Gene copy number alterations in the azoospermia-associated AZFc region and their effect on spermatogenic impairment

Cytogenetics investigation in 151 Brazilian infertile male patients and genomic analysis in selected cases: experience of 14 years in a public genetic service

OBJECTIVES

Male infertility accounts for approximately 30% of cases of reproductive failure. The characterization of genetic variants using cytogenomic techniques is essential for the adequate clinical management of these patients. We aimed to conduct a cytogenetic investigation of numerical and structural rearrangements and a genomic study of Y chromosome microdeletions/microduplications in infertile men derived from a single centre with over 14 years of experience.

RESULTS

We evaluated 151 infertile men in a transversal study using peripheral blood karyotypes and 15 patients with normal karyotypes through genomic investigation by multiplex ligation-dependent probe amplification (MLPA) or polymerase chain reaction of sequence-tagged sites (PCR-STS) techniques. Out of the 151 patients evaluated by karyotype, 13 presented chromosomal abnormalities: two had numerical alterations, and 11 had structural chromosomal rearrangements. PCR-STS detected a BPY2 gene region and RBMY2DP pseudogene region microdeletion in one patient. MLPA analysis allowed the identification of one patient with CDY2B_1 and CDY2B_2 probe duplications (CDY2B and NLGN4Y genes) and one patient with BPY2_1, BPY2_2, and BPY2_4 probe duplications (PRY and RBMY1J genes).

Detection of AZFc gene deletion in a cohort of Egyptian patients with idiopathic male infertility

BACKGROUND

The deletions of azoospermic factor regions (AZF) are considered risk factor of spermatogenic failure. AZF duplications or complex copy number variants (CNVs) were rarely studied because STS-PCR could not always detect these changes. The application of multiplex ligation-dependent probe amplification (MLPA) as a valuable test for detection of the deletion and or duplication was introduced to investigate the AZF sub-region CNVs. The MLPA technique is still not applied on a large scale, and the publications in this area of research are limited. The aim of this work was to evaluate the efficacy of MLPA assay to detect AZF-linked CNVs in idiopathic spermatogenic failure patients and to evaluate its importance as a prognostic marker in the reproduction outcome.

RESULTS

Forty infertile men (37 with azoospermia and 3 with severe oligozoospermia) and 20 normal fertile men were subjected to thorough clinical, pathological, and laboratory assessment, chromosomal study, MLPA, STS-PCR assays, histopathology study, and testicular sperm retrieval (TESE). Out of the 40 patients, 7 patients have shown CNV in the AZFc region, 6 patients have partial deletion, and one patient has partial duplication. Only one of the normal control has AZFc duplication. STS-PCR was able to detect the deletion in only 4 out of the 7 positive patients and none of the control.

CONCLUSION

We concluded that MLPA should be applied on a larger scale for the detection of Y chromosome microdeletion as a rapid, efficient, and cheap test.

Practical guidance to reduce radiation exposure in electrophysiology applying ultra low-dose protocols: a European Heart Rhythm Association review

Interventional electrophysiology offers a great variety of treatment options to patients suffering from symptomatic cardiac arrhythmia. Catheter ablation of supraventricular and ventricular tachycardia has globally evolved a cornerstone in modern arrhythmia management. Complex interventional electrophysiological procedures engaging multiple ablation tools have been developed over the past decades. Fluoroscopy enabled interventional electrophysiologist throughout the years to gain profound knowledge on intracardiac anatomy and catheter movement inside the cardiac cavities and hence develop specific ablation approaches. However, the application of X-ray technologies imposes serious health risks to patients and operators. To reduce the use of fluoroscopy during interventional electrophysiological procedures to the possibly lowest degree and to establish an optimal protection of patients and operators in cases of fluoroscopy is the main goal of modern radiation management. The present manuscript gives an overview of possible strategies of fluoroscopy reduction and specific radiation protection strategies.

