无精子和严重少精子患者Y染色体AZF微缺失的PCR筛查

目的：探讨Y染色体上AZF微缺失与精子生成的遗传效应关系,建立对无精子症和严重少精子患者Y染色体微缺失的筛查方法。方法;本文应用聚合酶链反应（PCR）技术对无精子症和严重少精子患者进行Y染色体上AZFa,AZFb,AZFc等5个基因片段的微缺失检测。结果：在64例无精子患者中,AZFb,AZFc,RBM人率分别为4．69％、17．19％、4．69％、未发现AZFa缺失。在53例严重少精子患者中,除1例同时伴有RBM缺失外,均为AZFc缺失,未发现AZFa和AZFb缺失,缺失率为18．87％。30例正常对照组未发现5个区域缺失。结论：精子发生与Y染色体上的多个基因有关,AZFb,AZFc的微缺失是导致无精子和严重少精子的重要原因,AZFc区微缺失可作病因筛查主要候选基因。     

Y chromosome microdeletions, in azoospermic or near-azoospermic subjects, are located in the AZFc (DAZ) subregion

Submicroscopic deletions of the Y chromosome and polymorphisms of the androgen receptor (AR) gene in the X chromosome have been observed in men with defective spermatogenesis. To further define the subregions/genes in the Y chromosome causing male infertility and its relationship to polymorphisms of the AR polyglutamine tract, we screened the genomic DNA of 202 subfertile males and 101 healthy fertile controls of predominantly Chinese ethnic origin. Y microdeletions were examined with 16 sequence-tagged site (STS) probes, including the RBM and DAZ genes, spanning the AZFb and AZFc subregions of Yq11, and related to the size of trinucleotide repeat encoding the AR polyglutamine tract. Y microdeletions were detected and confirmed in three out of 44 (6.8%) of azoospermic and three out of 86 (3.5%) severely oligozoospermic patients. No deletions were detected in any of the patients with sperm counts of >0.5 x 10(6)/ml, nor in any of the 101 fertile controls. All six affected patients had almost contiguous Y microdeletions spanning the entire AZFc region including the DAZ gene. The AZFb region, containing the RBM1 gene, was intact in five of the six subjects. Y deletions were not found in those with long AR polyglutamine tracts. Our study, the first in a Chinese population, suggest a cause and effect relationship between Y microdeletions in the AZFc region (possibly DAZ), and azoospermia or near-azoospermia. Y microdeletions and long AR polyglutamine tracts appear to be independent contributors to male infertility.      

The use of spermHALO-FISH to determine DAZ gene copy number

The AZFc region of the human Y chromosome is frequently deleted in men with spermatogenic failure and contains many multicopy genes. The best-characterized gene family within this region is the Deleted in AZoospermia (DAZ) gene family, which is present in four nearly identical copies. Recent reports claim deletions of some but not all DAZ genes. The assays used in these studies, however, are unable to provide conclusive evidence on the number of DAZ genes. In this study we show that with the use of highly decondensed sperm nuclei with large DNA domains (spermHALO) it is possible to determine the number of DAZ genes accurately. Using this fluorescent in-situ hybridization (FISH) technique, which has both high resolution and high range, we show that in 10 normospermic men, in which PCR digest assays indicated a deletion of one or more DAZ genes, all four DAZ genes were present. Also we confirmed previous findings of a deletion of two DAZ genes in two men and identified a man with six DAZ genes. Our results indicate that spermHALO-FISH allows an accurate determination of DAZ gene copy number, while PCR digest assays do not. Therefore, confirmation of positive results from PCR digest assays with spermHALO-FISH is essential. Furthermore, the spermHALO-FISH technique should prove useful as a genetic mapping technique in other regions of the Y chromosome and similar repetitive regions throughout the genome.     

