201
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Abstract
The cytoskeleton is connected to the nuclear interior by LINC (linker of nucleoskeleton and cytoskeleton) complexes located in the nuclear envelope. These complexes consist of SUN proteins and nesprins present in the inner and outer nuclear membrane respectively. Whereas SUN proteins can bind the nuclear lamina, members of the nesprin protein family connect the nucleus to different components of the cytoskeleton. Nesprin-1 and -2 can establish a direct link with actin filaments, whereas nesprin-4 associates indirectly with microtubules through its interaction with kinesin-1. Nesprin-3 is the only family member known that can link the nuclear envelope to intermediate filaments. This indirect interaction is mediated by the binding of nesprin-3 to the cytoskeletal linker protein plectin. Furthermore, nesprin-3 can connect the nucleus to microtubules by its interactions with BPAG1 (bullous pemphigoid antigen 1) and MACF (microtubule-actin cross-linking factor). In contrast with the active roles that nesprin-1, -2 and -4 have in actin- and microtubule-dependent nuclear positioning, the role of nesprin-3 is likely to be more passive. We suggest that it helps to stabilize the anchorage of the nucleus within the cytoplasm and maintain the structural integrity and shape of the nucleus.
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202
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Borrego-Pinto J, Jegou T, Osorio DS, Auradé F, Gorjánácz M, Koch B, Mattaj IW, Gomes ER. Samp1 is a component of TAN lines and is required for nuclear movement. J Cell Sci 2012; 125:1099-105. [PMID: 22349700 DOI: 10.1242/jcs.087049] [Citation(s) in RCA: 84] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The position of the nucleus is regulated in different developmental stages and cellular events. During polarization, the nucleus moves away from the future leading edge and this movement is required for proper cell migration. Nuclear movement requires the LINC complex components nesprin-2G and SUN2, which form transmembrane actin-associated nuclear (TAN) lines at the nuclear envelope. Here we show that the nuclear envelope protein Samp1 (NET5) is involved in nuclear movement during fibroblast polarization and migration. Moreover, we demonstrate that Samp1 is a component of TAN lines that contain nesprin-2G and SUN2. Finally, Samp1 associates with SUN2 and lamin A/C, and the presence of Samp1 at the nuclear envelope requires lamin A/C. These results support a role for Samp1 in the association between the LINC complex and lamins during nuclear movement.
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203
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Cytoskeletal interactions at the nuclear envelope mediated by nesprins. Int J Cell Biol 2012; 2012:736524. [PMID: 22518138 PMCID: PMC3296292 DOI: 10.1155/2012/736524] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2011] [Revised: 10/13/2011] [Accepted: 10/18/2011] [Indexed: 11/29/2022] Open
Abstract
Nesprin-1 is a giant tail-anchored nuclear envelope protein composed of an N-terminal F-actin binding domain, a long linker region formed by multiple spectrin repeats and a C-terminal transmembrane domain. Based on this structure, it connects the nucleus to the actin cytoskeleton. Earlier reports had shown that Nesprin-1 binds to nuclear envelope proteins emerin and lamin through C-terminal spectrin repeats. These repeats can also self-associate. We focus on the N-terminal Nesprin-1 sequences and show that they interact with Nesprin-3, a further member of the Nesprin family, which connects the nucleus to the intermediate filament network. We show that upon ectopic expression of Nesprin-3 in COS7 cells, which are nearly devoid of Nesprin-3 in vitro, vimentin filaments are recruited to the nucleus and provide evidence for an F-actin interaction of Nesprin-3 in vitro. We propose that Nesprins through interactions amongst themselves and amongst the various Nesprins form a network around the nucleus and connect the nucleus to several cytoskeletal networks of the cell.
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204
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Dado D, Sagi M, Levenberg S, Zemel A. Mechanical control of stem cell differentiation. Regen Med 2012; 7:101-16. [DOI: 10.2217/rme.11.99] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
Numerous studies have focused on identifying the chemical and biological factors that govern the differentiation of stem cells; however, recent research has shown that mechanical cues may play an equally important role. Mechanical forces such as shear stresses and tensile loads, as well as the rigidity and topography of the extracellular matrix were shown to induce significant changes in the morphology and fate of stem cells. We survey experimental studies that focused on the response of stem cells to mechanical and geometrical properties of their environment and discuss the mechanical mechanisms that accompany their response including the remodeling of the cytoskeleton and determination of cell and nucleus size and shape.
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Affiliation(s)
- Dekel Dado
- Biomedical Engineering, Technion, Haifa, 32000, Israel
| | - Maayan Sagi
- Institute of Dental Sciences & the Fritz Haber Research Center, Hebrew-University, Hadassah Medical Center, Jerusalem, 91120, Israel
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205
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Zhou Z, Du X, Cai Z, Song X, Zhang H, Mizuno T, Suzuki E, Yee MR, Berezov A, Murali R, Wu SL, Karger BL, Greene MI, Wang Q. Structure of Sad1-UNC84 homology (SUN) domain defines features of molecular bridge in nuclear envelope. J Biol Chem 2011; 287:5317-26. [PMID: 22170055 DOI: 10.1074/jbc.m111.304543] [Citation(s) in RCA: 102] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The SUN (Sad1-UNC-84 homology) domain is conserved in a number of nuclear envelope proteins involved in nuclear migration, meiotic telomere tethering, and antiviral responses. The LINC (linker of nucleoskeleton and cytoskeleton) complex, formed by the SUN and the nesprin proteins at the nuclear envelope, serves as a mechanical linkage across the nuclear envelope. Here we report the crystal structure of the SUN2 protein SUN domain, which reveals a homotrimer. The SUN domain is sufficient to mediate binding to the KASH (Klarsicht, ANC-1, and Syne homology) domain of nesprin 2, and the regions involved in the interaction have been identified. Binding of the SUN domain to the KASH domain is abolished by deletion of a region important for trimerization or by point mutations associated with nuclear migration failure. We propose a model of the LINC complex, where the SUN and the KASH domains form a higher ordered oligomeric network in the nuclear envelope. These findings provide the structural basis for understanding the function and the regulation of the LINC complex.
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Affiliation(s)
- Zhaocai Zhou
- Department of Pathology and Laboratory Medicine, University of Pennsylvania, Perelman School of Medicine, Philadelphia, Pennsylvania 19104, USA
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206
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Lombardi ML, Lammerding J. Keeping the LINC: the importance of nucleocytoskeletal coupling in intracellular force transmission and cellular function. Biochem Soc Trans 2011; 39:1729-34. [PMID: 22103516 PMCID: PMC4589539 DOI: 10.1042/bst20110686] [Citation(s) in RCA: 92] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
Providing a stable physical connection between the nucleus and the cytoskeleton is essential for a wide range of cellular functions and it could also participate in mechanosensing by transmitting intra- and extra-cellular mechanical stimuli via the cytoskeleton to the nucleus. Nesprins and SUN proteins, located at the nuclear envelope, form the LINC (linker of nucleoskeleton and cytoskeleton) complex that connects the nucleus to the cytoskeleton; underlying nuclear lamins contribute to anchoring LINC complex components at the nuclear envelope. Disruption of the LINC complex or loss of lamins can result in disturbed perinuclear actin and intermediate filament networks and causes severe functional defects, including impaired nuclear positioning, cell polarization and cell motility. Recent studies have identified the LINC complex as the major force-transmitting element at the nuclear envelope and suggest that many of the aforementioned defects can be attributed to disturbed force transmission between the nucleus and the cytoskeleton. Thus mutations in nesprins, SUN proteins or lamins, which have been linked to muscular dystrophies and cardiomyopathies, may weaken or completely eliminate LINC complex function at the nuclear envelope and result in impaired intracellular force transmission, thereby disrupting critical cellular functions.
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Affiliation(s)
- Maria L. Lombardi
- Brigham and Women’s Hospital/Harvard Medical School, Department of Medicine, Cambridge, MA USA
| | - Jan Lammerding
- Brigham and Women’s Hospital/Harvard Medical School, Department of Medicine, Cambridge, MA USA
- Cornell University, Weill Institute for Cell and Molecular Biology, Department of Biomedical Engineering, Ithaca, NY USA
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207
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The role of nesprins as multifunctional organizers in the nucleus and the cytoskeleton. Biochem Soc Trans 2011; 39:1725-8. [DOI: 10.1042/bst20110668] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Nesprins (nuclear envelope spectrin repeat proteins), also known as SYNE (synaptic nuclear envelope protein), MYNE (myocyte nuclear envelope protein), ENAPTIN and NUANCE, are proteins that are primarily components of the nuclear envelope. The nuclear envelope is a continuous membrane system composed of two lipid bilayers: an inner and an outer nuclear membrane. Nesprins are components of both nuclear membranes and reach into the nucleoplasm and the cytoplasm, where they undergo different interactions and have the potential to influence transcriptional processes and cytoskeletal activities.
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208
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Moore SW, Sheetz MP. Biophysics of substrate interaction: influence on neural motility, differentiation, and repair. Dev Neurobiol 2011; 71:1090-101. [PMID: 21739614 PMCID: PMC3307797 DOI: 10.1002/dneu.20947] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
The identity and behavior of a cell is shaped by the molecular and mechanical composition of its surroundings. Molecular cues have firmly established roles in guiding both neuronal fate decisions and the migration of cells and axons. However, there is growing evidence that topographical and rigidity cues in the extracellular environment act synergistically with these molecular cues. Like chemical cues, physical factors do not elicit a fixed response, but rather one that depends on the sensory makeup of the cell. Moreover, from developmental studies and the plasticity of neural tissue, it is evident that there is dynamic feedback between physical and chemical factors to produce the final morphology. Here, we focus on our current understanding of how these physical cues shape cellular differentiation and migration, and discuss their relevance to repairing the injured nervous system.
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Affiliation(s)
- Simon W Moore
- Department of Biological Sciences, Columbia University, Sherman Fairchild Center, Amsterdam Ave., New York, NY 10027, USA.
