AZF微缺失与男性不育

Y染色体是男性特有的染色体,其上含有与精子发生相关的基因。越来越多研究证实AZF区基因微缺失与男性不育密切相关,并且可能以正常生殖或辅助生殖方式遗传给后代引起不育。本文从Y染色体微缺失基因类型、Y染色体缺失机制及Y染色体微缺失的临床意义三个方面综述。     

Turner综合征Y染色体物质嵌合分子遗传学研究

摘要：目的　分析Turner综合征（TS）患儿Y染色体物质及衍生物嵌合发生的情况，为TS患儿诊断后的监测提供科学建议，改善国内TS监测和保健管理的现状。方法　选取2006年2月至2007年8月在重庆医科大学附属儿童医院诊断为TS患儿30例，进行基因组DNA 的Y编码睾丸特异性蛋白基因（TSPY）、 Y染色体中心着丝粒DYZ3重复序列（DYZ3 ）和Y性别决定区域（SRY）3个Y染色体特异序列多聚酶链反应（PCR）检测，反应结果阳性的病例补充SRY探针原位荧光杂交（FISH）分析。结果　基因组DNA 的PCR结果显示，3例患儿的TSPY、 DYZ3扩增均为阳性（10.00%），其中只有1例 SRY 扩增阳性（3.33%）；3例Y染色体物质阳性病例进一步进行FISH研究，结果显示3例SRY杂交信号均为阳性。结论　运用3个Y染色体特异序列的分子遗传学研究，证实Y染色体物质嵌合在TS不少见，每一个TS患儿都应在诊断后进行Y染色体物质的分子遗传学监测。     

Y染色体单倍群与精子发生相关性

Y染色体上存在众多精子发生的相关基因。在Y染色体进化过程中形成可稳定遗传的碱基突变位点:SNP位点。根据Y染色体SNP位点不同,把全球人群分为153个单倍群(haplogroup)。大量研究显示,Y染色体无精子因子(azoospermia factor,AZF)区基因重组引起的缺失是导致男性不育的重要原因。常见的缺失类型为AZFa、AZFb、AZFc、AZFbc、AZFabc,以及AZFc区的部分缺失:gr/gr缺失、b2/b3缺失。目前研究表明,Y染色体单倍群不但与精子发生相关,而且与Y染色体微缺失相关,即某些单倍群易发生Y染色体微缺失而导致男性不育。     

男性不育中Y染色体微缺失的研究进展

近年来对男性不育的遗传学因素的广泛研究显示Y染色体微缺失是导致不同程度生精障碍从而引起男性不育的第二大遗传学病因。无精子症因子区(AZF区)由近至远包含3个不同的亚区:AZFa、AZFb和AZFc,不同缺失类型的表型不同。目前常采用PCR法进行Y染色体微缺失的检测,其缺点是准确度低、特异性差、耗时。而基因芯片技术虽能克服上述缺点,但目前成本过高。通过检测能预测患者男性后代的遗传风险,有助于患者选择辅助治疗的方式。虽然Y染色体微缺失的严重不育患者能通过辅助生殖技术成功获得后代,但有可能将遗传缺陷传给男性后代,使之获得相同的Yq微缺失和不育。     

胎儿染色体疾病及单基因疾病非侵入性产前诊断

胎儿染色体疾病及单基因疾病是较常见的出生缺陷。染色体病是由于染色体数目或结构异常而发生的疾病,其中染色体数目异常比结构异常更为常见。染色体的数目异常可表现为非整倍体及多倍体。常见的结构异常有缺失、环状染色体、易位、重复、倒位和等臂染色体。细胞遗传学是经典的诊断方法。胎儿单基因病可因一个(对)基因的突变,或由双亲单基因遗传病按孟德尔法则遗传至后代。目前已知的单基因遗传病有3000余种。分子遗传学、免疫生化学等是目前常用的诊断方法。非侵入性产前诊断胎儿染色体疾病及单基因疾病有赖于可靠的实验室方法及获取可用于…     

精子发生障碍患者Y染色体微缺失分子诊断

目的:通过建立的Y染色体微缺失筛查方法了解生精障碍与Y染色体微缺失的关系。方法:同时采用多重PCR-凝胶电泳技术和多重PCR-液态芯片技术对原发性无精症、少精症患者和精液常规正常男性对照进行Y染色体微缺失筛查。结果:42例无精症、少精症患者中,6例有AZF区域STS位点或基因的缺失,总缺失率为14.3%,AZFc/DAZ区发生微缺失的频率较高,AZFa区发生微缺失的频率较低。结论:本研究建立的Y染色体微缺失多重PCR-MASA检测系统具有相对高通量、简便、快速、特异性强、敏感性高等特点;染色体微缺失是导致男性精子发生障碍的重要原因之一,AZF的候选基因在精子发生过程中可能起重要作用。     

