bims-cebooc Biomed News
on Cell biology of oocytes
Issue of 2024‒08‒18
nineteen papers selected by
Gabriele Zaffagnini, Centre for Genomic Regulation
  1. The idiosyncrasies of oocytes.
  2. Reconstruction of artificial nuclei with nuclear import activity in living mouse oocytes.
  3. Decreased glutathione synthesis in granulosa cells, but not oocytes, of growing follicles decreases fertility in mice.
  4. Histories and mysteries underlying meiotic maturation failure in human oocytes.
  5. Analysis of Meiotic Progression by Ex Vivo Culture of Mouse Embryonic Ovaries.
  6. 3D culture of ovarian follicles in granular and nanofibrillar hydrogels.
  7. Rapid Isolation of Stage I Oocytes in Zebrafish Devoid of Granulosa Cells.
  8. Molecular regulation of DNA damage and repair in female infertility: a systematic review.
  9. DNA methylation in mammalian development and disease.
  10. Embryonic aneuploidy - the true "last barrier in assisted reproductive technology"?
  11. Ice formation and its elimination in cryopreservation of oocytes.
  12. Temporal Analysis of DSB Repair Outcome in Caenorhabditis elegans Meiosis.
  13. The synaptonemal complex assembles between meiotic chromosomes by wetting.
  14. Culture of the Intact Postnatal Naked Mole-Rat Ovary: From Meiotic Prophase to Single-Cell RNASeq.
  15. Nuclear Argonaute protein NRDE-3 switches small RNA binding partners during embryogenesis coincident with the formation of SIMR granules.
  16. Polo-like kinase 1 prevents excess microtubule polymerization in C. elegans oocytes to ensure faithful meiosis.
  17. Automated Quantification of Meiotic Recombination Foci Position and Intensity.
  18. Generation of Meiotic Mouse Models Using CRISPR/Cas9 Technology.
  19. Cellular sex throughout the organism underlies somatic sexual differentiation.
  1. Trends Cell Biol. 2024 Aug 13. pii: S0962-8924(24)00144-2. [Epub ahead of print]
    The idiosyncrasies of oocytes.
    Jun Wei Pek.
      Animal oocytes face extreme challenges. They remain dormant in the body for long periods of time. To support offspring development and health, they need to store genetic material and maternal factors stably and at the same time manage cellular damage in a reliable manner. Recent studies have provided new insights on how oocytes cope with such challenges. This review discusses the many unusual or idiosyncratic nature of oocytes and how understanding oocyte biology can help us address issues of reproduction and intergenerational inheritance.
    Keywords:  dormancy; germline; mitochondria; primordial follicle; quiescence; reproduction
    DOI:  https://doi.org/10.1016/j.tcb.2024.07.006
  2. Genes Cells. 2024 Aug 14.
    Reconstruction of artificial nuclei with nuclear import activity in living mouse oocytes.
    Nao Yonezawa, Tomoko Shindo, Haruka Oda, Hiroshi Kimura, Yasushi Hiraoka, Tokuko Haraguchi, Kazuo Yamagata.
      In eukaryotes, DNA is housed within the cell nucleus. Molecules required for the formation of a nucleus have been identified using in vitro systems with frog egg extracts and in vivo imaging of somatic cells. However, little is known about the physicochemical factors and conditions required for nuclear formation in mouse oocytes. In this study, using a reconstitution approach with purified DNA, we aimed to determine factors, such as the amount and timing of DNA introduction, required for the formation of nuclei with nuclear transport activity in mouse oocytes. T4 phage DNA (~166 kbp) was microinjected into strontium-activated oocytes to evaluate the conditions appropriate for nuclear formation. Microinjection of 100-500 ng/μL of T4 DNA, but not 20 ng/μL, was sufficient for the formation of nucleus-like structures. Furthermore, microinjection of DNA during metaphase II to telophase II, but not during interphase, was sufficient. Electron and fluorescence microscopy showed that T4 DNA-induced nucleus-like structures had nuclear lamina and nuclear pore complex structures similar to those of natural nuclei, as well as nuclear import activity. These results suggest that exogenous DNA can form artificial nuclei with nuclear transport functions in mouse oocytes, regardless of the sequence or source of the DNA.
