bims-cebooc 2025-07-20 papers

bims-cebooc

Biomed News

on Cell biology of oocytes

Issue of 2025–07–20
thirty papers selected by
Gabriele Zaffagnini, Universität zu Köln

Spindle checkpoint can secure additional cheating time for selfish expanded centromeres.
The proteostatic landscape of healthy human oocytes.
Asynchronous mouse embryo polarization leads to heterogeneity in cell fate specification.
ZSCAN4 functions as a safeguard to maintain centromere integrity during oocyte meiosis.
Decoding protein phosphorylation during oocyte meiotic divisions using phosphoproteomics.
Female-germline specific protein Sakura interacts with Otu and is crucial for germline stem cell renewal and differentiation and oogenesis.
Clonal analysis reveals differential PGC contributions to the early germline and ovarian reserve.
Fertility is compromised after oocyte-specific deletion of microtubule severing protein katanin A1.
Spindle-localized F-actin regulates polar MTOC organization and the fidelity of meiotic spindle formation.
Sequential action of the nuclear Argonautes HRDE-1 and NRDE-3 promotes global transcriptional silencing during starvation in the nascent C. elegans germline.
Multiple domains of scaffold Tudor protein play nonredundant roles in Drosophila germline.
Ovulation: A cellular symphony in three movements.
The ORB2 RNA-binding protein represses translation of its target transcripts during the Drosophila maternal-to-zygotic transition via its functionally conserved Zinc-binding 'ZZ' domain.
Centromere regulation in the germline and early embryo.
CRISPR-based screening identifies the role of KRAB-containing transcription factors ZIM3 and ZNF394 in human major zygotic genome activation.
The fantastic voyage: primordial germ cell migration through the developing mouse embryo.
MEIOC prevents continued mitotic cycling and promotes meiotic entry during mouse oogenesis.
Single-nucleotide Resolution Epitranscriptomic Profiling Uncovers Dynamic m 6 A Regulation in Bovine Preimplantation Development.
Glucose enrichment accelerates C. elegans reproductive aging via non-autonomous DAF-2/insulin-like receptor signaling in somatic tissues.
Patched regulates cell cycle and tissue architecture in C. elegans gonad.
C. elegans sperm and oocytes differentially transmit diet-induced adaptations to their progeny.
Re-establishment of H3K9me2 eliminates the transcriptional inhibition of ST18 on meiotic genes and orchestrates female germ cell development.
The LOTUS domain of Oskar promotes localisation of both protein and mRNA components of Drosophila germ plasm.
Phase separation of PGL-3 driven by structured domains that oligomerize and interact with terminal RGG motifs.
Chinmo is a novel regulator of differential Hippo signaling response within a single developing organ.
A pre-menopausal single-cell atlas for ovarian drug discovery.
Non-autonomy of age-related morphological changes in the C. elegans germline stem cell niche.
Systematic characterization of the ovarian landscape across mouse menopause models.
Why and how paternal mitochondrial DNA gets cut out of the inheritance.
The Somatic Impact on Inheritance and the Germline Control of the Soma.

Curr Biol. 2025 Jul 08. pii: S0960-9822(25)00813-9. [Epub ahead of print]

Spindle checkpoint can secure additional cheating time for selfish expanded centromeres.

R Zaak Walton, Sebastian J Khan, Warif El Yakoubi, Takashi Akera.

  Expanded centromeric satellite repeats can violate Mendel's law of segregation by preferentially segregating to the egg. In mice, these selfish centromeres enrich microtubule destabilizers at pericentromeres to detach from the spindle and flip toward the egg side of the meiotic spindle, thereby achieving preferential segregation. However, despite the consistent enrichment of destabilizers upon centromere expansion, such enrichment alone is insufficient to drive the preferential retention of expanded centromeres, suggesting a missing component in understanding their non-Mendelian segregation. Here, we propose that prolonged spindle checkpoint activation is crucial for expanded centromeres to cheat the segregation process by providing sufficient time for them to flip toward the egg side. By experimentally manipulating kinetochore size in a species-specific manner, we found that assembling larger kinetochores triggers robust spindle checkpoint activation, leading to anaphase delay and preferential retention of expanded centromeres in the egg. Comparisons across multiple hybrid mouse models revealed that centromeric satellite asymmetry does not consistently lead to kinetochore asymmetry and anaphase delay, explaining why satellite asymmetry does not always result in the preferential retention of larger centromeres. Altogether, this work highlights the significance of checkpoint activation in exploiting the inherent asymmetry in female meiosis and the distinct responses of kinetochore proteins and microtubule destabilizers to centromere expansion.

Keywords:  centromere; centromere drive; chromosome segregation; female meiosis; kinetochore; meiotic drive; mouse oocyte; spindle checkpoint

DOI:  https://doi.org/10.1016/j.cub.2025.06.056
EMBO J. 2025 Jul 16.

The proteostatic landscape of healthy human oocytes.

Gabriele Zaffagnini, Miquel Solé, Juan Manuel Duran, Nikolaos P Polyzos, Elvan Böke.

  Oocytes, female germ cells that develop into eggs, are among the longest-lived cells in the animal body. Recent studies on mouse oocytes highlight unique adaptations in protein homeostasis (proteostasis) within these cells. However, the mechanisms of proteostasis in human oocytes remain virtually unstudied. We present the first large-scale study of proteostatic activity in human oocytes using over 100 freshly donated oocytes from 21 healthy women aged 19-34 years. We analysed the activity and distribution of lysosomes, proteasomes, and mitochondria in both immature and mature oocytes. Notably, human oocytes exhibit nearly twofold lower proteolytic activity than surrounding somatic cells, with further decreases as oocytes mature. Oocyte maturation is also coupled with lysosomal exocytosis and a decrease in mitochondrial membrane potential. We propose that reduced organelle activity preserves key cellular components critical for early embryonic development during the prolonged maturation of human oocytes. Our findings highlight the distinctive biology of human oocytes and the need to investigate human-specific reproductive biology to address challenges in female fertility.

