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Huang ZP, Young Seok H, Zhou B, Chen J, Chen JF, Tao Y, Pu WT, Wang DZ. CIP, a cardiac Isl1-interacting protein, represses cardiomyocyte hypertrophy. Circ Res 2012; 110:818-30. [PMID: 22343712 DOI: 10.1161/circresaha.111.259663] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
RATIONALE Mammalian heart has minimal regenerative capacity. In response to mechanical or pathological stress, the heart undergoes cardiac remodeling. Pressure and volume overload in the heart cause increased size (hypertrophic growth) of cardiomyocytes. Whereas the regulatory pathways that activate cardiac hypertrophy have been well-established, the molecular events that inhibit or repress cardiac hypertrophy are less known. OBJECTIVE To identify and investigate novel regulators that modulate cardiac hypertrophy. METHODS AND RESULTS Here, we report the identification, characterization, and functional examination of a novel cardiac Isl1-interacting protein (CIP). CIP was identified from a bioinformatic search for novel cardiac-expressed genes in mouse embryonic hearts. CIP encodes a nuclear protein without recognizable motifs. Northern blotting, in situ hybridization, and reporter gene tracing demonstrated that CIP is highly expressed in cardiomyocytes of developing and adult hearts. Yeast two-hybrid screening identified Isl1, a LIM/homeodomain transcription factor essential for the specification of cardiac progenitor cells in the second heart field, as a cofactor of CIP. CIP directly interacted with Isl1, and we mapped the domains of these two proteins, which mediate their interaction. We show that CIP represses the transcriptional activity of Isl1 in the activation of the myocyte enhancer factor 2C. The expression of CIP was dramatically reduced in hypertrophic cardiomyocytes. Most importantly, overexpression of CIP repressed agonist-induced cardiomyocyte hypertrophy. CONCLUSIONS Our studies therefore identify CIP as a novel regulator of cardiac hypertrophy.
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Affiliation(s)
- Zhan-Peng Huang
- Department of Cardiology, Children's Hospital Boston, Harvard Medical School, MA 02115, USA
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Inner nuclear membrane proteins: impact on human disease. Chromosoma 2012; 121:153-67. [DOI: 10.1007/s00412-012-0360-2] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2011] [Revised: 01/02/2012] [Accepted: 01/03/2012] [Indexed: 02/01/2023]
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53
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54
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Lamins, laminopathies and disease mechanisms: Possible role for proteasomal degradation of key regulatory proteins. J Biosci 2011; 36:471-9. [DOI: 10.1007/s12038-011-9085-2] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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55
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Affiliation(s)
- Kris Noel Dahl
- Department of Biomedical Engineering, Carnegie Mellon University, 5000 Forbes Avenue, Pittsburgh, PA 15213, USA.
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Abstract
Over the past fifteen years, our understanding of the molecular mechanisms underlying human disease has flourished in large part due to the discovery of gene mutations linked with membrane ion channels and transporters. In fact, ion channel defects ("channelopathies" - the focus of this review series) have been associated with a spectrum of serious human disease phenotypes including cystic fibrosis, cardiac arrhythmia, diabetes, skeletal muscle defects, and neurological disorders. However, we now know that human disease, particularly excitable cell disease, may be caused by defects in non-ion channel polypeptides including in cellular components residing well beneath the plasma membrane. For example, over the past few years, a new class of potentially fatal cardiac arrhythmias has been linked with cytoplasmic proteins that include sub-membrane adapters such as ankyrin-B (ANK2), ankyrin-G (ANK3), and alpha-1 syntrophin, membrane coat proteins including caveolin-3 (CAV3), signaling platforms including yotiao (AKAP9), and cardiac enzymes (GPD1L). The focus of this review is to detail the exciting role of lamins, yet another class of gene products that have provided elegant new insight into human disease.
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Ahmady E, Deeke SA, Rabaa S, Kouri L, Kenney L, Stewart AFR, Burgon PG. Identification of a novel muscle A-type lamin-interacting protein (MLIP). J Biol Chem 2011; 286:19702-13. [PMID: 21498514 PMCID: PMC3103349 DOI: 10.1074/jbc.m110.165548] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
Mutations in the A-type lamin (LMNA) gene are associated with age-associated degenerative disorders of mesenchymal tissues, such as dilated cardiomyopathy, Emery-Dreifuss muscular dystrophy, and limb-girdle muscular dystrophy. The molecular mechanisms that connect mutations in LMNA with different human diseases are poorly understood. Here, we report the identification of a Muscle-enriched A-type Lamin-interacting Protein, MLIP (C6orf142 and 2310046A06rik), a unique single copy gene that is an innovation of amniotes (reptiles, birds, and mammals). MLIP encodes alternatively spliced variants (23-57 kDa) and possesses several novel structural motifs not found in other proteins. MLIP is expressed ubiquitously and most abundantly in heart, skeletal, and smooth muscle. MLIP interacts directly and co-localizes with lamin A and C in the nuclear envelope. MLIP also co-localizes with promyelocytic leukemia (PML) bodies within the nucleus. PML, like MLIP, is only found in amniotes, suggesting that a functional link between the nuclear envelope and PML bodies may exist through MLIP. Down-regulation of lamin A/C expression by shRNA results in the up-regulation and mislocalization of MLIP. Given that MLIP is expressed most highly in striated and smooth muscle, it is likely to contribute to the mesenchymal phenotypes of laminopathies.
