bims-micesi Biomed News
on Mitotic cell signalling
Issue of 2025–09–07
twenty papers selected by
Valentina Piano, Uniklinik Köln
  1. When the Clock Is Ticking: The Role of Mitotic Duration in Cell Fate Determination.
  2. NuSAP1 promotes bipolar spindle assembly in Trypanosoma brucei by bundling spindle microtubules.
  3. Plasmodium ARK1 regulates spindle formation during atypical mitosis and forms a divergent chromosomal passenger complex.
  4. Mechanisms of nuclear segregation in a multinucleate multibudding yeast.
  5. Optineurin Localization at the Centrosome, Spindle, and Midbody Implies Its Role in Cell Division.
  6. Ndc80 complex, a conserved coupler for kinetochore-microtubule motility, is a sliding molecular clutch.
  7. Investigating Nuclear Envelope Assembly on Mis-Segregated Chromosomes.
  8. The unique contributions of Rab11 and Rab35 to the completion of cell division.
  9. The centromere: the punching bag of the chromosome.
  10. Farnesylation-Dependent Kinetochore Targeting of CENP-F Is Essential for Oocyte Meiotic Progression and Female Fertility.
  11. Stu2 performs an essential kinetochore function independent of its microtubule polymerase activity.
  12. Transcription-Replication Conflicts and Incomplete Replication as a Cause of Micronuclei-Driven Chromoanagenesis.
  13. Effects of reversine and proTAME treatment on chromosome segregation during mouse oocyte maturation.
  14. Lysine demethylase 4A is a centrosome-associated protein required for centrosome integrity and genomic stability.
  15. Classifying the AMi-Br Mitotic Figure Dataset with AUCMEDI.
  16. The Fate of Micronuclei.
  17. Development of D-box peptides to inhibit the anaphase-promoting complex/cyclosome.
  18. DNA methylation influences human centromere positioning and function.
  19. Acentrosomal aster with atypical microtubule polarity recruits cytokinesis signals to its center in Xenopus egg extracts.
  20. The making of a leaf tip: how cell division angles define shape.
  1. Bioessays. 2025 Aug 30. e70061
    When the Clock Is Ticking: The Role of Mitotic Duration in Cell Fate Determination.
    Cornelia Sala, Elmar Schiebel.
      Mitosis is a crucial phase of the cell cycle, during which several mechanisms work together to ensure accurate chromosome segregation and to eliminate defective cells if errors occur. One key mechanism is the spindle assembly checkpoint (SAC), which upon mitotic errors-such as those induced by genetic mutations, drug treatments, or environmental stresses-arrest cells in mitosis. Arrested cells may undergo apoptosis during mitosis or eventually exit mitosis even if the damage remains unrepaired. Mitotic exit is driven by a reduction in cyclin B1 levels, regulated during mitosis by multiple mechanisms affecting both its synthesis and degradation. Strikingly, cells harboring the tumor suppressor p53 can monitor the duration of mitosis and encode this information as a form of "mitotic memory". This memory influences the fate of daughter cells after mitotic exit by inducing G1 arrest through p53-dependent expression of the cyclin-dependent kinase (CDK) inhibitor p21. Recent studies have proposed mechanisms by which cyclin B1 levels are regulated during mitotic arrest and how p53 promotes mitotic-arrest-dependent transcription of p21 in G1. These findings indicate that both the expression of regulators that control mitotic duration and the activity of proteins that monitor the duration of mitosis and halt proliferation work together to determine cell fate following mitotic errors. Understanding these mechanisms offers valuable insights for cancer therapy, particularly regarding the strategic application of antimitotic agents.
    DOI:  https://doi.org/10.1002/bies.70061
  2. bioRxiv. 2025 Aug 25. pii: 2025.08.25.672125. [Epub ahead of print]
    NuSAP1 promotes bipolar spindle assembly in Trypanosoma brucei by bundling spindle microtubules.
    Qing Zhou, Yasuhiro Kurasawa, Thiago Souza Onofre, Ziyin Li.
