bims-cebooc 2025-03-23 papers

bims-cebooc

Biomed News

on Cell biology of oocytes

Issue of 2025–03–23
thirteen papers selected by
Gabriele Zaffagnini, Universität zu Köln

SnapShot: Human sperm-egg interface proteins.
The autophagy protein ATG14 safeguards against unscheduled pyroptosis activation to enable embryo transport during early pregnancy.
Rediscovering the rete ovarii, a secreting auxiliary structure to the ovary.
Polarization-independent regulation of the subcellular localization of Yes-associated protein 1 during preimplantation development.
Endosomal-lysosomal organellar assembly (ELYSA) structures coordinate lysosomal degradation systems through mammalian oocyte-to-embryo transition.
Protein-targeting reverse genetic approaches: the future of oocyte and preimplantation embryo research.
Autonomous follicle quality control mechanisms: Innate immune signaling capabilities of granulosa cells.
Mitofusin 1 Drives Preimplantation Development by Enhancing Chromatin Incorporation of Histone H3.3.
Regulation of Female Reproductive Aging by the Spag17 Gene.
Ultrastructure assessment of oocyte from mouse with polycystic ovary syndrome following cryopreservation.
FSP1 regulates ferroptosis and mitochondrial function during mouse oocyte maturation.
Ovarian aging-associated downregulation of GPX4 expression regulates ovarian follicular development by affecting granulosa cell functions and oocyte quality.
GPD1L-Mediated Glycerophospholipid Metabolism Dysfunction in Women With Diminished Ovarian Reserve: Insights From Pseudotargeted Metabolomic Analysis of Follicular Fluid.

Cell. 2025 Mar 20. pii: S0092-8674(25)00001-7. [Epub ahead of print]188(6): 1746-1746.e1

SnapShot: Human sperm-egg interface proteins.

Emily Forster, Xinyin Wang, Abenan Thayaparan, Jeffrey E Lee.

Human fertilization is a complex, highly regulated process that involves intricate molecular interactions between sperm and egg. Ultimately, this process culminates in the fusion of the gamete membranes to form a zygote. Gene disruption studies in mice have identified several critical fertilization factors. This SnapShot highlights the structure function of key proteins at the sperm-egg interface, providing insights into the mechanism of fertilization. To view this SnapShot, open or download the PDF.

DOI: https://doi.org/10.1016/j.cell.2025.01.001
Elife. 2025 Mar 18. pii: RP97325. [Epub ahead of print]13

The autophagy protein ATG14 safeguards against unscheduled pyroptosis activation to enable embryo transport during early pregnancy.

Pooja Popli, Arin K Oestreich, Vineet K Maurya, Marina N Rowen, Yong Zhang, Michael J Holtzman, Ramya Masand, John P Lydon, Shizuo Akira, Kelle Moley, Ramakrishna Kommagani.

  Recurrent pregnancy loss, characterized by two or more failed clinical pregnancies, poses a significant challenge to reproductive health. In addition to embryo quality and endometrial function, proper oviduct function is also essential for successful pregnancy establishment. Therefore, structural abnormalities or inflammation resulting from infection in the oviduct may impede the transport of embryos to the endometrium, thereby increasing the risk of miscarriage. However, our understanding of the biological processes that preserve the oviductal cellular structure and functional integrity is limited. Here, we report that autophagy-related protein ATG14 plays a crucial role in maintaining the cellular integrity of the oviduct by controlling inflammatory responses, thereby supporting efficient embryo transport. Specifically, the conditional depletion of the autophagy-related gene Atg14 in the oviduct causes severe structural abnormalities compromising its cellular integrity, leading to the abnormal retention of embryos. Interestingly, the selective loss of Atg14 in oviduct ciliary epithelial cells did not impact female fertility, highlighting the specificity of ATG14 function in distinct cell types within the oviduct. Mechanistically, loss of Atg14 triggered unscheduled pyroptosis via altering the mitochondrial integrity, leading to inappropriate embryo retention and impeded embryo transport in the oviduct. Finally, pharmacological activation of pyroptosis in pregnant mice phenocopied the genetically induced defect and caused impairment in embryo transport. Together, we found that ATG14 safeguards against unscheduled pyroptosis activation to enable embryo transport from the oviduct to uterus for the successful implantation. Of clinical significance, these findings provide possible insights into the underlying mechanism(s) of early pregnancy loss and might aid in developing novel prevention strategies using autophagy modulators.

