiling of normal human testis by microarray technology.

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.

A frequent Y chromosome b2/b3 subdeletion shows strong association with male infertility in Han-Chinese population

BACKGROUND

Azoospermia factor c (AZFc) subdeletions were reported to be significant risk factors for spermatogenesis. In this study, we assessed the occurrence of classical AZF deletions and AZFc subdeletions and their impact on male infertility in a Han-Chinese population.

METHODS

This study analysed a population of 699 subjects, including 451 idiopathic infertile patients with a range of fertility disorders and 248 fertile controls, using a retrospective design. Deletions were identified by multiplex PCR.

RESULTS

The prevalence and phenotypes of the classical AZF deletions were similar to previous studies. Subdeletions of the AZFc region in patients showed similar overall frequencies in all sperm concentration categories of gr/gr (7.0%) and b2/b3 (8.9%). For controls, these subdeletions were also found with a prevalence of gr/gr (7.7%) and b2/b3 (3.2%). b1/b3 deletions were not found either in the patients or in the controls.

CONCLUSION

Our data showed a higher frequency of deletion events in this Han-Chinese population than in populations elsewhere in the world. The classical AZF deletions were the primary genetic factors for spermatogenic failure, while no significant association was found for AZFc subdeletions with sperm concentration. However, the b2/b3 subdeletion was significantly associated with idiopathic male infertility (odds ratio, 2.93; 95% confidence interval 1.34-6.39) (P = 0.005), indicating a potential impairment of male fertility.

Sperm cryopreservation in male infertility due to genetic disorders

Certain chromosomal and genetic anomalies, such as Klinefelter syndrome (47,XXY) and Y chromosome microdeletions, have been reported as potential causes of a progressive impairment of spermatogenesis. In these cases cryoconservation of ejaculated or testicular sperm represent a valuable tool for the preservation of fertility. However, dealing with genetic disorders, the transmission of genetic anomalies has to be taken into consideration. It is therefore important to be aware about the clinical importance and the related genetic risks of these anomalies. In this article we describe the clinical significance of these diseases.

Reevaluation of azoospermic factor c microdeletions using sequence-tagged site markers with confirmed physical positions from the GenBank database

OBJECTIVE

To investigate microdeletions and palindrome complexes in the azoospermic factor (AZF) c regions of the Y chromosome, by polymerase chain reaction (PCR) with sequence-tagged site (STS) markers with known physical positions, after verification of the exact physical locations of candidate STSs and exclusion of those that would give ambiguous results on PCR.

DESIGN

Retrospective STS deletion study in infertile Japanese men.

SETTING

University hospital and reproductive clinic.

PATIENT(S)

A total of 410 men with nonobstructive azoospermia and severe oligospermia (sperm concentrations of <5 x 10(6)/mL).

INTERVENTION(S)

Polymerase chain reaction was performed for all STS markers confirmed to be physically located in the partial AZFb and AZFc regions of the Y chromosome. All STSs were retrieved from the University of California at Santa Cruz database, and their location and specificity were verified.

MAIN OUTCOME MEASURE(S)

Presence or absence of appropriately sized PCR products.

RESULT(S)

Sixty-nine markers were retrieved, 32 of which were not specific to the long arm of the Y chromosome (Yq). The markers retained for test use were contiguous deletions classified as P1+P2 (AZFc) or P3 proximal/P1 (AZFb+c). The prevalence of accurately mapped microdeletions was 5.1% (21 of 410) in this patient population.

CONCLUSION(S)

Although noncontiguous deletions were observed, considerable confusion remained until the genome sequence was finally determined because many of the STSs were either repetitive sequences or polymorphic between individuals or races.

Intracytoplasmic sperm injection may lead to vertical transmission, expansion, and de novo occurrence of Y-chromosome microdeletions in male fetuses

Y-chromosome microdeletion in male fetuses conceived by intracytoplasmic sperm injection (ICSI) was screened by polymerase chain reaction for sequence-tagged sites in azoospermia factor (AZF)-b and AZFc regions. Treatment with ICSI may lead to vertical transmission, expansion, and de novo Y-chromosome microdeletion in male fetuses.

