bims-cebooc Biomed News
on Cell biology of oocytes
Issue of 2024–08–11
twelve papers selected by
Gabriele Zaffagnini, Centre for Genomic Regulation
  1. Female-specific mechanisms of meiotic initiation and progression in mammalian oocyte development.
  2. RNAseq analysis of oocyte maturation from the germinal vesicle stage to metaphase II in pig and human.
  3. Unique hyaluronan structure of expanded oocyte-cumulus extracellular matrix in ovarian follicles.
  4. The interferon γ pathway enhances pluripotency and X-chromosome reactivation in iPSC reprogramming.
  5. Identification of novel cattle (Bos taurus) genes and biological insights of their function in pre-implantation embryo development.
  6. Oocyte-specific deletion of eukaryotic translation initiation factor 5 causes apoptosis of mouse oocytes within the early-growing follicles by mitochondrial fission defect-reactive oxygen species-DNA damage.
  7. Cyclin B3 is a dominant fast-acting cyclin that drives rapid early embryonic mitoses.
  8. Participation of preovulatory follicles in the activation of primordial follicles in mouse ovaries.
  9. BRCA1/BRC-1 and SMC-5/6 regulate DNA repair pathway engagement during C. elegans meiosis.
  10. RAB37-mediated autophagy guards ovarian homeostasis and function.
  11. Mechanical remodeling of nuclear biomolecular condensates.
  12. Attenuation of endoplasmic reticulum stress improves invitro growth and subsequent maturation of bovine oocytes.
  1. Genes Cells. 2024 Aug 09.
    Female-specific mechanisms of meiotic initiation and progression in mammalian oocyte development.
    Ryuki Shimada, Kei-Ichiro Ishiguro.
      Meiosis is regulated in sexually dimorphic manners in mammals. In females, the commitment to and entry into meiosis are coordinated with the developmental program of oocytes. Female germ cells initiate meiosis within a short time window during the fetal period and then undergo meiotic arrest until puberty. However, the genetic mechanisms underlying the orchestration of oocyte development and meiosis to maximize the reproductive lifespan of mammalian females remain largely elusive. While meiotic initiation is regulated by a sexually common mechanism, where meiosis initiator and Stimulated by Retinoic Acid Gene 8 (STRA8) activate the meiotic genes, the female-specific mode of meiotic initiation is mediated by the interaction between retinoblastoma (RB) and STRA8. This review highlights the female-specific mechanisms of meiotic initiation and meiotic prophase progression in the context of oocyte development. Furthermore, the downstream pathway of the RB-STRA8 interaction that may regulate meiotic arrest will be discussed in the context of oocyte development, highlighting a potential genetic link between the female-specific mode of meiotic entry and meiotic arrest.
    Keywords:  development; germ cell; meiosis; oocyte
    DOI:  https://doi.org/10.1111/gtc.13152
  2. PLoS One. 2024 ;19(8): e0305893
    RNAseq analysis of oocyte maturation from the germinal vesicle stage to metaphase II in pig and human.
    Feng Tang, Katja Hummitzsch, Raymond J Rodgers.
      During maturation oocytes at the germinal vesicle (GV) stage progress to metaphase II (MII). However, during in vitro maturation a proportion often fail to progress. To understand these processes, we employed RNA sequencing to examine the transcriptome profile of these three groups of oocytes from the pig. We compared our findings with similar public oocyte data from humans. The transcriptomes in oocytes that failed to progress was similar to those that did. We found in both species, the most upregulated genes in MII oocytes were associated with chromosome segregation and cell cycle processes, while the most down regulated genes were relevant to ribosomal and mitochondrial pathways. Moreover, those genes involved in chromosome segregation during GV to MII transition were conserved in pig and human. We also compared MII and GV oocyte transcriptomes at the isoform transcript level in both species. Several thousands of genes (including DTNBP1, MAPK1, RAB35, GOLGA7, ATP1A1 and ATP2B1) identified as not different in expression at a gene transcript level were found to have differences in isoform transcript levels. Many of these genes were involved in ATPase-dependent or GTPase-dependent intracellular transport in pig and human, respectively. In conclusion, our study suggests the failure to progress to MII in vitro may not be regulated at the level of the genome and that many genes are differentially regulated at the isoform level, particular those involved ATPase- or GTPase-dependent intracellular transport.
    DOI:  https://doi.org/10.1371/journal.pone.0305893
  3. Endocr Regul. 2024 Jan 01. 58(1): 174-180
    Unique hyaluronan structure of expanded oocyte-cumulus extracellular matrix in ovarian follicles.