Analysis of the correlation between gene copy deletion in the AZFc region and male infertility in Japanese men

Deletion of the azoospermia factor c (AZFc), located on the long arm of the Y chromosome, is a cause of male infertility. The structure of the Y chromosome is diversified by the copy number of various genes, such as deleted in azoospermia (DAZ), basic protein Y2, chromodomain Y1, testis-specific transcript Y-linked 4, and Golgi autoantigen golgin subfamily a2 like Y, located in the AZF region. In this study, we investigated the deletion of each gene copy and analyzed its relationship with Japanese male infertility. Deletions of single nucleotide variants of each gene copy in 721 proven fertile men as controls, 139 patients with non-obstructive azoospermia (NOA), and 56 patients with oligozoospermia (OS) were analyzed via polymerase chain reaction-restriction fragment length polymorphism analysis. Their association with infertility was analyzed using logistic regression analysis adjusted for the Y-chromosome haplogroup, D1a2a. Deletions of DAZ/II in the r1 region and DAZ/V in the r1 and r2 regions showed significant associations with NOA (odds ratio [OR] = 4.15, 95 % confidence interval [CI] = 1.18-14.6, P = 0.026; OR = 4.19, 95 % CI = 1.19-14.7, P = 0.025, respectively). They did not show any association with OS. Partial deletion of the AZFc region affects spermatogenesis in Japanese male.

Repetitive DNA Sequences in the Human Y Chromosome and Male Infertility

The male-specific Y chromosome, which is well known for its diverse and complex repetitive sequences, has different sizes, genome structures, contents and evolutionary trajectories from other chromosomes and is of great significance for testis development and function. The large number of repetitive sequences and palindrome structure of the Y chromosome play an important role in maintaining the stability of male sex determining genes, although they can also cause non-allelic homologous recombination within the chromosome. Deletion of certain Y chromosome sequences will lead to spermatogenesis disorders and male infertility. And Y chromosome genes are also involved in the occurrence of reproductive system cancers and can increase the susceptibility of other tumors. In addition, the Y chromosome has very special value in the personal identification and parentage testing of male-related cases in forensic medicine because of its unique paternal genetic characteristics. In view of the extremely high frequency and complexity of gene rearrangements and the limitations of sequencing technology, the analysis of Y chromosome sequences and the study of Y-gene function still have many unsolved problems. This article will introduce the structure and repetitive sequence of the Y chromosome, summarize the correlation between Y chromosome various sequence deletions and male infertility for understanding the repetitive sequence of Y chromosome more systematically, in order to provide research motivation for further explore of the molecules mechanism of Y-deletion and male infertility and theoretical foundations for the transformation of basic research into applications in clinical medicine and forensic medicine.

Y-chromosome genes associated with sertoli cell-only syndrome identified by array comparative genome hybridization

BACKGROUND

The precise contribution of each chromosome gene or gene family in achieving male fertility is still the subject of debate. Most studies have examined male populations with heterogeneous causes of infertility, and have therefore reached controversial or uncertain conclusions. This study uses Y-chromosome array-based comparative genomic hybridization (aCGH) to examine a population of males with a uniform sertoli cell-only syndrome (SCOS) infertility phenotype.

METHODS

Initial analysis of gene copy number variations in 8 SCOS patients, with determination of the log-ratio of probe signal intensity against a DNA reference, was performed using the Y-chromosome NimbleGen aCGH. To confirm the role of candidate genes, real-time quantitative RT-PCR was used to compare 19 patients who had SCOS non-obstructive azoospermia with 15 patients who had obstructive azoospermia but normal spermatogenesis.

RESULTS

Our initial aCGH experiments identified CDY1a and CDY1b double deletions in all 8 patients who had total germ cell depletion. However, 5 patients had DAZ1/2 and DAZ3/4 deletions, 1 patient had a DAZ2 and DAZ3/4 deletion, and 2 patients had no DAZ1/2 or DAZ3/4 deletions. Examination of testicular mRNA expression in another 19 patients with SCOS indicated all patients had no detectable levels of CDY1.

CONCLUSIONS

Our findings indicate that CDY1 deletion in SCOS patients, and analysis of the expression of DAZ and CDY1 genes using aCGH and quantitative RT-PCR, may be useful to predict the presence of mature spermatozoa.

Clinical implications of Y chromosome microdeletions among infertile men

Male factor infertility contributes significantly to couples facing difficulty achieving a pregnancy. Genetic factors, and specifically those related to the Y chromosome, may occur in up to 15% of men with oligozoospermia or azoospermia. A subset of loci within the Y chromosome, known as the azoospermia factors (AZFa, AZFb, and AZFc), have been associated with male infertility. Emerging evidence has demonstrated that microdeletions of at least a subset of these regions may also have impacts on systemic conditions. This review provides a brief review of male infertility and the structure of the Y chromosome, and further highlights the role of Y chromosome microdeletions in male infertility and other systemic disease.