Keywords:  Female Fertility; Human Oocytes; Lysosomes; Mitochondria; Proteostasis

DOI:  https://doi.org/10.1038/s44318-025-00493-2
bioRxiv. 2025 Jun 23. pii: 2024.07.26.605266. [Epub ahead of print]

Asynchronous mouse embryo polarization leads to heterogeneity in cell fate specification.

Adiyant Lamba, Meng Zhu, Maciej Meglicki, Sylwia Czukiewska, Lakshmi Balasubramaniam, Ron Hadas, Nina Weishaupt, Ekta M Patel, Yu Hua Kavanagh, Ran Wang, Naihe Jing, Magdalena Zernicka-Goetz.

The first lineage allocation in mouse and human embryos separates the inner cell mass (ICM) from the outer trophectoderm (TE). This symmetry breaking event is executed through polarization of cells at the 8-cell stage and subsequent asymmetric divisions, generating polar (TE) and apolar (ICM) cells. Here, we show that embryo polarization is unexpectedly asynchronous. Cells polarizing at the early and late 8-cell stage have distinct molecular and morphological properties that direct their following lineage specification, with early polarizing cells being biased towards producing the TE lineage. More recent studies have also implicated heterogeneities between cells prior to the 8-cell stage in the first lineage allocation: cells exhibiting reduced methyltransferase CARM1 activity at the 4-cell stage are predisposed towards the TE fate. Here, we demonstrate that reduced CARM1 activity and upregulation of its substrate BAF155 promote early polarization and TE specification. These findings provide a link between asymmetries at the 4-cell stage and polarization at the 8-cell stage, mechanisms of the first lineage allocation that had been considered separate.

DOI: https://doi.org/10.1101/2024.07.26.605266
Genome Biol. 2025 Jul 15. 26(1): 204

ZSCAN4 functions as a safeguard to maintain centromere integrity during oocyte meiosis.

Da Yi Choi, Jiyeon Leem, Crystal Lee, Jeong Su Oh.

   BACKGROUND: Centromeres play a vital role in ensuring accurate chromosome segregation during meiosis by serving as the foundation for kinetochore assembly and microtubule attachment. In oocytes, maintaining centromere integrity is particularly critical due to the extended arrest period prior to meiotic resumption. However, the molecular safeguards that preserve centromere structure and function throughout oocyte maturation remain poorly understood.
RESULTS: Here, we identify ZSCAN4 as an essential regulator of centromere integrity during mouse oocyte meiosis. ZSCAN4 depletion leads to a marked reduction in key centromeric and kinetochore proteins, including CENP-A, accompanied by aberrant centromere stretching under spindle tension. Mechanistically, ZSCAN4 promotes pericentromeric H3K9me3 enrichment, facilitating proper chromatin compaction and chromosome alignment. Moreover, ZSCAN4 contributes to genomic stability by mediating the chromosomal recruitment of the CIP2A complex in response to DNA damage during meiotic progression.
CONCLUSIONS: These findings establish ZSCAN4 as a critical factor in preserving centromere structure and function during oocyte meiosis, with potential implications for female reproductive health and developmental competence.

Keywords:  Centromere; Meiosis; Oocytes; SMC family; ZSCAN4

DOI:  https://doi.org/10.1186/s13059-025-03687-3
Elife. 2025 Jul 17. pii: RP104255. [Epub ahead of print]13

Decoding protein phosphorylation during oocyte meiotic divisions using phosphoproteomics.

Leonid Peshkin, Enrico Maria Daldello, Elizabeth S Van Itallie, Matthew Sonnett, Johannes Kreuzer, Wilhelm Haas, Marc W Kirschner, Catherine Jessus.

  Oocyte meiotic divisions represent a critical process in sexual reproduction, as a diploid non-dividing oocyte is transformed into a haploid fertilizable egg, as a prelude for the subsequent embryonic divisions and differentiation. Although cell differentiation and proliferation are governed by transcription, oocyte maturation and early embryonic divisions depend entirely on changes in protein abundance and post-translational modifications. Here, we analyze the abundance and phosphorylation of proteins during Xenopus oocyte meiotic maturation. We reveal significant shifts in protein stability, related to spindle assembly, DNA replication, and RNA-binding. Our analysis pinpoints broad changes in phosphorylation correlating with key cytological meiotic milestones, noteworthy changes in membrane trafficking, nuclear envelope disassembly, and modifications in microtubule dynamics. Additionally, specific phosphorylation events target regulators of protein translation, Cdk1 and the Mos/MAPK pathway, thereby providing insight into the dynamics of Cdk1 activity, as related to the meiotic cell cycle. This study sheds light on the orchestration of protein dynamics and phosphorylation events during oocyte meiotic divisions, providing a rich resource for understanding the molecular pathways orchestrating meiotic progression in the frog, and most likely applicable to other vertebrate species.

Keywords:  biochemistry; cell biology; chemical biology; meiotic maturation; oocyte; phosphoproteome; xenopus

DOI:  https://doi.org/10.7554/eLife.104255
Elife. 2025 Jul 15. pii: RP103828. [Epub ahead of print]13

Female-germline specific protein Sakura interacts with Otu and is crucial for germline stem cell renewal and differentiation and oogenesis.

Azali Azlan, Li Zhu, Ryuya Fukunaga.

  During oogenesis, self-renewal and differentiation of germline stem cells (GSCs) must be tightly regulated. The Drosophila female germline serves as an excellent model for studying these regulatory mechanisms. Here, we report that a previously uncharacterized gene CG14545, which we named sakura, is essential for oogenesis and female fertility in Drosophila. Sakura is predominantly expressed in the ovaries, particularly in the germline cells, including GSCs. sakura null mutant female flies display rudimentary ovaries with germline-less and tumorous phenotypes, fail to produce eggs, and are completely sterile. The germline-specific depletion of sakura impairs Dpp/BMP signaling, leading to aberrant bag-of-marbles (bam) expression, resulting in faulty differentiation and loss of GSCs. sakura is also necessary for normal levels of piwi-interacting RNAs (piRNAs) levels and for female-specific splicing of sex-lethal (sxl), a master regulator of sex identity determination. We identified Ovarian Tumor (Otu) as a protein binding partner of Sakura and found that loss of otu phenocopies loss of sakura in ovaries. Thus, we identify Sakura as a crucial factor for GSC renewal and differentiation and oogenesis, and propose that Sakura and Otu function together in these processes.

