bims-cebooc 2025-11-23 papers

bims-cebooc

Biomed News

on Cell biology of oocytes

Issue of 2025–11–23
thirteen papers selected by
Gabriele Zaffagnini, Universität zu Köln

Oocyte Age-Dependent DNA Damage Can Be Reverted by the DNA Repair Competent Karyoplasm of Young Oocytes.
A simple, efficient, and scalable method to generate oocyte-like cells in vitro.
Comprehensive profiling of migratory primordial germ cells reveals niche-specific differences in non-canonical Wnt and Nodal-Lefty signaling in anterior vs posterior migrants.
An Nlrp5-null mutation leads to attenuated de novo methylation in oocytes, accompanied by a significant reduction in DNMT3L.
Mechanical coordination between anaphase A and B drives asymmetric chromosome segregation.
Somatic Kitl promotes mTOR to facilitate prophase I of meiosis in female embryonic gonads.
TRPM-mediated mechanoreception regulates myosin oscillation during tissue elongation.
5-Hydroxymethylcytosine Dynamics Reveals Coordinated Reprogramming of Parental Genomes and X Chromosome Dosage Balance in Mouse SCNT Embryos.
Loss of full-length DAZL isoform disrupts PABPC1-dependent translational regulation and meiosis.
Mitochondrial and Glucose Metabolic Patterns in Pre-Granulosa Cells and Oocytes and Their Dysfunctions Induce Impaired Primordial Follicle Formation in Mice.
A mechanical origin for implantation defects in embryos from aged females.
Capturing aberrant cell behaviors producing defects in human embryos via live imaging.
CRISPR-RfxCas13d screening uncovers Bckdk as a post-translational regulator of maternal-to-zygotic transition in teleosts.

Aging Cell. 2025 Nov 15. e70300

Oocyte Age-Dependent DNA Damage Can Be Reverted by the DNA Repair Competent Karyoplasm of Young Oocytes.

Nataliia Dudko, Tereza Ilcikova, Natalie Novotna, Marta Czernik, Pasqualino Loi, Josef Fulka, Pritha Bhattacharjee, Raffaella Santoro, Helena Fulka.

  Mammalian fully grown oocytes are believed to exhibit a weakened DNA damage response, leading to the accumulation of substantial levels of DNA damage and increased frequency of aneuploidies in an age-dependent manner. These hallmarks of reproductive ageing are generally presumed to be irreversible by rendering the oocyte chromosome complement incompatible with development. To test whether this is indeed true, we performed a series of germinal vesicle (GV) transfers between oocytes from females of late breeding/post-breeding age and oocytes from young animals. Our results show that age-associated DNA damage can be effectively suppressed: introducing the GVs of advanced-maternal-age (AMA) oocytes into DNA repair-competent cytoplasts generated by selective enucleation (SE) of young oocytes effectively suppresses the signs of age-dependent DNA damage. This is accompanied by a partial recovery of the chromatin dynamics and, surprisingly, a higher fidelity of chromosome segregation. By dissecting the GV fractions, we show that the ability to sense and repair DNA is linked to the free, non-chromatin-bound nuclear factors but not the oocyte nucleolus. Finally, we show that the overall improved state of the reconstructed oocytes is accompanied by enhanced full-term development. Therefore, contrary to popular belief, our results show that the age-associated decline in oocyte quality can be effectively mitigated, opening new possibilities for cell-based oocyte therapy.

Keywords:  DNA damage; ageing; chromosomal aberrations; oocyte

DOI:  https://doi.org/10.1111/acel.70300
Life Sci Alliance. 2026 Feb;pii: e202503379. [Epub ahead of print]9(2):

A simple, efficient, and scalable method to generate oocyte-like cells in vitro.

Ami Banno, Kana Mizuno, Mizuki Sakamoto, Sota Komatsubara, Kenjiro Shirane, Katsuhiko Hayashi, Nobuhiko Hamazaki, Koshi Imami, Shigenobu Yonemura, Takashi Ishiuchi.

