bims-micesi Biomed News
on Mitotic cell signalling
Issue of 2025–08–17
fourteen papers selected by
Valentina Piano, Uniklinik Köln
  1. Regulation of X. laevis M18BP1 centromeric localization and CENP-A assembly.
  2. Decoding the language of PLK1 docking motifs and activation mechanisms.
  3. Aurora B maintains spherical shape of mitotic cells via simultaneously stabilizing myosin II and vimentin.
  4. Polo-like kinase 1 maintains transcription and chromosomal accessibility during mitosis.
  5. Psrc1 Ensures Proper Spindle Assembly and Chromosome Segregation During Mouse Oocyte Maturation.
  6. Redistribution of fragmented mitochondria ensures symmetric organelle partitioning and faithful chromosome segregation in mitotic mouse zygotes.
  7. G2 regulatory processes require speedbump for Wee1 kinase activity.
  8. RIF1 orchestrates a multi-step restoration of post-replicative H3K9me3.
  9. Optimizing chromosome yield: a comparative analysis of harvesting, preparation and waste recovery methods.
  10. A SETD2-CDK1-lamin axis maintains nuclear morphology and genome stability.
  11. KDM5B impairs oocyte quality and causes embryo arrest via epigenetic regulation of spindle assembly and chromosome arrangement.
  12. Accurate Identification of Cell Cycle Stages in RPE1 Cells Using the ImmunoCellCycle-ID Method.
  13. Mitosis Localization Signal (MLS) extends KA1 and regulates MELK kinase localization to plasma membrane and activity in Xenopus embryo.
  14. Biallelic variants in DLGAP5 cause spindle assembly defects and human early embryonic arrest.
  1. bioRxiv. 2025 Jul 15. pii: 2025.07.15.664882. [Epub ahead of print]
    Regulation of X. laevis M18BP1 centromeric localization and CENP-A assembly.
    Rae R Brown, Jacob P Schwartz, Lyin Ghadri, Aaron F Straight.
      Eukaryotic chromosome segregation requires attachment of chromosomes to microtubules of the mitotic spindle through the kinetochore so that chromosomes can align and move in mitosis. Kinetochores are assembled on the centromere which is a unique chromatin domain that is epigenetically defined by the histone H3 variant CENtromere Protein A (CENP-A). During DNA replication CENP-A is equally divided between replicated chromatids and new CENP-A nucleosomes are re-assembled during the subsequent G1 phase of the cell cycle. How cells regulate the strict cell cycle timing of CENP-A assembly is a central question in the epigenetic maintenance of centromeres and kinetochores. One essential assembly factor for CENP-A nucleosomes is the Mis18 complex (Mis18α, Mis18β, and M18BP1) which is regulated in its localization to centromeres between metaphase and G1 when CENP-A assembly occurs. Here, we define a new regulatory mechanism that works through cell cycle dependent phosphorylation of Xenopus laevis M18BP1 between metaphase and interphase. This phosphoregulatory switch disrupts binding of M18BP1 to CENP-A nucleosomes in metaphase, and when relieved enables M18BP1 binding to CENP-A nucleosomes in interphase. We show that this phosphorylation dependent switching mechanism regulates CENP-A nucleosome assembly. We propose that the phospho-regulated binding of M18BP1 to CENP-A nucleosomes is an important control mechanism that restricts the timing of new CENP-A assembly.
    DOI:  https://doi.org/10.1101/2025.07.15.664882
  2. Trends Cell Biol. 2025 Aug 08. pii: S0962-8924(25)00156-4. [Epub ahead of print]
    Decoding the language of PLK1 docking motifs and activation mechanisms.
    Arianna Esposito-Verza, Andrea Musacchio, Duccio Conti.