      The parasitic protozoan Trypanosoma brucei assembles a bipolar mitotic spindle and undergoes a closed mitosis to segregate its megabase chromosomes and mini-chromosomes through mechanisms that are distinct from its mammalian host. This parasite employs a subset of trypanosome-specific nucleus- and spindle-associated proteins (NuSAPs) to regulate mitosis, but the mechanistic roles of these proteins remain poorly understood. Here, we performed biochemical and molecular characterization of NuSAP1 and analyzed the functional interplay of NuSAP1 with its interacting and proximal proteins. NuSAP1 localizes to the mitotic spindle with spindle pole enrichment, and interacts with the spindle-associated and spindle pole-enriched proteins NuSAP4 and SPB1 through distinct structural motifs. NuSAP1 and NuSAP4 are interdependent for protein stability, and NuSAP1 is required for SPB1 localization. Further, NuSAP1 bundles microtubules in vitro , and depletion of NuSAP1 disrupts bipolar spindle assembly. Finally, knockdown of NuSAP1 disrupts the localization of its proximal proteins MAP103 and TbMlp2 to spindle poles. Together, these results uncover the mechanistic role of NuSAP1 in bipolar spindle assembly by bundling spindle microtubules and promoting spindle pole complex formation, underscoring unusual regulatory mechanisms for mitosis in this early divergent unicellular eukaryote.
    DOI:  https://doi.org/10.1101/2025.08.25.672125
  3. bioRxiv. 2025 Aug 27. pii: 2025.08.27.672654. [Epub ahead of print]
    Plasmodium ARK1 regulates spindle formation during atypical mitosis and forms a divergent chromosomal passenger complex.
    Annu Nagar, Ryuji Yanase, Mohammad Zeeshan, David J P Ferguson, Steven Abel, Sarah L Pashley, Akancha Mishra, Antonius Eze, Edward Rea, Declan Brady, Andrew R Bottrill, Sue Vaughan, Karine G Le Roch, David S Guttery, Anthony A Holder, Eelco C Tromer, Pushkar Sharma, Rita Tewari.
      Mitosis in Plasmodium spp., the causative agent of malaria, is fundamentally different from model eukaryotes, proceeding via a bipartite microtubule organising centre (MTOC) and lacking canonical regulators such as Polo and Bub1 kinases. During schizogony, asynchronous nuclear replication produces a multinucleate schizont, while rapid male gametogony generates an octaploid nucleus before gamete formation. Here, we identify Aurora-related kinase 1 (ARK1) as a key component of inner MTOC and spindle formation, controlling kinetochore dynamics and driving mitotic progression. Conditional ARK1 depletion disrupts spindle biogenesis, kinetochore segregation, karyokinesis and cytokinesis in both stages, and affects parasite transmission. Interactome analysis reveals ARK1 as the catalytic core of a non-canonical chromosomal passenger complex (CPC) containing two divergent inner centromere proteins (INCENPs) but lacking Survivin and Borealin. Comparative genomics indicates this CPC architecture arose early in Apicomplexa, replacing canonical centromere-targeting modules. These findings uncover a distinct mitotic machinery in Plasmodium and identify the ARK1-INCENP interface as a potential multistage target for malaria therapeutic intervention.
    DOI:  https://doi.org/10.1101/2025.08.27.672654
  4. J Cell Biol. 2025 Nov 03. pii: e202504068. [Epub ahead of print]224(11):
    Mechanisms of nuclear segregation in a multinucleate multibudding yeast.
    Claudia A Petrucco, Alex W Crocker, Alison C E Wirshing, Analeigha V Colarusso, Maya Waarts, Amy S Gladfelter, Daniel J Lew.
      Budding yeasts present an especially challenging geometry for segregation of chromosomes, which must be delivered across the narrow mother-bud neck into the bud. Studies in the model yeast Saccharomyces cerevisiae have revealed an elaborate set of mechanisms that selectively orient one mitotic spindle pole toward the bud and then drive spindle elongation along the mother-bud axis, ensuring nuclear segregation between mother and bud. It is unclear how these pathways might be adapted to yield similar precision in more complex cell geometries. Here, we provide the first description of the dynamics of mitosis in a multinucleate, multibudding yeast, Aureobasidium pullulans, and identify many unexpected differences from uninucleate yeasts. Mitotic spindles do not orient along the mother-bud axis prior to anaphase, and accurate nuclear segregation often occurs after spindle disassembly. Cortical Num1-dynein forces pull highly mobile nuclei into buds, and once a nucleus enters a bud, it discourages others from entering, ensuring that most daughters inherit only one nucleus.
