bims-micesi Biomed News
on Mitotic cell signalling
Issue of 2024–05–12
fiveteen papers selected by
Valentina Piano, Uniklinik Köln
  1. Centromeric chromatin clearings demarcate the site of kinetochore formation.
  2. Chromosome size-dependent polar ejection force impairs mammalian mitotic error correction.
  3. Arabidopsis α-Aurora kinase plays a role in cytokinesis through regulating MAP65-3 association with microtubules at phragmoplast midzone.
  4. A human papillomavirus 16 E2-TopBP1 dependent SIRT1-p300 acetylation switch regulates mitotic viral and human protein levels and activates the DNA damage response.
  5. A non-canonical role of the inner kinetochore in regulating sister-chromatid cohesion at centromeres.
  6. Binucleated human hepatocytes arise through late cytokinetic regression during endomitosis M phase.
  7. Translational control of MPS1 links protein synthesis with the initiation of cell division and spindle pole body duplication in Saccharomyces cerevisiae.
  8. Cell growth and nutrient availability control the mitotic exit signaling network in budding yeast.
  9. Chromothripsis: an emerging crossroad from aberrant mitosis to therapeutic opportunities.
  10. Mitotic Kinases Aurora-A, Plk1, and Cdk1 Interact with Elk-1 Transcription Factor through the N-Terminal Domain.
  11. Adducin Regulates Sarcomere Disassembly During Cardiomyocyte Mitosis.
  12. AURKB promotes colorectal cancer progression by triggering the phosphorylation of histone H3 at serine 10 to activate CCNE1 expression.
  13. Metabolic contribution to age-related chromosome missegregation in mammalian oocytes.
  14. Correlative light and electron microscopy at defined cell cycle stages in a controlled environment.
  15. The holocentricity in the dioecious nutmeg (Myristica fragrans) is not based on major satellite repeats.
  1. bioRxiv. 2024 Apr 26. pii: 2024.04.26.591177. [Epub ahead of print]
    Centromeric chromatin clearings demarcate the site of kinetochore formation.
    Kathryn Kixmoeller, 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. The kinetochore has been interrogated by electron microscopy since the middle of the last century, but with methodologies that compromised fine structure. Using cryo-ET on human mitotic chromosomes, we reveal a distinctive architecture at the centromere: clustered 20-25 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 further visualize the scaffold of the fibrous corona, a structure amplified at unattached kinetochores, revealing crescent-shaped parallel arrays of fibrils that extend >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.
    DOI:  https://doi.org/10.1101/2024.04.26.591177
  2. J Cell Biol. 2024 Aug 05. pii: e202310010. [Epub ahead of print]223(8):
    Chromosome size-dependent polar ejection force impairs mammalian mitotic error correction.
    Megan K Chong, Miquel Rosas-Salvans, Vanna Tran, Sophie Dumont.
      Accurate chromosome segregation requires sister kinetochores to biorient, attaching to opposite spindle poles. To this end, the mammalian kinetochore destabilizes incorrect attachments and stabilizes correct ones, but how it discriminates between these is not yet clear. Here, we test the model that kinetochore tension is the stabilizing cue and ask how chromosome size impacts that model. We live image PtK2 cells, with just 14 chromosomes, widely ranging in size, and find that long chromosomes align at the metaphase plate later than short chromosomes. Enriching for errors and imaging error correction live, we show that long chromosomes exhibit a specific delay in correcting attachments. Using chromokinesin overexpression and laser ablation to perturb polar ejection forces, we find that chromosome size and force on arms determine alignment order. Thus, we propose a model where increased force on long chromosomes can falsely stabilize incorrect attachments, delaying their biorientation. As such, long chromosomes may require compensatory mechanisms for correcting errors to avoid chromosomal instability.
    DOI:  https://doi.org/10.1083/jcb.202310010
  3. Nat Commun. 2024 May 06. 15(1): 3779
    Arabidopsis α-Aurora kinase plays a role in cytokinesis through regulating MAP65-3 association with microtubules at phragmoplast midzone.
    Xingguang Deng, Yu Xiao, Xiaoya Tang, Bo Liu, Honghui Lin.
