Y-chromosome microdeletion and its effect on reproductive decisions in taiwanese patients presenting with nonobstructive azoospermia

A Role for Chromosomal Microarray Testing in the Workup of Male Infertility

Genetic analysis is a critical component in the male infertility workup. For male infertility due to oligospermia/azoospermia, standard guidelines recommend karyotype and Y-chromosome microdeletion analyses. A karyotype is used to identify structural and numerical chromosome abnormalities, whereas Y-chromosome microdeletions are commonly evaluated by multiplex PCR analysis because of their submicroscopic size. Because these assays often require different Vacutainer tubes to be sent to different laboratories, ordering is prone to errors. In addition, this workflow limits the ability for sequential testing and a comprehensive test result. A potential solution includes performing Y-microdeletion and numerical chromosome analysis-the most common genetic causes of oligospermia/azoospermia-by chromosomal microarray (CMA) and reflexing to karyotype as both assays are often offered in the cytogenetics laboratory. Such analyses can be performed using one sodium heparin Vacutainer tube sample. To determine the effectiveness of CMA for the detection of clinically significant Y-chromosome microdeletions, 21 cases with known Y microdeletions were tested by CytoScan HD platform. CMA studies identified all known Y-chromosome microdeletions, and in 11 cases (52%) identified additional clinically important cytogenetic anomalies, including six cases of 46, XX males, one case of isodicentric Y, two cases of a dicentric Y, and three cases of terminal Yq deletions. These findings demonstrate that this testing strategy would simplify ordering and allow for an integrated interpretation of test results.

Molecular and cytogenetic studies of 101 infertile men with microdeletions of Y chromosome in 1,306 infertile Korean men

OBJECTIVES

To determine the prevalence of Y chromosome microdeletions in infertile Korean men with abnormal sperm counts and to assess the clinical features and frequency of chromosomal abnormalities in Korean patients with microdeletions.

METHODS

A total of 1,306 infertile men were screened for Y chromosome microdeletions, and 101 of them had microdeletions. These 101 men were then retrospectively studied for cytogenetic evaluation, testicular biopsy and outcomes of IVF and ICSI.

RESULTS

The overall prevalence of Y chromosome microdeletions in infertile men was 7.7% (101/1,306). Most microdeletions were in the AZFc region (87.1%), including deletions of AZFbc (24.7%) and AZFabc (8.9%). All patients with AZFa, AZFbc and AZFabc deletions had azoospermia, whereas patients with an AZFc deletion usually had low levels of sperm in the ejaculate or in the testis tissues. Chromosomal studies were performed in 99 men with microdeletions, 36 (36.4%) of whom had chromosomal abnormalities. Among the infertile men with Y chromosome microdeletions in this study, the incidence of chromosomal abnormality was 48.6% in the azoospermic group and 3.7% in the oligozoospermic group. Among the 69 patients with microdeletions and available histological results, 100.0% of the azoospermic group and 85.7% of the oligozoospermic group had histological abnormalities. The frequency of both chromosomal abnormalities and histological abnormalities was higher in the azoospermic group compared to the oligozoospermic group. Thirty-four ICSI cycles with either testicular (n = 14) or ejaculated spermatozoa (n = 20) were performed in 23 couples with men with AZFc microdeletion. Thirteen clinical pregnancies (39.4%) were obtained, leading to the birth of 13 babies.

CONCLUSIONS

The study results revealed a close relationship between microdeletions and spermatogenesis, although IVF outcome was not significantly affected by the presence of the AZFc microdeletion. Nevertheless, Y chromosome microdeletions have the potential risk of being transmitted from infertile fathers to their offspring by ICSI. Therefore, before using ICSI in infertile patients with severe spermatogenic defects, careful evaluations of chromosomal abnormalities and Y chromosome microdeletions screening should be performed and genetic counseling should be provided before IVF-ET.

Use of ethnicity-specific sequence tag site markers for Y chromosome microdeletion studies

INTRODUCTION

Microdeletions in the azoospermia factor region on the long arm of Y chromosome are associated with spermatogenic failure. There are many markers for the diagnosis of Y chromosome microdeletion analysis, but in routine practice only a limited set of markers can be tested.

OBJECTIVE

The objectives of this study were to determine the frequency of Y chromosome microdeletion in idiopathic cases of male infertility in India, to attempt genotype-phenotype correlation, and to evaluate whether markers to be tested for diagnosis of Y chromosome microdeletion should be ethnicity specific.