Understanding the molecular basis of oocyte identity and function is essential not only for basic biology but also for clinical applications, as it is closely linked to female infertility. However, technical challenges remain in advancing this understanding, mainly because of the difficulty in obtaining a sufficient number of oocytes. In this study, through refining previously reported three-dimensional protocols, we established a two-dimensional culture method that efficiently generates oocyte-like cells, referred to as mini-oocytes, from mouse embryonic stem cells. This method requires minimal labor, does not rely on supporting somatic cells, and leverages a transcription factor-mediated approach for oocyte-like cell generation. Our transcriptome and proteome analyses revealed significant similarities between in vitro-derived mini-oocytes and in vivo oocytes, despite their relatively smaller size. Furthermore, we demonstrated the utility of mini-oocytes for investigating oocyte-specific molecular features through a small-scale knockout screen targeting the subcortical maternal complex. Given the simplicity, efficiency, and scalability of the mini-oocyte induction method, it offers a practical platform for conducting experiments that are otherwise challenging with in vivo oocytes.

DOI: https://doi.org/10.26508/lsa.202503379
Elife. 2025 Nov 19. pii: RP103074. [Epub ahead of print]14

Comprehensive profiling of migratory primordial germ cells reveals niche-specific differences in non-canonical Wnt and Nodal-Lefty signaling in anterior vs posterior migrants.

Rebecca Garrett Jaszczak, Jay W Zussman, Daniel E Wagner, Diana J Laird.

  Mammalian primordial germ cells (PGCs) migrate asynchronously through the embryonic hindgut and dorsal mesentery to reach the gonads. We previously found that interaction with different somatic niches regulates mouse PGC proliferation along the migration route. To characterize transcriptional heterogeneity of migrating PGCs and their niches, we performed single-cell RNA sequencing of 13,262 mouse PGCs and 7868 surrounding somatic cells during migration (E9.5, E10.5, E11.5) and in anterior vs posterior locations to enrich for leading and lagging migrants. Analysis of PGCs by position revealed dynamic gene expression changes between faster or earlier migrants in the anterior and slower or later migrants in the posterior at E9.5; these differences include migration-associated actin polymerization machinery and epigenetic reprogramming-associated genes. We furthermore identified changes in signaling with various somatic niches, notably strengthened interactions with hindgut epithelium via non-canonical WNT (ncWNT) in posterior PGCs compared to anterior. Reanalysis of a previously published dataset suggests that ncWNT signaling from the hindgut epithelium to early migratory PGCs is conserved in humans. Trajectory inference methods identified putative differentiation trajectories linking cell states across timepoints and from posterior to anterior in our mouse dataset. At E9.5, we mainly observed differences in cell adhesion and actin cytoskeletal dynamics between E9.5 posterior and anterior migrants. At E10.5, we observed divergent gene expression patterns between putative differentiation trajectories from posterior to anterior, including Nodal signaling response genes Lefty1, Lefty2, and Pycr2 and reprogramming factors Dnmt1, Prc1, and Tet1. At E10.5, we experimentally validated anterior migrant-specific Lefty1/2 upregulation via whole-mount immunofluorescence staining for LEFTY1/2 and phosphorylated SMAD2/3, suggesting that elevated autocrine Nodal signaling in migrating PGCs occurs as they near the gonadal ridges. Together, this positional and temporal atlas of mouse PGCs supports the idea that niche interactions along the migratory route elicit changes in proliferation, actin dynamics, pluripotency, and epigenetic reprogramming.

Keywords:  Nodal; Wnt; cell heterogeneity; cell migration; developmental biology; mouse; primordial germ cell

DOI:  https://doi.org/10.7554/eLife.103074
Mol Hum Reprod. 2025 Nov 18. pii: gaaf055. [Epub ahead of print]

An Nlrp5-null mutation leads to attenuated de novo methylation in oocytes, accompanied by a significant reduction in DNMT3L.

Leah Nic Aodha, Alexandra Pokhilko, Leah U Rosen, Styliani Galatidou, Edyta Walewska, Christian Belton, Antonio Galvao, Hanneke Okkenhaug, Lu Yu, Asif Nakhuda, Bill Mansfield, Soumen Khan, David Oxley, Montserrat Barragán, Gavin Kelsey.

