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Kincade JN, Hlavacek A, Akera T, Balboula AZ. Initial spindle positioning at the oocyte center protects against incorrect kinetochore-microtubule attachment and aneuploidy in mice. SCIENCE ADVANCES 2023; 9:eadd7397. [PMID: 36800430 PMCID: PMC9937575 DOI: 10.1126/sciadv.add7397] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/30/2022] [Accepted: 01/19/2023] [Indexed: 06/18/2023]
Abstract
Spindle positioning within the oocyte must be tightly regulated. In mice, the spindle is predominantly assembled at the oocyte center before its migration toward the cortex to achieve the highly asymmetric division, a characteristic of female meiosis. The significance of the initial central positioning of the spindle is largely unknown. We show that initial spindle positioning at the oocyte center is an insurance mechanism to avoid the premature exposure of the spindle to cortical CDC42 signaling, which perturbs proper kinetochore-microtubule attachments, leading to the formation of aneuploid gametes. These findings contribute to understanding why female gametes are notoriously associated with high rates of aneuploidy, the leading genetic cause of miscarriage and congenital abnormalities.
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Affiliation(s)
- Jessica N. Kincade
- Animal Sciences Research Center, University of Missouri, Columbia, MO 65211, USA
| | - Avery Hlavacek
- Animal Sciences Research Center, University of Missouri, Columbia, MO 65211, USA
| | - Takashi Akera
- Cell and Developmental Biology Center, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD 20892, USA
| | - Ahmed Z. Balboula
- Animal Sciences Research Center, University of Missouri, Columbia, MO 65211, USA
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2
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Daeden A, Mietke A, Derivery E, Seum C, Jülicher F, Gonzalez-Gaitan M. Polarized branched Actin modulates cortical mechanics to produce unequal-size daughters during asymmetric division. Nat Cell Biol 2023; 25:235-245. [PMID: 36747081 PMCID: PMC9928585 DOI: 10.1038/s41556-022-01058-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2021] [Accepted: 11/22/2022] [Indexed: 02/08/2023]
Abstract
The control of cell shape during cytokinesis requires a precise regulation of mechanical properties of the cell cortex. Only few studies have addressed the mechanisms underlying the robust production of unequal-sized daughters during asymmetric cell division. Here we report that unequal daughter-cell sizes resulting from asymmetric sensory organ precursor divisions in Drosophila are controlled by the relative amount of cortical branched Actin between the two cell poles. We demonstrate this by mistargeting the machinery for branched Actin dynamics using nanobodies and optogenetics. We can thereby engineer the cell shape with temporal precision and thus the daughter-cell size at different stages of cytokinesis. Most strikingly, inverting cortical Actin asymmetry causes an inversion of daughter-cell sizes. Our findings uncover the physical mechanism by which the sensory organ precursor mother cell controls relative daughter-cell size: polarized cortical Actin modulates the cortical bending rigidity to set the cell surface curvature, stabilize the division and ultimately lead to unequal daughter-cell size.
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Affiliation(s)
- Alicia Daeden
- Department of Biochemistry, Faculty of Sciences, University of Geneva, Geneva, Switzerland
| | - Alexander Mietke
- Department of Mathematics, Massachusetts Institute of Technology, Cambridge, MA, USA
- Max Planck Institute for the Physics of Complex Systems, Dresden, Germany
- Max Planck Institute of Molecular Cell Biology and Genetics, Dresden, Germany
- Center for Systems Biology Dresden, Dresden, Germany
| | - Emmanuel Derivery
- Department of Biochemistry, Faculty of Sciences, University of Geneva, Geneva, Switzerland
- MRC Laboratory of Molecular Biology, Cambridge, UK
| | - Carole Seum
- Department of Biochemistry, Faculty of Sciences, University of Geneva, Geneva, Switzerland
| | - Frank Jülicher
- Max Planck Institute for the Physics of Complex Systems, Dresden, Germany
| | - Marcos Gonzalez-Gaitan
- Department of Biochemistry, Faculty of Sciences, University of Geneva, Geneva, Switzerland.
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3
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Tao R, Bi J, Zhu F, Wang X, Jia C, Xu H, He X, Li J. Division Behaviors and Their Effects on Preimplantation Development of Pig Embryos. Reprod Domest Anim 2022; 57:1016-1028. [PMID: 35662274 DOI: 10.1111/rda.14168] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2022] [Revised: 05/10/2022] [Accepted: 05/28/2022] [Indexed: 11/27/2022]
Abstract
Quality of preimplantation embryos could affect development efficiency after embryo transfer. However, assessment of preimplantation embryos was unsatisfied especially in pig embryos to date. Therefore, the present study was design to investigate available and applicable parameters which indicating development potential and quality of porcine preimplantation embryos produced by handmade cloning (HMC), parthenogenetic activation without zona pellucida (PAZF) and with zona pellucida (PAZI). Results firstly detected a common division behavior that formation of uneven division with two unequal size blastomeres (UD 2-cell), especially in HMC embryos, the proportion of UD 2-cell was significantly higher than that of equal size blastomeres (ED 2-cell) with 72.56 ± 4.56 vs. 24.57 ± 1.92. Formation of UD 2-cell might due to spindle migrates along the long axis in 1-cell stage, and the cleavage furrow not formed in the center of cytoplasm. In the two sister blastomeres of UD 2-cell, unevenly distribution of organelles (mitochondria and lipid droplet) was observed with lower proportion in the smaller one (p<0.05). Althoug no difference of blastocyst rate was observed between UD and ED 2-cell embryos, the cell number per blastocyst from UD 2-cell embryos was lower than that from ED 2-cell embryos (44.15 ± 2.05 vs. 51.55 ± 1.83). Besides, because of nonsynchronized division of each blastomeres, another common behavior that three cleavage routes were observed in all of HMC/PAZF/PAZI embryos that T1 (2-cell → 3-cell → 4-cell → ≥ 5-cell → morula → blastocyst), T2 (2-cell → 3-cell → 4-cell → morula → blastocyst), and T3 (2-cell → 3-cell / 4-cell → morula → blastocyst). Therefore, in pig in vitro produced embryos, division behaviors of uneven volume of cytoplasm and nonsynchronized cell cycles were observed at the early embryonic developmental stage, which might be another potential factor to evaluate embryonic development.
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Affiliation(s)
- Ruixin Tao
- College of Animal Science and Technology, Nanjing Agricultural University, Nanjing, China
| | - Jiaying Bi
- College of Animal Science and Technology, Nanjing Agricultural University, Nanjing, China
| | - Fuquan Zhu
- College of Animal Science and Technology, Nanjing Agricultural University, Nanjing, China
| | - Xuguang Wang
- College of Animal Science and Technology, Xinjiang Agricultural University, Urimuqi, China
| | - Chao Jia
- College of Animal Science and Technology, Nanjing Agricultural University, Nanjing, China
| | - Hongxia Xu
- College of Animal Science and Technology, Nanjing Agricultural University, Nanjing, China
| | - Xu He
- College of Animal Science and Technology, Nanjing Agricultural University, Nanjing, China
| | - Juan Li
- College of Animal Science and Technology, Nanjing Agricultural University, Nanjing, China
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4
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Londoño-Vásquez D, Rodriguez-Lukey K, Behura SK, Balboula AZ. Microtubule organizing centers regulate spindle positioning in mouse oocytes. Dev Cell 2022; 57:197-211.e3. [PMID: 35030327 PMCID: PMC8792338 DOI: 10.1016/j.devcel.2021.12.011] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2021] [Revised: 10/18/2021] [Accepted: 12/10/2021] [Indexed: 01/26/2023]
Abstract
During female meiosis I (MI), spindle positioning must be tightly regulated to ensure the fidelity of the first asymmetric division and faithful chromosome segregation. Although the role of F-actin in regulating these critical processes has been studied extensively, little is known about whether microtubules (MTs) participate in regulating these processes. Using mouse oocytes as a model system, we characterize a subset of MT organizing centers that do not contribute directly to spindle assembly, termed mcMTOCs. Using laser ablation, STED super-resolution microscopy, and chemical manipulation, we show that mcMTOCs are required to regulate spindle positioning and faithful chromosome segregation during MI. We discuss how forces exerted by F-actin on the spindle are balanced by mcMTOC-nucleated MTs to anchor the spindle centrally and to regulate its timely migration. Our findings provide a model for asymmetric cell division, complementing the current F-actin-based models, and implicate mcMTOCs as a major player in regulating spindle positioning.
