bims-cebooc Biomed News
on Cell biology of oocytes
Issue of 2026–09–06
sixteen papers selected by
Gabriele Zaffagnini, Universität zu Köln
  1. Maternal DNA repair safeguards genome stability during the oocyte-to-embryo transition.
  2. Maternal metabolic stress regulates progeny intestinal stem cell niche signaling through heritable changes in redox metabolites.
  3. Imaging Spatiotemporal RNA and Protein Dynamics in Mouse Embryos.
  4. Targeted Degradation of Mouse Embryo Proteins Using Trim-Away.
  5. Pronuclear Transfer and Maternal Spindle Transfer in the Mouse.
  6. Molecular Regulation of Primordial Germ Cell Specification and Implications for In Vitro Gametogenesis.
  7. In Vitro Development of Primordial Follicles from Human Ovarian Tissue.
  8. Protocol for Duplex Sequencing of Mitochondrial DNA in Single Human Oocytes.
  9. Analysis of Relative Telomere Length and mtDNA Content in Individual Oocytes and Embryos by Quantitative Real-Time PCR (qPCR).
  10. Oocyte and Embryo Vitrification.
  11. Signaling Cascades in Meiotic Chromosome Dynamics.
  12. Immunofluorescence Analysis of Epigenetic Markers in Oocytes and Preimplantation Embryos.
  13. ERH elicits cell lineage restriction in mammalian preimplantation development and differentiation from pluripotency via H3K9me3-heterochromatin.
  14. Evaluating Preimplantation Embryo Metabolism Through Imaging of Cellular Autofluorescence.
  15. Characterization of the metabolome and proteome of stem cell-derived human primordial germ cell-like cells: a multi-omics approach.
  16. Capacitation In Vitro Maturation (CAPA-IVM) of Human Oocytes.
  1. Mol Hum Reprod. 2026 Sep 03. pii: gaag050. [Epub ahead of print]
    Maternal DNA repair safeguards genome stability during the oocyte-to-embryo transition.
    Mateus P Grejo, J Djaci Augusto Neto, Angélica C Dos Santos, Lindomar O Alves, Carolina H Macabelli, Sérgio A G Pereira-Júnior, Tainã F Cardoso, Anand K Pandey, Suellen G B Clemente, Deborah N Yokomizo, Marcelo M Seneda, Ricardo P Nociti, Flávio V Meirelles, Patrick F Chinnery, Rodrigo A P Martins, Pierre-Olivier Frappart, Marcos R Chiaratti.
      De novo mutations are a major source of genetic variation and disease risk, yet the developmental timing and mechanisms underlying their origin require further investigation. While germ cells have traditionally been considered the primary source of these mutations, increasing evidence suggests that a substantial fraction arise after fertilization. Here, we investigated the role of maternal DNA repair in shaping mutagenesis during this critical window by using a mouse model with oocyte-specific disruption of the homologous recombination factor RAD51 and a combination of cellular and molecular analyses. Loss of maternal RAD51 led to the accumulation of DNA double-strand breaks in oocytes without impairing their growth, meiotic maturation, or fertilization competence. In contrast, embryos derived from RAD51-deficient oocytes exhibited increased DNA damage and developmental delay during early cleavage stages. Whole-genome sequencing revealed a significant increase in de novo variants in offspring, the majority displaying intermediate allele frequencies consistent with post-zygotic mosaic mutations. These findings confirm that maternal DNA repair safeguards genome stability across the oocyte-to-embryo transition and identify early embryogenesis as a major source of de novo mutations, with implications for reproductive biology and the origins of genetic diseases.
    Keywords:  DNA; DNV; DSB; RAD51; SNV; embryo; homologous recombination; mutation; oocyte; repair
    DOI:  https://doi.org/10.1093/molehr/gaag050
  2. Nat Commun. 2026 08 03. pii: 9338. [Epub ahead of print]17(1):
    Maternal metabolic stress regulates progeny intestinal stem cell niche signaling through heritable changes in redox metabolites.
