Types of Y chromosome deletions and their frequency in infertile men

Deletions of Y chromosome AZF locus were analyzed during a large-scale andrological and genetic examination of 810 infertile men. The search for Yq microdeletions was carried out according to the standard EAA/EMQN guidelines. The breakpoints were mapped for the deletions in AZF locus. The Y chromosome macro- and microdeletions were detected in 61 (7.5%) infertile men. The frequencies of AZF deletions during azoospermia and severe oligozoospermia amounted to 12.2 and 8.1 %, respectively. On the whole, the frequencies of Yq microdeletions and the genophenotypic correlations characteristic of various AZF deletion types comply with the relevant published data. However, spermatozoids in the ejaculate sediment of men with completely deleted AZFa region or AZFb+c deletions (from solitary spermatozoids to several dozens) were detected for the first time. It was demonstrated that the breakpoints were localized between AZFa and AZFb regions proximally to AZFb+c microdeletions for the majority of cytogenetically detectable deletions in the Y chromosome long arm. This indicates that the mechanisms underlying Yq macro- and microdeletions are somewhat different. The issues related to the role of Y chromosome deletions in the origins of monosomy for X chromosome and X/XY mosaicism are discussed.     

Genetische Aspekte bei Spermatogenesestörungen

The cause for infertility which affects about 10–15% of all couples may be found in approximately half of the cases in the male partners who usually exhibit reduced sperm counts in the ejaculate (i.e. oligozoospermia or azoospermia). The clinically most relevant genetic causes of spermatogenic failure are chromosomal aberrations including Klinefelter’s syndrome and Y chromosomal microdeletions of the AZF loci. Aside from the full clinical picture of cystic fibrosis, mutations in the CFTR gene can cause an isolated obstructive azoospermia without spermatogenic impairment. Genetic investigations should depend on the results of andrological examinations. Chromosomal aberrations are detected more frequently with decreasing sperm counts, where autosomes (e.g. translocations) are predominantly involved in men with oligozoospermia whereas in 10–15% azoospermia is caused by Klinefelter’s syndrome. Classical AZF deletions are found only in men with severe oligospermia or azoospermia and have a prognostic value. In contrast to men with AZFc deletions, carriers of complete AZFa and AZFb deletions have virtually no chance for testicular sperm extraction and a testicular biopsy is not advised. Rare cases of male infertility may be caused by specific syndromes or sperm defects (e.g. globozoospermia and disorders of ciliary structure).     

Molecular analysis of Y chromosome microdeletions in idiopathic cases of male infertility in Serbia

The aim of this study was to detect frequency of microdeletions of Y chromosome in idiopathic cases of male infertility in Serbian population. Patients were subjected to detailed clinical, endocrinological and cytogenetic examinations. Ninety patients with normal cytogenetic findings with azoospermia and severe oligozoospermia were included in the study. In these patients microdeletion analysis was performed by multiplex polymerase chain reaction (PCR) method on DNA extracted from peripheral blood. In each case 6 markers in azoospermia factor (AZF) regions were tested: sY84, sY86 (AZFa); sY127, sY134 (AZFb); sY254, sY255 (AZFc). Deletions on Y chromosome were detected in 14 of 90 cases (15.6%), 9 with azoospermia and 5 with severe oligozoospermia. Of total number of 17 deletions, 11 (64.7%) were detected in AZFc region, 3 (17.6%) in AZFa region and 3 (17.6%) in AZFb region. Microdeletions in AZF region of Y chromosome, especially AZFc microdeletions, represent common genetic cause of idiopathic azoospermia and severe oligozoospremia in Serbian infertile men. Therefore, testing for Y chromosome microdeletions should be considered as an important element in diagnosis and genetic counseling of infertile men in Serbia and decisions regarding the assisted reproduction should be made based on the presence and type of AZF microdeletions.     