METHODS

Microdeletions in the Y chromosome were analyzed in 200 infertile males. The six sequence tag site (STS) markers prescribed by the European Academy of Andrology (EAA) were used initially. Patients in whom no deletions were detected by use of these markers were tested by markers selected from other studies from India.

RESULTS

The STS markers prescribed by EAA detected deletions in only 6 (3%) of 200 infertile males. However, markers selected from previous Indian studies showed deletions in an additional 15 (7.5%) of infertile males. Overall, Y chromosome microdeletions were observed in 21 (10.5%) of 200 patients. Of these, 13 were cases of azoospermia and 8 were cases of severe oligospermia.

CONCLUSION

The markers prescribed by EAA alone are not suitable for the diagnosis of Y chromosome microdeletions in infertile males. The protocol for identification of Y chromosome microdeletions in cases of nonobstructive azoospermia/severe oligospermia would have to include a different set of STS markers.

Azoospermia factor and male infertility

Recently, work has shown that azoospermia factor (AZF) microdeletions result from homologous recombination between almost identical blocks in this gene region. These microdeletions in the Y chromosome are a common molecular genetic cause of spermatogenetic failure leading to male infertility. After completion of the sequencing of the Y chromosome, the classical definition of AZFa, AZFb, and AZFc was modified to five regions, namely AZFa, P5/proximal-P1, P5/distal-P1, P4/distal-P1, and AZFc, as a result of the determination of Y chromosomal structure. Moreover, partial AZFc deletions have also been reported, resulting from recombination in their sub-ampliconic identical pair sequences. These deletions are also implicated in a possible association with Y chromosome haplogroups. In this review, we address Y chromosomal complexity and the modified categories of the AZF deletions. Recognition of the association of Y deletions with male infertility has implications for the diagnosis, treatment, and genetic counseling of infertile men, in particular candidates for intracytoplasmic sperm injection.

A genetic survey of 1935 Turkish men with severe male factor infertility

Male factor infertility is the sole reason in approximately 25% of couples who suffer from infertility. Genetic factors such as numerical and structural chromosomal abnormalities and microdeletions of the Y chromosome might be the cause of poor semen parameters. The results of karyotype analyses and Y-chromosome microdeletions of 1935 patients with severe male factor infertility, which is the largest series from Turkey, were assessed retrospectively. The frequency of cytogenetic abnormalities among 1214 patients with non-obstructive azoospermia (NOA) and 721 patients with severe oligoasthenoteratozoospermia (OAT) were 16.40 and 5.83% respectively. The overall incidence of Y-chromosome microdeletion was 7.70%. The incidence of Y chromosome microdeletion in patients with NOA and OAT was 9.51 and 1.86% respectively. The abnormality rate increased with the severity of infertility. Some patients (n = 22) were carriers of both chromosomal abnormalities and Y-chromosome microdeletions. Results suggest the need for genetic screening and proper genetic counselling before initiation of assisted reproduction treatment.

DAZL protein expression in mouse preimplantation embryo

OBJECTIVE

To evaluate the expression pattern of Dazl (deleted in azoospermia-like) protein in the mouse preimplantation embryo.

DESIGN

Experimental study.

SETTING

Medical research laboratory in a university hospital.

ANIMAL(S)

Twenty female 28- to 35-day-old FVB mice.

INTERVENTION(S)

Embryo collection at 1.5, 2.5, and 3.5 days postcoitus (plug date, 0.5 d postcoitus) to examine the Dazl protein expression from the two-cell embryo to the blastocyst.

MAIN OUTCOME MEASURE(S)

Dazl protein expression was analyzed by immunofluorescent staining.

RESULT(S)

There is abundant expression of Dazl protein in the cytoplasm of the blastomere. Strong fluorescent signals of Dazl protein expression were found in preimplantation embryo cytoplasm, including two-cell, eight-cell, morula, and blastocyst.

CONCLUSION(S)

By using an antibody raised against mouse Daz-like protein (Dazl), we showed that Dazl protein is present in all cleaving stages of the preimplantation embryo. This is the first report on the protein expression of a Dazl gene during embryogenesis in mice. However, further study is needed to evaluate the molecular functional role of Dazl.

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.

Y chromosome microdeletions in Tunisian infertile males

AIM

To determine frequency of Y microdeletions in azoospermic and oligospermic Tunisian infertile males.

METHODS

A Sample of 146 Tunisian infertile males with a low sperm count (<5 x 10(6) sperms per mililiter) and normal karyotype was screened for Y chromosome microdeletions. 76 men were azoospermic and 70 men were oligospermic. Genomic DNA was isolated from blood and multiplex PCR was carried out with a set of 20 AZFa, AZFb and AZFc STS markers to detect the microdeletions as recommended by the European Academy of Andrology.