    Helin Hocaoglu, Shenlu Qin, Leah Eller, Farhan Abu, Benjamin Ohlstein, Lei Wang, Matthew H Sieber.
      Maternal metabolic stress is a major determinant of progeny health and disease susceptibility, yet the mechanisms linking germline metabolism to lifelong changes in tissue physiology remain poorly defined. Here, we show that maternal metabolic stress alters the cellular composition of the progeny intestinal epithelium through a conserved metabolic pathway. Germline metabolic dysfunction depletes NAD⁺ in mature oocytes, reprogramming progeny redox metabolism and impairing the methionine cycle. This metabolic shift reduces protein levels of the Notch ligand Delta, disrupting intestinal stem cell niche signaling and altering progeny intestinal physiology. Across insect and mammalian models, our findings reveal that maternal metabolic health has conserved effects on progeny metabolism and intestinal function. Together, this work identifies heritable redox-metabolic changes as a mechanistic link between maternal metabolic stress, stem cell regulation, and intestinal disease susceptibility.
    DOI:  https://doi.org/10.1038/s41467-026-76249-1
  3. Methods Mol Biol. 2026 ;3038 197-225
    Imaging Spatiotemporal RNA and Protein Dynamics in Mouse Embryos.
    Hongbin Jin, Jennifer Zenker.
      To study subcellular real-time dynamics in preimplantation embryos of mammals such as mice, the gold standard is currently to microinject fluorescently tagged constructs to visualize their protein products, which has significantly advanced our knowledge of early mammalian embryogenesis. However, during early embryonic development, it is recognized that mRNAs are precisely localized in space and time inside single cells to ensure their gene products, such as proteins, are synthesized and available when and where they are needed. Here, we describe a method that enables the simultaneous real-time imaging of RNAs and proteins of interest at the subcellular level in living mammalian embryos. Additionally, we present imaging settings specifically tailored for live mouse embryos, using a confocal microscope to visualize the real-time interactions between proteins and RNAs, such as mRNA transport along microtubule filaments.
    Keywords:  Fluorescence; Live imaging; Microtubule cytoskeleton; Mouse preimplantation embryo; RNA
    DOI:  https://doi.org/10.1007/978-1-0716-5292-3_12
  4. Methods Mol Biol. 2026 ;3038 399-423
    Targeted Degradation of Mouse Embryo Proteins Using Trim-Away.
    Thomas Nolte, Steffen Israel, Michele Boiani.
      Trim-Away is an antibody-based method for the degradation of endogenous cellular proteins without prior genetic manipulation. From the effect that protein degradation has on the phenotype, one can infer the function of the protein-coding gene. Among the strengths of Trim-Away, the authors highlight the possibility to target embryonic proteins that have not yet been produced or are not yet functionally required at the time of antibody delivery. Conversely, a limitation of Trim-Away is the possibility that while the target protein is being degraded, de novo translation may replenish it, whereby the two processes offset each other, and the phenotype is inconspicuous. Appropriate controls, as described, are therefore essential for the correct interpretation of Trim-Away results. With these considerations in mind, the authors provide guidance on how to set up a Trim-Away experiment in fertilized mouse oocytes, using microinjection as the delivery method and the epithelial CADHERIN protein as an example.
    Keywords:  Antibody; E-CADHERIN; Mouse; Oocyte; Protein of interest (POI); TRIM 21 protein; Trim21 mRNA
    DOI:  https://doi.org/10.1007/978-1-0716-5292-3_22
  5. Methods Mol Biol. 2026 ;3038 477-493
    Pronuclear Transfer and Maternal Spindle Transfer in the Mouse.
    Ross Stocker, Jeffrey R Mann, John Carroll.