Keywords:  Atg14; autophagy; developmental biology; inflammation; mouse; oviduct; pregnancy

DOI:  https://doi.org/10.7554/eLife.97325
Elife. 2025 Mar 19. pii: RP96662. [Epub ahead of print]13

Rediscovering the rete ovarii, a secreting auxiliary structure to the ovary.

Dilara N Anbarci, Jennifer McKey, Daniel S Levic, Michel Bagnat, Blanche Capel.

  The rete ovarii (RO) is an appendage of the ovary that has been given little attention. Although the RO appears in drawings of the ovary in early versions of Gray's Anatomy, it disappeared from recent textbooks, and is often dismissed as a functionless vestige in the adult ovary. Using PAX8 immunostaining and confocal microscopy, we characterized the fetal development of the RO in the context of the mouse ovary. The RO consists of three distinct regions that persist in adult life, the intraovarian rete (IOR), the extraovarian rete (EOR), and the connecting rete (CR). While the cells of the IOR appear to form solid cords within the ovary, the EOR rapidly develops into a convoluted tubular epithelium ending in a distal dilated tip. Cells of the EOR are ciliated and exhibit cellular trafficking capabilities. The CR, connecting the EOR to the IOR, gradually acquires tubular epithelial characteristics by birth. Using microinjections into the distal dilated tip of the EOR, we found that luminal contents flow toward the ovary. Mass spectrometry revealed that the EOR lumen contains secreted proteins potentially important for ovarian function. We show that the cells of the EOR are closely associated with vasculature and macrophages, and are contacted by neuronal projections, consistent with a role as a sensory appendage of the ovary. The direct proximity of the RO to the ovary and its integration with the extraovarian landscape suggest that it plays an important role in ovary development and homeostasis.

Keywords:  SNARE complex; cell biology; developmental biology; fluid secretion; mouse; ovary; proteomics; rete ovarii

DOI:  https://doi.org/10.7554/eLife.96662
J Biol Chem. 2025 Mar 19. pii: S0021-9258(25)00278-9. [Epub ahead of print] 108429

Polarization-independent regulation of the subcellular localization of Yes-associated protein 1 during preimplantation development.

Shun Saito, Koji Nishiyama, Hanako Bai, Masashi Takahashi, Manabu Kawahara.

  Cell polarization is a crucial developmental process that determines cell differentiation in mouse embryos. During this process, an extensively expressed transcriptional regulator, Yes-associated protein 1 (YAP1), is localized either to the cytoplasm or nucleus via HIPPO signaling. In mouse pre-morula embryos, YAP1 is present in the nuclei of all cells. Thereafter, YAP1 is distributed to the nuclei of outer cells or cytoplasm of inner cells, depending on the establishment of cell polarity and morula formation. However, the dynamics of YAP1 localization in other species, including ruminants, remain unclear. To gain an in-depth understanding of cell differentiation in mammalian embryos, we investigated YAP1 localization changes in bovine embryos. Unlike in mouse morulae, YAP1 displayed cytoplasmic localization in most cells, including the outer cells of bovine morulae, after the 32-cell stage. Next, we analyzed the relationship between cell polarity and nuclear localization of YAP1. Polarization of outer cells in the bovine morula began at the late 16-cell stage and was established by the late 32-cell stage, indicating that polarization preceded the nuclear localization of YAP1 in bovine embryos. To explore the regulation of YAP1 localization in bovine morula, we analyzed zona-free embryos and found that the presence of the zona pellucida significantly enhanced YAP1 cytoplasmic localization. Moreover, we observed ectopic expression of SOX2 in zona-free blastocysts, which indicated that cytoplasmic localization of YAP1 was associated with the suppression of pluripotency in the trophectoderm. These findings provide valuable insights into the molecular mechanisms underlying the first cell differentiation in mammalian embryos.

