miRNAs与精子发生研究进展

精子发生过程包括精原干细胞的有丝分裂、精母细胞的减数分裂和精子变态形成3个阶段,该过程涉及一系列复杂的转录后表达调控。微小核糖核酸(miRNA)作为非编码RNA的一种,研究证实其在转录后的表达调控中发挥非常重要的作用。很多研究显示miRNA在睾丸组织中广泛表达,参与不同阶段精子形成生殖细胞的成熟和分化。本文将从miRNA在睾丸发育、精原干细胞自我更新和分化,减数分裂及减数分裂后精子分化等方面中发挥的重要作用进行综述。     

性腺的组织发生与卵巢肿瘤的分类

本文观察了胚胎发育与性腺的组织发生,并以此作为研究卵巢肿瘤病理的基础。选择了宫外孕,人工流产,剖腹产和新生儿死婴共9例,按不同受精胚龄或胎龄的胚胎或胎儿发育,分别寻找性腺,从未分化性腺、男女性腺的各阶段的发育特征,进一步认识卵巢肿瘤分类的多样性和多类型性。根据性腺的形成基础可将卵巢肿瘤分为上皮性,性腺间质性、生殖细胞性、非特殊间质性和转移性5大类。     

人类原始生殖细胞的起源、迁移、增殖及凋亡过程

人类原始生殖细胞(PGC)是人卵母细胞的祖细胞,是人类生存及繁衍后代的重要细胞。PGCs起源于性腺外,经迁移到达生殖嵴与体细胞共同组成生殖腺;之后,PGCs在性腺内经增殖、分化等一系列复杂的变化最终形成成熟的卵子。认识PGCs的起源、迁移、增殖、分化等过程对生殖医学具有重要意义。目前对禽类及小鼠PGCs的研究已取得深入进展,由于人PGCs不易获得,且受到伦理、道德及宗教方面的制约,有关人生殖细胞的研究进程较缓慢,对人PGC的起源及迁移过程等都不甚清楚,现就生殖细胞的起源、迁移、增殖及凋亡过程的研究进展作一概述。     

小鼠精巢生殖细胞减数分裂各时相识别

目的 :识别鉴定哺乳动物小鼠精巢生殖细胞减数分裂各时相细胞。方法 :结合减数分裂过程染色体变化及秋水仙素抑制纺锤体形成原理,分析观察改良制作小鼠精巢生殖细胞减数分裂染色体标本,比较各时期细胞及染色体形态变化。结果 :鉴定出小鼠减数分裂第1次分裂、第2次分裂及精子形成过程各细胞形态特征图谱,并详细解析了识别各时期细胞染色体构型变化要点,同时也简要阐述了秋水仙素的应用对识别细胞各时相染色体的影响。结论 :小鼠精巢生殖细胞减数分裂染色体变化复杂,建立完整的清晰图谱可为减数分裂课程教学及染色体异常研究提供参考。     

人胚胎睾丸生殖细胞发育的组织学和超微结构研究

用光镜与电镜技术，对１５例７至２８周人胚胎睾丸生殖细胞的发育进行了研究。结果：（１）据时间，位置及形态结构特点，将生殖细胞的发育过程初步分为三个阶段，即原始生殖细胞阶段，生殖母细胞阶段和前的细胞阶段。其中前精原细胞阶段又经历了早，中，晚三上时期各期出现的时间有交错。（２）１４周是胚胎生殖细胞发育的一个重要时期。     

染色体平衡易位的夫妇进行遗传咨询的意义--附三例成功生育报告

染色体平衡易位者表型正常,因其不伴有遗传物质-基因的丢失,从而保持了体细胞内遗传物质的稳定,使个体表型正常,但其配子(精子或卵子)需由生殖细胞经减数分裂形成,其染色体数目减少一半,由双倍体变成单倍体,所以染色体平衡易位者的配子却伴有遗传基因的增减,其形成合子时导致染     