Reproductive outcomes and Y chromosome instability in radiation-exposed male workers in cardiac catheterization laboratory

Occupational radiation exposure may impact the reproductive outcome of male workers in the cardiac catheterization laboratory (cath Lab) who receive a dose of ~1-10 mSv/year. An increased copy number variation (CNV) in azoospermia factor region c (AZFc) of the Y chromosome is a marker of spermatogenic failure, previously associated with radiation exposure. This study sought to investigate the association between paternal exposure in the Cath Lab and adverse reproductive outcomes as well as to assess the induction of CNV in the AZFc region. In a case-control study, we enrolled 193 catheterization lab workers (Group I) and 164 age-matched unexposed controls (Group II). Reproductive outcomes were assessed through a structured questionnaire. Two sequence-tagged sites (SY1197 and SY579) in AZFc region were evaluated by qRT-PCR in 83 exposed and 47 unexposed subjects. Exposed workers had a higher prevalence of low birth weight in offspring (Group I = 13% vs. II = 5.3%, P = 0.02; OR_adjusted = 2.7; 95% CI: 1.1-6.3; P = 0.02). The mean of CNV (microdeletion and microduplication) for SY1197 was significantly higher in the exposed workers (Group I = 1.53 ± 0.85 vs. Group II = 1.02 ± 0.41; P = 0.0005). Despite the study design limitations, our findings show that chronic occupational radiation exposure of male workers is correlated with higher prevalence of low birth weight in offspring and instability in the Y chromosome AZFc region. Environ. Mol. Mutagen. 61:361-368, 2020. © 2019 Wiley Periodicals, Inc.

The Role of Number of Copies, Structure, Behavior and Copy Number Variations (CNV) of the Y Chromosome in Male Infertility

The World Health Organization (WHO) defines infertility as the inability of a sexually active, non-contracepting couple to achieve spontaneous pregnancy within one year. Statistics show that the two sexes are equally at risk. Several causes may be responsible for male infertility; however, in 30–40% of cases a diagnosis of idiopathic male infertility is made in men with normal urogenital anatomy, no history of familial fertility-related diseases and a normal panel of values as for endocrine, genetic and biochemical markers. Idiopathic male infertility may be the result of gene/environment interactions, genetic and epigenetic abnormalities. Numerical and structural anomalies of the Y chromosome represent a minor yet significant proportion and are the topic discussed in this review. We searched the PubMed database and major search engines for reports about Y-linked male infertility. We present cases of Y-linked male infertility in terms of (i) anomalies of the Y chromosome structure/number; (ii) Y chromosome misbehavior in a normal genetic background; (iii) Y chromosome copy number variations (CNVs). We discuss possible explanations of male infertility caused by mutations, lower or higher number of copies of otherwise wild type, Y-linked sequences. Despite Y chromosome structural anomalies are not a major cause of male infertility, in case of negative results and of normal DNA sequencing of the ascertained genes causing infertility and mapping on this chromosome, we recommend an analysis of the karyotype integrity in all cases of idiopathic fertility impairment, with an emphasis on the structure and number of this chromosome.

The Association of Partial Azoospermia Factor C Deletions and Male Infertility in Northwestern China

BACKGROUND

Male infertility is a major health issue worldwide. Y chromosome microdeletions are well-characterized genetic causes of male infertility. The association of partial AZFc deletions (gr/gr, b2/b3, and b1/b3) with male infertility is not well confirmed in diverse populations. The purpose of the present study was to investigate the frequency of partial AZFc deletions and their association with male infertility in a population from Northwestern China.

METHODS

Multiplex polymerase chain reaction was used to detect partial AZFc deletions in 228 infertile patients. We analyzed 141 cases of azoospermia (AS), 87 cases of oligozoospermia (OS), and 200 fertile controls.