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Affiliation(s)
| | | | - Susanta K Behura
- Animal Sciences Research Center, University of Missouri, Columbia, MO 65211, USA
| | - Ahmed Z Balboula
- Animal Sciences Research Center, University of Missouri, Columbia, MO 65211, USA; University of Cambridge, Department of Genetics, Downing Street, Cambridge, CB2 3EH, UK.
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5
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Zou YJ, Shan MM, Wang HH, Pan ZN, Pan MH, Xu Y, Ju JQ, Sun SC. RAB14 GTPase is essential for actin-based asymmetric division during mouse oocyte maturation. Cell Prolif 2021; 54:e13104. [PMID: 34323331 PMCID: PMC8450121 DOI: 10.1111/cpr.13104] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2021] [Revised: 06/25/2021] [Accepted: 07/15/2021] [Indexed: 12/19/2022] Open
Abstract
Objectives RAB14 is a member of small GTPase RAB family which localizes at the endoplasmic reticulum (ER), Golgi apparatus and endosomal compartments. RAB14 acts as molecular switches that shift between a GDP‐bound inactive state and a GTP‐bound active state and regulates circulation of vesicles between the Golgi and endosomal compartments. In present study, we investigated the roles of RAB14 during oocyte meiotic maturation. Materials and methods Microinjection with siRNA and exogenous mRNA for knock down and rescue, and immunofluorescence staining, Western blot and real‐time RT‐PCR were utilized for the study. Results Our results showed that RAB14 localized in the cytoplasm and accumulated at the cortex during mouse oocyte maturation, and it was also enriched at the spindle periphery. Depletion of RAB14 did not affect polar body extrusion but caused large polar bodies, indicating the failure of asymmetric division. We found that absence of RAB14 did not affect spindle organization but caused the spindle migration defects, and this might be due to the regulation on cytoplasmic actin assembly via the ROCK‐cofilin signalling pathway. We also found that RAB14 depletion led to aberrant Golgi apparatus distribution. Exogenous Myc‐Rab14 mRNA supplement could significantly rescue these defects caused by Rab14 siRNA injection. Conclusions Taken together, our results suggest that RAB14 affects ROCK‐cofilin pathway for actin‐based spindle migration and Golgi apparatus distribution during mouse oocyte meiotic maturation.
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Affiliation(s)
- Yuan-Jing Zou
- College of Animal Science and Technology, Nanjing Agricultural University, Nanjing, China
| | - Meng-Meng Shan
- College of Animal Science and Technology, Nanjing Agricultural University, Nanjing, China
| | - Hong-Hui Wang
- College of Animal Science and Technology, Nanjing Agricultural University, Nanjing, China.,WEGO Holding Company Limited, Weihai, China
| | - Zhen-Nan Pan
- College of Animal Science and Technology, Nanjing Agricultural University, Nanjing, China
| | - Meng-Hao Pan
- College of Animal Science and Technology, Nanjing Agricultural University, Nanjing, China
| | - Yi Xu
- College of Animal Science and Technology, Nanjing Agricultural University, Nanjing, China
| | - Jia-Qian Ju
- College of Animal Science and Technology, Nanjing Agricultural University, Nanjing, China
| | - Shao-Chen Sun
- College of Animal Science and Technology, Nanjing Agricultural University, Nanjing, China
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6
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Magliozzi JO, Moseley JB. Connecting cell polarity signals to the cytokinetic machinery in yeast and metazoan cells. Cell Cycle 2021; 20:1-10. [PMID: 33397181 DOI: 10.1080/15384101.2020.1864941] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
Abstract
Polarized growth and cytokinesis are two fundamental cellular processes that exist in virtually all cell types. Mechanisms for asymmetric distribution of materials allow for cells to grow in a polarized manner. This gives rise to a variety of cell shapes seen throughout all cell types. Following polarized growth during interphase, dividing cells assemble a cytokinetic ring containing the protein machinery to constrict and separate daughter cells. Here, we discuss how cell polarity signaling pathways act on cytokinesis, with a focus on direct regulation of the contractile actomyosin ring (CAR). Recent studies have exploited phosphoproteomics to identify new connections between cell polarity kinases and CAR proteins. Existing evidence suggests that some polarity kinases guide the local organization of CAR proteins and structures while also contributing to global organization of the division plane within a cell. We provide several examples of this regulation from budding yeast, fission yeast, and metazoan cells. In some cases, kinase-substrate connections point to conserved processes in these different organisms. We point to several examples where future work can indicate the degree of conservation and divergence in the cell division process of these different organisms.
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Affiliation(s)
- Joseph O Magliozzi
- Department of Biochemistry and Cell Biology, The Geisel School of Medicine at Dartmouth , Hanover, New Hampshire, USA
| | - James B Moseley
- Department of Biochemistry and Cell Biology, The Geisel School of Medicine at Dartmouth , Hanover, New Hampshire, USA
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7
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Augustine B, Chin CF, Yeong FM. Role of Kip2 during early mitosis - impact on spindle pole body separation and chromosome capture. J Cell Sci 2018; 131:jcs.211425. [PMID: 29739877 DOI: 10.1242/jcs.211425] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2017] [Accepted: 04/30/2018] [Indexed: 11/20/2022] Open
Abstract
Mitotic spindle dynamics are regulated during the cell cycle by microtubule motor proteins. In Saccharomyces cerevisiae, one such protein is Kip2p, a plus-end motor that regulates the polymerization and stability of cytoplasmic microtubules (cMTs). Kip2p levels are regulated during the cell cycle, and its overexpression leads to the formation of hyper-elongated cMTs. To investigate the significance of varying Kip2p levels during the cell cycle and the hyper-elongated cMTs, we overexpressed KIP2 in the G1 phase and examined the effects on the separation of spindle pole bodies (SPBs) and chromosome segregation. Our results show that failure to regulate the cMT lengths during G1-S phase prevents the separation of SPBs. This, in turn, affects chromosome capture and leads to the activation of spindle assembly checkpoint (SAC) and causes mitotic arrest. These defects could be rescued by either the inactivation of checkpoint components or by co-overexpression of CIN8, which encodes a motor protein that elongates inter-polar microtubules (ipMTs). Hence, we propose that the maintenance of Kip2p level and cMT lengths during early cell division is important to ensure coordination between SPB separation and chromosome capture by kinetochore microtubules (kMTs).
