Lecture 9: Reproduction - male embryonic and postnatal
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Questions and Answers

What are the two primary fates of spermatogonia cells?

  • Self-renewal or sperm maturation
  • Self-renewal or spermatogenesis (correct)
  • Mitosis or meiosis
  • Cell death or differentiation

    • What technique was primarily used to demonstrate the repopulation of testes by SSCs?

  • Flow cytometry analysis
  • LacZ+ gene labeling (correct)
  • CRISPR gene editing
  • Gene knockout therapy

    • Which of the following results confirmed that LacZ+ SSCs contributed to normal spermatogenesis in recipient mice?

  • Presence of spermatogonia in the seminiferous tubules
  • Increased testis size and weight
  • Clear staining for β-galactosidase in the testes (correct)
  • Complete absence of germ cells in recipients

    • What does the detection of β-galactosidase activity indicate in this study?

    <p>Successful repopulation of the testis by SSCs</p> Signup and view all the answers

    What was the condition of the recipient mice's testis before the injection of LacZ+ SSCs?

    <p>Depleted of their own germ cells</p> Signup and view all the answers

    What is the primary process that occurs in spermatogonial stem cells during the embryonic stage?

    <p>Self-renewal</p> Signup and view all the answers

    At which stage does spermatogenic activity first begin to activate?

    <p>Puberty</p> Signup and view all the answers

    During adulthood, how is spermatogenesis characterized?

    <p>It is a continuous process with daily sperm production.</p> Signup and view all the answers

    What happens to one daughter cell during the mitotic division of spermatogonial stem cells at puberty?

    <p>It maintains the stem cell population.</p> Signup and view all the answers

    What is the main outcome of sperm maturation in the epididymis?

    <p>Development of motility and fertilization capability.</p> Signup and view all the answers

    What occurs during childhood regarding the spermatogonial population?

    <p>Spermatogonia proliferate without active spermatogenesis.</p> Signup and view all the answers

    Which phase of sperm development follows the completion of meiosis?

    <p>Spermiogenesis</p> Signup and view all the answers

    What is the key feature of spermatogenic activity during the childhood stage?

    <p>Presence of spermatogonia without spermatogenesis.</p> Signup and view all the answers

    What is the fate of the spermatogonia during the embryonic stage before puberty?

    <p>They solely undergo self-renewal.</p> Signup and view all the answers

    What is the primary distinction between germline stem cells and multipotent stem cells?

    <p>Germline stem cells are unipotent and only produce germ cells, whereas multipotent stem cells can differentiate into various cell types.</p> Signup and view all the answers

    What characterizes a terminally differentiated germ cell?

    <p>It has irreversibly lost its ability to proliferate and has reached its final stage of development.</p> Signup and view all the answers

    Why is the genomic quality of differentiated germ cells significant?

    <p>It carries the DNA that may lead to potential genetic disorders in the offspring.</p> Signup and view all the answers

    What type of stem cells from the hematopoietic system are considered multipotent?

    <p>Stem cells that can give rise to a range of blood cells, including red and white blood cells.</p> Signup and view all the answers

    What happens to germline stem cells after they differentiate into mature germ cells?

    <p>They become terminally differentiated and cannot proliferate.</p> Signup and view all the answers

    Which statement correctly describes the function of unipotent germline stem cells?

    <p>They produce either sperm or oocytes but not both.</p> Signup and view all the answers

    What does the term 'totipotent zygote' refer to in the context of germ cell development?

    <p>A fertilized egg that has the potential to develop into any cell type.</p> Signup and view all the answers

    What is the significance of somatic genes being down-regulated in germ cells?

    <p>It helps maintain the distinct identity of germ cells.</p> Signup and view all the answers

    What role does global DNA methylation changes play during embryonic development?

    <p>It erases epigenetic imprints for cell reprogramming.</p> Signup and view all the answers

    How do male and female epigenetic patterns differ in germ cells?

    <p>Male germ cells are prepared for spermatogenesis, while female are for oogenesis.</p> Signup and view all the answers

    At what stage do female germ cells pause during meiosis?

    <p>Prophase I</p> Signup and view all the answers

    When do male germ cells begin their meiotic process?

    <p>At puberty</p> Signup and view all the answers

    What is the main difference in reproduction between male and female germ cells following puberty?

    <p>Males produce sperm throughout life, while females arrest oocytes until fertilization.</p> Signup and view all the answers

    What is an essential factor for establishing the correct epigenetic environment in germ cells?

    <p>Proper epigenetic reprogramming.</p> Signup and view all the answers

    How do extended meiosis stages affect female germ cells?

    <p>They remain arrested at various meiosis stages until fertilized.</p> Signup and view all the answers

    What maintains the distinct identity of germ cells during development?

    <p>Down-regulation of somatic cell functions.</p> Signup and view all the answers

    How do primordial germ cells (PGCs) initially differ in their development?