RESULTS

Our data showed that the frequency of a b2/b3 deletion in infertile men, men with AS, men with OS, and controls was 3.51, 2.13, 5.75, and 0.00%, respectively. The frequency of this deletion was significantly different between the infertile group and the control group (3.51 vs. 0.00%, respectively, p = 0.021) and between the OS group and the control group (5.75 vs. 0.00%, respectively, p = 0.003). The frequency of a gr/gr deletion in each group was 11.84, 9.22, 16.09, and 7.50%, respectively. The frequency of a gr/gr deletion was significantly different between the OS group and the control group (16.09 vs. 7.50%, respectively, p = 0.026) but not between the infertile group and the control group (11.84 vs. 7.50%, p = 0.132) or the AS group and the control group (9.22 vs. 7.50%, p = 0.569). The frequency of a b1/b3 deletion was 0.44, 0.71, 0.00, and 3.00%, respectively. For this deletion, there was no significant difference between the infertile (0.44 vs. 3.00%, p = 0.089), AS (0.71 vs. 3.00%, p = 0.276), and OS groups (0.00 vs. 3.00%, p = 0.236) and the control group.

CONCLUSIONS

Our results suggest that the b2/b3 deletion might be associated with male infertility and that the gr/gr deletion might be associated with spermatogenic failure in men with OS in Northwestern China (Ningxia).

Genome-wide differential methylation analyses identifies methylation signatures of male infertility

STUDY QUESTION

Do methylation changes in sperm DNA correlate with infertility?

STUDY ANSWER

Loss of spermatogenesis and fertility was correlated with 1680 differentially-methylated CpGs (DMCs) across 1052 genes.

WHAT IS KNOWN ALREADY

Methylation changes in a number of genes have been correlated with reduced sperm count and motility.

STUDY DESIGN, SIZE, DURATION

This case-control study used spermatozoal DNA from 38 oligo-/oligoastheno-zoospermic infertile patients and 26 normozoospermic fertile men.

PARTICIPANTS/MATERIALS, SETTINGS, METHODS

Genome-wide methylation analysis was undertaken using 450 K BeadChip on spermatozoal DNA from six infertile and six fertile men to identify DMCs. This was followed by deep sequencing of spermatozoal DNA from 32 infertile patients and 20 fertile controls.

MAIN RESULTS AND THE ROLE OF CHANCE

A total of 1680 DMCs were identified, out of which 1436 were hypermethylated and 244 were hypomethylated. Classification of DMCs according to the genes identified BCAN, CTNNA3, DLGAP2, GATA3, MAGI2 and TP73 among imprinted genes, SPATA5, SPATA7, SPATA16 and SPATA22 among spermatogenesis-associated genes, KDM4C and JMJD1C, EZH2 and HDAC4 among genes which regulate methylation and gene expression, HLA-C, HLA-DRB6 and HLA-DQA1 among complementation and immune response genes, and CRISPLD1, LPHN3 and CPEB2 among other genes. Genes showing significant differential methylation in deep sequencing, i.e. HOXB1, GATA3, EBF3, BCAN and TCERG1L, are strong candidates for further investigations. The role of chance was ruled out by deep sequencing of select genes.

LARGE-SCALE DATA

N/A.

LIMITATIONS, REASON FOR CAUTION

Genome-wide analyses are fairly accurate, but may not be exactly validated in replication studies across all DMCs. We used the 't' test in the genome-wide methylation analysis, whereas other tests could provide a more robust and powerful analysis.

WIDER IMPLICATIONS OF THE FINDINGS

DMCs can serve as markers for inclusion in infertility screening panels, particularly those in the genes showing differential methylation consistent with previous studies. The genes validated by deep sequencing are strong candidates for investigations of their roles in spermatogenesis.

STUDY FUNDING/COMPETING INTEREST(S)

The study was funded by the Council of Scientific and Industrial Research (CSIR), Govt. of India with grant number BSC0101 awarded to Rajender Singh. None of the authors has any competing interest to declare.

gr/gr deletion predisposes to testicular germ cell tumour independently from altered spermatogenesis: results from the largest European study