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209
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Ferraro E, Pesaresi MG, De Zio D, Cencioni MT, Gortat A, Cozzolino M, Berghella L, Salvatore AM, Oettinghaus B, Scorrano L, Pérez-Payà E, Cecconi F. Apaf1 plays a pro-survival role by regulating centrosome morphology and function. J Cell Sci 2011; 124:3450-63. [DOI: 10.1242/jcs.086298] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
The apoptotic protease activating factor 1 (Apaf1) is the main component of the apoptosome, and a crucial factor in the mitochondria-dependent death pathway. Here we show that Apaf1 plays a role in regulating centrosome maturation. By analyzing Apaf1-depleted cells, we have found that Apaf1 loss induces centrosome defects that impair centrosomal microtubule nucleation and cytoskeleton organization. This, in turn, affects several cellular processes such as mitotic spindle formation, cell migration and mitochondrial network regulation. As a consequence, Apaf1-depleted cells are more fragile and have a lower threshold to stress than wild-type cells. In fact, we found that they exhibit low Bcl-2 and Bcl-XL expression and, under apoptotic treatment, rapidly release cytochrome c. We also show that Apaf1 acts by regulating the recruitment of HCA66, with which it interacts, to the centrosome. This function of Apaf1 is carried out during the cell life and is not related to its apoptotic role. Therefore, Apaf1 might also be considered a pro-survival molecule, whose absence impairs cell performance and causes a higher responsiveness to stressful conditions.
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Affiliation(s)
- Elisabetta Ferraro
- Laboratory of Molecular Neuroembryology, IRCCS Fondazione Santa Lucia, 00143, Rome, Italy
- Dulbecco Telethon Institute, Department of Biology, University of Rome ‘Tor Vergata’, 00133, Rome, Italy
| | | | - Daniela De Zio
- Dulbecco Telethon Institute, Department of Biology, University of Rome ‘Tor Vergata’, 00133, Rome, Italy
| | | | - Anne Gortat
- Department of Medicinal Chemistry, Centro de Investigación Príncipe Felipe, 46012 Valencia, Spain and IBV-CSIC, E-46010, Valencia, Spain
| | - Mauro Cozzolino
- Laboratory of Neurochemistry, IRCCS Fondazione Santa Lucia, 00143, Rome, Italy
| | | | | | - Bjorn Oettinghaus
- Department of Cell Physiology and Metabolism, University of Geneva, 1206, Geneva, Switzerland
| | - Luca Scorrano
- Department of Cell Physiology and Metabolism, University of Geneva, 1206, Geneva, Switzerland
| | - Enrique Pérez-Payà
- Department of Medicinal Chemistry, Centro de Investigación Príncipe Felipe, 46012 Valencia, Spain and IBV-CSIC, E-46010, Valencia, Spain
| | - Francesco Cecconi
- Laboratory of Molecular Neuroembryology, IRCCS Fondazione Santa Lucia, 00143, Rome, Italy
- Dulbecco Telethon Institute, Department of Biology, University of Rome ‘Tor Vergata’, 00133, Rome, Italy
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210
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Dupin I, Etienne-Manneville S. Nuclear positioning: mechanisms and functions. Int J Biochem Cell Biol 2011; 43:1698-707. [PMID: 21959251 DOI: 10.1016/j.biocel.2011.09.004] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2011] [Revised: 09/10/2011] [Accepted: 09/15/2011] [Indexed: 10/17/2022]
Abstract
The nucleus is the largest organelle in the cell and its position is dynamically controlled in space and time, although the functional significance of this dynamic regulation is not always clear. Nuclear movements are mediated by the cytoskeleton which transmits pushing or pulling forces onto the nuclear envelope. Recent studies have shed light on the mechanisms regulating nuclear positioning inside the cell. While microtubules have been known for a long time to be key players in nuclear positioning, the actin and cytoplasmic intermediate filament cytoskeletons have been implicated in this function more recently and various molecular links between the nuclear envelope and cytoplasmic elements have been identified. In this review, we summarize the recent advances in our understanding of the molecular mechanisms involved in the regulation of nuclear localization in various animal cells and give an overview of the evidence suggesting a crucial role of nuclear positioning in cell polarity and physiology and the consequences of nuclear mispositioning in human pathologies.
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Affiliation(s)
- Isabelle Dupin
- Institut Pasteur, Cell Polarity, Migration and Cancer Unit and CNRS URA 2582, 25 rue du Dr Roux, 75724 Paris Cedex 15, France
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211
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Nuclear structure and chromosome segregation in Drosophila male meiosis depend on the ubiquitin ligase dTopors. Genetics 2011; 189:779-93. [PMID: 21900273 DOI: 10.1534/genetics.111.133819] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
In many organisms, homolog pairing and synapsis at meiotic prophase depend on interactions between chromosomes and the nuclear membrane. Male Drosophila lack synapsis, but nonetheless, their chromosomes closely associate with the nuclear periphery at prophase I. To explore the functional significance of this association, we characterize mutations in nuclear blebber (nbl), a gene required for both spermatocyte nuclear shape and meiotic chromosome transmission. We demonstrate that nbl corresponds to dtopors, the Drosophila homolog of the mammalian dual ubiquitin/small ubiquitin-related modifier (SUMO) ligase Topors. We show that mutations in dtopors cause abnormalities in lamin localizations, centriole separation, and prophase I chromatin condensation and also cause anaphase I bridges that likely result from unresolved homolog connections. Bridge formation does not require mod(mdg4) in meiosis, suggesting that bridges do not result from misregulation of the male homolog conjunction complex. At the ultrastructural level, we observe disruption of nuclear shape, an uneven perinuclear space, and excess membranous structures. We show that dTopors localizes to the nuclear lamina at prophase, and also transiently to intranuclear foci. As a role of dtopors at gypsy insulator has been reported, we also asked whether these new alleles affected expression of the gypsy-induced mutation ct(6) and found that it was unaltered in dtopors homozygotes. Our results indicate that dTopors is required for germline nuclear structure and meiotic chromosome segregation, but in contrast, is not necessary for gypsy insulator function. We suggest that dtopors plays a structural role in spermatocyte lamina that is critical for multiple aspects of meiotic chromosome transmission.
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212
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Smith ER, Zhang XY, Capo-Chichi CD, Chen X, Xu XX. Increased expression of Syne1/nesprin-1 facilitates nuclear envelope structure changes in embryonic stem cell differentiation. Dev Dyn 2011; 240:2245-55. [PMID: 21932307 DOI: 10.1002/dvdy.22717] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/20/2011] [Indexed: 01/16/2023] Open
Abstract
We found by electron microscopy that the inter-membrane space of embryonic stem cells is irregular and generally wider than in differentiated cells. Among a panel of nuclear envelope structural proteins examined, the expression of Syne1/nesprin-1 was found to be greatly induced upon differentiation. Down-regulation of Syne1 by siRNA in differentiated embryonic stem cells caused the nuclear envelope to adopt a configuration resembling that found in undifferentiated embryonic stem cells. Suppression of Syne1 expression did not produce a detectable impact on the retinoic acid-induced differentiation of embryonic stem cells; however, forced expression of Syne1 enhanced the tendency of the cells to lose pluripotency. Thus, we found that low expression of Syne1 splicing isoforms accounts for the wider and irregular nuclear envelope inter-membrane space in embryonic stem cells. We conclude that the nuclear envelope structural change accompanying differentiation likely participates in promoting the differential chromatin organization of the differentiated cells.
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Affiliation(s)
- Elizabeth R Smith
- Sylvester Comprehensive Cancer Center, Department of Medicine, and Department of Obstetrics and Gynecology, University of Miami School of Medicine, Miami, Florida, USA
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213
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Mattioli E, Columbaro M, Capanni C, Maraldi NM, Cenni V, Scotlandi K, Marino MT, Merlini L, Squarzoni S, Lattanzi G. Prelamin A-mediated recruitment of SUN1 to the nuclear envelope directs nuclear positioning in human muscle. Cell Death Differ 2011; 18:1305-15. [PMID: 21311568 PMCID: PMC3097169 DOI: 10.1038/cdd.2010.183] [Citation(s) in RCA: 67] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2010] [Revised: 11/12/2010] [Accepted: 12/06/2010] [Indexed: 01/09/2023] Open
Abstract
Lamin A is a nuclear lamina constituent expressed in differentiated cells. Mutations in the LMNA gene cause several diseases, including muscular dystrophy and cardiomyopathy. Among the nuclear envelope partners of lamin A are Sad1 and UNC84 domain-containing protein 1 (SUN1) and Sad1 and UNC84 domain-containing protein 2 (SUN2), which mediate nucleo-cytoskeleton interactions critical to the anchorage of nuclei. In this study, we show that differentiating human myoblasts accumulate farnesylated prelamin A, which elicits upregulation and recruitment of SUN1 to the nuclear envelope and favors SUN2 enrichment at the nuclear poles. Indeed, impairment of prelamin A farnesylation alters SUN1 recruitment and SUN2 localization. Moreover, nuclear positioning in myotubes is severely affected in the absence of farnesylated prelamin A. Importantly, reduced prelamin A and SUN1 levels are observed in Emery-Dreifuss muscular dystrophy (EDMD) myoblasts, concomitant with altered myonuclear positioning. These results demonstrate that the interplay between SUN1 and farnesylated prelamin A contributes to nuclear positioning in human myofibers and may be implicated in pathogenetic mechanisms.