  Nlrp5 encodes a core component of the subcortical maternal complex (SCMC) a cytoplasmic protein structure unique to the mammalian oocyte and cleavage-stage embryo. NLRP5 mutations have been identified in patients presenting with early embryo arrest, recurrent molar pregnancies and imprinting disorders. Correct patterning of DNA methylation over imprinted domains during oogenesis is necessary for faithful imprinting of genes. It was previously shown that oocytes with mutation in the human SCMC gene KHDC3L had globally impaired methylation, indicating that integrity of the SCMC is essential for correct establishment of DNA methylation at imprinted regions. Here, we present a multi-omic analysis of an Nlrp5-null mouse model, which in germinal vesicle (GV) stage oocytes displays a misregulation of a broad range of maternal proteins, including proteins involved in several key developmental processes. This misregulation likely underlies impaired oocyte developmental competence. Amongst impacted proteins are several epigenetic modifiers, including a substantial reduction in DNMT3L; we show that de novo DNA methylation is attenuated in Nlrp5-null oocytes, including at some imprinting control regions. This provides evidence for a mechanism of epigenetic impairment in oocytes which could contribute to downstream misregulation of imprinted genes.

Keywords:  DNA methylation; Nlrp5; Subcortical Maternal Complex; epigenetics; imprinting; multi-omics; oocyte

DOI:  https://doi.org/10.1093/molehr/gaaf055
bioRxiv. 2025 Oct 04. pii: 2025.10.02.680008. [Epub ahead of print]

Mechanical coordination between anaphase A and B drives asymmetric chromosome segregation.

Ana M Dias Maia Henriques, Tim Davies, Serge Dmitrieff, Nicolas Minc, Julie C Canman, Julien Dumont, Gilliane Maton.

Chromosome segregation during anaphase occurs through two mechanistically distinct processes: anaphase A, in which chromosomes move toward spindle poles, and anaphase B, in which the anaphase spindle elongates through cortical astral microtubule pulling forces. Caenorhabditis elegans embryos have been thought to rely primarily on anaphase B, with little to no contribution from anaphase A. Here, we uncover a novel anaphase A mechanism in C. elegans embryos, driven by the kinesin-13 KLP-7 MCAK and opposed by the kinesin-12 KLP-18. We found that the extent of chromosome segregation during anaphase A is asymmetrically regulated by cell polarity cues and modulated by mechanical tension within the spindle, generated by opposing forces acting on chromosomes and spindle poles. Additionally, we found that the contribution of anaphase A to chromosome segregation increases progressively across early embryonic divisions. These findings uncover an unexpected role for anaphase A in early C. elegans development and reveal a KLP-7 MCAK -dependent mechanical coordination between anaphase A and anaphase B driven chromosome segregation.
eTOC summary: Dias Maia Henriques et al. uncover an anaphase A pathway, driven by the kinesin-13 KLP-7 and opposed by the kinesin-12 KLP-18, that contributes to chromosome segregation in early C. elegans embryos. Its activity is regulated by spindle tension, cell polarity cues, and progressively increases during early embryonic divisions.

DOI: https://doi.org/10.1101/2025.10.02.680008
Cell Death Dis. 2025 Nov 17. 16(1): 838

Somatic Kitl promotes mTOR to facilitate prophase I of meiosis in female embryonic gonads.

Chang Liu, Ziyi Jin, Jiyu Chen, Jie Li, Guofeng Feng, Guoxing Yin, Yongqin Yu, Xiaoying Ye, Haowei Sun, Hua Zhang, Fei Gao, Lin Liu.

Homologous synapsis and recombination are the central events that take place in the prophase I of meiosis. Signaling that promotes the germ cell differentiation and prophase I remains elusive. Here we show a key Kitl/Kit signaling between somatic cells and germ cells in regulating meiotic prophase I in the mouse fetal gonad. Disruption of Kitl/Kit signaling, both in vivo and in vitro, impairs meiosis initiation, disrupts homologous synapsis and recombination. Moreover, mTOR/p-S6 signaling induced by Kitl/Kit elevates the levels of critical proteins such as Stra8, Sycp1 and Sycp3 for meiosis entry and homologous synapsis. Blocking Kitl/Kit signaling suppresses the mTOR and decreases the protein levels of Stra8, Sycp1, Sycp3 and Vasa, impairing the prophase I. In contrast, activating mTOR can rescue the meiotic defects caused by somatic Kitl deficiency. The activated p-AKT links Kitl/Kit to promoting mTOR/p-S6 signaling in the fetal germ cells. These findings reveal the critical functions and mechanisms of somatic Kitl in meiosis entry and homologous synapsis and recombination during the prophase I.