The association between impaired spermatogenesis and TGCT has stimulated research on shared genetic factors. Y chromosome-linked partial AZFc deletions predispose to oligozoospermia and were also studied in TGCT patients with controversial results. In the largest study reporting the association between gr/gr deletion and TGCT, sperm parameters were unknown. Hence, it remains to be established whether this genetic defect truly represents a common genetic link between TGCT and impaired sperm production. Our aim was to explore the role of the following Y chromosome-linked factors in the predisposition to TGCT: (i) gr/gr deletion in subjects with known sperm parameters; (ii) other partial AZFc deletions and, for the first time, the role of partial AZFc duplications; (iii) DAZ gene dosage variation. 497 TGCT patients and 2030 controls from two Mediterranean populations with full semen/andrological characterization were analyzed through a series of molecular genetic techniques. Our most interesting finding concerns the gr/gr deletion and DAZ gene dosage variation (i.e., DAZ copy number is different from the reference sequence), both conferring TGCT susceptibility. In particular, the highest risk was observed when normozoospermic TGCT and normozoospermic controls were compared (OR = 3.7; 95% CI = 1.5-9.1; p = 0.006 for gr/gr deletion and OR = 1.8; 95% CI = 1.1-3.0; p = 0.013 for DAZ gene dosage alteration). We report in the largest European study population the predisposing effect of gr/gr deletion to TGCT as an independent risk factor from impaired spermatogenesis. Our finding implies regular tumour screening/follow-up in male family members of TGCT patients with gr/gr deletion and in infertile gr/gr deletion carriers.

Natural Transmission of b2/b3 Subdeletion or Duplication to Expanded Y Chromosome Microdeletions

Background

Y chromosome microdeletions are usually de novo mutations, but in several cases, transmission from fertile fathers to infertile sons has been reported.

Material/Methods

We report 3 cases of infertile patients who inherited expanded Y chromosome microdeletions from their fathers, who carried b2/b3 subdeletion or duplication. The karyotype was analyzed using G-banding. High-throughput sequencing was used to detect AZF region microdeletions.

Results

Cytogenetic analysis showed a normal karyotype 46,XY in patient 1 (P1), patient 2 (P2), and their fathers (F1 and F2). Patient 3 (P3) and his father (F3) presented a karyotype of 46,XY,Yqh-. High-throughput sequencing for the AZF disclosed an identical b2/b3 subdeletion in the F1 and F2. P1 had an AZFc deletion that accounted for 3.5 Mb, and P2 had an AZFa+b+c microdeletion that accounted for 10.5 Mb. F3 had a b2/b3 duplication of 1.8Mb, but P3 had an AZFb+c deletion of 6.2 Mb.

Conclusions

Our findings suggest that b2/b3 partial deletion or duplication can lead to structural instability in the Y chromosome and be a risk factor of complete deletion of AZFc or more expanded deletion during transmission.

Genetics of the human Y chromosome and its association with male infertility

The human Y chromosome harbors genes that are responsible for testis development and also for initiation and maintenance of spermatogenesis in adulthood. The long arm of the Y chromosome (Yq) contains many ampliconic and palindromic sequences making it predisposed to self-recombination during spermatogenesis and hence susceptible to intra-chromosomal deletions. Such deletions lead to copy number variation in genes of the Y chromosome resulting in male infertility. Three common Yq deletions that recur in infertile males are termed as AZF (Azoospermia Factor) microdeletions viz. AZFa, AZFb and AZFc. As estimated from data of nearly 40,000 Y chromosomes, the global prevalence of Yq microdeletions is 7.5% in infertile males; however the European infertile men are less susceptible to Yq microdeletions, the highest prevalence is in Americans and East Asian infertile men. In addition, partial deletions of the AZFc locus have been associated with infertility but the effect seems to be ethnicity dependent. Analysis of > 17,000 Y chromosomes from fertile and infertile men has revealed an association of gr/gr deletion with male infertility in Caucasians and Mongolian men, while the b2/b3 deletion is associated with male infertility in African and Dravidian men. Clinically, the screening for Yq microdeletions would aid the clinician in determining the cause of male infertility and decide a rational management strategy for the patient. As these deletions are transmitted to 100% of male offspring born through assisted reproduction, testing of Yq deletions will allow the couples to make an informed choice regarding the perpetuation of male infertility in future generations. With the emerging data on association of Yq deletions with testicular cancers and neuropsychiatric conditions long term follow-up data is urgently needed for infertile men harboring Yq deletions. If found so, the information will change the current the perspective of androgenetics from infertility and might have broad implication in men health.

