bims-micesi 2025-02-02 papers

Issue of 2025–02–02
seven papers selected by
Valentina Piano, Uniklinik Köln

Cell. 2025 Jan 23. pii: S0092-8674(24)01467-3. [Epub ahead of print]

Centromeric chromatin clearings demarcate the site of kinetochore formation.

Kathryn Kixmoeller, Ekaterina V Tarasovetc, Elie Mer, Yi-Wei Chang, Ben E Black.

The centromere is the chromosomal locus that recruits the kinetochore, directing faithful propagation of the genome during cell division. Using cryo-ET on human mitotic chromosomes, we reveal a distinctive architecture at the centromere: clustered 20- to 25-nm nucleosome-associated complexes within chromatin clearings that delineate them from surrounding chromatin. Centromere components CENP-C and CENP-N are each required for the integrity of the complexes, while CENP-C is also required to maintain the chromatin clearing. We find that CENP-C is required in mitosis, not just for kinetochore assembly, likely reflecting its role in organizing the inner kinetochore during chromosome segregation. We further visualize the scaffold of the fibrous corona, a structure amplified at unattached kinetochores, revealing crescent-shaped parallel arrays of fibrils extending >1 μm. Thus, we reveal how the organization of centromeric chromatin creates a clearing at the site of kinetochore formation as well as the nature of kinetochore amplification mediated by corona fibrils.

Keywords: centromere; chromatin; chromosome; cryo-ET; kinetochore; mitosis; mitotic chromosome; nucleosome

DOI: https://doi.org/10.1016/j.cell.2024.12.025

Proc Natl Acad Sci U S A. 2025 Feb 04. 122(5): e2416459122

Optimal strategies for correcting merotelic chromosome attachments in anaphase.

Evgenii Kliuchnikov, Kenneth A Marx, Valeri Barsegov, Alex Mogilner.

Accurate chromosome segregation in mitosis depends on proper connections of sister chromatids, through microtubules, to the opposite poles of the early mitotic spindle. Transiently, many inaccurate connections are formed and rapidly corrected throughout the mitotic stages, but a small number of merotelic connections, in which a chromatid is connected to both spindle poles, remain lagging at the spindle's equator in anaphase. Most of the lagging chromatids are eventually moved to one or the other pole, likely by a combination of microtubules' turnover and the brute force of pulling by the microtubules' majority from the one pole against the microtubules' minority from the other pole. We use computer simulations from two stochastic models (1D and full 3D CellDynaMo model) combining force balances and microtubules' dynamics for the lagging chromatids to investigate what maximizes the percentage of segregated laggards. We find that a) brute force tug-of-war with slow (< 0.0001 s-1) microtubules' detachment rate can move asymmetric laggards to the poles in limited time, b) rapid (> 0.01 s-1) microtubules' detachment rate leads to a significant loss of the laggards, and c) intermediate (~ 0.001 s-1) microtubules' detachment rate ensures higher than 90% accuracy of segregation. The simulations also shed light on the waiting time required to correct the merotelic errors in anaphase and on the roles of chromatid-attached microtubule number and Aurora B-mediated, spatially graded regulation of microtubule kinetics in anaphase.

Keywords: 3D computational modeling; anaphase; merotelic errors; tug-of-war

DOI: https://doi.org/10.1073/pnas.2416459122

Front Biosci (Landmark Ed). 2025 Jan 21. 30(1): 26426

HP1 Promotes the Centromeric Localization of ATRX and Protects Cohesion by Interfering Wapl Activity in Mitosis.

Erchen Zhang, Lei Peng, Kejia Yuan, Zexian Ding, Qi Yi.

