bims-cebooc 2025-03-09 papers

bims-cebooc

Biomed News

on Cell biology of oocytes

Issue of 2025–03–09
twelve papers selected by
Gabriele Zaffagnini, Universität zu Köln

Ovarian tachykinin signaling system induces the growth of secondary follicles during the gonadotropin-independent process.
Aberrant activation of chromosome asynapsis checkpoint triggers oocyte elimination.
NAT10 regulates zygotic genome activation and the morula-to-blastocyst transition.
Meiosis-specific distal cohesion site decoupled from the kinetochore.
Hybrid female sterility due to cohesin protection errors in oocytes.
Multi-Omics Reveal the Metabolic Changes in Cumulus Cells During Aging.
Formation of Drosophila germ cells requires spatial patterning of phospholipids.
Complementary Volume Electron Microscopy-based approaches reveal ultrastructural changes in germline intercellular bridges of D. melanogaster.
Dux cluster duplication ensures full activation of totipotent genes.
Allosteric inhibition of the IZUMO1-JUNO fertilization complex by the naturally occurring antisperm antibody OBF13.
Smooth endoplasmic reticulum aggregates in human oocytes are related to female infertility etiology and diminished reproductive outcomes.
Reproductive Adaptation of Astyanax mexicanus Under Nutrient Limitation.

J Biol Chem. 2025 Mar 03. pii: S0021-9258(25)00224-8. [Epub ahead of print] 108375

Ovarian tachykinin signaling system induces the growth of secondary follicles during the gonadotropin-independent process.

Tsuyoshi Kawada, Masato Aoyama, Shin Matsubara, Tomohiro Osugi, Tsubasa Sakai, Shinji Kirimoto, Satsuki Nakaoka, Yuki Sugiura, Keiko Yasuda, Honoo Satake.

  Mammalian follicle growth development is mainly regulated by the hypothalamus-pituitary-gonadal (HPG) axis after puberty. Although pituitary hormones, gonadotropins, are involved in HPG axis signaling, they are not responsible for the growth of early-stage follicles, namely, primordial follicles, primary follicles, and secondary follicles, in both sexually immature and mature individuals. Unlike those of gonadotropin-dependent follicle growth, the specific regulatory factors of gonadotropin-independent follicle growth have yet to be identified. Here, we identified tachykinins (TKs) as inducers of gonadotropin-independent secondary follicle growth. TKs play various roles as neuropeptides or hormones in a wide variety of biological events both in the central nervous system and in peripheral tissues, but a direct effect of TKs on ovarian follicles has yet to investigated. Follicle development was suppressed in sexually immature 3-week-old knockout mice of Tac1 gene encoding TKs (substance P and neurokinin A), which is independent of gonadotropins. TKs and their receptors are specifically localized to granulosa cells in mouse secondary follicles. Furthermore, TKs upregulate the prostaglandin (PG) synthase COX-2 via the JAK1-STAT3 signaling cascade. We also demonstrated that PGE2 and PGF2α are major PGs in the immature ovary, and the secondary follicle growth was enhanced by interaction between PGE2 / PGF2α and their receptors, PGE2 receptor (EP2) localized in the oocyte membrane and PGF2α receptor (FP) localized in the oocyte membrane, the granulosa cells, and theca cells. Consequently, this study paves the way for exploring gonadotropin-independent early-stage follicle growth systems and relevant dysfunctions, including pediatric endocrinological diseases.

Keywords:  mouse; ovary; peptide hormone; prostaglandin; receptor; secondary follicle; tachykinin

DOI:  https://doi.org/10.1016/j.jbc.2025.108375
Nat Commun. 2025 Mar 06. 16(1): 2260

Aberrant activation of chromosome asynapsis checkpoint triggers oocyte elimination.

Xiaofei Jiao, Zhongyang Liang, Jiwei Li, Long Bai, Jun Xu, Yidan Liu, Lin-Yu Lu.

