Arrest of WNT/Β-Catenin Signaling Enables the Transition from Pluripotent to Differentiated Germ Cells in Mouse Ovaries
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Sex Determination in Mammalian Germ Cells: Extrinsic Versus Intrinsic Factors
REPRODUCTIONREVIEW Sex determination in mammalian germ cells: extrinsic versus intrinsic factors Josephine Bowles and Peter Koopman Division of Molecular Genetics and Development, and ARC Centre of Excellence in Biotechnology and Development, Institute for Molecular Bioscience, The University of Queensland, Brisbane, Queensland 4072, Australia Correspondence should be addressed to J Bowles; Email: [email protected] Abstract Mammalian germ cells do not determine their sexual fate based on their XX or XY chromosomal constitution. Instead, sexual fate is dependent on the gonadal environment in which they develop. In a fetal testis, germ cells commit to the spermatogenic programme of development during fetal life, although they do not enter meiosis until puberty. In a fetal ovary, germ cells commit to oogenesis by entering prophase of meiosis I. Although it was believed previously that germ cells are pre-programmed to enter meiosis unless they are actively prevented from doing so, recent results indicate that meiosis is triggered by a signaling molecule, retinoic acid (RA). Meiosis is avoided in the fetal testis because a male-specifically expressed enzyme actively degrades RA during the critical time period. Additional extrinsic factors are likely to influence sexual fate of the germ cells, and in particular, we postulate that an additional male-specific fate-determining factor or factors is involved. The full complement of intrinsic factors that underlie the competence of gonadal germ cells to respond to RA and other extrinsic factors is yet to be defined. Reproduction (2010) 139 943–958 Introduction A commitment to oogenesis involves pre-meiotic DNA replication and entry into and progression through Germ cells are the special cells of the embryo that prophase of the first meiotic division during fetal life. -
Gametogenesis: Spermatogenesis & Oogenesis -Structure of Sperm and Egg Fertilization
Gametogenesis: Spermatogenesis & Oogenesis ‐Structure of Sperm and Egg Fertilization ‐ Definition, Mechanism Early development in Frog ‐ Cleavage, Blas tu la, GtlGastrula, DitiDerivatives of Germ layers Vikasana - CET 2012 y Human reproduction y Brief Account of Fertilization: Implantation, Placenta, Role of Gonadotropins and sex hormones , Menstrual cycle. y Fertility Control: Family Planning Methods- y Infertility Control: Meaning, Causes,Treatment y STD: AIDS , Syphilis and Gonorrhea Vikasana - CET 2012 1.Primary Oocyte is a) Haploid (n) b) Diploid (2n) c) Polyploid d) None of the above Vikasana - CET 2012 2.Secondary Oocyte is a) Haploid (n) b) Diploid (2n) c) Polyploid d) None of the above Vikasana - CET 2012 3.Centrioles of sperm control a) Movement of tail b) Hap lo id numb er of ch romosomes c) Help in fertilization d) None of the above. Vikasana - CET 2012 4.The Fertilization membrane is secreted because a) It checks the entry of more sperms after fertilization b) it checks the entry of antigens in ovum c))p it represents the left out tail of the sperm d) it represen tVikasanas the p - l CETasma 2012 mem brane of the sperm 5.Meiosis I occurs in a) Primary spermatocytes b) Secondary spermatocytes c) Both a and b d) Spermatogonia Vikasana - CET 2012 6.Meiosis II occurs in a) Secondary oocyte b))y Primary oocyte c) Spermatogonia d) Oogonia Vikasana - CET 2012 7.Axial filament of sperm is formed by a) Distal centriole b) Prox ima l centitrio le c) Mitochondria d) DNA Vikasana - CET 2012 8.Polar bodies are formed during a) oogenesis -
Focus on Stem Cells Germ Cells from Mouse and Human Embryonic Stem Cells