Keywords:  D. melanogaster; cell biology; developmental biology; fertility; germline stem cell; oogenesis; ovarian tumor; ovary

DOI:  https://doi.org/10.7554/eLife.103828
bioRxiv. 2025 May 07. pii: 2025.04.30.651497. [Epub ahead of print]

Clonal analysis reveals differential PGC contributions to the early germline and ovarian reserve.

Maya Pahima, Florence L Marlow.

Primordial germ cells (PGCs) are the precursors of the germline and among the first cells to be specified during embryogenesis. Contrary to the common assumption that PGCs directly develop into germline stem cells (GSCs), recent mammalian data and our zebrafish observations suggest a more complex picture. We hypothesized that individual PGCs contribute differentially to gonad development. To test this hypothesis, we developed two Cre-based lineage tracing systems and demonstrate that PGCs give rise to at least four distinct clone types in zebrafish. We observed no restriction in clone type localization along the anterior-posterior axis, suggesting these differences are PGC intrinsic or locally determined. Further examination of the ovarian reserve revealed functional evidence that some PGCs generate self-renewing GSCs, while others produce non-renewing progenitors that are depleted with successive matings. Collectively, our findings propose a revised model of vertebrate germline establishment with implications to reproductive lifespan. This model suggests that differentiation potential varies among PGCs, allowing individual PGCs to directly differentiate into multiple distinct germ cell types, including renewing GSCs and transient populations that contribute to an early wave of gametes.

DOI: https://doi.org/10.1101/2025.04.30.651497
Mol Hum Reprod. 2025 Jul 16. pii: gaaf034. [Epub ahead of print]

Fertility is compromised after oocyte-specific deletion of microtubule severing protein katanin A1.

Wai Shan Yuen, Qing-Hua Zhang, Monique Dunstan, Deepak Aidhikari, Anne E O'Connor, Jessica Em Dunleavy, Moira K O'Bryan, John Carroll.

  Katanins are microtubule severing enzymes that play roles in diverse cell functions including meiotic and mitotic spindle formation. To address the role of Katanin p60 isozymes in mammalian oocytes, we have used the ZP3-CreLox approach to specifically delete Katanin A1 (KATNA1) and Katanin A-Like 1 (KATNAL1) from the start of oocyte growth. Here, we show that KATNAL1 is not required for normal fertility, but that deletion of KATNA1 causes a 50% decrease in fertility. Further investigation in Katna1 -/- oocytes revealed no effect on MI spindle morphology but a modest effect on the morphology of MII spindles. This was accompanied by a decreased rate of fertilization, but Katna1 -/+ heterozygous embryos that reached the 2-cell stage developed at normal rates to the blastocyst stage. Parthenogenetic activation of Katna1 -/- oocytes to generate diploid homozygous embryos revealed a reduced rate of blastocyst formation. Further, the Katna1 -/- parthenogenetic blastocysts had a reduced diameter, decreased cell number, and increased nuclear size. Taken together, our data indicates KATNA1, but not KATNAL1, plays a role in MII spindle function and mitotic cell divisions of the preimplantation embryo. The ability of the paternal allele to rescue preimplantation development suggests the origin of the decrease in the fertility of conditional Katna1 -/- mice lies in abnormalities arising in the egg to embryo transition prior to embryonic genome activation.

Keywords:  Oocyte; early embryogenesis; female fertility; meiosis; microtubules; spindle

DOI:  https://doi.org/10.1093/molehr/gaaf034
bioRxiv. 2025 May 11. pii: 2025.05.07.652730. [Epub ahead of print]

Spindle-localized F-actin regulates polar MTOC organization and the fidelity of meiotic spindle formation.

Edgar J Soto-Moreno, Nourhan N Ali, Florian Küller, Veselin Nasufovic, Michaela Frolikova, Olga Tepla, Jaromir Masata, Dirk Trauner, Amanda A Patterson, Hans-Dieter Arndt, Katerina Komrskova, Magdalena Zernicka-Goetz, David M Glover, Ahmed Z Balboula.

Mammalian oocytes are notoriously prone to chromosome segregation errors leading to aneuploidy. The spindle provides the machinery for accurate chromosome segregation during cell division. Mammalian oocytes lack centrioles and, therefore, the meiotic spindle relies on the organization of numerous acentriolar microtubule organizing centers into two poles (polar MTOCs, pMTOCs). The traditional view is that, in mammalian oocytes, microtubules are the sole cytoskeletal component responsible for regulating pMTOC organization and spindle assembly. We identified a novel F-actin pool that surrounds pMTOCs, forming F-actin cage-like structure. We demonstrated that F-actin localization on the spindle depends on unconventional myosins X and VIIb. Selective disruption of spindle-localized F-actin, using myosin X/VIIb knockdown oocytes or photoswitchable Optojasp-1, perturbed pMTOC organization, leading to unfocused spindle poles and chromosome missegregation. Here, we unveil an important function of F-actin in regulating pMTOC organization, a critical process for ensuring the fidelity of meiotic spindle formation and proper chromosome segregation.

DOI: https://doi.org/10.1101/2025.05.07.652730
bioRxiv. 2025 Jun 25. pii: 2025.06.25.661390. [Epub ahead of print]

Sequential action of the nuclear Argonautes HRDE-1 and NRDE-3 promotes global transcriptional silencing during starvation in the nascent C. elegans germline.

Emilie Chien, Mezmur D Belew, W Matthew Michael.

In C. elegans , if embryos hatch into an environment lacking nutrients the primordial germ cells (PGCs) will arrest mRNA transcription and enter quiescence until food becomes available. Our previous work had shown that the global transcriptional silencing (GTS) that occurs in PGCs during L1 starvation requires a "hyperdeposition" of the repressive histone mark H3K9me3 in germline chromatin. Hyperdeposition is defined as an increase in the amount of H3K9me3 embedded in germline chromatin, relative to neighboring somatic nuclei. Hyperdeposition initiates in embryonic PGCs and is maintained in starved L1s. Here, we show that the nuclear RNAi pathway is responsible for both initiation and maintenance of H3K9me3 hyperdeposition. Interestingly, both known nuclear Argonautes, HRDE-1 and NRDE-3, play a role in hyperdeposition and they do so in a sequential manner. We show that HRDE-1 acts in embryonic PGCs to initiate hyperdeposition and then, at the embryo-to-L1 transition, HRDE-1 becomes dispensable and NRDE-3 is required to maintain H3K9me3 levels, and for GTS. We also examine the timing of H3K9me3 hyperdeposition and find that it initiates soon after germline zygotic genome activation (ZGA) occurs. Our data suggest a model where ZGA promotes both gene expression and H3K9me3 deposition at active loci, and under starvation conditions these H3K9me3 marks are employed to silence the germline genome.