Role of the AZFd locus in spermatogenesis

To determine the prevalence of Y-chromosome microdeletions among infertile men and to correlate the clinical presentation of the men with specific deletions, microdeletion analysis in 53 infertile men (30 nonobstructive azoospermic, 23 severely oligozoospermic patients), and 100 age-matched, fathered normospermic men who had fathered children was performed by the multiplex PCR with 18 different Y-chromosome-specific STS primer sets, spanning the AZFa, AZFb, AZFd, and AZFc regions. Detection of the same locus deletion of the AZFd region in three cases indicated the possible importance of the genes located in this region in spermatogenesis.

Y chromosome microdeletions: are they implicated in teratozoospermia?

BACKGROUND

Y chromosome microdeletions are known to impair spermatogenesis. Screenings for these microdeletions are performed mostly in patients with sperm count abnormalities.

METHODS

We have screened the Y chromosome of 80 infertile patients with sperm morphological abnormalities. DNA from sperm, peripheral blood or single sperm following multiple displacement amplification (MDA) was utilized to amplify 20 specific sequence-tagged sites (STS) by PCR.

RESULTS

Y chromosome microdeletions were detected in sperm DNA from four of the teratozoospermic patients; while none of the 53 men with normal sperm morphology had any deletions. Two of the four patients with deletions also provided peripheral blood and a fresh semen sample. Both patients had none of the STS deleted in the peripheral blood DNA. Y chromosome microdeletion analysis in the MDA amplified SRY-positive single sperm DNA confirmed the presence of the same deletion in all 10 sperm for one patient and eight out of 10 sperm in the second patient.

CONCLUSIONS

Our observations suggest that some of the teratozoospermia might be related to gonadal mosaic Y chromosome microdeletions. Gonadal mosaicism can be a source of de novo transmissions of Y chromosome microdeletions. The application of MDA can yield enough DNA from a single sperm for genetic analyses.

Y chromosome and new concept of azoospermia factor

The completion of a draft sequence of the entire human genome in 2001 was followed by a complete sequencing of the Y chromosome in 2003. It is now possible to refer to a physical map of the Y chromosome. The Y chromosome can be classified into X-transposed, X-degenerate and ampliconic sequences depending on the origins of its sequences. In particular, the ampliconic sequences are complexes of massive palindrome structures in which sequences having higher than 99.9% homology are present symmetrically. Interestingly, palindromic repeats may undergo frequent gene conversion associated with intrachromosomal recombination and play an important role in the maintenance of the genetic materials of the Y chromosome. The azoospermia factor (AZF) region of the ampliconic region is the most probable candidate for spermatogenesis, and forms a palindrome structure. Thus, there is a limit in the detection of microdeletion using conventional sequence-tagged sites based on polymerase chain reaction because of their structure. It is now necessary to update the AZF concept. (Reprod Med Biol 2005; 4: 123-128).

EAA/EMQN best practice guidelines for molecular diagnosis of y-chromosomal microdeletions. State of the art 2004

Microdeletions of the Y chromosome are the second most frequent genetic cause of spermatogenetic failure in infertile men after the Klinefelter syndrome. The molecular diagnosis of Y-chromosomal microdeletions is routinely performed in the workup of male infertility in men with azoospermia or severe oligozoospermia. Since 1999, the European Academy of Andrology (EAA) and the European Molecular Genetics Quality Network (EMQN) support the improvement of the quality of the diagnostic assays by publication of the laboratory guidelines for molecular diagnosis of Y-chromosomal microdeletions and by offering external quality assessment trials. The present revision of the 1999 laboratory guidelines summarizes the results of a 'Best Practice Meeting' held in Florence (Italy) in October 2003. The basic protocol for microdeletion screening suggested in the 1999 guidelines proved to be very accurate, sensitive and robust. In the light of the recent advance in the knowledge of the Y chromosome sequence and of the mechanism of microdeletion it was agreed that the basic 1999 protocol, based on two multiplex polymerase chain reactions each covering the three AZF regions, is still fully valid and appropriate for accurate diagnosis.