      Maternal Spindle Transfer (MST) and Pronuclear Transfer (PNT) are micromanipulation techniques that allow the transfer of the nuclear material from one oocyte or zygote to the cytoplasm of another. The application of these techniques has provided novel insights into nuclear-cytoplasmic interactions necessary for development, as well as fundamental discoveries such as genomic imprinting. Now, after extensive pre-clinical research, PNT and MST are starting to be used clinically for Mitochondrial Donation (also known as mitochondrial replacement therapy) and for patients with a history of repeated IVF failure. Here, we describe the methods for PNT and MST currently used in the mouse model. The techniques are readily adaptable for application to other mammalian species, including humans.
    Keywords:  Maternal spindle transfer; Mitochondrial disease; Mouse; Oocyte; Pronuclear transfer; Sendai virus; Zygote
    DOI:  https://doi.org/10.1007/978-1-0716-5292-3_25
  6. Biol Reprod. 2026 Sep 03. pii: ioag188. [Epub ahead of print]
    Molecular Regulation of Primordial Germ Cell Specification and Implications for In Vitro Gametogenesis.
    Maddison Marshall, Eryl Bevan, Yuan Wang.
      Primordial germ cells (PGCs) are the embryonic precursors of gametes, essential for transmitting genetic and epigenetic information across generations. However, PGC specification occurs within a narrow developmental window and involves only a small number of cells, making it difficult to study in vivo. In vitro models using pluripotent stem cells have enabled the generation of primordial germ cell-like cells, but these systems often rely on exogenous signaling and exhibit variability in efficiency and epigenetic fidelity. In this review, we synthesize current understanding of PGC specification in mouse and human systems, emphasizing the integration of signaling pathways, transcriptional networks, epigenetic reprogramming, and metabolic regulation. Canonical regulators, including PRDM1, PRDM14, TFAP2C, and SOX17, function within a broader, interconnected network that establishes for PGC competence. Understanding these interactions will be crucial for advancing in vitro gametogenesis and improving mammalian reproduction.
    Keywords:  mammalian reproduction; pluripotent stem cells; primordial germ cells
    DOI:  https://doi.org/10.1093/biolre/ioag188
  7. Methods Mol Biol. 2026 ;3038 1-14
    In Vitro Development of Primordial Follicles from Human Ovarian Tissue.
    Evelyn E Telfer, Yvonne L Odey.
      The ability to develop human oocytes from the primordial stage to full maturation entirely in vitro presents profound opportunities. Beyond advancing basic science in oogenesis and meiosis, in vitro growth systems hold immense potential for novel assisted reproductive technologies (ARTs). Advances in deriving oocytes from stem cells combined with in vitro growth and in vitro maturation hold the promise of revolutionizing fertility preservation. Should these stem cell-derived oocytes prove functionally competent, in combination with IVG systems they could ultimately reduce reliance on donor gametes and expand reproductive options for a wide range of patients. Looking ahead, refining culture conditions to more closely mimic the in vivo ovarian niche will be essential for improving oocyte quality and developmental competence. Ethical and regulatory frameworks will also need to evolve to address the unique challenges posed by in vitro-derived gametes. As genomic, epigenetic, and metabolic profiling techniques advance, they will enable rigorous assessment of the safety and fidelity of IVG derived oocytes. In the long term, these technologies could not only transform fertility treatment but also serve as powerful models for studying human germline development, inheritance, and disease. This chapter outlines a methodology for developing human oocytes from primordial follicles to maturity.
    Keywords:  Follicle culture; In vitro growth (IVG); In vitro maturation (IVM); Oocyte maturation; Ovarian cortex; Ovary
    DOI:  https://doi.org/10.1007/978-1-0716-5292-3_1
  8. J Vis Exp. 2026 Sep 03.
    Protocol for Duplex Sequencing of Mitochondrial DNA in Single Human Oocytes.
    Teresa Kloimboeck, Thomas Ebner, Kateryna Makova, Barbara Arbeithuber.