DOI: https://doi.org/10.1101/2025.06.25.661390
Life Sci Alliance. 2025 Oct;pii: e202503304. [Epub ahead of print]8(10):

Multiple domains of scaffold Tudor protein play nonredundant roles in Drosophila germline.

Samuel J Tindell, Alyssa G Boeving, Julia Aebersold, Alexey L Arkov.

Scaffold proteins play crucial roles in subcellular organization and function. In many organisms, proteins with multiple Tudor domains are required for the assembly of membraneless RNA-protein organelles (germ granules) in germ cells. Tudor domains are protein-protein interaction modules which bind to methylated polypeptides. Drosophila Tudor protein contains 11 Tudor domains, which is the highest number known in a single protein. The role of each of these domains in germ cell formation has not been systematically tested, and it is not clear if some domains are functionally redundant. Using CRISPR methodology, we generated mutations in several uncharacterized Tudor domains and showed that they all caused defects in germ cell formation. Mutations in individual domains affected Tudor protein differently, causing reduction in protein levels and defects in subcellular localization and in the assembly of germ granules. Our data suggest that multiple domains of Tudor protein are all needed for efficient germ cell formation, highlighting the rational for keeping many Tudor domains in protein scaffolds of biomolecular condensates in Drosophila and other organisms.

DOI: https://doi.org/10.26508/lsa.202503304
Semin Cell Dev Biol. 2025 Jul 12. pii: S1084-9521(25)00044-8. [Epub ahead of print]174 103634

Ovulation: A cellular symphony in three movements.

Christopher Thomas.

  Ovulation is a complex and tightly regulated process essential for mammalian reproduction. It involves the coordinated, tissue-scale remodelling of the ovulatory follicle, culminating in the release of a fertilisation-competent egg. Ovulation is triggered by external hormonal cues: rising levels of follicle-stimulating hormone (FSH), followed by a surge in luteinising hormone (LH) from the anterior pituitary. These cues initiate a cascade of downstream events driven by follicle-derived signals, including epidermal growth factor (EGF) and progesterone, which propagate the ovulatory response. Recent advances using ex vivo follicle culture and live imaging in mouse follicles have revealed ovulation as a stepwise, self-contained programme characterised by dynamic spatial and temporal coordination. Notably, the oocyte remains largely stationary during most of ovulation, only moving toward the rupture site minutes before its release. This finding emphasises that ovulation is not defined by egg release alone, but by a prolonged and tightly regulated sequence of cellular and tissue-level events. This review presents ovulation through a temporal framework, metaphorically structured as a symphony performed by the four major follicular cell types. Beginning with an FSH-driven prelude, the symphony progresses through three movements: LH-induced initiation and meiotic resumption; progesterone-driven late events; and finally, follicle rupture and oocyte release. Together, this framework offers a new lens to understand ovulation as a developmental performance marking the transition from reproductive readiness to potential fertilisation and new life.

Keywords:  Actomyosin contraction; Corpus; Cumulus expansion; Epidermal growth factor (EGF); Extracellular matrix (ECM) remodelling; Follicle rupture; Follicle-stimulating hormone (FSH); Folliculogenesis; Granulosa cells; Hyaluronic acid; Luteinising, hormone (LH); Luteum; Meiosis; Oogenesis; Ovarian follicle; Ovulation; Progesterone signalling

DOI:  https://doi.org/10.1016/j.semcdb.2025.103634
bioRxiv. 2025 Jul 13. pii: 2025.07.10.664187. [Epub ahead of print]

The ORB2 RNA-binding protein represses translation of its target transcripts during the Drosophila maternal-to-zygotic transition via its functionally conserved Zinc-binding 'ZZ' domain.

Timothy C H Low, Hua Luo, Chalini Weerasooriya, Sichun Lin, Stephane Angers, Craig A Smibert, Howard D Lipshitz.

RNA-binding proteins (RBPs) are key components of the post-transcriptional regulatory machinery. We show that the ORB2 RBP, the Drosophila ortholog of human Cytoplasmic Polyadenylation Element Binding Protein (hCPEB) 2-4 protein family, binds to hundreds of maternally provided mRNAs in early embryos, identify a U-rich motif enriched in ORB2's targets, and show that this motif confers ORB2 binding and repression to a luciferase reporter mRNA in S2 tissue culture cells. ORB2's target transcripts are translationally repressed and unstable during the maternal-to-zygotic transition (MZT), a developmental phase during which a large proportion of maternally provided mRNAs are repressed and cleared. We show that, when tethered to a luciferase reporter, ORB2 and hCPEB2 (but not ORB and hCPEB1) repress translation and that the C-terminal Zinc-binding ('ZZ') domain of ORB2 is necessary and sufficient for repression. ORB2 interacts with a suite of post-transcriptional regulators in early embryos; a subset of these interactions is lost upon deletion of the ZZ domain, notably with the Cup repressive complex. Analysis of the early embryo's translatome in the presence or absence of the endogenous ZZ domain, shows that ORB2's targets move onto polysomes upon ZZ domain deletion, indicating that this domain mediates translational repression of ORB2's targets during the MZT. Together, our results assign a function to the ZZ domain and support a significant role for ORB2 in post-transcriptional regulation of maternal mRNAs during the Drosophila MZT.
ARTICLE SUMMARY: We show that Drosophila ORB2, the ortholog of the human CPEB2 RNA-binding protein, represses translation of its target mRNAs during the maternal-to-zygotic transition via its C-terminal Zinc-binding ('ZZ') domain.