REPRODUCTIONREVIEW Focus on Stem Cells Germ cells from mouse and human embryonic stem cells Behrouz Aflatoonian and Harry Moore Centre for Stem Cell Biology, University of Sheffield, Sheffield S10 2UH, UK Correspondence should be addressed to H Moore; Email: [email protected] Abstract Mammalian gametes are derived from a founder population of primordial germ cells (PGCs) that are determined early in embryogenesis and set aside for unique development. Understanding the mechanisms of PGC determination and differentiation is important for elucidating causes of infertility and how endocrine disrupting chemicals may potentially increase susceptibility to congenital reproductive abnormalities and conditions such as testicular cancer in adulthood (testicular dysgenesis syndrome). Primordial germ cells are closely related to embryonic stem cells (ESCs) and embryonic germ (EG) cells and comparisons between these cell types are providing new information about pluripotency and epigenetic processes. Murine ESCs can differentiate to PGCs, gametes and even blastocysts – recently live mouse pups were born from sperm generated from mESCs. Although investigations are still preliminary, human embryonic stem cells (hESCs) apparently display a similar developmental capacity to generate PGCs and immature gametes. Exactly how such gamete-like cells are generated during stem cell culture remains unclear especially as in vitro conditions are ill-defined. The findings are discussed in relation to the mechanisms of human PGC and gamete development and the biotechnology of hESCs and hEG cells. Reproduction (2006) 132 699–707 Introduction indicate that human embryonic stem cells (hESCs) most likely display a similar developmental capacity (Clark Detailed investigations of the earliest stages of germ cell et al. -
Insights from Male Germ Cell Differentiation
Cell Death & Differentiation (2021) 28:2296–2299 https://doi.org/10.1038/s41418-021-00812-0 COMMENT Natural selection at the cellular level: insights from male germ cell differentiation 1 1 Daniel H. Nguyen ● Diana J. Laird Received: 9 February 2021 / Revised: 20 May 2021 / Accepted: 20 May 2021 / Published online: 2 June 2021 © The Author(s) 2021. This article is published with open access Waddington’s concept of differentiation as an epigenetic The germline is a fascinating context for investigating landscape provides an enduring metaphor visualizing the the consequences of heterogeneity on differentiation and options faced by stem and progenitor cells. However, cell fate. As fetal germ cells establish the gametes, their increasing understanding of cellular heterogeneity poses population dynamics can greatly influence inheritance. The new questions about the identities and behaviors of the cells conflict between diversity and orderly differentiation looms beginning this process. We now recognize a greater diver- centrally over germline development. In mouse embryos, sity of initial states for individual progenitor cells, which germ cells undertake an epic journey, from specification may affect their trajectories and disrupt progress entirely. through sex differentiation, replete with opportunities for 1234567890();,: 1234567890();,: Here, we consider how developmental selection occurs heterogeneity to develop and be assessed. Notably, an when heterogeneity in differentiating progenitors produces excess of germ cells is produced and then pruned by pro- divergent cellular outcomes of survival versus elimination. grammed cell death [5]. This occurs across diverse species Heterogeneity is a fundamental property of biological regardless of sex, suggesting that differential fitness and systems. Individual cell properties like location or cell cycle elimination are critical. -
Development of Sexual Dimorphism in the Drosophila Testis
review REVIEW Spermatogenesis 2:3, 129-136; July/August/September 2012; © 2012 Landes Bioscience Development of sexual dimorphism in the Drosophila testis Cale Whitworth, Erin Jimenez and Mark Van Doren* Department of Biology; The Johns Hopkins University; Baltimore, MD USA Keywords: Drosophila, gonad, germ cell, sexual dimorphism, testis, doublesex, DMRT, germline stem cell, stem cell niche The creation of sexual dimorphism in the gonads is essential for posterior (A/P) and dorsal/ventral (D/V) patterning systems that producing the male and female gametes required for sexual divide the mesoderm into distinct cell types (reviewed in ref. 1). reproduction. Sexual development of the gonads involves Three clusters of ≈12 SGPs each will form on either side of the both somatic cells and germ cells, which often undergo sex embryo in parasegments (PSs) 10–12 (ref. 2, Figure 1) (“paraseg- determination by different mechanisms. While many sex- specific characteristics evolve rapidly and are very different ments” are the units of segmental identity along the A/P axis). between animal species, gonad function and the formation Each mesodermal PS is divided into an anterior (“even skipped of sperm and eggs appear more similar and may be more (eve) domain”) and posterior (“sloppy paired domain”). SGPs conserved. Consistent with this, the doublesex/mab3 Related form within the eve domain while in other PSs this domain gives Transcription factors (DMRTs) are important for gonad sexual rise to the fat body.3,4 The D/V axis is also divided into distinct dimorphism in a wide range of animals, including flies, worms domains, and the SGPs in PS10–12 form within the dorso-lateral and mammals. -