      The α-Aurora kinase is a crucial regulator of spindle microtubule organization during mitosis in plants. Here, we report a post-mitotic role for α-Aurora in reorganizing the phragmoplast microtubule array. In Arabidopsis thaliana, α-Aurora relocated from spindle poles to the phragmoplast midzone, where it interacted with the microtubule cross-linker MAP65-3. In a hypomorphic α-Aurora mutant, MAP65-3 was detected on spindle microtubules, followed by a diffuse association pattern across the phragmoplast midzone. Simultaneously, phragmoplast microtubules remained belatedly in a solid disk array before transitioning to a ring shape. Microtubules at the leading edge of the matured phragmoplast were often disengaged, accompanied by conspicuous retentions of MAP65-3 at the phragmoplast interior edge. Specifically, α-Aurora phosphorylated two residues towards the C-terminus of MAP65-3. Mutation of these residues to alanines resulted in an increased association of MAP65-3 with microtubules within the phragmoplast. Consequently, the expansion of the phragmoplast was notably slower compared to wild-type cells or cells expressing a phospho-mimetic variant of MAP65-3. Moreover, mimicking phosphorylation reinstated disrupted MAP65-3 behaviors in plants with compromised α-Aurora function. Overall, our findings reveal a mechanism in which α-Aurora facilitates cytokinesis progression through phosphorylation-dependent restriction of MAP65-3 associating with microtubules at the phragmoplast midzone.
    DOI:  https://doi.org/10.1038/s41467-024-48238-9
  4. mBio. 2024 May 09. e0067624
    A human papillomavirus 16 E2-TopBP1 dependent SIRT1-p300 acetylation switch regulates mitotic viral and human protein levels and activates the DNA damage response.
    Apurva T Prabhakar, Claire D James, Aya H Youssef, Reafa A Hossain, Ronald D Hill, Molly L Bristol, Xu Wang, Aanchal Dubey, Elmira Karimi, Iain M Morgan.
      An interaction between human papillomavirus 16 (HPV16) E2 and the cellular proteins TopBP1 and BRD4 is required for E2 plasmid segregation function. The E2-TopBP1 interaction promotes increased mitotic E2 protein levels in U2OS and N/Tert-1 cells, as well as in human foreskin keratinocytes immortalized by HPV16 (HFK + HPV16). SIRT1 deacetylation reduces E2 protein stability and here we demonstrate that increased E2 acetylation occurs during mitosis in a TopBP1 interacting-dependent manner, promoting E2 mitotic stabilization. p300 mediates E2 acetylation and acetylation is increased due to E2 switching off SIRT1 function during mitosis in a TopBP1 interacting-dependent manner, confirmed by increased p53 stability and acetylation on lysine 382, a known target for SIRT1 deacetylation. SIRT1 can complex with E2 in growing cells but is unable to do so during mitosis due to the E2-TopBP1 interaction; SIRT1 is also unable to complex with p53 in mitotic E2 wild-type cells but can complex with p53 outside of mitosis. E2 lysines 111 and 112 are highly conserved residues across all E2 proteins and we demonstrate that K111 hyper-acetylation occurs during mitosis, promoting E2 interaction with Topoisomerase 1 (Top1). We demonstrate that K112 ubiquitination promotes E2 proteasomal degradation during mitosis. E2-TopBP1 interaction promotes mitotic acetylation of CHK2, promoting phosphorylation and activation of the DNA damage response (DDR). The results present a new model in which the E2-TopBP1 complex inactivates SIRT1 during mitosis, and activates the DDR. This is a novel mechanism of HPV16 activation of the DDR, a requirement for the viral life cycle.
    IMPORTANCE: Human papillomaviruses (HPVs) are causative agents in around 5% of all human cancers. While there are prophylactic vaccines that will significantly alleviate HPV disease burden on future generations, there are currently no anti-viral strategies available for the treatment of HPV cancers. To generate such reagents, we must understand more about the HPV life cycle, and in particular about viral-host interactions. Here, we describe a novel mitotic complex generated by the HPV16 E2 protein interacting with the host protein TopBP1 that controls the function of the deacetylase SIRT1. The E2-TopBP1 interaction disrupts SIRT1 function during mitosis in order to enhance acetylation and stability of viral and host proteins. We also demonstrate that the E2-TopBP1 interaction activates the DDR. This novel complex is essential for the HPV16 life cycle and represents a novel anti-viral therapeutic target.
    Keywords:  E2; SIRT1; TopBP1; acetylation; cervical cancer; chromosome segregation; head and neck cancer; mitosis; p300; papillomavirus; switch
    DOI:  https://doi.org/10.1128/mbio.00676-24
  5. EMBO J. 2024 May 07.
    A non-canonical role of the inner kinetochore in regulating sister-chromatid cohesion at centromeres.