    DOI:  https://doi.org/10.1083/jcb.202504068
  5. Cytoskeleton (Hoboken). 2025 Jul 31.
    Optineurin Localization at the Centrosome, Spindle, and Midbody Implies Its Role in Cell Division.
    Ankan Chakraborty, Marie-Noelle Benassy, Dominique Weil, Bishwajit Kundu.
      Optineurin (OPTN), a multifunctional cytosolic protein, is recognized as an autophagy adaptor. Its association with neurodegenerative diseases, like ALS, triggered extensive research. OPTN has been found in intracellular organelles, including the mitochondria, Golgi body, endosomes, microtubules, and the nucleus. The report of mitotic defects and delayed cell division in OPTN-depleted cells prompted us to explore OPTN's exact localization in the cell that could interfere with cell division assemblies. We used three distinct human cell lines, HeLa, HEK293, and SH-SY5Y, and probed them for OPTN localization using both centrosomal (Aurora A kinase, pericentrin, PCM1, Cep170, and γ-tubulin) and mitotic spindle markers (β-tubulin). Our immunofluorescence-based detection using wide-field fluorescence, confocal, and structured illumination microscopy (SIM) placed OPTN at the centrosome, which remained associated with the centriole after duplication and their migration during mitosis. OPTN was also observed at the junction of daughter cells during cytokinesis. Our finding reveals unmapped localizations of OPTN with key cytosolic assemblies that are directly involved in cell division.
    Keywords:  cell division; centrosome; midbody; mitotic spindle; optineurin; pericentriolar matrix; structured illumination microscopy
    DOI:  https://doi.org/10.1002/cm.70015
  6. Sci Adv. 2025 Sep 05. 11(36): eadx0005
    Ndc80 complex, a conserved coupler for kinetochore-microtubule motility, is a sliding molecular clutch.
    Vladimir M Demidov, Ivan V Gonchar, Suvranta K Tripathy, Fazly I Ataullakhanov, Ekaterina L Grishchuk.
      Chromosome motion at spindle microtubule plus ends relies on dynamic molecular bonds between kinetochores and proximal microtubule walls. Under opposing forces, kinetochores move bidirectionally along these walls while remaining near the ends, yet how continuous wall sliding occurs without end detachment remains unclear. Using ultrafast force-clamp spectroscopy, we show that single Ndc80 complexes, the primary microtubule-binding kinetochore component, exhibit processive, bidirectional sliding. Plus end-directed forces induce a mobile catch bond in Ndc80, increasing frictional resistance and restricting sliding toward the tip. Conversely, forces pulling Ndc80 away from the plus end trigger mobile slip-bond behavior, facilitating sliding. This dual behavior arises from force-dependent modulation of the Nuf2 calponin-homology domain's microtubule binding, identifying this subunit as a friction regulator. We propose that Ndc80's ability to modulate sliding friction provides the mechanistic basis for the kinetochore's end coupling, enabling its slip-clutch behavior.
    DOI:  https://doi.org/10.1126/sciadv.adx0005
  7. Methods Mol Biol. 2025 ;2968 401-413
    Investigating Nuclear Envelope Assembly on Mis-Segregated Chromosomes.
    Shiwei Liu.
      During mitotic exit in metazoans, the properly segregated chromosome mass is typically enclosed by the newly formed nuclear envelope to form a single nucleus in each daughter cell. On the other hand, mis-segregated chromosomes that lag behind can also undergo nuclear envelope assembly, leading to the formation of atypical nuclear structures such as micronuclei. Micronuclei are commonly observed in cancer and are known to cause extensive genome alterations such as chromothripsis. Recent studies highlight that micronuclei frequently exhibit fragile nuclear envelopes and undergo defective nuclear envelope assembly, which are linked to numerous adverse consequences, including abnormal DNA replication, DNA damage, transcriptional defects, and proinflammatory immune responses. In this chapter, I describe methods to examine nuclear envelope assembly on micronuclei during chromosome mis-segregation.
    Keywords:  Chromosome mis-segregation; Micronuclei; Mitosis; Nuclear envelope assembly
    DOI:  https://doi.org/10.1007/978-1-0716-4750-9_24
  8. Biol Res. 2025 Aug 29. 58(1): 59
    The unique contributions of Rab11 and Rab35 to the completion of cell division.