DOI: https://doi.org/10.1101/2025.07.10.664187
Curr Opin Genet Dev. 2025 Jul 10. pii: S0959-437X(25)00071-1. [Epub ahead of print]94 102379

Centromere regulation in the germline and early embryo.

Marta Grzonka, Ben E Black, Michael A Lampson.

Centromeres are essential for genome inheritance, serving as sites for kinetochore assembly and for final sister chromatid cohesion to ensure accurate chromosome segregation during cell division. These roles must persist through radical physical changes to chromosomes and other biological challenges presented by specialized processes in the germlines of both sexes and during early embryonic development. Centromeres in most organisms are epigenetically defined by the presence of a histone H3 variant, CENP-A. Therefore, to maintain centromeres, CENP-A nucleosomes must be inherited across generations through the germline. However, unique aspects of gametogenesis, including asymmetric meiosis and prolonged cell cycle arrest in the female germline and extensive chromatin reorganization in the male germline, introduce additional layers of complexity to the process of centromere inheritance. Here, we review the implications of these processes for centromere regulation during gametogenesis and early embryonic development, drawing on findings from mouse and fruit fly models.

DOI: https://doi.org/10.1016/j.gde.2025.102379
Cell Rep. 2025 Jul 15. pii: S2211-1247(25)00786-7. [Epub ahead of print]44(8): 116015

CRISPR-based screening identifies the role of KRAB-containing transcription factors ZIM3 and ZNF394 in human major zygotic genome activation.

Jiayu Li, Liangfu Xie, Cheng Shi, Tiantian Zhang, Xiwen Lin, Haokun Da, Kongqianqian Sun, Chunsheng Han, Bing Zhu, Xi Chen, Hongkui Deng, Jun Xu.

  The initiation of major zygotic genome activation (ZGA) is crucial for human early embryogenesis. However, the transcription factors (TFs) regulating major ZGA in humans remain largely unknown. Here, we performed a CRISPR-based activation screen of 1,603 human TFs in human extended pluripotent stem cells (hEPSCs), which identified 132 candidates as potential regulators of major ZGA. Further evaluation of these candidates revealed that the KRAB-containing TFs ZIM3 and ZNF394 activated totipotent features in hEPSCs upon overexpression. Importantly, simultaneous knockdown of these two TFs arrested human embryo development prior to the eight-cell embryo stage. Mechanistically, the KRAB domains contributed to ZIM3- and ZNF394-mediated totipotency induction in vitro, accompanied by the suppression of a set of four-cell embryo enriched genes. Our study provided valuable resources for totipotency and major ZGA regulation, suggesting an un-reported role of KRAB-containing TFs in major ZGA in humans.

Keywords:  CP: Developmental biology; CP: Molecular biology; totipotency; transcription factors; zygotic genome activation

DOI:  https://doi.org/10.1016/j.celrep.2025.116015
Biochem Soc Trans. 2025 Jul 17. pii: BST20253009. [Epub ahead of print]

The fantastic voyage: primordial germ cell migration through the developing mouse embryo.

Katharine Goodwin.

  During the early stages of embryonic development, a small population of cells is set aside to form the germline. These primordial germ cells (PGCs) are often specified separate in time and space from their eventual home, the developing gonads. PGCs must therefore undertake a journey through the developing tissues of the embryo to reach their destination and ensure the fertility of the organism. Despite decades of interest in this topic and significant progress made in other model organisms, there is still very little known about how this migration is accomplished in the mouse or any other mammal. In this review, I explore over half a century of work examining this enigmatic cell and its voyage through the mouse embryo, interpreting these findings in light of recent discoveries in the field of cell migration. I discuss possible migration modes used by mouse PGCs, changes in their microenvironment that could influence migration, and roles the nucleus might play in their journey. With modern advances in microscopy and transgenic reporter mice, it is time to delve into this fascinating and important model of cell migration in vivo.

Keywords:  cell adhesion; cell migration; germ cells; mechanobiology; morphogenesis

DOI:  https://doi.org/10.1042/BST20253009
bioRxiv. 2025 Jun 15. pii: 2025.06.12.659330. [Epub ahead of print]

MEIOC prevents continued mitotic cycling and promotes meiotic entry during mouse oogenesis.

Esther G Ushuhuda, Jenniluyn T Nguyen, Natalie G Pfaltzgraff, Matthew Kofron, Maria M Mikedis.

In multicellular organisms, germ cells' transformation into haploid gametes requires that they transition from mitosis to meiosis, whereby they stop mitotic cycling and enter the meiotic cell cycle. In mammals, transcriptional activator STRA8-MEIOSIN mediates the decision to enter the meiotic cell cycle by triggering the G1-to-meiotic S phase transition. However, the molecular basis by which mammalian germ cells prevent continued mitotic cycling before entering the meiotic cell cycle remains unclear. Here, we investigate MEIOC's role in the mitosis-to-meiosis transition during mouse oogenesis by analyzing proliferation, cell cycle transcriptomics, and cell cycle-associated protein expression. MEIOC was previously shown to destabilize mRNA and repress the mitotic program after meiotic entry. Here, we demonstrate that MEIOC prevents continued mitotic cycling prior to meiotic entry in oogenic cells. We find that the mitosis-to-meiosis transition involves the repression of G1/S cyclin CCNA2 at the transcript and protein levels, and that MEIOC downregulates CCNA2 protein expression. In addition, MEIOC promotes entry into meiotic S phase by increasing Meiosin transcript abundance and consequently activating the STRA8-MEIOSIN transcription factor. Given that STRA8- MEIOSIN upregulates Meioc expression, MEIOC and STRA8-MEIOSIN form a positive feedback loop to reinforce timely meiotic initiation. We also demonstrate that BMP signaling halts mitotic cycling and promotes meiotic entry by upregulating MEIOC. We conclude that, in mouse oogenic cells, the transition from mitosis to meiosis occurs as two molecularly regulated steps- (i) halt of mitotic cycling and (ii) entry into the meiotic cell cycle - and that MEIOC modifies the cell cycle program to facilitate both steps in this transition.

DOI: https://doi.org/10.1101/2025.06.12.659330
bioRxiv. 2025 Jul 10. pii: 2025.07.07.663558. [Epub ahead of print]

Single-nucleotide Resolution Epitranscriptomic Profiling Uncovers Dynamic m 6 A Regulation in Bovine Preimplantation Development.