    <p>They start as a bipotential cell type with the potential to become either sperm or eggs.</p> Signup and view all the answers

    What markers do primordial germ cells express during their early development?

    <p>Oct4, Nagog, and Sox2</p> Signup and view all the answers

    What occurs to primordial germ cells when they migrate to the gonadal ridge in the male?

    <p>They enter a mitotic arrest before further differentiation.</p> Signup and view all the answers

    How does the activation of the SRY gene affect primordial germ cells?

    <p>It promotes the differentiation of PGCs into male germ cells.</p> Signup and view all the answers

    Which process occurs in female gonads after primordial germ cells enter meiosis?

    <p>They arrest at prophase I until fertilization.</p> Signup and view all the answers

    What is the role of SOX9 in male gonad development?

    <p>It promotes FGF9 expression necessary for differentiation.</p> Signup and view all the answers

    At which stage do male primordial germ cells start spermatogenesis?

    <p>At puberty.</p> Signup and view all the answers

    What is the function of FGF9 in the development of male germ cells?

    <p>It promotes the proliferation and differentiation of male germ cells.</p> Signup and view all the answers

    What sequence of events characterizes the male embryonic development of primordial germ cells?

    <p>SRY gene activation, differentiation into male germ cells, formation of seminiferous cords.</p> Signup and view all the answers

    Study Notes

    Germline Stem Cells (GSCs)

    • Produce gametes (sperm or oocytes)
    • Unipotent: Can only produce one type of cell (sperm or oocytes).
    • Unlike multipotent stem cells which can differentiate into multiple cell types.

    Germ Cell Specification

    • Two types:
      • Determinative: Inherited factors (insects, worms, frogs, fish)
      • Regulative: Induced by signalling factors (mammals)
      • Germ plasm unevenly distributed during early embryonic development in determinative specification; molecular signals like Nanos mark cells destined to become germ cells

    Mammalian Germline Induction

    • BMP (bone morphogenetic protein) from extraembryonic ectoderm, especially BMP4 and BMP8B, initiate changes that lead to germ cell formation.
    • BMP antagonists restrict BMP signaling to proximal epiblast to ensure placement.

    Germ Cell Development

    • Germ cells originate from the early embryo.
    • Cells migrate to the genital ridges (ovaries or testes.)
    • They undergo meiosis at puberty, leading to sperm or oocytes

    Activation of Pluripotency

    • Crucial factors: Oct4, Sox2, Nanog, and Nanos3 maintain pluripotency, allowing cells to differentiate into a variety of cells.

    Germ Cell Genes

    • Oct4: Maintains pluripotency
    • Sox2: Part of pluripotency network
    • Nanog: Maintains germline's undifferentiated state
    • Nanos3: Part of pluripotency network involved in germline development

    Mammalian Germ Cells

    • Not pre-determined by cytoplasmic determinants, but induced by signals from extra-embryonic tissues.

    Germ Cell Differentiation

    • Markers: Blimp1, Prdm14, Sox2, Stella and Nanos3.
    • Transcription factors to maintain germline identity and establish the epigenetic landscape.

    Epigenetic Reprogramming

    • Crucial for resetting epigenetic imprints for germ cells prior to fertilization.
    • Global demethylation (reduction of 5-methylcytosine) prepares germ cells.
    • Epigenetically programmed differently depending on sex (male or female).

    Spermatogenesis

    • Male gamete production.
    • Stages: Spermatogonia, primary spermatocytes, secondary spermatocytes, spermatids and spermatozoa.
    • Spermatogonial stem cell (SSCs): Continuous sperm production throughout adult life.

    Spermatogonial Stem Cells (SSC)

    • Primitive spermatogonia.
    • Responsible for continuous sperm production.
    • Located at the periphery of the seminiferous tubules, undergo self-renewal and differentiation.

    Postnatal Development

    • Increase in Retinoic Acid levels in males during puberty to initiate the initial stage of meiosis.
    • Peak STRA8 expression in males shortly after birth marking the transition to meiosis.

    Aging and SSC

    • The niche supporting SSC decline with aging, leading to a loss of germ cells.
    • Lower GDNF levels in aging males contributing to the decline in SSC function,
    • Reduced GDNF leads to impaired spermatogenesis.

    Spermatogonial Stem Cell Niche

    • Crucial for SSC maintenance: Sertoli cells, FGF2, CSF1, and CXCL12 play a vital role.
    • Extrinsic factors supporting SSC survival.

    Markers and Selection of SSC

    • LacZ+ staining identifies and confirms SSC repopulation and spermatogenesis.

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    Description

    Explore the two primary fates of spermatogonia cells in this informative quiz. Understand the processes of differentiation and proliferation in male gametogenesis. Test your knowledge and learn more about the fascinating world of cellular development.

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