DOI: https://doi.org/10.1038/s41419-025-08158-y
Curr Biol. 2025 Nov 18. pii: S0960-9822(25)01381-8. [Epub ahead of print]

TRPM-mediated mechanoreception regulates myosin oscillation during tissue elongation.

Zhixiang Dong, Heng Wang, Renchang Zhang, Ziqi Guo, Boxin Zhang, Ruoyi Pei, Xuan Guo, Peng Xia, Guangwei Si, Jiong Chen.

  Periodic oscillation of myosin II has been shown to be required for a wide variety of morphogenetic processes, including tissue elongation of Drosophila egg chambers during mid and late oogenesis. But what developmental cues initiate myosin oscillation in the basal region of the somatic follicle cells in stage 9 egg chambers is not clear. Here, we show that increased mechanical pressure caused by the growth of the adjacent germline tissue could serve as a temporal and spatial cue that helps induce basal myosin oscillation in early-mid stage 9 follicle cells through the function of the mechanosensing TRPM (transient receptor potential M) channel. We demonstrate that TRPM is expressed in stage 9 follicle cells and is required for calcium influx, myosin oscillation, and tissue elongation. Furthermore, calcium levels and the propagation of calcium waves across the follicle epithelium-which requires gap junction function-are critical for myosin oscillation, which we show to be regulated by both the CaM-MLCK and Rho1-Rok pathways. Together, our results support a model that, beginning at stage 9 of oogenesis, growth-induced mechanical pressure serves as a developmental cue to initiate periodic basal myosin oscillations through the function of the mechanosensing calcium channel, TRPM, to drive tissue elongation.

Keywords:  Drosophila oogenesis; TRPM; calcium influx; germline tissue; mechanoreception; morphogenesis; myosin II; myosin oscillation; somatic follicle cells; tissue elongation

DOI:  https://doi.org/10.1016/j.cub.2025.10.038
Adv Sci (Weinh). 2025 Nov 18. e09682

5-Hydroxymethylcytosine Dynamics Reveals Coordinated Reprogramming of Parental Genomes and X Chromosome Dosage Balance in Mouse SCNT Embryos.

Zeming Xiang, Rui Yan, Jing Guo, Mengyao Wang, Xin Cheng, Fan Zhang, Tianzi Guo, Xin Long, Fan Guo, Dan Liang.

  Somatic cell nuclear transfer (SCNT) embryos exhibit widespread epigenetic defects, particularly aberrant DNA methylation. DNA 5-hydroxymethylcytosine (5hmC) is involved in methylation reprogramming during early embryonic development, yet its role in SCNT embryos remains largely unknown. Here, the genome-wide 5hmC landscapes in mouse SCNT embryos are systematically profiled with parental allele specificity. It is revealed that both maternal and paternal genomes of donor somatic cells acquire a transient, sperm-like but attenuated and allele symmetric distribution of 5hmC at the 2-cell stage, distinct from the parental asymmetric pattern observed in naturally fertilized eggs. This is characterized by insufficient DNA hydroxymethylation of the X chromosome in female SCNT embryos, as well as resistance to 5hmC-associated DNA demethylation at germline imprinting control regions (gICRs). While de novo 5hmC generation is closely associated with initial DNA demethylation during somatic-to-zygotic transition, it later becomes uncoupled from ongoing methylation changes. Importantly, global elevation of 5hmC via Tet3 overexpression leads to premature activation of developmental genes at the 2-cell stage and severely impairs SCNT embryo development. These findings reveal unique dynamics and functional consequences of abnormal 5hmC remodeling in SCNT embryos, highlighting the precise regulation of 5hmC generation as a key epigenetic event for successful mammalian cloning.

Keywords:  5‐hydroxymethylcytosine; embryonic development; epigenetic barrier; somatic cell nuclear transfer

DOI:  https://doi.org/10.1002/advs.202509682
Cell Death Dis. 2025 Nov 17. 16(1): 841

Loss of full-length DAZL isoform disrupts PABPC1-dependent translational regulation and meiosis.

