bims-cebooc 2025-08-31 papers

bims-cebooc

Biomed News

on Cell biology of oocytes

Issue of 2025–08–31
eighteen papers selected by
Gabriele Zaffagnini, Universität zu Köln

Mevalonate metabolites boost aged oocyte quality through prenylation of small GTPases.
T4 DNA-Induced Reconstruction of Artificial Nuclei in Living Mouse Oocytes.
Mechanics of oogenesis: Lessons from C. elegans germline cysts.
A conserved triple arginine motif in OMA-1 is required for RNA-binding activity and embryo viability.
Kif11-haploinsufficient oocytes reveal spatially differential requirements for chromosome biorientation.
Drosophila COMPASS Complex Subunits Set1 and Ash2 Are Required for Oocyte Determination and Maintenance of the Synaptonemal Complex.
Germ cell formation and reproduction in tunicates.
ETS transcription factor pointed controls germline survival in Drosophila.
The mechanics behind the Drosophila egg.
Defining the cell and molecular origins of the primate ovarian reserve.
Ovarian germline stem cell dedifferentiation is cytoneme dependent.
The nuclear-cytoplasmic ratio controls the cell-cycle period in compartmentalized frog egg extract.
The full-length BEND2 protein is dispensable for spermatogenesis but required for setting the ovarian reserve in mice.
NAD+-dependent Sirt6 is a key regulator involved in telomere shortening of in vitro-cultured preimplantation embryos.
Multi-state catch bond formed in the Izumo1:Juno complex that initiates human fertilization.
Functional Methods for Studying Sperm-Zona Pellucida Interaction in Mammals.
Size-dependent temporal decoupling of morphogenesis and transcriptional programs in pseudoembryos.
Fertilization in the African clawed frog , Xenopus laevis , requires an egg-derived PLC to signal the fast block to polyspermy.

Nat Aging. 2025 Aug 26.

Mevalonate metabolites boost aged oocyte quality through prenylation of small GTPases.

Chuanming Liu, Huidan Zhang, Jialian Mao, Sainan Zhang, Xiao Tian, Yibing Zhu, Changjiang Wang, Junshun Fang, Huijie Pan, Nannan Kang, Yang Zhang, Jidong Zhou, Xin Zhen, Guijun Yan, Chaojun Li, Yali Hu, Cunqi Ye, Ran Xie, Chun So, Haixiang Sun, Lijun Ding.

Declining oocyte quality is the major contributor to female subfertility in aged mammals. Currently, there are no effective interventions to ameliorate aged oocyte quality. Here we found that oocytes at metaphase I from the cumulus-oocyte complexes of aged mice showed reduced cortical F-actin and lower levels of mevalonate (MVA) pathway metabolites, including MVA, farnesyl pyrophosphate (FPP) and geranylgeranyl pyrophosphate. We further showed that MVA supplementation improved FPP levels, cortical F-actin and the quality of aged oocytes. Mechanistically, we found that MVA supplementation induced granulosa cells to synthesize FPP, which was subsequently transferred to aged oocytes. Transported FPP increased the prenylation of small GTPases, including CDC42 and RAC1, and promoted membrane localization of CDC42-N-WASP-Arp2/3 and RAC1-WAVE2-Arp2/3 complexes, promoting cortical F-actin reassembly and reducing aneuploidy of aged oocytes. We also identified a natural chemical compound, 8-isopentenyl flavone, with an isopentenyl side chain from Epimedium brevicornu Maxim, which could increase CDC42 and RAC1 prenylation, improving the cortical F-actin and the competence of aged oocytes, and ameliorating reproductive outcomes in aged female mice. Collectively, increasing the prenylation of small GTPases via MVA metabolites or 8-isopentenyl flavone provides a therapeutic approach for boosting female fertility during reproductive aging.

DOI: https://doi.org/10.1038/s43587-025-00946-7
Methods Mol Biol. 2025 ;2958 183-199

T4 DNA-Induced Reconstruction of Artificial Nuclei in Living Mouse Oocytes.

Nao Yonezawa, Yasushi Hiraoka, Tokuko Haraguchi, Kazuo Yamagata.