Chromosome synapsis is an evolutionarily conserved process essential for meiotic recombination. HORMAD1 and HORMAD2, which monitor chromosome asynapsis by localizing to unsynapsed chromosome axes, are removed from synapsed chromosome axes by TRIP13, though the biological significance of this process remains unclear. We show that when HORMAD1 and HORMAD2 are retained on synapsed chromosome axes, they recruit BRCA1, activate chromosome asynapsis checkpoint, and trigger oocyte elimination. Unexpectedly, N-terminal tagging retains HORMAD1 and HORMAD2 on synapsed chromosome axes without triggering oocyte elimination due to defective BRCA1 recruitment. Mechanistically, HORMAD1 co-immunoprecipitates with BRCA1 readily, not through the canonical closure motif-binding mode but via an interface on its HORMA domain near the N-terminus. HORMAD2 co-immunoprecipitates with BRCA1 weakly but also regulates its recruitment. Collectively, the TRIP13-dependent removal of HORMAD1 and HORMAD2 from synapsed chromosome axes is essential for female fertility, preventing aberrant chromosome asynapsis checkpoint activation and unintended oocyte elimination.

DOI: https://doi.org/10.1038/s41467-025-57702-z
FASEB J. 2025 Mar 15. 39(5): e70444

NAT10 regulates zygotic genome activation and the morula-to-blastocyst transition.

Zhi Cui, Cong Fu, Di Ai, Haibo Zhu, Fang Wang, Xinglan An, Ziyi Li, Sheng Zhang.

  As the first acetylated nucleoside to be discovered, N-acetyltransferase 10 (NAT10)-catalyzed RNA N4-acetylcytidine (ac4C) modification is involved in the occurrence of various diseases. However, the roles of RNA ac4C in preimplantation embryo development still need more detailed studies. Here, we analyzed the role of RNA ac4C in preimplanted embryonic development in mice through Nat10 siRNA microinjection and growing oocyte stage-specific Nat10 knockout (Zp3-Nat10lox/lox). We found that NAT10 was indispensable for both the morula-to-blastocyst transition and zygotic genome activation (ZGA). Nat10 knockdown by Nat10 siRNA microinjection caused most embryos to arrest at the morula stage, and the expression levels of NANOG and CDX2 were significantly decreased. Moreover, the mRNA stability of Nanog was also significantly decreased in morulae after Nat10 knockdown. Zp3-Nat10lox/lox female mice were completely sterile, and the embryos from Zp3-Nat10lox/lox females were arrested at the 2-cell stage. Both the degradation of maternal mRNA and ZGA were deficient in 2-cell embryos from Zp3-Nat10lox/lox females. In conclusion, our findings demonstrate that NAT10 is crucial for both ZGA and the morula-to-blastocyst transition processes during mouse preimplantation embryonic development.

Keywords:  NAT10; RNA N4‐acetylcytidine; embryonic development; mice; zygotic genome activation

DOI:  https://doi.org/10.1096/fj.202402751R
Nat Commun. 2025 Mar 03. 16(1): 2116

Meiosis-specific distal cohesion site decoupled from the kinetochore.

Bo Pan, Melania Bruno, Todd S Macfarlan, Takashi Akera.

Primary constriction of the M-phase chromosome serves as a marker for the kinetochore position. Underlying this observation is the concept that the kinetochore is spatially linked with the pericentromere where sister-chromatids are cohered. Here, we find an unconventional chromatid-cohesion pattern in Peromyscus oocytes, with sister chromatids cohered at a chromosome end, spatially separated from the kinetochore. This distal locus enriches cohesin protectors specifically during meiosis, and chromosomes with this additional cohesion site exhibit enhanced cohesin protection at anaphase I compared to those without it, implying an adaptive evolution to ensure cohesion during meiosis. The distal locus corresponds to an additional centromeric satellite block, located far from the satellite block building the kinetochore. Analyses on three Peromyscus species reveal that the internal satellite consistently assembles the kinetochore in mitosis and meiosis, whereas the distal satellite selectively enriches cohesin protectors in meiosis to promote cohesion. Our study demonstrates that cohesion regulation is flexible, controlling chromosome segregation in a cell-type dependent manner.