RESULTS

In 10/146 (6.85%) subjects AZF deletions were observed. Of these ten males with microdeletions, 9/10 subjects were azoospermic (90%), 1/10 was oligospermic (10%). Frequency of microdeletions in azoospermic men was 9/76 (11.84%). None of the patients showed isolated microdeletion in the AZFa region, but one azoospermic man had deletion in the AZFb region. Eight azoospermic patients and one oligospremic man have AZFc microdeletions. AZFc and AZFb were deleted in three azoospermic patients. AZFc, AZFb and AZFa were deleted in three azoospermic patients We estimate the sensitivity of the test comprising six STS in our sample to be 90%.

CONCLUSION

The incidence of Yq microdeletions in the study population of infertile Tunisian men falls within the range published in other countries. We suggest to analyze 9STS in the first step to detect efficiently Y microdeletions in our population.

Y-chromosomal microdeletions and partial deletions of the Azoospermia Factor c (AZFc) region in normozoospermic, severe oligozoospermic and azoospermic men in Sri Lanka

AIM

To assess for the first time the occurrence of Y chromosomal microdeletions and partial deletions of the Azoospermia Factor c (AZFc) region in Sri Lankan men and to correlate them with clinical parameters.

METHODS

In a retrospective study, we analyzed 96 infertile men (78 with non-obstructive azoospermia) and 87 controls with normal spermatogenesis. AZFa, AZFb, AZFc and partial deletions within the AZFc region were analyzed by multiplex polymerase chain reaction (PCR) according to established protocols.

RESULTS

No AZFa, AZFb or AZFc deletions were found in the control group. Seven patients in the group of infertile men were found to have deletions as following: one AZFa, two AZFc, two AZFbc and two AZFabc. The relative distribution of these patterns was significantly different compared with that found in the German population. Extension analysis confirmed that the deletions occurred according to the current pathogenic model. gr/gr deletions were found to be equally present both in the patients (n=4) and in the control group (n=4). One b2/b3 deletion was found in the patient group.

CONCLUSION

These results suggest that the frequency and pattern of microdeletions of the Y chromosome in Sri Lankan men are similar to those found in other populations and confirm that gr/gr deletions are not sufficient to cause spermatogenetic failure.

Genetics and assisted reproduction technology

In the past 20 years, a significant improvement has been shown in the treatment for infertility in both women and men through the development of in vitro fertilization (IVF) and intracytoplasmic sperm injection (ICSI). Only donated sperm could be previously used for treatment; now oocytes can also be donated. Furthermore, the combination of IVF and ICSI with advanced genetic methods has made preimplantation genetic diagnosis possible for many genetic conditions. These methods enable genetic testing of the early human embryo by using only a single cell, one blastomere biopsied from the embryo, as the sample from which the diagnosis of many chromosome rearrangements and other inherited diseases can be made. It has also been established that a considerable proportion of infertility is caused by genetic defects, which have several implications for infertility treatment. The purpose of this review is to give a concise introduction on how genetics is involved in assisted reproduction technology to specialists who may not be working in this particular field of gynecology, but who would need some knowledge of this for proper care of their patients.

Ring (Y) in two azoospermic men

We have identified two azoospermic men with r(Y) in 312 infertile men presenting with non-obstructive azoospermia or oligozoospermia. Their karyotypes were 45,X [9]/46,X, r(Y)(p11q11) [11] (case 1), and 46,X,r(Y)(p11q11) (case 2), respectively. In both cases, the Yp breakpoints were located within the pseudoautosomal region. Both cases had extensive deletions of azoospermia factors (AZFs). Case 1 also had deletion of the putative growth controlling gene (GCY) and the Yq breakpoint was located between sY741 and USP9Y. The Yq breakpoint was located between sY105 and sY109 in case 2. Both cases did not have Turner stigmata except short stature in case 1. By a combination of cytogenetic and molecular genetic tools, we showed r(Y) arose from breakage in both arms of the chromosome with subsequent fusion of two broken ends of the centric fragment to form a continuous ring. Spermatogenic defects in men with r(Y) may result from deletion of Y-linked AZFs combined with synaptic failure.