Mouse homologues of the human AZF candidate gene RBM are expressed in spermatogonia and spermatids, and map to a Y chromosome deletion interval associated with a high incidence of sperm abnormalities

An RNA-binding motif (RBM) gene family has been identified on the human Y chromosome that maps to the same deletion interval as the 'azoospermia factor' (AZF). We have identified the homologous gene family (Rbm) on the mouse Y with a view to investigating the proposal that this gene family plays a role in spermatogenesis. At least 25 and probably >50 copies of Rbm are present on the mouse Y chromosome short arm located between Sry and the centromere. As in the human, a role in spermatogenesis is indicated by a germ cell-specific pattern of expression in the testis, but there are distinct differences in the pattern of expression between the two species. Mice carrying the deletion Yd1, that maps to the proximal Y short arm, are female due to a position effect resulting in non-expression of Sry ; sex-reversing such mice with an Sry transgene produces males with a high incidence of abnormal sperm, making this the third deletion interval on the mouse Y that affects some aspect of spermatogenesis. Most of the copies of Rbm map to this deletion interval, and the Yd1males have markedly reduced Rbm expression, suggesting that RBM deficiency may be responsible for, or contribute to, the abnormal sperm development. In man, deletion of the functional copies of RBM is associated with meiotic arrest rather than sperm anomalies; however, the different effects of deletion are consistent with the differences in expression between the two species.      

AZF and DAZ gene copy-specific deletion analysis in maturation arrest and Sertoli cell-only syndrome

Deletions of the AZFc region in Yq11.2, which include the DAZ gene family, are responsible for most cases of male infertility and were associated with severe oligozoospermia and also with a variable testicular pathology. To uncover the functional contribution of DAZ to human spermatogenesis, a DAZ gene copy-specific deletion analysis was previously established and showed that DAZ1/DAZ2 deletions associate with oligozoospermia. In this study we applied the same screening method to 50 control fertile males and 91 non-obstructive azoospermic males, 39 with Sertoli cell-only syndrome (SCOS) and 52 with meiotic arrest (MA). Samples were also screened with 24 sequence-tagged sites to the different AZF regions, including 114 control fertile males. After biopsy (testicular sperm extraction, TESE), residual spermiogenesis was found in 57.7% MA and 30.8% SCOS cases (incomplete syndromes). DAZ1/DAZ2 deletions were associated with the testicular phenotype of residual spermiogenesis as they were only found in two patients (8%) with incomplete MA. Differences between incomplete (23.3%) and complete (4.5%) MA cases regarding AZFc and DAZ1/DAZ2 deletion frequencies, and between incomplete (58.3%) and complete (11.1%) SCOS cases for AZFc deletions, suggest that incomplete syndromes might represent an aggravation of the oligozoospermic phenotype. As successful TESE was achieved in 87.5% of MA cases with AZFc and DAZ1/DAZ2 deletions and in 58.3% of SCOS cases with AZFc deletions, the present results also suggest that these molecular markers might be used for the establishment of a prognosis before TESE.     

Screening for microdeletions of Y chromosome genes in patients undergoing intracytoplasmic sperm injection.

The potential of assisted reproduction techniques to transmit genetic defects causing male infertility raises questions concerning the need for a systematic genetic screen and counselling. Deletions of the long arm of the Y chromosome are frequently associated with a failure of spermatogenesis. The search for Y specific sequences and for the gene families RNA binding motif (RBM) and deleted in azoospermia (DAZ) have been introduced in many laboratories. The incidence of Y microdeletions varies widely between studies, from 1-55%. These differences are mainly related to study design. The highest incidence of microdeletions has been reported in well selected idiopathic azoospermic patients. Since microdeletions have been reported also in non-idiopathic patients, it is important to define what is the deletion frequency in unselected patients. We report Y chromosome microdeletion screening in 134 unselected patients undergoing intracytoplasmic sperm injection (ICSI). In the first part of the study we tested six Y chromosome markers. We found three patients with microdeletions (2.2%). Subdivision of the study population revealed a deletion incidence of 4.7% in azoospermic/cryptozoospermic patients; an incidence of 7% in idiopathic patients and an incidence of 16% in idiopathic azoospermic/cryptozoospermic patients. The second part of the study consisted of a screen for the presence of the Y chromosome genes, DBY, CDY, XKRY, eIF-1A, DAZ and BPY2. No additional gene-specific deletions were found. Further data on gene specific screening are needed especially for selected idiopathic patients.     