DOI: https://doi.org/10.1038/s41467-025-57438-w
bioRxiv. 2025 Feb 17. pii: 2025.02.16.638358. [Epub ahead of print]

Hybrid female sterility due to cohesin protection errors in oocytes.

Warif El Yakoubi, Bo Pan, Takashi Akera.

Hybrid incompatibility can lead to lethality and sterility of F1 hybrids, contributing to speciation. Here we found that female hybrids between Mus musculus domesticus and Mus spicilegus mice are sterile due to the failure of homologous chromosome separation in oocyte meiosis I, producing aneuploid eggs. This non-separation phenotype was driven by the mis- localization of the cohesin protector, SGO2, along the chromosome arms instead of its typical centromeric enrichment, resulting in cohesin over-protection. The upstream kinase, BUB1, showed a significantly higher activity in hybrid oocytes, explaining SGO2 mis-targeting along the chromosome arm. Higher BUB1 activity was not observed in mitosis, consistent with viable hybrid mice. Cohesion defects were also evident in hybrid mice from another genus, Peromyscus , wherein cohesin protection is weakened. Defective cohesion in oocytes is a leading cause of reduced fertility especially with advanced maternal age. Our work provides evidence that a major cause of human infertility may play a positive role in promoting mammalian speciation.

DOI: https://doi.org/10.1101/2025.02.16.638358
Cell Prolif. 2025 Mar 05. e70014

Multi-Omics Reveal the Metabolic Changes in Cumulus Cells During Aging.

Liangyue Shi, Hengjie Wang, Shuai Zhu, Minjian Chen, Xuejiang Guo, Qiang Wang, Ling Gu.

  Maternal age has been reported to impair oocyte quality. However, the molecular mechanisms underlying the age-related decrease in oocyte competence remain poorly understood. Cumulus cells establish direct contact with the oocyte through gap junctions, facilitating the provision of crucial nutrients necessary for oocyte development. In this study, we obtained the proteomic and metabolomic profiles of cumulus cells from both young and old mice. We found that fatty acid beta-oxidation and nucleotide metabolism, markedly active in aged cumulus cells, may serve as a compensatory mechanism for energy provision. Tryptophan undergoes two principal metabolic pathways, including the serotonin (5-HT) synthesis and kynurenine catabolism. Notably, we discovered that kynurenine catabolism is reduced in aged cumulus cells compared to young cells, whereas 5-HT synthesis exhibited a significant decrease. Furthermore, the supplement of 5-HT during cumulus-oocyte complexes (COCs) culture significantly ameliorated the metabolic dysfunction and meiotic defects in old oocytes. In sum, our data provide a comprehensive multiple omics resource, offering potential insights for improving oocyte quality and promoting fertility in aged females.

Keywords:  aging; cumulus cells; metabolomics; oocyte; proteomic

DOI:  https://doi.org/10.1111/cpr.70014
Curr Biol. 2025 Mar 03. pii: S0960-9822(25)00134-4. [Epub ahead of print]

Formation of Drosophila germ cells requires spatial patterning of phospholipids.

Marcus D Kilwein, Pearson Miller, Kwan Yin Lee, Miriam Osterfield, Alex Mogilner, Stanislav Y Shvartsman, Elizabeth R Gavis.