    Lu Yan, Xueying Yuan, Mingjie Liu, Qinfu Chen, Miao Zhang, Junfen Xu, Ling-Hui Zeng, Long Zhang, Jun Huang, Weiguo Lu, Xiaojing He, Haiyan Yan, Fangwei Wang.
      The 16-subunit Constitutive Centromere-associated Network (CCAN)-based inner kinetochore is well-known for connecting centromeric chromatin to the spindle-binding outer kinetochore. Here, we report a non-canonical role for the inner kinetochore in directly regulating sister-chromatid cohesion at centromeres. We provide biochemical, X-ray crystal structure, and intracellular ectopic localization evidence that the inner kinetochore directly binds cohesin, a ring-shaped multi-subunit complex that holds sister chromatids together from S-phase until anaphase onset. This interaction is mediated by binding of the 5-subunit CENP-OPQUR sub-complex of CCAN to the Scc1-SA2 sub-complex of cohesin. Mutation in the CENP-U subunit of the CENP-OPQUR complex that abolishes its binding to the composite interface between Scc1 and SA2 weakens centromeric cohesion, leading to premature separation of sister chromatids during delayed metaphase. We further show that CENP-U competes with the cohesin release factor Wapl for binding the interface of Scc1-SA2, and that the cohesion-protecting role for CENP-U can be bypassed by depleting Wapl. Taken together, this study reveals an inner kinetochore-bound pool of cohesin, which strengthens centromeric sister-chromatid cohesion to resist metaphase spindle pulling forces.
    Keywords:  Centromere; Cohesin; Kinetochore; Mitosis; Sister-Chromatid Cohesion
    DOI:  https://doi.org/10.1038/s44318-024-00104-6
  6. J Cell Biol. 2024 Aug 05. pii: e202403020. [Epub ahead of print]223(8):
    Binucleated human hepatocytes arise through late cytokinetic regression during endomitosis M phase.
    Gabriella S Darmasaputra, Cindy C Geerlings, Susana M Chuva de Sousa Lopes, Hans Clevers, Matilde Galli.
      Binucleated polyploid cells are common in many animal tissues, where they arise by endomitosis, a non-canonical cell cycle in which cells enter M phase but do not undergo cytokinesis. Different steps of cytokinesis have been shown to be inhibited during endomitosis M phase in rodents, but it is currently unknown how human cells undergo endomitosis. In this study, we use fetal-derived human hepatocyte organoids (Hep-Orgs) to investigate how human hepatocytes initiate and execute endomitosis. We find that cells in endomitosis M phase have normal mitotic timings, but lose membrane anchorage to the midbody during cytokinesis, which is associated with the loss of four cortical anchoring proteins, RacGAP1, Anillin, SEPT9, and citron kinase (CIT-K). Moreover, reduction of WNT activity increases the percentage of binucleated cells in Hep-Orgs, an effect that is dependent on the atypical E2F proteins, E2F7 and E2F8. Together, we have elucidated how hepatocytes undergo endomitosis in human Hep-Orgs, providing new insights into the mechanisms of endomitosis in mammals.
    DOI:  https://doi.org/10.1083/jcb.202403020
  7. Genetics. 2024 May 07. pii: iyae069. [Epub ahead of print]
    Translational control of MPS1 links protein synthesis with the initiation of cell division and spindle pole body duplication in Saccharomyces cerevisiae.
    Heidi M Blank, Annabel Alonso, Amy S Fabritius, Ervin Valk, Mart Loog, Mark Winey, Michael Polymenis.
      Protein synthesis underpins cell growth and controls when cells commit to a new round of cell division at a point in late G1 of the cell cycle called Start. Passage through Start also coincides with the duplication of the microtubule-organizing centers, the yeast spindle pole bodies, which will form the two poles of the mitotic spindle that segregates the chromosomes in mitosis. The conserved Mps1p kinase governs the duplication of the spindle pole body in Saccharomyces cerevisiae. Here, we show that the MPS1 transcript has a short upstream open reading frame that represses the synthesis of Mps1p. Mutating the MPS1 uORF makes the cells smaller, accelerates the appearance of Mps1p in late G1, and promotes completion of Start. Monitoring the spindle pole body in the cell cycle using structured illumination microscopy revealed that mutating the MPS1 uORF enabled cells to duplicate their spindle pole body earlier at a smaller cell size. The accelerated Start of MPS1 uORF mutants depends on the G1 cyclin Cln3p and the transcriptional repressor Whi5p but not on the Cln1,2p G1 cyclins. These results identify growth inputs in mechanisms that control duplication of the microtubule-organizing center and implicate these processes in the coupling of cell growth with division.