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Affiliation(s)
- Beryl Augustine
- Department of Biochemistry, Yong Loo Lin School of Medicine, National University of Singapore, MD4, 5 Science Drive 2, Singapore 117545
| | - Cheen Fei Chin
- Department of Biochemistry, Yong Loo Lin School of Medicine, National University of Singapore, MD4, 5 Science Drive 2, Singapore 117545
| | - Foong May Yeong
- Department of Biochemistry, Yong Loo Lin School of Medicine, National University of Singapore, MD4, 5 Science Drive 2, Singapore 117545
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8
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Kumar M, Pushpa K, Mylavarapu SVS. Splitting the cell, building the organism: Mechanisms of cell division in metazoan embryos. IUBMB Life 2015; 67:575-87. [PMID: 26173082 PMCID: PMC5937677 DOI: 10.1002/iub.1404] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2015] [Accepted: 06/18/2015] [Indexed: 11/12/2022]
Abstract
The unicellular metazoan zygote undergoes a series of cell divisions that are central to its development into an embryo. Differentiation of embryonic cells leads eventually to the development of a functional adult. Fate specification of pluripotent embryonic cells occurs during the early embryonic cleavage divisions in several animals. Early development is characterized by well-known stages of embryogenesis documented across animals--morulation, blastulation, and morphogenetic processes such as gastrulation, all of which contribute to differentiation and tissue specification. Despite this broad conservation, there exist clearly discernible morphological and functional differences across early embryonic stages in metazoans. Variations in the mitotic mechanisms of early embryonic cell divisions play key roles in governing these gross differences that eventually encode developmental patterns. In this review, we discuss molecular mechanisms of both karyokinesis (nuclear division) and cytokinesis (cytoplasmic separation) during early embryonic divisions. We outline the broadly conserved molecular pathways that operate in these two stages in early embryonic mitoses. In addition, we highlight mechanistic variations in these two stages across different organisms. We finally discuss outstanding questions of interest, answers to which would illuminate the role of divergent mitotic mechanisms in shaping early animal embryogenesis.
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Affiliation(s)
- Megha Kumar
- Laboratory of Cellular Dynamics, Regional Centre for Biotechnology, NCR Biotech Science Cluster, Faridabad, Haryana, India
| | - Kumari Pushpa
- Laboratory of Cellular Dynamics, Regional Centre for Biotechnology, NCR Biotech Science Cluster, Faridabad, Haryana, India
| | - Sivaram V. S. Mylavarapu
- Laboratory of Cellular Dynamics, Regional Centre for Biotechnology, NCR Biotech Science Cluster, Faridabad, Haryana, India
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9
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Ucar H, Tachibana K, Kishimoto T. The Mos-MAPK pathway regulates Diaphanous-related formin activity to drive cleavage furrow closure during polar body extrusion in starfish oocytes. J Cell Sci 2013; 126:5153-65. [PMID: 24046444 DOI: 10.1242/jcs.130476] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
Maintenance of spindle attachment to the cortex and formation of the cleavage furrow around the protruded spindle are essential for polar body extrusion (PBE) during meiotic maturation of oocytes. Although spindle movement to the cortex has been well-studied, how the spindle is maintained at the cortex during PBE is unknown. Here, we show that activation of Diaphanous-related formin mediated by mitogen-activated protein kinase (MAPK) is required for tight spindle attachment to the cortex and cleavage furrow closure during PBE in starfish (Asterina pectinifera) oocytes. A. pectinifera Diaphanous-related formin (ApDia) had a distinct localization in immature oocytes and was localized to the cleavage furrow during PBE. Inhibition of the Mos-MAPK pathway or the actin nucleating activity of formin homology 2 domain prevented cleavage furrow closure and resulted in PBE failure. In MEK/MAPK-inhibited oocytes, activation of ApDia by relief of its intramolecular inhibition restored PBE. In summary, this study elucidates a link between the Mos-MAPK pathway and Diaphanous-related formins, that is responsible for maintaining tight spindle attachment to the cortex and cleavage furrow closure during PBE.
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Affiliation(s)
- Hasan Ucar
- Laboratory of Cell and Developmental Biology, Graduate School of Bioscience, Tokyo Institute of Technology, Yokohama 226-8501, Japan
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Zheng Z, Wan Q, Liu J, Zhu H, Chu X, Du Q. Evidence for dynein and astral microtubule-mediated cortical release and transport of Gαi/LGN/NuMA complex in mitotic cells. Mol Biol Cell 2013; 24:901-13. [PMID: 23389635 PMCID: PMC3608500 DOI: 10.1091/mbc.e12-06-0458] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Spindle positioning is believed to be governed by the interaction between astral microtubules and the cell cortex and involve cortically anchored motor protein dynein. How dynein is recruited to and regulated at the cell cortex to generate forces on astral microtubules is not clear. Here we show that mammalian homologue of Drosophila Pins (Partner of Inscuteable) (LGN), a Gαi-binding protein that is critical for spindle positioning in different systems, associates with cytoplasmic dynein heavy chain (DYNC1H1) in a Gαi-regulated manner. LGN is required for the mitotic cortical localization of DYNC1H1, which, in turn, also modulates the cortical accumulation of LGN. Using fluorescence recovery after photobleaching analysis, we show that cortical LGN is dynamic and the turnover of LGN relies, at least partially, on astral microtubules and DYNC1H1. We provide evidence for dynein- and astral microtubule-mediated transport of Gαi/LGN/nuclear mitotic apparatus (NuMA) complex from cell cortex to spindle poles and show that actin filaments counteract such transport by maintaining Gαi/LGN/NuMA and dynein at the cell cortex. Our results indicate that astral microtubules are required for establishing bipolar, symmetrical cortical LGN distribution during metaphase. We propose that regulated cortical release and transport of LGN complex along astral microtubules may contribute to spindle positioning in mammalian cells.
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Affiliation(s)
- Zhen Zheng
- Department of Neurology, Medical College of Georgia, Georgia Regents University, Augusta, GA, USA
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Abstract
Brown algae are an extremely interesting, but surprisingly poorly explored, group of organisms. They are one of only five eukaryotic lineages to have independently evolved complex multicellularity, which they express through a wide variety of morphologies ranging from uniseriate branched filaments to complex parenchymatous thalli with multiple cell types. Despite their very distinct evolutionary history, brown algae and land plants share a striking amount of developmental features. This has led to an interest in several aspects of brown algal development, including embryogenesis, polarity, cell cycle, asymmetric cell division and a putative role for plant hormone signalling. This review describes how investigations using brown algal models have helped to increase our understanding of the processes controlling early embryo development, in particular polarization, axis formation and asymmetric cell division. Additionally, the diversity of life cycles in the brown lineage and the emergence of Ectocarpus as a powerful model organism, are affording interesting insights on the molecular mechanisms underlying haploid-diploid life cycles. The use of these and other emerging brown algal models will undoubtedly add to our knowledge on the mechanisms that regulate development in multicellular photosynthetic organisms.
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Affiliation(s)
- Kenny A Bogaert
- Phycology Research Group, Department of Biology, Center for Molecular Phylogenetics and Evolution, Ghent University, Ghent, Belgium
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12
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Juranić M, Srilunchang KO, Krohn NG, Leljak-Levanić D, Sprunck S, Dresselhaus T. Germline-specific MATH-BTB substrate adaptor MAB1 regulates spindle length and nuclei identity in maize. THE PLANT CELL 2012; 24:4974-91. [PMID: 23250449 PMCID: PMC3556970 DOI: 10.1105/tpc.112.107169] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/05/2012] [Revised: 11/05/2012] [Accepted: 11/28/2012] [Indexed: 05/03/2023]
Abstract
Germline and early embryo development constitute ideal model systems to study the establishment of polarity, cell identity, and asymmetric cell divisions (ACDs) in plants. We describe here the function of the MATH-BTB domain protein MAB1 that is exclusively expressed in the germ lineages and the zygote of maize (Zea mays). mab1 (RNA interference [RNAi]) mutant plants display chromosome segregation defects and short spindles during meiosis that cause insufficient separation and migration of nuclei. After the meiosis-to-mitosis transition, two attached nuclei of similar identity are formed in mab1 (RNAi) mutants leading to an arrest of further germline development. Transient expression studies of MAB1 in tobacco (Nicotiana tabacum) Bright Yellow-2 cells revealed a cell cycle-dependent nuclear localization pattern but no direct colocalization with the spindle apparatus. MAB1 is able to form homodimers and interacts with the E3 ubiquitin ligase component Cullin 3a (CUL3a) in the cytoplasm, likely as a substrate-specific adapter protein. The microtubule-severing subunit p60 of katanin was identified as a candidate substrate for MAB1, suggesting that MAB1 resembles the animal key ACD regulator Maternal Effect Lethal 26 (MEL-26). In summary, our findings provide further evidence for the importance of posttranslational regulation for asymmetric divisions and germline progression in plants and identified an unstable key protein that seems to be involved in regulating the stability of a spindle apparatus regulator(s).
