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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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Sang Y, Silva-Ortega CO, Wu S, Yamaguchi N, Wu MF, Pfluger J, Gillmor CS, Gallagher KL, Wagner D. Mutations in two non-canonical Arabidopsis SWI2/SNF2 chromatin remodeling ATPases cause embryogenesis and stem cell maintenance defects. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2012; 72:1000-14. [PMID: 23062007 PMCID: PMC3561502 DOI: 10.1111/tpj.12009] [Citation(s) in RCA: 63] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
SWI2/SNF2 chromatin remodeling ATPases play important roles in plant and metazoan development. Whereas metazoans generally encode one or two SWI2/SNF2 ATPase genes, Arabidopsis encodes four such chromatin regulators: the well-studied BRAHMA and SPLAYED ATPases, as well as two closely related non-canonical SWI2/SNF2 ATPases, CHR12 and CHR23. No developmental role has as yet been described for CHR12 and CHR23. Here, we show that although strong single chr12 or chr23 mutants are morphologically indistinguishable from the wild type, chr12 chr23 double mutants cause embryonic lethality. The double mutant embryos fail to initiate root and shoot meristems, and display few and aberrant cell divisions. Weak double mutant embryos give rise to viable seedlings with dramatic defects in the maintenance of both the shoot and the root stem cell populations. Paradoxically, the stem cell defects are correlated with increased expression of the stem cell markers WUSCHEL and WOX5. During subsequent development, the meristem defects are partially overcome to allow for the formation of very small, bushy adult plants. Based on the observed morphological defects, we named the two chromatin remodelers MINUSCULE 1 and 2. Possible links between minu1 minu2 defects and defects in hormone signaling and replication-coupled chromatin assembly are discussed.
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Affiliation(s)
- Yi Sang
- Department of Biology, University of Pennsylvania, 415 S. University Ave, Philadelphia, PA, 19104
| | - Claudia O. Silva-Ortega
- Laboratorio Nacional de Genómica para la Biodiversidad (Langebio), CINVESTAV-IPN, Irapuato, Guanajuato, C.P 36821, MEXICO
| | - Shuang Wu
- Department of Biology, University of Pennsylvania, 415 S. University Ave, Philadelphia, PA, 19104
| | - Nobutoshi Yamaguchi
- Department of Biology, University of Pennsylvania, 415 S. University Ave, Philadelphia, PA, 19104
| | - Miin-Feng Wu
- Department of Biology, University of Pennsylvania, 415 S. University Ave, Philadelphia, PA, 19104
| | - Jennifer Pfluger
- Department of Biology, University of Pennsylvania, 415 S. University Ave, Philadelphia, PA, 19104
| | - C. Stewart Gillmor
- Laboratorio Nacional de Genómica para la Biodiversidad (Langebio), CINVESTAV-IPN, Irapuato, Guanajuato, C.P 36821, MEXICO
| | - Kimberly L. Gallagher
- Department of Biology, University of Pennsylvania, 415 S. University Ave, Philadelphia, PA, 19104
- authors for correspondence: Doris Wagner, tel: 215-898-0483, fax: 215 898-8780, ; Kimberly L. Gallagher, tel: 215 746-3605, fax: 215 898-8780,
| | - Doris Wagner
- Department of Biology, University of Pennsylvania, 415 S. University Ave, Philadelphia, PA, 19104
- authors for correspondence: Doris Wagner, tel: 215-898-0483, fax: 215 898-8780, ; Kimberly L. Gallagher, tel: 215 746-3605, fax: 215 898-8780,
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Stevermann L, Liakopoulos D. Molecular mechanisms in spindle positioning: structures and new concepts. Curr Opin Cell Biol 2012; 24:816-24. [PMID: 23142476 DOI: 10.1016/j.ceb.2012.10.005] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2012] [Revised: 10/08/2012] [Accepted: 10/15/2012] [Indexed: 10/27/2022]
Abstract
Coordination of cell cleavage with respect to cell geometry, cell polarity and neighboring tissues is critical for tissue maintenance, malignant transformation and metastasis. The position of the mitotic spindle within the cell determines where cell cleavage occurs. Spindle positioning is often mediated through capture of astral microtubules by motor proteins at the cell cortex. Recently, the core dynein anchor complex has been structurally resolved. Junctional complexes were shown to provide additional capture sites for astral microtubules in proliferating tissues. Finally, latest studies show that signals from centrosomes control spindle positioning and propose novel concepts for generation of centrosome identity.