    Eva Nagyova, Alzbeta Bujnakova Mlynarcikova, Lucie Nemcova, Sona Scsukova.
      In preovulatory follicles, after the endogenous gonadotropin surge, the oocyte-cumulus complexes (OCCs) produce hyaluronan (HA) in a process called "cumulus expansion". During this process, the heavy chains (HCs) of the serum-derived inter-alpha-trypsin inhibitor (IαI) family bind covalently to synthesized HA and form a unique structure of the expanded cumulus HA-rich extracellular matrix. Understanding the biochemical mechanism of the covalent linkage between HA and the HCs of the IαI family is one of the most significant discoveries in reproductive biology, since it explains basis of the cumulus expansion process running in parallel with the oocyte maturation, both essential for ovulation. Two recent studies have supported the above-mentioned findings: in the first, seven components of the extracellular matrix were detected by proteomic, evolutionary, and experimental analyses, and in the second, the essential role of serum in the process of cumulus expansion in vitro was confirmed. We have previously demonstrated the formation of unique structure of the covalent linkage of HA to HCs of IαI in the expanded gonadotropin-stimulated OCC, as well as interactions with several proteins produced by the cumulus cells: tumor necrosis factor-alpha-induced protein 6, pentraxin 3, and versican. Importantly, deletion of these genes in the mice produces female infertility due to defects in the oocyte-cumulus structure.
    Keywords:  cumulus expansion; extracellular matrix; hyaluronan; inter-alpha-trypsin inhibitor
    DOI:  https://doi.org/10.2478/enr-2024-0020
  4. Sci Adv. 2024 Aug 09. 10(32): eadj8862
    The interferon γ pathway enhances pluripotency and X-chromosome reactivation in iPSC reprogramming.
    Mercedes Barrero, Aleksey Lazarenkov, Enrique Blanco, Luis G Palma, Anna V López-Rubio, Moritz Bauer, Anna Bigas, Luciano Di Croce, José Luis Sardina, Bernhard Payer.
      Reprogramming somatic cells into induced pluripotent stem cells (iPSCs) requires activation of the pluripotency network and resetting of the epigenome by erasing the epigenetic memory of the somatic state. In female mouse cells, a critical epigenetic reprogramming step is the reactivation of the inactive X chromosome. Despite its importance, a systematic understanding of the regulatory networks linking pluripotency and X-reactivation is missing. Here, we reveal important pathways for pluripotency acquisition and X-reactivation using a genome-wide CRISPR screen during neural precursor to iPSC reprogramming. In particular, we discover that activation of the interferon γ (IFNγ) pathway early during reprogramming accelerates pluripotency acquisition and X-reactivation. IFNγ stimulates STAT3 signaling and the pluripotency network and leads to enhanced TET-mediated DNA demethylation, which consequently boosts X-reactivation. We therefore gain a mechanistic understanding of the role of IFNγ in reprogramming and X-reactivation and provide a comprehensive resource of the molecular networks involved in these processes.
    DOI:  https://doi.org/10.1126/sciadv.adj8862
  5. BMC Genomics. 2024 Aug 09. 25(1): 775
    Identification of novel cattle (Bos taurus) genes and biological insights of their function in pre-implantation embryo development.
    Gustavo P Schettini, Michael Morozyuk, Fernando H Biase.
       BACKGROUND: Appropriate regulation of genes expressed in oocytes and embryos is essential for acquisition of developmental competence in mammals. Here, we hypothesized that several genes expressed in oocytes and pre-implantation embryos remain unknown. Our goal was to reconstruct the transcriptome of oocytes (germinal vesicle and metaphase II) and pre-implantation cattle embryos (blastocysts) using short-read and long-read sequences to identify putative new genes.
    RESULTS: We identified 274,342 transcript sequences and 3,033 of those loci do not match a gene present in official annotations and thus are potential new genes. Notably, 63.67% (1,931/3,033) of potential novel genes exhibited coding potential. Also noteworthy, 97.92% of the putative novel genes overlapped annotation with transposable elements. Comparative analysis of transcript abundance identified that 1,840 novel genes (recently added to the annotation) or potential new genes were differentially expressed between developmental stages (FDR < 0.01). We also determined that 522 novel or potential new genes (448 and 34, respectively) were upregulated at eight-cell embryos compared to oocytes (FDR < 0.01). In eight-cell embryos, 102 novel or putative new genes were co-expressed (|r|> 0.85, P < 1 × 10-8) with several genes annotated with gene ontology biological processes related to pluripotency maintenance and embryo development. CRISPR-Cas9 genome editing confirmed that the disruption of one of the novel genes highly expressed in eight-cell embryos reduced blastocyst development (ENSBTAG00000068261, P = 1.55 × 10-7).