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Affiliation(s)
- Martina Juranić
- Cell Biology and Plant Biochemistry, Biochemie-Zentrum Regensburg, University of Regensburg, 93053 Regensburg, Germany
- Department of Molecular Biology, Faculty of Science and Mathematics, University of Zagreb, 10000 Zagreb, Croatia
| | | | - Nádia Graciele Krohn
- Faculty of Pharmaceutical Sciences of Ribeirão Preto, University of São Paulo, Ribeirao Preto 14040-903, Brazil
| | - Dunja Leljak-Levanić
- Department of Molecular Biology, Faculty of Science and Mathematics, University of Zagreb, 10000 Zagreb, Croatia
| | - Stefanie Sprunck
- Cell Biology and Plant Biochemistry, Biochemie-Zentrum Regensburg, University of Regensburg, 93053 Regensburg, Germany
| | - Thomas Dresselhaus
- Cell Biology and Plant Biochemistry, Biochemie-Zentrum Regensburg, University of Regensburg, 93053 Regensburg, Germany
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13
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Collins ES, Balchand SK, Faraci JL, Wadsworth P, Lee WL. Cell cycle-regulated cortical dynein/dynactin promotes symmetric cell division by differential pole motion in anaphase. Mol Biol Cell 2012; 23:3380-90. [PMID: 22809624 PMCID: PMC3431930 DOI: 10.1091/mbc.e12-02-0109] [Citation(s) in RCA: 61] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Evidence is presented for dynamic cortical association of dynein and dynactin in mammalian cells and its regulation by Plk1, astral microtubules, and the cell cycle. The asymmetric spindle positioning in LLC-Pk1 cells and its correction by dynein and dynactin provide a new system for analysis of spindle position and symmetric cell division. In cultured mammalian cells, how dynein/dynactin contributes to spindle positioning is poorly understood. To assess the role of cortical dynein/dynactin in this process, we generated mammalian cell lines expressing localization and affinity purification (LAP)–tagged dynein/dynactin subunits from bacterial artificial chromosomes and observed asymmetric cortical localization of dynein and dynactin during mitosis. In cells with asymmetrically positioned spindles, dynein and dynactin were both enriched at the cortex distal to the spindle. NuMA, an upstream targeting factor, localized asymmetrically along the cell cortex in a manner similar to dynein and dynactin. During spindle motion toward the distal cortex, dynein and dynactin were locally diminished and subsequently enriched at the new distal cortex. At anaphase onset, we observed a transient increase in cortical dynein, followed by a reduction in telophase. Spindle motion frequently resulted in cells entering anaphase with an asymmetrically positioned spindle. These cells gave rise to symmetric daughter cells by dynein-dependent differential spindle pole motion in anaphase. Our results demonstrate that cortical dynein and dynactin dynamically associate with the cell cortex in a cell cycle–regulated manner and are required to correct spindle mispositioning in LLC-Pk1 epithelial cells.
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14
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Maly IV. Equilibria of idealized confined astral microtubules and coupled spindle poles. PLoS One 2012; 7:e38921. [PMID: 22719988 PMCID: PMC3375304 DOI: 10.1371/journal.pone.0038921] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2012] [Accepted: 05/15/2012] [Indexed: 12/03/2022] Open
Abstract
Positioning of the mitotic spindle through the interaction of astral microtubules with the cell boundary often determines whether the cell division will be symmetric or asymmetric. This process plays a crucial role in development. In this paper, a numerical model is presented that deals with the force exerted on the spindle by astral microtubules that are bent by virtue of their confinement within the cell boundary. It is found that depending on parameters, the symmetric position of the spindle can be stable or unstable. Asymmetric stable equilibria also exist, and two or more stable positions can exist simultaneously. The theory poses new types of questions for experimental research. Regarding the cases of symmetric spindle positioning, it is necessary to ask whether the microtubule parameters are controlled by the cell so that the bending mechanics favors symmetry. If they are not, then it is necessary to ask what forces external to the microtubule cytoskeleton counteract the bending effects sufficiently to actively establish symmetry. Conversely, regarding the cases with asymmetry, it is now necessary to investigate whether the cell controls the microtubule parameters so that the bending favors asymmetry apart from any forces that are external to the microtubule cytoskeleton.
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Affiliation(s)
- Ivan V Maly
- Department of Computational and Systems Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, United States of America.
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15
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Xiao Z, Wan Q, Du Q, Zheng Z. Galpha/LGN-mediated asymmetric spindle positioning does not lead to unequal cleavage of the mother cell in 3-D cultured MDCK cells. Biochem Biophys Res Commun 2012; 420:888-94. [PMID: 22469469 DOI: 10.1016/j.bbrc.2012.03.095] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2012] [Accepted: 03/19/2012] [Indexed: 01/14/2023]
Abstract
The position of the mitotic spindle plays a key role in spatial control of cell division. It is generally believed that when a spindle is positioned asymmetrically in a dividing cell, the resulting daughter cells are usually unequal in size due to eccentric cleavage of the mother cell. Molecular mechanisms underlying the generation of unequal sized daughter cells have been extensively studied in Drosophila neuroblast and Caenorhabditis elegans zygote where the Gα subunit of the heterotrimeric G proteins and its binding partner - Pins in Drosophila and GPR-1/2 in C. elegans - are shown to be critical in governing spindle positioning and asymmetric cleavage of the mother cell. In mammalian system, although Gα and LGN (mammalian Pins homolog) are also required for spindle orientation, whether they can mediate asymmetric spindle positioning or asymmetric cleavage of the mother cell is not known. Here, by artificially targeting Gαi to the apical cortex in 3-D cultured MDCK cells, we established a system where asymmetric spindle positioning can be consistently induced. Interestingly, this asymmetrically positioned spindle does not lead to asymmetric cleavage; instead it results in equal sized daughter cells. Live cell time-lapse analysis revealed that anaphase spindle elongation compensated the original asymmetric spindle positioning. Our findings demonstrate that asymmetric spindle positioning does not necessarily lead to unequal sized daughter cells in mammalian system. We discuss potential mechanisms in generating unequal sized daughter cells.
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Affiliation(s)
- Zhuoni Xiao
- Institute of Molecular Medicine and Genetics, Department of Neurology, Georgia Health Sciences University, 1120 15th Street, Augusta, GA 30912, USA
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16
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Rasmussen CG, Humphries JA, Smith LG. Determination of symmetric and asymmetric division planes in plant cells. ANNUAL REVIEW OF PLANT BIOLOGY 2011; 62:387-409. [PMID: 21391814 DOI: 10.1146/annurev-arplant-042110-103802] [Citation(s) in RCA: 78] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
The cellular organization of plant tissues is determined by patterns of cell division and growth coupled with cellular differentiation. Cells proliferate mainly via symmetric division, whereas asymmetric divisions are associated with initiation of new developmental patterns and cell types. Division planes in both symmetrically and asymmetrically dividing cells are established through the action of a cortical preprophase band (PPB) of cytoskeletal filaments, which is disassembled upon transition to metaphase, leaving behind a cortical division site (CDS) to which the cytokinetic phragmoplast is later guided to position the cell plate. Recent progress has been made in understanding PPB formation and function as well as the nature and function of the CDS. In asymmetrically dividing cells, division plane establishment is governed by cell polarity. Recent work is beginning to shed light on polarization mechanisms in asymmetrically dividing cells, with receptor-like proteins and potential downstream effectors emerging as important players in this process.