  Fertilization involves a specialized nuclear formation process distinct from that of somatic cells, and reconstitution methods are useful for understanding its underlying mechanisms. Recently, we successfully reconstructed a nuclear-like structure, termed an "artificial nucleus," in living mouse oocytes by microinjecting solutions of T4 DNA (~166 kbp). This achievement allowed us to identify the physicochemical properties necessary for nuclear formation. In this paper, we describe a method for constructing artificial nuclei using T4 DNA solutions, which will contribute to future studies on the mechanisms of nuclear formation.

Keywords:  Artificial nucleus; Indirect immunofluorescence staining; Live-cell imaging; Microinjection; Mouse oocyte; T4 DNA

DOI:  https://doi.org/10.1007/978-1-0716-4714-1_13
Semin Cell Dev Biol. 2025 Aug 21. pii: S1084-9521(25)00054-0. [Epub ahead of print]175 103644

Mechanics of oogenesis: Lessons from C. elegans germline cysts.

Kenji Kimura, Fumio Motegi.

  Germ cells are organized into a syncytial architecture, wherein individual cells remain connected via intercellular bridges. Within this structural framework, known as germline cysts, a subset of germ cells enlarges and develops into oocytes, while others shrink and are eliminated through cell death. Recent studies with Caenorhabditis elegans have revealed that both apoptosis-mediated germ cell death and enlargement of surviving germ cells are regulated by mechanical forces. Germ cells exhibit stochastic fluctuations in volume driven by actomyosin contractility. This initial size heterogeneity is progressively amplified due to mechanical instability driven by differential hydrostatic pressure within the cyst, which biases smaller cells toward shrinkage and subsequent apoptotic death. This mechanical instability is further reinforced by the RAS/MAPK signaling cascade and the ECT-2/RhoA pathway, both of which enhance actomyosin contractility. Surviving germ cells continue to grow by acquiring the cytoplasmic materials through actomyosin contractility-mediated hydrodynamic flow within the cyst. Collectively, these findings highlight the critical role of mechanical forces in modulating cell fate decisions between survival and death, facilitating cell volume dynamics and maintaining germline homeostasis during oogenesis.

Keywords:  Actomyosin contractility; Cell death; Cytoplasmic streaming; Germ cell; Hydrostatic pressure; Oocyte; Oogenesis

DOI:  https://doi.org/10.1016/j.semcdb.2025.103644
RNA. 2025 Aug 27. pii: rna.080611.125. [Epub ahead of print]

A conserved triple arginine motif in OMA-1 is required for RNA-binding activity and embryo viability.

Asli Ertekin, Sharon T Noronha, Christable Darko, Francesca Massi, Sean Patrick Ryder.

  Sexually reproducing organisms make haploid gametes-oocytes and spermatocytes-that combine during fertilization to make an embryo. While both gametes contain similar DNA content, oocytes con-tain the bulk of the cytoplasm including maternally supplied mRNAs and proteins required prior to zygotic gene activation. RNA-binding proteins are key regulators of these maternal transcripts. In Caenorhabditis elegans, the tandem zinc finger proteins OMA-1 and OMA-2 are required for fertiliza-tion. Here, we show that OMA-1 RNA-binding activity requires a short basic region immediately up-stream from the canonical tandem zinc finger domain. Mutation of this region in animals produces a phenotype distinct from a genetic null. Oocytes can be fertilized, but fail to form an intact chitin egg-shell, frequently break in utero, and arrest prior to morphogenesis. Our results identify a critical region outside of the canonical RNA-binding domain required for both RNA-binding activity as well as re-vealing a new role for OMA-1 during the oocyte-to-embryo transition.

Keywords:  C. elegans; NMR; RNA-binding protein; embryogenesis; post-transcriptional regulation

DOI:  https://doi.org/10.1261/rna.080611.125
EMBO Rep. 2025 Aug 20.

Kif11-haploinsufficient oocytes reveal spatially differential requirements for chromosome biorientation.

Tappei Mishina, Aurélien Courtois, Shuhei Yoshida, Kohei Asai, Hiroshi Kiyonari, Tomoya S Kitajima.