Keywords:  Hippo pathway; Yes-associated protein 1 (YAP1); cattle; cell differentiation; cell polarity; morula; preimplantation; zona pellucida

DOI:  https://doi.org/10.1016/j.jbc.2025.108429
Elife. 2025 Mar 17. pii: RP99358. [Epub ahead of print]13

Endosomal-lysosomal organellar assembly (ELYSA) structures coordinate lysosomal degradation systems through mammalian oocyte-to-embryo transition.

Yuhkoh Satouh, Takaki Tatebe, Isei Tanida, Junji Yamaguchi, Yasuo Uchiyama, Ken Sato.

  Mouse oocytes undergo drastic changes in organellar composition and their activities during maturation from the germinal vesicle (GV) to metaphase II (MII) stage. After fertilization, the embryo degrades parts of the maternal components via lysosomal degradation systems, including autophagy and endocytosis, as zygotic gene expression begins during embryogenesis. Here, we demonstrate that endosomal-lysosomal organelles form large spherical assembly structures, termed endosomal-lysosomal organellar assemblies (ELYSAs), in mouse oocytes. ELYSAs are observed in GV oocytes, attaining sizes up to 7-8 μm in diameter in MII oocytes. ELYSAs comprise tubular-vesicular structures containing endosomes and lysosomes along with cytosolic components. Most ELYSAs are also positive for an autophagy regulator, LC3. These characteristics of ELYSA resemble those of ELVA (endolysosomal vesicular assemblies) identified independently. The signals of V1-subunit of vacuolar ATPase tends to be detected on the periphery of ELYSAs in MII oocytes. After fertilization, the localization of the V1-subunit on endosomes and lysosomes increase as ELYSAs gradually disassemble at the 2-cell stage, leading to further acidification of endosomal-lysosomal organelles. These findings suggest that the ELYSA/ELVA maintain endosomal-lysosomal activity in a static state in oocytes for timely activation during early development.

Keywords:  cell biology; developmental biology; endosome; lysosomal maturation; mouse; oocyte activation; oocyte dormancy; ubiquitination; vacuolar ATPase

DOI:  https://doi.org/10.7554/eLife.99358
Mol Hum Reprod. 2025 Mar 18. pii: gaaf008. [Epub ahead of print]

Protein-targeting reverse genetic approaches: the future of oocyte and preimplantation embryo research.

Nicole J Camlin.

  Reverse genetic approaches are the standard in molecular biology to determine a protein's function. Traditionally, nucleic acid targeting via gene knockout (DNA) and knockdown (RNA) has been the method of choice to remove proteins-of-interest. However, the nature of mammalian oocyte maturation and preimplantation embryo development can make nucleic acid targeting approaches difficult. Gene knockout allows time for compensatory mechanisms and secondary phenotypes to develop which can make interpretation of a protein's function difficult. Furthermore, genes can be essential for animal and/or oocyte survival, and therefore, gene knockout is not always a viable approach to investigate oocyte maturation and preimplantation embryo development. Conversely, RNA-targeting approaches, ie RNA interference (RNAi) and morpholinos, rely on protein half-life and therefore are unable to knockdown every protein-of-interest. An increasing number of reverse genetic approaches that directly target proteins have been developed to overcome the limitations of nucleic acid-based approaches, including Trim-Away and auxin-inducible degradation. These protein-targeting approaches give researchers exquisite and fast control of protein loss. This review will discuss how Trim-Away and auxin-inducible degradation can overcome many of the challenges of nucleic acid based reverse genetic approaches. Furthermore, it highlights the unique research opportunities these approaches afford, such as targeting post-translationally modified proteins.