Rajan Iyyappan, Yichi Niu, Ming Hao, Kinga Pajdzik, Noah R Rakestraw, Piyush K Jain, Chuan He, Chenghang Zong, Zongliang Jiang.

RNA N 6 -methyladenosine (m 6 A) plays a crucial role in regulating gene expression during early embryonic development. However, the m 6 A dynamics at single-nucleotide resolution in preimplantation development remain uncharacterized, and the functional significance of site specific m 6 A modifications in key developmental regulators is largely unknown. Here, using SAC-seq, a single-base resolution, antibody-independent m 6 A profiling method, we generate the first comprehensive m 6 A landscape in bovine oocytes and preimplantation embryos. We identify a previously uncharacterized m 6 A site in RPL12 transcript that is essential for embryonic development. Loss of m 6 A at this site leads to reduced protein synthesis, disrupted expression of translation-related genes, and impaired zygotic genome activation and blastocyst formation. Notably, supplementation with wild-type RPL12 mRNA fails to rescue the developmental arrest, indicating that m 6 A regulation extends beyond transcript abundance. Our findings provide a valuable resource of m 6 A at single-nucleotide resolution in mammalian embryogenesis and uncover a critical mechanism by which precise, site-specific m 6 A regulates translation and developmental competence in early embryos.

DOI: https://doi.org/10.1101/2025.07.07.663558
bioRxiv. 2025 Jul 08. pii: 2025.07.04.663088. [Epub ahead of print]

Glucose enrichment accelerates C. elegans reproductive aging via non-autonomous DAF-2/insulin-like receptor signaling in somatic tissues.

Faria Athar, Emma J Houston, Emily Jewett, Nicole M Templeman.

Detrimental effects of chronic high-sugar overconsumption can extend from molecular and cellular responses to systemic changes. Reproductive systems are particularly sensitive to diet and energetic state, yet the long-term reproductive consequences of overnutrition are poorly defined. Here, we used Caenorhabditis elegans to study the impacts of glucose excess on reproductive aging. Glucose supplementation shortens C. elegans lifespan, and we found that it also hastens age-related reproductive decline, evidenced by a greater deterioration in oocyte quality and lower fertility with age. We next evaluated insulin-like signaling contributions, as this glucose-responsive pathway is well known to regulate both somatic aging and reproductive aging. Intriguingly, while 20 mM glucose enrichment still shortens the lifespan of daf-2(e1370) mutants, we found that it had no detrimental impact on their reproductive aging phenotypes. Using auxin-induced tissue-selective degradation, we discovered that DAF-2/insulin-like receptor signaling in C. elegans intestine and body wall musculature is required for glucose enrichment to exert damaging impacts on the reproductive system. However, suppressing insulin-like signaling in either of these tissues is sufficient to protect C. elegans against glucose-induced reproductive aging. These findings suggest that insulin-like signalling in metabolically active somatic tissues may represent a key link between overnutrition and reproductive aging.

DOI: https://doi.org/10.1101/2025.07.04.663088
bioRxiv. 2025 Jun 10. pii: 2025.06.09.657693. [Epub ahead of print]

Patched regulates cell cycle and tissue architecture in C. elegans gonad.

Johanna Kate Farley, Madeleine Schwalbe, Fredrik Forsberg, Aqilah Amran, Sandeep Gopal.

Hedgehog (Hh) signaling is essential for embryonic development and tissue homeostasis in several organisms. However, Caenorhabditis elegans lacks canonical Hh signaling due to the absence of key components, such as smoothened (SMO) and Hh ligands. Despite this, C. elegans retains Patched homologs, ptc-1 and ptc-3, which have specialized independent functions. Although ptc-1 is predominantly expressed in the gonads and ptc-3 in somatic tissues, we demonstrate that both genes are required to maintain germ cell populations and proper actin cytoskeletal architecture in the progenitor zone of the germline. Disruption of actin-regulating genes impairs germ cell cycle progression and reduces germ cell numbers, indicating that cytoskeletal integrity is critical for maintaining the germline. Furthermore, defects observed upon loss of Patched function are linked to disruptions in cholesterol metabolism. We show that the phenotypes observed in the gonads due to the loss of Patched function can be rescued by modulating dietary cholesterol. Together, our findings reveal a role for Patched receptors in regulating germline architecture and germ cell development indirectly through a cholesterol-sensitive pathway, offering insights into how metabolic cues influence the organization of complex tissues and cells.

DOI: https://doi.org/10.1101/2025.06.09.657693
Nat Commun. 2025 Jul 12. 16(1): 6457

C. elegans sperm and oocytes differentially transmit diet-induced adaptations to their progeny.

Alexandria B Pete, Craig P Hunter.

Non-genetic inheritance allows organisms to transmit recently acquired adaptive information to progeny to maximize fitness in response to environmental change. While Caenorhabditis elegans exhibits persistent multigenerational responses to transient stress, how non-genetic mechanisms respond to multigenerational environmental change remains largely unexplored. As a bacterivore exposed to diverse microbes, C. elegans offers a powerful model to study adaptation to a persistent environmental change. We measured reproductive fitness via hermaphrodite self-brood size and found that novel diets often caused 20-45% brood-size reductions compared to controls. However, animals adapt to the new diet producing normal-sized broods within 5 to 10 generations. However, these adapted animals often became maladapted to their previous diet but could re-adapt within a similar timeframe. This rapidity and reversibility, which was also observed in genetically identical isogenic lines, strongly suggest a non-genetic mechanism. Phenotypic analyses of maladapted animals revealed a correlation between specific diets and germline defects primarily affecting either sperm or oocytes. Crosses between differently adapted parents demonstrated that sperm primarily transmitted sperm adaptations and oocytes primarily transmitted oocyte adaptations. Together, these results highlight the critical role of non-genetic inheritance as a flexible and heritable mechanism enabling organisms to rapidly adapt to unpredictable environmental change.