Y chromosome microdeletions in Brazilian fertility clinic patients

Microdeletions in Yq are associated with defects in spermatogenesis, while those in the AZF region are considered critical for germ cell development. We examined microdeletions in the Y chromosomes of patients attended at the Laboratory of Human Reproduction of the Clinical Hospital of the Federal University of Goiás as part of a screening of patients who plan to undergo assisted reproduction. Analysis was made of the AZF region of the Y chromosome in men who had altered spermograms to detect possible microdeletions in Yq. Twenty-three patients with azoospermia and 40 with severe oligozoospermia were analyzed by PCR for the detection of six sequence-tagged sites: sY84 and sY86 for AZFa, sY127 and sY134 for AZFb, and sY254 and sY255 for AZFc. Microdeletions were detected in 28 patients, including 10 azoospermics and 18 severe oligozoospermics. The patients with azoospermia had 43.4% of their microdeletions in the AZFa region, 8.6% in the AZFb region and 17.4% in the AZFc region. In the severe oligozoospermics, 40% were in the AZFa region, 5% in the AZFb region and 5% in the AZFc region. We conclude that microdeletions can be the cause of idiopathic male infertility, supporting conclusions from previous studies.     

Molecular analysis of Y chromosome microdeletions in idiopathic cases of male infertility in Serbia

The aim of this study was to detect frequency of microdeletions of Y chromosome in idiopathic cases of male infertility in Serbian population. Patients were subjected to detailed clinical, endocrinological and cytogenetic examinations. Ninety patients with normal cytogenetic findings with azoospermia and severe oligozoospermia were included in the study. In these patients microdeletion analysis was performed by multiplex polymerase chain reaction (PCR) method on DNA extracted from peripheral blood. In each case 6 markers in azoospermia factor (AZF) regions were tested: sY84, sY86 (AZFa); sY127, sY134 (AZFb); sY254, sY255 (AZFc). Deletions on the Y chromosome were detected in 14 of 90 cases (15.6%), nine with azoospermia and five with severe oligozoospermia. Of total number of 17 deletions, 11 (64.7%) were detected in AZFc region, three (17.6%) in AZFa region and three (17.6%) in AZFb region. Microdeletions in AZF region of the Y chromosome, especially AZFc microdeletions, represent common genetic cause of idiopathic azoospermia and severe oligozoospremia in Serbian infertile men. Therefore, testing for Y chromosome microdeletions should be considered as an important element in diagnosis and genetic counseling of infertile men in Serbia and decisions regarding the assisted reproduction should be made based on the presence and type of AZF microdeletions. The text was submitted by the authors in English.     

AZF microdeletions on the Y chromosome of infertile men from Turkey

Intervals V and VI of Yq11.23 regions contain responsible genes for spermatogenesis, and are named as "azoospermia factor locus" (AZF). 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 on the Y chromosome in infertile Turkish males with azoospermia or oligozoospermia. We applied multiplex polymerase chain reaction (PCR) using several sequence-tagged site (STS) primer sets, in order to determine Y chromosome microdeletions. In this study, 61 infertile males were enrolled for the molecular AZF screening program. In this cohort, one infertile male had 46,XX karyotype and the remaining had 46,XY karyotypes. Forty-eight patients had a diagnosis of azoospermia and 13 had oligozoospermia. Microdeletions in AZFa, AZFb and AZFc (DAZ gene) regions were detected in two of the 60 (3.3%) idiopathic infertile males with normal karyotypes and a SRY translocation was determined on 46,XX male. Our findings suggest that genetic screening should be advised to infertile men before starting assisted reproductive treatments.     

Cytogenetic and molecular analysis of male infertility

Reduced male fertility and subfertility can be caused by genetic factors that affect both germ cell development, differentiation, and function; in particular, chromosome abnormalities and Yq microdeletions are a possible cause of spermatogenetic impairment in males as shown by their higher frequency in infertile men than in the general male population. Microdeletion of the long arm of the Y chromosome (Yq) are associated with spermatogenic failure and have been used to define three regions on Yq (AZFa, AZFb, and AZFc) that are critical for germ cell development. With the advent of assisted reproductive technology and intracytoplasmic sperm injection, knowledge about the various factors leading to spermatogenic impairment is one of the most important aspects of scientific research. Therefore, this study was designed to identify the frequency of cytogenetic and submicroscopic interstitial deletions in azoospermia factor loci in infertile Indian males. One hundred and eighty males with nonobstructive oligozoospermia and azoospermia were included in this study. Semen analysis was done in each case to determine the spermatogenic status. Individuals were subjected to detailed clinical examination, family history, and endocrinological and cytogenetic study after consent from the patient. Peripheral blood cultures were set up according to standard protocols and 30 G-banded metaphases were analyzed in each case. Numerical and structural chromosomal abnormalities were detected in 40 infertile cases. Fluorescence in situ hybridization analysis was done in some cases to identify the percentage of mosaic cell lines and any cryptic or low-level mosaicism. Polymerase chain reaction microdeletion analysis was done in 140 cytogenetically normal cases. Of the 140 cases, 8 showed deletion of at least one of the sequence-tagged site markers. Review of literature has shown that the overall frequency of microdeletions varies from 1 to 55%. In the present study, the frequency of microdeletion was 5.8%, and deletions were identified in cases with undescended testis and varicocele and cases with bilateral severe testiculopathy.     