      Polo-like kinase 1 (PLK1) phosphorylates a plethora of different substrates to regulate key cell cycle processes that include, among others, mitotic entry, chromosome condensation, nuclear envelope breakdown, centrosome maturation, spindle assembly and chromosome biorientation, cytokinesis, and the deposition of the specialized centromere histone CENP-A. Addressing the exact spatial and temporal control of PLK1 activity in these processes and its dynamic interplay with protein phosphatases that counteract mitotic phosphorylation, most notably PP1 and PP2A, has proven especially puzzling. In this review, we focus on the main unknowns in the area of human PLK1 regulation, exploring more specifically an emerging concept that master docking sites, including newly discovered noncanonical motifs, trigger initial local activation of PLK1 that promotes subsequent localized spreading of phosphorylation.
    Keywords:  Aurora A; Bora; Polo-like kinase 1; activation loop; centrosome; chromosome segregation; kinetochore
    DOI:  https://doi.org/10.1016/j.tcb.2025.07.004
  3. J Mol Cell Biol. 2025 Aug 08. pii: mjaf023. [Epub ahead of print]
    Aurora B maintains spherical shape of mitotic cells via simultaneously stabilizing myosin II and vimentin.
    Chenxi Hou, Fazhi Yu, Cheng Cao, Tianchen Wang, Zihang Pan, Minru Zhong, Xing Liu, Xuebiao Yao, Kaiguang Zhang, Zhenye Yang, Jing Guo.
      Cells round up when they enter mitosis and maintain this rounded morphology until they pass the spindle assembly checkpoint during anaphase. However, the mechanisms that regulate and maintain this transient spherical state remain unclear. In this study, we demonstrate that both astral microtubules and Aurora B kinase are required to maintain cortex stability during prometaphase. Simultaneous inhibition of astral microtubules and Aurora B leads to severe and continuous deformation of mitotic cells, resulting in micronuclei containing chromosomes after the cells exit mitosis. Mechanistically, active Aurora B kinase reduces the activity of myosin light chain kinase through phosphorylation, which in turn decreases the motor activity of myosin II. Additionally, Aurora B kinase regulates the distribution of actin at the cortex by phosphorylating the intermediate filament protein vimentin. Blocking these phosphorylation events disrupts the para-cortex localization of vimentin around the cortex and leads to the dislocalization of actin at the cortex. These regulatory effects occur in highly mobile cells expressing vimentin. In summary, we show that during mitosis, Aurora B kinase coordinates the interactions between microtubules, actin, and intermediate filaments to stabilize the cortex of rounded mitotic cells, ensuring the successful completion of mitosis.
    Keywords:  Aurora B; cortex; mitosis; rounding; vimentin
    DOI:  https://doi.org/10.1093/jmcb/mjaf023
  4. Mol Biol Cell. 2025 Aug 13. mbcE25020053
    Polo-like kinase 1 maintains transcription and chromosomal accessibility during mitosis.
    Zhouyuan Shen, Kristin Adams, Ryan Moreno, Robert Lera, Emily Kaufman, Jessica D Lang, Mark Burkard.
      Transcription persists at low levels in mitotic cells and plays essential roles in mitotic fidelity and chromosomal dynamics. However, the detailed regulatory network of mitotic transcription remains largely unresolved. Here, we report the novel role of Polo-like kinase 1 (Plk1) in maintaining mitotic transcription. Using 5-ethynyl uridine (5-EU) labeling of nascent RNAs, we found that Plk1 inhibition leads to significant downregulation of nascent transcription in prometaphase cells. Chromatin-localized Plk1 activity is required for transcription regulation and mitotic fidelity. Plk1 sustains global chromosomal accessibility in mitosis, especially at promoter and transcription start site (promoter-TSS) regions, facilitating transcription factor binding and ensuring proper transcriptional activity. We identified SMC4, a common subunit of condensin I and II, as a potential Plk1 substrate. Plk1 activity is fundamental to these processes across non-transformed and transformed cell lines, underscoring its critical role in cell cycle regulation. This study elucidates a novel regulatory mechanism of global mitotic transcription, advancing our understanding of cell cycle control.
    DOI:  https://doi.org/10.1091/mbc.E25-02-0053
  5. FASEB J. 2025 Aug 31. 39(16): e70928
    Psrc1 Ensures Proper Spindle Assembly and Chromosome Segregation During Mouse Oocyte Maturation.