DOI: https://doi.org/10.1038/s41467-025-61750-w
Nucleic Acids Res. 2025 Jul 08. pii: gkaf657. [Epub ahead of print]53(13):

Re-establishment of H3K9me2 eliminates the transcriptional inhibition of ST18 on meiotic genes and orchestrates female germ cell development.

Bing-Wang Zhao, Yi-Na Zhang, Tie-Gang Meng, Yuan-Hong Xu, Yi-Ke Lu, Si-Min Sun, Jia-Ni Guo, Xue-Mei Yang, Zhen-Bo Wang.

Epigenetic reprogramming is widespread and highly active during gametogenesis, which is usually involving in the expression of critical genes. The expression of genes couple with transcription activation, and the transcriptional regulation by transcription factors predetermine protein translation for biological processes. In this study, we found that EHMT1-mediated re-establishment of H3K9me2 played crucial roles in the progression of meiosis in female germ cells. EHMT1 deficient female mice were nearly infertile due to the arrest of zygotene in embryonic germ cells, which was caused by downregulated expression of key meiotic genes. Furthermore, we identified transcription suppressor, particularly ST18, for meiotic genes by combining RNA-seq, Cut&Tag seq analysis, and luciferase reporter assays. We uncovered that H3K9me2 mediated ST18 expression homeostasis and played critical roles in regulating the timed expression of key meiotic genes. Overall, we revealed that EHMT1-mediated H3K9me2 re-establishment facilitated the expression of key meiotic genes for female meiosis progression.

DOI: https://doi.org/10.1093/nar/gkaf657
bioRxiv. 2025 May 06. pii: 2025.05.02.651258. [Epub ahead of print]

The LOTUS domain of Oskar promotes localisation of both protein and mRNA components of Drosophila germ plasm.

Anastasia Repouliou, John R Srouji, Emily L Rivard, Andrés E Leschziner, Cassandra G Extavour.

Germ cells transmit genetic information to the next generation in multicellular organisms. In Drosophila melanogaster , germ cells are determined by germ plasm, a specialised cytoplasm assembled by the Oskar protein. The current view of the molecular mechanism of germ plasm assembly attributes recruitment of protein and mRNA germ plasm components to distinct domains of the Oskar protein, called the LOTUS and OSK domains respectively. However, most evidence for this model is based on in vitro studies. Here we test the ability of Oskar variants to assemble functional germ plasm in vivo . We found that Vasa recruitment was largely unperturbed by LOTUS deletion or mutations in vivo . In contrast, nanos and pgc mRNA recruitment was affected by LOTUS domain perturbations, despite the current model attributing mRNA recruitment to the distinct OSK domain. Taken together, these data suggest a revision of the prevailing modular view of Oskar's structure-function mechanism.

DOI: https://doi.org/10.1101/2025.05.02.651258
bioRxiv. 2025 Jun 24. pii: 2025.06.23.660947. [Epub ahead of print]

Phase separation of PGL-3 driven by structured domains that oligomerize and interact with terminal RGG motifs.

Rimpei Kuroiwa, Piyoosh Sharma, Andrea Putnam, Stephen D Fried, Geraldine Seydoux.

Phase separation of biomolecular condensates is often assumed to be driven by interactions involving nucleic acids and intrinsically disordered regions (IDRs) of proteins. PGL-3 is a component of P granules, biomolecular condensates in the C. elegans germline, that contains two structured domains in tandem (D1-D2), an internal IDR, and a C-terminal IDR rich with RGG motifs. Theoretical and in vitro studies have implicated the internal IDR and RGG motifs in driving PGL-3 phase separation via self-interactions and binding to RNA. Studies in cells, however, have implicated the D1 and D2 domains. Here, we investigate the molecular basis of PGL-3 phase separation in vitro using microscopy, crosslinking mass spectrometry and biophysical measurements. We find that D1-D2 is oligomeric and necessary and sufficient for phase separation independent of RNA. D1-D2 also interacts with the terminal RGG domain in a manner that correlates with phase separation. In contrast, the internal IDR is neither necessary nor sufficient for phase separation. These findings support a new model for PGL-3 phase separation driven by oligomerization of structured domains and enhanced by RGG repeats independent of RNA.

DOI: https://doi.org/10.1101/2025.06.23.660947
bioRxiv. 2025 May 06. pii: 2025.05.02.651944. [Epub ahead of print]

Chinmo is a novel regulator of differential Hippo signaling response within a single developing organ.

Shreeharsha Tarikere, Tarun Kumar, Guillem Ylla, Cassandra G Extavour.

Orchestrated control of proliferation of multiple cell types is essential for building a healthy organ. Here we use larval ovary development in Drosophila melanogaster as a model to understand the homeostasis of somatic and germ line cells in the formation of the female adult reproductive organ. We previously showed that the highly conserved Hippo signaling pathway regulates proliferation of both germ line and somatic cells in the D. melanogaster larval ovary. Response to Hippo signaling appeared to be mediated by different genetic mechanisms in germ line and soma, but the mechanism allowing distinct responses to the same signaling pathway remained unknown. Here we perform cell type-specific RNA-Seq of isolated germ line and somatic cells from the developing ovary at multiple time points spanning the formation of germ line stem cell niches, in either a Hippo signaling loss- or gain-of-function genetic background. Applying network analysis to these data revealed a novel regulator of ovarian development, the transcription factor chinmo . Subsequent experimental validation showed that chinmo acts as a key germ cell-specific translator of Hippo signaling in the developing ovary, allowing the Hippo signal to be transduced in cell type-specific ways in germ line and somatic cells within the same organ.

DOI: https://doi.org/10.1101/2025.05.02.651944
bioRxiv. 2025 Jun 27. pii: 2025.06.20.660779. [Epub ahead of print]

A pre-menopausal single-cell atlas for ovarian drug discovery.

Hannah VanBenschoten, Zhanel Nugmanova, Audrey Olmsted, Laasya Devi Annepureddy, Ian Gingerich, Caroline Kratka, Ruixu Huang, Francesca E Duncan, Olha Kholod, Brittany A Goods.