Y chromosome assessment and its implications for the development of ICSI children

The aetiology of compromised spermatogenesis is often genetic in nature. There are only a few reports of father/son cohorts that have been evaluated to assess heritability of mutations associated with male factor infertility and the psychological well-being of the children. In the present study, multiple tissues were sampled from consenting male patients and their sons derived from intracytoplasmic sperm injection (ICSI) and underwent chromosomal and genetic analyses. Paediatric and psychological examinations were also conducted. In 87 men and 47 boys, 22 sequence tagged sites (STS) were analysed by multiplex PCR and deletion breakpoints were defined with additional loci. In one patient, the breakpoints map to the highly unstable palindrome-rich region within AZFb and proximal AZFc was investigated. A total of 86 blood, 26 semen, and 73 cheek cells samples were collected from adults, and 36 blood samples and 44 cheek cell specimens were obtained from the boys. Though all of the fathers had normal karyotypes, the incidence of chromosomal abnormalities in the somatic cells of male progeny was 8.3% (3/36). The incidence of germ line aneuploidy in these men was 0.5-2.8%. A CF mutation (Delta508) was detected in one of 87 men (1.2%) and microdeletions in Yq AZF were detected in 3.4% of 87 adults and in 2.1% of their sons (n = 47). In conclusion, screening for Y chromosome microdeletions provides crucial information in the counselling of couples seeking infertility treatment. Moreover, DNA extraction and Y deletion assessments of cheek cells provide a non-invasive approach. Inheritance of Yq deletions appears not to affect the psychological and physical development of children derived from ICSI.

Idiopathic non-obstructive azoospermia or severe oligozoospermia: a cross-sectional study in 61 Greek men

Idiopathic non-obstructive azoospermia or severe oligozoospermia (INOA) consists a special group of men characterized by eugonadism, primary infertility, low testicular volume, azoospermia or severe oligozoospermia and high follicle stimulating hormone values. Aims of this study were to describe the clinical, hormonal, sperm and histological characteristics of men with INOA and to define if and to what extend men with the INOA phenotype carry Y chromosome long arm (Yq) microdeletions. Sixty-three men with INOA were studied through clinical examination, spermiograms, hormonal profile, polymerase chain reaction for Yq microdeletions, karyotype and testicular fine-needle aspiration biopsy. Sixty-seven men with infertility of known causes and sixty fertile men served as controls. Men with INOA had significantly lower total testosterone levels than fertile men as well as higher prevalence of loss of libido, higher luteinizing hormone levels and lower sperm volume whereas men with infertility of known causes had intermediate values. The prevalence of Yq microdeletions was 3% in men with INOA, 3% in men with infertility of known causes (all of them with abnormal karyotype) and 0% in fertile men. In conclusion, men with INOA have more severe testiculopathy than these with infertility of known causes. These men may be at increased risk of developing partial androgen deficiency of the aging male.

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.

Prevalence of Y chromosome deletions in a Brazilian population of nonobstructive azoospermic and severely oligozoospermic men

We determined the prevalence of Y chromosome deletions in a population of 60 Brazilian nonobstructive azoospermic and severely oligozoospermic men. PCR-based screening of microdeletions was performed on lymphocyte DNA for the presence of 14 sequence-tagged sites (STS) located in the azoospermic factor (AZF) on the Yq chromosome. All STS were amplified efficiently in samples from 12 fertile men tested, but failed to be amplified in samples from fertile women, indicating the specificity of PCR conditions for Yq screening. Overall, 4 of the 60 infertile patients tested (6.7%) exhibited deletion of the Y chromosome, 2 of them being severely oligozoospermic patients (P10 and P32) and 2 azoospermic men (patients P47 and P57). Patients P47 and P57 presented larger deletions in the AZFa, AZFb and AZFc subregions, with apparent loss of Yq material evidenced by karyotype analysis. Patients P10 and P32 presented deletions confined to the AZFc region, involving the DAZ locus. Male relatives of patients P10 and P32 had no Y chromosome deletions and presented a normal karyotype, suggesting a de novo status of the deletions found. Our data add to the growing literature showing that microdeletions of the Y chromosome can be the cause of male idiopathic infertility.