子宫肌瘤相关基因研究

近年子宫肌瘤分子遗传学研究主要集中在HMGI-C/HMGI(Y)基因上,其结构改变,酸性尾丢失,AT-钩作用增强,促进子宫肌瘤细胞增殖。与HMGI-C/HMGI(Y)相对应的若干融合配对基因具有有限的协同作用。原癌基因c-fos可能抑制子宫肌瘤向恶性转化。雌激素受体(ER)β基因的作用值得进一步关注和研究     

Y染色体微缺失与辅助生殖技术关系的研究进展

Y染色体是男性特有的染色体,其长臂上的无精子因子(AZF)区域具与男性不育密切相关的基因,目前将该区域分为AZFa、AZFb、AZFc和AZFd4个区域。AZF缺失是导致男性不育的重要因素之一,可以通过辅助生殖技术(ART)遗传给下一代引起不育。研究Y染色体微缺失分类与表型关系,可以为临床治疗各种男性不育症提供分子或细胞水平的依据。Y染色体微缺失发生频率存在种族差异性;目前Y染色体微缺失的检测方法仍然以多重PCR为主;对于ICSI助孕的男性后代是否会出现新发Y染色体微缺失仍然存在争论。     

子宫肌瘤相关基因研究

近年子宫肌瘤分子遗传学研究主要集中在HMGI-C/HMGI(Y)基因上,其结构改变,酸性尾丢失,AT-钩作用增强,促进子宫肌瘤细胞增殖.与HMGI-C/HMGI(Y)相对应的若干融合配对基因具有有限的协同作用.原癌基因c-fos可能抑制子宫肌瘤向恶性转化.雌激素受体(ER)β基因的作用值得进一步关注和研究.     

卵巢癌的遗传学研究进展

卵巢癌的遗传学研究进展卞美璐，郎景和近十年来，对妇科卵巢癌遗传学的研究进展迅速。如在细胞水平上，发现了染色体在数目和结构上的异常；在分子水平上，发现了某些癌基因及抑癌基因的作用。这些研究，为从遗传学角度探讨卵巢癌的发病机理提供了重要依据，并为临床上对...     

Studies on the control mechanism of hCG beta gene expression--focusing on identification of promoter and other transcriptional regulatory elements

hCG beta gene is composed of 6 genes or pseudogenes. To find which of these 6 genes are active and which are inactive, a cosmid clone containing the entire hCG beta gene cluster, which we had isolated previously, was separated into subclones containing each gene. Then they were transfected into mouse Y1 cells which express this gene efficiently. The result showed that genes 5, 3 and 8 are active and the rest are inactive. To identify the promoter region of gene 5, which is the most active gene, we created deletion mutants lacking various lengths of gene 5 upstream sequence. We made them either by using restriction endonuclease or Exonuclease III. We transfected them into Y1 cells and studied which part of the upstream sequence is required for hCG beta expression. The results of this experiment show that the promoter region for hCG beta is located within 78bp of the cap site and there are additional regulatory elements upstream. The information obtained here provides a foundation for analytical studies on nuclear factors binding to this region regulating hCG beta expression.     

The Y chromosome and its role in testis differentiation and spermatogenesis

The Y chromosome contains genes and gene families that play critical roles in the processes of testis determination and testis differentiation. Great strides have been made toward defining the genetic pathways associated with the determination of gender. The data are summarized and discussed and clinical ramifications are considered.     

Fetal cells in the maternal circulation: detection of Y-sequence by gene amplification.

Detection of a Y-specific sequence in the maternal circulation has clinical importance because it would be useful in determining fetal gender in mothers with severe X-linked disorders. The method described in this paper has the advantage of requiring only small amounts of maternal blood. Numerous attempts have been made to identify XY cells in the blood of mothers bearing male fetuses; however, the results have been controversial. In this study, a member of the DYZ1 family and the XY homologous region of the amelogenin gene were used as targets for polymerase chain reaction detection of the Y chromosome. The subjects in this study were a group of 100 pregnant women at 17-20 weeks' gestation and 30 puerperal women who had given birth 2-5 days previously. All of the former underwent amniocentesis, with venous blood samples drawn before the procedure. Forty-five fetuses were confirmed as male by karyotyping amniocytes, and 30 of these were positive for the Y sequence in the DYZ1 region (sensitivity 66.7%). However, ten of the 55 cases diagnosed as female were also positive, giving a specificity of only 81.8%. Thus, the positive and negative predictive values were each 75%. In the amelogenin gene study, a positive Y signal was not detected in any of the cases examined. This study demonstrates the usefulness of polymerase chain reaction detection of Y-specific sequences in the maternal circulation. However, further investigation is necessary to increase the reliability for clinical application, because the method does produce false-positive results.     