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Affiliation(s)
- E Mattioli
- Institute for Molecular Genetics, IGM-CNR, Unit of Bologna, Bologna, Italy
| | - M Columbaro
- Laboratory of Musculoskeletal Cell Biology, Istituto Ortopedico Rizzoli, Bologna, Italy
| | - C Capanni
- Institute for Molecular Genetics, IGM-CNR, Unit of Bologna, Bologna, Italy
| | - N M Maraldi
- Laboratory of Musculoskeletal Cell Biology, Istituto Ortopedico Rizzoli, Bologna, Italy
| | - V Cenni
- Institute for Molecular Genetics, IGM-CNR, Unit of Bologna, Bologna, Italy
| | - K Scotlandi
- Laboratory of Oncological Research, Istituto Ortopedico Rizzoli, Bologna, Italy
| | - M T Marino
- Laboratory of Oncological Research, Istituto Ortopedico Rizzoli, Bologna, Italy
| | - L Merlini
- Laboratory of Musculoskeletal Cell Biology, Istituto Ortopedico Rizzoli, Bologna, Italy
| | - S Squarzoni
- Institute for Molecular Genetics, IGM-CNR, Unit of Bologna, Bologna, Italy
| | - G Lattanzi
- Institute for Molecular Genetics, IGM-CNR, Unit of Bologna, Bologna, Italy
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214
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Lombardi ML, Jaalouk DE, Shanahan CM, Burke B, Roux KJ, Lammerding J. The interaction between nesprins and sun proteins at the nuclear envelope is critical for force transmission between the nucleus and cytoskeleton. J Biol Chem 2011; 286:26743-53. [PMID: 21652697 PMCID: PMC3143636 DOI: 10.1074/jbc.m111.233700] [Citation(s) in RCA: 400] [Impact Index Per Article: 28.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2011] [Revised: 05/19/2011] [Indexed: 02/04/2023] Open
Abstract
Maintaining physical connections between the nucleus and the cytoskeleton is important for many cellular processes that require coordinated movement and positioning of the nucleus. Nucleo-cytoskeletal coupling is also necessary to transmit extracellular mechanical stimuli across the cytoskeleton to the nucleus, where they may initiate mechanotransduction events. The LINC (Linker of Nucleoskeleton and Cytoskeleton) complex, formed by the interaction of nesprins and SUN proteins at the nuclear envelope, can bind to nuclear and cytoskeletal elements; however, its functional importance in transmitting intracellular forces has never been directly tested. This question is particularly relevant since recent findings have linked nesprin mutations to muscular dystrophy and dilated cardiomyopathy. Using biophysical assays to assess intracellular force transmission and associated cellular functions, we identified the LINC complex as a critical component for nucleo-cytoskeletal force transmission. Disruption of the LINC complex caused impaired propagation of intracellular forces and disturbed organization of the perinuclear actin and intermediate filament networks. Although mechanically induced activation of mechanosensitive genes was normal (suggesting that nuclear deformation is not required for mechanotransduction signaling) cells exhibited other severe functional defects after LINC complex disruption; nuclear positioning and cell polarization were impaired in migrating cells and in cells plated on micropatterned substrates, and cell migration speed and persistence time were significantly reduced. Taken together, our findings suggest that the LINC complex is critical for nucleo-cytoskeletal force transmission and that LINC complex disruption can result in defects in cellular structure and function that may contribute to the development of muscular dystrophies and cardiomyopathies.
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Affiliation(s)
- Maria L. Lombardi
- From the Department of Medicine, Brigham & Women's Hospital/Harvard Medical School, Cambridge, Massachusetts 02139
| | - Diana E. Jaalouk
- From the Department of Medicine, Brigham & Women's Hospital/Harvard Medical School, Cambridge, Massachusetts 02139
| | | | - Brian Burke
- the Institute of Medical Biology, 8A Biomedical Grove, Immunos, Singapore 138648, Singapore, and
| | - Kyle J. Roux
- the Department of Anatomy and Cell Biology, University of Florida, Gainesville, Florida 32610
| | - Jan Lammerding
- From the Department of Medicine, Brigham & Women's Hospital/Harvard Medical School, Cambridge, Massachusetts 02139
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215
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Lam LT, Böhm SV, Roberts RG, Morris GE. Nesprin-2 epsilon: a novel nesprin isoform expressed in human ovary and Ntera-2 cells. Biochem Biophys Res Commun 2011; 412:291-5. [PMID: 21820406 DOI: 10.1016/j.bbrc.2011.07.085] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2011] [Accepted: 07/20/2011] [Indexed: 11/17/2022]
Abstract
The nuclear envelope-associated cytoskeletal protein, nesprin-2, is encoded by a large gene containing several internal promoters that produce shorter isoforms. In a study of Ntera-2 teratocarcinoma cells, a novel isoform, nesprin-2-epsilon, was found to be the major mRNA and protein product of the nesprin-2 gene. Its existence was predicted by bioinformatic analysis, but this is the first direct demonstration of both the mRNA and the 120 kDa protein which is located at the nuclear envelope. In a panel of 21 adult and foetal human tissues, the nesprin-2-epsilon mRNA was strongly expressed in ovary but was a minor isoform elsewhere. The expression pattern suggests a possible link with very early development and a likely physiological role in ovary.
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Affiliation(s)
- Le Thanh Lam
- Wolfson Centre for Inherited Neuromuscular Disease, RJAH Orthopaedic Hospital, Oswestry SY10 7AG, UK
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216
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Talamas JA, Hetzer MW. POM121 and Sun1 play a role in early steps of interphase NPC assembly. ACTA ACUST UNITED AC 2011; 194:27-37. [PMID: 21727197 PMCID: PMC3135402 DOI: 10.1083/jcb.201012154] [Citation(s) in RCA: 106] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
POM121 and Sun1, but not the Nup107–160 complex, are required for fusion of the inner and outer nuclear membrane during nuclear pore assembly in interphase of the cell cycle. Nuclear pore complexes (NPCs) assemble at the end of mitosis during nuclear envelope (NE) reformation and into an intact NE as cells progress through interphase. Although recent studies have shown that NPC formation occurs by two different molecular mechanisms at two distinct cell cycle stages, little is known about the molecular players that mediate the fusion of the outer and inner nuclear membranes to form pores. In this paper, we provide evidence that the transmembrane nucleoporin (Nup), POM121, but not the Nup107–160 complex, is present at new pore assembly sites at a time that coincides with inner nuclear membrane (INM) and outer nuclear membrane (ONM) fusion. Overexpression of POM121 resulted in juxtaposition of the INM and ONM. Additionally, Sun1, an INM protein that is known to interact with the cytoskeleton, was specifically required for interphase assembly and localized with POM121 at forming pores. We propose a model in which POM121 and Sun1 interact transiently to promote early steps of interphase NPC assembly.
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Affiliation(s)
- Jessica A Talamas
- Molecular and Cell Biology Laboratory, Salk Institute for Biological Studies, La Jolla, CA 92037, USA
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217
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Lynes EM, Simmen T. Urban planning of the endoplasmic reticulum (ER): how diverse mechanisms segregate the many functions of the ER. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2011; 1813:1893-905. [PMID: 21756943 PMCID: PMC7172674 DOI: 10.1016/j.bbamcr.2011.06.011] [Citation(s) in RCA: 107] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/20/2011] [Revised: 06/22/2011] [Accepted: 06/23/2011] [Indexed: 12/21/2022]
Abstract
The endoplasmic reticulum (ER) is the biggest organelle in most cell types, but its characterization as an organelle with a continuous membrane belies the fact that the ER is actually an assembly of several, distinct membrane domains that execute diverse functions. Almost 20 years ago, an essay by Sitia and Meldolesi first listed what was known at the time about domain formation within the ER. In the time that has passed since, additional ER domains have been discovered and characterized. These include the mitochondria-associated membrane (MAM), the ER quality control compartment (ERQC), where ER-associated degradation (ERAD) occurs, and the plasma membrane-associated membrane (PAM). Insight has been gained into the separation of nuclear envelope proteins from the remainder of the ER. Research has also shown that the biogenesis of peroxisomes and lipid droplets occurs on specialized membranes of the ER. Several studies have shown the existence of specific marker proteins found on all these domains and how they are targeted there. Moreover, a first set of cytosolic ER-associated sorting proteins, including phosphofurin acidic cluster sorting protein 2 (PACS-2) and Rab32 have been identified. Intra-ER targeting mechanisms appear to be superimposed onto ER retention mechanisms and rely on transmembrane and cytosolic sequences. The crucial roles of ER domain formation for cell physiology are highlighted with the specific targeting of the tumor metastasis regulator gp78 to ERAD-mediating membranes or of the promyelocytic leukemia protein to the MAM.
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Affiliation(s)
- Emily M Lynes
- Department of Cell Biology, University of Alberta, Alberta, Canada
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218
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Jiang XZ, Yang MG, Huang LH, Li CQ, Xing XW. SPAG4L, a novel nuclear envelope protein involved in the meiotic stage of spermatogenesis. DNA Cell Biol 2011; 30:875-82. [PMID: 21711156 DOI: 10.1089/dna.2010.1161] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
SUN domain-containing proteins belong to a novel protein family. To date, several members--SUN1, SUN2, SUN3, and SPAG4--have been identified as nuclear envelope (NE) proteins. In this study, we sought to characterize and define the potential function of SPAG4L, a newly identified SUN protein. Using bioinformatic analysis, we found that SPAG4L contained a conserved SUN domain in the C-terminal. Subcellular localization analysis indicated that the expression of green fluorescent protein-labeled full-length SPAG4L was localized to the NE and the endoplasmic reticulum (ER). Deletion analysis revealed that the transmembrane region and the coiled-coil domain, but not the SUN domain, were required for localization of SPAG4L to the NE and ER. Subsequently, we confirmed that the human testes expressed endogenous SPAG4L as a 43-kDa protein. Further studies revealed that mouse Spag4L colocalized with the NE marker Lamin B1 and the ER marker PDI in isolated mouse spermatocytes. In addition, the expression of Spag4L was observed in meiosis I and II stages, suggesting that Spag4L may be involved in NE reconstitution and nuclear migration occurring during the process of spermatocyte division. Together, the findings indicate that SPAG4L, a new NE protein, may play an important role in the meiotic stage of spermatogenesis.