Y-chromosome haplotypes in azoospermic Israeli men

Among azoospermic and severely oligozoospermic men, 7-15% present microdeletions of a region on the long arm of the Y chromosome that has been called AZF (azoospermia factor). Because these deletions present varying relative frequencies in different populations, we decided to ascertain whether their presence was correlated with specific Y-chromosome haplotypes. For that, we evaluated 51 infertile Israeli men, 9 of whom had microdeletions in AZF. Haplotypes were identified using a hierarchical system with eight biallelic DNA markers. We also checked for the presence of the deletion marker 50f2/C, which was absent in all seven patients with isolated AZFc deletion and also in the one patient with isolated AZFb deletion, suggesting that these microdeletions overlap. As expected, haplogroup J was the most common (47%), followed by equal frequencies of haplogroups Y* (xDE, J, K), P* (xR1a, R1b8), K* (xP), and E. In six patients with AZFc deficiencies of comparable size, three belonged to haplogroup J, two belonged to haplogroup P* (xR1a, R1b8), and one belonged to haplogroup R1a. Also, there were no significant differences in the haplotype frequencies between the groups with and without microdeletions. Thus we did not identify any association of a specific haplogroup with predisposition to de novo deletion of the AZF region in the Israeli population.     

A cost-effective screening test for detecting AZF microdeletions on the human Y chromosome

PCR-based screening of microdeletions in the azoospermic factor (AZF) on the Yq chromosome is an accepted means of identifying a common genetic cause of male infertility, responsible for 5-15% of cases associated with a low sperm count (相似文献   

A deletion map of the human Yq11 region: implications for the evolution of the Y chromosome and tentative mapping of a locus involved in spermatogenesis.

A deletion map of Yq11 has been constructed by analyzing 23 individuals bearing structural abnormalities (isochromosomes, terminal deletions and X;Y, Y;X, or A;Y translocations) in the long arm of the Y chromosome. Twenty-two Yq-specific loci were detected using 14 DNA probes, ordered in 11 deletion intervals, and correlated with the cytogenetic map of the chromosome. The breakpoints of seven translocations involving Xp22 and Yq11 were mapped. The results obtained from at least five translocations suggest that these abnormal chromosomes may result from aberrant interchanges between X-Y homologous regions. The use of probes detecting Yq11 and Xp22.3 homologous sequences allowed us to compare the order of loci within these two chromosomal regions. The data suggest that at least three physically and temporary distinct rearrangements (pericentric inversion of pseudoautosomal sequences and/or X-Y transpositions and duplications) have occurred during evolution and account for the present organization of this region of the human Y chromosome. The correlation between the patient' phenotypes and the extent of their Yq11 deletions permits the tentative assignment of a locus involved in human spermatogenesis to a specific interval within Yq11.23.     

Chromosomal aberrations, Yq microdeletion, and sperm DNA fragmentation in infertile men opting for assisted reproduction

Male infertility is a multi‐factorial disorder, and identification of its etiology in an individual is critical for treatment. Systematically elucidating the underlying genetic causes (chromosomal and Yq microdeletion) and factors, such as reactive oxygen species (ROS) levels and total antioxidant capacity (TAC), which contribute to sperm DNA damage, may help to reduce the number of men with idiopathic infertility and provide them with the most suitable therapeutics and counseling. This study was done to comprehensively investigate genetic and oxidative stress factors that might be the etiology of a large percentage of men with idiopathic infertility. One hundred twelve infertile men and 76 fertile controls were screened for chromosomal aberrations and Yq microdeletions. ROS, TAC, and sperm DNA damage were assessed in cytogenetically normal, non‐azoospermic men with intact Y chromosome (n = 93). ROS was assessed in neat and washed semen by chemiluminescence; seminal TAC with a commercially available kit; and sperm DNA damage by the comet assay. Two men had cytogenetic abnormalities and seven men harbored Yq microdeletions. ROS levels in neat and washed semen of infertile men were significantly higher (P < 0.01) than controls. Infertile men had significantly lower (P < 0.01) TAC levels (1.79 mM), whereas sperm DNA fragmentation in infertile men was significantly higher (P < 0.01) than controls. Genetic factors and oxidative stress cumulatively account for large number of idiopathic infertile cases. Unlike, genetic causes, which cannot be cured, timely identification and management of oxidative stress may help to reverse/reduce the effects on induced DNA damage, and improve the outcomes for infertile males. Mol. Reprod. Dev. 79: 637–650, 2012. © 2012 Wiley Periodicals, Inc.     