Xin Li, Dandan Cao, Yue Lu, Zexin Bian, Tingting Zhao, Wenbo Liu, Yan Zhao, Jun Tan, Lei Li, Eugene Yujun Xu.

Alternative splicing (AS) events are exceptionally active during spermatogenesis, enhancing the diversity of the testicular transcriptome and proteome. In mouse testes, the germ cell-specific RNA-binding protein DAZL undergoes alternative splicing to produce two isoforms: a full-length DAZL (DAZL_FL) and a short isoform lacking exon 8 (DAZL_Sh). While DAZL is a hallmark of germ cell development, the physiological roles of its alternative splicing, and the distinct functions of these two isoforms remain yet to be fully elucidated. To investigate this, we disrupted alternative splicing of Dazl by generating DAZL short isoform only mice via deletion of the DAZL exon 8 and found that the resulting loss of DAZL_FL led to male infertility, characterized by extensive spermatocyte apoptosis and arrest of spermatid development. Ribosome profiling (Ribo-seq) revealed that loss of DAZL_FL downregulated the translation of meiotic genes specifically bound by DAZL. Mechanistically, DAZL_Sh failed to interact with Poly(A) Binding Protein Cytoplasmic 1 (PABPC1), resulting in impaired translation of DAZL-targeted germ cell transcripts. In females, DAZL_FL ablation caused complete infertility, marked by massive primordial follicle apoptosis and failure of primary follicle recruitment, highlighting a shared role for DAZL_FL in meiotic regulation in both sexes. Our findings established DAZL/PABPC1 complex formation as a pivotal mechanism controlling meiotic progression. By functionally dissecting DAZL isoforms, we uncovered a critical role of Dazl alternative splicing during spermatogenesis and folliculogenesis, further expanding the roles of DAZL in germ cell development and thereby providing novel genetic causes and potential therapeutic targets for azoospermia and primary ovarian insufficiency.

DOI: https://doi.org/10.1038/s41419-025-08179-7
J Cell Physiol. 2025 Nov;240(11): e70110

Mitochondrial and Glucose Metabolic Patterns in Pre-Granulosa Cells and Oocytes and Their Dysfunctions Induce Impaired Primordial Follicle Formation in Mice.

Yutong Yan, Wenhui Ma, Yanxue Li, Jiaqi Li, Xiaoe Zhao, Qiang Wei, Sha Peng, Menghao Pan, Baohua Ma.

  In mammals, the establishment of primordial follicles (PFs) occurs in an orderly manner and is an energy-demanding process. However, the mechanisms underlying the supply and demand of energy metabolism during primordial follicle formation, particularly glycolysis and oxidative phosphorylation (OXPHOS) signaling, remain poorly understand. Herein, based on the analyses of single-cell RNA sequencing (scRNA-seq) data from mouse ovarian tissues, gene expression associated with glycolysis and OXPHOS signaling were dynamically changed along pseudotime trajectory in pre-granulosa (PG) cells and oocytes following cell development and PF formation. The molecules related to glycolysis and OXPHOS signaling exhibited dynamic expression patterns in mouse ovarian tissues following PF formation, with distinct expression levels and location in somatic cells and oocytes. The dysfunctions of mitochondrial and glucose metabolic patterns using glycolysis inhibitor (2-Deoxy-Dglucose, 2-DG) or OXPHOS signaling inhibitor (metformin, MET) significantly inhibited PF formation, disordered oocyte development, downregulated key gene expression, impaired the recruitment and maintenance of PG cells, and altered cell proliferation and apoptosis. Collectively, these results demonstrate that cellular metabolic patterns are diverse and dynamically regulate in oocytes and PG cells during PF formation of mice, and glucose metabolism is essential for PF formation and its disruption inhibits PF formation.

Keywords:  glucose metabolism; glycolysis; mouse; oxidative phosphorylation; primordial follicle formation

DOI:  https://doi.org/10.1002/jcp.70110
bioRxiv. 2025 Oct 01. pii: 2025.09.29.679218. [Epub ahead of print]

A mechanical origin for implantation defects in embryos from aged females.

Kate E Cavanaugh, M J Franco-Oñate, Diana J Laird, Patrick W Oakes, Ricard Alert, Orion D Weiner.

