Detection of sperm in men with Y chromosome microdeletions of the AZFa,AZFb and AZFc regions

BACKGROUND: Y chromosome microdeletions are associated with severe male factor infertility. In this study, the success rate of testicular sperm retrieval was determined for men with deletions of AZF regions a, b or c. METHODS: AZF deletions were detected by PCR of 30 sequence-tagged sites within Yq emphasizing the AZFa, b and c regions. Semen analysis and diagnostic testis biopsy or testicular sperm extraction (TESE) findings were correlated with the specific AZF region deleted. RESULTS: A total of 78 men with AZF deletions included three with AZFa deletion, 11 with AZFb, 42 with AZFc, 16 with AZFb+c and six with Yq (AZFa+b+c). All men with AZFa, AZFb, AZFb+c and Yq deletions were azoospermic and no sperm were found with TESE or biopsy. Of men with isolated AZFc deletion, sperm were found in 75% (9/12) by TESE and 45% (9/20) on biopsy (56% overall); 62% (26/42) were azoospermic and 38% (16/42) severely oligozoospermic. A total of 7 patients with deletion patterns that included the complete AZFa region and 23 that included the complete AZFb region who underwent TESE or biopsy did not have sperm detected by these surgical measures. CONCLUSIONS: Microdeletion of the entire AZFa or AZFb regions of the Y chromosome portends an exceptionally poor prognosis for sperm retrieval, whereas the majority of men with AZFc deletion have sperm within the semen or testes available for use in IVF/ICSI.     

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染色体小于22号染色体患者AZF微缺失分析

目的观察Y染色体≤22号染色体患者Y染色体微缺失的发生情况。方法本实验对象为47例Y染色体≤22号染色体患者,其中A组精子密度10×106/ml共12例,B组精子密度≥10×106/ml共35例,采用多重聚合酶链反应技术对其进行Y染色体微缺失15个序列标签位点进行检测。结果47例患者中共有4例发现微缺失,缺失率为8.51%;4例均为A组中发现,A组AZF总缺失率为33.33%,AZFa区缺失率为0%,AZFb区缺失率为25%,AZFc区及d区的缺失率均为33.33%,其中3例在无精子症中,缺失率为60%,1例在严重少精子症中,缺失率为14.29%;B组未发现微缺失,缺失率为0%。结论对于Y染色体≤22号染色体的男性,精子密度≥10×106/ml者AZF微缺失发生率很低;而无精子或严重少精子者,则有发生AZF微缺失的风险,尤其无精子症患者发生AZF多区域的联合缺失的风险显著增加。     

Dicentric Y chromosome in an azoospermic male

We describe a 28 year old male with a pseudodicentric Y chromosome who suffered from azoospermia attributed to maturation arrest of the primary spermatocyte, as diagnosed by testicular biopsy. Chromosome analysis, using G, Q and C banding techniques, revealed an abnormal karyotype of 45,X[7]/46,X,psu dic (Y)(pter-->q11.2::q11.2-->pter)[33]. Polymerase chain reaction (PCR) DNA analysis did not detect the absence of DAZ and RBM1 which are candidates for azoospermic factor (AZF) genes. Therefore, it is suggested that the maturation arrest of the primary spermatocyte in this patient was caused either by a pairing dysfunction between the X and Y chromosomes during meiosis or by deletions in the autosomal or the Y chromosomal spermatogenesis controlling genes, excluding DAZ and RBM1.      

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.     