    Wang Xin-Jie, Wei Kang-Na, Liu Yu-Qing, Zeng Zhao-Cheng, Liang Hui-Sheng, Jiang Jiang, Zeng Li-Xin, Wang Hai-Long.
      The proper assembly and migration of the spindle and the correct segregation of the chromosomes play a crucial role in oocyte quality. In somatic cells, Psrc1 regulates spindle dynamics and mitotic progression; however, its functions in oocyte meiosis have not been fully elucidated. This study aims to elucidate the functions of Psrc1 in mouse oocyte meiosis. To understand PSRC1's function, immunofluorescence staining was used to examine its location in the oocyte and to analyze phenotype after protein knockdown. Western blotting was used to examine the PSRC1 protein abundance. The treatment of oocytes with Taxol and nocodazole demonstrated that PSRC1 co-localizes with spindle microtubules. Psrc1 was knocked down by siRNA injection, and myc-Psrc1 mRNA was overexpressed via plasmid construction. In the current study, we demonstrated for the first time that PSRC1 is located at the poles of the spindle at all stages of mouse oocyte development. Knockdown of Psrc1 leads to abnormal spindle morphology, continuous activation of the spindle assembly checkpoint (SAC) protein, abnormal kinetochore-microtubule (K-M) attachments, and an increased aneuploidy rate. Surprisingly, either knockdown or overexpression of Psrc1 also causes abnormal spindle assembly and increases the rate of large polar bodies. To summarize, Psrc1 is essential for spindle assembly and chromosome segregation during mouse oocyte maturation.
    Keywords:   Psrc1 ; meiosis; mice; oocyte; spindle
    DOI:  https://doi.org/10.1096/fj.202501813R
  6. Elife. 2025 Aug 11. pii: RP99936. [Epub ahead of print]13
    Redistribution of fragmented mitochondria ensures symmetric organelle partitioning and faithful chromosome segregation in mitotic mouse zygotes.
    Haruna Gekko, Ruri Nomura, Daiki Kuzuhara, Masato Kaneyasu, Genpei Koseki, Deepak Adhikari, Yasuyuki Mio, John Carroll, Tomohiro Kono, Hiroaki Funahashi, Takuya Wakai.
      In cleavage-stage embryos, preexisting organelles partition evenly into daughter blastomeres without significant cell growth after symmetric cell division. The presence of mitochondrial DNA within mitochondria and its restricted replication during preimplantation development makes their inheritance particularly important. While chromosomes are precisely segregated by the mitotic spindle, the mechanisms controlling mitochondrial partitioning remain poorly understood. In this study, we investigate the mechanism by which Dynamin-related protein 1 (Drp1) controls the mitochondrial redistribution and partitioning during embryonic cleavage. Depletion of Drp1 in mouse zygotes causes marked mitochondrial aggregation, and the majority of embryos arrest at the 2 cell stage. Clumped mitochondria are located in the center of mitotic Drp1-depleted zygotes with less uniform distribution, thereby preventing their symmetric partitioning. Asymmetric mitochondrial inheritance is accompanied by functionally inequivalent blastomeres with biased ATP and endoplasmic reticulum Ca2+ levels. We also find that marked mitochondrial centration in Drp1-depleted zygotes prevents the assembly of parental chromosomes, resulting in chromosome segregation defects and binucleation. Thus, mitochondrial fragmentation mediated by Drp1 ensures proper organelle positioning and partitioning into functional daughters during the first embryonic cleavage.
    Keywords:  Dynamin-related protein 1; binuclear formation; chromosome segregation; developmental biology; mitochondrial dynamics; mouse; organelle inheritance; preimplantation development
    DOI:  https://doi.org/10.7554/eLife.99936
  7. Dev Biol. 2025 Aug 09. pii: S0012-1606(25)00223-4. [Epub ahead of print]
    G2 regulatory processes require speedbump for Wee1 kinase activity.
    Rachel M Warga, Donald A Kane.