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Affiliation(s)
- Elmira Ahmady
- University of Ottawa Heart Institute, Ottawa, Ontario, Canada
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Koshimizu E, Imamura S, Qi J, Toure J, Valdez DM, Carr CE, Hanai JI, Kishi S. Embryonic senescence and laminopathies in a progeroid zebrafish model. PLoS One 2011; 6:e17688. [PMID: 21479207 PMCID: PMC3068137 DOI: 10.1371/journal.pone.0017688] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2010] [Accepted: 02/09/2011] [Indexed: 11/18/2022] Open
Abstract
Background Mutations that disrupt the conversion of prelamin A to mature lamin A cause the rare genetic disorder Hutchinson-Gilford progeria syndrome and a group of laminopathies. Our understanding of how A-type lamins function in vivo during early vertebrate development through aging remains limited, and would benefit from a suitable experimental model. The zebrafish has proven to be a tractable model organism for studying both development and aging at the molecular genetic level. Zebrafish show an array of senescence symptoms resembling those in humans, which can be targeted to specific aging pathways conserved in vertebrates. However, no zebrafish models bearing human premature senescence currently exist. Principal Findings We describe the induction of embryonic senescence and laminopathies in zebrafish harboring disturbed expressions of the lamin A gene (LMNA). Impairments in these fish arise in the skin, muscle and adipose tissue, and sometimes in the cartilage. Reduced function of lamin A/C by translational blocking of the LMNA gene induced apoptosis, cell-cycle arrest, and craniofacial abnormalities/cartilage defects. By contrast, induced cryptic splicing of LMNA, which generates the deletion of 8 amino acid residues lamin A (zlamin A-Δ8), showed embryonic senescence and S-phase accumulation/arrest. Interestingly, the abnormal muscle and lipodystrophic phenotypes were common in both cases. Hence, both decrease-of-function of lamin A/C and gain-of-function of aberrant lamin A protein induced laminopathies that are associated with mesenchymal cell lineages during zebrafish early development. Visualization of individual cells expressing zebrafish progerin (zProgerin/zlamin A-Δ37) fused to green fluorescent protein further revealed misshapen nuclear membrane. A farnesyltransferase inhibitor reduced these nuclear abnormalities and significantly prevented embryonic senescence and muscle fiber damage induced by zProgerin. Importantly, the adult Progerin fish survived and remained fertile with relatively mild phenotypes only, but had shortened lifespan with obvious distortion of body shape. Conclusion We generated new zebrafish models for a human premature aging disorder, and further demonstrated the utility for studying laminopathies. Premature aging could also be modeled in zebrafish embryos. This genetic model may thus provide a new platform for future drug screening as well as genetic analyses aimed at identifying modifier genes that influence not only progeria and laminopathies but also other age-associated human diseases common in vertebrates.
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Affiliation(s)
- Eriko Koshimizu
- Department of Ophthalmology, Harvard Medical School, Boston, Massachusetts, United States of America
- Graduate School of Marine Science and Technology, University of Marine Science and Technology, Tokyo, Japan
| | - Shintaro Imamura
- Department of Ophthalmology, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Jie Qi
- Department of Ophthalmology, Harvard Medical School, Boston, Massachusetts, United States of America
- Department of Metabolism and Aging, The Scripps Research Institute, Jupiter, Florida, United States of America
| | - Jamal Toure
- Department of Ophthalmology, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Delgado M. Valdez
- Department of Metabolism and Aging, The Scripps Research Institute, Jupiter, Florida, United States of America
| | - Christopher E. Carr
- Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States of America
| | - Jun-ichi Hanai
- Division of Nephrology, Interdisciplinary Medicine and Biotechnology, Department of Medicine, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Shuji Kishi
- Department of Ophthalmology, Harvard Medical School, Boston, Massachusetts, United States of America
- Department of Metabolism and Aging, The Scripps Research Institute, Jupiter, Florida, United States of America
- * E-mail:
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Liang WC, Mitsuhashi H, Keduka E, Nonaka I, Noguchi S, Nishino I, Hayashi YK. TMEM43 mutations in emery-dreifuss muscular dystrophy-related myopathy. Ann Neurol 2011; 69:1005-13. [DOI: 10.1002/ana.22338] [Citation(s) in RCA: 94] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2010] [Revised: 10/25/2010] [Accepted: 11/12/2010] [Indexed: 01/18/2023]
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Abstract
Emery-Dreifuss muscular dystrophy (EDMD) is a progressive muscle-wasting disorder defined by early contractures of the Achilles tendon, spine, and elbows. EDMD is also distinctive for its association with defects of the cardiac conduction system that can result in sudden death. It can be inherited in an X-linked, autosomal dominant, or autosomal recessive fashion and is caused by mutations in proteins of the nuclear membrane. Mutations in the EMD gene, which encodes emerin, a transmembrane protein found at the inner nuclear membrane, are responsible for X-linked EDMD. The most common etiology of autosomal dominant EDMD is an LMNA gene mutation; LMNA encodes the intermediate filament protein lamins A and C, which constitute the major scaffolding protein of the inner nuclear membrane. Murine models of LMNA gene mutations have helped to identify different mechanisms of disease. Loss of LMNA function leads to nuclear fragility as well as other defects, such as abnormal nuclear function. Additional genes encoding nuclear membrane proteins such as SYNE1 and SYNE2 have also been implicated in EDMD, and in some cases their importance for cardiac and muscle function has been supported by animal modeling.