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.     

Partial rescue of the Dazl knockout mouse by the human DAZL gene

Y-chromosomal DAZ (deleted in azoospermia) and autosomal DAZ-like (DAZL) comprise a gene family involved in gametogenesis. Y-chromosomal and autosomal genes only co-exist in humans and old world monkeys, indicating that DAZ genes are a recent acquisition of the Y chromosome. In most mammals, the ancestral Dazl alone is sufficient to complete gametogenesis. It is not yet understood why humans and old world monkeys have a second set of genes that are apparently necessary for spermatogenesis, since deletions removing the Y-chromosomal DAZ are often associated with azoo- or oligospermia. We used transgenic mice carrying either human DAZL or human DAZ on a mouse Dazl null background to investigate the functions of the human homologues. Both transgenes enabled prophase spermatocytes to be produced, mainly of the leptonema/zygonema stage, but failed to promote differentiation into mid- to late pachytenes. The presence of human DAZL resulted in a larger amount of early germ cells compared with that observed in DAZ. The degree of rescue was independent of copy number, integration site or presence of the DAZ repeat region for the DAZ transgenes. These findings confirm that DAZL and DAZ can only substitute for early functions of the murine homologue resulting in the establishment of the germ cell population and partial progression into meiosis.     

特发性无精子症及少弱精子症患者Y染色体AZF微缺失筛查分析

目的探讨特发性无精子症及少弱精子症不育男性与Y染色体AZF微缺失的关系.方法用双重PCR技术对63例患者(无精于症41例,少弱精子症14例,严重少精子症8例)进行Y染色体AZFa、AZFb、AZFc、SRY的微缺失筛查.同时对26例无精于症患者行睾丸活检、组织学评估.结果63例中AZF微缺失7例,缺失率为11.1%.其中无精子症5例,严重少精子症2例.AZFc缺失4例,AZFb缺失2例,AZFb AZFc缺失1例,未发现AZFa区缺失.63例及对照组30例SRY基因扩增均阳性.26例无精子症患者行睾丸活检、组织学检查,无1例精子发生正常.结论Y染色体微缺失,特别是AZFc区DAZ基因的微缺失,是引起无精子和严重少弱精子等生精障碍而致男性不育较为重要的遗传学因素.     

AZF缺失患者Y染色体断裂点定位分析

目的 分析导致无精子因子区域(azoospermia factor,AZF)缺失的Y染色体断裂的特点.方法 在272例无精子症、240例严重少精子症患者进行Y染色体AZF微缺失筛查基础上,对筛查发现大片段缺失的49例患者,选择AZFa、AZFb、AZFc区23个序列标签位点(sequence tagged site,STS),对断裂点进行定位分析.颖有无精子症缺失基因家族(deletedin azoospermia,DAZ)、基因部分拷贝缺失病例进行单核苷酸多态性(single nuecleotide varians,SNV)缺失分析以确定DAZ基因的拷贝数.结果 6例AZFb+C缺失患者,1例为sY98/sY1206缺失,4例为P5/P1远端重组,1例为P4/P1远端重组.3例筛查发现AZFb区缺失患者,1例为P5/P3缺失,2例为P5/P1近端重组,伴有DAZ1、DAZ2拷贝缺失.40例AZFc区全缺失患者,均为b2/b4同源重组.部份AZFb、AZFb+c缺失患者,睾丸穿刺活检发现精子生成减少或精子成熟障碍.结论 对Y染色体AZF大片段缺失断裂点的大致定位有利于判断缺失发生机制,进而分析丢失的生精相关基因拷贝性质与数量,以评价其与生精障碍表型之间的关联.     