无精和严重少精子症患者Y染色体的微缺失

目的 检测我国无精和严重少精子症患者Y染色体微缺失的发生情况和位点,及其与睾丸病理学类型的关系.方法 取584例无精子症和80例严重少精子症患者精液中细胞或外周血白细胞,裂解提取DNA,用4组多重聚合酶链反应检测分布于AZFa、AZFb、AZFc区,包括欧洲男科学会和欧洲分子遗传学质量控制体系推荐的6个位点在内的共15个序列标签位点(sequence tagged site,SIS)的缺失.对部分有Y染色体微缺失患者进行睾丸细针抽吸活检,检查睾丸病理学类型.结果 584例无精子症患者中,共有66例(11.3%)发生Y染色体微缺失,各区发生率构成比由高到低依次为:AZFc区48例(72.7%),AZFb+c区9例(13.6%),AZFa+b+c区4例(6.1%),AZFb区3例(4.5%),A2Fa区2例(3.0%).80例严重少精子症患者共有10例发生Y染色体微缺失(12.5%),均为AZFc区缺失.AZFc区缺失患者(19例)睾丸病理学类型多样化;AZFb+c区或AZFa+b+c区缺失患者(7例)睾丸病理学类型为唯支持细胞综合征或生精阻滞于精原细胞.结论 Y染色体微缺失在我国的发生情况与其他国家大多数报道基本一致,跨区大缺失对精子发生造成严重影响.     

Does intracytoplasmic sperm injection lead to a rise in the frequency of microdeletions in the AZFc region of the Y chromosome in future generations?

Microdeletions in the AZFc region of the Y chromosome are foundin oligo- and azoospermic men. These mutations were geneticallylethal before the intracytoplasmic sperm injection (ICSI) erabut they can nowadays be transmitted to next generations viaICSI. We have tried to answer the question, ‘Does ICSIlead to a significant rise in the frequency of these microdeletionsin future generations?’, by developing a mathematicalmodel for Y-linked mutations with two variables (fitness andmutation frequency). To illustrate this model we have made estimatesaccording to three imaginary scenarios. Using the assumptionsdescribed, the model predicted that the frequency of microdeletionsin the AZFc region would increase in each generation until aplateau was reached. The higher the fitness, the higher theplateau and the later the plateau would be reached. Taking realisticestimates for fitness (0.5) and spontaneous mutation frequency(0.0001), the maximum increase in men with microdeletions wouldbe twofold. This maximum would be already reached after fivegenerations. However, if the fitness of these men were improvedand approached 1.0, the mechanism of selection would disappearand finally all men would have the deletion in the AZFc region.Because of the assumptions in these scenarios, these estimateshave limitations. The model presented shows that the rise inthe frequency of men with microdeletions in the AZFc regionin future generations would be limited as long as the fitnessof these men remained limited.     

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.     

Y chromosome microdeletions and germinal mosaicism in infertile males

Molecular deletions of the Y chromosome long arm are a frequent cause of male infertility. Because these deletions are thought to be inherited from fathers without Y chromosome deletions, the question arises as to whether their relatively high incidence in the male population could be due to the existence of a mosaicism in somatic and/or germinal paternal cells. This study included a total of 181 infertile men, among whom 18 were found to have an abnormal karyotype. In the other 163, polymerase chain reaction (PCR) analysis detected nine (5.5%) Y chromosome microdeletions. Blood, spermatozoa or testicular cells from 47 men (27 oligozoospermia, 20 azoospermia), including six Y-deleted patients, were screened for mosaicism using double target fluorescence in-situ hybridization (FISH) with Y centromeric and deleted in azoospermia (DAZ) gene-specific probes. Results indicated that: (i) percentages of double (intact Y chromosome) or single (deleted Y chromosome) fluorescent signals by FISH were in agreement with PCR data, thus demonstrating the reliability of the method; and (ii) a weak germ cell mosaicism was found in only two oligozoospermic patients, carrying 1.97 and 4.13% respectively of spermatozoa with a deleted Y chromosome. Further studies on larger populations are needed to evaluate precisely the incidence of Y deletion mosaicisms in infertile men.     

180例无精子症或严重少精子症不育男性的Y染色体微缺失检测

目的探讨不育男性无精子症或严重少精子症与Y染色体微缺失之间的关系.方法利用9个Y染色体特异序列标签位点,以多重PCR法检测无精子症或严重少精子症患者的Y染色体微缺失情况.结果 180例无精子症或严重少精子症患者中共检出Y染色体微缺失15例,缺失率为8.3%.精液正常者(对照组)20例未发现Y染色体微缺失.9例Y染色体微缺失的无精子症患者睾丸细胞学检查均未发现精子.结论 Y染色体微缺失是造成男性精子发生障碍的常见病因之一.     