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Małek ŁA, Labib S, Mazurkiewicz Ł, Saj M, Płoski R, Tesson F, Bilińska ZT. A new c.1621 C>G, p.R541G lamin A/C mutation in a family with DCM and regional wall motion abnormalities (akinesis/dyskinesis): genotype–phenotype correlation. J Hum Genet 2010; 56:83-6. [DOI: 10.1038/jhg.2010.137] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Hernandez L, Roux KJ, Wong ESM, Mounkes LC, Mutalif R, Navasankari R, Rai B, Cool S, Jeong JW, Wang H, Lee HS, Kozlov S, Grunert M, Keeble T, Jones CM, Meta MD, Young SG, Daar IO, Burke B, Perantoni AO, Stewart CL. Functional coupling between the extracellular matrix and nuclear lamina by Wnt signaling in progeria. Dev Cell 2010; 19:413-25. [PMID: 20833363 PMCID: PMC2953243 DOI: 10.1016/j.devcel.2010.08.013] [Citation(s) in RCA: 141] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2009] [Revised: 07/07/2010] [Accepted: 08/23/2010] [Indexed: 12/14/2022]
Abstract
The segmental premature aging disease Hutchinson-Gilford Progeria (HGPS) is caused by a truncated and farnesylated form of Lamin A. In a mouse model for HGPS, a similar Lamin A variant causes the proliferative arrest and death of postnatal, but not embryonic, fibroblasts. Arrest is due to an inability to produce a functional extracellular matrix (ECM), because growth on normal ECM rescues proliferation. The defects are associated with inhibition of canonical Wnt signaling, due to reduced nuclear localization and transcriptional activity of Lef1, but not Tcf4, in both mouse and human progeric cells. Defective Wnt signaling, affecting ECM synthesis, may be critical to the etiology of HGPS because mice exhibit skeletal defects and apoptosis in major blood vessels proximal to the heart. These results establish a functional link between the nuclear envelope/lamina and the cell surface/ECM and may provide insights into the role of Wnt signaling and the ECM in aging.
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Affiliation(s)
- Lidia Hernandez
- Cancer and Developmental Biology Laboratory, NCI, Frederick, MD 21702
- Molecular Signaling Section, Medical Oncology Branch, Center for Cancer Research NCI, Bethesda, MD 20892
| | - Kyle J. Roux
- Dept. of Anatomy and Cell Biology, University of Florida College of Medicine, Gainesville, FL 32606
| | | | - Leslie C. Mounkes
- Cancer and Developmental Biology Laboratory, NCI, Frederick, MD 21702
| | - Rafidah Mutalif
- Institute of Medical Biology, Immunos, 8A Biomedical Grove, Singapore 138648
| | - Raju Navasankari
- Institute of Medical Biology, Immunos, 8A Biomedical Grove, Singapore 138648
| | - Bina Rai
- Institute of Medical Biology, Immunos, 8A Biomedical Grove, Singapore 138648
| | - Simon Cool
- Institute of Medical Biology, Immunos, 8A Biomedical Grove, Singapore 138648
| | - Jae-Wook Jeong
- Department of Molecular and Cellular Biology, Baylor College of Medicine, Houston, TX 77030
| | - Honghe Wang
- Cancer and Developmental Biology Laboratory, NCI, Frederick, MD 21702
| | - Hyun-Shik Lee
- Laboratory of Cell and Developmental Signaling, NCI, Frederick, MD 21702
| | - Serguei Kozlov
- Cancer and Developmental Biology Laboratory, NCI, Frederick, MD 21702
| | - Martin Grunert
- Institute of Medical Biology, Immunos, 8A Biomedical Grove, Singapore 138648
| | - Thomas Keeble
- Institute of Medical Biology, Immunos, 8A Biomedical Grove, Singapore 138648
| | - C. Michael Jones
- Institute of Medical Biology, Immunos, 8A Biomedical Grove, Singapore 138648
| | - Margarita D. Meta
- Dept. of Medicine, David Geffen School of Medicine, University of California, Los Angeles, CA90095
| | - Stephen G. Young
- Dept. of Medicine, David Geffen School of Medicine, University of California, Los Angeles, CA90095
| | - Ira O. Daar
- Laboratory of Cell and Developmental Signaling, NCI, Frederick, MD 21702
| | - Brian Burke
- Dept. of Anatomy and Cell Biology, University of Florida College of Medicine, Gainesville, FL 32606
| | - Alan O. Perantoni
- Cancer and Developmental Biology Laboratory, NCI, Frederick, MD 21702
| | - Colin L. Stewart
- Cancer and Developmental Biology Laboratory, NCI, Frederick, MD 21702
- Institute of Medical Biology, Immunos, 8A Biomedical Grove, Singapore 138648
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Liu Q, Kim DI, Syme J, LuValle P, Burke B, Roux KJ. Dynamics of lamin-A processing following precursor accumulation. PLoS One 2010; 5:e10874. [PMID: 20526372 PMCID: PMC2878336 DOI: 10.1371/journal.pone.0010874] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2010] [Accepted: 05/06/2010] [Indexed: 11/18/2022] Open
Abstract