  Bipolar spindle assembly and chromosome biorientation are prerequisites for chromosome segregation during cell division. The kinesin motor KIF11 (also widely known as Eg5) drives spindle bipolarization by sliding antiparallel microtubules bidirectionally, elongating a spherical spindle into a bipolar-shaped structure in acentrosomal oocytes. During meiosis I, this process stretches homologous chromosome pairs, establishing chromosome biorientation at the spindle equator. The quantitative requirement for KIF11 in acentrosomal spindle bipolarization and homologous chromosome biorientation remains unclear. Here, using a genetic strategy to modulate KIF11 expression levels, we show that Kif11 haploinsufficiency impairs spindle elongation, leading to the formation of a partially bipolarized spindle during meiosis I in mouse oocytes. While the partially bipolarized spindle allows chromosome stretching in the inner region of its equator, it fails to do so in the outer region, where merotelic kinetochore-microtubule attachments are favored to form. These findings demonstrate the necessity of biallelic functional Kif11 for bipolar spindle assembly in acentrosomal oocytes and reveal a spatially differential requirement for homologous chromosome biorientation within the spindle.

Keywords:  Chromosome Segregation; Meiosis; Oocyte; Spindle

DOI:  https://doi.org/10.1038/s44319-025-00539-w
J Dev Biol. 2025 Aug 19. pii: 30. [Epub ahead of print]13(3):

Drosophila COMPASS Complex Subunits Set1 and Ash2 Are Required for Oocyte Determination and Maintenance of the Synaptonemal Complex.

Brigite Cabrita, Mary Enyioko, Rui Gonçalo Martinho.

  Female gametogenesis is orchestrated by dynamic epigenetic modifications. In mammals, SETDB1, a histone H3K9 methyltransferase, is required for proper meiotic progression and early embryonic development. In Drosophila, the ortholog of SETDB1 plays a critical role in germ cell differentiation, transposon silencing, and the transcriptional repression of specific germline genes during oocyte fate determination. Moreover, Polycomb group (PcG) proteins in both mammals and Drosophila are essential for primary oocyte viability and meiosis, functioning through the silencing of early prophase I genes during later stages of prophase. While the repressive roles of epigenetic regulators in both Drosophila and mammalian oogenesis are well characterized, the functions of epigenetic activators remain less defined. Gene expression is controlled by the opposing activities of PcG and Trithorax group (TrxG) proteins, with the latter constituting a diverse family of chromatin remodelling factors that include H3K4 methyltransferases. In Drosophila, SET domain containing 1 (Set1)-the ortholog of mammalian SETD1A/B-acts as the primary regulator of global H3K4me2/3 levels. Set1 is critical for germline stem cell (GSC) self-renewal, functioning through both cell-autonomous and non-cell-autonomous mechanisms, with its depletion in the germline resulting in a progressive loss of GSC. More recently, Set1 has been implicated in germline cyst differentiation, although the mechanisms underlying this role remain poorly understood due to the complexity of the observed phenotypes. To investigate this, we analyzed ovaries from recently eclosed females in which Set1 and its highly conserved COMPASS partner, absent, small, or homeotic discs 2 (Ash2), were depleted-thus minimizing the confounding effects from GSC loss. We observed striking defects in both oocyte determination and Synaptonemal Complex (SC) integrity in one- to two-day-old females, within otherwise normal egg chambers. Interestingly, while defects in oocyte fate and oocyte-chromatin architecture were partially recovered in older egg chambers, SC integrity remained compromised. These findings suggest a critical window for SC assembly during germline cyst differentiation, after which this assembly cannot occur.

Keywords:  Ash2; COMPASS complex; Set1; oocyte determination; synaptonemal complex

DOI:  https://doi.org/10.3390/jdb13030030
Dev Biol. 2025 Aug 18. pii: S0012-1606(25)00230-1. [Epub ahead of print]527 226-249

Germ cell formation and reproduction in tunicates.

Yasunori Sasakura, Takeshi Sunanaga, Takeshi A Onuma, Honoo Satake.

  Because tunicates are the closest living relatives of vertebrates within the phylum Chordata, understanding the mechanisms of tunicate germ cell formation is essential to infer this process in ancestral chordates. Vasa-localization to primordial germ cells (PGCs), PGC formation biased to the posterior side of embryos, and transcriptional silencing by phosphorylation of RNA polymerase II are the core PGC-forming events inherited from the shared ancestor of protostomes and deuterostomes. Neuropeptide- and peptidase-mediated regulations of oocyte maturation are examples of mechanisms observed in both vertebrates and tunicates. However, the pathways that activate and regulate these mechanisms, such as the hypothalamus-pituitary-gonad axis, are not always conserved between tunicates and vertebrates, suggesting that these animals achieved the same end-products via different molecular mechanisms. Tunicates are divided into the classes Ascidiacea, Thaliacea, and Larvacea, each of which exhibits specific characteristics in germ cell formation. Some ascidians form colonies of interconnected zooids, each having regenerative capacity sufficient to regrow the entire body, including gametes, from a tiny body piece. Larvaceans maintain their tadpole shape throughout their very short life cycle: they manage to complete their gamete formation using small gene sets encoded in the shortest genomes yet observed among non-parasitic animals. These group-specific characteristics are likely to reflect different strategies for ensuring survival in the respective environments.