  Germline-soma segregation is crucial for fertility. Primordial germ cells (PGCs) arise early in development and are the very first cells to form in the Drosophila embryo. At the time of PGC formation, the embryo is a syncytium where nuclei divide within a common cytoplasm. Whereas invaginating plasma membrane furrows enclose nuclei to form somatic lineages during the 14th nuclear division cycle, PGCs emerge from the syncytium during the 9th division cycle in a mechanistically distinct process. PGC formation depends on maternally deposited germ granules localized at the embryo's posterior pole. Germ granules trigger protrusion of membrane buds that enlarge to surround several nuclei that reach the posterior pole. Buds are remodeled to cells through mitotic division and constriction of the bud neck. Previous studies implicated F-actin,1 actin regulators,2,3 and contractile ring components4 in mitotic furrow formation, but what drives bud emergence and how germ granules provoke reshaping of the plasma membrane remain unknown. Here, we investigate the mechanism of germ-granule-induced bud formation. Treating the embryo as a pressurized elastic shell, we used mathematical modeling to examine possible mechanical mechanisms for local membrane protrusion. One mechanism, outward buckling produced by polymerization of a branched F-actin network, is supported by experimental data. Further, we show that germ granules modify membrane lipid composition, promoting local branched F-actin polymerization that initiates PGC formation. We propose that a mechanism for membrane lipid regulation of F-actin dynamics in migrating cells has been adapted for PGC formation in response to spatial cues provided by germ granules.

Keywords:  Drosophila; PI4Kα; PIP2; germ granules; germline; primordial germ cells

DOI:  https://doi.org/10.1016/j.cub.2025.01.071
bioRxiv. 2025 Feb 23. pii: 2025.02.18.638836. [Epub ahead of print]

Complementary Volume Electron Microscopy-based approaches reveal ultrastructural changes in germline intercellular bridges of D. melanogaster.

Irina Kolotuev, Abigayle Williams, Caroline Kizilyaprak, Stephanie Pellegrino, Lindsay Lewellyn.

Intercellular bridges are essential to connect developing germline cells. The Drosophila melanogaster egg chamber is a powerful model system to study germline intercellular bridges, or ring canals (RCs). RCs connect the developing oocyte to supporting nurse cells, and defects in their stability or growth lead to infertility. Despite their importance, it has been technically difficult to use electron microscopy-based approaches to monitor changes in RC structure during oogenesis. Here, we describe the application of a complementary set of volume EM-based approaches to visualize ultrastructural changes in the germline RCs. The combination of array tomography (AT) and focused ion beam (FIB) scanning electron microscopy (SEM) has allowed us to gain insight into previously unappreciated aspects of RC structure. We were able to quantify differences in RC size and thickness within and between germ cell clusters at different developmental stages. Within a cluster, RC size correlates with lineage; the largest RCs were formed during the first division, and the smallest RCs were formed during the fourth mitotic division. We observed the formation of membrane interdigitations in the vicinity of RCs much earlier than previously reported, and reconstruction of a RC from a mid-stage EC provided insight into the 3D orientation of these extensive cell-cell contacts. Our imaging also revealed a novel membrane structure that appeared to line the interior of the RC lumen. Although the focus was on ultrastructural changes in the germline RCs, our dataset contains valuable details of additional cell types and structures, including the fusome, the germline stem cells and their niche, and the migrating border cells. This imaging framework could be applied to other tissues or samples that face similar technical challenges, where the small structure of interest is located within a large sample volume.

DOI: https://doi.org/10.1101/2025.02.18.638836
Proc Natl Acad Sci U S A. 2025 Mar 11. 122(10): e2421594122

Dux cluster duplication ensures full activation of totipotent genes.

Meiqi Lin, Zeling Du, Dan Guo, Yiran Zhang, Jiameng Dan.