Diagnostic test for Y chromosome microdeletion screening in male infertility

Despite the current lack of understanding the mechanism of deleterious effects of Y chromosome microdeletions and their prognostic influence on male subfertility, the Y chromosome microdeletion test is widely used in the diagnostic evaluation of male subfertility. However, currently used diagnostic schemes have not been sufficiently evaluated for their diagnostic performance. The purpose of this study was to analyze a large database of published Y chromosome microdeletions to develop the optimal screening strategy for male subfertility. Therefore, we created a database from genetic and clinical data published in 52 peer-reviewed studies reporting on 512 cases with Y chromosome microdeletions. We developed a computerized procedure with the goal of minimizing the number of genetic markers included in the diagnostic set while maximizing the detection rate in patients with microdeletions. We estimate that 85.6% of all published Y chromosome microdeletions can be covered by a set of six genetic markers (sY84, sY127, sY152, RBMY1, sY147, sY254-DAZ). Inclusion of additional markers brings relatively little to the sensitivity of the test and is potentially related to the population origin.

Y Chromosome Microdeletions in Infertile Males from Andhra Pradesh, South India

Studies on the frequency of Y chromosome microdeletions were carried out in 70 idiopathic infertile males with normal karyotypes. Genomic DNA was isolated from blood and PCR analysis was carried out with AZFa, AZFb, and AZFc STS markers SY 84, SY 87, SY 127, SY 254, and SY 158 to detect the deletions. In 9/70 (12.8%) subjects AZF deletions were observed. In 4/9 (44.4%) subjects were azoospermic, 4/9 (44.4%) of cases were severe oligozoospermic, and 1/9 (11.1%) cases was oligozoospermic.

Recombination between palindromes P5 and P1 on the human Y chromosome causes massive deletions and spermatogenic failure

It is widely believed that at least three nonoverlapping regions of the human Y chromosome-AZFa, AZFb, and AZFc ("azoospermia factors" a, b, and c)-are essential for normal spermatogenesis. These intervals are defined by interstitial Y-chromosome deletions that impair or extinguish spermatogenesis. Deletion breakpoints, mechanisms, and lengths, as well as inventories of affected genes, have been elucidated for deletions of AZFa and of AZFc but not for deletions of AZFb or of AZFb plus AZFc. We studied three deletions of AZFb and eight deletions of AZFb plus AZFc, as assayed by the STSs defining these intervals. Guided by Y-chromosome sequence, we localized breakpoints precisely and were able to sequence nine of the deletion junctions. Homologous recombination can explain seven of these deletions but not the remaining two. This fact and our discovery of breakpoint hotspots suggest that factors in addition to homology underlie these deletions. The deletions previously thought to define AZFb were found to extend from palindrome P5 to the proximal arm of palindrome P1, 1.5 Mb within AZFc. Thus, they do not define a genomic region separate from AZFc. We also found that the deletions of AZFb plus AZFc, as assayed by standard STSs heretofore available, in fact extend from P5 to the distal arm of P1 and spare distal AZFc. Both classes of deletions are massive: P5/proximal-P1 deletions encompass up to 6.2 Mb and remove 32 genes and transcripts; P5/distal-P1 deletions encompass up to 7.7 Mb and remove 42 genes and transcripts. To our knowledge, these are the largest of all human interstitial deletions for which deletion junctions and complete intervening sequence are available. The restriction of the associated phenotype to spermatogenic failure indicates the remarkable functional specialization of the affected regions of the Y chromosome.

Gene-based screening for Y chromosome deletions in Taiwanese men presenting with spermatogenic failure

OBJECTIVE

To develop a simple and rapid protocol for detecting deletions of the Y chromosome and to evaluate the feasibility of gene-based screening in men with spermatogenic failure.

DESIGN

Prospective case study.

SETTING

University-based reproductive clinics and genetics laboratory.

PATIENT(S)

Two hundred two infertile men presenting with severe oligozoospermia and nonobstructive azoospermia.

INTERVENTION(S)

Fifteen gene-specific primers were used to detect deletions of Y chromosome genes in men with spermatogenic failure. A multiplex polymerase chain reaction amplification system was developed to facilitate rapid screening. Another 24 markers for sequence-tagged sites (STS) were used to ensure the adequacy of gene-based screening.

MAIN OUTCOME MEASURE(S)

Detection of deletions of Y chromosome genes.

RESULT(S)

Of 180 patients evaluated, 19 (10.6%) had deletions of one or more genes, including DFFRY, DBY, RBM1, DAZ, CDY1, and BPY2. A second round of STS-based screenings did not show an increase in the deletion rate but more clearly defined the extent of deletion in 14 of the 19 patients. In most patients, deletions detected by gene-based screening were similar to those detected by STS markers.

CONCLUSION(S)

Gene-based screening with multiplex polymerase chain reaction is a rational alternative for detecting deletions of Y chromosome genes in infertile men.