Analysis of the hemochromatosis mutations C282Y and H63D in infertile men

The aim of this study was to find out whether C282Y and H63D mutations in the hemochromatosis (HFE) gene are associated with male infertility and whether the prevalence of the HFE mutations is higher in a group of 262 infertile men in comparison to 200 fertile men. Because the C282Y and H63D HFE gene distributions in infertile men were not significantly different from fertile controls, our data suggest that the C282Y and H63D HFE gene mutations are not risk factors for male infertility and are not associated with clinical manifestations of male infertility.     

Genotype analysis of the neuropeptide Y (NPY) Y1 and NPY Y5 receptor genes in gonadotropin-releasing hormone-dependent precocious gonadarche

To test whether GnRH-dependent precocious puberty (precocious gonadarche) is associated with loss-of-function mutations in the genes encoding the NPY Y1 and Y5 receptors, we used single-stranded conformation polymorphism analysis to assess for mutations in 15 patients with precocious gonadarche (mean age, 6.84 ± 2.07 years) and in 72 controls. Although variants were not identified in the NPY Y1 receptor gene, 4 patients and 20 control subjects carried a G→A transition resulting in a silent variant, G426G, suggesting that NPY Y1 and Y5 receptor variants do not play a major role in our patient population.     

Current concepts of human azoospermia and its causes

Infertility is a serious social problem in advanced nations today. One of the most important causes is the male factor. Striking progress has been achieved in recent years in elucidating the mechanisms of spermatogenesis in mice by experimental methods represented by the knockout mouse. Although many factors associated with male infertility are known in mice, the translation of this information to people has been slow. This is because the knockout mouse phenotype cannot necessarily be reproduced faithfully in humans. However, it is known that environmental factors, chromosomal defects and several specific gene mutations result in human male infertility. In this review, we first discuss the environmental factors considered likely to be involved in male infertility, and secondly we describe the Y chromosome and several important genes on the Y chromosome that play critical roles in spermatogenesis in humans. Then, we demonstrate the three critical genes identified in our laboratory in autosomes involved in human spermatogenesis, the SYCP3, MEI1 and PARP-2. Finally, we explain the future directionality and possibilities of research in this field.     

Screening for mutations in the SRY gene in patients with mixed gonadal dysgenesis or with Turner syndrome and Y mosaicism

OBJECTIVE: To investigate the presence of mutations in the open reading frame (ORF), as well as on the 5' and 3', flanking regions of the SRY gene in patients with mixed gonadal dysgenesis (MGD) or with Turner syndrome (TS) and Y mosaicism. STUDY DESIGN: We studied 13 patients with MGD and three patients with TS and Y mosaicism. DNA was isolated from blood leukocytes for subsequent polymerase chain reaction (PCR) and direct sequencing were performed in the ORF, as well as from the 5' and 3' flanking regions of the SRY gene. RESULTS: No mutations were present in any of the patients studied. CONCLUSION: The absence of mutations in these regions indicated that mutations were an unlikely cause of MGD or TS with Y mosaicism and suggested that there are others genes playing an important role in sex development.     

Y chromosome mosaicism and occurrence of gonadoblastoma in cases of Turner syndrome and amenorrhoea

In the present study, 73 cases with a clinical diagnosis of Turner syndrome, or with primary or secondary amenorrhoea without frank Turner phenotype, were evaluated for presence of low level Y chromosome mosaicism using molecular methods. Fluorescence in-situ hybridization for centromere and q arm of the Y chromosome and nested polymerase chain reaction for the sex determining region on Y (SRY) gene were performed in peripheral blood, buccal cells and gonadal biopsies. The overall frequency of Y chromosome mosaicism was found to be 18% (13/73 cases). Four cases (16%) of Turner syndrome had Y chromosome mosaicism, seven cases (28%) with primary amenorrhoea and two cases (9%) with secondary amenorrhoea had Y chromosome mosaicism. Histologically detectable gonadoblastoma was observed in one of seven cases (14%) that had Y chromosome mosaicism. This frequency is lower than that reported previously, underscoring the need for large prospective investigations to determine the frequency of Y chromosome mosaicism and occurrence of gonadoblastoma in cases of Turner syndrome and other forms of amenorrhoea.     

Deoxyribonucleic acid analysis of the zinc finger Y gene in 45,X/46,XY subjects

The deoxyribonucleic acid from nine subjects with a 45,X/46,XY karyotype with a cytogenetically intact Y chromosome and phenotypically presenting with bilateral streak gonads, streak and testis, or bilateral scrotal testes along with a control male and female were analyzed for the presence of the zinc finger Y sequence through the molecular probe pDP1007. This particular probe is thought to constitute part of the putative testicular-determining factor gene. All the study subjects demonstrated the presence of zinc finger Y. Laser densitometry studies confirmed a correlation between the intensity of the zinc finger Y band and the percentage of Y cell lines. This study supports the fact that individuals with mixed gonadal dysgenesis and cytogenetically intact Y chromosomes will tend to have intact zinc finger Y sequences.