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Affiliation(s)
- Xian-Zhen Jiang
- Center for Medical Experiments, Third Xiang-Ya Hospital of Central South University, Changsha, China
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219
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Dupin I, Sakamoto Y, Etienne-Manneville S. Cytoplasmic intermediate filaments mediate actin-driven positioning of the nucleus. J Cell Sci 2011; 124:865-72. [PMID: 21378307 DOI: 10.1242/jcs.076356] [Citation(s) in RCA: 89] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The localization of the nucleus is precisely regulated, and defects in nuclear positioning are observed in diseases such as lissencephaly, cerebellar ataxia and dysplasia. We show here that cytoplasmic intermediate filaments are essential players in actin-dependent positioning of the nucleus. The actin retrograde flow is relayed by a flow of intermediate filaments that accumulate asymmetrically around the nuclear envelope. Perturbations of the intermediate filament network alter positioning of the nucleus in both migrating and immobile astrocytes. This function of intermediate filaments might be crucial for regulating cell motility, in particular in tumor cells expressing high levels of cytoplasmic intermediate filaments.
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Affiliation(s)
- Isabelle Dupin
- Institut Pasteur, Cell polarity and Migration Group and CNRS URA 2582, 25 rue du Dr Roux, 75724 Paris cedex 15, France
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220
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Gehrig K, Ridgway ND. CTP:phosphocholine cytidylyltransferase α (CCTα) and lamins alter nuclear membrane structure without affecting phosphatidylcholine synthesis. BIOCHIMICA ET BIOPHYSICA ACTA 2011; 1811:377-85. [PMID: 21504799 DOI: 10.1016/j.bbalip.2011.04.001] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/17/2010] [Revised: 03/28/2011] [Accepted: 04/01/2011] [Indexed: 11/21/2022]
Abstract
CTP:phosphocholine cytidylyltransferase α (CCTα) is a nuclear enzyme that catalyzes the rate-limiting step in the CDP-choline pathway for phosphatidylcholine (PC) synthesis. Lipid activation of CCTα results in its translocation to the nuclear envelope and expansion of an intranuclear membrane network termed the nucleoplasmic reticulum (NR) by a mechanism involving membrane deformation. Nuclear lamins are also required for stability and proliferation of the NR, but whether this unique structure, or the nuclear lamina in general, is required for PC synthesis is not known. To examine this relationship, the nuclear lamina was depleted by RNAi or disrupted by expression of the Hutchinson-Gilford progeria syndrome (HGPS) mutant lamin A (progerin), and the effect on CCTα and choline metabolism was analyzed. siRNA-mediated silencing of lamin A/C or lamin B1 in CHO cells to diminish the NR had no effect on PC synthesis, while double knockdown non-specifically inhibited the pathway. Confirming this minor role in PC synthesis, only 10% of transiently overexpressed choline/ethanolamine phosphotransferase was detected in the NR. In CHO cells, CCTα was nucleoplasmic and co-localized with GFP-progerin in nuclear folds and invaginations; however, HGPS fibroblasts displayed an abnormal distribution of CCTα in the cytoplasm and nuclear envelope that was accompanied by a 2-fold reduction in PC synthesis. In spite of its altered localization, choline-labeling experiments showed that CCT activity was unaffected, and inhibition of PC synthesis was traced to reduced activity of a hemicholinium-sensitive choline transporter. We conclude that CCTα and lamins specifically cooperate to form the NR, but the overall structure of the nuclear envelope has a minimal impact on CCT activity and PC synthesis.
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Affiliation(s)
- Karsten Gehrig
- Atlantic Research Centre, Departments of Pediatrics and Biochemistry and Molecular Biology, Dalhousie University, Halifax, Nova Scotia, Canada
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221
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Liang Y, Chiu PH, Yip KY, Chan SY. Subcellular localization of SUN2 is regulated by lamin A and Rab5. PLoS One 2011; 6:e20507. [PMID: 21655223 PMCID: PMC3105078 DOI: 10.1371/journal.pone.0020507] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2011] [Accepted: 05/03/2011] [Indexed: 11/18/2022] Open
Abstract
SUN2 is an inner nuclear membrane protein with a conserved Sad1/UNC-84 homology SUN-domain at the C-terminus. Intriguingly, SUN2 has also been reported to interact with Rab5, which localizes in early endosomes. To clarify the dual subcellular localization of SUN2, we investigated its localization in lamin A/C deficient cells rescued with lamin A or lamin C isoform, and in HeLa cells transfected with Rab5 or its mutants. We found that expression of lamin A but not lamin C partly restored the nuclear envelope localization of SUN2. SUN2 was redistributed to endosomes upon overexpression of Rab5, but remained on the nuclear envelope when the SUN domain was deleted. To explore the physiological function of SUN2 in vesicle trafficking and endocytosis, we demonstrated the colocalization of endogenous SUN2 and Rab5. Moreover, overexpression of SUN2 stimulated the uptake of transferrin while suppression of SUN2 expression attenuated the process. These findings support a role of SUN2 in endocytosis.
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Affiliation(s)
- Ying Liang
- Department of Paediatrics and Adolescent Medicine, Li Ka Shing Faculty of Medicine, University of Hong Kong, Pokfulam, Hong Kong SAR, China
| | - Peng Hang Chiu
- Department of Paediatrics and Adolescent Medicine, Li Ka Shing Faculty of Medicine, University of Hong Kong, Pokfulam, Hong Kong SAR, China
| | - Kit Yan Yip
- Department of Paediatrics and Adolescent Medicine, Li Ka Shing Faculty of Medicine, University of Hong Kong, Pokfulam, Hong Kong SAR, China
| | - Siu Yuen Chan
- Department of Paediatrics and Adolescent Medicine, Li Ka Shing Faculty of Medicine, University of Hong Kong, Pokfulam, Hong Kong SAR, China
- * E-mail:
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222
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Schneider M, Lu W, Neumann S, Brachner A, Gotzmann J, Noegel AA, Karakesisoglou I. Molecular mechanisms of centrosome and cytoskeleton anchorage at the nuclear envelope. Cell Mol Life Sci 2011; 68:1593-610. [PMID: 20922455 PMCID: PMC11115004 DOI: 10.1007/s00018-010-0535-z] [Citation(s) in RCA: 66] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2010] [Revised: 09/13/2010] [Accepted: 09/14/2010] [Indexed: 01/07/2023]
Abstract
Cell polarization is a fundamental process underpinning organismal development, and tissue homeostasis, which requires an orchestrated interplay of nuclear, cytoskeletal, and centrosomal structures. The underlying molecular mechanisms, however, still remain elusive. Here we report that kinesin-1/nesprin-2/SUN-domain macromolecular assemblies, spanning the entire nuclear envelope (NE), function in cell polarization by anchoring cytoskeletal structures to the nuclear lamina. Nesprin-2 forms complexes with the kinesin-1 motor protein apparatus by associating with and recruiting kinesin light chain 1 (KLC1) to the outer nuclear membrane. Similar to nesprin-2, KLC1 requires lamin A/C for proper NE localization. The depletion of nesprin-2 or KLC1, or the uncoupling of nesprin-2/SUN-domain protein associations impairs cell polarization during wounding and dislodges the centrosome from the NE. In addition nesprin-2 loss has profound effects on KLC1 levels, the cytoskeleton, and Golgi apparatus organization. Collectively these data show that NE-associated proteins are pivotal determinants of cell architecture and polarization.
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Affiliation(s)
- Maria Schneider
- School of Biological and Biomedical Sciences, University of Durham, Durham, DH1 3LE UK
- Center for Biochemistry, Center for Molecular Medicine Cologne (CMMC), Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (CECAD), Medical Faculty, University of Cologne, 50931 Cologne, Germany
| | - Wenshu Lu
- School of Biological and Biomedical Sciences, University of Durham, Durham, DH1 3LE UK
| | - Sascha Neumann
- Center for Biochemistry, Center for Molecular Medicine Cologne (CMMC), Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (CECAD), Medical Faculty, University of Cologne, 50931 Cologne, Germany
| | - Andreas Brachner
- Max F. Perutz Laboratories, Medical University of Vienna, 1030 Vienna, Austria
| | - Josef Gotzmann
- Max F. Perutz Laboratories, Medical University of Vienna, 1030 Vienna, Austria
| | - Angelika A. Noegel
- Center for Biochemistry, Center for Molecular Medicine Cologne (CMMC), Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (CECAD), Medical Faculty, University of Cologne, 50931 Cologne, Germany
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223
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Oda Y, Fukuda H. Dynamics of Arabidopsis SUN proteins during mitosis and their involvement in nuclear shaping. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2011; 66:629-41. [PMID: 21294795 DOI: 10.1111/j.1365-313x.2011.04523.x] [Citation(s) in RCA: 95] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
The nuclear envelope (NE) is a highly active structure with a specific set of nuclear envelope proteins acting in diverse cellular events. SUN proteins are conserved NE proteins among eukaryotes. Although they form nucleocytoplasmic linkage complexes in metazoan cells, their functions in the plant kingdom are unknown. To understand the function of plant SUN proteins, in this study we first investigated the dynamics of Arabidopsis SUN proteins during mitosis in Arabidopsis roots and cultured cells. For this purpose, we performed dual and triple visualization of these proteins, microtubules, chromosomes, and endoplasmic reticulum (ER) in cultured cells, and observed their dynamics during mitosis using a high-speed spinning disk confocal microscope. The localizations of SUN proteins changed dynamically during mitosis, tightly coupled with NE dynamics. Moreover, NE re-formation marked with SUN proteins is temporally and spatially coordinated with plant-specific microtubule structures such as phragmoplasts. Finally, the analysis with gene knockdowns of AtSUN1 and AtSUN2 indicated that they are necessary for the maintenance and/or formation of polarized nuclear shape in root hairs. These results suggest that Arabidopsis SUN proteins function in the maintenance or formation of nuclear shape as components of the nucleocytoskeletal complex.
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Affiliation(s)
- Yoshihisa Oda
- Department of Biological Sciences, Graduate School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan.