    Paulius Gibieža, Emilija Ratkevičiūtė, Girstautė Dabkevičiūtė, Vilma Petrikaitė.
      Rab11 and Rab35 have been implicated in large-scale intracellular membrane trafficking during the last phases of the cell cycle. Although both proteins are associated with cytokinetic abscission, they appear to perform distinct functions and give rise to different phenotypes in dividing cells. Despite a substantial body of research on each protein individually, no study to date has systematically compared Rab11 and Rab35 in the context of cancer cell division. As a result, the extent of their interrelationship and potential compensatory mechanisms remains unclear. Our data demonstrate that Rab11a, Rab11b and Rab35 expression levels are partially interrelated. We also show that Rab11 and Rab35 contribute to mitotic progression in different ways, particularly during specific stages of the M-phase. Notably, depletion of either Rab11 or Rab35 disrupts cytokinetic abscission and correlates with aberrant F-actin accumulation at the intercellular bridge. Furthermore, overexpression of related Rab proteins with overlapping functions does not rescue the cytokinetic defects caused by Rab11 or Rab35 downregulation in cancer cells. Therefore, this study aims to deepen our understanding of how Rab11 and Rab35 orchestrate the molecular events that drive the progression from late anaphase through the completion of cytokinesis.
    Keywords:  Abscission; Cytokinesis; Division; Rab11; Rab35; Telophase
    DOI:  https://doi.org/10.1186/s40659-025-00638-x
  9. Chromosome Res. 2025 Aug 30. 33(1): 19
    The centromere: the punching bag of the chromosome.
    Annapaola Angrisani, Daniele Fachinetti.
      The centromere is a region present on every human chromosome that is essential for mediating chromosome segregation and maintaining genome stability. However, despite its fundamental role in the process of cell division, the centromere is constantly subjected to a wide range of stresses that can challenge their integrity, causing breakages and aneuploidy. In this review, we will examine the plethora of stresses that challenge the centromere, its stress response and how cells cope with perturbations originating from the intracellular and extracellular microenvironment in order to preserve centromere function and, overall, cellular fitness.
    Keywords:  Aneuploidy; Centromere; Centromere fragility; Genome instability; Stress
    DOI:  https://doi.org/10.1007/s10577-025-09778-y
  10. Am J Obstet Gynecol. 2025 Aug 28. pii: S0002-9378(25)00588-5. [Epub ahead of print]
    Farnesylation-Dependent Kinetochore Targeting of CENP-F Is Essential for Oocyte Meiotic Progression and Female Fertility.
    Ou Zhong, Congjing Wang, Junqiang Zhang, Xiaolan Zhang, Ximan Rui, Qiqi Cao, Xinru Jia, Pinhua Wang, Jie Ding, Xiufeng Ling, Hong Li, Qingxia Meng, Chun Zhao, Ran Huo.
       BACKGROUND: During mammalian oocyte meiosis, accurate chromosome segregation critically depends on precise regulation of kinetochore-microtubule (K-MT) attachments, a process monitored by the spindle assembly checkpoint (SAC). While CENP-F has been well characterized as a kinetochore-associated protein that stabilizes K-MT connections during mitosis, its functional mechanisms during meiosis remain poorly understood. In particular, there is still controversy over whether farnesylation modification governs localization and functionality of CENP-F. Concurrently, clinical investigations face a knowledge gap regarding the genetic basis of oocyte maturation arrest, a prevalent phenotype observed in female infertility patients.
    OBJECTIVE: This study aims to reveal the regulatory mechanism of CENP-F farnesylation modification on its meiotic function and explore the association between CENP-F gene mutations and female oocyte maturation disorders.
    STUDY DESIGN: Previous studies have shown that CENP-F is essential for chromosome segregation during mitosis, but its functional mechanism during meiosis remains poorly understood. Oocyte microinjection, western blotting, co-immunoprecipitation (Co-IP), and immunofluorescence were used to explore the localization and function of CENP-F in oocytes. The role of CENP-F farnesylation in mouse oocytes was investigated using pharmacological (farnesyltransferase inhibitor treatment) and genetic (C3111S point mutation) methods. Subsequently, four patients with CENP-F mutations were identified in the whole-exome sequencing (WES) dataset consisting of 179 infertile patients with oocyte maturation disorders. Mouse oocyte and 293T cell models were used to verify the mechanism of patient-derived CENP-F mutations causing oocyte maturation disorders.