  Zygotic genome activation (ZGA) confers to the mouse two-cell (2C) embryo a unique transcriptional profile characterized by transient up-regulation of many totipotency-related genes and MERVL retrotransposons. Intriguingly, those genes are duplicated and clustered in the genome during evolution, including Dux cluster, Obox, and Zscan4 family members in mice. However, the contribution and biological significance of the totipotency-related gene duplication events in early embryo development remain poorly understood. Here, we focus on Dux cluster, the master regulator of ZGA that is necessary and sufficient for the induction of 2C-like cells and activation of totipotency-related genes in mouse embryonic stem cells (mESCs). By reducing Dux gene copies from 31 to 0 or 1 through CRISPR-Cas9 technology, we generate Dux-KO and Dux (n = 1) mESC lines, respectively. We uncover that the totipotency-related gene transcriptional profile is awakened to a much lesser extent in Dux (n = 1) mESCs compared to wild type mESCs following global DNA demethylation reprogramming or induction of DNA damage, mimicking the intrinsic events in preimplantation development. Together, Dux cluster duplication is critically required for full activation of ZGA transcripts.

Keywords:  2C-like state; Dux cluster duplication; totipotency; zygotic genome activation

DOI:  https://doi.org/10.1073/pnas.2421594122
Proc Natl Acad Sci U S A. 2025 Mar 11. 122(10): e2425952122

Allosteric inhibition of the IZUMO1-JUNO fertilization complex by the naturally occurring antisperm antibody OBF13.

Yonggang Lu, Masahito Ikawa, Shaogeng Tang.

  Sperm IZUMO1 binds to egg JUNO, and this interaction is essential for mammalian fertilization. Isolated from a female mouse immunized with syngeneic sperm, the antisperm antibody OBF13 recognizes IZUMO1 and inhibits murine fertilization. How OBF13 interferes with sperm-egg interactions was unknown. Here, we present the X-ray crystal structure of IZUMO1 in complex with OBF13. OBF13 binds to the apex of the four-helix domain of IZUMO1, distant from the JUNO-binding site. Our crystal structure of OBF13-bound IZUMO1 resembles apo-IZUMO1 and differs from the structure of IZUMO1 in complex with JUNO. We identify that OBF13 carries a low level of somatic hypermutation, and through deep mutational scanning, we engineer an affinity-enhanced OBF13 variant. This OBF13 variant single-chain fragment variable decreases the apparent affinity of IZUMO1 for membrane-bound murine JUNO and blocks the binding of acrosome-reacted sperm to eggs, thereby preventing fertilization. We propose allostery between the OBF13 epitope and the JUNO-binding site. OBF13 inhibits a conformational change in IZUMO1, preventing fusion-competent sperm from adhering to murine eggs during fertilization. Surprisingly, murine IZUMO1 binds to hamster JUNO with an affinity ~20-fold higher than to murine JUNO. The decreased affinity caused by OBF13 of murine IZUMO1 for hamster JUNO is sufficient for murine sperm to bind to and fuse with hamster eggs. Our studies provide a structural and mechanistic framework for species-specific, allosteric inhibition of IZUMO1 by a naturally occurring antisperm antibody and offer insights into the development of immunocontraceptives.

Keywords:  IZUMO1; antisperm antibody; contraception; fertilization; infertility

DOI:  https://doi.org/10.1073/pnas.2425952122
Sci Rep. 2025 Feb 28. 15(1): 7160

Smooth endoplasmic reticulum aggregates in human oocytes are related to female infertility etiology and diminished reproductive outcomes.

Nasrin Ghanami Gashti, Seyedeh Zahra Hosseini, Maryam Qasemi, Roya Kabodmehri, Ziba Zahiri Sorouri, Mohammad Hadi Bahadori.