Module 10: Meiosis and Gametogenesis
PEER-LED TEAM LEARNING INTRODUCTORY BIOLOGY MODULE 10: MEIOSIS AND GAMETOGENESIS JOSEPH G. GRISWOLD, PH.D. City College of New York, CUNY (retired) I. Introduction Most cells in our bodies have nuclei with 46 chromosomes organized in 23 homologous pairs. Because there are two chromosomes of each type, the cells are called diploid and 2N = 46. If mothers and fathers each passed 46 chromosomes to their offspring in reproducing, the children in the new generation would have 92 chromosomes apiece. In the following generation it would be 184. Obviously, the increase does not occur; normal people in each generation have the same 2N = 46. To produce a new individual (a zygote, initially) with 46 chromosomes, an egg and sperm each contribute half the total, or 23, when fertilization occurs. Both sperm and eggs, called gametes, develop from body cells in which the full 46 chromosomes are present. These body cells, located in the testes and ovaries, undergo special cell divisions, which reduce the number of chromosomes in half. The special cell divisions, two for each cell, make up a process called meiosis. Cells that have completed meiosis then differentiate to become gametes. The general objective of this laboratory is to learn how meiosis occurs in forming eggs and sperm to carry genetic information from one generation to the next. B. Benchmarks. 1. Demonstrate an understanding of the terminology of cellular genetic structure using diagrams. 2. Demonstrate the process of meiosis by using models or drawing chromosomes on cell outlines. 3. Compare the processes of mitosis and meiosis by: a. drawing diagrams with explanations of the processes, and b. -
Germ-Line Immortality
COMMENTARY Germ-line immortality Martin M. Matzuk* Departments of Pathology, Molecular and Cellular Biology, and Molecular and Human Genetics, and Program in Developmental Biology, Baylor College of Medicine, Houston, TX 77030 ajor advances in stem cell Table 1. Pathway of differentiation in males research have occurred over Spermatogonial Differentiated the last decades. Progress Markers ES cells ¡ PGCs ¡ Gonocytes ¡ stem cells ¡ spermatogonia has included the generation Mof lines of human and mouse embryonic Kit ϩϩϩ͞– – (low) ϩ ϩ ϩϩ stem (ES) cells and the identification and Thy-1 ? (low) – Oct4 ϩϩ ϩ ϩ – purification of stem cells for multiple Plzf ϩ (low)* ϩ* ϩϩ – independent lineages. Recent studies by GCNA1 – ϩ† ϩϩ ϩ Brinster and colleagues in this issue of TNAP ϩ (high) ϩ (high) – ϩ (low)͞–– PNAS (1) also suggest that the reproduc- RET ϩ (low)* ? ? ϩ – ␣ ϩ ϩ tive potential of an organism can be pro- GFR 1 (low)* ? ? (low) – NCAM ϩ ? ϩϩ ? longed indefinitely by using germ-line stem cells. It even appears that eggs and Markers that are known to be expressed (ϩ) or absent (–) in many of the pathway cells are listed. GCNA1, sperm can develop from cultured mouse germ cell nuclear antigen 1; TNAP, tissue-nonspecific alkaline phosphatase; NCAM, neural cell adhesion ES cells (2–4). Although gametes derived molecule. in vitro have yet to prove their develop- *mRNA levels. † mental potential, these studies suggest Postmigratory PGCs only. that ES cells and germ-line stem cells share many characteristics. ent males. The process was surprisingly KitϪ Sca-IϪ ␣6-integrinϩ ␣v-integrinϪ/dim In most mammalian females, meiosis efficient, with up to 100% of the injected (9, 10). -
Female and Male Gametogenesis 3 Nina Desai , Jennifer Ludgin , Rakesh Sharma , Raj Kumar Anirudh , and Ashok Agarwal