    CONCLUSIONS: Our results revealed several putative new genes that need careful annotation. Many of the putative new genes have dynamic regulation during pre-implantation development and are important components of gene regulatory networks involved in pluripotency and blastocyst formation.
    Keywords:  Embryos; Gene annotation; Transcriptome
    DOI:  https://doi.org/10.1186/s12864-024-10685-5
  6. Clin Transl Med. 2024 Aug;14(8): e1791
    Oocyte-specific deletion of eukaryotic translation initiation factor 5 causes apoptosis of mouse oocytes within the early-growing follicles by mitochondrial fission defect-reactive oxygen species-DNA damage.
    Weiyong Wang, Huiyu Liu, Shuang Liu, Tiantian Hao, Ying Wei, Hongwei Wei, Wenjun Zhou, Xiaodan Zhang, Xiaoqiong Hao, Meijia Zhang.
       BACKGROUND: Mutations in several translation initiation factors are closely associated with premature ovarian insufficiency (POI), but the underlying pathogenesis remains largely unknown.
    METHODS AND RESULTS: We generated eukaryotic translation initiation factor 5 (Eif5) conditional knockout mice aiming to investigate the function of eIF5 during oocyte growth and follicle development. Here, we demonstrated that Eif5 deletion in mouse primordial and growing oocytes both resulted in the apoptosis of oocytes within the early-growing follicles. Further studies revealed that Eif5 deletion in oocytes downregulated the levels of mitochondrial fission-related proteins (p-DRP1, FIS1, MFF and MTFR) and upregulated the levels of the integrated stress response-related proteins (AARS1, SHMT2 and SLC7A1) and genes (Atf4, Ddit3 and Fgf21). Consistent with this, Eif5 deletion in oocytes resulted in mitochondrial dysfunction characterized by elongated form, aggregated distribution beneath the oocyte membrane, decreased adenosine triphosphate content and mtDNA copy numbers, and excessive accumulation of reactive oxygen species (ROS) and mitochondrial superoxide. Meanwhile, Eif5 deletion in oocytes led to a significant increase in the levels of DNA damage response proteins (γH2AX, p-CHK2 and p-p53) and proapoptotic proteins (PUMA and BAX), as well as a significant decrease in the levels of anti-apoptotic protein BCL-xL.
    CONCLUSION: These findings indicate that Eif5 deletion in mouse oocytes results in the apoptosis of oocytes within the early-growing follicles via mitochondrial fission defects, excessive ROS accumulation and DNA damage. This study provides new insights into pathogenesis, genetic diagnosis and potential therapeutic targets for POI.
    KEY POINTS: Eif5 deletion in oocytes leads to arrest in oocyte growth and follicle development. Eif5 deletion in oocytes impairs the translation of mitochondrial fission-related proteins, followed by mitochondrial dysfunction. Depletion of Eif5 causes oocyte apoptosis via ROS accumulation and DNA damage response pathway.
    Keywords:  POI; eIF5; follicle development; mitochondrial fission; oocyte growth
    DOI:  https://doi.org/10.1002/ctm2.1791
  7. J Cell Biol. 2024 Nov 04. pii: e202308034. [Epub ahead of print]223(11):
    Cyclin B3 is a dominant fast-acting cyclin that drives rapid early embryonic mitoses.
    Pablo Lara-Gonzalez, Smriti Variyar, Shabnam Moghareh, Anh Cao Ngoc Nguyen, Amrutha Kizhedathu, Jacqueline Budrewicz, Aleesa Schlientz, Neha Varshney, Andrew Bellaart, Karen Oegema, Lee Bardwell, Arshad Desai.
      Mitosis in early embryos often proceeds at a rapid pace, but how this pace is achieved is not understood. Here, we show that cyclin B3 is the dominant driver of rapid embryonic mitoses in the C. elegans embryo. Cyclins B1 and B2 support slow mitosis (NEBD to anaphase ∼600 s), but the presence of cyclin B3 dominantly drives the approximately threefold faster mitosis observed in wildtype. Multiple mitotic events are slowed down in cyclin B1 and B2-driven mitosis, and cyclin B3-associated Cdk1 H1 kinase activity is ∼25-fold more active than cyclin B1-associated Cdk1. Addition of cyclin B1 to fast cyclin B3-only mitosis introduces an ∼60-s delay between completion of chromosome alignment and anaphase onset; this delay, which is important for segregation fidelity, is dependent on inhibitory phosphorylation of the anaphase activator Cdc20. Thus, cyclin B3 dominance, coupled to a cyclin B1-dependent delay that acts via Cdc20 phosphorylation, sets the rapid pace and ensures mitotic fidelity in the early C. elegans embryo.