    Keywords:  artificial nucleus; long‐strand DNA; mouse oocyte; nuclear import activity; pronucleus
    DOI:  https://doi.org/10.1111/gtc.13149
  3. Biol Reprod. 2024 Aug 16. pii: ioae124. [Epub ahead of print]
    Decreased glutathione synthesis in granulosa cells, but not oocytes, of growing follicles decreases fertility in mice.
    Rachel Cinco, Kelli Malott, Jinhwan Lim, Laura Ortiz, Christine Pham, Angelica Rosario, Jennifer Welch, Ulrike Luderer.
      Prior studies showed that mice deficient in the modifier subunit of glutamate cysteine ligase (Gclm), the rate-limiting enzyme in synthesis of the thiol antioxidant glutathione (GSH), have decreased ovarian GSH concentrations, chronic ovarian oxidative stress, poor oocyte quality resulting in early preimplantation embryonic mortality and decreased litter size, and accelerated age-related decline in ovarian follicle numbers. Global deficiency of the catalytic subunit of this enzyme, Gclc, is embryonic lethal. We tested the hypothesis that granulosa cell- or oocyte-specific deletion of Gclc recapitulates the female reproductive phenotype of global Gclm deficiency. We deleted Gclc in granulosa cells or oocytes of growing follicles using Gclc floxed transgenic mice paired with Amhr2-Cre or Zp3-Cre alleles respectively. We discovered that granulosa cell-specific deletion of Gclc in Amhr2Cre;Gclc(f/-) mice recapitulates the decreased litter size observed in Gclm-/- mice, but does not recapitulate the accelerated age-related decline in ovarian follicles observed in Gclm-/- mice. In addition to having lower GSH concentrations in granulosa cells, Amhr2Cre;Gclc(f/-) mice also had decreased GSH concentrations in oocytes. By contrast, oocyte-specific deletion of Gclc in Zp3Cre;Gclc(f/-) mice did not affect litter size or accelerate the age-related decline in follicle numbers, and these mice did not have decreased oocyte GSH concentrations, consistent with transport of GSH between cells via gap junctions. The results suggest that GSH deficiency at earlier stages of follicle development may be required to generate the accelerated follicle depletion phenotype observed in global Gclm null mice.
    Keywords:  Fertility; Glutamate cysteine ligase; Glutathione; Ovarian follicle; Ovary; Oxidative stress
    DOI:  https://doi.org/10.1093/biolre/ioae124
  4. J Assist Reprod Genet. 2024 Aug 13.
    Histories and mysteries underlying meiotic maturation failure in human oocytes.
    David F Albertini.
      
    DOI:  https://doi.org/10.1007/s10815-024-03221-7
  5. Methods Mol Biol. 2024 ;2818 133-145
    Analysis of Meiotic Progression by Ex Vivo Culture of Mouse Embryonic Ovaries.
    Odei Barreñada, Silvia González-Sanz, Alba López-Palacios, Jesús A Carballo, Jesús Del Mazo, Miguel A Brieño-Enríquez.
      Oogenesis is the central process required to produce viable oocytes in female mammals. It is initiated during embryonic development, and it involves the specification of primordial germ cells (PGCs) and progresses through the activation of the meiotic program, reaching a crucial phase in prophase I before pausing at diplotene around the time of birth. The significance of meiosis, particularly the prophase I stage, cannot be overstated, as it plays a pivotal role in ensuring the formation of healthy gametes, a prerequisite for successful reproduction. While research has explored meiosis across various organisms, understanding how environmental factors, including radiation, drugs, endocrine disruptors, reproductive age, or diet, influence this complex developmental process remains incomplete. In this chapter, we describe an ex vivo culture method to investigate meiotic prophase I and beyond and the disruption of oogenesis by external factors. Using this methodology, it is possible to evaluate the effects of individual xenobiotics by administering chemicals at specific points during oogenesis. This culture technique was optimized to study the effects of two selected endocrine disruptors (vinclozolin and MEHP), demonstrating that vinclozolin exposure delayed meiotic differentiation and MEHP exposure reduced follicle size. This approach also opens avenues for future applications, involving the exploration of established or novel pharmaceutical substances and their influence on essential events during prophase I, such as homologous recombination and chromosome segregation. These processes collectively dictate the ultimate fitness of oocytes, with potential implications for factors relevant to the reproductive age and fertility.