Intracytoplasmic sperm injection: stiletto conception or a stab in the dark

To describe the importance of molecular and cellular analyses in intracytoplasmic sperm injection (ICSI) the authors review the literature on biological challenges in ICSI and associated techniques. Several matters can be proposed in molecular and cellular challenges in ICSI for safety and efficacy: (1) a reliable and convenient animal model for understanding the molecular and cellular basis of human ICSI must be established, and molecular and cellular analysis of the first cell cycle of human fertilization should be better understood; (2) a proper assay for human sperm function that contributes to the indication for ICSI should be developed; and (3) de novo and transmitted genetic security in ICSI should be examined.

Clinical characterization of 42 oligospermic or azoospermic men with microdeletion of the AZFc region of the Y chromosome, and of 18 children conceived via ICSI

BACKGROUND

Severe spermatogenic compromise may be the result of a Y-chromosomal deletion of the AZFc region. Prior studies are limited to relatively small numbers of AZFc-deleted men. In this study, we have fully characterized 42 infertile men with a Y chromosome microdeletion strictly confined to the AZFc region, and we report on 18 children conceived through the use of ICSI.

METHODS

A total of 42 oligospermic or azoospermic men had AZFc deletions. History, physical examination, karyotype, FSH, LH, testosterone, testis histology and results of ICSI using ejaculated or testis sperm were retrospectively accumulated in two academic clinical practices.

RESULTS

All men were somatically healthy. Karyotypes were 46,XY in all but two men. FSH, LH, testosterone and testis histology could not differentiate those with oligospermia or azoospermia, nor could they predict whether sperm could be found in harvested testis tissue. Paternal age was not increased. Sperm production appeared stable over time. The results of ICSI were not affected by the AZFc deletion. All but one of the offspring were healthy. The sons inherited the AZFc deletion with no increase in length.

CONCLUSIONS

AZFc-deleted men are somatically healthy, will most likely have useable sperm, will have stable sperm production over time and will have a good chance to experience biological paternity, but their sons will also be AZFc-deleted.

Y-chromosome microdeletions and cytogenetic findings in unselected ICSI candidates at a Danish fertility clinic

PURPOSE

To determine the frequency and type of microdeletions on the Y chromosome, and to evaluate cytogenetic findings in unselected ICSI candidates at a Danish Fertility Clinic.

METHODS

Genomic DNA was extracted from blood samples, which were collected prospectively from 400 ICSI candidates attending the Fertility Clinic at Aarhus University Hospital, Denmark. Twenty-five sequence tagged sites (STSs) spanning the azoospermia factor (AZF) regions of the Y chromosome were amplified in 5 multiplex sets to investigate Y microdeletions. Semen analysis, karyotype analysis, and histological evaluation of testicular biopsies were also performed.

RESULTS

Y microdeletions were detected in 3 (0.75%) of 400 unselected ICSI candidates. The frequency of Y microdeletions was found higher in azoospermic men (2%) than in oligozoospermic men (0.6%). Two patients having oligozoospermia had Y microdeletions in the AZFc region only, whereas the patient having azoospermia had Y microdeletions spanning the AZFb and AZFc regions. No microdeletion was detected in the AZFa region. Chromosomal anomalies were found in 6.1% of azoospermic men and in 2.7% of oligozoospermic men. A high frequency of cytogenetic abnormalities was found in normozoospermic men with fertilization failure (7.4%).

CONCLUSIONS

The frequency of Y microdeletions both in the unselected ICSI candidates and subgroups classified as azoospermic and oligozoospermic seems rather low compared to results of previous studies, which have been quite varying. It is possible that in addition to patient selection criteria, ethnical and geographical differences may contribute to these variations. Cytogenetic evaluation of normozoospermic men with fertilization failure seems indicated because of a high frequency of cytogenetic abnormalities.

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.

Absence of deleted in azoospermia (DAZ) genes in spermatozoa of infertile men with somatic DAZ deletions

OBJECTIVE

To determine the presence or absence of the deleted in azoospermia (DAZ) gene clusters in the Y-bearing spermatozoa in semen of severely oligozoospermic men or in testicular biopsy samples of azoospermic men with somatic DAZ deletions.

DESIGN

Prospective study.

SETTING

Academic hospital.

PATIENT(S)

Nineteen patients attending our clinics for therapeutic intracytoplasmic injection of sperm.

