A nation-based population screening for azoospermia factor deletions in Greek-Cypriot patients with severe spermatogenic failure and normal fertile controls, using a specific study and experimental design

The Prevalence of Y-chromosome Microdeletions in Oligozoospermic Men: A Systematic Review and Meta-analysis of European and North American Studies

CONTEXT

European and North American guidelines recommend Y-chromosome microdeletion (YCM) screening in azoospermic and oligozoospermic men with sperm concentrations of <5 million sperm/ml; however, numerous studies have suggested that YCMs are rare when sperm concentrations are >1 million sperm/ml.

OBJECTIVE

We systematically reviewed and meta-analyzed European and North American studies to determine the prevalence of a complete YCM in oligozoospermic men with sperm concentrations of >0-1, >1-5, and >5-20 million sperm/ml, and to determine whether 1 or 5 million sperm/ml is the most appropriate sperm concentration threshold for YCM screening.

EVIDENCE ACQUISITION

A systematic review of MEDLINE, EMBASE, Cochrane Library, and ClinicalTrials.gov was performed for studies assessing the prevalence of a complete YCM in oligozoospermic men in European and North American studies.

EVIDENCE SYNTHESIS

Thirty-seven studies were identified during a systematic review (n = 12 492 oligozoospermic men). All complete YCMs in oligozoospermic men were AZFc microdeletions. Eighteen studies contained data conducive to meta-analysis (n = 10 866 men). Comparing the pooled estimated prevalence by sperm concentration, complete YCMs were significantly more common in men with sperm concentrations of >0-1 million sperm/ml (5.0% [95% confidence interval {CI}: 3.6-6.8%]) versus >1-5 million sperm/ml (0.8% [95% CI: 0.5-1.3%], p < 0.001). YCMs were similar in men with sperm concentrations of >1-5 and >5-20 million sperm/ml (0.8% [95% CI: 0.5-1.3%] vs 0.5% [95% CI: 0.2-0.9%], p = 0.14).

CONCLUSIONS

In Europe and North America, the majority of YCMs occur in men with sperm concentrations of ≤1 million sperm/ml, with <1% identified in men with >1 million sperm/ml. Male infertility guidelines for North America and Europe should reconsider the sperm concentration screening thresholds to recommend testing for YCMs only for men with sperm concentrations of <1 million sperm/ml.

PATIENT SUMMARY

Complete Y-chromosome microdeletions (YCMs) are rare in men with >1 million sperm/ml. Routine screening for YCMs should occur only if sperm concentration is ≤1 million sperm/ml.

Microdeletions at DYS448 and DYS387S1 associate with increased risk of male infertility

Male infertility affects many people of reproductive age. Diagnosis and therapies based on descriptive semen parameters have helped some of the infertility patients; however, further progress in reproductive therapy demands a better understanding of the molecular and genetic causes for male infertility. Although Y chromosome microdeletions have been a hot subject of genetic studies on male infertility, the relationship between male infertility and microdeletions at Y chromosome loci DYS448, DYS387, and DYS627 remains unclear. Here we analyzed the microdeletions at these three loci in 200 infertility male patients and 200 healthy subjects and showed that microdeletions at DYS448 and DYS387 correlate with male infertility. Our results suggest that genetic analyses of Y chromosome loci DYS448 and DYS387 can be genetic markers for reproductive diagnosis and therapy.

High frequency of TTTY2-like gene-related deletions in patients with idiopathic oligozoospermia and azoospermia

Genes located on Y chromosome and expressed in testis are likely to be involved in spermatogenesis. TTTY2 is a Y-linked multicopy gene family of unknown function that includes TTTY2L2A and TTTY2L12A at Yq11 and Yp11 loci respectively. Using PCR amplification, we screened for TTTY2L2A- and TTTY2L12A-associated deletions, in 94 Greek men with fertility problems. Patients were divided into three groups as following: group A (n = 28) included men with idiopathic moderate oligozoospermia, group B (n = 34) with idiopathic severe oligozoospermia and azoospermia, and group C (n = 32) with oligo- and azoospermia of various known etiologies. No deletions were detected in group C patients and 50 fertile controls. However, two patients from group A had deletions in TTTY2L2A (7.1%) and six in TTTY2L12A (21.4%), whereas from group B, four patients had deletions in TTTY2L2A (11.8%) and 10 in TTTY2L12A (29.4%). In addition, five patients from both groups A and B (8%) appeared to have deletions in both studied TTTY2 genes, although these are located very far apart. These results indicate that the TTTY2 gene family may play a significant role in spermatogenesis and suggest a possible mechanism of nonhomologous recombinational events that may cause genomic instability and ultimately lead to male infertility.