  Smooth endoplasmic reticulum aggregates (SERa) are a type of dysmorphism in oocytes derived from controlled ovarian stimulation (COS). The effect of SERa on assisted reproductive techniques (ART) outcomes is debatable. Based on some evidence, SERa-positive (SERa+) oocytes cause complications including newborn demise, and compromise the outcome of the unaffected oocytes of the same cycle. While other reports demonstrated equal developmental competence between SERa + and SERa-negative (SERa-) oocytes/cycles. We conducted a prospective cross-sectional study on 315 women candidates for ART and compared the outcome among SERa+ (N = 73) and SERa- cycles (N = 217). Furthermore, for the first time, we investigated the prevalence of SERa + cycles in women with various infertility etiologies. Our results indicated that SERa + patients presented higher levels of Estradiol on the day of ovulation triggering (p = 0.02). Regarding the ART outcome, there were no differences in the number of retrieved oocytes, oocyte maturation and fertilization rates among the groups. However, the quality of the unaffected oocytes (p = 0.03), the rates of day-3 top-quality embryos (p = 0.01, and p = 0.03 for grades A and B, respectively), and clinical pregnancy (p = 0.05) in SERa + group were significantly reduced. Moreover, the prevalence of SERa + cycles gradually increased among endometriosis, POI/POR, PCOS, normal women, tubal factor, and idiopathic groups. Our study suggests that suboptimal situations such as elevated levels of Estradiol can increase the occurrence of SERa + oocytes. This suboptimal phenomenon can negatively influence the outcome of the cycle. Thus, optimization of COS, particularly in vulnerable groups such as women with idiopathic infertility may lower the SERa + cycle occurrence, improving the ART outcome.

Keywords:  ART outcome.; Assisted reproductive techniques; Infertility; Oocyte; Smooth endoplasmic reticulum aggregates

DOI:  https://doi.org/10.1038/s41598-024-78366-7
bioRxiv. 2025 Feb 17. pii: 2025.02.13.638191. [Epub ahead of print]

Reproductive Adaptation of Astyanax mexicanus Under Nutrient Limitation.

Fanning Xia, Ana Santacruz, Di Wu, Sylvain Bertho, Elizabeth Fritz, Pedro Morales-Sosa, Sean McKinney, Stephanie H Nowotarski, Nicolas Rohner.

Reproduction is a fundamental biological process for the survival and continuity of species. Examining changes in reproductive strategies offers valuable insights into how animals have adapted their life histories to different environments. Since reproduction is one of the most energy-intensive processes in female animals, nutrient scarcity is expected to interfere with the ability to invest in gametes. Lately, a new model to study adaptation to nutrient limitation has emerged; the Mexican tetra Astyanax mexicanus . This fish species exists as two different morphs, a surface river morph and a cave-dwelling morph. The cave-dwelling morph has adapted to the dark, biodiversity, and nutrient-limited cave environment and consequently evolved an impressive starvation resistance. However, how reproductive strategies have adapted to nutrient limitations in this species remains poorly understood. Here, we compared breeding activities and maternal contributions between laboratory-raised surface fish and cavefish. We found that cavefish produce different clutch sizes of eggs with larger yolk compared to surface fish, indicating a greater maternal nutrient deposition in cavefish embryos. To systematically characterize yolk compositions, we used untargeted proteomics and lipidomics approaches to analyze protein and lipid profiles in 2-cell stage embryos and found an increased proportion of sphingolipids in cavefish compared to surface fish. Additionally, we generated transcriptomic profiles of surface fish and cavefish ovaries using a combination of single cell and bulk RNA sequencing to examine differences in maternal contribution. We found that genes essential for hormone regulation were upregulated in cavefish follicular somatic cells compared to surface fish. To evaluate whether these differences contribute to their reproductive abilities under natural-occurring stress, we induced breeding in starved female fish. Remarkably, cavefish maintained their ability to breed under starvation, whereas surface fish largely lost this ability. We identified insulin-like growth factor 1a receptor ( igf1ra ) as a potential candidate gene mediating the downregulation of ovarian development genes, potentially contributing to the starvation-resistant fertility of cavefish. Taken together, we investigated the female reproductive strategies in Astyanax mexicanus , which will provide fundamental insights into the adaptations of animals to environments with extreme nutrient deficit.

DOI: https://doi.org/10.1101/2025.02.13.638191