Additional genomic duplications in AZFc underlie the b2/b3 deletion-associated risk of spermatogenic impairment in Han Chinese population

The azoospermia factor c (AZFc) region on the Y chromosome is a genetically dynamic locus in the human genome. Numerous genomic rearrangements, including deletion, duplication and inversion, have been identified in AZFc. The complete deletion of AZFc can cause spermatogenic impairment. However, the roles of partial AZFc deletions (e.g. b2/b3 deletion) in spermatogenesis are controversial and variable among human populations. Secondary duplication has been hypothesized to be a compensatory factor for partial AZFc deletions. To further study genomic duplications in AZFc as a potential genetic modifier underlying the phenotypic variations of partial AZFc deletions in spermatogenesis, we conducted comprehensive molecular analyses in 711 idiopathic infertile men and 390 healthy controls. Unexpectedly, we found that additional AZFc duplications accompanying the b2/b3 deletion, instead of the b2/b3 deletion alone, led to the b2/b3 deletion-associated risk of spermatogenic impairment previously reported in Han Chinese population. In addition, partial AZFc duplication also rendered a risk factor in the non-deletion patients. DAZ is a multi-copy AZFc gene (DAZ1-DAZ4) implicated in spermatogenesis. Genetic variations do exist between DAZ copies. Intriguingly, we found that the DAZ1/2 cluster was the main duplicated copies in the partial AZFc duplications associated with spermatogenic impairment, suggesting a potential different role of spermatogenesis between DAZ copies. Our findings demonstrated that additional AZFc duplications did not compensate but convey the susceptibility of the b2/b3 deletion to spermatogenic impairment in the tested population. Notably, genomic duplications and deletions in AZFc deserve comprehensive investigations to uncover spermatogenic roles of the AZFc region.     

AZFc区gr/gr及DAZ基因拷贝缺失与原发性男性生精障碍的相关性研究

目的探讨Y染色体AZFc区gr/gr缺失及DAZ基因拷贝缺失与男性生精障碍的相关性。方法运用PCR与PCR-RFLP检测技术,对252例正常生精男性,430例原发性生精障碍男性患者进行Y染色体AZFc区gr/gr缺失及DAZ基因拷贝缺失分析。结果正常生精男性组gr/gr缺失率为5.2%,原发性生精障碍组gr/gr缺失率为10.2%,P=0.021,差异有统计学意义;正常生精男性组DAZ1/DAZ2基因拷贝共缺失率为2.0%,原发性生精障碍组中DAZ1/DAZ2基因拷贝共缺失率为7.0%,P=0.004,差异亦有统计学意义;正常生精男性组DAZ3/DAZ4基因拷贝共缺失率为3.2%,在生精障碍组中DAZ3/DAZ4基因拷贝的共缺失率为3.3%,P=0.954,差异无统计学意义。结论在原发性男性生精障碍患者中存在较高频率的gr/gr缺失及DAZ1/DAZ2基因共缺失,提示gr/gr缺失及DAZ1/DAZ2基因拷贝的共缺失是男性不育的高风险因子。     

Transmission of a Y chromosomal deletion involving the deleted in azoospermia (DAZ) and chromodomain (CDY1) genes from father to son through intracytoplasmic sperm injection: case report.

The transmission of a deleted in azoospermia (DAZ) deletion from a severely oligozoospermic patient to his son following intracytoplasmic sperm injection (ICSI) treatment is reported. The case report highlights the fertilizing capacity of spermatozoa carrying Y chromosome deletions in patients treated with ICSI and stresses the importance of genetic counselling in severe male infertility.     

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.     