Spermatogenic failure and the Y chromosome

The Y chromosome harbors a number of genes essential for testis development and function. Its highly repetitive structure predisposes this chromosome to deletion/duplication events and is responsible for Y-linked copy-number variations (CNVs) with clinical relevance. The AZF deletions remove genes with predicted spermatogenic function en block and are the most frequent known molecular causes of impaired spermatogenesis (5-10% of azoospermic and 2-5% of severe oligozoospermic men). Testing for this deletion has both diagnostic and prognostic value for testicular sperm retrieval in azoospermic men. The most dynamic region on the Yq is the AZFc region, presenting numerous NAHR hotspots leading to partial losses or gains of the AZFc genes. The gr/gr deletion (a partial AZFc deletion) negatively affects spermatogenic efficiency and it is a validated, population-dependent risk factor for oligozoospermia. In certain populations, the Y background may play a role in the phenotypic expression of partial AZFc rearrangements and similarly it may affect the predisposition to specific deletions/duplication events. Also, the Yp contains a gene array, TSPY1, with potential effect on germ cell proliferation. Despite intensive investigations during the last 20 years on the role of this sex chromosome in spermatogenesis, a number of clinical and basic questions remain to be answered. This review is aimed at providing an overview of the role of Y chromosome-linked genes, CNVs, and Y background in spermatogenesis.

Azoospermia Factor C Subregion of the Y Chromosome

The azoospermia factor (AZF) region on the Y chromosome consists of genes required for spermatogenesis. Among the three subregions, the AZFc subregion located at the distal portion of AZF is the driver for genetic variation in Y chromosome. The candidate gene of AZFc is known as deleted in azoospermia gene, which is studied with interest because it is involved in germ cell development and most frequently deleted genes leading to oligozoospermia and azoospermia. Recently, two partial deletions in AZFc gr/gr and b2/b3 are characterized at the molecular level which showed homologous recombination between amplicons, affecting spermatogenesis process. There are novel methods and commercially available kits for accurate screening and characterization of microdeletions. It is important to detect the AZFc microdeletions through genetic screening and counseling those infertile men who planned to avail assisted reproduction techniques such as undergoing intracytoplasmic sperm injection or in vitro fertilization.

gr/gr-DAZ2-DAZ4-CDY1b deletion is a high-risk factor for male infertility in Tunisian population

The azoospermia factor c (AZFc) region harbors multi-copy genes that are expressed in the testis. Deletions of this region lead to reduced copy numbers of these genes. In this present study we aimed to determine the frequency of AZFc subdeletion in infertile and fertile men from Tunisia and to identify whether deletions of DAZ and CDY1 gene copies are deleterious on spermatogenesis and on semen quality. We studied a group of 241 infertile men and 115 fertile healthy males using a sequence tagged site (STS)±method. To gain insight into the molecular basis of the heterogeneous phenotype observed in men with the deletion we defined the type of DAZ and CDY1 genes deleted. We reported in the present study and for the first time a new type of AZFc deletion (gr/gr-DAZ2-DAZ4-CDY1b) and hypothesis that this new deletion is the result of two successive events. We also demonstrated that this deletion constitutes a relative high-risk factor for male infertility in Tunisian population.

Deletion of GOLGA2P3Y but not GOLGA2P2Y is a risk factor for oligozoospermia

The AZFc locus on the human Y chromosome harbours several multicopy genes, some of which are required for spermatogenesis. It is believed that deletion of one or more copies of these genes is a cause of infertility in some men. GOLGA2LY is one of the genes in the AZFc locus and it exists in two copies, GOLGA2P2Y and GOLGA2P3Y. The involvement of GOLGA2LY gene copy deletions in male infertility, however, is unknown. This study aimed to investigate the association of deletions of GOLGA2P2Y and GOLGA2P3Y gene copies with male infertility and with sperm concentration and motility. The frequency of GOLGA2P3Y deletion was significantly higher in oligozoospermic men compared with normozoospermic men (7.7% versus 1.2%; P = 0.0001), whereas the frequency of GOLGA2P2Y deletion was comparable between oligozoospermic and normozoospermic men (10.3% versus 11.3%). The deletion of GOLGA2P3Y but not GOLGA2P2Y was significantly higher (P = 0.03) in men with gr/gr rearrangements, indicating that GOLGA2P3Y deletions increase the susceptibility of men with gr/gr rearrangements to oligozoospermia. Furthermore, men with GOLGA2P3Y deletion had reduced sperm concentration and motility compared with men without deletion or with deletion of GOLGA2P2Y. These findings indicate GOLGA2P3Y gene copy may be candidate AZFc gene for male infertility.