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Affiliation(s)
- Carolyn G Rasmussen
- Section of Cell and Developmental Biology, University of California, San Diego, La Jolla, California 92093, USA.
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17
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Vladar EK, Antic D, Axelrod JD. Planar cell polarity signaling: the developing cell's compass. Cold Spring Harb Perspect Biol 2010; 1:a002964. [PMID: 20066108 DOI: 10.1101/cshperspect.a002964] [Citation(s) in RCA: 178] [Impact Index Per Article: 12.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
Cells of many tissues acquire cellular asymmetry to execute their physiologic functions. The planar cell polarity system, first characterized in Drosophila, is important for many of these events. Studies in Drosophila suggest that an upstream system breaks cellular symmetry by converting tissue gradients to subcellular asymmetry, whereas a downstream system amplifies subcellular asymmetry and communicates polarity between cells. In this review, we discuss apparent similarities and differences in the mechanism that controls PCP as it has been adapted to a broad variety of morphological cellular asymmetries in various organisms.
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Affiliation(s)
- Eszter K Vladar
- Department of Pathology, Stanford University School of Medicine, 300 Pasteur Drive, Stanford, California 94305, USA
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18
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Ortiz J, Funk C, Schäfer A, Lechner J. Stu1 inversely regulates kinetochore capture and spindle stability. Genes Dev 2009; 23:2778-91. [PMID: 19952112 DOI: 10.1101/gad.541309] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
The Saccharomyces cerevisiae CLASP (CLIP-associated protein) Stu1 is essential for the establishment and maintenance of the mitotic spindle. Furthermore, Stu1 localizes to kinetochores. Here we show that, in prometaphase, Stu1 assembles in an Ndc80-dependent manner exclusively at kinetochores that are not attached to microtubules. Stu1 relocates to microtubules when a captured kinetochore reaches a spindle pole. This relocation does not depend on kinetochore biorientation, but requires a functional DASH complex. Stu1 at detached kinetochores facilitates kinetochore capturing. Furthermore, since most of the nuclear Stu1 is sequestered by one or a few detached kinetochores, the presence of detached kinetochores prevents Stu1 from localizing the spindle, and therefore from stabilizing the spindle. Thus, the sequestering of Stu1 by detached kinetochores serves as a checkpoint that keeps spindle poles in close proximity until all kinetochores are captured. This is likely to facilitate kinetochore biorientation. In agreement with the findings described above, a kinetochore mutant (okp1-52) that fails to release Stu1 from the kinetochore displays a severe spindle defect upon spindle pole body separation, and this defect can be rescued by destroying the okp1-52 kinetochore.
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Affiliation(s)
- Jennifer Ortiz
- Biochemie-Zentrum der Universität Heidelberg, 69120 Heidelberg, Germany
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19
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Szymczak P, Janovjak H. Periodic forces trigger a complex mechanical response in ubiquitin. J Mol Biol 2009; 390:443-56. [PMID: 19426737 DOI: 10.1016/j.jmb.2009.04.071] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2009] [Revised: 04/27/2009] [Accepted: 04/28/2009] [Indexed: 01/12/2023]
Abstract
Mechanical forces govern physiological processes in all living organisms. Many cellular forces, for example, those generated in cyclic conformational changes of biological machines, have repetitive components. In apparent contrast, little is known about how dynamic protein structures respond to periodic mechanical information. Ubiquitin is a small protein found in all eukaryotes. We developed molecular dynamics simulations to unfold single and multimeric ubiquitins with periodic forces. By using a coarse-grained representation, we were able to model forces with periods about 2 orders of magnitude longer than the protein's relaxation time. We found that even a moderate periodic force weakened the protein and shifted its unfolding pathways in a frequency- and amplitude-dependent manner. A complex dynamic response with secondary structure refolding and an increasing importance of local interactions was revealed. Importantly, repetitive forces with broadly distributed frequencies elicited very similar molecular responses compared to fixed-frequency forces. When testing the influence of pulling geometry on ubiquitin's mechanical stability, it was found that the linkage involved in the mechanical degradation of cellular proteins renders the protein remarkably insensitive to periodic forces. We also devised a complementary kinetic energy landscape model that traces these observations and explains periodic-force, single-molecule measurements. In turn, this analytical model is capable of predicting dynamic protein responses. These results provide new insights into ubiquitin mechanics and a potential mechanical role during protein degradation, as well as first frameworks for dynamic protein stability and the modeling of repetitive mechanical processes.
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Affiliation(s)
- Piotr Szymczak
- Institute of Theoretical Physics, Warsaw University, Poland
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20
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Zhang X, Liu D, Lv S, Wang H, Zhong X, Liu B, Wang B, Liao J, Li J, Pfeifer GP, Xu X. CDK5RAP2 is required for spindle checkpoint function. Cell Cycle 2009; 8:1206-16. [PMID: 19282672 DOI: 10.4161/cc.8.8.8205] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
The combination of paclitaxel and doxorubicin is among the most successful chemotherapy regimens in cancer treatment. CDK5RAP2, when mutated, causes primary microcephaly. We show here that inhibition of CDK5RAP2 expression causes chromosome mis-segregation, fails to maintain the spindle checkpoint, and is associated with reduced expression of the spindle checkpoint proteins BUBR1 and MAD2 and an increase in chromatin-associated CDC20. CDK5RAP2 resides on the BUBR1 and MAD2 promoters and regulates their transcription. Furthermore, CDK5RAP2-knockdown cells have increased resistance to paclitaxel and doxorubicin, and this resistance is partially rescued upon restoration of CDK5RAP2 expression. Cancer cells cultured in the presence of paclitaxel or doxorubicin exhibit dramatically decreased CDK5RAP2 levels. These results suggest that CDK5RAP2 is required for spindle checkpoint function and is a common target in paclitaxel and doxorubicin resistance.
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Affiliation(s)
- Xiaoying Zhang
- Laboratory of Cancer Biology, Capital Normal University College of Life Science, Beijing, China
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21
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Great expectations for PIP: phosphoinositides as regulators of signaling during development and disease. Dev Cell 2009; 16:12-20. [PMID: 19154715 DOI: 10.1016/j.devcel.2008.12.006] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Phosphoinositides function as signaling precursors as well as regulators and scaffolds of signaling molecules required for important cellular processes such as membrane trafficking. Although a picture of the biochemical and cell biological functions of phosphoinositides is emerging, less is known about how these functions impact signaling on a broader scale during development. This review summarizes recent work on the role of phosphoinositides in developmental signaling and in a number of diseases and developmental disorders.