QF-PCR筛查男性不育患者Y染色体无精子症因子微缺失

为评估定量荧光PCR(Quantitative fluorescent polymerase chain reaction, QF-PCR)技术在快速筛查无精子症因子(Azoospermia factor, AZF)微缺失中的应用, 文章对1218例非梗阻性无精子症、少精子症的男性不育患者, 采用多重QF-PCR结合毛细管电泳技术, 检测Y染色体长臂AZF区9个序列标签位点(Sequence tagged site, STS)以及性染色体短臂的AMEL(Amelogenin)和SRY(Sex-determining region of Y chromosome)位点, 辅以常规染色体G显带方法进行核型分析。结果显示, 1218例患者中105例可见AZF区微缺失(8.62%), 其中AZFc区缺失(67.62%)最常见, 其次为AZFb,c区缺失(20.95%); AZFb区缺失(7.62%)和AZFa区缺失(3.81%)则较少见; 另有5例患者为AZFa,b,c区缺失合并AMEL-Y缺失, 提示可能缺少Y染色体, 经核型分析验证为46,XX(性反转)。105例AZF区微缺失患者的染色体核型分析显示染色体异常16例, 其中“Yqh-”12例。根据AMEL-X/AMEL-Y比值, 可见1218例患者中86例可能存在性染色体异常, 经核型分析验证, 68例为性染色体非整倍体。多重QF-PCR技术, 一个反应即能检测样本的多个位点, 并可提示性染色体是否存在异常, 有助于男性不育患者尽早明确病因, 也为后续的检查和治疗提供依据。     

Association of spermatogenic failure with the b2/b3 partial AZFc deletion

Infertility affects around 1 in 10 men and in most cases the cause is unknown. The Y chromosome plays an important role in spermatogenesis and specific deletions of this chromosome, the AZF deletions, are associated with spermatogenic failure. Recently partial AZF deletions have been described but their association with spermatogenic failure is unclear. Here we screened a total of 339 men with idiopathic spermatogenic failure, and 256 normozoospermic ancestry-matched men for chromosome microdeletions including AZFa, AZFb, AZFc, and the AZFc partial deletions (gr/gr, b1/b3 and b2/b3).AZFa and AZFc deletions were identified in men with severe spermatogenic failure at similar frequencies to those reported elsewhere. Gr/gr deletions were identified in case and control populations at 5.83% and 6.25% respectively suggesting that these deletions are not associated with spermatogenic failure. However, b2/b3 deletions were detected only in men with spermatogenic failure and not in the normospermic individuals. Combined with our previous data this shows an association of the b2/b3 deletion (p = 0.0318) with spermatogenic failure in some populations. We recommend screening for this deletion in men with unexplained spermatogenic failure.     

The relationship between Y chromosome DNA haplotypes and Y chromosome deletions leading to male infertility

Microdeletions on the short arm of the Y chromosome have defined three non-overlapping regions (AZFa, b, c) recurrently deleted among infertile males. These regions contain several genes or gene families involved in male germ-cell development and maintenance. Even though a meiotic origin for these microdeletions is assumed, the mechanisms and causes leading to microdeletion formation are largely unknown. In order to assess whether some Y chromosome groups (or haplogroups) are predisposed to, or protected against, deletion formation during male meiosis, we have defined and compared Y chromosome haplogroup distribution in a group of infertile/subfertile males harbouring Yq deletions and in a relevant Northwestern European control population. Our analyses suggest that Y chromosome deletion formation is, at least in the study populations, a stochastic event independent of the Y chromosome background on which they arise and may be caused by other genetic and/or environmental factors.     