The human Y chromosome genes BPY2, CDY1 and DAZ are not essential for sustained fertility

Deletions of the AZFc interval of the human Y chromosome are found in >5% of male patients with idiopathic infertility and are associated with a severely reduced sperm count. The most common deletion type is large (>1 Mb) and removes members of the Y-borne testis-specific gene families of BPY2, CDY1, DAZ, PRY, RBMY2 and TTY2, which are candidate AZF genes. Four exceptional individuals who have transmitted a large AZFc deletion naturally to their infertile sons have, however, been described. In three cases, transmission was to an only son, but in the fourth case a Y chromosome, shown to be deleted for all copies of DAZ, was transmitted from a father to his four infertile sons. Here we present a second family of this latter type and demonstrate that an AZFc-deleted Y chromosome lacking not only DAZ, but also BPY2 and CDY1, has been transmitted from a father to his three infertile sons. Polymerase chain reaction (PCR) and Southern blot analyses revealed no difference in the size of the AZFc deletion in the father and his sons. We propose that the father carries rare alleles of autosomal or X-linked loci which suppress the infertility that is frequently associated with the absence of AZFc.     

The Old World monkey DAZ (Deleted in AZoospermia) gene yields insights into the evolution of the DAZ gene cluster on the human Y chromosome.

The DAZ gene cluster on the human Y chromosome is a candidate for the Azoospermia Factor (AZFc). According to the current evolutionary model, the DAZ cluster derived from the autosomal homolog DAZL1 through duplications and rearrangements and is confined to Old World monkeys, apes and humans. To study functional and evolutionary aspects of this gene family we have isolated from a cynomolgus (Old World) monkey testis cDNA library the Y chromosomal cynDAZ and the autosomal cynDAZL1 cDNA. cynDAZL1 contains one DAZ repeat and displays high homology to human DAZL1. cynDAZ comprises 11 repeats, each consisting of exons 7 and 8, whereas the human DAZ cDNA repeat units contain predominantly exon 7. Genomic studies revealed the same amplific- ation events of a 2.4 kb genomic unit encompassing exons 7 and 8 in both species, indicating that after splitting of the two lineages, in the human mainly exon 8 was converted to a pseudoexon by splice site mutations. The structural features of cynDAZ reveal a more detailed model for the sequence of events leading to the present form of human DAZ. Thus, in a monkey species DAZ is present in a form more ancestral than that of the human. Studies on the immunolocalization of cynDAZ / DAZL1 in cynomolgus monkey testis revealed a biphasic expression pattern with proteins being detectable in A-pale to B-spermatogonia, late spermatocytes and spermatids, but not in early spermatocytes and late spermatids. In contrast, in the marmoset monkey, an animal lacking DAZ, DAZL1 protein was only expressed in late spermatocytes and early spermatids. These findings point to an additional function of cynDAZ / cynDAZL1 during spermato- genesis in the Old World monkey not needed in the New World monkey.     

Optical mapping of BAC clones from the human Y chromosome DAZ locus

The accurate mapping of clones derived from genomic regions containing complex arrangements of repeated elements presents special problems for DNA sequencers. Recent advances in the automation of optical mapping have enabled us to map a set of 16 BAC clones derived from the DAZ locus of the human Y chromosome long arm, a locus in which the entire DAZ gene as well as subsections within the gene copies have been duplicated. High-resolution optical mapping employing seven enzymes places these clones into two contigs representing four distinct copies of the DAZ gene and highlights a number of differences between individual copies of DAZ.     