BACKGROUND: α thalassemia/mental retardation syndrome X-linked (ATRX) serves as a part of the sucrose nonfermenting 2 (SNF2) chromatin-remodeling complex. In interphase, ATRX localizes to pericentromeric heterochromatin, contributing to DNA double-strand break repair, DNA replication, and telomere maintenance. During mitosis, most ATRX proteins are removed from chromosomal arms, leaving a pool near the centromere region in mammalian cells, which is critical for accurate chromosome congression and sister chromatid cohesion protection. However, the function and localization mechanisms of ATRX at mitotic centromeres remain largely unresolved.
METHODS: The clustered regularly interspaced short palindromic repeats with CRISPR-associated protein 9 (CRISPR-Cas9) system and overexpression approaches were employed alongside immunofluorescence to investigate the mechanism of ATRX localization at the centromere. To study the binding mechanism between ATRX and heterochromatin protein 1 (HP1), both full-length and truncated mutants of hemagglutinin (HA)-ATRX were generated for co-immunoprecipitation and glutathione S-transferase (GST)-pull assays. Wild-type ATRX and HP1 binding-deficient mutants were created to investigate the role of ATRX binding to HP1 during mitosis, with the Z-Leu-Leu-Leu-al (MG132) maintenance assay, cohesion function assay, and kinetochore distance measurement.
RESULTS AND CONCLUSIONS: Our research demonstrated that HP1α, HP1β, and HP1γ facilitate the positioning of ATRX within the mitotic centromere area through their interaction with the first two [P/L]-X-V-X-[M/L/V] (PxVxL)motifs at the N-terminus of ATRX. ATRX deficiency causes aberrant mitosis and decreased centromeric cohesion. Furthermore, reducing Wapl activity can bypass the need for ATRX to protect centromeric cohesion. These results provide insights into the mechanism of ATRX's centromeric localization and its critical function in preserving centromeric cohesion by reducing Wapl activity in human cells.

Keywords: ATRX; HP1; Wapl; chromosomal instability; cohesion

DOI: https://doi.org/10.31083/FBL26426

BMC Cancer. 2025 Jan 24. 25(1): 143

Interplay of aurora kinase a functional residues and Epstein-barr Nuclear Antigen 1 in Epstein-barr virus associated Gastric cancer using AGS cells.

Nidhi Varshney, Siddharth Singh, Meenakshi Kandpal, Vaishali Saini, Erle S Roberston, Hem Chandra Jha.

Epstein-Barr virus (EBV), an oncogenic gamma-herpesvirus, belongs to group 1 carcinogen and is implicated in various cancers, including gastric cancer. Aurora Kinase A is a major mitotic protein kinase that regulates mitotic progression; overexpression and hyperactivation of AURKA commonly promote genomic instability in many tumours. However, the relationship of functional residues of AURKA and EBV in gastric cancer progression remains unknown. We reveal that AURKA overexpression and EBV infection induce aneuploidy in gastric epithelial cells. The AURKA (S89) N-terminal residue is critical for the centrosome maturation process in EBV-infected gastric epithelial cells. The kinase domain residues T287 and T288 of AURKA are essential for centrosome maturation and bipolar spindle formation in EBV-infected gastric cancer cells. We also show that AURKA 287/288 dm reduces the transcript expression of cell cycle markers involved in mitotic entry in EBV infection. This mutant also enhanced the protein expression of p53 and Rb, which was reduced in EBV infection and decreased the Survivin expression. Further, EBNA1, the latent gene of EBV, stabilises the AURKA in its wild-type form and S89A mutant but unable to stabilise in T287/288A double mutant. These mutants also induce mitotic catastrophe by regulating the apoptosis and autophagy pathway in EBV infection. AURKA287/288 dm also promotes autophagosome formation even in EBV infection. Thus, this study demonstrates that the AURKA kinase domain is essential for its functioning and progression of the oncogenesis of EBV-infected gastric epithelial cells.

Keywords: Aurora Kinase A; Epstein-Barr Nuclear Antigen 1; Epstein-Barr Virus; Gastric cancer; Microtubule polymerisation; Stability assay

DOI: https://doi.org/10.1186/s12885-024-13260-z

Cell Commun Signal. 2025 Jan 20. 23(1): 35

NKX6.3 modulation of mitotic dynamics and genomic stability in gastric carcinogenesis.

Jung Hwan Yoon, Jeong-Kyu Kim, Jung Woo Eun, Hassan Ashktorab, Duane T Smoot, Suk Woo Nam, Won Sang Park.