      Oocytes are densely packed with mitochondria, the energy-producing organelles that contain their own genome, mitochondrial DNA (mtDNA). Each cell contains multiple copies of mtDNA, with copy number varying among tissue types. Oocytes possess the highest mtDNA copy number, containing hundreds of thousands of mtDNA molecules per cell. Because mitochondria are inherited exclusively through the maternal lineage, accurate detection of mtDNA variants is essential for studies of inheritance, aging, and disease. The presence of multiple mtDNA copies allows wild-type and mutant molecules to coexist within the same cell, a condition known as heteroplasmy, in which low-frequency and de novo variants may occur at frequencies below 1%. Conventional next-generation sequencing (NGS) lacks sufficient accuracy to reliably distinguish these rare variants from errors introduced during library preparation and sequencing. Here, we present a protocol for enriching mtDNA from single human oocytes using Exonuclease V to remove linear DNA, followed by duplex sequencing library preparation for highly accurate mtDNA analysis. This workflow enables error-corrected sequencing of individual oocytes, facilitating reliable detection of low-frequency mtDNA variants and analysis of heteroplasmy and de novo mutagenesis. The protocol provides a reproducible approach for investigating mitochondrial genome variation in single oocytes using Illumina-compatible sequencing platforms.
    DOI:  https://doi.org/10.3791/73071
  9. Methods Mol Biol. 2026 ;3038 249-263
    Analysis of Relative Telomere Length and mtDNA Content in Individual Oocytes and Embryos by Quantitative Real-Time PCR (qPCR).
    Yasmyn E Winstanley, Darryl L Russell, Rebecca L Robker.
      Oocytes and embryos are highly susceptible to intrinsic and extrinsic stressors, making assays for biomarkers of embryo quality of high importance. This has been technically challenging due to the very small amounts of material in embryos, leading to the use of assays requiring pooled embryos which mask inter-embryo variability. This protocol details a qPCR assay to analyze relative telomere lengths and mtDNA content in individual oocytes and embryos. Each is singly collected and lysed in a minimal volume, then qPCR is used to independently amplify two nuclear (telomere and Rn18S) and one mitochondrial DNA sequence for quantification of relative telomere length or mtDNA content that is normalized for cell number by the reference gene. This methodology enables robust and precise measurements of these molecular biomarkers in physiological contexts where tissue availability is limited. Importantly, this assay allows detection of the natural variability in mtDNA and telomeric DNA content between individual oocytes and embryos.
    Keywords:  Embryo; Mitochondrial DNA; Mouse; Oocyte; Telomere; qPCR
    DOI:  https://doi.org/10.1007/978-1-0716-5292-3_15
  10. Methods Mol Biol. 2026 ;3038 121-134
    Oocyte and Embryo Vitrification.
    Masashige Kuwayama, Gabriel Dalvit.
      Widespread use of oocyte cryopreservation began after the introduction of vitrification, allowing women to postpone childbearing, precipitated by age-related declines in fertility. Similarly, vitrification offers poor responder patients the option of accumulating embryos. Over the last decade, several advances in vitrification technologies have improved clinical efficiency and outcome, reduced the dependence on operator skills, and raised success rates to higher and more uniform levels. As a result, vitrification has become reliable and safe, completely replacing slow cooling as the method of choice. Minimum volume methods, in particular the advanced Cryotec Ready to Use (RtU) system, as described here, ensure achieving the highest viability in oocytes and embryos at any stage can be achieved safely. A robust vitrification protocol is therefore a cornerstone of any ART program.
    Keywords:  Cryotec method; Embryos; Oocytes; Vitrification
    DOI:  https://doi.org/10.1007/978-1-0716-5292-3_8
  11. Annu Rev Genet. 2026 Sep 01.
    Signaling Cascades in Meiotic Chromosome Dynamics.
    Dahlia Y Deng, Jocelyn Haversat, Yumi Kim.