Keywords:  Ascidians; CAB; Follicle; Larvaceans; Postplasmic/PEM RNA; Regeneration; Syncytium; Vasa

DOI:  https://doi.org/10.1016/j.ydbio.2025.08.013
PLoS Genet. 2025 Aug 25. 21(8): e1011809

ETS transcription factor pointed controls germline survival in Drosophila.

Alicia E Rosales-Nieves, Miriam Marín-Menguiano, Lourdes López-Onieva, Juan Garrido-Maraver, Acaimo González-Reyes.

Proper gonad development is a pre-requisite for gametogenesis and reproduction. During female gonad formation in Drosophila, the EGF receptor (EGFR) signalling pathway ensures the correct number of primordial germ cells (PGCs) populate the larval gonad. We study the gene pointed (pnt), which acts downstream of the EGFR receptor and belongs to the ETS transcription factor family, with a previously unknown function in gonadogenesis. We report that pnt is expressed in female larval gonads and later in the adult ovarian germline niche and that it is required to sustain proper gametogenesis. Loss of pnt function in female larval gonads, similar to the EGFR, induced PGC overproliferation. Conversely, we isolated a novel mutant allele gene, termed pntaga, which resulted in agametic gonads and ovaries. While pntaga embryos developed gonads containing a normal complement of PGCs, these are subsequently lost by apoptosis during late larval and pupal stages. Molecular characterization of pntaga revealed reduced expression levels of the different pnt isoforms, unveiling a complex autoregulatory network involving the three Pnt proteins. We propose that germline survival in Drosophila gonads requires a precise tuning of EGFR signalling to ensure the appropriate transcriptional activation of its target pnt.

DOI: https://doi.org/10.1371/journal.pgen.1011809
Semin Cell Dev Biol. 2025 Aug 21. pii: S1084-9521(25)00048-5. [Epub ahead of print]175 103638

The mechanics behind the Drosophila egg.

Megha Maria Jacob, Muriel Grammont.

  The formation and the development of the Drosophila egg involves multiple mechanical cross-talks between germline cells, somatic cells and the surrounding basement membrane. In this review, we discuss several development stages when the sources, as well as the roles, of mechanical forces in egg shape establishment are well defined. The examples described here illustrate the diversity of these forces as well as of the tools used to measure them and of the outcome each of them generates. We examine their contributions and their integration to morphogenesis. We discuss the limitations of our current knowledge, the importance of developing novel approaches and the support that modelling could bring to tackle some issues. One major future challenge is to understand how robustness in shaping the egg is achieved when the contributors act in different cell types and at different times. Studying Drosophila egg formation thus remains an exciting model in developmental biology as it must integrate a variety of biomechanical inputs from its environment, in addition of the biochemical signals discovered in the past.

Keywords:  Drosophila; Mechanical forces; Morphogenesis; Ovarian follicle development

DOI:  https://doi.org/10.1016/j.semcdb.2025.103638
Nat Commun. 2025 Aug 26. 16(1): 7539

Defining the cell and molecular origins of the primate ovarian reserve.

Sissy E Wamaitha, Ernesto J Rojas, Francesco Monticolo, Fei-Man Hsu, Enrique Sosa, Amanda M Mackie, Kiana Oyama, Maggie Custer, Melinda Murphy, Diana J Laird, Jian Shu, Jon D Hennebold, Amander T Clark.

The primate ovarian reserve is established during late fetal development and consists of quiescent primordial follicles in the ovarian cortex each composed of granulosa cells surrounding an oocyte in dictate. As late stages of fetal development are not routinely accessible using human tissues, the current study exploits the evolutionary proximity of the rhesus macaque to investigate follicle formation in primates. Like in humans, the rhesus prenatal ovary develops multiple types of pre-granulosa cells in time and space, with primordial follicles deriving from later emerging pre-granulosa subtypes. In addition, our work shows that activated medullary follicles recruit fetal theca cells to establish a two-cell system for sex-steroid hormone production prior to birth, providing a cell-based explanation for mini puberty.