人胚胎干细胞表达生殖细胞分化相关基因的研究

目的 探讨人胚胎干细胞(hES)系H1生殖细胞分化相关基因的表达.方法 免疫荧光、碱性磷酸酶检测和核型分析等方法联合鉴定H1的基本生物学特性,RT-PCR方法检测未分化H1的生殖细胞分化相关基因的基本表达模式,分别以人正常睾丸组织和人胚胎成纤维细胞株HFF-1作为阳性和阴性对照组织.结果 H1保持正常核型并维持未分化状态.未分化H1表达减数分裂前生殖细胞标志基因STELLAR、DAZL、FRAGILIS、PUM1、PUM2和GDF3;不表达原始生殖细胞(PGCs)标志基因BLIMP-1、减数分裂特异标志基因SCP1、减数分裂启动标志基因STRA8以及生殖细胞分化后期标志基因VASA.结论 未分化Hl细胞表达生殖细胞减数分裂前标志基因,但不表达分化后期基因,BLIMP-1可能成为区分未分化hES细胞与PGCs的特异性标志基因.     

B细胞发育的几个重要阶段

Ｂ细胞的发育经历多个连续变化阶段，各阶段的细胞表面标志、免疫球蛋白基因片段重排状态等均有显著不同。本文综述了自造血干细胞至成熟Ｂ细胞发育过程中各阶段细胞的主要特征，讨论了其与某些Ｂ系疾病的关系。不同发育期Ｂ细胞离体培养技术的建立及分子生物学高新技术的发展将进一步促进Ｂ细胞发育分化及相关疾病的研究。     

人胚胎干细胞系chHES-20表达生殖细胞分化相关基因

目的 探讨人胚胎干细胞系chHES-20能否表达生殖细胞分化相关基因. 方法 反转录-聚合酶链式反应(RT-PCR)检测chHES-20细胞系生殖细胞特异基因的表达情况,以人正常睾丸组织作为阳性对照,以人成纤维细胞为阴性对照. 结果 胚胎干细胞系chHES-20表达全能性相关基因OCT4、NANOG和SOX2,同时表达减数分裂前生殖细胞标志基因DAZL和FRAGILIS;不表达减数分裂特异标志基因联会复合体基因3(SCP3)和生殖细胞分化后期标志基因VASA. 结论 chHES-20胚胎干细胞系具有向生殖细胞诱导分化的潜能.     

对33例性异常分化患者的细胞遗传学与临床分析

<正>正常的性别分化是一种自胚胎发育期至青春期发育成熟的序贯而连续的分化和发育过程。个体的染色体性别(遗传性别)在受精卵形成时就已确定,即46,XX为女性,46,XY为男性。并且由性染色体的差别决定了性腺的差别,即发育为卵巢及其附属器官着为女性,发育为睾丸及其附属器官者为男性。在染色体基因、性腺和其他一些因素的作用下,个体又向女性表现型或男性表现型性别(躯体性别和社会性别)发育。在胚胎发育的任何时期或任何步骤出现异常,均可引起性别分化异常或性发育疾病。本文对遗传咨询门诊中33例因不育、无精子症、原发闭经和外生殖器发育畸形等原因就诊的患者进行染色体检查及临床分析,探讨了性分化异常患者的遗传学基础。     

Differentiation and development of human female germ cells during prenatal gonadogenesis: an immunohistochemical study

BACKGROUND: In the development of the human ovary, the second trimester includes the transition from oogonial replication to primordial follicle formation. The present study was carried out to assess differentiation and proliferation of germ cells in a series of female gonads from 19 fetuses from the second and third trimester, and two neonates. METHODS: Using immunohistochemistry, the following markers were studied: placental/germ-like cell alkaline phosphatases (PLAP), the marker of pluripotency OCT3/4, the proliferation marker Ki-67, beta-catenin and E-cadherin, the stem cell factor receptor c-KIT, and VASA, a protein specific for the germ cell lineage. RESULTS: PLAP and OCT3/4 were seen during oogenesis, but not in germ cells engaged in folliculogenesis. A similar pattern was observed for Ki-67. Loss of pluripotency occurs once oocytes engage in follicle formation, suggesting a role of cell-cell interactions in the process of germ cell maturation. VASA, c-KIT, beta-catenin and E-cadherin were found in germ cells at all developmental stages of oogenesis and folliculogenesis. CONCLUSIONS: Immunohistochemically, two groups of germ cells can be distinguished. Germ cells that are predominantly found in the cortical region of the ovary before weeks 22-24 of gestation, showing an immature phenotype, are mitotically active, and express OCT3/4, a marker of pluripotency. On the other hand, germ cells undergoing folliculogenesis have lost their pluripotent potential and no longer proliferate.     