Lamin A (LaA) is a component of the nuclear lamina, an intermediate filament meshwork that underlies the inner nuclear membrane (INM) of the nuclear envelope (NE). Newly synthesized prelamin A (PreA) undergoes extensive processing involving C-terminal farnesylation followed by proteolysis yielding non-farnesylated mature lamin A. Different inhibitors of these processing events are currently used therapeutically. Hutchinson-Gilford Progeria Syndrome (HGPS) is most commonly caused by mutations leading to an accumulation of a farnesylated LaA isoform, prompting a clinical trial using farnesyltransferase inhibitors (FTI) to reduce this modification. At therapeutic levels, HIV protease inhibitors (PI) can unexpectedly inhibit the final processing step in PreA maturation. We have examined the dynamics of LaA processing and associated cellular effects during PI or FTI treatment and following inhibitor washout. While PI reversibility was rapid, with respect to both LaA maturation and associated cellular phenotype, recovery from FTI treatment was more gradual. FTI reversibility is influenced by both cell type and rate of proliferation. These results suggest a less static lamin network than has previously been observed.
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Affiliation(s)
- Qian Liu
- Department of Histology and Embryology, Shandong University School of Medicine, Jinan, Shandong, China
- Department of Anatomy and Cell Biology, University of Florida, Gainesville, Florida, United States of America
| | - Dae In Kim
- Department of Anatomy and Cell Biology, University of Florida, Gainesville, Florida, United States of America
| | - Janet Syme
- Department of Anatomy and Cell Biology, University of Florida, Gainesville, Florida, United States of America
| | - Phyllis LuValle
- Department of Anatomy and Cell Biology, University of Florida, Gainesville, Florida, United States of America
| | - Brian Burke
- Department of Anatomy and Cell Biology, University of Florida, Gainesville, Florida, United States of America
- Institute of Medical Biology, Immunos, Singapore, Singapore
| | - Kyle J. Roux
- Department of Anatomy and Cell Biology, University of Florida, Gainesville, Florida, United States of America
- * E-mail:
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Chaturvedi P, Parnaik VK. Lamin A rod domain mutants target heterochromatin protein 1alpha and beta for proteasomal degradation by activation of F-box protein, FBXW10. PLoS One 2010; 5:e10620. [PMID: 20498703 PMCID: PMC2869352 DOI: 10.1371/journal.pone.0010620] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2010] [Accepted: 04/20/2010] [Indexed: 11/19/2022] Open
Abstract
BACKGROUND Lamins are major structural proteins of the nucleus and contribute to the organization of various nuclear functions. Mutations in the human lamin A gene cause a number of highly degenerative diseases, collectively termed as laminopathies. Cells expressing lamin mutations exhibit abnormal nuclear morphology and altered heterochromatin organization; however, the mechanisms responsible for these defects are not well understood. METHODOLOGY AND PRINCIPAL FINDINGS The lamin A rod domain mutants G232E, Q294P and R386K are either diffusely distributed or form large aggregates in the nucleoplasm, resulting in aberrant nuclear morphology in various cell types. We examined the effects of these lamin mutants on the distribution of heterochromatin protein 1 (HP1) isoforms. HeLa cells expressing these mutants showed a heterogeneous pattern of HP1alpha and beta depletion but without altering HP1gamma levels. Changes in HP1alpha and beta were not observed in cells expressing wild-type lamin A or mutant R482L, which assembled normally at the nuclear rim. Treatment with proteasomal inhibitors led to restoration of levels of HP1 isoforms and also resulted in stable association of lamin mutants with the nuclear periphery, rim localization of the inner nuclear membrane lamin-binding protein emerin and partial improvement of nuclear morphology. A comparison of the stability of HP1 isoforms indicated that HP1alpha and beta displayed increased turnover and higher basal levels of ubiquitination than HP1gamma. Transcript analysis of components of the ubiquitination pathway showed that a specific F-box protein, FBXW10 was induced several-fold in cells expressing lamin mutants. Importantly, ectopic expression of FBXW10 in HeLa cells led to depletion of HP1alpha and beta without alteration of HP1gamma levels. CONCLUSIONS Mislocalized lamins can induce ubiquitin-mediated proteasomal degradation of certain HP1 isoforms by activation of FBXW10, a member of the F-box family of proteins that is involved in E3 ubiquitin ligase activity.