    DOI:  https://doi.org/10.1083/jcb.202308034
  8. Int J Biol Sci. 2024 ;20(10): 3863-3880
    Participation of preovulatory follicles in the activation of primordial follicles in mouse ovaries.
    Jingwen Zhang, Wenzhe Xia, Jiaqi Zhou, Shaogang Qin, Lin Lin, Ting Zhao, Huarong Wang, Chen Mi, Yifan Hu, Zixuan Chen, Tianhua Zhu, Xinyu Yang, Tuo Zhang, Guoliang Xia, Yuwen Ke, Chao Wang.
      The mechanisms behind the selection and initial recruitment of primordial follicles (PmFs) from the non-growing PmF pool during each estrous cycle in females remain largely unknown. This study demonstrates that PmFs closest to the ovulatory follicle are preferentially activated in mouse ovaries under physiological conditions. PmFs located within 40 μm of the ovulatory follicles were more likely to be activated compared to those situated further away during the peri-ovulation period. Repeated superovulation treatments accelerated the depletion of the PmF reserve, whereas continuous suppression of ovulation delayed PmF reserve consumption. Spatial transcriptome sequencing of peri-ovulatory follicles revealed that ovulation primarily induces the degradation and remodeling of the extracellular matrix (ECM). This ECM degradation reduces mechanical stress around PmFs, thereby triggering their activation. Specifically, Cathepsin L (CTSL), a cysteine proteinase and lysosomal enzyme involved in ECM degradation, initiates the activation of PmFs adjacent to ovulatory follicles in a distance-dependent manner. These findings highlight the link between ovulation and selective PmF activation, and underscore the role of CTSL in this process under physiological conditions.
    Keywords:  Cathepsin L.; Ovulation; extracellular matrix; primordial follicle activation
    DOI:  https://doi.org/10.7150/ijbs.95020
  9. Elife. 2024 Aug 08. pii: e80687. [Epub ahead of print]13
    BRCA1/BRC-1 and SMC-5/6 regulate DNA repair pathway engagement during C. elegans meiosis.
    Erik Toraason, Alina Salagean, David E Almanzar, Jordan E Brown, Colette M Richter, Nicole A Kurhanewicz, Ofer Rog, Diana E Libuda.
      The preservation of genome integrity during sperm and egg development is vital for reproductive success. During meiosis, the tumor suppressor BRCA1/BRC-1 and structural maintenance of chromosomes 5/6 (SMC-5/6) complex genetically interact to promote high fidelity DNA double strand break (DSB) repair, but the specific DSB repair outcomes these proteins regulate remain unknown. Using genetic and cytological methods to monitor resolution of DSBs with different repair partners in Caenorhabditis elegans, we demonstrate that both BRC-1 and SMC-5 repress intersister crossover recombination events. Sequencing analysis of conversion tracts from homolog-independent DSB repair events further indicates that BRC-1 regulates intersister/intrachromatid noncrossover conversion tract length. Moreover, we find that BRC-1 specifically inhibits error prone repair of DSBs induced at mid-pachytene. Finally, we reveal functional interactions of BRC-1 and SMC-5/6 in regulating repair pathway engagement: BRC-1 is required for localization of recombinase proteins to DSBs in smc-5 mutants and enhances DSB repair defects in smc-5 mutants by repressing theta-mediated end joining (TMEJ). These results are consistent with a model in which some functions of BRC-1 act upstream of SMC-5/6 to promote recombination and inhibit error-prone DSB repair, while SMC-5/6 acts downstream of BRC-1 to regulate the formation or resolution of recombination intermediates. Taken together, our study illuminates the coordinate interplay of BRC-1 and SMC-5/6 to regulate DSB repair outcomes in the germline.
    Keywords:  C. elegans; chromosomes; gene expression; genetics; genomics
    DOI:  https://doi.org/10.7554/eLife.80687
  10. Autophagy. 2024 Aug 08.
    RAB37-mediated autophagy guards ovarian homeostasis and function.