    RESULTS: Microinjection of Cenp-f siRNA into mouse oocytes significantly reduced maturation rates (77.84±2.087% vs 34.26±4.748%, P<.01), with the majority arrested at metaphase I (MI) (17.69±2.207% vs 44.93±5.539%, P<.05). Time-course immunofluorescence analysis revealed dynamic CENP-F localization: initially dispersed across chromosome following nuclear envelope breakdown (NEBD), then progressively accumulating at kinetochores by MI. Co-IP assays confirmed a direct interaction between CENP-F and AURKB. Knockdown of AURKB would damage the kinetochore localization of CENP-F in oocytes. Farnesylation inhibition (via farnesyltransferase inhibitor or C3111S mutation) significantly decreased oocyte maturation rates (75.58±3.703% vs 46.18±1.282%, P<.01; 75.58±3.703% vs 44.04±2.541%, P<.01), concomitantly weakening interaction between CENP-F and AURKB (P<.01) and disrupting kinetochore localization. Genetic screening identified four CENP-F mutations in 179 infertile women with oocyte maturation arrest. Microinjection of patient-derived mutant CENP-F cRNAs into mouse oocytes significantly reduced maturation rates (77.00±2.411% vs 49.10±6.561%, P<.01; 77.00±2.411% vs35.43±1.035%, P<.01; 77.00±2.411% vs 55.43±1.288%, P<.05; 77.00±2.411% vs 40.00±4.187%, P<.01). Two of these mutations (K1708T/S1971fs) can reduce the farnesylation of CENP-F (P<.05/P<.01), damage its interaction with AURKB (P<0.05/P<0.01), and disrupt the kinetochore localization. Both CENP-F depletion and patient mutations induced constitutive SAC activation, and the treatment with SAC inhibitor partially rescued the meiotic arrest phenotype in oocytes (P<.05).
    CONCLUSION: This study represents the first demonstration of a direct association between CENP-F genetic defects and human infertility, uncovering a novel farnesylation-dependent mechanism that governs meiotic progression, while simultaneously identifying CENP-F as a potential molecular marker for diagnosing oocyte maturation failure.
    Keywords:  CENP-F; Farnesylation; Female infertility; Kinetochore; Oocyte metaphase I arrest; Spindle assembly checkpoint
    DOI:  https://doi.org/10.1016/j.ajog.2025.08.031
  11. J Cell Biol. 2025 Oct 06. pii: e202209025. [Epub ahead of print]224(10):
    Stu2 performs an essential kinetochore function independent of its microtubule polymerase activity.
    Ahmed A Abouelghar, Joseph S Carrier, Julia R Torvi, Erin Jenson, Chloe Jones, Binnu Gangadharan, Elisabeth G Prinslow, Luke M Rice, Brent Lagesse, Georjana Barnes, Matthew P Miller.
      ch-TOG family proteins, including the budding yeast Stu2, are essential for spindle formation and chromosome segregation. Such functions depend on an array of activities ranging from microtubule nucleation, polymerization, and depolymerization to conferring tension sensitivity to kinetochores. This functional diversity makes it challenging to dissect these various functions and understand their relative importance. Here, we developed separation-of-function mutants and used artificial tethering tools to elucidate several important mechanistic insights into Stu2's essential role. We show that Stu2's microtubule polymerization activity depends on its basic linker region but is surprisingly dispensable for viability; that in fact, Stu2 carries out an essential kinetochore-associated function; and finally, that Stu2's precise location within the kinetochore is critical for its function, suggesting a spatial separation mode of action may underlie its ability to confer tension sensitivity. Our findings highlight the significance of Stu2's kinetochore role and provide insights into the molecular mechanisms by which it performs its various functions.
    DOI:  https://doi.org/10.1083/jcb.202209025
  12. Methods Mol Biol. 2025 ;2968 415-440
    Transcription-Replication Conflicts and Incomplete Replication as a Cause of Micronuclei-Driven Chromoanagenesis.
    Hervé Técher, Philippe Pasero.