      Wee1 is a conserved Cdk1 inhibitory kinase operating at the G2/M checkpoint to prevent entry into mitosis until the genome has been surveilled and replication is complete. We report here that the early arrest mutant speedbump is a loss-of-function mutation in the zebrafish ortholog of wee1. Like other creatures lacking Wee1 kinase, cells in the mutant enter mitosis early. Eventually, mutant cells exhibit chromosomal defects and undergo apoptosis. Live recordings of the mutant reveal that as gastrula cells transition from maternal to zygotic control, their cell cycle gets progressively shorter rather than lengthening as seen in wild-type embryos. This suggests that Wee1 kinase inhibition is part of a mechanism to slow the cell cycle that we posit is independent of its role in blocking entry into mitosis to prevent DNA damage. Supporting this view, we show that Wee1 kinase is also crucial for tissues that normally exit the cell cycle in the G2 phase. In the absence of Wee1 kinase, hatching gland cells, which typically cease dividing before speedbump defects appear, no longer remain in G2, and instead advance into mitosis before prematurely dying. Finally, we demonstrate that Wee1 kinase is essential for the endoreplication cycle in the yolk cell. We show that wild-type yolk cell nuclei transition to an S and G endocycle after they cease mitosis in the blastula. However, without Wee1 kinase these nuclei have difficulty attaining this endocycle and sometimes regress back into mitosis. We conclude that besides the regulation of mitotic timing, Wee1 kinase has other G2 regulatory roles not previously reported in which controlling entry into mitosis must be coordinated with other cellular processes.
    Keywords:  G2; Wee1 kinase; cell cycle; deep cell; endocycle; hatching gland; mitosis; yolk cell; zebrafish
    DOI:  https://doi.org/10.1016/j.ydbio.2025.08.006
  8. bioRxiv. 2025 Jul 15. pii: 2025.07.14.664777. [Epub ahead of print]
    RIF1 orchestrates a multi-step restoration of post-replicative H3K9me3.
    Naiming Chen, Susanne Bandau, Reshma Ravindran Nair Pushkala Kumari, Bram Prevo, Takayo Sasaki, Shaun Web, Simone di Sanzo, David Shapira, Moritz Voelker-Albert, David M Gilbert, Constance Alabert, Sara B C Buonomo.
      DNA replication causes the dilution of parental histones along with their specific post-translational modifications. The kinetics of restoring these marks on newly incorporated histones dictate how quickly genomic domains regain their epigenetic identity after replication. H3K9me3 is restored extremely slowly; the process of reconstitution, to achieve the pre-replication levels, continues throughout the following G1 phase. The molecular mechanisms behind this slow reconstitution are unknown. We show here that RIF1's reassociation with heterochromatin during mitotic exit is required to set up a chromatin environment permissive for histone methyltransferases to resume H3K9me3 deposition. RIF1 facilitates the recruitment of SUV39H1, HP1α and HP1β and is required for the increased tri-methylation of H3K9 that occurs during G1 phase. RIF1 is also indispensable for recruiting Protein Phosphatase 1α (PP1α) to heterochromatin, and the interaction between RIF1 and PP1α is essential for the maintenance of H3K9me3 levels. In addition, RIF1-PP1 complex temporally restrains the activity of Aurora kinase at heterochromatin, ensuring that phosphorylation of H3S10 does not precede replication. This creates a time- window permissive for SUV39Hs to initiate the reinstatement of H3K9me3.
    DOI:  https://doi.org/10.1101/2025.07.14.664777
  9. Biotechniques. 2025 Aug 11. 1-12
    Optimizing chromosome yield: a comparative analysis of harvesting, preparation and waste recovery methods.
    Sarah L Berger, Rinyaporn Phengchat, Stanley W Botchway, Mohammed Yusuf.