    Keywords:  MTOC; SIM; SPB; Start; cell size
    DOI:  https://doi.org/10.1093/genetics/iyae069
  8. J Cell Biol. 2024 Aug 05. pii: e202305008. [Epub ahead of print]223(8):
    Cell growth and nutrient availability control the mitotic exit signaling network in budding yeast.
    Rafael A Talavera, Beth E Prichard, Robert A Sommer, Ricardo M Leitao, Christopher J Sarabia, Semin Hazir, Joao A Paulo, Steven P Gygi, Douglas R Kellogg.
      Cell growth is required for cell cycle progression. The amount of growth required for cell cycle progression is reduced in poor nutrients, which leads to a reduction in cell size. In budding yeast, nutrients can influence cell size by modulating the extent of bud growth, which occurs predominantly in mitosis. However, the mechanisms are unknown. Here, we used mass spectrometry to identify proteins that modulate bud growth in response to nutrient availability. This led to the discovery that nutrients regulate numerous components of the mitotic exit network (MEN), which controls exit from mitosis. A key component of the MEN undergoes gradual multisite phosphorylation during bud growth that is dependent upon bud growth and correlated with the extent of growth. Furthermore, activation of the MEN is sufficient to override a growth requirement for mitotic exit. The data suggest a model in which the MEN ensures that mitotic exit occurs only when an appropriate amount of bud growth has occurred.
    DOI:  https://doi.org/10.1083/jcb.202305008
  9. J Mol Cell Biol. 2024 May 06. pii: mjae016. [Epub ahead of print]
    Chromothripsis: an emerging crossroad from aberrant mitosis to therapeutic opportunities.
    Umer Ejaz, Zhen Dou, Phil Y Yao, Zhikai Wang, Xing Liu, Xuebiao Yao.
      Chromothripsis, a type of complex chromosomal rearrangement originally known as chromoanagenesis, has been a subject of extensive investigation due to its potential role in various diseases, particularly cancer. Chromothripsis involves the rapid acquisition of tens to hundreds of structural rearrangements within a short period, leading to complex alterations in one or a few chromosomes. This phenomenon is triggered by chromosome missegregation during mitosis. Errors in accurate chromosome segregation lead to formation of aberrant structural entities such as micronuclei or chromatin bridges. The association between chromothripsis and cancer has attracted significant interest, with potential implications for tumorigenesis and disease prognosis. This review aims to explore the intricate mechanisms and consequences of chromothripsis, with a specific focus on its association with mitotic perturbations. Herein, we discuss a comprehensive analysis of crucial molecular entities and pathways, exploring the intricate roles of the CIP2A-TOPBP1 complex, micronuclei formation, chromatin bridge processing, DNA damage repair, and mitotic checkpoints. Moreover, the review will highlight recent advancements in identifying potential therapeutic targets and the underlying molecular mechanisms associated with chromothripsis, paving the way for future therapeutic interventions in various diseases.
    Keywords:  DNA damage repair; cell division; chromothripsis; genomic stability; synthetic lethality
    DOI:  https://doi.org/10.1093/jmcb/mjae016
  10. Int J Cell Biol. 2024 ;2024 6798897
    Mitotic Kinases Aurora-A, Plk1, and Cdk1 Interact with Elk-1 Transcription Factor through the N-Terminal Domain.
    Oya Arı Uyar, Yigit Koray Babal, Bayram Yılmaz, Isil Aksan Kurnaz.
      Elk-1 is a member of the ETS domain transcription factor superfamily that is phosphorylated upon mitogen-activated protein kinase (MAPK) pathway activation, which in turn regulated its interaction with partner protein serum response factor (SRF), leading to formation of a ternary complex with DNA. It has previously been reported that Elk-1 interacts with a mitotic kinase Aurora-A, although the mechanisms or the relevance of this interaction was unclear. Elk-1 was also reported to be phosphorylated by CDK5 on Thr417 residue. In this study, we show for the first time that this transcription factor interacts not only with Aurora-A but also with other mitotic kinases Aurora-B, Plk1, and Cdk1, and we define the interaction domain on Elk-1 to the first N-terminal 205 amino acids. We also describe putative phosphorylation sites of these mitotic kinases on Elk-1 and show that Elk-1 peptides containing these residues get phosphorylated by the mitotic kinases in in vitro kinase assays. We also perform bioinformatic analysis of mitotic phosphoproteomes and determine potential interaction partners for Elk-1 in Plk or Aurora phosphoproteomes. We propose that understanding the dynamic phosphorylation of Elk-1 by mitotic kinases is important and that it can present a novel target for anticancer strategies.