The Biology and Evolution of Mammalian Y Chromosomes

Mammals have the oldest sex chromosome system known: the mammalian X and Y chromosomes evolved from ordinary autosomes beginning at least 180 million years ago. Despite their shared ancestry, mammalian Y chromosomes display enormous variation among species in size, gene content, and structural complexity. Several unique features of the Y chromosome--its lack of a homologous partner for crossing over, its functional specialization for spermatogenesis, and its high degree of sequence amplification--contribute to this extreme variation. However, amid this evolutionary turmoil many commonalities have been revealed that have contributed to our understanding of the selective pressures driving the evolution and biology of the Y chromosome. Two biological themes have defined Y-chromosome research over the past six decades: testis determination and spermatogenesis. A third biological theme begins to emerge from recent insights into the Y chromosome's roles beyond the reproductive tract--a theme that promises to broaden the reach of Y-chromosome research by shedding light on fundamental sex differences in human health and disease.

Susceptibility of gr/gr rearrangements to azoospermia or oligozoospermia is dependent on DAZ and CDY1 gene copy deletions

PURPOSE

The purpose of this study was to determine the association of AZFc subdeletions (gr/gr, b1/b3 and b2/b3) and deletion of DAZ and CDY1 gene copies with male infertility

METHODS

Three hundred twelve controls, 172 azoospermic and 343 oligozoospermic subjects were subjected to AZFc subdeletion typing by STS PCR. Deletion of DAZ and CDY1 gene copies was done using sequence family variant analysis. Sperm concentration and motility were compared between men with and without AZFc subdeletions. Effect of the AZFc subdeletions on ICSI outcome was evaluated.

RESULTS

Amongst the three AZFc subdeletions, the frequency of gr/gr was higher in oligozoospermic (10.5 %) and azoospermic (11.6 %) men as compared to controls (5.1 %). In men with AZFc subdeltions, loss of two DAZ and one CDY1 gene copy made them highly susceptible to azoospermia and severe oligozoospermia with OR of 29.7 and 26, respectively. These subdeletions had no effect on ICSI outcome, albeit there were an increased number of poor quality embryos in AZFc subdeleted group.

CONCLUSION

AZFc subdeletions are a major risk factor for male infertility in the Indian population. In the subjects with AZFc subdeletions, the deletion of DAZ and CDY1 gene copies increases its susceptibility to azoospermia or severe oligozoospermia. Since these deletions can be vertically transmitted to the future male offspring by ICSI, it will be essential to counsel the couples for the transmission of the genetic defect in the male offspring born after assisted reproduction and the risk of perpetuating infertility in future generation.

Common AZFc structure may possess the optimal spermatogenesis efficiency relative to the rearranged structures mediated by non-allele homologous recombination

The azoopsermia factor c (AZFc) region of human Y-chromosome is an essential genomic segment for spermatogenesis with frequent non-allele homologous recombination (NAHR). Recent case-control studies on the association of the NAHR-based AZFc structural mutations with spermatogenic failure produced inconsistent results. To more precisely evaluate their spermatogenesis effects, we investigated the correlation between the subdivided AZFc mutations and sperm production in 3,439 Han Chinese males. Our results showed that both partial AZFc deletion-only and primary duplication mutation presented a significant risk for decreased sperm production. Restoration of the reduced dosage of the AZFc content to the normal level had a milder effect, whereas an overdose of the AZFc content arising from multiple duplications of a partial AZFc-deleted structure produced a more serious consequence compared to the partial deletion-only mutation. Additionally, the AZFc-mutated structures with excessive NAHR-substrate showed a notably negative effect on spermatogenesis. These results suggest that the recurrent NAHR-based AZFc mutations may be associated with decreased spermatogenesis efficiency in present population. More significantly, our finding implies that the overdose of AZFc NAHR-substrate may produce an additional risk for the massive AZFbc deletions during the multi-stage division process of germ cells and thus impair the global spermatogenesis efficiency in the carriers.