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224
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Gardner JM, Smoyer CJ, Stensrud ES, Alexander R, Gogol M, Wiegraebe W, Jaspersen SL. Targeting of the SUN protein Mps3 to the inner nuclear membrane by the histone variant H2A.Z. ACTA ACUST UNITED AC 2011; 193:489-507. [PMID: 21518795 PMCID: PMC3087001 DOI: 10.1083/jcb.201011017] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Binding of histone H2A.Z to the SUN family member Mps3 is chromatin independent. Understanding the relationship between chromatin and proteins at the nuclear periphery, such as the conserved SUN family of inner nuclear membrane (INM) proteins, is necessary to elucidate how three-dimensional nuclear architecture is established and maintained. We found that the budding yeast SUN protein Mps3 directly binds to the histone variant H2A.Z but not other histones. Biochemical and genetic data indicate that the interaction between Mps3 and H2A.Z requires the Mps3 N-terminal acidic domain and unique sequences in the H2A.Z N terminus and histone-fold domain. Analysis of binding-defective mutants showed that the Mps3–H2A.Z interaction is not essential for any previously described role for either protein in nuclear organization, and multiple lines of evidence suggest that Mps3–H2A.Z binding occurs independently of H2A.Z incorporation into chromatin. We demonstrate that H2A.Z is required to target a soluble Mps3 fragment to the nucleus and to localize full-length Mps3 in the INM, indicating that H2A.Z has a novel chromatin-independent function in INM targeting of SUN proteins.
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225
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Postel R, Ketema M, Kuikman I, de Pereda JM, Sonnenberg A. Nesprin-3 augments peripheral nuclear localization of intermediate filaments in zebrafish. J Cell Sci 2011; 124:755-64. [PMID: 21303928 DOI: 10.1242/jcs.081174] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The outer nuclear membrane protein nesprin-3 binds the cytoskeletal linker protein plectin, which are proposed to anchor the intermediate filaments to the nuclear envelope. To investigate the function of nesprin-3 in vivo, we used the zebrafish as a vertebrate model system. Zebrafish nesprin-3 is expressed at the nuclear envelope of epidermal and skeletal muscle cells during development. Unexpectedly, loss of nesprin-3 did not affect embryonic development, viability or fertility. However, nesprin-3-deficient zebrafish embryos showed a reduced concentration of intermediate filaments around the nucleus. Additional analysis revealed the presence of two nesprin-3 isoforms in zebrafish, nesprin-3α and nesprin-3β. Nesprin-3β is only expressed during early development and lacks seven amino acids in its first spectrin repeat that are crucial for plectin binding and recruitment to the nuclear envelope. These seven amino acids are highly conserved and we showed that residues R43 and L44 within this motif are required for plectin binding. Furthermore, several residues in the actin-binding domain of plectin that are crucial for binding to the integrin β4 subunit are also important for the binding to nesprin-3α, indicating partial overlapping binding sequences for nesprin-3α and integrin β4. All this shows that nesprin-3 is dispensable for normal development in zebrafish, but important for mediating the association of the intermediate filament system with the nucleus in vivo.
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Affiliation(s)
- Ruben Postel
- Division of Cell Biology, The Netherlands Cancer Institute, Plesmanlaan 121, 1066 CX Amsterdam, The Netherlands
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226
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Mellad JA, Warren DT, Shanahan CM. Nesprins LINC the nucleus and cytoskeleton. Curr Opin Cell Biol 2011; 23:47-54. [PMID: 21177090 DOI: 10.1016/j.ceb.2010.11.006] [Citation(s) in RCA: 112] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2010] [Revised: 11/19/2010] [Accepted: 11/27/2010] [Indexed: 01/08/2023]
Abstract
Like other spectrin repeat proteins, nesprins co-ordinate and maintain cellular architecture by linking membranous organelles to the cytoskeleton. However nuclear envelope (NE) nesprins, uniquely hardwire the nuclear lamina to the cytoskeleton and molecular motors. Emerging evidence suggests that nesprins also form a continuous network linking the plasma membrane to the NE that potentially translates mechanical stimuli into nuclear reorganisation. Surprisingly, this network is also essential for cytoskeletal organisation and its disruption has dramatic effects on nuclear migration, centrosomal positioning, focal adhesion maturation and cell motility. Herein we review recent advances in our understanding of how nesprins couple to various filamentous systems within the cell and emphasise the importance of both KASH and KASH-less nesprin isoforms in these interactions.
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Affiliation(s)
- Jason A Mellad
- BHF Centre of Research Excellence, Division of Cardiovascular Medicine, King's College London, SE5 9NU, UK
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227
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Gerlitz G, Bustin M. The role of chromatin structure in cell migration. Trends Cell Biol 2011; 21:6-11. [PMID: 20951589 PMCID: PMC3014417 DOI: 10.1016/j.tcb.2010.09.002] [Citation(s) in RCA: 65] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2010] [Revised: 08/24/2010] [Accepted: 09/01/2010] [Indexed: 10/18/2022]
Abstract
Chromatin dynamics play a major role in regulating genetic processes. Now, accumulating data suggest that chromatin structure may also affect the mechanical properties of the nucleus and cell migration. Global chromatin organization appears to modulate the shape, the size and the stiffness of the nucleus. Directed-cell migration, which often requires nuclear reshaping to allow passage of cells through narrow openings, is dependent not only on changes in cytoskeletal elements but also on global chromatin condensation. Conceivably, during cell migration a physical link between the chromatin and the cytoskeleton facilitates coordinated structural changes in these two components. Thus, in addition to regulating genetic processes, we suggest that alterations in chromatin structure could facilitate cellular reorganizations necessary for efficient migration.
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Affiliation(s)
- Gabi Gerlitz
- Protein Section, Laboratory of Metabolism, National Cancer Institute, US National Institutes of Health, Bethesda, MD 20892, USA.
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228
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Yu J, Lei K, Zhou M, Craft CM, Xu G, Xu T, Zhuang Y, Xu R, Han M. KASH protein Syne-2/Nesprin-2 and SUN proteins SUN1/2 mediate nuclear migration during mammalian retinal development. Hum Mol Genet 2010; 20:1061-73. [PMID: 21177258 DOI: 10.1093/hmg/ddq549] [Citation(s) in RCA: 132] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Nuclear movement relative to cell bodies is a fundamental process during certain aspects of mammalian retinal development. During the generation of photoreceptor cells in the cell division cycle, the nuclei of progenitors oscillate between the apical and basal surfaces of the neuroblastic layer (NBL). This process is termed interkinetic nuclear migration (INM). Furthermore, newly formed photoreceptor cells migrate and form the outer nuclear layer (ONL). In the current study, we demonstrated that a KASH domain-containing protein, Syne-2/Nesprin-2, as well as SUN domain-containing proteins, SUN1 and SUN2, play critical roles during INM and photoreceptor cell migration in the mouse retina. A deletion mutation of Syne-2/Nesprin-2 or double mutations of Sun1 and Sun2 caused severe reduction of the thickness of the ONL, mislocalization of photoreceptor nuclei and profound electrophysiological dysfunction of the retina characterized by a reduction of a- and b-wave amplitudes. We also provide evidence that Syne-2/Nesprin-2 forms complexes with either SUN1 or SUN2 at the nuclear envelope to connect the nucleus with dynein/dynactin and kinesin molecular motors during the nuclear migrations in the retina. These key retinal developmental signaling results will advance our understanding of the mechanism of nuclear migration in the mammalian retina.
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Affiliation(s)
- Juehua Yu
- Institute of Developmental Biology and Molecular Medicine, School of Life Science, Fudan University, Shanghai 200433, China
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229
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Frohnert C, Schweizer S, Hoyer-Fender S. SPAG4L/SPAG4L-2 are testis-specific SUN domain proteins restricted to the apical nuclear envelope of round spermatids facing the acrosome. Mol Hum Reprod 2010; 17:207-18. [DOI: 10.1093/molehr/gaq099] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
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230
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Randles KN, Lam LT, Sewry CA, Puckelwartz M, Furling D, Wehnert M, McNally EM, Morris GE. Nesprins, but not sun proteins, switch isoforms at the nuclear envelope during muscle development. Dev Dyn 2010; 239:998-1009. [PMID: 20108321 DOI: 10.1002/dvdy.22229] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022] Open
Abstract
Nesprins are a family of nuclear transmembrane proteins anchored via Sun proteins to the nuclear membrane. Analysis of nesprins during human muscle development revealed an increase in nesprin-1-giant during early myogenesis in vitro. During the transition from immature to mature muscle fibres in vivo, nesprin-2 partly replaced nesprin-1 at the nuclear envelope and short nesprin isoforms became dominant. Sun1 and Sun2 proteins remained unchanged during this fibre maturation. In emerin-negative skin fibroblasts, nesprin-2-giant was relocated from the nuclear envelope to the cytoplasm, not to the endoplasmic reticulum, while nesprin-1 remained at the nuclear envelope. In emerin-negative keratinocytes lacking nesprin-1, nesprin-2 remained at the nuclear envelope. HeLa cell nuclear envelopes lacked nesprin-1, which was the dominant form in myoblasts, while a novel 130-kD nesprin-2 isoform dominated Ntera-2 cells. The results suggest the possibility of isoform-specific and tissue-specific roles for nesprins in nuclear positioning.