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Affiliation(s)
| | - Veena K. Parnaik
- Centre for Cellular and Molecular Biology (CSIR), Hyderabad, India
- * E-mail:
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Roblek M, Schüchner S, Huber V, Ollram K, Vlcek-Vesely S, Foisner R, Wehnert M, Ogris E. Monoclonal antibodies specific for disease-associated point-mutants: lamin A/C R453W and R482W. PLoS One 2010; 5:e10604. [PMID: 20498701 PMCID: PMC2869350 DOI: 10.1371/journal.pone.0010604] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2009] [Accepted: 04/11/2010] [Indexed: 12/27/2022] Open
Abstract
BACKGROUND Disease-linked missense mutations can alter a protein's function with fatal consequences for the affected individual. How a single amino acid substitution in a protein affects its properties, is difficult to study in the context of the cellular proteome, because mutant proteins can often not be traced in cells due to the lack of mutation-specific detection tools. Antibodies, however, with their exquisite epitope specificity permit the detection of single amino acid substitutions but are not available for the vast majority of disease-causing mutant proteins. One of the most frequently missense-mutated human genes is the LMNA gene coding for A-type lamins. Mutations in LMNA cause phenotypically heterogenous, mostly autosomal-dominant inherited diseases, termed laminopathies. The molecular mechanisms underlying the phenotypic heterogeneity of laminopathies, however, are not well understood. Hence, the goal of this study was the development of monoclonal antibodies specific for disease-linked point-mutant A-type lamins. METHODOLOGY/PRINCIPAL FINDINGS Using two different approaches of antigen presentation, namely KLH-coupled peptides and the display of a complete protein domain fused to the Hepatitis B virus capsid protein, we developed monoclonal antibodies against two disease-associated lamin A/C mutants. Both antibodies display exquisite specificity for the respective mutant proteins. We show that with the help of these novel antibodies it is now possible for the first time to study specifically the properties of the mutant proteins in primary patient cells in the background of wild-type protein. CONCLUSIONS We report here the development of two point-mutant specific antibodies against A-type lamins. While synthetic peptides may be the prime choice of antigen, our results show that a given target sequence may have to be presented in alternative ways to ensure the induction of a mutant-specific immune response. Point-mutant specific antibodies will represent valuable tools for basic and clinical research on a number of hereditary as well as acquired diseases caused by dominant missense mutations.
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Affiliation(s)
- Marko Roblek
- Department of Medical Biochemistry, Max F. Perutz Laboratories, Medical University of Vienna, Vienna, Austria
| | - Stefan Schüchner
- Department of Medical Biochemistry, Max F. Perutz Laboratories, Medical University of Vienna, Vienna, Austria
| | - Veronika Huber
- Department of Medical Biochemistry, Max F. Perutz Laboratories, Medical University of Vienna, Vienna, Austria
| | - Katrin Ollram
- Department of Medical Biochemistry, Max F. Perutz Laboratories, Medical University of Vienna, Vienna, Austria
| | - Sylvia Vlcek-Vesely
- Department of Medical Biochemistry, Max F. Perutz Laboratories, Medical University of Vienna, Vienna, Austria
| | - Roland Foisner
- Department of Medical Biochemistry, Max F. Perutz Laboratories, Medical University of Vienna, Vienna, Austria
| | - Manfed Wehnert
- Institute of Human Genetics, Ernst-Moritz-Arndt-University, Greifswald, Germany
| | - Egon Ogris
- Department of Medical Biochemistry, Max F. Perutz Laboratories, Medical University of Vienna, Vienna, Austria
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66
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Gurudatta BV, Shashidhara LS, Parnaik VK. Lamin C and chromatin organization in Drosophila. J Genet 2010; 89:37-49. [DOI: 10.1007/s12041-010-0009-y] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
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Cowan J, Li D, Gonzalez-Quintana J, Morales A, Hershberger RE. Morphological analysis of 13 LMNA variants identified in a cohort of 324 unrelated patients with idiopathic or familial dilated cardiomyopathy. CIRCULATION. CARDIOVASCULAR GENETICS 2010; 3:6-14. [PMID: 20160190 PMCID: PMC2908895 DOI: 10.1161/circgenetics.109.905422] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
BACKGROUND Mutations in the LMNA gene, encoding lamins A/C, represent a significant cause of dilated cardiomyopathy. We recently identified 18 protein-altering LMNA variants in a cohort of 324 unrelated patients with dilated cardiomyopathy. However, at least one family member with dilated cardiomyopathy in each of 6 pedigrees lacked the LMNA mutation (nonsegregation), whereas small sizes of 5 additional families precluded definitive determinations of segregation, raising questions regarding contributions by those variants to disease. METHODS AND RESULTS We have consequently expressed, in COS7 cells, GFP-prelamin A (GFPLaA) fusion constructs incorporating the 6 variants in pedigrees with nonsegregation (R101P, A318T, R388H, R399C, S437Hfsx1, and R654X), the 4 variants in pedigrees with unknown segregation (R89L, R166P [in 2 families], I210S, R471H), and 3 additional missense variants (R190Q, E203K, and L215P) that segregated with disease. Confocal immunofluorescence microscopy was used to characterize GFP-lamin A localization and nuclear morphology. Abnormal phenotypes were observed for 10 of 13 (77%) variants (R89L, R101P, R166P, R190Q, E203K, I210S, L215P, R388H, S437Hfsx1, and R654X), including 4 of 6 showing nonsegregation and 3 of 4 with uncertain segregation. All 7 variants affecting coil 1B and the lamin A-only mutation, R654X, exhibited membrane-bound GFP-lamin A aggregates and nuclear shape abnormalities. Unexpectedly, R388H largely restricted GFP-lamin A to the cytoplasm. Equally unexpected were unique streaked aggregates with S437Hfsx1 and giant aggregates with both S437Hfsx1 and R654X. CONCLUSIONS This work expands the recognized spectrum of lamin A localization abnormalities in dilated cardiomyopathy. It also provides evidence supporting pathogenicity of 10 of 13 tested LMNA variants, including some with uncertain or nonsegregation.