Ultrastructural sperm study in infertile males with microdeletions of Y chromosome

A retrospective study to detect specific Y chromosome microdeletions and to evaluate sperm ultrastructural characteristics in infertile men was set up. We selected 219 infertile men referred to Regional Referral Center for Male Infertility, Siena, Italy for semen analysis from January 1999 to April 2004. Family history, lymphocyte karyotype determination, Y microdeletion screening, physical examination, hormonal assays, semen analysis were carried out. Sperm concentration and progressive motility, ultrastructural analysis of sperm organelles, PCR amplification of sequence tagged sites for Y microdeletion screening were performed. Different Y-chromosome deletions were found, mainly in the AZFb and AZFc regions. Severe alterations of sperm ultrastructure, affecting whole sperm population, were detected in carriers of Y-deletions. Our data confirms the highest frequency of Y deletions in azoospermic patients. In all other patients with Y microdeletions, sperm ultrastructural defects affected the whole sperm population and were mainly related to apoptosis or immaturity.     

Towards the molecular localisation of the AZF locus: mapping of microdeletions in azoospermic men within 14 subintervals of interval 6 of the human Y chromosome.

We have used a series of 30 DNA probes previously mapped to the long arm of the human Y chromosome, to screen a panel of 21 patients with structural abnormalities in Yq, by genomic blot hybridisation. The results have allowed us to construct a detailed map of interval 6 of the Y chromosome, in which 28 of the probes could be assigned to 14 sub-intervals within interval 6. Some probes detect two or more loci within this region, each of which has been localised. The same set of probes has been used to screen a panel of 19 chromosomally normal azoospermic men, two of whom have been found to carry microdeletions within this region. With the completion of this map we have been able accurately to localise these microdeletions within interval 6 and show that they do not overlap. We believe these microdeletions may disrupt the azoospermia factor (AZF) involved in spermatogenesis, and which is known to lie in this region. These results are an important step towards the localisation of the AZF locus.     

无精症及隐匿精子症患者染色体核型与Y染色体微缺失分析

目的 研究无精症和隐匿精子症染色体核型与Y染色体无精因子(azoospermia factor,AZF)微缺失的发生频率及其关系.方法 对997例无精症和隐匿精子症患者进行常规染色体核型分析及多重聚合酶链反应技术检测AZF位点.结果 在997例无精症和隐匿精子症患者中,染色体核型异常检出率28.4%,异常核型包括47,XXY、46,XY(Y＜G)、46,XX、嵌合体及相互易位等.AZF微缺失总检出率17.4%.常见于46,XY及46,XY(Y＜G)等核型.结论 染色体核型异常是无精症和隐匿精子症的重要遗传病因.正常核型与Y＜G患者中存在较高的AZF微缺失率,对这些患者进行AZF微缺失检查有助于明确病因,避免一些不必要的临床治疗及遗传缺陷的垂直传递.     

高促卵泡成熟激素无精子症患者Y染色体微缺失检测

目的　探讨高促卵泡成熟激素 (follicle- stimulating hormone,FSH)无精子症与 Y染色体基因微缺失的关系。方法　采用 PCR技术对 16例高 FSH无精子症患者 Y染色体长臂上 11个序列标记位点进行微缺失的检测。结果　 16例高 FSH无精子症不育男性中 6例存在 Y染色体序列标记位点的微缺失 ,缺失率为 37.5 % (6 / 16 ) ,缺失形式有 5种 ,分别为 AZFc(SY15 2 )、AZFc(SY15 2 SY2 5 4 ) AZFd(SY15 3)、AZFc(SY15 2 SY2 5 4 SY2 5 5 ) AZFd(SY15 3)、AZFc(SY15 2 SY15 8 SY2 5 5 ) AZFd(SY15 3)、AZFb(SY130 ) AZFc(SY15 8 SY2 5 4 SY2 5 5 ) AZFd(SY15 3)。结论　 Y染色体微缺失是高FSH无精子症患者的重要原因之一 ,对高 FSH无精子症患者实施辅助生育技术时非常有必要先进行 Y染色体基因微缺失的检测 ,特别是检测 AZFc、AZFd等区域。