BACKGROUND: Gastric cancer remains a significant global health challenge, characterized by poor prognosis and high mortality rates. Mitotic integrity and genomic stability are crucial in maintaining cellular homeostasis and preventing tumorigenesis. The transcription factor NKX6.3 has emerged as a potential regulator of these processes in gastric epithelial cells, prompting an investigation into its role in gastric cancer development.
METHODS: We employed a combination of in vitro and in vivo techniques to elucidate the impact of NKX6.3 depletion on mitotic dynamics and genomic stability in gastric epithelial cells. Quantitative real-time PCR and Western blot analyses were conducted to assess the expression of mitosis-related genes and proteins. Flow cytometry was utilized to evaluate cell cycle distribution, while immunofluorescence microscopy enabled the visualization of mitotic abnormalities. Statistical analyses, including Student's t-test and ANOVA, were performed to determine the significance of our findings.
RESULTS: Our results demonstrate that NKX6.3 depletion leads to significant mitotic defects, characterized by increased chromosome misalignment and lagging chromosomes during anaphase. These abnormalities corresponded with elevated levels of genomic instability markers, indicating compromised genomic integrity. Furthermore, the loss of NKX6.3 resulted in altered expression of key regulatory proteins involved in mitosis and DNA repair pathways, suggesting a mechanistic link between NKX6.3 and the maintenance of genomic stability in gastric epithelial cells. Depletion of NKX6.3 resulted in accelerated cell cycle progression and the formation of abnormal mitotic figures, leading to genomic instability characterized by increased DNA content and structural abnormalities. In both in vitro and xenograft models, the depletion of NKX6.3 significantly upregulated AurkA and TPX2, which correlated with gains in DNA copy number. An inverse relationship was observed between NKX6.3 expression and the levels of AurkA and TPX2 in human gastric cancer tissues.
CONCLUSIONS: This study highlights the essential role of NKX6.3 in regulating mitotic integrity and genomic stability in gastric carcinogenesis. The findings suggest that targeting NKX6.3 may offer a novel therapeutic strategy for improving treatment outcomes in gastric cancer by restoring mitotic fidelity and genomic stability.
TRIAL REGISTRATION: This study was not registered.

Keywords: Gastric carcinogenesis; Genomic stability; Mitotic integrity; NKX6.3

DOI: https://doi.org/10.1186/s12964-025-02030-4

Contact (Thousand Oaks). 2025 Jan-Dec;8:8 25152564241309207

Remodeling of ER Membrane Contact Sites During Cell Division.

Fang Yu, Khaled Machaca.

Membrane contact sites (MCS) provide specialized conduits for inter-organelle communications to maintain cellular homeostasis. Most organelles are interconnected, which supports their coordination and function. M-phase (mitosis or meiosis) is associated with dramatic cellular remodeling to support cell division, including the equal distribution of organelles to the two daughter cells. However, the fate of MCS in M-phase is poorly understood. Here we review recent advances arguing for differential remodeling of endoplasmic reticulum (ER) MCS with the plasma membrane (PM, ERPMCS) and the mitochondria (MERCS) during cell division.

Keywords: ERPMCS; MERCS; cell division; endoplasmic reticulum; meiosis; membrane contact sites; mitochondrion (mitochondria); mitosis

DOI: https://doi.org/10.1177/25152564241309207

Gynecol Endocrinol. 2025 Dec;41(1): 2451672

Biallelic mutations in CDC20 cause female infertility due to oocyte maturation abnormality.

Guangzhong Jiao, Jinhao Xing, Zhaoli Du, Hongchu Bao, Xiaoyan Liu.

Oocyte maturation arrest (OMA) may occur at different stages, including the germinal vesicle (GV), metaphase I (MI), and metaphase II (MII). A total maturation arrest of human oocytes is rarely observed during in vitro fertilization (IVF). We have identified a case of infertile female for whom all oocytes fail to mature and are arrested at MI. Whole-exome sequencing revealed a compound heterozygous mutant (c.533C > A: p.Val458Ala; c.1373T > C: p.Ala178Glu) in cell division cycle 20 (CDC20). Through rigorous validation using Sanger sequencing technology, both of her parents have been confirmed as genetic carriers of these specific mutations. Based on the three-dimensional (3D) structures of the CDC20 protein used to assess the effect of the mutant, the mutant causes a change in hydrogen bond in the protein structure, which may affect the stability of the mutant protein. Previous studies have firmly established CDC20 as a pivotal member of the cell cycle regulation family, playing an indispensable role in the transition from metaphase to anaphase during cell division. Our findings not only broaden the current understanding of CDC20 gene mutations but also profoundly illuminate how these mutations serve as potential genetic mechanisms underlying the arrest of oocyte maturation.

Keywords: CDC20; Female infertility; IVF; mutation; oocyte maturation arrest

DOI: https://doi.org/10.1080/09513590.2025.2451672