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Affiliation(s)
- Jason Cowan
- Cardiovascular Division, Department of Medicine, University of Miami Miller School of Medicine, Miami, FL 33136, USA
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Dauer WT, Worman HJ. The nuclear envelope as a signaling node in development and disease. Dev Cell 2009; 17:626-38. [PMID: 19922868 DOI: 10.1016/j.devcel.2009.10.016] [Citation(s) in RCA: 185] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
The development of a membrane-bound structure separating DNA from other cellular components was the epochal evolutionary event that gave rise to eukaryotes, possibly occurring up to 2 billion years ago. Yet, this view of the nuclear envelope as a physical barrier greatly underestimates its fundamental impact on cellular organization and complexity, much of which is only beginning to be understood. Indeed, alterations of nuclear envelope structure and protein composition are essential to many aspects of metazoan development and cellular differentiation. Mutations in genes encoding nuclear envelope proteins cause a fascinating array of diseases referred to as "nuclear envelopathies" or "laminopathies" that affect different tissues and organ systems. We review recent work on the nuclear envelope, including insights derived from the study of nuclear envelopathies. These studies are uncovering new functions for nuclear envelope proteins and underlie an emerging view of the nuclear envelope as a critical signaling node in development and disease.
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Affiliation(s)
- William T Dauer
- Department of Neurology, University of Michigan Medical School, Ann Arbor, MI 48109 USA.
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Attenuated hypertrophic response to pressure overload in a lamin A/C haploinsufficiency mouse. J Mol Cell Cardiol 2009; 48:1290-7. [PMID: 19913544 DOI: 10.1016/j.yjmcc.2009.10.024] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/07/2009] [Accepted: 10/26/2009] [Indexed: 11/24/2022]
Abstract
Inherited mutations cause approximately 30% of all dilated cardiomyopathy cases, with autosomal dominant mutations in the LMNA gene accounting for more than one third of these. The LMNA gene encodes the nuclear envelope proteins lamins A and C, which provide structural support to the nucleus and also play critical roles in transcriptional regulation. Functional deletion of a single allele is sufficient to trigger dilated cardiomyopathy in humans and mice. However, whereas Lmna(-/-) mice develop severe muscular dystrophy and dilated cardiomyopathy and die by 8 weeks of age, heterozygous Lmna(+/-) mice have a much milder phenotype, with changes in ventricular function and morphology only becoming apparent at 1 year of age. Here, we studied 8- to 20-week-old Lmna(+/-) mice and wild-type littermates in a pressure overload model to examine whether increased mechanical load can accelerate or exacerbate myocardial dysfunction in the heterozygotes. While overall survival was similar between genotypes, Lmna(+/-) animals had a significantly attenuated hypertrophic response to pressure overload as evidenced by reduced ventricular mass and myocyte size. Analysis of pressure overload-induced transcriptional changes suggested that the reduced hypertrophy in the Lmna(+/-) mice was accompanied by impaired activation of the mechanosensitive gene Egr-1. In conclusion, our findings provide further support for a critical role of lamins A and C in regulating the cellular response to mechanical stress in cardiomyocytes and demonstrate that haploinsufficiency of lamins A and C alone is sufficient to alter hypertrophic responses and cardiac function in the face of pressure overload in the heart.
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70
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Abstract
Defects in nuclear morphology often correlate with the onset of disease, including cancer, progeria, cardiomyopathy, and muscular dystrophy. However, the mechanism by which a cell controls its nuclear shape is unknown. Here, we use adhesive micropatterned surfaces to control the overall shape of fibroblasts and find that the shape of the nucleus is tightly regulated by the underlying cell adhesion geometry. We found that this regulation occurs through a dome-like actin cap that covers the top of the nucleus. This cap is composed of contractile actin filament bundles containing phosphorylated myosin, which form a highly organized, dynamic, and oriented structure in a wide variety of cells. The perinuclear actin cap is specifically disorganized or eliminated by inhibition of actomyosin contractility and rupture of the LINC complexes, which connect the nucleus to the actin cap. The organization of this actin cap and its nuclear shape-determining function are disrupted in cells from mouse models of accelerated aging (progeria) and muscular dystrophy with distorted nuclei caused by alterations of A-type lamins. These results highlight the interplay between cell shape, nuclear shape, and cell adhesion mediated by the perinuclear actin cap.