    Keywords:  3Rs; Ex vivo culture 3D; Folliculogenesis; Meiosis; Meiotic recombination; Oocyte development; Reproductive aging; Reproductive toxicology
    DOI:  https://doi.org/10.1007/978-1-0716-3906-1_8
  6. Biomater Adv. 2024 Aug 03. pii: S2772-9508(24)00230-9. [Epub ahead of print]164 213987
    3D culture of ovarian follicles in granular and nanofibrillar hydrogels.
    Marko Mihajlovic, Dóra Katalin Pásztor-Jánoska, Jesús Cadenas, Cristina Subiran Adrados, Claus Yding Andersen, Stine Gry Kristensen, Johan Ulrik Lind.
      3D culture of ovarian follicles in hydrogel matrices is an important emerging tool for basic scientific studies as well as clinical applications such as fertility preservation. For optimizing and scaling 3D culture of preantral follicles, there is a need for identifying biomaterial matrices that simplifies and improves the current culture procedures. At present, microencapsulation of follicles in alginate beads is the most commonly used approach. However, this technique involves notable manual handling and is best suited for encapsulation of single or several follicles. As a potential alternative, we here explore the suitability of different particle-based hydrogel matrices, where follicles can easily be introduced in tunable 3D environments, in large numbers. Specifically, we study the growth of secondary murine follicles in microgranular alginate and nanofibrillar cellulose matrices, with and without cell-binding cues, and map follicle growth against the viscoelastic properties of the matrices. We cultured follicles within the particle-based hydrogels for 10 days and continuously monitored their size, survival, and tendency to extrude oocytes. Interestingly, we observed that the diameter of the growing follicles increased significantly in the particle-based matrices, as compared to state-of-the-art alginate micro-encapsulation. On the other hand, the follicles displayed an increased tendency for early oocyte extrusion in the granular matrices, leading to a notable reduction in the number of intact follicles. We propose that this may be caused by impaired diffusion of nutrients and oxygen through thicker matrices, attributable to our experimental setup. Still, our findings suggest that viscoelastic, granular hydrogels represent promising matrices for 3D culture of early-stage ovarian follicles. In particular, these materials may easily be implemented in advanced culturing devices such as micro-perfusion systems.
    Keywords:  3D cell culture; Biomaterials; Matrices; Microgranular hydrogels; Nanofibers; Ovarian follicles; Reproductive biology; Scaffolds
    DOI:  https://doi.org/10.1016/j.bioadv.2024.213987
  7. J Vis Exp. 2024 Jul 26.
    Rapid Isolation of Stage I Oocytes in Zebrafish Devoid of Granulosa Cells.
    Qianwen Zheng, Xiaolong Xie, Yao Li, Chengbo Ai, Siyu Pu, Jing Chen.
      The study of oocyte development holds significant implications in developmental biology. The zebrafish (Danio rerio) has been extensively used as a model organism to investigate early developmental processes from oocyte to embryo. In zebrafish, oocytes are surrounded by a single layer of somatic granulosa cells. However, separating granulosa cells from oocytes poses a challenge, as achieving pure oocytes is crucial for precise analysis. Although various methods have been proposed to isolate zebrafish oocytes at different developmental stages, current techniques fall short in removing granulosa cells completely, limiting the accuracy of genome analysis focused solely on oocytes. In this study, we successfully developed a rapid and efficient process for isolating pure stage I oocytes in zebrafish while eliminating granulosa cell contamination. This technique facilitates biochemical and molecular analysis, particularly in exploring epigenetic and genome structure aspects specific to oocytes. Notably, the method is user-friendly, minimizes oocyte damage, and provides a practical solution for subsequent research and analysis.