DOI: https://doi.org/10.1038/s41467-025-62702-0
Proc Natl Acad Sci U S A. 2025 Sep 02. 122(35): e2426145122

Ovarian germline stem cell dedifferentiation is cytoneme dependent.

Catherine Sutcliffe, Nabarun Nandy, Raluca Revici, Heather Johnson, Shukry J Habib, Hilary L Ashe, Scott G Wilcockson.

  Progenitor cell dedifferentiation is important for stem cell maintenance during tissue repair and age-related stem cell decline. Here, we use the Drosophila ovary as a model to study the role of cytonemes in bone morphogenic protein (BMP) signaling-directed germline stem cell (GSC) maintenance and dedifferentiation of germ cells to GSCs. We provide evidence that differentiating germ cell cysts extend longer cytonemes that are more polarized toward the niche during dedifferentiation to reactivate BMP signaling. The presence of additional somatic cells in the niche is associated with a failure of germ cell dedifferentiation, consistent with the formation of a physical barrier to cytoneme-niche contact and outcompetition of germ cells for BMP. Using BMP beads in vitro, we show that these are sufficient to induce cytoneme-dependent contacts in Drosophila tissue culture cells. We demonstrate that the Enabled (Ena) actin polymerase is localized to the tips of germ cell cytonemes and is necessary for robust cytoneme formation, as its mislocalization reduces the frequency, length, and directionality of cytonemes. During homeostasis, specifically perturbing cytoneme function through Ena mislocalization impairs GSC fitness by reducing GSC BMP signaling and niche occupancy. Disrupting cytonemes by targeting Ena during dedifferentiation reduces germ cell BMP responsiveness and the ability of differentiating cysts to dedifferentiate. Overall, our results provide evidence that cytonemes play a fundamental role in establishing polarized signaling and niche occupancy during stem cell maintenance and dedifferentiation.

Keywords:  BMP signaling; cytoneme; dedifferentiation; enabled; germline stem cell

DOI:  https://doi.org/10.1073/pnas.2426145122
Curr Biol. 2025 Aug 22. pii: S0960-9822(25)01021-8. [Epub ahead of print]

The nuclear-cytoplasmic ratio controls the cell-cycle period in compartmentalized frog egg extract.

Liliana Piñeros, Nikita Frolov, Daniel Ruiz-Reynés, Aleyde Van Eynde, Gabriel Cavin-Meza, Rebecca Heald, Lendert Gelens.

  Each proliferating cell replicates its DNA and internal components before distributing this material evenly to its daughters. Although the regulation of cyclin-dependent kinases (Cdks) that dictate orderly cell-cycle progression is well characterized, how the subcellular localization of the cell-cycle machinery contributes to timing is not well understood. We investigated the influence of the nucleus by reconstituting cell-cycle oscillations in droplets of frog egg extract in the absence or presence of a nuclear compartment and monitoring dynamics by time-lapse microscopy. We found that the cell-cycle time increased in the presence of nuclei, which grew larger with each cell cycle. The correlation between increasing nuclear volume and a longer cell-cycle period was maintained across extracts and nuclei from various Xenopus species and persisted upon inhibition of DNA replication or transcription. However, inhibition of nuclear import or the kinase Wee1 impacted the relationship between the nuclear-cytoplasmic ratio and the cell-cycle period. To conceptually capture these experimental observations, we developed a computational model that incorporates cell-cycle oscillations, nuclear-cytoplasmic compartmentalization, and periodic nuclear envelope breakdown and reformation. Altogether, our results support the major role of the nuclear compartment in setting the pace of the cell cycle and provide an explanation for the increase in cell-cycle length observed at the midblastula transition when cells become smaller and the nuclear-cytoplasmic ratio increases.

Keywords:  Cdk1 regulation; MBT; Xenopus egg extract; cell-cycle oscillations; compartmentalization; computational modeling; embryonic development; midblastula transition; nuclear import; nuclear size; nuclear-cytoplasmic ratio

DOI:  https://doi.org/10.1016/j.cub.2025.07.075
Elife. 2025 Aug 20. pii: RP96052. [Epub ahead of print]13

The full-length BEND2 protein is dispensable for spermatogenesis but required for setting the ovarian reserve in mice.