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71
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Worman HJ, Fong LG, Muchir A, Young SG. Laminopathies and the long strange trip from basic cell biology to therapy. J Clin Invest 2009; 119:1825-36. [PMID: 19587457 PMCID: PMC2701866 DOI: 10.1172/jci37679] [Citation(s) in RCA: 208] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
The main function of the nuclear lamina, an intermediate filament meshwork lying primarily beneath the inner nuclear membrane, is to provide structural scaffolding for the cell nucleus. However, the lamina also serves other functions, such as having a role in chromatin organization, connecting the nucleus to the cytoplasm, gene transcription, and mitosis. In somatic cells, the main protein constituents of the nuclear lamina are lamins A, C, B1, and B2. Interest in the nuclear lamins increased dramatically in recent years with the realization that mutations in LMNA, the gene encoding lamins A and C, cause a panoply of human diseases ("laminopathies"), including muscular dystrophy, cardiomyopathy, partial lipodystrophy, and progeroid syndromes. Here, we review the laminopathies and the long strange trip from basic cell biology to therapeutic approaches for these diseases.
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Affiliation(s)
- Howard J. Worman
- Department of Medicine and
Department of Pathology and Cell Biology, Columbia University College of Physicians and Surgeons, New York, New York, USA.
Department of Medicine and
Department of Human Genetics, UCLA David Geffen School of Medicine, Los Angeles, California, USA
| | - Loren G. Fong
- Department of Medicine and
Department of Pathology and Cell Biology, Columbia University College of Physicians and Surgeons, New York, New York, USA.
Department of Medicine and
Department of Human Genetics, UCLA David Geffen School of Medicine, Los Angeles, California, USA
| | - Antoine Muchir
- Department of Medicine and
Department of Pathology and Cell Biology, Columbia University College of Physicians and Surgeons, New York, New York, USA.
Department of Medicine and
Department of Human Genetics, UCLA David Geffen School of Medicine, Los Angeles, California, USA
| | - Stephen G. Young
- Department of Medicine and
Department of Pathology and Cell Biology, Columbia University College of Physicians and Surgeons, New York, New York, USA.
Department of Medicine and
Department of Human Genetics, UCLA David Geffen School of Medicine, Los Angeles, California, USA
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72
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Emerson LJ, Holt MR, Wheeler MA, Wehnert M, Parsons M, Ellis JA. Defects in cell spreading and ERK1/2 activation in fibroblasts with lamin A/C mutations. Biochim Biophys Acta Mol Basis Dis 2009; 1792:810-21. [PMID: 19524666 DOI: 10.1016/j.bbadis.2009.05.007] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2009] [Revised: 05/05/2009] [Accepted: 05/13/2009] [Indexed: 01/02/2023]
Abstract
In-frame mutations in nuclear lamin A/C lead to a multitude of tissue-specific degenerative diseases known as the 'laminopathies'. Previous studies have demonstrated that lamin A/C-null mouse fibroblasts have defects in cell polarisation, suggesting a role for lamin A/C in nucleo-cytoskeletal-cell surface cross-talk. However, this has not been examined in patient fibroblasts expressing modified forms of lamin A/C. Here, we analysed skin fibroblasts from 3 patients with Emery-Dreifuss muscular dystrophy and from 1 with dilated cardiomyopathy. The emerin-lamin A/C interaction was impaired in each mutant cell line. Mutant cells exhibited enhanced cell proliferation, collagen-dependent adhesion, larger numbers of filopodia and smaller cell spread size, compared with control cells. Furthermore, cell migration, speed and polarization were elevated. Mutant cells also showed an enhanced ability to contract collagen gels at early time points, compared with control cells. Phosphotyrosine measurements during cell spreading indicated an initial temporal lag in ERK1/2 activation in our mutant cells, followed by hyper-activation of ERK1/2 at 2 h post cell attachment. Deregulated ERK1/2 activation is linked with cardiomyopathy, cell spreading and proliferation defects. We conclude that a functional emerin-lamin A/C complex is required for cell spreading and proliferation, possibly acting through ERK1/2 signalling.
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Affiliation(s)
- Lindsay J Emerson
- The Randall Division of Cell and Molecular Biophysics, King's College, New Hunts House, Guy's Campus, London, SE1 1UL, UK
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73
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Abstract
Recent findings that some 24 inherited diseases and anomalies are caused by defects in proteins of the NE (nuclear envelope) and lamina have resulted in a fundamental reassessment of the functions of the NE and underlying lamina. Instead of just regarding the NE and lamina as a molecular filtering device, regulating the transfer of macromolecules between the cytoplasm and nucleus, we now envisage the NE/lamina functioning as a key cellular 'hub' in integrating critical functions that include chromatin organization, transcriptional regulation, mechanical integrity of the cell and signalling pathways, as well as acting as a key component in the organization and function of the cytoskeleton.