Keywords:  Knockdown; Trim-away; auxin-inducible degradation; knockout; meiosis; oocyte; preimplantation embryo

DOI:  https://doi.org/10.1093/molehr/gaaf008
Reproduction. 2025 Mar 01. pii: REP-25-0042. [Epub ahead of print]

Autonomous follicle quality control mechanisms: Innate immune signaling capabilities of granulosa cells.

Prianka H Hashim, Madeline J Perry, Michele T Pritchard, Jennifer L Gerton, Francesca E Duncan.

We synthesize current evidence that granulosa cells possess unique innate immune signaling capabilities. We suggest the novel concept that this serves as a quality control surveillance mechanism by integrating signals from the oocyte and ovarian microenvironment to prevent poor-quality follicles from producing gametes that contribute to the next generation.

DOI: https://doi.org/10.1530/REP-25-0042
Adv Sci (Weinh). 2025 Mar 16. e2414985

Mitofusin 1 Drives Preimplantation Development by Enhancing Chromatin Incorporation of Histone H3.3.

Xiao-Yan Shi, Yu Tian, Yu-Fan Wang, Yi-Ran Zhang, Ying Yin, Qing Tian, Lei Li, Bing-Xin Ma, Ximiao He, Li-Quan Zhou.

  Mitofusin 1 (MFN1) plays a crucial role in mitochondrial fusion and oocyte development. However, its function in preimplantation embryonic development and its potential involvement in epigenetic regulation remain poorly understood. In this study, it is shown that MFN1 interacts with PADI6, a key component of the cytoplasmic lattice in oocytes and early embryos. MFN1 deficiency in mice results in reduced PADI6 levels and decreased expression of translational machinery components, which suppress protein synthesis activity and lower histone H3.3 abundance. These disruptions lead to the failure of male pronucleus formation, aberrant zygotic genome activation, and impaired embryonic development. It is further demonstrated that the MFN1 activator S89 promotes H3.3 incorporation and rescues early development in maternally aged embryos with low MFN1 levels. Additionally, a positive correlation between MFN1 and H3.3 protein levels in early human embryos is observed. Together, these findings provide new insights into MFN1's role in regulating epigenetic reprogramming during preimplantation embryo development.

Keywords:  H3.3; MFN1; cytoplasmic lattice; preimplantation; zygotic genome activation

DOI:  https://doi.org/10.1002/advs.202414985
bioRxiv. 2025 Mar 03. pii: 2025.03.01.640648. [Epub ahead of print]

Regulation of Female Reproductive Aging by the Spag17 Gene.

Valerie Ericsson, Madisyn Elam, Paulene Sapao, Le My Tu Nguyen, Mary Ellen Gill, Saikeerthana Chodavarapu, Carlos Córdova-Fletes, Audrey Lafrenaye, Sonia Hassan, Mala Mahendroo, Li Chen, Mathieu Petitjean, Jerome F Strauss, John Varga, Francesca E Duncan, Maria E Teves.

Reproductive aging in females is characterized by a decline in oocyte quantity and quality, as well as uterine and cervical dysfunction that contributes to infertility and pregnancy complications. To investigate mechanisms underlying reproductive aging, we explored the contribution of Spag17 , a cilia-related gene associated with tissue homeostasis and fibrosis. Spag17 was expressed throughout the female reproductive tract; however, its expression declined with age in ovarian tissue, while high expression levels were observed in the cervix of young females during cervical tissue remodeling in the pre- and post-parturition periods. Loss of Spag17 in mice resulted in impaired fertility, obstructed labor, and maternal death. This phenotype was associated with accelerated ovarian aging, increased fibrosis, and cervical stiffness, further complicating parturition. At the molecular level, Spag17 loss activated key aging-associated pathways, including proinflammatory, profibrotic, and senescence signaling, suggesting that SPAG17 may be a critical player in female reproductive aging.
TEASER: Spag17 is a key modulator of female reproductive aging.

DOI: https://doi.org/10.1101/2025.03.01.640648
Cryo Letters. 2025 Mar-Apr;46(2):46(2): 116-125

Ultrastructure assessment of oocyte from mouse with polycystic ovary syndrome following cryopreservation.