    DOI:  https://doi.org/10.3791/66458
  8. Reprod Biol Endocrinol. 2024 Aug 14. 22(1): 103
    Molecular regulation of DNA damage and repair in female infertility: a systematic review.
    Xiuhua Xu, Ziwei Wang, Luyi Lv, Ci Liu, Lili Wang, Ya-Nan Sun, Zhiming Zhao, Baojun Shi, Qian Li, Gui-Min Hao.
      DNA damage is a key factor affecting gametogenesis and embryo development. The integrity and stability of DNA are fundamental to a woman's successful conception, embryonic development, pregnancy and the production of healthy offspring. Aging, reactive oxygen species, radiation therapy, and chemotherapy often induce oocyte DNA damage, diminished ovarian reserve, and infertility in women. With the increase of infertility population, there is an increasing need to study the relationship between infertility related diseases and DNA damage and repair. Researchers have tried various methods to reduce DNA damage in oocytes and enhance their DNA repair capabilities in an attempt to protect oocytes. In this review, we summarize recent advances in the DNA damage response mechanisms in infertility diseases such as PCOS, endometriosis, diminished ovarian reserve and hydrosalpinx, which has important implications for fertility preservation.
    Keywords:  DNA damage; DNA damage response; DNA repair; Infertility; Oocyte; ROS
    DOI:  https://doi.org/10.1186/s12958-024-01273-z
  9. Nat Rev Genet. 2024 Aug 12.
    DNA methylation in mammalian development and disease.
    Zachary D Smith, Sara Hetzel, Alexander Meissner.
      The DNA methylation field has matured from a phase of discovery and genomic characterization to one seeking deeper functional understanding of how this modification contributes to development, ageing and disease. In particular, the past decade has seen many exciting mechanistic discoveries that have substantially expanded our appreciation for how this generic, evolutionarily ancient modification can be incorporated into robust epigenetic codes. Here, we summarize the current understanding of the distinct DNA methylation landscapes that emerge over the mammalian lifespan and discuss how they interact with other regulatory layers to support diverse genomic functions. We then review the rising interest in alternative patterns found during senescence and the somatic transition to cancer. Alongside advancements in single-cell and long-read sequencing technologies, the collective insights made across these fields offer new opportunities to connect the biochemical and genetic features of DNA methylation to cell physiology, developmental potential and phenotype.
    DOI:  https://doi.org/10.1038/s41576-024-00760-8
  10. F S Sci. 2024 Aug 08. pii: S2666-335X(24)00054-5. [Epub ahead of print]
    Embryonic aneuploidy - the true "last barrier in assisted reproductive technology"?
    Alexander M Quaas, Alan S Penzias, Eli Y Adashi.
      Human embryonic aneuploidy may represent one of the final frontiers in assisted reproductive technology (ART), primarily secondary to oocyte aneuploidy. Mammalian oocytes possess unique characteristics predisposing them to much higher rates of aneuploidy than sperm or most somatic cells. Some of these characteristics are age-independent, while others result from reproductive aging and environmental toxicity. A detailed understanding of these properties may lead to novel diagnostic and therapeutic tools designed to detect and prevent oocyte and embryonic aneuploidy, to overcome this ultimate barrier to success in ART.
    Keywords:  Assisted Reproductive Technology (ART); Embryonic aneuploidy; Environmental toxins; Mammalian oocytes; Reproductive aging
    DOI:  https://doi.org/10.1016/j.xfss.2024.08.002
  11. Sci Rep. 2024 08 13. 14(1): 18809
    Ice formation and its elimination in cryopreservation of oocytes.
    Abdallah W Abdelhady, David W Mittan-Moreau, Patrick L Crane, Matthew J McLeod, Soon Hon Cheong, Robert E Thorne.