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22
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Schuh M, Ellenberg J. A new model for asymmetric spindle positioning in mouse oocytes. Curr Biol 2008; 18:1986-92. [PMID: 19062278 DOI: 10.1016/j.cub.2008.11.022] [Citation(s) in RCA: 229] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2008] [Revised: 10/29/2008] [Accepted: 11/12/2008] [Indexed: 10/21/2022]
Abstract
An oocyte matures into an egg by extruding half of the chromosomes in a small polar body. This extremely asymmetric division enables the oocyte to retain sufficient storage material for the development of the embryo after fertilization. To divide asymmetrically, mammalian oocytes relocate the spindle from their center to the cortex. In all mammalian species analyzed so far, including human, mouse, cow, pig, and hamster, spindle relocation depends on filamentous actin (F-actin). However, even though spindle relocation is essential for fertility, the involved F-actin structures and the mechanism by which they relocate the spindle are unknown. Here we show in live mouse oocytes that spindle relocation requires a continuously reorganizing cytoplasmic actin network nucleated by Formin-2 (Fmn2). We found that the spindle poles were enriched in activated myosin and pulled on this network. Inhibition of myosin activation by myosin light chain kinase (MLCK) stopped pulling and spindle relocation, indicating that myosin pulling creates the force that drives spindle movement. Based on these results, we propose the first mechanistic model for asymmetric spindle positioning in mammalian oocytes and validate five of its key predictions experimentally.
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Affiliation(s)
- Melina Schuh
- European Molecular Biology Laboratory (EMBL), Gene Expression Unit, Heidelberg, Germany
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23
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Panbianco C, Weinkove D, Zanin E, Jones D, Divecha N, Gotta M, Ahringer J. A casein kinase 1 and PAR proteins regulate asymmetry of a PIP(2) synthesis enzyme for asymmetric spindle positioning. Dev Cell 2008; 15:198-208. [PMID: 18694560 PMCID: PMC2686839 DOI: 10.1016/j.devcel.2008.06.002] [Citation(s) in RCA: 71] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2007] [Revised: 03/21/2008] [Accepted: 06/04/2008] [Indexed: 01/19/2023]
Abstract
Spindle positioning is an essential feature of asymmetric cell division. The conserved PAR proteins together with heterotrimeric G proteins control spindle positioning in animal cells, but how these are linked is not known. In C. elegans, PAR protein activity leads to asymmetric spindle placement through cortical asymmetry of Gα regulators GPR-1/2. Here, we establish that the casein kinase 1 gamma CSNK-1 and a PIP2 synthesis enzyme (PPK-1) transduce PAR polarity to asymmetric Gα regulation. PPK-1 is posteriorly enriched in the one-celled embryo through PAR and CSNK-1 activities. Loss of CSNK-1 causes uniformly high PPK-1 levels, high symmetric cortical levels of GPR-1/2 and LIN-5, and increased spindle pulling forces. In contrast, knockdown of ppk-1 leads to low GPR-1/2 levels and decreased spindle forces. Furthermore, loss of CSNK-1 leads to increased levels of PIP2. We propose that asymmetric generation of PIP2 by PPK-1 directs the posterior enrichment of GPR-1/2 and LIN-5, leading to posterior spindle displacement.
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Affiliation(s)
- Costanza Panbianco
- The Gurdon Institute and Department of Genetics, University of Cambridge, Tennis Court Road, Cambridge CB21QN, UK
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24
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Hyenne V, Desrosiers M, Labbé JC. C. elegans Brat homologs regulate PAR protein-dependent polarity and asymmetric cell division. Dev Biol 2008; 321:368-78. [PMID: 18652816 DOI: 10.1016/j.ydbio.2008.06.037] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2008] [Revised: 06/25/2008] [Accepted: 06/25/2008] [Indexed: 12/18/2022]
Abstract
The evolutionary conserved PAR proteins control polarization and asymmetric division in many organisms. Recent work in Caenorhabditis elegans demonstrated that nos-3 and fbf-1/2 can suppress par-2(it5ts) lethality, suggesting that they participate in cell polarity by regulating the function of the anterior PAR-3/PAR-6/PKC-3 proteins. In Drosophila embryos, Nanos and Pumilio are homologous to NOS-3 and FBF-1/2 respectively and control cell polarity by forming a complex with the tumor suppressor Brat to inhibit Hunchback mRNA translation. In this study, we investigated the possibility that Brat could control cell polarity and asymmetric cell division in C. elegans. We found that disrupting four of the five C. elegans Brat homologs (Cebrats) individually results in suppression of par-2(it5ts) lethality, indicating that these genes are involved in embryonic polarity. Two of the Cebrats, ncl-1 and nhl-2, partially restore the localization of PAR proteins at the cortex. While mutations in the four Cebrat genes do not severely impair polarity, they display polarity-associated defects. Surprisingly, these defects are absent from nos-3 mutants. Similarly, while nos-3 controls PAR-6 protein levels, this is not the case for any of the Cebrats. Our results, together with results from Drosophila, indicate that Brat family members function in generating cellular asymmetries and suggest that, in contrast to Drosophila embryos, the C. elegans homologs of Brat and Nanos could participate in embryonic polarity via distinct mechanisms.
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Affiliation(s)
- Vincent Hyenne
- Cell Division and Differentiation Laboratory, Institute of Research in Immunology and Cancer, Université de Montréal, C.P. 6128, Succ Centre-ville Montréal, QC Canada H3C 3J7.
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25
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Lagos-Cabré R, Moreno RD. Mitotic, but not meiotic, oriented cell divisions in rat spermatogenesis. Reproduction 2008; 135:471-8. [PMID: 18296512 DOI: 10.1530/rep-07-0389] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
The process of mammalian spermatogenesis involves both mitosis and meiosis at the same developmental age. Most previous studies have focused on mitotic spindle orientation during development, but not during meiotic division. Therefore, we asked whether there is a difference between mitotic and meiotic germ cell spindle orientation during rat spermatogenesis. Our results showed that mitotic spindles of spermatogonia were mainly oriented with angles ranging from 60 to 90 degrees, perpendicular in relation to the basement membrane of the seminiferous tubules. On the other hand, meiotic spindles showed a random orientation. Nocodazole treatment (at a concentration that depolymerizes only astral microtubules) induced a significant increase in cells with an angle between 0 and 30 degrees (parallel) in relation to the basement membrane. Meiotic spindles did not show a significant change in their orientation after the Nocodazole treatment. Therefore, our results suggest differences between the mechanisms controlling positioning and orientation of mitotic and meiotic spindles during rat spermatogenesis. It seems that a phylogenetically conserved programme controls the mitotic spindle orientation in organisms ranging from worms to mammals.
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Affiliation(s)
- Raul Lagos-Cabré
- Departamento de Ciencias Fisiológicas, Facultad de Ciencias Biológicas, Pontificia Universidad Católica de Chile, Alameda 340, 8331010 Santiago, Chile
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26
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Toyoshima F, Nishida E. Spindle orientation in animal cell mitosis: roles of integrin in the control of spindle axis. J Cell Physiol 2008; 213:407-11. [PMID: 17654475 DOI: 10.1002/jcp.21227] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
The orientation of mitotic spindles, which determines the plane of cell division, is tightly regulated in polarized cells such as epithelial cells, but it has been unclear whether there is a mechanism regulating spindle orientation in non-polarized cultured cells. In adherent cultured cells, spindles are positioned at the center of the cells and the axis of the spindle lies in the longest axis of the cell. Thus, cell geometry is thought to be one of cues for spindle orientation and positioning in cultured cells because this defines the center and the long axis of the cell. Recent work provides a new insight into the spindle orientation in cultured cells; spindles are aligned along the axis parallel to the cell-substrate adhesion plane. Concomitantly, integrin-mediated cell adhesion to the extracellular matrix (ECM), rather than gravitation, cell-cell adhesion or cell geometry, has shown to be essential for this mechanism of spindle orientation. Several independent lines of evidence confirm the involvement of cell-ECM adhesion in spindle orientation in both cultured cells and in developing organisms. The important future challenge is to identify a molecular mechanism(s) that links integrin and spindles in the control of spindle axis.