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Affiliation(s)
- K Natalie Randles
- Wolfson Centre for Inherited Neuromuscular Disease, RJAH Orthopaedic Hospital, Oswestry, United Kingdom
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231
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Fridolfsson HN, Starr DA. Kinesin-1 and dynein at the nuclear envelope mediate the bidirectional migrations of nuclei. ACTA ACUST UNITED AC 2010; 191:115-28. [PMID: 20921138 PMCID: PMC2953438 DOI: 10.1083/jcb.201004118] [Citation(s) in RCA: 126] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Kinesin-1 and dynein are recruited to the nuclear envelope by the Caenorhabditis elegans klarsicht/ANC-1/Syne homology (KASH) protein UNC-83 to move nuclei. The mechanisms of how these motors are coordinated to mediate nuclear migration are unknown. Time-lapse differential interference contrast and fluorescence imaging of embryonic hypodermal nuclear migration events were used to characterize the kinetics of nuclear migration and determine microtubule dynamics and polarity. Wild-type nuclei display bidirectional movements during migration and are also able to roll past cytoplasmic granules. unc-83, unc-84, and kinesin-1 mutants have severe nuclear migration defects. Without dynein, nuclear migration initiates normally but lacks bidirectional movement and shows defects in nuclear rolling, implicating dynein in resolution of cytoplasmic roadblocks. Microtubules are highly dynamic during nuclear migration. EB1::green fluorescence protein imaging demonstrates that microtubules are polarized in the direction of nuclear migration. This organization of microtubules fits with our model that kinesin-1 moves nuclei forward and dynein functions to move nuclei backward for short stretches to bypass cellular roadblocks.
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Affiliation(s)
- Heidi N Fridolfsson
- Department of Molecular and Cellular Biology, University of California, Davis, Davis, CA 95616, USA
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232
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Chancellor TJ, Lee J, Thodeti CK, Lele T. Actomyosin tension exerted on the nucleus through nesprin-1 connections influences endothelial cell adhesion, migration, and cyclic strain-induced reorientation. Biophys J 2010; 99:115-23. [PMID: 20655839 DOI: 10.1016/j.bpj.2010.04.011] [Citation(s) in RCA: 149] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2009] [Revised: 03/31/2010] [Accepted: 04/01/2010] [Indexed: 11/20/2022] Open
Abstract
Endothelial cell polarization and directional migration is required for angiogenesis. Polarization and motility requires not only local cytoskeletal remodeling but also the motion of intracellular organelles such as the nucleus. However, the physiological significance of nuclear positioning in the endothelial cell has remained largely unexplored. Here, we show that siRNA knockdown of nesprin-1, a protein present in the linker of nucleus to cytoskeleton complex, abolished the reorientation of endothelial cells in response to cyclic strain. Confocal imaging revealed that the nuclear height is substantially increased in nesprin-1 depleted cells, similar to myosin inhibited cells. Nesprin-1 depletion increased the number of focal adhesions and substrate traction while decreasing the speed of cell migration; however, there was no detectable change in nonmuscle myosin II activity in nesprin-1 deficient cells. Together, these results are consistent with a model in which the nucleus balances a portion of the actomyosin tension in the cell. In the absence of nesprin-1, actomyosin tension is balanced by the substrate, leading to abnormal adhesion, migration, and cyclic strain-induced reorientation.
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Affiliation(s)
- T J Chancellor
- Department of Chemical Engineering, University of Florida, Gainesville, Florida, USA
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233
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Starr DA, Fridolfsson HN. Interactions between nuclei and the cytoskeleton are mediated by SUN-KASH nuclear-envelope bridges. Annu Rev Cell Dev Biol 2010; 26:421-44. [PMID: 20507227 DOI: 10.1146/annurev-cellbio-100109-104037] [Citation(s) in RCA: 438] [Impact Index Per Article: 29.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
The nuclear envelope links the cytoskeleton to structural components of the nucleus. It functions to coordinate nuclear migration and anchorage, organize chromatin, and aid meiotic chromosome pairing. Forces generated by the cytoskeleton are transferred across the nuclear envelope to the nuclear lamina through a nuclear-envelope bridge consisting of SUN (Sad1 and UNC-84) and KASH (Klarsicht, ANC-1 and Syne/Nesprin homology) proteins. Some KASH-SUN combinations connect microtubules, centrosomes, actin filaments, or intermediate filaments to the surface of the nucleus. Other combinations are used in cell cycle control, nuclear import, or apoptosis. Interactions between the cytoskeleton and the nucleus also affect global cytoskeleton organization. SUN and KASH proteins were identified through genetic screens for mispositioned nuclei in model organisms. Knockouts of SUN or KASH proteins disrupt neurological and muscular development in mice. Defects in SUN and KASH proteins have been linked to human diseases including muscular dystrophy, ataxia, progeria, lissencephaly, and cancer.
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Affiliation(s)
- Daniel A Starr
- Department of Molecular and Cellular Biology, University of California, Davis, California 95616, USA.
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234
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Brosig M, Ferralli J, Gelman L, Chiquet M, Chiquet-Ehrismann R. Interfering with the connection between the nucleus and the cytoskeleton affects nuclear rotation, mechanotransduction and myogenesis. Int J Biochem Cell Biol 2010; 42:1717-28. [DOI: 10.1016/j.biocel.2010.07.001] [Citation(s) in RCA: 78] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2010] [Revised: 07/01/2010] [Accepted: 07/03/2010] [Indexed: 01/02/2023]
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235
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Neumann S, Schneider M, Daugherty RL, Gottardi CJ, Eming SA, Beijer A, Noegel AA, Karakesisoglou I. Nesprin-2 interacts with {alpha}-catenin and regulates Wnt signaling at the nuclear envelope. J Biol Chem 2010; 285:34932-8. [PMID: 20801886 DOI: 10.1074/jbc.m110.119651] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Nesprins and emerin are structural nuclear envelope proteins that tether nuclei to the cytoskeleton. In this work, we identified the cytoskeleton-associated α-N/E-catenins as novel nesprin-2-binding partners. The association involves the C termini of nesprin-2 giant and α-N/E-catenins. α-E/T/N-catenins are known primarily for their roles in cadherin-mediated cell-cell adhesion. Here, we show that, in addition, α-catenin forms complexes with nesprin-2 that include β-catenin and emerin. We demonstrate that the depletion of nesprin-2 reduces both the amount of active β-catenin inside the nucleus and T-cell factor/lymphoid-enhancing factor-dependent transcription. Taken together, these findings suggest novel nesprin-2 functions in cellular signaling. Moreover, we propose that, in contrast to emerin, nesprin-2 is a positive regulator of the Wnt signaling pathway.
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Affiliation(s)
- Sascha Neumann
- Institute of Biochemistry I, Medical Faculty, Center for Molecular Medicine, University of Cologne, Cologne Excellence Cluster on Cellular Stress Responses in Aging-associated Diseases, 50931 Cologne, Germany
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236
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Zhou K, Hanna-Rose W. Movers and shakers or anchored: Caenorhabditis elegans nuclei achieve it with KASH/SUN. Dev Dyn 2010; 239:1352-64. [PMID: 20108325 DOI: 10.1002/dvdy.22226] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
The invariant cell division patterns that characterize Caenorhabditis elegans development make it an ideal system to study the mechanisms that control nuclear movement and positioning. Forward genetic screens in this system allowed identification of the key molecular machinery for connecting the nucleus to the cytoskeleton; pairs of protein partners, consisting of a KASH domain protein and a SUN domain protein, bridge the nuclear envelope to connect the nucleus to cytoskeletal components. The C. elegans genome encodes several KASH/SUN pairs, and mutant phenotypes as well as tissue-specific expression patterns suggest a diversity of functions. These functions include moving the nucleus but have been extended to effects on the chromosomes inside the nucleus as well. We review the impact of the C. elegans system in pioneering this field as well as the functions of these KASH/SUN protein pairs across spatial and temporal C. elegans development.
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Affiliation(s)
- Kang Zhou
- Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, Pennsylvania 16802, USA
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237
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Dialynas G, Speese S, Budnik V, Geyer PK, Wallrath LL. The role of Drosophila Lamin C in muscle function and gene expression. Development 2010; 137:3067-77. [PMID: 20702563 DOI: 10.1242/dev.048231] [Citation(s) in RCA: 91] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
The inner side of the nuclear envelope (NE) is lined with lamins, a meshwork of intermediate filaments that provides structural support for the nucleus and plays roles in many nuclear processes. Lamins, classified as A- or B-types on the basis of biochemical properties, have a conserved globular head, central rod and C-terminal domain that includes an Ig-fold structural motif. In humans, mutations in A-type lamins give rise to diseases that exhibit tissue-specific defects, such as Emery-Dreifuss muscular dystrophy. Drosophila is being used as a model to determine tissue-specific functions of A-type lamins in development, with implications for understanding human disease mechanisms. The GAL4-UAS system was used to express wild-type and mutant forms of Lamin C (the presumed Drosophila A-type lamin), in an otherwise wild-type background. Larval muscle-specific expression of wild type Drosophila Lamin C caused no overt phenotype. By contrast, larval muscle-specific expression of a truncated form of Lamin C lacking the N-terminal head (Lamin C DeltaN) caused muscle defects and semi-lethality, with adult 'escapers' possessing malformed legs. The leg defects were due to a lack of larval muscle function and alterations in hormone-regulated gene expression. The consequences of Lamin C association at a gene were tested directly by targeting a Lamin C DNA-binding domain fusion protein upstream of a reporter gene. Association of Lamin C correlated with localization of the reporter gene at the nuclear periphery and gene repression. These data demonstrate connections among the Drosophila A-type lamin, hormone-induced gene expression and muscle function.