      Damage from ice and potential toxicity of ice-inhibiting cryoprotective agents (CPAs) are key issues in assisted reproduction of humans, domestic and research animals, and endangered species using cryopreserved oocytes and embryos. The nature of ice formed in bovine oocytes (similar in size to oocytes of humans and most other mammals) after rapid cooling and during rapid warming was examined using synchrotron-based time-resolved x-ray diffraction. Using cooling rates, warming rates and CPA concentrations of current practice, oocytes show no ice after cooling but always develop large ice fractions-consistent with crystallization of most free water-during warming, so most ice-related damage must occur during warming. The detailed behavior of ice at warming depended on the nature of ice formed during cooling. Increasing cooling rates allows oocytes soaked as in current practice to remain essentially ice free during both cooling and warming. Much larger convective warming rates are demonstrated and will allow routine ice-free cryopreservation with smaller CPA concentrations. These results clarify the roles of cooling, warming, and CPA concentration in generating ice in oocytes and establish the structure and grain size of ice formed. Ice formation can be eliminated as a factor affecting post-warming oocyte viability and development in many species, improving outcomes and allowing other deleterious effects of the cryopreservation cycle to be independently studied.
    Keywords:  Assisted reproduction; Cryopreservation; Ice formation; Oocyte; Vitrification; X-ray diffraction
    DOI:  https://doi.org/10.1038/s41598-024-69528-8
  12. Methods Mol Biol. 2024 ;2818 195-212
    Temporal Analysis of DSB Repair Outcome in Caenorhabditis elegans Meiosis.
    Tara Hicks, Nicola Silva, Sarit Smolikove.
      The Caenorhabditis elegans germline is arranged spatiotemporally and is therefore a powerful model system for the interrogation of meiotic molecular dynamics. Coupling this property with the temporal control that the auxin-inducible degron (AID) system allows can unveil new/unappreciated roles for critical meiotic factors in specific germline regions. Here we describe a widely used approach for the introduction of degron tags to specific targets and provide a procedure for applying the AID system to C. elegans meiotic DSB repair dynamics in the germline.
    Keywords:  Auxin; Caenorhabditis elegans; Crossovers; Germline; Meiosis
    DOI:  https://doi.org/10.1007/978-1-0716-3906-1_13
  13. bioRxiv. 2024 Aug 08. pii: 2024.08.07.607092. [Epub ahead of print]
    The synaptonemal complex assembles between meiotic chromosomes by wetting.
    Spencer G Gordon, Chiu Fan Lee, Ofer Rog.
      Exchange of genetic information between the parental chromosomes during sexual reproduction is controlled by a conserved structure called the synaptonemal complex. It is composed of axes (stiff chromosomal backbones), and a central region that assembles between two parallel axes. To form exchanges, the parental chromosomes must be drawn together and aligned by the synaptonemal complex. However, its mechanism of assembly remains unknown. Here we identify an axis-central region interface in C. elegans composed of the axis component HIM-3 and the central region component SYP-5. Weaker interface prevented complete synaptonemal complex assembly, and crucially, altered its canonical layered ultrastructure. Informed by these phenotypes, we built a thermodynamic model for synaptonemal complex assembly. The model recapitulates our experimental observations, indicating that the liquid-like central region can move chromosomes by wetting the axes without active energy consumption. More broadly, our data show that condensation can bring about tightly regulated nuclear reorganization.
    DOI:  https://doi.org/10.1101/2024.08.07.607092
  14. Methods Mol Biol. 2024 ;2818 179-194
    Culture of the Intact Postnatal Naked Mole-Rat Ovary: From Meiotic Prophase to Single-Cell RNASeq.
    Patrick T Walsh, Ana Martínez-Marchal, Miguel Angel Brieño-Enríquez.