      Meiosis is a specialized cell division essential for sexual reproduction, generating haploid gametes through two consecutive nuclear divisions following a single round of DNA replication. During an extended meiotic prophase I, chromosomes undergo elaborate rearrangements, such as pairing, synapsis, and recombination, culminating in crossovers that physically link homologs for accurate segregation. Errors in these processes cause aneuploidy, a leading contributor to infertility, miscarriage, and congenital disorders. These chromosomal events must be precisely coordinated with cell cycle transitions through signaling pathways involving cell cycle and DNA damage checkpoint kinases, as well as ubiquitin-mediated regulation. These pathways control the timing and levels of programmed DNA double-strand breaks, monitor synapsis and crossover formation, and enforce surveillance checkpoints that eliminate defective cells. This review examines how signaling networks orchestrate chromosome dynamics during meiotic prophase, highlighting conserved principles and organism-specific adaptations that ensure faithful genetic transmission across generations.
    DOI:  https://doi.org/10.1146/annurev-genet-011626-030553
  12. Methods Mol Biol. 2026 ;3038 337-359
    Immunofluorescence Analysis of Epigenetic Markers in Oocytes and Preimplantation Embryos.
    Marcella Pecora Milazzotto, Jessica Ispada.
      Immunofluorescence (IF) is an essential technique for studying epigenetic modifications in embryos. It offers high spatial resolution for precise visualization of chromatin-associated proteins and modifications involved in gene regulation and epigenetic reprogramming. IF allows multiplexing with multiple fluorophores, enabling the study of protein interactions and co-localization. Widely used in gametes and embryos across species, IF aids in analyzing epigenetic-related protein expression and localization during various stages of development.
    Keywords:  Embryo; Epigenetic; Gamete; Immunofluorescence
    DOI:  https://doi.org/10.1007/978-1-0716-5292-3_19
  13. Nat Commun. 2026 07 30. pii: 9262. [Epub ahead of print]17(1):
    ERH elicits cell lineage restriction in mammalian preimplantation development and differentiation from pluripotency via H3K9me3-heterochromatin.
    Andrew Katznelson, Blake Hernandez, Kylea Tapia, Holly Fahning, Adam Burton, Jingchao Zhang, Maria-Elena Torres-Padilla, Nicolas Plachta, Kenneth S Zaret, Ryan L McCarthy.
      Enhancer of Rudimentary Homolog (ERH) is an evolutionarily conserved protein originally characterized as promoting fission yeast heterochromatin and recently shown to maintain H3K9me3 heterochromatin in human fibroblasts. Here, we find that ERH depletion in fibroblasts reverts the somatic cell H3K9me3 landscape of broad megabase size domains to an embryonic stem cell (ESC) state composed of mainly H3K9me3 peaks and enables activation of naïve and pluripotency genes and transposable elements during induced pluripotent stem cell (iPSC) reprogramming. Concordantly, we find that ERH represses totipotent and alternative lineage programs during mouse preimplantation development and is required for proper segregation of the inner cell mass and trophectoderm cell lineages. During human ESC differentiation into germ layer lineages, ERH silences naïve and pluripotency genes, transposable elements, and alternative lineage somatic genes. As in fission yeast, we find that mammalian ERH interacts with RNA-binding proteins to engage and repress its chromatin targets. Our findings reveal a conserved, fundamental role for ERH in mammalian cell fate specification via the initiation and maintenance of early developmental gene repression.
    DOI:  https://doi.org/10.1038/s41467-026-76015-3
  14. Methods Mol Biol. 2026 ;3038 171-195
    Evaluating Preimplantation Embryo Metabolism Through Imaging of Cellular Autofluorescence.
    Darren J X Chow, Tiffany C Y Tan, Kishan Dholakia, Kylie R Dunning.