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Affiliation(s)
- George Dialynas
- Department of Biochemistry, University of Iowa, Iowa City, IA 52241, USA
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238
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Göb E, Schmitt J, Benavente R, Alsheimer M. Mammalian sperm head formation involves different polarization of two novel LINC complexes. PLoS One 2010; 5:e12072. [PMID: 20711465 PMCID: PMC2919408 DOI: 10.1371/journal.pone.0012072] [Citation(s) in RCA: 113] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2010] [Accepted: 07/14/2010] [Indexed: 11/18/2022] Open
Abstract
BACKGROUND LINC complexes are nuclear envelope bridging protein structures formed by interaction of SUN and KASH proteins. They physically connect the nucleus with the peripheral cytoskeleton and are critically involved in a variety of dynamic processes, such as nuclear anchorage, movement and positioning and meiotic chromosome dynamics. Moreover, they are shown to be essential for maintaining nuclear shape. FINDINGS Based on detailed expression analysis and biochemical approaches, we show here that during mouse sperm development, a terminal cell differentiation process characterized by profound morphogenic restructuring, two novel distinctive LINC complexes are established. They consist either of spermiogenesis-specific Sun3 and Nesprin1 or Sun1eta, a novel non-nuclear Sun1 isoform, and Nesprin3. We could find that these two LINC complexes specifically polarize to opposite spermatid poles likely linking to sperm-specific cytoskeletal structures. Although, as shown in co-transfection/immunoprecipitation experiments, SUN proteins appear to arbitrarily interact with various KASH partners, our study demonstrates that they actually are able to confine their binding to form distinct LINC complexes. CONCLUSIONS Formation of the mammalian sperm head involves assembly and different polarization of two novel spermiogenesis-specific LINC complexes. Together, our findings suggest that theses LINC complexes connect the differentiating spermatid nucleus to surrounding cytoskeletal structures to enable its well-directed shaping and elongation, which in turn is a critical parameter for male fertility.
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Affiliation(s)
- Eva Göb
- Department of Cell and Developmental Biology, Biocenter, University of Würzburg, Würzburg, Germany
| | - Johannes Schmitt
- Department of Cell and Developmental Biology, Biocenter, University of Würzburg, Würzburg, Germany
| | - Ricardo Benavente
- Department of Cell and Developmental Biology, Biocenter, University of Würzburg, Würzburg, Germany
| | - Manfred Alsheimer
- Department of Cell and Developmental Biology, Biocenter, University of Würzburg, Würzburg, Germany
- * E-mail:
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239
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A classical NLS and the SUN domain contribute to the targeting of SUN2 to the inner nuclear membrane. EMBO J 2010; 29:2262-75. [PMID: 20551905 DOI: 10.1038/emboj.2010.119] [Citation(s) in RCA: 74] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2010] [Accepted: 05/14/2010] [Indexed: 01/26/2023] Open
Abstract
Integral membrane proteins of the inner nuclear membrane (INM) are inserted into the endoplasmic reticulum membrane during their biogenesis and are then targeted to their final destination. We have used human SUN2 to delineate features that are required for INM targeting and have identified multiple elements that collectively contribute to the efficient localization of SUN2 to the nuclear envelope (NE). One such targeting element is a classical nuclear localization signal (cNLS) present in the N-terminal, nucleoplasmic domain of SUN2. A second motif proximal to the cNLS is a cluster of arginines that serves coatomer-mediated retrieval of SUN2 from the Golgi. Unexpectedly, also the C-terminal, lumenal SUN domain of SUN2 supports NE localization, showing that targeting elements are not limited to cytoplasmic or transmembrane domains of INM proteins. Together, SUN2 represents the first mammalian INM protein relying on a functional cNLS, a Golgi retrieval signal and a perinuclear domain to mediate targeting to the INM.
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240
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Chalut KJ, Kulangara K, Giacomelli MG, Wax A, Leong KW. Deformation of stem cell nuclei by nanotopographical cues. SOFT MATTER 2010; 6:1675-1681. [PMID: 21297875 PMCID: PMC3032404 DOI: 10.1039/b921206j] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
Cells sense cues in their surrounding microenvironment. These cues are converted into intracellular signals and transduced to the nucleus in order for the cell to respond and adapt its function. Within the nucleus, structural changes occur that ultimately lead to changes in the gene expression. In this study, we explore the structural changes of the nucleus of human mesenchymal stem cells as an effect of topographical cues. We use a controlled nanotopography to drive shape changes to the cell nucleus, and measure the changes with both fluorescence microscopy and a novel light scattering technique. The nucleus changes shape dramatically in response to the nanotopography, and in a manner dependent on the mechanical properties of the substrate. The kinetics of the nuclear deformation follows an unexpected trajectory. As opposed to a gradual shape change in response to the topography, once the cytoskeleton attains an aligned and elongation morphology on the time scale of several hours, the nucleus changes shape rapidly and intensely.
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Affiliation(s)
- Kevin J Chalut
- Department of Physics, University of Cambridge, Cambridge, CB3 0HE, UK
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241
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Abstract
A- and B-type lamins are the major intermediate filaments of the nucleus. Lamins engage in a plethora of stable and transient interactions, near the inner nuclear membrane and throughout the nucleus. Lamin-binding proteins serve an amazingly diverse range of functions. Numerous inner-membrane proteins help anchor lamin filaments to the nuclear envelope, serving as part of the nuclear "lamina" network that is essential for nuclear architecture and integrity. Certain lamin-binding proteins of the inner membrane bind partners in the outer membrane and mechanically link lamins to the cytoskeleton. Inside the nucleus, lamin-binding proteins appear to serve as the "adaptors" by which the lamina organizes chromatin, influences gene expression and epigenetic regulation, and modulates signaling pathways. Transient interactions of lamins with key components of the transcription and replication machinery may provide an additional level of regulation or support to these essential events.
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Affiliation(s)
- Katherine L Wilson
- Department of Cell Biology, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA
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242
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Mazumder A, Shivashankar GV. Emergence of a prestressed eukaryotic nucleus during cellular differentiation and development. J R Soc Interface 2010; 7 Suppl 3:S321-30. [PMID: 20356876 DOI: 10.1098/rsif.2010.0039.focus] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
Nuclear shape and size are emerging as mechanistic regulators of genome function. Yet, the coupling between chromatin assembly and various nuclear and cytoplasmic scaffolds is poorly understood. The present work explores the structural organization of a prestressed nucleus in a variety of cellular systems ranging from cells in culture to those in an organism. A combination of laser ablation and cellular perturbations was used to decipher the dynamic nature of the nucleo-cytoplasmic contacts. In primary mouse embryonic fibroblasts, ablation of heterochromatin nodes caused an anisotropic shrinkage of the nucleus. Depolymerization of actin and microtubules, and inhibition of myosin motors, resulted in the differential stresses that these cytoplasmic systems exert on the nucleus. The onset of nuclear prestress was then mapped in two contexts--first, in the differentiation of embryonic stem cells, where signatures of prestress appeared with differentiation; second, at an organism level, where nuclear or cytoplasmic laser ablations of cells in the early Drosophila embryo induced a collapse of the nucleus only after cellularization. We thus show that the interplay of physical connections bridging the nucleus with the cytoplasm governs the size and shape of a prestressed eukaryotic nucleus.
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Affiliation(s)
- Aprotim Mazumder
- National Centre for Biological Sciences, Tata Institute of Fundamental Research, GKVK Campus, Bellary Road, Bangalore 560065, India
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243
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Abstract
The giant isoforms of nesprins 1 and 2 are emerging as important players in cellular organization, particularly in the positioning of nuclei, and possibly other organelles, within the cytoplasm. The experimental evidence suggests that nesprins also occur at the inner nuclear membrane, where they interact with the nuclear lamina. In this paper, we consider whether this is consistent with current ideas about nesprin anchorage and about mechanisms for nuclear import of membrane proteins.
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244
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Fridolfsson HN, Ly N, Meyerzon M, Starr DA. UNC-83 coordinates kinesin-1 and dynein activities at the nuclear envelope during nuclear migration. Dev Biol 2010; 338:237-50. [PMID: 20005871 PMCID: PMC2826220 DOI: 10.1016/j.ydbio.2009.12.004] [Citation(s) in RCA: 112] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2009] [Revised: 12/04/2009] [Accepted: 12/04/2009] [Indexed: 11/19/2022]
Abstract
Nuclei migrate during many events, including fertilization, establishment of polarity, differentiation, and cell division. The Caenorhabditis elegans KASH protein UNC-83 localizes to the outer nuclear membrane where it recruits kinesin-1 to provide the major motor activity required for nuclear migration in embryonic hyp7 cells. Here we show that UNC-83 also recruits two dynein-regulating complexes to the cytoplasmic face of the nucleus that play a regulatory role. One consists of the NudE homolog NUD-2 and the NudF/Lis1/Pac1 homolog LIS-1, and the other includes dynein light chain DLC-1, the BicaudalD homolog BICD-1, and the Egalitarian homologue EGAL-1. Genetic disruption of any member of these two complexes caused nuclear migration defects that were enhanced in some double mutant animals, suggesting that BICD-1 and EGAL-1 function in parallel to NUD-2. Dynein heavy chain mutant animals also had a nuclear migration defect, suggesting these complexes function through dynein. Deletion analysis indicated that independent domains of UNC-83 interact with kinesin and dynein. These data suggest a model where UNC-83 acts as the cargo-specific adaptor between the outer nuclear membrane and the microtubule motors kinesin-1 and dynein. Kinesin-1 functions as the major force generator during nuclear migration, while dynein is involved in regulation of bidirectional transport of the nucleus.