    Rongjia Zhou, Xu Xu, Mengxin Hu, Ruhong Ying, Juan Zou, Zhuoyue Du, Lan Lin, Tian Lan, Haoyu Wang, Yu Hou, Hanhua Cheng.
      Loss of ovarian homeostasis is associated with ovary dysfunction and female diseases; however, the underlying mechanisms responsible for the establishment of homeostasis and its function in the ovary have not been fully elucidated. Here, we showed that conditional knockout of Rab37 in oocytes impaired macroautophagy/autophagy proficiency in the ovary and interfered with follicular homeostasis and ovary development in mice. Flunarizine treatment upregulated autophagy, thus rescuing the impairment of follicular homeostasis and ovarian dysfunction in rab37 knockout mice by reprogramming of homeostasis. Notably, both the E2F1 and EGR2 transcription factors synergistically activated Rab37 transcription and promoted autophagy. Thus, RAB37-mediated autophagy ensures ovary function by maintaining ovarian homeostasis.
    Keywords:  Gene knockout; RAB37; homeostasis; mice; ovary; transcription regulation
    DOI:  https://doi.org/10.1080/15548627.2024.2389568
  11. Physiology (Bethesda). 2024 Aug 07.
    Mechanical remodeling of nuclear biomolecular condensates.
    Giulia Soggia, Yasmin ElMaghloob, Annie-Kermen Boromangnaeva, Adel Al Jord.
      Organism health relies on cell proliferation, migration, and differentiation. These universal processes depend on cytoplasmic reorganization driven notably by the cytoskeleton and its force-generating motors. Their activity generates forces that mechanically agitate the cell nucleus and its interior. New evidence from reproductive cell biology revealed that these cytoskeletal forces can be tuned to remodel nuclear membrane-less compartments, known as biomolecular condensates, and regulate their RNA processing function for the success of subsequent cell division that is critical for fertility. Both cytoskeletal and nuclear condensate reorganization are common to numerous physiological and pathological contexts, raising the possibility that mechanical remodeling of nuclear condensates may be a much broader mechanism regulating their function. Here, we review this newfound mechanism of condensate remodeling and venture into contexts of health and disease where it may be relevant, with a focus on reproduction, cancer, and premature aging.
    Keywords:  Aging; Biomolecular Condensates; Cancer; Nucleus; Oocytes
    DOI:  https://doi.org/10.1152/physiol.00027.2024
  12. Theriogenology. 2024 Jul 31. pii: S0093-691X(24)00307-8. [Epub ahead of print]228 54-63
    Attenuation of endoplasmic reticulum stress improves invitro growth and subsequent maturation of bovine oocytes.
    Md Nuronnabi Islam, Fumio Ebara, Kokoro Kawasaki, Toshihiro Konno, Hideki Tatemoto, Ken-Ichi Yamanaka.
      Endoplasmic reticulum (ER) stress interferes with developmental processes in oocyte maturation and embryo development. Invitro growth (IVG) is associated with low developmental competence, and ER stress during IVG culture may play a role. Therefore, this study aimed to examine the effect of tauroursodeoxycholic acid (TUDCA), an ER stress inhibitor, on the IVG of bovine oocytes to understand the role of ER stress. Oocyte-granulosa cell complexes (OGCs) were collected from early antral follicles (1.5-1.8 mm) and allowed to grow in vitro for 5 days at 38.5 °C in a humidified atmosphere containing 5 % CO2. Basic growth culture medium was supplemented with TUDCA at various concentrations (0, 50, 100, 250, and 500 μM). After IVG, oocyte diameters were similar among groups, but the antrum formation rate tended to be higher in the TUDCA 100 μM group. The mRNA expression levels of ER stress-associated genes (PERK, ATF6, ATF4, CHOP, BAX, IRE1, and XBP1) in OGCs were downregulated in the TUDCA 100 μM group than those in the control group. Moreover, the TUDCA 100 μM group exhibited reduced ROS production with higher GSH levels and improved in vitro-grown oocyte maturation compared with those in the control group. In contrast, no difference in the developmental competence of embryos following invitro fertilization was observed between the control and TUDCA 100 μM groups. These results indicate that ER stress could impair IVG and subsequent maturation rate of bovine oocytes, and TUDCA could alleviate these detrimental effects. These outcomes might improve the quality of oocytes in IVG culture in assisted reproductive technology.
    Keywords:  Bovine; Endoplasmic reticulum stress; In vitro growth; Oocyte maturation; Tauroursodeoxycholic acid
    DOI:  https://doi.org/10.1016/j.theriogenology.2024.07.027
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