Yan Huang, Nina Bucevic, Carmen Coves, Natalia Felipe-Medina, Marina Marcet-Ortega, Nikoleta Nikou, Cristina Madrid-Sandín, Maria López-Panadés, Carolina Buza, Neus Ferrer Miralles, Antoni Iborra, Anna Pujol, Alberto M Pendás, Ignasi Roig.

  Infertility affects up to 12% of couples globally, with genetic factors contributing to nearly half of the cases. Advances in genomic technologies have led to the discovery of genes like Bend2, which play a crucial role in gametogenesis. In the testis, Bend2 expresses two protein isoforms: full-length and a smaller one. Ablation of both proteins results in an arrested spermatogenesis. Because the Bend2 locus is on the X chromosome, and the Bend2-/y mutants are sterile, BEND2's role in oogenesis remained elusive. In this study, we employed a novel Bend2 mutation that blocks the expression of the full-length BEND2 protein but allows the expression of the smaller BEND2 isoform. Interestingly, this mutation does not confer male sterility and mildly affects spermatogenesis. Thus, it allowed us to study the role of BEND2 in oogenesis. Our findings demonstrate that full-length BEND2 is dispensable for male fertility, and its ablation leads to a reduced establishment of the ovarian reserve. These results reveal a critical role for full-length BEND2 in oogenesis and provide insights into the mechanisms underlying the establishment of the ovarian reserve. Furthermore, these findings hold relevance for the diagnostic landscape of human infertility.

Keywords:  BEND2; cell biology; developmental biology; gametogenesis; infertility; meiosis; mouse; ovarian reserve

DOI:  https://doi.org/10.7554/eLife.96052
Commun Biol. 2025 Aug 23. 8(1): 1275

NAD+-dependent Sirt6 is a key regulator involved in telomere shortening of in vitro-cultured preimplantation embryos.

Danjun Li, Wenzhi Li, Xiaoyu Liao, Shutian Jiang, Meng Ma, Zhijie Hu, Kaibo Lin, Weina Yu, Xue Sun, Yong Fan, Haibo Wu, Mingru Yin, Li Wang, Lun Suo, Hui Long, Xuefeng Lu, Yanping Kuang, Qifeng Lyu.

Telomere length (TL) is important for maintaining the individual health of a species. Recent studies shows that in vitro fertilization therapy can drastically reduce TL in offspring, however, the underlying molecular mechanism remains unknown. Sirt6 is a NAD+-dependent epigenetic regulator that has recently been found to play an important role in maintaining telomere stability. Here, we report that NAD+ deficiency in in vitro-cultured blastocysts impairs Sirt6 function, triggering telomere shortening of the inner cell mass and possibly affecting newborns. This phenotype could be effectively mitigated by supplementation with nicotinamide mononucleotide (NAD+ precursor) during in vitro culture, while it could not be achieved in Sirt6 conditional knockout embryos. mtROS accumulation and epigenetic modifications may also be involved in this process. Our results reveal the mechanism by which in vitro culture induces telomere shortening in preimplantation embryos, providing a potential target for improving in vitro culture conditions.

DOI: https://doi.org/10.1038/s42003-025-08567-x
Nat Commun. 2025 Aug 26. 16(1): 7952

Multi-state catch bond formed in the Izumo1:Juno complex that initiates human fertilization.

Sean Boult, Paulina Pacak, Byeongseon Yang, Haipei Liu, Viola Vogel, Michael A Nash.

Izumo1:Juno-mediated adhesion between sperm and egg cells is essential for mammalian sexual reproduction. However, conventional biophysical and structural approaches have provided only limited functional insights. Using atomic force microscopy-based single-molecule force spectroscopy and all-atom steered molecular dynamic simulations, we explore the role of mechanical forces in regulating the human Izumo1:Juno complex. Our findings reveal a multi-state catch bond capable of withstanding forces up to 600 pN- mechanostability rarely observed among eukaryotic protein complexes. We find that this enhanced mechanostability is impaired in the infertility-associated mutant, JunoH177Q. Detailed steered molecular dynamics simulations show how force-dependent structural reorganization of the Izumo1:Juno complex engages previously undiscovered binding conformations to achieve this state of high mechanostability. Overall, this study significantly enhances our understanding of the mechanical underpinnings that regulate human fertilization.