Women over 35 experience a marked reduction in fertility. The origin of these fertility defects appears to reside in the implantation capacity of the embryo itself, but the mechanistic basis of this impairment is not well-understood. Here, we identify a core mechanical defect in embryos from aged mothers that impairs the process of implantation. Using mouse models, we find that reproductive aging yields increased contractility in the extra-embryonic trophectoderm, the outer epithelial tissue responsible for mediating uterine attachment and embryo implantation. This hypercontractile state elevates tissue surface tension and viscosity in the blastocyst, culminating in defective spreading during implantation. Enhanced contractility is necessary and sufficient for this age-related defect in implantation, and early embryo mechanics can be used to predict successful implantation for embryos from both young and aged mothers. Our work represents a potential foundation for improving embryo selection in Assisted Reproductive Technologies to resolve age-related defects in female fertility.

DOI: https://doi.org/10.1101/2025.09.29.679218
Sci Adv. 2025 Nov 21. 11(47): eady6402

Capturing aberrant cell behaviors producing defects in human embryos via live imaging.

Hiroki Akizawa, Ana Domingo-Muelas, Maria Pardo-Figuerez, Blake Hernandez, Goli Ardestani, Robin M Skory, Marta Venturas, Piotr Tetlak, Stephanie Bissiere, Denny Sakkas, Carlos Simon, Nicolas Plachta.

The generation of human embryos in vitro has revolutionized reproductive medicine, and also made it possible to study fundamental aspects of early human development. However, human preimplantation embryos often display an array of morphological defects associated with poor development and implantation. Here, we used live-embryo imaging and computational analysis to capture how these defects can be produced in real time. We record various forms of mitotic errors including lagging chromosomes producing micronuclei, multipolar spindles causing abnormal chromosome organization recapitulated by daughter cells, and uncontrolled scattering of condensed chromosomes. In addition, we capture abnormal cleavage furrow dynamics during cytokinesis producing binucleated and enucleated cells. Finally, we find cells with disrupted mitotic progression ultimately leading to blebbing and fragmentation. Thus, these results document specific aberrant cell behaviors producing morphological defects in real time, and indicate that errors during mitosis and cytokinesis represent a major cause of developmental failures in human embryos.

DOI: https://doi.org/10.1126/sciadv.ady6402
EMBO J. 2025 Nov 18.

CRISPR-RfxCas13d screening uncovers Bckdk as a post-translational regulator of maternal-to-zygotic transition in teleosts.

Luis Hernández-Huertas, Ismael Moreno-Sánchez, Jesús Crespo-Cuadrado, Ana Vargas-Baco, Gabriel da Silva Pescador, Ying Zhang, Zhihui Wen, Laurence Florens, José M Santos-Pereira, Ariel A Bazzini, Miguel A Moreno-Mateos.

  The maternal-to-zygotic transition (MZT) is a reprograming process encompassing zygotic genome activation (ZGA) and the clearance of maternally-provided mRNAs. While some factors regulating MZT have been identified, there are thousands of maternal RNAs whose function has not been ascribed yet. Here, we have performed a proof-of-principle CRISPR-RfxCas13d maternal screen, in which we targeted mRNAs encoding kinases and phosphatases or proteins regulating them in zebrafish. This screen identified branched-chain ketoacid dehydrogenase kinase, Bckdk, as a novel post-translational regulator of MZT. Bckdk mRNA knockdown caused epiboly defects, ZGA deregulation, H3K27ac reduction and a partial impairment of miR-430 processing. Phospho-proteomic analysis revealed that Phf10/Baf45a, a chromatin remodeling factor, is less phosphorylated upon Bckdk depletion. Further, phf10 mRNA knockdown also altered ZGA, and expression of a phospho-mimetic mutant of Phf10 rescued the developmental defects observed after bckdk mRNA depletion, as well as restored H3K27ac levels. Altogether, our results demonstrate the competence of CRISPR-RfxCas13d screenings to uncover new regulators of early vertebrate development and shed light on the post-translational control of MZT mediated by protein phosphorylation.

Keywords:  Bckdk; CRISPR-RfxCas13d; Kinases; MZT; Zebrafish

DOI:  https://doi.org/10.1038/s44318-025-00617-8