S Afzalnia, F Ghasemian, H S Maryan, T Mirzapour.

BACKGROUND: The polycystic ovary syndrome (PCOS) is a substantial obstacle to female fertility due to ovulation inhibition. Oocyte cryopreservation is crucial for preserving fertility in women with fertility-compromising disorders such as PCOS.
OBJECTIVE: In this study, the ultrastructural damages of oocytes were evaluated following freezing from PCOS mouse model.
MATERIALS AND METHODS: This experimental study was conducted on 30 adult NMRI mouse. The study comprised three groups: 1) unfrozen PCOS oocytes; 2) vitrified-thawed control oocytes; and 3) vitrified-thawed PCOS oocytes. Transmission electron microscopy was employed for ultrastructure examination across all groups. Moreover, the expression of apoptotic genes, including BAX and Bcl2, was assessed using real time-quantitative polymerase chain reaction (RT-PCR).
RESULTS: The oocyte cryopreservation process had a high impact on the destruction of ooplasm cortical granules, Golgi complexes and mitochondria in vitrified-thawed PCOS oocytes compared to the other groups. In PCOS oocytes, particularly those that were vitrified-thawed, there was a notable increase in vacuolation, with a higher abundance of larger and more numerous vacuoles observed compared to the control group. The vitrified-thawed PCOS group also exhibited a notable increase in the expression of the apoptotic gene compared to the other groups (p < 0.05).
CONCLUSION: A precise evaluation of oocyte cryopreservation is imperative for improving this technique and for producing high-quality oocytes with enhanced fertility potential. This study contributes valuable insights into understanding the intricate relationship between PCOS, cryopreservation and oocyte quality. https://doi.org/10.54680/fr25210110412.
Exp Cell Res. 2025 Mar 18. pii: S0014-4827(25)00120-X. [Epub ahead of print]447(2): 114524

FSP1 regulates ferroptosis and mitochondrial function during mouse oocyte maturation.

Hongzhen Ruan, Huifen Xiang, Yajing Liu, Peiwen Wang, Liuliu Dong, Yunxia Cao, Dan Liang, Zhiming Ding.

  Oocyte quality plays a fundamental role in fertilization and embryonic development. Emerging evidence indicates that ferroptosis may impair oocyte quality. Ferroptosis suppressor protein 1 (FSP1), a known ferroptosis inhibitor, has an uncharacterized function in regulating oocyte quality during meiotic maturation. This study identified FSP1 expression across all stages of meiotic maturation with localization to the cytoplasm of mouse oocytes. Aged mice exhibited a marked reduction in FSP1 expression within the ovaries and oocytes. Pharmacological inhibition of FSP1 disrupted germinal vesicle breakdown and polar body emission, leading to spindle defects and chromosome misalignment. Additionally, FSP1 inhibition persistently activated the spindle assembly checkpoint, resulting in meiotic arrest. At the mechanistic level, inhibition of FSP1 led to an increase in intracellular Fe2+ levels, enhanced dihydroethidium fluorescence, excessive accumulation of reactive oxygen species, and intensified lipid peroxidation. Disruptions in ferroptosis-associated gene expression further indicated that oocytes underwent ferroptosis. Moreover, mitochondrial dysfunction was evident following FSP1 inhibition, as reflected by aberrant mitochondrial distribution, diminished ATP production, and an elevated mitochondrial membrane potential. Collectively, these results establish FSP1 as a key regulator of oocyte meiotic maturation by modulating iron homeostasis and mitochondrial function, while its inhibition triggers ferroptosis-dependent meiotic failure.

Keywords:  FSP1; Ferroptosis; Meiosis; Mitochondria; Oocyte

DOI:  https://doi.org/10.1016/j.yexcr.2025.114524
FASEB J. 2025 Mar 31. 39(6): e70469

Ovarian aging-associated downregulation of GPX4 expression regulates ovarian follicular development by affecting granulosa cell functions and oocyte quality.