A deletion of a novel heat shock gene on the Y chromosome associated with azoospermia

Deletions of the Y chromosome are a significant cause of spermatogenic failure. Three major deletion intervals have been defined and termed AZFa, AZFb and AZFc. Here, we report an unusual case of a proximal AZFb deletion that includes the Y chromosome palindromic sequence P4 and a novel heat shock factor (HSFY). This deletion neither include the genes EIF1AY, RPS4Y2 nor copies of the RBMY1 genes. The individual presented with idiopathic azoospermia. We propose that deletions of the testis-specific HSFY gene family may be a cause of unexplained cases of idiopathic male infertility. This deletion would not have been detected using current protocols for Y chromosome microdeletion screens, therefore we recommend that current screening protocols be extended to include this region and other palindrome sequences that contain genes expressed specifically in the testis.     

Partial duplication at AZFc on the Y chromosome is a risk factor for impaired spermatogenesis in Han Chinese in Taiwan

The Azoospermia Factor c (AZFc) region on the Y chromosome long arm is one of the least stable regions in the human genome. It consists almost entirely of very long repeats and is prone to rearrangement. Numerous structures at AZFc have been identified, and some of them have been reported to be associated with male infertility. We screened 580 Han Chinese in Taiwan for AZFc deletion and duplication using three PCR assays, and characterized the DAZ genes in selected subjects with additional Southern analyses. About 9.5% of our subjects have AZFc partial deletion, 2.8% have partial deletion followed by duplication, and 1.7% have partial duplication. The overall rearrangement frequencies vary significantly between different Y chromosome haplogroups (Yhgs), ranging from 2.9% in O3e to 100% in N and Q. All individuals in Yhg-N lack the sY1191 marker, but one out of three of them actually have four DAZ genes, indicating further duplication after the b2/b3 deletion. Our additional screening of 142 oligospermic men and 107 fertile controls found no significant difference in the frequencies of the gr/gr and the b2/b3 deletion. However, the frequency of AZFc partial duplication in the infertile group (7.0%) was significantly higher than that in the fertile control group (0.9%) and the general Taiwanese population (1.7%). Our results indicate that AZFc partial deletion and partial duplication are common polymorphisms in Han Chinese, and that the AZFc partial duplication, but not the AZFc partial deletion, is a risk factor for male infertility in the Taiwanese population.     

精子发生障碍患者Y染色体微缺失的研究

目的研究无精子症和少精子症患者Y染色体上无精子症因子(azoospermicfactor,AZF)微缺失情况,建立Y染色体微缺失的分子诊断的临床筛查方法,分析原发性无精子症和少精子症患者与Y染色体微缺失的关系。方法采用多重PCR、凝胶电泳技术对56例无精子症和少精子症患者的10个STS位点或基因进行检测与筛查。结果20例精子密度正常的生育男性未检测出Y染色体微缺失;56例无精子症和少精子症患者中有9例有AZF区域的微缺失,总缺失率16.1%(9/56),AZFc/DAZ区发生微缺失频率较高。结论Y染色体微缺失是导致男性不育患者精子发生障碍的重要原因之一,AZF侯选基因在精子发生过程中可能起重要作用。     

Y染色体微缺失35例患者临床表型分析

目的分析35例Y染色体微缺失患者临床表型。方法按照WHO标准进行检查和精液分析,证实为非梗阻性无精子症或严重少精子症（〈1×10^6／mL）367例,然后应用改良多重多聚酶链反应（multiplex—PCR）,对367例不育患者进行Y染色体微缺失分子学诊断。将微缺失患者分为两组：严重少精子组和无精子组。再按缺失类型将无精子组分为两个亚组：单纯AZFc缺失组和其它类型缺失组。采集以下临床资料进行分析：结婚年龄、不育史、精液分析、睾丸体积、附睾睾丸穿刺情况、染色体核型分析以及性激素检测。结果367例中发现AZF微缺失35例（9．54％）,其中AZFa、AZFb微缺失各1例（2．86％）,AZFc微缺失29例（82．86％）,AZFb＋c微缺失2倒（5．71％）,AZFa＋b＋c微缺失2例（5．71％）。严重少精子患者14例,缺失类型均为AZFc;无精子症患者21例,其中对12例无精子症患者行睾丸穿刺活检,2例AZFc微缺失患者发现精子。其中未发现输精管缺如患者。染色体核型分析2例AZFc微缺失患者发现异常,其余均为46,XY。严重少精子组与无精子组患者年龄、不育年限、黄体生成素、雄激素及出生时父亲年龄无统计学差异,卵泡刺激素有统计学差异。结论 临床表型、染色体核型正常的严重少弱精子或无精子症患者可存在Y染色体微缺失,其发生率约为10％,最常见的类型为AZFc微缺失。单纯AZFc缺失对精子生成的影响比其他类型缺失较小,无精子症AZFc缺失者行睾丸穿刺活检有可能发现可用精子,AZFa、AZFb或AZFa＋b＋c缺失者基本不可能有精子,临床上无睾丸活检的价值。     