Female and Male Gametogenesis 3 Nina Desai , Jennifer Ludgin , Rakesh Sharma , Raj Kumar Anirudh , and Ashok Agarwal intimately part of the endocrine responsibility of the ovary. Introduction If there are no gametes, then hormone production is drastically curtailed. Depletion of oocytes implies depletion of the major Oogenesis is an area that has long been of interest in medicine, hormones of the ovary. In the male this is not the case. as well as biology, economics, sociology, and public policy. Androgen production will proceed normally without a single Almost four centuries ago, the English physician William spermatozoa in the testes. Harvey (1578–1657) wrote ex ovo omnia —“all that is alive This chapter presents basic aspects of human ovarian comes from the egg.” follicle growth, oogenesis, and some of the regulatory mech- During a women’s reproductive life span only 300–400 of anisms involved [ 1 ] , as well as some of the basic structural the nearly 1–2 million oocytes present in her ovaries at birth morphology of the testes and the process of development to are ovulated. The process of oogenesis begins with migra- obtain mature spermatozoa. tory primordial germ cells (PGCs). It results in the produc- tion of meiotically competent oocytes containing the correct genetic material, proteins, mRNA transcripts, and organ- Structure of the Ovary elles that are necessary to create a viable embryo. This is a tightly controlled process involving not only ovarian para- The ovary, which contains the germ cells, is the main repro- crine factors but also signaling from gonadotropins secreted ductive organ in the female. -
Grade 12 Life Science Human Reproduction Notes
KNOWLEDGE AREA: Life Processes in Plants and Animals TOPIC 2.1: Reproduction in Vertebrates Human Reproduction Introduction Structure of Male Reproductive System Structure of Female Reproductive System Main Changes that occur during Puberty Gametogenesis Menstrual Cycle Fertilization and Embryonic Development Implantation and Development Gestation Role of Placenta There are 2 types of reproduction. These are… 1. Sexual and 2. Asexual reproduction We are studying reproduction in humans. Therefore we need to know what is sexual reproduction. Sexual reproduction is reproduction that occurs with the use of gametes. In humans fertilization occurs during sexual reproduction. This means a haploid sperm fuses with a haploid egg to form a diploid zygote. The zygote has 46 chromosomes or 23 pairs of chromosomes therefore it is called diploid. So how many chromosomes does the egg and sperm have? The sperm has 23 chromosomes The egg has 23 chromosomes The zygote then divides by mitosis to produce a large number of identical cells. All the cells have the same number of chromosomes and identical DNA. Some of these cells become differentiated. This means that the cells undergo physical and chemical changes to perform specialized function. Therefore these cells are adapted for their functions. This is how the body parts are formed. Therefore the zygote eventually develops into a fully formed adult. Sexual maturity occur between 11-15. It is known as puberty. During puberty meiosis occurs in the male and female reproductive organs to produce the gametes. Since the gametes are produced by meiosis, each gamete will have a haploid number of chromosomes and each egg or sperm will be genetically different from the other. -
The Effects of Dexamethasone on the Differentiation and the Fertilisation of the Germinal Primordium in the Chick Embryo Danièle Cuminge, Julian Smith, Régis Dubois
The effects of dexamethasone on the differentiation and the fertilisation of the germinal primordium in the chick embryo Danièle Cuminge, Julian Smith, Régis Dubois To cite this version: Danièle Cuminge, Julian Smith, Régis Dubois. The effects of dexamethasone on the differentiation and the fertilisation of the germinal primordium in the chick embryo. Reproduction Nutrition Devel- opment, EDP Sciences, 2000, 40 (2), pp.127-148. 10.1051/rnd:2000125. hal-00900392 HAL Id: hal-00900392 https://hal.archives-ouvertes.fr/hal-00900392 Submitted on 1 Jan 2000 HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. The documents may come from émanant des établissements d’enseignement et de teaching and research institutions in France or recherche français ou étrangers, des laboratoires abroad, or from public or private research centers. publics ou privés. Reprod. Nutr. Dev. 40 (2000) 127–148 127 © INRA, EDP Sciences Original article The effects of dexamethasone on the differentiation and the fertilisation of the germinal primordium in the chick embryo Danièle CUMINGEa, Julian SMITHb, Régis DUBOISa* a Institut d’Embryologie Cellulaire et Moléculaire, 49 bis avenue de la Belle Gabrielle, Collège de France et CNRS, 94736 Nogent-sur-Marne Cedex, France b Centre de Biologie du Développement, Université Paul Sabatier, 31062 Toulouse, France (Received 15 December 1999; accepted 24 February 2000) Abstract — We showed that, in the chick embryo, the fertilisation of the attractive germinal epithe- lium by primary germ cells can be represented by a three-dimensional diagram in which the space and time co-ordinates are graduated in terms of the segmentation of the axial and paraxial mesoderm. -