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Affiliation(s)
- Fumiko Toyoshima
- Department of Cell and Developmental Biology, Graduate School of Biostudies, Kyoto University, Sakyo-ku, Kyoto, Japan.
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27
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AI JS, WANG Q, LI M, SHI LH, OLA SI, XIONG B, YIN S, CHEN DY, SUN QY. Roles of Microtubules and Microfilaments in Spindle Movements During Rat Oocyte Meiosis. J Reprod Dev 2008; 54:391-6. [DOI: 10.1262/jrd.20034] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Affiliation(s)
- Jun-Shu AI
- State Key Laboratory of Reproductive Biology, Institute of Zoology
- Graduate School, Chinese Academy of Sciences
| | - Qiang WANG
- State Key Laboratory of Reproductive Biology, Institute of Zoology
- Graduate School, Chinese Academy of Sciences
| | - Mo LI
- State Key Laboratory of Reproductive Biology, Institute of Zoology
- Graduate School, Chinese Academy of Sciences
| | - Li-Hong SHI
- State Key Laboratory of Reproductive Biology, Institute of Zoology
- Graduate School, Chinese Academy of Sciences
| | - Safiriyu Idowu OLA
- State Key Laboratory of Reproductive Biology, Institute of Zoology
- Department of Animal Science, Obafemi Awolowo University
| | - Bo XIONG
- State Key Laboratory of Reproductive Biology, Institute of Zoology
- Graduate School, Chinese Academy of Sciences
| | - Shen YIN
- State Key Laboratory of Reproductive Biology, Institute of Zoology
- Graduate School, Chinese Academy of Sciences
| | - Da-Yuan CHEN
- State Key Laboratory of Reproductive Biology, Institute of Zoology
| | - Qing-Yuan SUN
- State Key Laboratory of Reproductive Biology, Institute of Zoology
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28
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Negishi T, Takada T, Kawai N, Nishida H. Localized PEM mRNA and protein are involved in cleavage-plane orientation and unequal cell divisions in ascidians. Curr Biol 2007; 17:1014-25. [PMID: 17570671 DOI: 10.1016/j.cub.2007.05.047] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2007] [Revised: 05/17/2007] [Accepted: 05/17/2007] [Indexed: 01/01/2023]
Abstract
BACKGROUND Orientation and positioning of the cell division plane are essential for generation of invariant cleavage patterns and for unequal cell divisions during development. Precise control of the division plane is important for appropriate partitioning of localized factors, spatial arrangement of cells for proper intercellular interactions, and size control of daughter cells. Ascidian embryos show complex but invariant cleavage patterns mainly due to three rounds of unequal cleavage at the posterior pole. RESULTS The ascidian embryo is an emerging model for studies of developmental and cellular processes. The maternal Posterior End Mark (PEM) mRNA is localized within the egg and embryo to the posterior region. PEM is a novel protein that has no known domain. Immunostaining showed that the protein is also present in the posterior cortex and the in centrosome-attracting body (CAB) and that the localization is extraction-resistant. Here we show that PEM of Halocynthia roretzi is required for correct orientation of early-cleavage planes and subsequent unequal cell divisions because it repeatedly pulls a centrosome toward the posterior cortex and the CAB, respectively, where PEM mRNA and protein are localized. When PEM activity is suppressed, formation of the microtubule bundle linking the centrosome and the posterior cortex did not occur. PEM possibly plays a role in anchoring microtubule ends to the cortex. In our model of orientation of the early-cleavage planes, we also amend the allocation of the conventional animal-vegetal axis in ascidian embryos, and discuss how the newly proposed A-V axis provides the rationale for various developmental events and the fate map of this animal. CONCLUSIONS The complex cleavage pattern in ascidian embryos can be explained by a simple rule of centrosome attraction mediated by localized PEM activity. PEM is the first gene identified in ascidians that is required for multiple spindle-positioning events.
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Affiliation(s)
- Takefumi Negishi
- Department of Biological Sciences, Graduate School of Science, Osaka University, 1-1 Machikaneyama-cho, Toyonaka, Osaka 560-0043, Japan
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29
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Abstract
To divide asymmetrically, a cell must position the mitotic spindle relative to localized cell fate determinants. Recent work in the early ascidian embryo reveals the function of a single factor that coordinates this act to control cleavage pattern and cell fate determination.
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Affiliation(s)
- Edwin Munro
- Center for Cell Dynamics, Friday Harbor Laboratories, University of Washington, 620 University Road, Friday Harbor, Washington 98250, USA.
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30
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Kozlowski C, Srayko M, Nedelec F. Cortical microtubule contacts position the spindle in C. elegans embryos. Cell 2007; 129:499-510. [PMID: 17482544 DOI: 10.1016/j.cell.2007.03.027] [Citation(s) in RCA: 192] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2006] [Revised: 12/01/2006] [Accepted: 03/02/2007] [Indexed: 12/18/2022]
Abstract
Interactions between microtubules and the cell cortex play a critical role in positioning organelles in a variety of biological contexts. Here we used Caenorhabditis elegans as a model system to study how cortex-microtubule interactions position the mitotic spindle in response to polarity cues. Imaging EBP-2::GFP and YFP::alpha-tubulin revealed that microtubules shrink soon after cortical contact, from which we propose that cortical adaptors mediate microtubule depolymerization energy into pulling forces. We also observe association of dynamic microtubules to form astral fibers that persist, despite the catastrophe events of individual microtubules. Computer simulations show that these effects, which are crucially determined by microtubule dynamics, can explain anaphase spindle oscillations and posterior displacement in 3D.
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Affiliation(s)
- Cleopatra Kozlowski
- Cell Biology and Biophysics Unit, European Molecular Biology Laboratory, Heidelberg D-69117 Germany
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31
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Dajnowiec D, Sabatini PJB, Van Rossum TC, Lam JTK, Zhang M, Kapus A, Langille BL. Force-induced polarized mitosis of endothelial and smooth muscle cells in arterial remodeling. Hypertension 2007; 50:255-60. [PMID: 17485596 DOI: 10.1161/hypertensionaha.107.089730] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Arteries display highly directional growth and remodeling that are specific to increases in the mechanical loads imposed on them by blood pressure, blood flow, and lengthwise tensile forces that are transmitted from the tissues to which they are attached. This study examined the effect of mechanical forces on the direction in which mitosis delivers daughter cells, as a mechanism for directional growth. Lateral forces were imposed on surface integrins of cultured endothelial cells by seeding the cells with arginine-glycine-aspartate peptide-coated magnetic microspheres and applying a magnetic field. Video images revealed that the mitotic axis of dividing cells became highly biased in the direction of applied force. Distribution of cortactin, which participates in polarized mitoses driven by other stimuli, was highly sensitive to mechanical loading and interfering with cortactin function arrested cell growth. Smooth muscle cell mitoses also proved to be sensitive to mechanical force: when lengthwise force imposed on rabbit carotid arteries was altered by excision of a vessel segment and reanastomosis of the cut ends, direction of mitosis was dramatically altered. These findings indicate that influences of mechanical force can modulate the manner in which mitosis of vascular cells contributes to reorganization of arterial wall tissue.