INTERVENTION(S)

Peripheral blood lymphocytes were used to obtain somatic DNA for analysis using the polymerase chain reaction. Analysis of chromosomes X and Y and the detection of the DAZ gene clusters were carried out with the fluorescence in situ hybridization technique in spermatozoa remaining after intracytoplasmic sperm injection.

MAIN OUTCOME MEASURE(S)

Presence or absence of the DAZ gene clusters in matched somatic DNA and Y-bearing spermatozoa.

RESULT(S)

Seven patients appeared to have a somatic DAZ deletion. Three-color fluorescence in situ hybridization showed that all Y-bearing spermatozoa examined from these men carried the same deletion.

CONCLUSION(S)

The DAZ deletions present in the seven men would all have been transmitted if they had fathered sons through artificial fertilization techniques using the sperm cells examined in this study.

Molecular detection of Y chromosome microdeletions: an Irish study

The region of the Y chromosome most critical for male fertility is called the azoospermia factor (AZF) region and it is located within subintervals five and six on the long arm of the Y chromosome. Several genes, all residing here, contribute to spermatogenesis and deletions in these genes are thought to be pathogenetically involved in some cases of male infertility associated with azoospermia or oligozoospermia. The aim of this study was to establish the prevalence of microdeletions in the AZF region of the Y chromosome in an Irish male population undergoing fertility treatment. To do this, we applied and compared two independent polymerase chain reaction (PCR) based screening methods, namely, a PCR protocol using several sequence-tagged site (STS) primer sets and a recently published multiplex PCR Y chromosome screening protocol. A total of 78 patients, attending the IVF unit at University College Hospital, Galway, were included in this study. Of them, 56 suffered from idiopathic azoospermic/oligozoospermic infertility. The remaining 22 patients had various conditions, which may have contributed to their infertility. A total of 50 age-matched normospermic men were included as controls. Two microdeletions were found; one in the AZFa region and one in AZFb region. These deletions were observed among the truly idiopathic cases. Further analysis was performed to study the extent of the deletions and it was confirmed that each deletion encompassed the respective AZF region including the AZF candidate gene.

Nonobstructive azoospermia

Nonobstructive azoospermia (NOA) remains a challenging condition in reproductive medicine to manage. The genetic basis of NOA related to partial deletions of the Y-chromosome has been intensely investigated. Such information is of prognostic value and allows more insightful genetic counseling of couples who opt for assisted reproductive technology. Testicular sperm extraction (TESE) combined with intracytoplasmic sperm injection has allowed many men with NOA to father their own biologic children. Although studies in the current literature support open testicular biopsy as the most reliable method to obtain testicular sperm, less invasive techniques such as testicular fine-needle aspiration and percutaneous needle biopsy are feasible alternatives in selected groups of patients. Measures to improve the efficacy of TESE, including the application of microsurgical techniques, are addressed. Other recent developments related to the management of NOA reviewed include processing of testicular tissue, cryopreservation of retrieved spermatozoa, in-vitro maturation of germ cells and microinjection of immature spermatogenic precursor cells.

Assisted reproductive technology (ART) in humans: facts and uncertainties

Since the first in vitro fertilization (IVF) in human, the number of patients using Assisted Reproductive Technologies (ART) has increased tremendously. ART technologies have increased in number and their spectrum has also widened. The first IVF babies are now more than 20 years old. All the retrospective analyses have demonstrated that the obstetrical and pediatrical impact has not really affected single births. The main problems observed occur with multiple pregnancies, including high costs for the couples and for society. The decrease in the number of embryos transferred has improved the situation and moreover does not impair the final results. IntraCytoplasmic Sperm Injection (ICSI) is a more debatable and questionable technique with a real negative genetic impact. The main problem is chromosome abnormalities more specifically related to the sex chromosomes. The question of a systematic genetic work-up on the patients entering ICSI programs is discussed. No negative impact of cryopreservation has been demonstrated even though some controversy arises from time to time. Pre-implantation Genetic Diagnosis (PGD) is now a interesting tool for patients carrying genetic defects. Blastocyst biopsy now has a future role in reproductive medicine. Gender selection through sperm sorting is also now a reality. As with the other developing bio-technologies related to reproduction, there are ethical questions. The decisions concerning these technologies do not belong solely to scientists but are rather a matter for society to decide.