      Optical imaging offers a non-invasive approach for assessing embryo viability. This may be achieved through capturing fluorescence from endogenous fluorophores that are associated with cellular metabolism. By recording and analysing natural autofluorescence emitted by molecules involved in metabolism, such as NADH and FAD, this technique offers crucial insights into the metabolic state of embryos, in the absence of exogenous labels. This approach is particularly valuable for preimplantation embryos developed in vitro, where the ability to identify those with high developmental potential may lead to improved outcomes in a clinical setting. Light sheet microscopy has recently emerged as a powerful imaging modality suitable for recording autofluorescence from the developing embryo. In contrast to standard point-scanning (confocal) approaches, it only illuminates the plane of interest, minimising light exposure and photodamage while enabling rapid 3D image acquisition. These aspects make light sheet microscopy particularly well-suited for metabolic imaging of live preimplantation embryos. In this chapter, we describe a general procedure to perform metabolic imaging of live mammalian embryos using light sheet microscopy. This protocol enables direct observation of metabolic changes within embryos in a spatial manner and provides guidelines for optimising imaging parameters to ensure accuracy and reproducibility.
    Keywords:  Autofluorescence; Confocal microscopy; Label-free; Light sheet microscopy; Metabolism; Murine preimplantation embryo; Optical imaging
    DOI:  https://doi.org/10.1007/978-1-0716-5292-3_11
  15. Biol Open. 2026 Sep 03. pii: bio.062801. [Epub ahead of print]
    Characterization of the metabolome and proteome of stem cell-derived human primordial germ cell-like cells: a multi-omics approach.
    Madalena Vaz Santos, Bauke V Schomakers, Marta Llobet Ayala, Tara Jamali, Michel van Weeghel, Ans M van Pelt, Callista L Mulder, Geert Hamer.
      Primordial germ cells (PGCs) are the population of cells that, in the human embryo, are initially specified at day 12 post-fertilization, and form the precursor cells for the future gametes. Although in vitro differentiation of PGCs from human stem cells has been achieved, these primordial germ cell-like cells (hPGCLCs) fail to completely mature without the use of ex vivo human or animal gonadal soma. Previous studies in mice revealed that several metabolic changes occur during the specification and maturation of these cells, which are essential for their developmental progress. However, little is known about the metabolic profile of human primordial germ cells. In the scarcity of human PGCs, particularly at the early specification stage, hPGCLCs serve as a research model to study PGC formation. To characterize the metabolic and proteomic profile of these cells, we differentiated hPGCLCs using induced-pluripotent stem cells and performed a mass spectrometry analysis to establish their metabolome and proteome. These cells revealed distinct metabolic profile, with changes particularly at the proteome level. This included a shift between canonical and non-canonical citric acid cycle in hPGCLCs, downregulation of late-stage glycolysis and reduction of nucleotide de novo synthesis. By providing an integrative map of these metabolic networks, we aim to provide insight on the metabolism of hPGCLC development that could help improve methods for fully in vitro differentiation and maturation of hPGCLCs.
    Keywords:  Human; In vitro; Induced-pluripotent stem cells; Metabolome; Primordial germ cells; Proteome
    DOI:  https://doi.org/10.1242/bio.062801
  16. Methods Mol Biol. 2026 ;3038 15-25
    Capacitation In Vitro Maturation (CAPA-IVM) of Human Oocytes.
    Lan N Vuong, Anh H Le, Tuong M Ho, Robert B Gilchrist.
      Oocyte in vitro maturation (IVM) is a patient-friendly technique that generates mature oocytes in vitro from patients who receive minimal or no gonadotrophin stimulation. Although it was discovered a long time ago, the clinical application of IVM has been constrained by its lower success rates compared with conventional IVF, principally due to suboptimal oocyte competency. Recent advancements in the culture system for immature oocytes have significantly enhanced both maturation efficiency and embryo quality. Consequently, this technique is experiencing a resurgence in interest among clinicians and embryologists globally. This chapter details the laboratory protocols employed in a novel form of IVM, called capacitation (CAPA) IVM.
    Keywords:  Biphasic IVM; In vitro maturation of oocyte; Standard IVM
    DOI:  https://doi.org/10.1007/978-1-0716-5292-3_2
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