      Cancers are characterized with altered genomes. Sequencing of thousands of cancer genomes has led to the identification of new types of complex genomic rearrangements that generate new chromosomes, known as chromoanagenesis. Chromothripsis is, to-date, the best characterized phenomenon of complex rearrangements, in which a single chromosome pulverization is followed by reassembly of broken DNA fragments in a random manner. Chromothripsis and chromothripsis-related events predominantly stem from mitotic- and post-mitotic aberrations, notably in consequence of chromatin bridges and micronuclei breakage. These mitotic defects result either from DNA breaks or from perturbations in the DNA replication program, leading to under-replication and DNA damage. In this chapter we describe the molecular mechanisms that connect replication stress to chromothripsis-related events. We focus on transcription-replication conflicts as a major source of endogenous replication stress.
    Keywords:  Cancer; Chromothripsis; DNA breaks; Micronuclei; Mitotic bridges; RNaseH2; Replication stress; TREX1; Transcription-replication conflicts
    DOI:  https://doi.org/10.1007/978-1-0716-4750-9_25
  13. Zygote. 2025 Sep 01. 1-8
    Effects of reversine and proTAME treatment on chromosome segregation during mouse oocyte maturation.
    Shiina Yonekura, Chihiro Hasegawa, Shoma Ochi, Yoh Kinoshita, Jin Shibata, Mizuho Kobayashi, Hikari Ikema, Akifumi Nakata, Tomisato Miura, Hideaki Yamashiro.
      Aneuploidy in oocytes is a leading cause of implantation failure, miscarriage and congenital disorders. During meiosis, proper timing of chromosome segregation is regulated by the spindle assembly checkpoint (SAC) and the anaphase-promoting complex/cyclosome (APC/C). However, how pharmacological manipulation of these regulatory pathways affects aneuploidy remains incompletely understood. In this study, we investigated whether SAC inhibition by reversine induces aneuploidy in mouse oocytes and whether partial inhibition of APC/C by proTAME can alleviate these errors. Germinal vesicle (GV) oocytes were matured in vitro in the presence of various concentrations of reversine. To optimize the timing of treatment, oocytes were exposed to reversine for 0, 3, 5 or 7 h, followed by culture with or without proTAME. A proTAME-only group (2.5 nM) was also included. Chromosome spreads were analyzed at the metaphase II (MII) stage to determine aneuploidy rates. Reversine (5 nM) yielded an MII maturation rate of 80.5% but induced a high aneuploidy rate of 77.0%. Sequential treatment with 2.5 nM proTAME significantly reduced aneuploidy to 33.3%. In contrast, proTAME alone led to 79.0% aneuploidy, suggesting its effect is contingent upon prior SAC disruption. These results indicate that reversine compromises chromosomal integrity, while appropriately timed, low-dose proTAME can partially rescue segregation errors. Our findings underscore the potential of pharmacologically regulating APC/C activity to reduce aneuploidy and enhance oocyte quality, offering new avenues for improving outcomes in assisted reproductive technologies.
    Keywords:  aneuploidy; chromosome segregation; meiosis; proTAME; reversine
    DOI:  https://doi.org/10.1017/S0967199425100117
  14. FEBS J. 2025 Aug 28.
    Lysine demethylase 4A is a centrosome-associated protein required for centrosome integrity and genomic stability.
    Pratim Chowdhury, Xiaoli Wang, Richard I Han, Manga Motrapu, Ashley G Boice, Yuya Nakatani, Sofia Vargas-Hernandez, Julia F Love, Claude Chew, Sandra L Grimm, Dereck Mezquita, Frank M Mason, Elisabeth D Martinez, Cristian Coarfa, Cheryl L Walker, Anna-Karin Gustavsson, Ruhee Dere.
      Centrosomes play a fundamental role in nucleating and organizing microtubules in the cell and are vital for faithful chromosome segregation and maintenance of genomic stability. Loss of structural or functional integrity of centrosomes causes genomic instability and is a driver of oncogenesis. Here we identify lysine demethylase 4A (KDM4A), an epigenetic 'eraser' of chromatin methyl marks, as a centrosome-localized protein, visualized at the nanometer-scale resolution. We additionally uncovered that KDM4A demethylase enzymatic activity is required to maintain centrosome homeostasis and integrity; a previously unknown functionality unlinked to altered expression of genes regulating centrosome number. We find that KDM4A interacts with and localizes to the centrosome in all stages of mitosis, where it maintains centrosome numbers and centriole engagement during mitosis. Loss of KDM4A results in supernumerary centrosomes and accrual of chromosome segregation errors including chromatin bridges and micronuclei, markers of genomic instability. In summary, these data highlight a previously unknown role for an epigenetic 'eraser' regulating centrosome integrity, mitotic fidelity, and genomic stability at the centrosome.