    DOI:  https://doi.org/10.1155/2024/6798897
  11. Circulation. 2024 May 06.
    Adducin Regulates Sarcomere Disassembly During Cardiomyocyte Mitosis.
    Feng Xiao, Ngoc Uyen Nhi Nguyen, Ping Wang, Shujuan Li, Ching-Cheng Hsu, Suwannee Thet, Wataru Kimura, Xiang Luo, Nicholas T Lam, Ivan Menendez-Montes, Waleed Elhelaly, Alisson Campos Cardoso, Ana Helena Macedo Pereira, Rohit Singh, Sakthivel Sadayappan, Mohammed Kanchwala, Chao Xing, Feria A Ladha, J Travis Hinson, Roger J Hajjar, Joseph A Hill, Hesham A Sadek.
       BACKGROUND: Recent interest in understanding cardiomyocyte cell cycle has been driven by potential therapeutic applications in cardiomyopathy. However, despite recent advances, cardiomyocyte mitosis remains a poorly understood process. For example, it is unclear how sarcomeres are disassembled during mitosis to allow the abscission of daughter cardiomyocytes.
    METHODS: Here, we use a proteomics screen to identify adducin, an actin capping protein previously not studied in cardiomyocytes, as a regulator of sarcomere disassembly. We generated many adeno-associated viruses and cardiomyocyte-specific genetic gain-of-function models to examine the role of adducin in neonatal and adult cardiomyocytes in vitro and in vivo.
    RESULTS: We identify adducin as a regulator of sarcomere disassembly during mammalian cardiomyocyte mitosis. α/γ-adducins are selectively expressed in neonatal mitotic cardiomyocytes, and their levels decline precipitously thereafter. Cardiomyocyte-specific overexpression of various splice isoforms and phospho-isoforms of α-adducin in identified Thr445/Thr480 phosphorylation of a short isoform of α-adducin as a potent inducer of neonatal cardiomyocyte sarcomere disassembly. Concomitant overexpression of this α-adducin variant along with γ-adducin resulted in stabilization of the adducin complex and persistent sarcomere disassembly in adult mice, which is mediated by interaction with α-actinin.
    CONCLUSIONS: These results highlight an important mechanism for coordinating cytoskeletal morphological changes during cardiomyocyte mitosis.
    Keywords:  Irak4; adducin; cardiac proliferation; sarcomere disassembly; α-actinin
    DOI:  https://doi.org/10.1161/CIRCULATIONAHA.122.059102
  12. Aging (Albany NY). 2024 May 06. 16
    AURKB promotes colorectal cancer progression by triggering the phosphorylation of histone H3 at serine 10 to activate CCNE1 expression.
    Ling Li, Ke Xie, Honghu Xie, Lei Wang, Zhong Li, Qicheng Lu, Jin Feng.
      Aurora kinase B (AURKB) initiates the phosphorylation of serine 10 on histone H3 (pH3S10), a crucial process for chromosome condensation and cytokinesis in mammalian mitosis. Nonetheless, the precise mechanisms through which AURKB regulates the cell cycle and contributes to tumorigenesis as an oncogenic factor in colorectal cancer (CRC) remain unclear. Here, we report that AURKB was highly expressed and positively correlated with Ki-67 expression in CRC. The abundant expression of AURKB promotes the growth of CRC cells and xenograft tumors in animal model. AURKB knockdown substantially suppressed CRC proliferation and triggered cell cycle arrest in G2/M phase. Interestingly, cyclin E1 (CCNE1) was discovered as a direct downstream target of AURKB and functioned synergistically with AURKB to promote CRC cell proliferation. Mechanically, AURKB activated CCNE1 expression by triggering pH3S10 in the promoter region of CCNE1. Furthermore, it was showed that the inhibitor specific for AURKB (AZD1152) can suppress CCNE1 expression in CRC cells and inhibit tumor cell growth. To conclude, this research demonstrates that AURKB accelerated the tumorigenesis of CRC through its potential to epigenetically activate CCNE1 expression, suggesting AURKB as a promising therapeutic target in CRC.