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Affiliation(s)
- Heidi N. Fridolfsson
- Department of Molecular and Cellular Biology, University of California, Davis, CA 95616
| | - Nina Ly
- Department of Molecular and Cellular Biology, University of California, Davis, CA 95616
| | - Marina Meyerzon
- Department of Molecular and Cellular Biology, University of California, Davis, CA 95616
| | - Daniel A. Starr
- Department of Molecular and Cellular Biology, University of California, Davis, CA 95616
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245
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Haque F, Mazzeo D, Patel JT, Smallwood DT, Ellis JA, Shanahan CM, Shackleton S. Mammalian SUN protein interaction networks at the inner nuclear membrane and their role in laminopathy disease processes. J Biol Chem 2010; 285:3487-98. [PMID: 19933576 PMCID: PMC2823409 DOI: 10.1074/jbc.m109.071910] [Citation(s) in RCA: 230] [Impact Index Per Article: 15.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2009] [Revised: 11/20/2009] [Indexed: 11/06/2022] Open
Abstract
The nuclear envelope (NE) LINC complex, in mammals comprised of SUN domain and nesprin proteins, provides a direct connection between the nuclear lamina and the cytoskeleton, which contributes to nuclear positioning and cellular rigidity. SUN1 and SUN2 interact with lamin A, but lamin A is only required for NE localization of SUN2, and it remains unclear how SUN1 is anchored. Here, we identify emerin and short nesprin-2 isoforms as novel nucleoplasmic binding partners of SUN1/2. These have overlapping binding sites distinct from the lamin A binding site. However, we demonstrate that tight association of SUN1 with the nuclear lamina depends upon a short motif within residues 209-228, a region that does not interact significantly with known SUN1 binding partners. Moreover, SUN1 localizes correctly in cells lacking emerin. Importantly then, the major determinant of SUN1 NE localization has yet to be identified. We further find that a subset of lamin A mutations, associated with laminopathies Emery-Dreifuss muscular dystrophy (EDMD) and Hutchinson-Gilford progeria syndrome (HGPS), disrupt lamin A interaction with SUN1 and SUN2. Despite this, NE localization of SUN1 and SUN2 is not impaired in cell lines from either class of patients. Intriguingly, SUN1 expression at the NE is instead enhanced in a significant proportion of HGPS but not EDMD cells and strongly correlates with pre-lamin A accumulation due to preferential interaction of SUN1 with pre-lamin A. We propose that these different perturbations in lamin A-SUN protein interactions may underlie the opposing effects of EDMD and HGPS mutations on nuclear and cellular mechanics.
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Affiliation(s)
- Farhana Haque
- From the Department of Biochemistry, University of Leicester, Leicester LE1 9HN
| | - Daniela Mazzeo
- From the Department of Biochemistry, University of Leicester, Leicester LE1 9HN
| | - Jennifer T. Patel
- From the Department of Biochemistry, University of Leicester, Leicester LE1 9HN
| | - Dawn T. Smallwood
- From the Department of Biochemistry, University of Leicester, Leicester LE1 9HN
| | - Juliet A. Ellis
- The Randall Division of Cell and Molecular Biophysics, Kings College, London SE1 1UL, and
| | - Catherine M. Shanahan
- the Cardiovascular Division, James Black Centre, Kings College London, 125 Coldharbour Lane, London SE5 9NU, United Kingdom
| | - Sue Shackleton
- From the Department of Biochemistry, University of Leicester, Leicester LE1 9HN
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246
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Warren DT, Tajsic T, Mellad JA, Searles R, Zhang Q, Shanahan CM. Novel nuclear nesprin-2 variants tether active extracellular signal-regulated MAPK1 and MAPK2 at promyelocytic leukemia protein nuclear bodies and act to regulate smooth muscle cell proliferation. J Biol Chem 2010; 285:1311-20. [PMID: 19861416 PMCID: PMC2801258 DOI: 10.1074/jbc.m109.032557] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2009] [Revised: 10/05/2009] [Indexed: 11/06/2022] Open
Abstract
Nuclear and cytoplasmic scaffold proteins have been shown to be essential for temporal and spatial organization, as well as the fidelity, of MAPK signaling pathways. In this study we show that nesprin-2 is a novel extracellular signal-regulated MAPK1 and 2 (ERK1/2) scaffold protein that serves to regulate nuclear signaling by tethering these kinases at promyelocytic leukemia protein nuclear bodies (PML NBs). Using immunofluorescence microscopy, GST pull-down and immunoprecipitation, we show that nesprin-2, ERK1/2, and PML colocalize and bind to form a nuclear complex. Interference of nesprin-2 function, by either siRNA-mediated knockdown or overexpression of a dominant negative nesprin-2 fragment, augmented ERK1/2 nuclear signaling shown by increased SP1 activity and ELK1 phosphorylation. The functional outcome of nesprin-2 disruption and the resultant sustained ERK1/2 signal was increased proliferation. Importantly, these activities were not induced by previously identified nuclear envelope (NE)-targeted nesprin-2 isoforms but rather were mediated by novel nuclear isoforms that lacked the KASH domain. Taken together, this study suggests that nesprin-2 is a novel intranuclear scaffold, essential for nuclear ERK1/2 signaling fidelity and cell cycle progression.
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Affiliation(s)
- Derek T Warren
- British Heart Foundation Centre, Division of Cardiovascular Medicine, King's College London, London SE5 9NU, United Kingdom.
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247
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Méjat A, Misteli T. LINC complexes in health and disease. Nucleus 2010; 1:40-52. [PMID: 21327104 PMCID: PMC3035119 DOI: 10.4161/nucl.1.1.10530] [Citation(s) in RCA: 148] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2009] [Revised: 11/04/2009] [Accepted: 11/05/2009] [Indexed: 11/19/2022] Open
Abstract
The cell nucleus communicates with the rest of the cell via nucleo/cytoplasmic transport of proteins and RNA through the nuclear pores. Direct mechanical links between the nucleus and the cytoplasm have recently emerged in the form of LINC (Linkers of the nucleoskeleton to the cytoskeleton) protein complexes. A LINC complex consists of four components. At its core are an inner nuclear membrane (INM) transmembrane protein and an outer nuclear membrane (ONM) transmembrane protein which physically interact with each other in the lumen of the NE. The INM LINC component interacts on the nucleoplasmic side with either the lamina or with an INM-associated protein. The ONM LINC component on the other hand contacts on the cytoplasmatic side a component of the cytoskeleton. This review highlights the components of LINC complexes and their emerging roles in mechanotransduction, nuclear migration, chromosome positioning, signaling, meiosis, cytoskeletal organization and human disease.
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Affiliation(s)
- Alexandre Méjat
- National Cancer Institute, National Institutes of Health, Bethesda, MD, USA.
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248
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Graumann K, Runions J, Evans DE. Characterization of SUN-domain proteins at the higher plant nuclear envelope. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2010; 61:134-44. [PMID: 19807882 DOI: 10.1111/j.1365-313x.2009.04038.x] [Citation(s) in RCA: 128] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/07/2023]
Abstract
Sad1/UNC-84 (SUN)-domain proteins are inner nuclear membrane (INM) proteins that are part of bridging complexes linking cytoskeletal elements with the nucleoskeleton, and have been shown to be conserved in non-plant systems. In this paper, we report the presence of members of this family in the plant kingdom, and investigate the two Arabidopsis SUN-domain proteins, AtSUN1 and AtSUN2. Our results indicate they contain the highly conserved C-terminal SUN domain, and share similar structural features with animal and fungal SUN-domain proteins including a functional coiled-coil domain and nuclear localization signal. Both are expressed in various tissues with AtSUN2 expression levels relatively low but upregulated in proliferating tissues. Further, we found AtSUN1 and AtSUN2 expressed as fluorescent protein fusions, to localize to and show low mobility in the nuclear envelope (NE), particularly in the INM. Deletion of various functional domains including the N terminus and coiled-coil domain affect the localization and increase the mobility of AtSUN1 and AtSUN2. Finally, we present evidence that AtSUN1 and AtSUN2 are present as homomers and heteromers in vivo, and that the coiled-coil domains are required for this. The study provides evidence suggesting the existence of cytoskeletal-nucleoskeletal bridging complexes at the plant NE.
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Affiliation(s)
- Katja Graumann
- School of Life Sciences, Oxford Brookes University, Headington Campus, Oxford OX3 0BP, UK
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249
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Mazumder A, Roopa T, Kumar A, Iyer KV, Ramdas NM, Shivashankar GV. Prestressed nuclear organization in living cells. Methods Cell Biol 2010; 98:221-39. [PMID: 20816237 DOI: 10.1016/s0091-679x(10)98010-2] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
The nucleus is maintained in a prestressed state within eukaryotic cells, stabilized mechanically by chromatin structure and other nuclear components on its inside, and cytoskeletal components on its outside. Nuclear architecture is emerging to be critical to the governance of chromatin assembly, regulation of genome function and cellular homeostasis. Elucidating the prestressed organization of the nucleus is thus important to understand how the nuclear architecture impinges on its function. In this chapter, various chemical and mechanical methods have been described to probe the prestressed organization of the nucleus.
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Affiliation(s)
- Aprotim Mazumder
- National Centre for Biological Sciences, Tata Institute of Fundamental Research, Bellary Road, Bangalore 560065, India
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250
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Puckelwartz MJ, Kessler EJ, Kim G, Dewitt MM, Zhang Y, Earley JU, Depreux FFS, Holaska J, Mewborn SK, Pytel P, McNally EM. Nesprin-1 mutations in human and murine cardiomyopathy. J Mol Cell Cardiol 2009; 48:600-8. [PMID: 19944109 DOI: 10.1016/j.yjmcc.2009.11.006] [Citation(s) in RCA: 110] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/29/2009] [Revised: 11/10/2009] [Accepted: 11/11/2009] [Indexed: 12/28/2022]
Abstract
Mutations in LMNA, the gene encoding the nuclear membrane proteins, lamins A and C, produce cardiac and muscle disease. In the heart, these autosomal dominant LMNA mutations lead to cardiomyopathy frequently associated with cardiac conduction system disease. Herein, we describe a patient with the R374H missense variant in nesprin-1alpha, a protein that binds lamin A/C. This individual developed dilated cardiomyopathy requiring cardiac transplantation. Fibroblasts from this individual had increased expression of nesprin-1alpha and lamins A and C, indicating changes in the nuclear membrane complex. We characterized mice lacking the carboxy-terminus of nesprin-1 since this model expresses nesprin-1 without its carboxy-terminal KASH domain. These Delta/DeltaKASH mice have a normally assembled but dysfunctional nuclear membrane complex and provide a model for nesprin-1 mutations. We found that Delta/DeltaKASH mice develop cardiomyopathy with associated cardiac conduction system disease. Older mutant animals were found to have elongated P wave duration, elevated atrial and ventricular effective refractory periods indicating conduction defects in the myocardium, and reduced fractional shortening. Cardiomyocyte nuclei were found to be elongated with reduced heterochromatin in the Delta/DeltaKASH hearts. These findings mirror what has been described from lamin A/C gene mutations and reinforce the importance of an intact nuclear membrane complex for a normally functioning heart.
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