Jingyi Hu, Huihui Wang, Junnan Fang, Ran Jiang, Yue Kong, Tongwei Zhang, Guang Yang, Haixia Jin, Senlin Shi, Ning Song, Lin Qi, Xianju Huang, Zhaoting Wu, Guidong Yao.

  In the physiological state, female fertility declines with age, as evidenced by a steady decline in oocyte quantity and quality. Aging of the first organ, the ovary, is accompanied by increased oxidative stress levels in the ovary, causing a decline in the ovarian reserve and follicular atresia. Ferroptosis is a novel mode of programmed cell death discovered in recent years and is involved in the onset and development of various diseases. To investigate whether ferroptosis regulates ovarian aging, we first examined granulosa cells from patients with a normal ovarian reserve, decreased ovarian reserve (DOR), and advanced age (Aged). GPX4, a key gene involved in ferroptosis, was identified. The marker of its activity, glutathione (GSH), was significantly downregulated in granulosa cells from the DOR and Aged groups. Transmission electron microscopy confirmed abnormal changes in mitochondrial morphology in granulosa cells from the DOR and Aged groups. In vitro, granulosa cell culture results showed that ferroptosis inducers inhibited cell growth by downregulating GPX4 expression. In contrast, ferroptosis inhibitors reversed the inhibitory effects of ferroptosis on granulosa cell growth by upregulating GPX4 expression. The results of mice in vivo experiments showed that the expression level of GPX4 was significantly decreased in the oocytes of aged mice and that Fer-1, an inhibitor of ferroptosis, reversed the decrease in the number of oocytes retrieved and the quality of oocytes in aged mice. Cyclophosphamide (CTX) was used to generate a mouse model of premature ovarian failure. The results showed that Fer-1 treatment significantly restored the inhibitory effect of CTX on GPX4 expression in the cumulus cells and partially reversed the adverse effects of CTX on the follicular reserve in the ovaries, the number of oocytes retrieved, and the quality of the oocytes in mice. The study findings suggest that ferroptosis is involved in regulating ovarian aging and that GPX4 is a key gene in regulating ovarian follicle development and ferroptosis and a potential key target for treating ovarian aging.

Keywords:  GPX4; ferroptosis; granulosa cell function; oocyte quality; ovarian aging

DOI:  https://doi.org/10.1096/fj.202401580RR
Cell Prolif. 2025 Mar 20. e70024

GPD1L-Mediated Glycerophospholipid Metabolism Dysfunction in Women With Diminished Ovarian Reserve: Insights From Pseudotargeted Metabolomic Analysis of Follicular Fluid.

Jiaqi Wu, Xuehan Zhao, Ying Fang, Cong Wang, Yichang Tian, Wan Tu, Qiqian Wu, Long Yan, Xiaokui Yang.

  Diminished ovarian reserve (DOR) is a pathological condition characterised by reduced ovarian function, which refers to the decreased quality and quantity of oocytes, potentially causing female infertility and various health issues. Follicular fluid (FF) serves as the microenvironment for follicular development and oocyte maturation, gaining an in-depth understanding of the metabolic state of FF will help us uncover the key biological processes involved in ovarian aging, while the specific underlying pathogenic mechanisms are not fully understood. In this study, we utilised pseudotargeted metabolomic analysis of FF to reveal the glycerophospholipid metabolism dysfunction mediated by GPD1L in DOR patients. We also found that GPD1L was downregulated in granulosa cells (GCs) of DOR patients, resulting in increased cell apoptosis and mitochondrial dysfunction. Moreover, our results demonstrated that the downregulated expression of GPD1L could induce follicular atresia and impair oocyte quality in mouse ovaries. Altogether, our research suggested that GPD1L in GCs and the key metabolites in the glycerophospholipid metabolism pathway could potentially act as novel biomarkers of DOR diagnosis, paving the way for a new theoretical basis for understanding the pathogenesis of DOR.

Keywords:  GPD1L; diminished ovarian reserve; follicular fluids; glycerophospholipid; metabolomics; mitochondria

DOI:  https://doi.org/10.1111/cpr.70024