    Keywords:  AURKB; CCNE1; cell cycle; colorectal cancer; polyploidy
    DOI:  https://doi.org/10.18632/aging.205801
  13. Reproduction. 2024 May 01. pii: REP-23-0510. [Epub ahead of print]
    Metabolic contribution to age-related chromosome missegregation in mammalian oocytes.
    Bettina P Mihalas, Adele L Marston, Lindsay E Wu, Robert B Gilchrist.
      Advanced maternal age is a major cause of infertility, miscarriage, and congenital abnormalities. This is principally caused by a decrease in oocyte quality and developmental competence with age. Oocyte ageing is characterised by an increase in chromosome missegregation and aneuploidy. However, the underlying mechanisms of age-related aneuploidy have not been fully elucidated and are still under active investigation. In addition to chromosome missegregation, oocyte ageing is also accompanied by metabolic dysfunction. In this review, we integrate old and new perspectives on oocyte ageing, chromosome segregation and metabolism in mammalian oocytes and make direct links between these processes. We consider age-related alterations to chromosome segregation machinery, including the loss of cohesion, microtubule stability and the integrity of the spindle assembly checkpoint. We focus on how metabolic dysfunction in the ageing oocyte disrupts chromosome segregation machinery to contribute to and exacerbate age-related aneuploidy. More specifically, we discuss how mitochondrial function, ATP production and the generation of free radicals are altered during ageing. We also explore recent developments in oocyte metabolic ageing, including altered redox reactions (NAD+ metabolism) and the interactions between oocytes and their somatic nurse cells. Throughout the review we integrate the mechanisms by which changes in oocyte metabolism influence age-related chromosome missegregation.
    DOI:  https://doi.org/10.1530/REP-23-0510
  14. Methods Cell Biol. 2024 ;pii: S0091-679X(24)00056-6. [Epub ahead of print]187 73-97
    Correlative light and electron microscopy at defined cell cycle stages in a controlled environment.
    Helena Bragulat-Teixidor, Shotaro Otsuka.
      Cells are dynamic machines that continuously change their architecture to adapt and respond to extracellular and intracellular stimuli. Deciphering dynamic processes with nanometer-scale resolution inside cells is critical for mechanistic understanding. Here, we present a protocol that enables the in situ study of dynamic changes in intracellular structures under close-to-native conditions at high spatiotemporal resolution. Importantly, the cells are grown, transported, and imaged in a chamber in which environmental conditions such as temperature and gas (e.g., carbon dioxide or oxygen) concentration can be controlled. We demonstrate this protocol to quantify ultrastructural changes that occur during the cell cycle of cultured mammalian cells. The environment control system opens up the possibility of applying this method to primary cells, tissues, and organoids by adjusting environmental conditions.
    Keywords:  Cell cycle; Electron tomography; Endoplasmic reticulum; High-pressure freezing; Live cell imaging; Mitosis; Nuclear envelope
    DOI:  https://doi.org/10.1016/bs.mcb.2024.02.025
  15. Chromosome Res. 2024 May 08. 32(2): 8
    The holocentricity in the dioecious nutmeg (Myristica fragrans) is not based on major satellite repeats.
    Yi-Tzu Kuo, Jacob Gigi Kurian, Veit Schubert, Jörg Fuchs, Michael Melzer, Ananthu Muraleedharan, Ravi Maruthachalam, Andreas Houben.
      Holocentric species are characterized by the presence of centromeres throughout the length of the chromosomes. We confirmed the holocentricity of the dioecious, small chromosome-size species Myristica fragrans based on the chromosome-wide distribution of the centromere-specific protein KNL1, α-tubulin fibers, and the cell cycle-dependent histone H3 serine 28 phosphorylation (H3S28ph) mark. Each holocentromere is likely composed of, on average, ten centromere units, but none of the identified and in situ hybridized high-copy satellite repeats is centromere-specific. No sex-specific major repeats are present in the high-copy repeat composition of male or female plants, or a significant difference in genome size was detected. Therefore, it is unlikely that M. fragrans possesses heteromorphic sex chromosomes.
    Keywords:   Myristica fragrans ; Centromere type; Dioecious; Holocentric chromosome; Holokinetic
    DOI:  https://doi.org/10.1007/s10577-024-09751-1
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