Single-cell atlas efforts have reshaped the way we understand cells across the human body. Despite their power, they have not been effectively used to study ovarian biology in the context of other tissues, nor have they comprehensively incorporated healthy tissues from pre-menopausal donors. A focused pre-menopausal single-cell atlas could both advance our understanding of this life stage and support identification of ovarian gene targets for indications prevalent among younger demographics, such as fertility management. Here, we present an integrated resource of single-cell datasets from pre-menopausal women (PreMeno Atlas), comprising 511,365 cells from 14 tissues, including the ovary. This unified resource enables transcriptomic comparisons across cell types, tissues, and organs within the pre-menopausal context. Our analysis revealed distinct ovarian cell gene signatures, with theca and stromal cells exhibiting the most unique transcriptional profiles among ovarian cell types. We further leveraged the PreMeno Atlas to prioritize ovary-specific genes with potential druggability, particularly G-protein coupled receptors (GPCRs), identifying GPR78, ADRB3, GPR20, and GPR101 as candidate targets. Finally, we assessed species homology of ovarian cell marker genes using a harmonized mouse ovulation and spatial transcriptomics dataset. Collectively, this work establishes the PreMeno Atlas as a resource for ovarian biology research and contraceptive target discovery.

DOI: https://doi.org/10.1101/2025.06.20.660779
bioRxiv. 2025 Jun 16. pii: 2025.06.13.658151. [Epub ahead of print]

Non-autonomy of age-related morphological changes in the C. elegans germline stem cell niche.

Nilay Gupta, Mia Sinks, E Jane Albert Hubbard.

A decline in tissue renewal and repair due to changes in tissue stem cells is a hallmark of aging. Many stem cell pools are maintained by interaction with morphologically complex local niches. Using the C. elegans hermaphrodite germline stem cell system, we analyzed age-related changes in the morphology of the niche, the distal tip cell (DTC), and identified a molecular mechanism that promotes a subset of these changes. We found that a long-lived daf-2 mutant exhibits a daf-16 -dependent decline in number and length of long DTC processes. Surprisingly, the tissue requirement for daf-16(+) is non-autonomous and is independent of the longevity requirement: daf-16(+) in body wall muscle is both necessary and sufficient. We also determined that pre-formed DTC processes deteriorate prematurely when the underlying germline differentiates. We propose a reciprocal DTC-germline interaction model and speculate a mechanism by which reducing daf-2 activity prevents stem cell exhaustion. These studies establish the C. elegans DTC as a powerful in vivo model for understanding age-related changes in cellular morphology and their consequences in stem cell systems.
SUMMARY: The C. elegans germline stem cell niche morphology is markedly altered with age and is regulated non-autonomously from the muscle by insulin/IGF-like signaling. Results suggest reciprocal niche-germline regulation.

DOI: https://doi.org/10.1101/2025.06.13.658151
bioRxiv. 2025 Jun 15. pii: 2025.06.10.658920. [Epub ahead of print]

Systematic characterization of the ovarian landscape across mouse menopause models.

Minhoo Kim, Rajyk Bhala, Justin Wang, Ryan J Lu, Evelyn H Lee, Julio L Alvarenga, Rapheal G Williams, Bérénice A Benayoun.

Menopause not only affects fertility but also has widespread impact on systemic health. Yet, the molecular mechanisms underlying this process are not fully understood, partly due to the absence of robust, age-relevant preclinical models with comprehensive molecular and phenotypic characterization. To address this, we systematically compared three candidate mouse models of menopause: (1) intact aging, (2) chemical ovarian follicle depletion using 4-vinylcyclohexene diepoxide (VCD) administered at multiple ages, and (3) Foxl2 haploinsufficiency, a genetic model based on a transcription factor linked to human premature ovarian failure. Through histology, serum hormone profiling, single-cell transcriptomics and machine-learning approaches, we uncovered both shared and model-specific features of follicle loss, endocrine disruption, and transcriptional remodeling. The VCD and Foxl2 haploinsufficiency models revealed distinct patterns of hormonal and immune alterations not captured by intact aging alone. This comparative framework enables informed selection of context-appropriate preclinical rodent models to study menopause and the broader physiological consequences of ovarian aging.

DOI: https://doi.org/10.1101/2025.06.10.658920
Curr Opin Genet Dev. 2025 Jul 16. pii: S0959-437X(25)00073-5. [Epub ahead of print]94 102381

Why and how paternal mitochondrial DNA gets cut out of the inheritance.

Mayu Shimomura, Thomas R Hurd.

Mitochondrial DNA (mtDNA) is inherited maternally across animals, yet the evolutionary rationale behind this unusual mode of inheritance remains a longstanding mystery. Understanding the processes that prevent the transmission of paternal mtDNA and thus ensure maternal-only inheritance is crucial to uncovering the evolutionary significance of this widespread phenomenon. Historically, research has focused on mechanisms that act within eggs to destroy sperm mitochondria via autophagy and the ubiquitin-proteasome degradation system. However, recent discoveries across multiple animal species, including humans, reveal a surprising twist: paternal mtDNA is actively degraded within mitochondria independently of and prior to the complete breakdown of the organelle itself, often even prior to fertilization. Only a few studies have begun to illuminate the molecular machinery responsible for this early mtDNA elimination. In this review, we explore the emerging landscape of paternal mtDNA elimination mechanisms across species, highlighting newly discovered pathways, evolutionary implications, and open questions that are furthering our understanding of mitochondrial inheritance.

DOI: https://doi.org/10.1016/j.gde.2025.102381
Annu Rev Genet. 2025 Jul 16.

The Somatic Impact on Inheritance and the Germline Control of the Soma.

Shoma Ishikawa, Björn Schumacher.

The faithful transmission of genomic DNA over succeeding generations is an essential prerequisite for species maintenance. The germplasm theory by August Weismann has been foundational for the current understanding of heredity; it proposed that genetic inheritance is exclusively mediated by germ cells while they are protecting heritable germline genomes from the phylogenetic influences of an individual's life history. However, recent studies on the inheritance of epigenetic variation have challenged the traditional dogma of heredity and opened new perspectives on molecular mechanisms of inheritance. This review highlights the current knowledge about heritable memories of the ancestral lifestyle and discusses emerging frontiers in soma-germline circuits with a focus on the control of the integrity of heritable genomes as well as their implications for somatic and reproductive aging.

DOI: https://doi.org/10.1146/annurev-genet-020325-040022