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.

Clinical consequences of microdeletions of the Y chromosome: the extended Münster experience

A total of 3179 patients were screened for Y-chromosome microdeletions and 821 patients for partial AZFc deletions. Thirty-nine Y-chromosomal microdeletions were found (2.4% of men with <1 x 10(6)/ml spermatozoa): two AZFa, two AZFb, one AZFbc, one partial AZFb, one partial AZFb+c and 32 AZFc (b2/b4). Partial AZFc deletions were found in 45 patients (5.5%), mostly gr/gr deletions (n = 28). In patients with AZFc deletion, azoospermia was found in 53.1% and sperm concentrations of mostly <0.1 x 10(6)/ml were found in 46.9%. Semen analyses and FSH measurements showed no trend over time. Elongated spermatids were seen in 6/15 AZFc patients and bilateral Sertoli cell-only was found in 4/15. Testicular sperm extraction (TESE) was attempted in 10 patients and spermatozoa were found in six. Compared with infertile men matched by sperm concentration, no differences in hormonal and seminal parameters could be found in patients with AZFc or gr/gr deletions. It is concluded that: (i) frequency of AZF deletions in Germany is much lower than in other countries; (ii) AZFc deletions are associated with severe disturbances of spermatogenesis and TESE is not possible in half of these patients; (iii) AZFc and gr/ gr deletions are not associated with any clinical diagnostic parameter; (iv) and no trend is apparent over time.

Loss of the Y chromosome PAR2 region and additional rearrangements in two familial cases of satellited Y chromosomes: cytogenetic and molecular analysis

Two cases of rare structural aberrations of the Y chromosome were detected: a del(Y) (q12) chromosome in a child with mild dysmorphic features, obesity and psychomotor delay, and two identical satellited Y chromosomes (Yqs) in a normal twin, which were originally observed during routine prenatal diagnosis. In both cases a Yqs chromosome was detected in the father which had arisen from a reciprocal translocation involving the short arm of chromosome 15 and the heterochromatin of the long arm of the Y chromosome (Yqh). Cytogenetic and molecular studies demonstrated that in the reciprocal product of chromosomes 15 and Y PAR2 could not be detected, showing that PAR2 had been deleted. It is discussed whether the translocation of the short arm of an acrocentric chromosome to the heterochromatin of the long arm of the Y chromosome causes instability of this region which results either in loss of genetic material or interference with the normal mechanism of disjunction.

Frequency of Y chromosome microdeletions and chromosomal abnormalities in infertile Thai men with oligozoospermia and azoospermia

AIM

To investigate the possible causes of oligozoospermia and azoospermia in infertile Thai men, and to find the frequencies of Y chromosome microdeletions and cytogenetic abnormalities in this group.

METHODS

From June 2003 to November 2005, 50 azoospermic and 80 oligozoospermic men were enrolled in the study. A detailed history was taken for each man, followed by general and genital examinations. Y chromosome microdeletions were detected by multiplex polymerase chain reaction (PCR) using 11 gene-specific primers that covered all three regions of the azoospermic factor (AZFa, AZFb and AZFc). Fifty men with normal semen analysis were also studied. Karyotyping was done with the standard G- and Q-banding. Serum concentrations of follicle stimulating hormone (FSH), luteinizing hormone (LH), prolactin (PRL) and testosterone were measured by electrochemiluminescence immunoassays (ECLIA).

RESULTS

Azoospermia and oligozoospermia could be explained by previous orchitis in 22.3%, former bilateral cryptorchidism in 19.2%, abnormal karyotypes in 4.6% and Y chromosome microdeletions in 3.8% of the subjects. The most frequent deletions were in the AZFc region (50%), followed by AZFb (33%) and AZFbc (17%). No significant difference was detected in hormonal profiles of infertile men, with or without microdeletions.

CONCLUSION

The frequencies of Y chromosome microdeletions and cytogenetic abnormalities in oligozoospermic and azoospermic Thai men are comparable with similarly infertile men from other Asian and Western countries.