High frequency of DAZ1/DAZ2 gene deletions in patients with severe oligozoospermia

Deletions of the DAZ gene family in distal Yq11 are always associated with deletions of the azoospermia factor c (AZFc) region, which we now estimate extends to 4.94 Mb. Because more Y gene families are located in this chromosomal region, and are expressed like the DAZ gene family only in the male germ line, the testicular pathology associated with complete AZFc deletions cannot predict the functional contribution of the DAZ gene family to human spermatogenesis. We therefore established a DAZ gene copy specific deletion analysis based on the DAZ-BAC sequences in GenBank. It includes the deletion analysis of eight DAZ-DNA PCR markers [six DAZ-single nucleotide varients (SNVs) and two DAZ-sequence tag sites (STS)] selected from the 5' to the 3'end of each DAZ gene and a deletion analysis of the gene copy specific EcoRV and TaqI restriction fragments identified in the internal repetitive DAZ gene regions (DYS1 locus). With these diagnostic tools, 63 DNA samples from men with idiopathic oligozoospermia and 107 DNA samples from men with proven fertility were analysed for the presence of the complete DAZ gene locus, encompassing the four DAZ gene copies. In five oligozoospermic patients, we found a DAZ-SNV/STS and DYS1/EcoRV and TaqI fragment deletion pattern indicative for deletion of the DAZ1 and DAZ2 gene copies; one of these deletions could be identified as a 'de-novo' deletion because it was absent in the DAZ locus of the patient's father. The same DAZ deletions were not found in any of the 107 fertile control samples. We therefore conclude that the deletion of the DAZ1/DAZ2 gene doublet in five out of our 63 oligozoospermic patients (8%) is responsible for the patients' reduced sperm numbers. It is most likely caused by intrachromosomal recombination events between two long repetitive sequence blocks (AZFc-Rep1) flanking the DAZ gene structures.     

A two-step protocol for the detection of rearrangements at the AZFc region on the human Y chromosome

The AZFc region on the human Y chromosome consists mainly of very long direct and inverted repeats and is prone to rearrangement. Although deletion of the entire AZFc is found only in subfertile men, duplications and deletions of portions of AZFc as well as inversions are quite common and represent major polymorphisms of the Y chromosome. Several methods are available to detect these rearrangements, and each has its own advantages and limits. We designed a two-step PCR protocol to study the polymorphic structure of AZFc. The first PCR determines the copy number of the Deleted in Azoospermia (DAZ) genes within AZFc using the autosomal DAZ-Like gene as a dosage control, and the results could be verified by dosage Southern blot analyses. The second PCR simultaneously detects five sequence tagged sites (STSs) that are either present or absent in the various AZFc partial deletions. One of the STSs, sY1291, was found to be polymorphic in size due to varying lengths of a poly-T stretch. A combination of the DAZ dosage PCR and the 5-STS multiplex PCR reaction detects most, if not all, deletions and duplications at AZFc. It offers a simple and reliable way to screen large populations for AZFc rearrangements and study their effects on male fertility.