      In mitotic chromosome preparation, it is crucial to maximize chromosome yield for downstream cytogenetic analysis. Using HeLa cells as a model adherent cell, we assessed and compared the recovery of chromosomes from the entire process as well as the fraction of chromosomes that would generally become discarded in the standardly used trypsinization and mitotic-shake-off chromosome preparation methods. A higher chromosome yield for polyamine (PA) and methanol acetic acid (MAA) chromosomes was achieved using the mitotic-shake-off method compared to trypsinization. Moreover, mitotic arrest using colcemid or nocodazole gave similar PA and MAA chromosome yields in the commonly collected fractions. Interestingly, when comparing the fractions that would usually be discarded in the mitotic-shake-off, for colcemid-treated cells compared to nocodazole-treated cells, a greater number of PA chromosomes was recovered from the former. Our results show that chromosomes can be retrieved from the waste media. These recovered chromosomes display a suitable morphology in all chromosome preparations, suggesting that in conditions where high chromosome yields are required, utilizing the mitotic-shake-off method and recovering the generally discarded chromosome fraction together with the commonly used fraction would aid in maximizing chromosome yield.
    Keywords:  chromosomes; methanol acetic acid; mitotic; mitotic inhibitors; polyamine
    DOI:  https://doi.org/10.1080/07366205.2025.2536438
  10. Nat Cell Biol. 2025 Aug;27(8): 1327-1341
    A SETD2-CDK1-lamin axis maintains nuclear morphology and genome stability.
    Abid Khan, Cheng Zhang, Phu G Nguyen, James M Metts, Lucas C Collins, Kanishk Jain, C Allie Mills, Logan Vlach, Kelin Li, Amanda L Brademeyer, Brittany M Bowman, Michael B Major, Jeffrey Aubé, Laura E Herring, W Kimryn Rathmell, Frank M Mason, Ian J Davis, Qing Zhang, Brian D Strahl.
      Histone methyltransferases regulate chromatin organization and are frequently mutated in human diseases, including cancer. One such often mutated methyltransferase, SETD2, associates with transcribing RNA polymerase II and catalyses H3K36me3-a modification that contributes to gene transcription, splicing and DNA repair. Although its catalytic function is well-characterized, its non-catalytic roles remain unclear. Here we reveal a catalysis-independent function of SETD2 in nuclear lamina stability and genome integrity. Through its intrinsically disordered amino terminus, SETD2 associates with lamina-associated proteins, including lamin A/C, lamin B1 and emerin. Loss of SETD2 or its N terminus leads to severe nuclear morphology defects and genome instability, mirroring lamina dysfunction. Mechanistically, the N terminus of SETD2 serves as a scaffold for the mitotic kinase CDK1 and lamins, facilitating lamin phosphorylation and depolymerization during mitosis. Restoration of the N-terminal regions required for interaction with CDK1 and lamins rescues nuclear morphology and suppresses tumorigenic growth in a clear cell renal cell carcinoma model with SETD2 haploinsufficiency. These findings reveal a previously unrecognized role of SETD2 in nuclear lamina organization and genome maintenance that probably extends to its role as a tumour suppressor.
    DOI:  https://doi.org/10.1038/s41556-025-01723-9
  11. Theriogenology. 2025 Aug 09. pii: S0093-691X(25)00357-7. [Epub ahead of print]249 117631
    KDM5B impairs oocyte quality and causes embryo arrest via epigenetic regulation of spindle assembly and chromosome arrangement.
    Yingnan Yang, Xiaowei Chen, Mingtian Deng, Feng Wang.
      Oocyte-stored maternal factors are critical for successful embryonic development, but they are remained incompletely understood. Histone demethylase KDM5B has been implicated in the regulation of embryonic development and genomic stability. However, the specific role of KDM5B during oocyte maturation and early embryogenesis remains unclear in goat. In this study, we investigated the function of KDM5B during goat oocyte maturation and early embryogenesis. Using GSK467, a selective KDM5B inhibitor, we observed increased H3K4me3 accumulation in both oocytes and parthenogenetically activated (PA) embryos. Secondly, inhibition of KDM5B disrupted spindle assembly and chromosome alignment, induced DNA damage, and significantly reduced the oocyte maturation rate in both goat and mouse models. Moreover, inhibition of KDM5B leads to developmental arrest of PA embryos, and low-input RNA sequencing of 8-cell-stage PA embryos revealed defective maternal mRNA degradation and impaired zygotic genome activation. In summary, our findings demonstrate that KDM5B plays a critical role in regulating spindle assembly and chromosome alignment maintaining oocyte quality, and supporting early embryo development. This study provides new insights into the epigenetic regulation of reproductive competence in mammals.