    Keywords:  KDM4A; abnormal mitosis; centrosomes; genomic instability; mitosis
    DOI:  https://doi.org/10.1111/febs.70240
  15. Stud Health Technol Inform. 2025 Sep 03. 331 339-345
    Classifying the AMi-Br Mitotic Figure Dataset with AUCMEDI.
    Daniel Hieber, Friederike Lische-Starnecker, Johannes Schobel, Rüdiger Pryss, Frank Kramer, Dominik Müller.
       INTRODUCTION: Mitotic figure (MF) density has been established as a key biomarker for certain tumors. Recently, the differentiation between atypical MFs (AMF) and normal MFs (NMFs) has gained increased interest in research, as AMFs density could be an independent biomarker. This results in the challenge of finding an automated, deterministic way to differentiate between AMFs and NMFs.
    METHODS: In this study, the AUCMEDI deep learning framework is applied to the recently published AMi-Br dataset to get a first bearing on the complexity of the task at hand. The dataset includes eight mitotic subclasses derived from breast cancer samples, four for NMFs and four for AMF. Using a patient-level cross- validation strategy and a ConvNeXt-based ensemble, we trained and evaluated an eight-class subtype classification model.
    RESULTS: Our results show high specificity across all classes (≥ 90%), but sensitivity varies significantly between mitotic subclasses (0-82%), reflecting the dataset's inherent challenges. The mean AUC of 85.90% outperforms the binary classification baseline (69.8%).
    CONCLUSION: The results highlight the promise of progress in subclass-level mitotic analysis while pointing to areas for further model refinement.
    Keywords:  Atypical Mitotic Figures; Classification; Computational Pathology; Computer Vision; Deep Learning
    DOI:  https://doi.org/10.3233/SHTI251413
  16. Methods Mol Biol. 2025 ;2968 373-383
    The Fate of Micronuclei.
    Henning Hintzsche, Helga Stopper.
      This chapter provides a brief overview about micronuclei and their postmitotic fate. Micronuclei are small chromatin-containing bodies formed during mitosis and located in the cytoplasm. Micronuclei have been known for more than 100 years and used as biomarkers for decades, but their fate after formation and with that their biological relevance for the organism has only been addressed in recent years. Four major fates of micronuclei are known: extrusion, reincorporation, degradation, and persistence. Generally, most micronuclei persist without any changes. Around one quarter of the micronuclei are reincorporated into the main nucleus during one of the next mitoses. Degradation and extrusion only occur rarely under special circumstances. Mechanistic backgrounds are still not well understood.
    Keywords:  Chromosomal instability; DNA damage; Micronucleated cells; Micronuclei; Postmitotic fate
    DOI:  https://doi.org/10.1007/978-1-0716-4750-9_22
  17. Elife. 2025 Sep 01. pii: RP104238. [Epub ahead of print]14
    Development of D-box peptides to inhibit the anaphase-promoting complex/cyclosome.
    Rohan Eapen, Cynthia Okoye, Christopher Stubbs, Marianne Schimpl, Thomas Tischer, Eileen J Fisher, Maria Zacharopoulou, Fernando Ferrer, David Barford, David R Spring, Catherine Lindon, Christopher Phillips, Laura S Itzhaki.