Mature oocytes derived from purified mouse fetal germ cells

BACKGROUND: Mouse fetal germ cells have been successfully purified from fetal gonads. However, there are no published reports describing a procedure for deriving mature oocytes from isolated fetal germ cells. The purpose of this present study is to explore whether purified fetal germ cells are able to differentiate into mature oocytes through an in vivo grafting procedure. METHODS AND RESULTS: First, intact 11.5 and 12.5 days post-coitum (dpc) female gonads with or without the attached mesonephros and the reaggregated female gonad cells were transplanted into the recipient mice. The results demonstrate both the gonad accompanied by mesonephroi and the innate gonad structure are not absolutely required for 11.5 dpc and 12.5 dpc oogonia to generate mature oocytes. Next, oogonia were purified from female gonads, aggregated with different ovarian somatic cells and transplanted into the recipient mice. Purified 12.5 dpc oogonia were able to generate mature oocytes by aggregating with 12.5 dpc ovarian somatic cells, but not with 16.5 dpc or 0 days postpartum ovarian somatic cells. We also tested 12.5 dpc male germ cells but they were unable to undergo oogenesis. CONCLUSIONS: Our study demonstrates that mature oocytes can be derived from purified fetal germ cells through an aggregation and transplantation procedure. It also suggests that the synchronized interactions between oogonia and gonadal somatic cells are important to ensure normal folliculogenesis.     

Mouse genetics provides insight into folliculogenesis,fertilization and early embryonic development

After colonization of the gonad, mouse female germ cells enter into the prophase of the first meiotic division as a mid-gestational hallmark of gender. Perinatally, oocytes interact with granulosa cells to form primordial follicles which, with cyclic periodicity, enter into a 3-week growth phase that culminates in meiotic maturation and ovulation. Successful fertilization in the oviduct results in the onset of embryogenesis. Genes expressed in oocytes encode maternal factors that control many of these developmental processes. The establishment of mouse models in which specific genes have been disrupted offers robust insights into molecular mechanisms that control oogenesis, folliculogenesis, fertilization and early embryogenesis. Although relatively few developmental circuits have been characterized in genetic detail, the ongoing revolution in mouse genetics holds great promise. These model systems provide novel information into the molecular basis of the pathways required for oocyte-specific processes as well as for interactions with the temporally changing environment of female germ cells. The similarities between the mouse and human genomes provide assurance that this knowledge will rapidly translate into a better understanding of human reproduction.     

Human BOULE gene rescues meiotic defects in infertile flies

Defects in human germ cell development are common and yet little is known of genes required for germ cell development in men and women. The pathways that develop germ cells appear to be conserved broadly, at least in outline, in organisms as diverse as flies and humans beginning with allocation of cells to the germ cell lineage, migration of these cells to the fetal gonad, mitotic proliferation and meiosis of the germ cells, and maturation into sperm and eggs. In model organisms, a few thousand genes may be required for germ cell development including meiosis. To date, however, no genes that regulate critical steps of reproduction have been shown to be functionally conserved from flies to humans. This may be due in part to strong selective pressures that are thought to drive reproductive genes to high degrees of divergence. Here, we investigated the micro- and macro-evolution of the BOULE gene, a member of the human DAZ (deleted in azoospermia) gene family, within primates, within mammals and within metazoans. We report that sequence divergence of BOULE is unexpectedly low and that rapid evolution is not detectable. We extend the evolutionary analysis of BOULE to the level of phyla and show that a human BOULE transgene can advance meiosis in infertile boule mutant flies. This is the first demonstration that a human reproductive gene can rescue reproductive defects in a fly. These studies lend strong support to the idea that BOULE may encode a key conserved switch that regulates progression of germ cells through meiosis in men.     