      Recently, we reported that, in the naked mole-rat (Heterocephalus glaber) ovary, there is mitotic expansion of the primordial germ cells (PGCs), and the initiation of the meiotic program occurs postnatally. This is opposite to almost all other mammals, including humans and mice, whose reproductive cycle begins very early in development. In both mouse and human, the ovaries become populated with PGCs in utero; these PGCs will later generate the oogonia. After mitotic proliferation, these cells will trigger the meiotic program and initiate meiotic prophase I. Given that all these processes happen in utero, their analysis has been very challenging; so the ability to study them postnatally and to manipulate them with inhibitors or other substances, in the naked mole-rat, opens new possibilities in the field. In this chapter, we present a comprehensive collection of protocols that permit the culture of whole naked mole-rat ovaries, followed by analysis of germ cells, from PGCs to oocytes, in meiotic prophase I, as well the obtention of single-cell suspension or single-nuclei suspension for RNASeq.
    Keywords:  Meiosis; Naked Mole-Rat; Ovary; Prophase I; Single cell/nuclei RNASeq; Whole ovary culture
    DOI:  https://doi.org/10.1007/978-1-0716-3906-1_12
  15. bioRxiv. 2024 Jul 30. pii: 2024.07.29.605686. [Epub ahead of print]
    Nuclear Argonaute protein NRDE-3 switches small RNA binding partners during embryogenesis coincident with the formation of SIMR granules.
    Shihui Chen, Carolyn M Phillips.
      RNA interference (RNAi) is a conserved gene regulation mechanism that utilizes the Argonaute protein and their associated small RNAs to exert regulatory function on complementary transcripts. While the majority of germline-expressed RNAi pathway components reside in perinuclear germ granules, it is unknown whether and how RNAi pathways are spatially organized in other cell types. Here we find that the small RNA biogenesis machinery is spatially and temporally organized during embryogenesis. Specifically, the RNAi factor, SIMR-1, forms visible concentrates during mid-embryogenesis that contain an RNA-dependent RNA polymerase, a poly-UG polymerase, and the unloaded nuclear Argonaute protein, NRDE-3. Further, we observe that many other RNAi factors form foci in embryonic cells distinct from SIMR granules, including the Argonaute protein CSR-1, underscoring a potential role for cytoplasmic concentrates of RNAi factors to promote gene regulation in embryos. Curiously, coincident with the appearance of the "SIMR granules", the small RNAs bound to NRDE-3 switch from predominantly CSR-class 22G-RNAs to ERGO-dependent 22G-RNAs. Thus, our study defines two separable roles for NRDE-3, targeting germline-expressed genes during early embryogenesis and switching later in embryogenesis to repress recently duplicated genes and retrotransposons in somatic cells, highlighting the plasticity of Argonaute proteins and the need for more precise temporal characterization of Argonaute-small RNA interactions.
    DOI:  https://doi.org/10.1101/2024.07.29.605686
  16. bioRxiv. 2024 Aug 04. pii: 2024.08.03.606476. [Epub ahead of print]
    Polo-like kinase 1 prevents excess microtubule polymerization in C. elegans oocytes to ensure faithful meiosis.
    Juhi G Narula, Sarah M Wignall.
      Sexual reproduction relies on meiosis, a specialized cell division program that produces haploid gametes. Oocytes of most organisms lack centrosomes, and therefore chromosome segregation is mediated by acentrosomal spindles. Here, we explore the role of Polo-like kinase 1 (PLK-1) in C. elegans oocytes, revealing mechanisms that ensure the fidelity of this unique form of cell division. Previously, PLK-1 was shown to be required for nuclear envelope breakdown and chromosome segregation in oocytes. We now find that PLK-1 is also required for establishing and maintaining acentrosomal spindle organization and for preventing excess microtubule polymerization in these cells. Additionally, our studies revealed an unexpected new role for this essential kinase. While PLK-1 is known to be required for centrosome maturation during mitosis, we found that removal of this kinase from oocytes caused premature recruitment of pericentriolar material to the sperm-provided centrioles following fertilization. Thus, PLK-1 suppresses centrosome maturation during oocyte meiosis, which is opposite to its role in mitosis. Taken together, our work reveals multiple new roles for PLK-1 in oocytes, identifying PLK-1 as a key player that promotes faithful acentrosomal meiosis.