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Affiliation(s)
- Dorota Dajnowiec
- Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, Ontario, Canada
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32
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Haarer BK, Helfant AH, Nelson SA, Cooper JA, Amberg DC. Stable preanaphase spindle positioning requires Bud6p and an apparent interaction between the spindle pole bodies and the neck. EUKARYOTIC CELL 2007; 6:797-807. [PMID: 17416900 PMCID: PMC1899834 DOI: 10.1128/ec.00332-06] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Faithful partitioning of genetic material during cell division requires accurate spatial and temporal positioning of nuclei within dividing cells. In Saccharomyces cerevisiae, nuclear positioning is regulated by an elegant interplay between components of the actin and microtubule cytoskeletons. Regulators of this process include Bud6p (also referred to as the actin-interacting protein Aip3p) and Kar9p, which function to promote contacts between cytoplasmic microtubule ends and actin-delimited cortical attachment points. Here, we present the previously undetected association of Bud6p with the cytoplasmic face of yeast spindle pole bodies, the functional equivalent of metazoan centrosomes. Cells lacking Bud6p show exaggerated movements of the nucleus between mother and daughter cells and display reduced amounts of time a given spindle pole body spends in close association with the neck region of budding cells. Furthermore, overexpression of BUD6 greatly enhances interactions between the spindle pole body and mother-bud neck in a spindle alignment-defective dynactin mutant. These results suggest that association of either spindle pole body with neck components, rather than simply entry of a spindle pole body into the daughter cell, provides a positive signal for the progression of mitosis. We propose that Bud6p, through its localization at both spindle pole bodies and at the mother-bud neck, supports this positive signal and provides a regulatory mechanism to prevent excessive oscillations of preanaphase nuclei, thus reducing the likelihood of mitotic delays and nuclear missegregation.
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Affiliation(s)
- Brian K Haarer
- Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, 750 E. Adams St., Syracuse, NY 13210, USA
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33
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Sardet C, Paix A, Prodon F, Dru P, Chenevert J. From oocyte to 16-cell stage: Cytoplasmic and cortical reorganizations that pattern the ascidian embryo. Dev Dyn 2007; 236:1716-31. [PMID: 17420986 DOI: 10.1002/dvdy.21136] [Citation(s) in RCA: 87] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
The dorsoventral and anteroposterior axes of the ascidian embryo are defined before first cleavage by means of a series of reorganizations that reposition cytoplasmic and cortical domains established during oogenesis. These domains situated in the periphery of the oocyte contain developmental determinants and a population of maternal postplasmic/PEM RNAs. One of these RNAs (macho-1) is a determinant for the muscle cells of the tadpole embryo. Oocytes acquire a primary animal-vegetal (a-v) axis during meiotic maturation, when a subcortical mitochondria-rich domain (myoplasm) and a domain rich in cortical endoplasmic reticulum (cER) and maternal postplasmic/PEM RNAs (cER-mRNA domain) become polarized and asymmetrically enriched in the vegetal hemisphere. Fertilization at metaphase of meiosis I initiates a series of dramatic cytoplasmic and cortical reorganizations of the zygote, which occur in two major phases. The first major phase depends on sperm entry which triggers a calcium wave leading in turn to an actomyosin-driven contraction wave. The contraction concentrates the cER-mRNA domain and myoplasm in and around a vegetal/contraction pole. The precise localization of the vegetal/contraction pole depends on both the a-v axis and the location of sperm entry and prefigures the future site of gastrulation and dorsal side of the embryo. The second major phase of reorganization occurs between meiosis completion and first cleavage. Sperm aster microtubules and then cortical microfilaments cause the cER-mRNA domain and myoplasm to reposition toward the posterior of the zygote. The location of the posterior pole depends on the localization of the sperm centrosome/aster attained during the first major phase of reorganization. Both cER-mRNA and myoplasm domains localized in the posterior region are partitioned equally between the first two blastomeres and then asymmetrically over the next two cleavages. At the eight-cell stage the cER-mRNA domain compacts and gives rise to a macroscopic cortical structure called the Centrosome Attracting Body (CAB). The CAB is responsible for a series of unequal divisions in posterior-vegetal blastomeres, and the postplasmic/PEM RNAs it contains are involved in patterning the posterior region of the embryo. In this review, we discuss these multiple events and phases of reorganizations in detail and their relationship to physiological, cell cycle, and cytoskeletal events. We also examine the role of the reorganizations in localizing determinants, postplasmic/PEM RNAs, and PAR polarity proteins in the cortex. Finally, we summarize some of the remaining questions concerning polarization of the ascidian embryo and provide comparisons to a few other species. A large collection of films illustrating the reorganizations can be consulted by clicking on "Film archive: ascidian eggs and embryos" at http://biodev.obs-vlfr.fr/recherche/biomarcell/.
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Affiliation(s)
- Christian Sardet
- BioMarCell group, UMR 7009 Biodev CNRS/ Université Pierre et Marie Curie (Paris VI), Observatoire Océanologique, Villefranche-sur-Mer, France.
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Bisgrove SR, Kropf DL. Asymmetric Cell Divisions: Zygotes of Fucoid Algae as a Model System. PLANT CELL MONOGRAPHS 2007. [DOI: 10.1007/7089_2007_134] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
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Heidstra R. Asymmetric Cell Division in Plant Development. PROGRESS IN MOLECULAR AND SUBCELLULAR BIOLOGY 2007; 45:1-37. [PMID: 17585494 DOI: 10.1007/978-3-540-69161-7_1] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Plant embryogenesis creates a seedling with a basic body plan. Post-embryonically the seedling elaborates with a lifelong ability to develop new tissues and organs. As a result asymmetric cell divisions serve essential roles during embryonic and postembryonic development to generate cell diversity. This review highlights selective cases of asymmetric division in the model plant Arabidopsis thaliana and describes the current knowledge on fate determinants and mechanisms involved. Common themes that emerge are: 1. role of the plant hormone auxin and its polar transport machinery; 2. a MAP kinase signaling cascade and; 3. asymmetric segregating transcription factors that are involved in several asymmetric cell divisions.
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Affiliation(s)
- Renze Heidstra
- Department of Biology, Section Molecular Genetics, Utrecht University, Padualaan 8, 3584CH Utrecht, Netherlands.
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Strawn LA, True HL. Deletion of RNQ1 gene reveals novel functional relationship between divergently transcribed Bik1p/CLIP-170 and Sfi1p in spindle pole body separation. Curr Genet 2006; 50:347-66. [PMID: 16972090 DOI: 10.1007/s00294-006-0098-6] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2006] [Revised: 08/17/2006] [Accepted: 08/19/2006] [Indexed: 02/03/2023]
Abstract
Spindle pole body (SPB; the microtubule organizing center in yeast) duplication is essential to form a bipolar spindle. The duplicated SPBs must then separate and migrate to opposite sides of the nucleus. We identified a novel functional relationship in SPB separation between the microtubule stabilizing protein Bik1p/CLIP-170 and the SPB half-bridge protein Sfi1p. A genetic interaction between BIK1 and SFI1 was discovered in a synthetic lethal screen using a strain deficient in the prion protein gene RNQ1. RNQ1 deletion reduced expression from the divergently transcribed BIK1, allowing us to identify genetic interactors with bik1. The sfi1-1 bik1 synthetic lethality was suppressed by over-expression of CIK1, KAR1, and PPH21. Genetic analysis indicated that the sfi1-1 bik1 synthetic lethality was unlikely related to the function of Bik1p in the dynein pathway or to defects in spindle position. Furthermore, a sfi1-1 Deltakip2 mutant was viable, suggesting that the Bik1p pool at the cytoplasmic microtubule plus-ends may not be required in sfi1-1. Microscopic examination indicated the sfi1-1 mutant was delayed in SPB duplication, SPB separation, or spindle elongation and the sfi-1 Deltabik1 double mutant arrested with duplicated but unseparated SPBs. These results suggest that Bik1p has a previously uncharacterized function in the separation of duplicated SPBs.
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Affiliation(s)
- Lisa A Strawn
- Department of Cell Biology and Physiology, Washington University School of Medicine, 660 S Euclid Ave, Campus Box 8228, St Louis, MO, 63110, USA.
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