Di(2‐ethylhexyl)phthalate: Adverse effects on folliculogenesis that cannot be neglected

Primordial follicle formation and the subsequent transition of follicles through primary and secondary stages constitute crucial events of oogenesis. In particular, in mammals, defects in the processes that precede and accompany the formation of the primordial follicle pool can affect the size of this population significantly, while alterations in follicle activation, growth and maturation can result in premature depletion of the follicle reserve or cause follicle arrest at immature stages. Over the last decade, in vitro and in vivo approaches have been used to provide evidence that exposure to di(2‐ethylhexyl)phthalate(DEHP), the most widely used plasticizer, has a deleterious effect on various stages of folliculogenesis in rodents. There is growing concern, supported by epidemiological and experimental data, that DEHP may have similar effects in women. This article reviews the evidence, with particular reference to our own findings, that DEHP may actually exert a variety of adverse effects on mammalian folliculogenesis from early to final stages of oogenesis, including altered development of the primordial germ cells, impaired fetal oocyte survival and meiotic progression, reduced oocyte nest breakdown, acceleration of primordial follicle activation, altered follicle steroidogenesis and increased follicle atresia. These effects can cause serious complications for reproductive and nonreproductive women's health. In addition, emerging data indicate that phthalates, including DEHP, may cause subtle epigenetic changes in germ cells that can be transmitted to subsequent generations, with potential negative effects on human health. Environ. Mol. Mutagen. 57:589–604, 2016. © 2016 Wiley Periodicals, Inc.     

Recent advances in the derivation of germ cells from the embryonic stem cells

In recent years, considerable progress has been made in the establishment and differentiation of human embryonic stem (ES) cell lines. The primordial germ cells (PGCs) and embryonic germ (EG) cells derived from them share many of their properties with ES cells. ES cell lines have now been derived from different stages of germ cell development and they have differentiated into gametes and shown embryonic development in mice, including the production of live pups. Conversely, germ cells can also be derived from ES cells. It has been demonstrated that murine (m) ES cells can differentiate into PGCs and subsequently into early gametes (oocytes and sperms) and blastocysts. Recently, immature sperm cells derived from mES cells in culture have produced live offspring. Preliminary research has indicated that human (h) ES cells probably have the potential to differentiate into germ cells. Adult stem cells have been reported to differentiate into mature germ cells in vitro. Therefore, stem cells may offer a valuable in vitro model for the investigation of germ cell development and the early stages of human gametogenesis, including epigenetic modifications of the germ line. This review discusses recent developments in the derivation and specification of mammalian germ cells from ES cells and describes some of the mechanisms of germ cell development.     

Mammalian sex chromosomes III. Activity of pseudoautosomal steroid sulfatase enzyme during spermatogenesis inMus musculus

Parallel to the inactivation of the X chromosome in somatic cells of female, the male X in mammals is rendered inactive during spermatogenesis. Pseudoautosomal genes, those present on the X-Y meiotically pairable region of male, escape inactivation in female soma. It is suggested, but not demonstrated, that they may also be refractory to the inactivation signal in male germ cells. We have assayed activity of the enzyme steroid sulfatase, product of a pseudoautosomal gene, in testicular cells of the mouse and shown its presence in premeiotic, meiotic (pachytene), and postmeiotic (spermatid) cell types. It appears that, as in females, pseudoautosomal genes may escape inactivation in male germ cells also.     

Morphological Aspects of Gonadal Morphogenesis in Bufo bufo (Amphibia anura): Bidder's Organ Differentiation

We have described the architecture of Bidder's organ, defined its compartmented structure, and affirmed the presence of basal laminae. We did not find morphological differences between sexes in Bidder's organ. All specimens initially developed gonads with a peripheral fertile layer surrounding a thin primary cavity. The first oogenetic wave was observed early, showing all phases of meiosis, including leptotene, zygotene, and pachytene, which had been previously thought to be lacking. The peculiar presence of an asynchronous germ cell nest was discussed. Diplotene oocytes issued from the peripheral layer and migrated inside the primary cavity. They were surrounded by a single layer of follicular cells, which originated from the peripheral layer somatic cells and were delimited by a basal lamina. There were few medulla or central layer cells. At the end of metamorphosis, while the oocytes of the first oogenetic wave came into close contact with blood vessels, a second oogenetic wave took place just as the first, except for the presence of synchronous germ cell nests. The central layer was not visible and we did not observe the formation of an ovarian pocket. Stocks of stem germ cells remained in the peripheral layer during both the first and second oogenetic waves. The asymmetric model, in which there is a tendency toward a primary female differentiation, was confirmed. The female differentiation becomes stable in the Bidder's organ because of the absence of further interaction between germ and medullary somatic cells, which would have led toward a male differentiation. Anat Rec, 2007. © 2007 Wiley‐Liss, Inc.