      E3 ubiquitin ligases engage their substrates via 'degrons' - short linear motifs typically located within intrinsically disordered regions of substrates. As these enzymes are large, multi-subunit complexes that generally lack natural small-molecule ligands and are difficult to inhibit via conventional means, alternative strategies are needed to target them in diseases, and peptide-based inhibitors derived from degrons represent a promising approach. Here we explore peptide inhibitors of Cdc20, a substrate-recognition subunit and activator of the E3 ubiquitin ligase the anaphase-promoting complex/cyclosome (APC/C) that is essential in mitosis and consequently of interest as an anti-cancer target. APC/C engages substrates via degrons that include the 'destruction box' (D-box) motif. We used a rational design approach to construct binders containing unnatural amino acids aimed at better filling a hydrophobic pocket that contributes to the D-box binding site on the surface of Cdc20. We confirmed binding by thermal-shift assays and surface plasmon resonance and determined the structures of a number of the Cdc20-peptide complexes. Using a cellular thermal shift assay, we confirmed that the D-box peptides also bind to and stabilise Cdc20 in the cell. We found that the D-box peptides inhibit ubiquitination activity of APC/CCdc20 and are more potent than the small-molecule inhibitor Apcin. Lastly, these peptides function as portable degrons capable of driving the degradation of a fused fluorescent protein. Interestingly, we find that although inhibitory activity of the peptides correlates with Cdc20-binding affinity, degradation efficacy does not, which may be due to the complex nature of APC/C regulation and effects of degron binding of subunit recruitment and conformational changes. Our study lays the groundwork for the further development of these peptides as molecular therapeutics for blocking APC/C as well as potentially for harnessing the APC/C for targeted protein degradation.
    Keywords:  APC/C; E. coli; anaphase-promoting complex/cyclosome; biochemistry; chemical biology; degron; human; peptide inhibitor; protein–protein interaction; ubiquitin
    DOI:  https://doi.org/10.7554/eLife.104238
  18. Nat Genet. 2025 Sep 04.
    DNA methylation influences human centromere positioning and function.
    Catalina Salinas-Luypaert, Danilo Dubocanin, Rosa Jooyoung Lee, Lorena Andrade Ruiz, Riccardo Gamba, Marine Grison, Leonid Velikovsky, Annapaola Angrisani, Andrea Scelfo, Yuan Xu, Marie Dumont, Viviana Barra, Therese Wilhelm, Guillaume Velasco, Marialucrezia Losito, René Wardenaar, Claire Francastel, Floris Foijer, Geert J P L Kops, Karen H Miga, Nicolas Altemose, Daniele Fachinetti.
      Maintaining the epigenetic identity of centromeres is essential to prevent genome instability. Centromeres are epigenetically defined by the histone H3 variant CENP-A. Prior work in human centromeres has shown that CENP-A is associated with regions of hypomethylated DNA located within large arrays of hypermethylated repeats, but the functional importance of these DNA methylation (DNAme) patterns remains poorly understood. To address this, we developed tools to perturb centromeric DNAme, revealing that it causally influences CENP-A positioning. We show that rapid loss of methylation results in increased binding of centromeric proteins and alterations in centromere architecture, leading to aneuploidy and reduced cell viability. We also demonstrate that gradual centromeric DNA demethylation prompts a process of cellular adaptation. Altogether, we find that DNAme causally influences CENP-A localization and centromere function, offering mechanistic insights into pathological alterations of centromeric DNAme.
    DOI:  https://doi.org/10.1038/s41588-025-02324-w
  19. J Cell Sci. 2025 Sep 01. pii: jcs.263766. [Epub ahead of print]
    Acentrosomal aster with atypical microtubule polarity recruits cytokinesis signals to its center in Xenopus egg extracts.
    Ling Jin, Muchen Liu, Xianrui Cheng.
      Xenopus egg extracts can self-organize into cell-like compartments without the classic microtubule organizer centrosome. Compartment formation requires microtubules, but the organization of microtubules throughout the process remains unclear. Here, we show that the earliest organized microtubule structures to emerge during cell-like compartment formation are centrosome-independent asters. In contrast to the microtubule orientation of a centrosome-nucleated aster, most microtubules in the centrosome-independent aster point their plus ends toward the center. Formation of these asters requires the microtubule motor MKLP2 and Aurora kinase B activity. The aster center accumulates microtubule plus end-binding protein EB1-GFP and the plus end-tracking motor kinesin-1-GFP, and also recruits cytokinesis related proteins GFP-MKLP1, active RhoA, and F-actin. Together, our findings identify an early microtubule structure in cell-like compartment self-organization and link it to the cytokinesis pathway.
    Keywords:  Aster; Cytokinesis; Microtubules; Motors; Self-organization; Xenopus egg extracts
    DOI:  https://doi.org/10.1242/jcs.263766
  20. Plant J. 2025 Aug;123(4): e70453
    The making of a leaf tip: how cell division angles define shape.
    Martin Balcerowicz.
      
    DOI:  https://doi.org/10.1111/tpj.70453
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