Microdeletions in interval 6 of the Y chromosome of males with idiopathic sterility point to disruption of AZF,a human spermatogenesis gene

Summary For males with idiopathic sterility, a molecular screen specific for small lesions (microdeletions) in interval 6 of the Y chromosome was set up using 29 Y-DNA probes. A de novo microdeletion in Y interval 6 was detected in 2 out of 19 chromosomally normal sterile males. The first microdeletion includes the Y-DNA probes pY6HP35 and 12f3; the second microdeletion includes the Y-DNA probes pY6HP52, 49f, FR15-II and the subinterval C of probe 50f2. A probe of the pY6H sequence family is present in both deletions. Sequences of this family cross-hybridize to dhMiF1, a DNA sequence of a fertility gene structure on the Y chromosome of Drosophila hydei. It was possible to map the position of the Y-deletion of one patient to the distal part of Yq11.22 or the proximal part of Yq11.23, and the deletion of the second patient to the distal part of Yq11.23. These microdeletions probably do not overlap. Since AZF, a human spermatogenesis gene, has been mapped to Y interval 6, we postulate that the microdeletions detected in this chromosome region affect the functional DNA structure of the AZF gene. If this holds true, it is possible that the AZF locus, cytogenetically mapped to distal Yq11, contains two spermatogenesis genes (AZFa and AZFb) or a large gene structure comparable to the Y fertility genes of Drosophila.     

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.     

Evolutionary breakpoint analysis on Y chromosomes of higher primates provides insight into human Y evolution

Comparative FISH mapping of PAC clones covering almost 3 Mb of the human AZFa region in Yq11.21 to metaphases of human and great apes unravels breakpoints that were involved in species-specific Y chromosome evolution. An astonishing clustering of evolutionary breakpoints was detected in the very proximal region on the long arm of the human Y chromosome in Yq11.21. These breakpoints were involved in deletions, one specific for the human and another for the orang-utan Y chromosome, in a duplicative translocation/transposition specific for bonobo and chimpanzee Y chromosomes and in a pericentric inversion specific for the gorilla Y chromosome. In addition, our comparative results allow the deduction of a model for the human Y chromosome evolution.     

Deletion of CDY1b copy of Y chromosome CDY1 gene is a risk factor of male infertility in Tunisian men

The relationship between male infertility and microdeletions in the Y chromosome that remove multiple genes varies among countries and populations. The aim of this study was to investigate the different types of Chromodomain protein, Y-linked 1 (CDY1) gene deletions and their effect on male infertility and spermatogenesis in Tunisian men. A total of 241 infertile men with different spermatogenic impairments and 115 fertile men were included in this study. We determined the prevalence of CDY1a and CDY1b copy deletions by PCR-RFLP using PvuII as restriction endonuclease. Results: Among the 356 Tunisian individuals, 93.25% had the two copies (CDY1a and CDY1b) of CDY gene (91.2% in infertile patients and 97.3% in fertile men). We also found that deletion of CDY1b was significantly more frequent in infertile patients (azoo/oligospermic and normospermic) than in fertile men (7% vs 1.7% respectively; p value = 0.02). However, deletion of CDY1a copy was very rare, and was detected in only one fertile man and four normospermic infertile patients. Our findings showed that deletion of CDY1b copy gene is a significant risk factor for male infertility independent of sperm concentration, whereas deletion of CDY1a gene seems to have no effect on fertility in the Tunisian population.     

Correlation of Y-chromosome multiple segmental deletions and chromosomal anomalies in non-obstructive azoospermic males from northeastern China

We investigated the frequency and types of Y-chromosome microdeletions and chromosomal anomalies in non-obstructive azoospermic and severely oligozoospermic infertile males in northeastern China. The sample consisted of 519 infertile males (456 azoospermic, 63 severely oligozoospermic). PCR assays for Y-chromosome microdeletions and chromosome analysis were performed on all patients and controls. Array-comparative genomic hybridization was performed for three patients with chromosomal anomalies. Fifty-nine of 519 patients (11.37%) had Y-chromosome microdeletions. Microdeletions were found in 11.18% (51/456) of the non-obstructive azoospermic patients and in 12.7% (8/63) of the severely oligozoospermic patients. Eleven of 51 non-obstructive azoospermic patients with Y-chromosome microdeletions had multiple segmental deletions in the AZFb+c regions; four of these patients had chromosomal anomalies. Our sample from northeastern China had a higher frequency of microdeletions among severely oligozoospermic than among non-obstructive azoospermic males.