    DOI:  https://doi.org/10.1101/2024.08.03.606476
  17. Methods Mol Biol. 2024 ;2818 239-248
    Automated Quantification of Meiotic Recombination Foci Position and Intensity.
    John Fozard, Chris Morgan.
      During meiosis, homologous chromosomes reciprocally exchange segments of DNA via the formation of crossovers. However, the frequency and position of crossover events along chromosomes are not random. Each chromosome must receive at least one crossover, and the formation of a crossover at one location inhibits the formation of additional crossovers nearby. These crossover patterning phenomena are referred to as "crossover assurance" and "crossover interference," respectively. One key method for quantifying meiotic crossover patterning is to immunocytologically measure the position and intensity of crossover-associated protein foci along the length of meiotic prophase I chromosomes. This approach was recently used to map the position of a conserved E3 ligase, HEI10, along Arabidopsis pachytene chromosomes, providing experimental support for a novel mechanistic "coarsening model" for crossover patterning. Here we describe a user-friendly method for automatically measuring the position and intensity of recombination-associated foci along meiotic prophase I chromosomes that is broadly applicable to studies in different eukaryotic species.
    Keywords:  Crossover interference; Meiosis; Quantitative cytogenetics; Synaptonemal complex
    DOI:  https://doi.org/10.1007/978-1-0716-3906-1_16
  18. Methods Mol Biol. 2024 ;2818 93-112
    Generation of Meiotic Mouse Models Using CRISPR/Cas9 Technology.
    Manuel Sánchez-Martín, Fernando Sánchez-Sáez, Elena Llano, Alberto M Pendás.
      In recent years, targeted genome editing has emerged as an indispensable tool for creating animal models, facilitating a comprehensive exploration of the molecular mechanisms governing a myriad of biological processes. Within this scientific landscape, the investigation of meiosis in mice has attracted considerable attention across numerous research laboratories. The precision and versatility of the CRISPR/Cas9 genome editing system have revolutionized our ability to generate mice with tailored genetic alterations, including point mutations and null mutations. These genetic modifications have provided invaluable insights into the intricate functionality of various meiotic genes and their associated variants. In this context, we present a detailed state of the art protocol for the creation of novel mouse models, each bearing specific genetic modifications within key meiotic genes, through the application of CRISPR/Cas9 technology. Furthermore, we showcase two distinct genetic modifications, accomplished within our laboratory, that can serve as valuable reference points for researchers seeking to elucidate the molecular intricacies of meiosis in mammals.
    Keywords:  CRISPR/Cas9; Genome editing; Meiosis; Mouse gametogenesis
    DOI:  https://doi.org/10.1007/978-1-0716-3906-1_6
  19. Nat Commun. 2024 Aug 13. 15(1): 6925
    Cellular sex throughout the organism underlies somatic sexual differentiation.
    Chloé Hérault, Thomas Pihl, Bruno Hudry.
      Sex chromosomes underlie the development of male or female sex organs across species. While systemic signals derived from sex organs prominently contribute to sex-linked differences, it is unclear whether the intrinsic presence of sex chromosomes in somatic tissues has a specific function. Here, we use genetic tools to show that cellular sex is crucial for sexual differentiation throughout the body in Drosophila melanogaster. We reveal that every somatic cell converts the intrinsic presence of sex chromosomes into the active production of a sex determinant, a female specific serine- and arginine-rich (SR) splicing factor. This discovery dismisses the mosaic model which posits that only a subset of cells has the potential to sexually differentiate. Using cell-specific sex reversals, we show that this prevalence of cellular sex drives sex differences in organ size and body weight and is essential for fecundity. These findings demonstrate that cellular sex drives differentiation programs at an organismal scale and highlight the importance of cellular sex pathways in sex trait evolution.
    DOI:  https://doi.org/10.1038/s41467-024-51228-6
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