    Keywords:  Chromosome arrangement; KDM5B; Oocyte maturation; Spindle assembly; Zygotic gene
    DOI:  https://doi.org/10.1016/j.theriogenology.2025.117631
  12. Bio Protoc. 2025 Aug 05. 15(15): e5407
    Accurate Identification of Cell Cycle Stages in RPE1 Cells Using the ImmunoCellCycle-ID Method.
    Syon Reddy, Yu-Lin Chen, Aussie Suzuki.
      Accurate identification of cell cycle stages is essential for investigating fundamental biological processes such as proliferation, differentiation, and tumorigenesis. While flow cytometry remains a widely used technique for such analyses, it is limited by its lack of single-cell resolution and its requirement for large sample sizes due to its population-based approach. These limitations underscore the need for alternative or complementary methods that offer single-cell precision with compatibility for small-scale applications. We present ImmunoCellCycle-ID, an immunofluorescence-based method that leverages the spatial distribution of endogenous markers, such as DNA, proliferating cell nuclear antigen (PCNA), centromere protein F (CENP-F), and centromere protein C (CENP-C), to reliably distinguish G1, early S, late S, early G2, late G2, and all mitotic sub-stages. This technique does not rely on precise signal quantification and utilizes standard immunofluorescence protocols alongside conventional laboratory microscopes, ensuring broad accessibility. Importantly, ImmunoCellCycle-ID detects endogenous proteins without the need for genetic modification, making it readily applicable to a wide range of human cell lines. Beyond its utility for single-cell resolution, the method can be scaled for population-level analyses, similar to flow cytometry. With its precision, versatility, and ease of implementation, ImmunoCellCycle-ID offers a powerful tool for high-resolution cell cycle profiling across diverse experimental platforms. Key features • Enables high-precision identification of cell cycle stages at single-cell resolution. • Broadly applicable to diverse human cell lines without genetic modification. • Fully compatible with standard fluorescence microscopy; no specialized equipment needed. • Requires only minimal image analysis and no complex quantification.
    Keywords:  Cancer research; Cell biology; Cell cycle; Immunofluorescence; Single-cell analysis
    DOI:  https://doi.org/10.21769/BioProtoc.5407
  13. Dev Biol. 2025 Aug 13. pii: S0012-1606(25)00228-3. [Epub ahead of print]
    Mitosis Localization Signal (MLS) extends KA1 and regulates MELK kinase localization to plasma membrane and activity in Xenopus embryo.
    Caroline Badouel, Guillaume Hatte, Claude Prigent, Jacek Z Kubiak, Jean-Pierre Tassan.
      MELK is a cell-cycle dependent serine/threonine protein kinase whose expression is elevated in proliferating and cancer cells. In the Xenopus embryo, MELK overexpression induces cytokinesis failure, leading to multinucleated cells. This phenotype requires MELK catalytic activity, which correlates with MELK conformational modification and its localization to the cell membrane. How MELK activation and localization are coordinated remains unclear. Here, we show that in Xenopus gastrula epithelial cells MELK is abruptly enriched at the plasma membrane starting precisely from the metaphase-to-anaphase transition until early interphase. We show that deletion of the Kinase-Associated domain 1 (KA1), involved in binding to anionic phospholipids, does not abolish MELK localization to the plasma membrane. By a series of deletions, we identified a new 41-amino-acid domain, called Mitosis Localization Signal (MLS) that regulates MELK localization to the plasma membrane in dividing cells. We show that MLS cooperates with KA1 to regulate MELK localization and is necessary to induce cytokinesis failure when MELK is overexpressed. Our findings highlight the importance of MLS in MELK localization and in regulating MELK activity.
    Keywords:  cytokinesis; mitosis; plasma membrane
    DOI:  https://doi.org/10.1016/j.ydbio.2025.08.011
  14. Hum Reprod. 2025 Aug 12. pii: deaf158. [Epub ahead of print]
    Biallelic variants in DLGAP5 cause spindle assembly defects and human early embryonic arrest.