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Affiliation(s)
- Lea Stevermann
- Heidelberg University Biochemistry Center (BZH) INF 328, 69120 Heidelberg, Germany
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Muroyama A, Lechler T. Polarity and stratification of the epidermis. Semin Cell Dev Biol 2012; 23:890-6. [PMID: 22960184 DOI: 10.1016/j.semcdb.2012.08.008] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2012] [Revised: 08/08/2012] [Accepted: 08/24/2012] [Indexed: 02/08/2023]
Abstract
Polarity is a fundamental property of epithelial cells. In this review, we discuss our current knowledge of the polarity of a stratified epithelium, the epidermis, focusing on similarities and differences with simple epithelial models. We highlight how the differences in tissue architecture and physiology result in alterations in some aspects of cell polarity. In addition, we discuss one of the most prominent uses for cell polarity in the epidermis-orienting the mitotic spindle to drive the stratification and differentiation of this tissue during development.
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Affiliation(s)
- Andrew Muroyama
- Department of Cell Biology, Duke University Medical Center, USA
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Bompard G, Morin N. p21-activated kinase 4 regulates mitotic spindle positioning and orientation. BIOARCHITECTURE 2012; 2:130-3. [PMID: 22960742 PMCID: PMC3675073 DOI: 10.4161/bioa.21132] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
During mitosis, microtubules (MTs) are massively rearranged into three sets of highly dynamic MTs that are nucleated from the centrosomes to form the mitotic spindle. Tight regulation of spindle positioning in the dividing cell and chromosome alignment at the center of the metaphase spindle are required to ensure perfect chromosome segregation and to position the cytokinetic furrow that will specify the two daughter cells. Spindle positioning requires regulation of MT dynamics, involving depolymerase activities together with cortical and kinetochore-mediated pushing and pulling forces acting on astral MTs and kinetochore fibres. These forces rely on MT motor activities. Cortical pulling forces exerted on astral MTs depend upon dynein/dynactin complexes and are essential in both symmetric and asymmetric cell division. A well-established spindle positioning pathway regulating the cortical targeting of dynein/dynactin involves the conserved LGN (Leu-Gly-Asn repeat-enriched-protein) and NuMA (microtubule binding nuclear mitotic apparatus protein) complex.1 Spindle orientation is also regulated by integrin-mediated cell adhesion2 and actin retraction fibres that respond to mechanical stress and are influenced by the microenvironment of the dividing cell.3 Altering the capture of astral MTs or modulating pulling forces affects spindle position, which can impair cell division, differentiation and embryogenesis.
In this general scheme, the activity of mitotic kinases such as Auroras and Plk1 (Polo-like kinase 1) is crucial.4 Recently, the p21-activated kinases (PAKs) emerged as novel important players in mitotic progression. In our recent article, we demonstrated that PAK4 regulates spindle positioning in symmetric cell division.5 In this commentary, and in light of recent published studies, we discuss how PAK4 could participate in the regulation of mechanisms involved in spindle positioning and orientation.
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Matsumura S, Toyoshima F. ABL1 Joins the Cadre of Spindle Orientation Machinery. Cell Struct Funct 2012; 37:81-7. [DOI: 10.1247/csf.12011] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Affiliation(s)
- Shigeru Matsumura
- Department of Cell Biology, Institute for Virus Research, Kyoto University
- Department of Cell Biology, Institute for Virus Research, Kyoto University
| | - Fumiko Toyoshima
- Department of Cell Biology, Institute for Virus Research, Kyoto University
- Department of Cell Biology, Institute for Virus Research, Kyoto University
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