DOI: https://doi.org/10.1038/s41467-025-62427-0
Methods Protoc. 2025 Aug 13. pii: 95. [Epub ahead of print]8(4):

Functional Methods for Studying Sperm-Zona Pellucida Interaction in Mammals.

Natalie Zelenkova, Veronika Kraus, Alexandra Maresova, Zuzana Pilsova, Aneta Pilsova, Barbora Klusackova, Eva Chmelikova, Katerina Komrskova, Pavla Postlerova.

  The initial molecular events mediating mammalian sperm binding to the zona pellucida (ZP) of the oocyte are highly complex and still not fully elucidated. Recent advances have identified multiple candidate sperm surface proteins, often functioning as part of high-molecular-weight complexes that mediate this critical fertilization event in a species-specific and coordinated manner. To address a significant gap in the literature, we provide an in-depth overview of the functional assays employed to investigate sperm-ZP interactions, emphasizing their underlying principles, potential applications, and key methodological strengths and limitations. The techniques discussed range from classical in vitro sperm-oocyte and hemizona binding assays, including antibody-blocking and competitive strategies, to cutting-edge in vivo genetic models, each contributing unique insights into the physiological relevance of the proposed ZP receptors. Robust experimental design, including the use of appropriate controls and validation strategies, is essential for accurately interpreting the role of candidate sperm receptors. This review provides a structured overview of current methodologies to support researchers in critically evaluating and applying functional assays in future studies.

Keywords:  antibody; antibody block; binding assay; competitive assay; hemizona binding assay; knockout model; recombinant protein; sperm receptor; sperm–ZP binding

DOI:  https://doi.org/10.3390/mps8040095
Sci Adv. 2025 Aug 22. 11(34): eadv7790

Size-dependent temporal decoupling of morphogenesis and transcriptional programs in pseudoembryos.

Isma Bennabi, Pauline Hansen, Melody Merle, Judith Pineau, Lucille Lopez-Delisle, Dominique Kolly, Denis Duboule, Alexandre Mayran, Thomas Gregor.

Understanding the interplay between cell fate specification and morphogenetic changes remains a challenge in developmental biology. Gastruloids, stem cell models of postimplantation mammalian development, provide a platform to address this question. Here, using quantitative live imaging and transcriptomic profiling, we show that physical parameters, particularly system size, affect morphogenetic timing and outcomes. Larger gastruloids exhibit delayed symmetry breaking, increased multipolarity, and prolonged axial elongation, with morphogenesis driven by size. Despite these variations, transcriptional programs and cell fate composition remain stable across a broad size range, illustrating the scaling of gene expression domains. In particular, extreme sizes show distinct transcriptional modules and shifts in gene expression patterns. Size perturbation experiments rescued the morphogenetic and pattern phenotypes observed in extreme sizes, demonstrating the adaptability of gastruloids to their effective system size. These findings position gastruloids as versatile models for dissecting spatiotemporal coordination in mammalian development and reveal how physical constraints can decouple gene expression programs from morphogenetic progression.

DOI: https://doi.org/10.1126/sciadv.adv7790
MicroPubl Biol. 2025 ;2025

Fertilization in the African clawed frog , Xenopus laevis , requires an egg-derived PLC to signal the fast block to polyspermy.

Kayla M Komondor, Katherine G Sharp, Anne E Carlson.

Fertilization in Xenopus laevis triggers calcium release and membrane depolarization to activate the fast block to polyspermy. This depolarization requires phospholipase C (PLC) activity, but the identity and origin of the PLC remained unclear. We previously reported that PLCZ1 , which encodes the sperm-derived PLCζ used in mammals and birds, was deleted in Pipidae frogs, suggesting an alternative mechanism. Here, we used the irreversible PLC inhibitor U73122 to test whether the PLC driving the fast block originates from the egg or sperm. Inhibiting PLC activity in the egg, but not in the sperm, abolished the fertilization-evoked depolarization and led to polyspermy. These findings demonstrate that X. laevis relies on an egg-derived PLC to signal the fast block, revealing a fertilization-triggered calcium signaling pathway that is mechanistically distinct from other vertebrates.

DOI: https://doi.org/10.17912/micropub.biology.001638