Sexual Reproduction: Meiosis, Germ Cells, and Fertilization 21
Chapter 21 Sexual Reproduction: Meiosis, Germ Cells, and Fertilization 21 Sex is not absolutely necessary. Single-celled organisms can reproduce by sim- In This Chapter ple mitotic division, and many plants propagate vegetatively by forming multi- cellular offshoots that later detach from the parent. Likewise, in the animal king- OVERVIEW OF SEXUAL 1269 dom, a solitary multicellular Hydra can produce offspring by budding (Figure REPRODUCTION 21–1), and sea anemones and marine worms can split into two half-organisms, each of which then regenerates its missing half. There are even some lizard MEIOSIS 1272 species that consist only of females that reproduce without mating. Although such asexual reproduction is simple and direct, it gives rise to offspring that are PRIMORDIAL GERM 1282 genetically identical to their parent. Sexual reproduction, by contrast, mixes the CELLS AND SEX DETERMINATION IN genomes from two individuals to produce offspring that differ genetically from MAMMALS one another and from both parents. This mode of reproduction apparently has great advantages, as the vast majority of plants and animals have adopted it. EGGS 1287 Even many procaryotes and eucaryotes that normally reproduce asexually engage in occasional bouts of genetic exchange, thereby producing offspring SPERM 1292 with new combinations of genes. This chapter describes the cellular machinery of sexual reproduction. Before discussing in detail how the machinery works, FERTILIZATION 1297 however, we will briefly consider what sexual reproduction involves and what its benefits might be. OVERVIEW OF SEXUAL REPRODUCTION Sexual reproduction occurs in diploid organisms, in which each cell contains two sets of chromosomes, one inherited from each parent. -
REVIEW Hormonal Regulation of Male Germ Cell Development
117 REVIEW Hormonal regulation of male germ cell development Saleela M Ruwanpura, Robert I McLachlan and Sarah J Meachem Prince Henry’s Institute of Medical Research, Clayton, Victoria 3168, Australia (Correspondence should be addressed to S J Meachem; Email: [email protected]) Abstract Over the past five decades, intense research using various been established that testosterone is essential for spermato- animal models, innovative technologies notably genetically genesis, and also FSH plays a valuable role. Therefore modified mice and wider use of stereological methods, unique understanding the basic mechanisms by which hormones agents to modulate hormones, genomic and proteomic govern germ cell progression are important steps towards techniques, have identified the cellular sites of spermato- improved understating of fertility regulation in health diseases. genesis, that are regulated by FSH and testosterone. It has Journal of Endocrinology (2010) 205, 117–131 Introduction (termed spermiation) requires both testosterone and FSH (reviewed in McLachlan et al. (2002a)). In humans, sperma- The past decade has been a critical period in our discoveries of togonial development, meiosis, and spermiation are the how the complex process of spermatogenic cell development three main processes that are regulated by gonadotrophins is regulated. These discoveries have been aided through the (McLachlan et al. 2002b, Matthiesson et al. 2005, 2006). use of innovative technologies, most notably genetically A stable germ cell population is determined by the modified mice, the wider use of best practice stereological balance of death (apoptosis) and division, which are influenced methods that allow the rigorous mapping of cell populations, by many biochemical factors. The highly coordinated nature unique agents to modulate hormones, and the genomic and of spermatogenesis requires intimate functional and junctional proteomic revolution.