    Huiling Hu, Xian Wan, Jiaqi Sun, Shen Zhang, Jing Guo, Yinli Zhang, Fei Meng, Shuoping Zhang, Yifan Gu, Fei Gong, Hongqing Liao, Ge Lin, Wei Zheng.
       STUDY QUESTION: What effects do DLGAP5 defects have on human early embryo development?
    SUMMARY ANSWER: DLGAP5 deficiency disrupts normal spindle assembly through its interaction with TACC3, leading to female infertility characterized by recurrent early embryonic arrest (REEA).
    WHAT IS KNOWN ALREADY: REEA is a significant contributor to failures in assisted reproductive technology. While genetic factors play a crucial role, known gene variants account for only a small proportion of affected individuals, leaving many underlying genetic factors yet to be elucidated. The relationship between spindle assembly and early embryonic development has emerged as a key research focus, however, our understanding of bipolar spindles in human oocytes and early embryos remains limited, highlighting the need for further investigation into the essential molecular players involved.
    STUDY DESIGN, SIZE, DURATION: A total of 488 female patients experiencing infertility characterized as REEA were recruited from a university-affiliated center from November 2021 to December 2023.
    PARTICIPANTS/MATERIALS, SETTING, METHODS: Whole-exome sequencing was performed on the REEA cohort to identify candidate variants. HeLa cells were transiently transfected with wild-type and mutant plasmids to evaluate protein abundance and localization. Mutant mRNAs were expressed at the zygote stage to monitor subsequent embryonic development. Immunoprecipitation-mass spectrometry was employed to identify altered interacting molecules associated with the candidate variants. Additionally, a site-directed mutant mouse model was developed to investigate the pathogenic mechanisms in vivo, validated with patient oocytes and arrested embryos.
    MAIN RESULTS AND THE ROLE OF CHANCE: The study identified two nonsense variants, one frameshift variant, and one missense pathogenic variant in the DLGAP5 gene of three independent families from the cohort of 488 REEA patients through whole-exome sequencing. All affected individuals displayed a Mendelian recessive inheritance pattern. These variants significantly altered protein length, abundance, or localization, resulting in spindle abnormalities in HeLa cells and mouse zygotes. Furthermore, the microinjection of exogenous mutant DLGAP5 mRNA into mouse zygote and the construction of Dlgap5 site-directed mutant mice successfully replicated the patient phenotypes. Functional studies, both in vivo and in vitro, revealed that DLGAP5 deficiency disrupts normal spindle assembly through its interaction with TACC3.
    LIMITATIONS, REASONS FOR CAUTION: This study was unable to observe the dynamic changes in spindle assembly in oocytes from patients with DLGAP5 variants due to ethical restrictions. Additionally, a larger patient cohort is needed, particularly multi-center and multi-ethnic studies, to further establish the relationship between DLGAP5 variants and female infertility.
    WIDER IMPLICATIONS OF THE FINDINGS: These findings suggest that DLGAP5 is essential for spindle assembly in oocytes through its interaction with TACC3. This could position DLGAP5 as a novel molecular diagnostic marker and a potential target for interventions in female infertility related to REEA.
    STUDY FUNDING/COMPETING INTEREST(S): This work was supported by the National Natural Science Foundation of China (82371672 and 82371667), the National Key Research and Development Program of China (2023YFC2705504 and 2022YFC2702300), the Natural Science Foundation of Hunan Province (2024JJ2083), the Science and Technology Innovation Program of Hunan Province (2023RC3233) and the Scientific Research Foundation of Reproductive and Genetic Hospital of CITIC-XIANGYA (YNXM-202202 and YNXM-202402), and Hunan Provincial Grant for Innovative Province Construction (2019SK4012). The authors declare they have no conflict of interest.
    TRIAL REGISTRATION NUMBER: N/A.
    Keywords:   DLGAP5 variant; TACC3 interaction; assisted reproductive technology; early embryonic arrest; female infertility; spindle
    DOI:  https://doi.org/10.1093/humrep/deaf158
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