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74
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Nesprin 4 is an outer nuclear membrane protein that can induce kinesin-mediated cell polarization. Proc Natl Acad Sci U S A 2009; 106:2194-9. [PMID: 19164528 DOI: 10.1073/pnas.0808602106] [Citation(s) in RCA: 284] [Impact Index Per Article: 17.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Nucleocytoplasmic coupling is mediated by outer nuclear membrane (ONM) nesprin proteins and inner nuclear membrane Sun proteins. Interactions spanning the perinuclear space create nesprin-Sun complexes connecting the cytoskeleton to nuclear components. A search for proteins displaying a conserved C-terminal sequence present in nesprins 1-3 identified nesprin 4 (Nesp4), a new member of this family. Nesp4 is a kinesin-1-binding protein that displays Sun-dependent localization to the ONM. Expression of Nesp4 is associated with dramatic changes in cellular organization involving relocation of the centrosome and Golgi apparatus relative to the nucleus. These effects can be accounted for entirely by Nesp4's kinesin-binding function. The implication is that Nesp4 may contribute to microtubule-dependent nuclear positioning.
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75
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Muchir A, Wu W, Worman HJ. Reduced expression of A-type lamins and emerin activates extracellular signal-regulated kinase in cultured cells. BIOCHIMICA ET BIOPHYSICA ACTA 2009; 1792:75-81. [PMID: 19022376 PMCID: PMC2646592 DOI: 10.1016/j.bbadis.2008.10.012] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Received: 09/24/2008] [Revised: 10/17/2008] [Accepted: 10/20/2008] [Indexed: 11/21/2022]
Abstract
BACKGROUND Mutations in genes encoding A-type lamins and emerin cause cardiomyopathy and muscular dystrophy. We previously showed activation of the extracellular signal-regulated kinase (ERK) branch of the mitogen-activated protein kinase (MAPK) cascade in hearts of mice with mutations in these genes. Here, we tested the hypothesis that reducing A-type lamins and emerin in cultured cells activate ERK signaling. METHODS We used siRNA to knockdown A-type lamins and emerin in HeLa and C2C12 cells. Activation of ERK was assessed by immunoblotting and immunofluorescence microscopy with antibodies against phosphorylated protein and by using real-time RT-PCR to measure RNAs encoded by genes for transcription factors stimulated by ERK. RESULTS Knockdown of A-type lamins and emerin in HeLa and C2C12 stimulated phosphorylation and nuclear translocation of ERK as well as activation of genes encoding downstream transcription factors. A MAPK/ERK kinase (MEK) inhibitor reduced ERK phosphorylation in cells with reduced expression of A-type lamins and emerin. CONCLUSIONS These results provide proof for the hypothesis that altered expression of emerin and A-type lamins activates ERK signaling, which in turn can cause cardiomyopathy. GENERAL SIGNIFICANCE ERK is a potential target for the pharmacological treatment of cardiomyopathy caused by mutations in the genes encoding emerin and A-type lamins.
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Affiliation(s)
- Antoine Muchir
- Departments of Medicine and of Pathology and Cell Biology, College of Physicians and Surgeons, Columbia University, New York, USA
| | - Wei Wu
- Departments of Medicine and of Pathology and Cell Biology, College of Physicians and Surgeons, Columbia University, New York, USA
| | - Howard J. Worman
- Departments of Medicine and of Pathology and Cell Biology, College of Physicians and Surgeons, Columbia University, New York, USA
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76
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Joining the dots: Production, processing and targeting of U snRNP to nuclear bodies. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2008; 1783:2137-44. [DOI: 10.1016/j.bbamcr.2008.07.025] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/08/2008] [Revised: 07/22/2008] [Accepted: 07/23/2008] [Indexed: 11/20/2022]
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77
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Fidziańska A, Bilińska ZT, Tesson F, Wagner T, Walski M, Grzybowski J, Ruzyłło W, Hausmanowa-Petrusewicz I. Obliteration of cardiomyocyte nuclear architecture in a patient with LMNA gene mutation. J Neurol Sci 2008; 271:91-6. [PMID: 18502446 DOI: 10.1016/j.jns.2008.03.017] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2006] [Revised: 02/26/2008] [Accepted: 03/24/2008] [Indexed: 12/23/2022]
Abstract
OBJECTIVE The aim of our study was to perform an immunohistochemical and ultrastructural analysis of the nuclear architecture of cardiomyocytes from an end-stage DCM patient with a missense point mutation in the exon 3 of the LMNA gene which is predicted to result in a D192G substitution. METHODS We studied endomyocardial biopsy samples taken from the right ventricle by immunostaining using antibodies against the lamins A and C and by electron microscopy. The cardiomyocyte ultrastructure was analysed, with particular attention to the nuclear architecture. RESULTS Thirty percent of cardiomyocyte nuclei from the D192G carrier showed chromatin disorganization and a changed nuclear shape. The most surprising finding was the appearance of sarcoplasmic organelles within the nuclear matrix of well enveloped nuclei. To our knowledge, this intriguing phenomenon was observed for the first time in cardiomyocytes. CONCLUSION The study documents that D192G mutation in LMNA gene may lead to the disruption of the nuclear wall in cardiomyocytes, thus supporting the mechanical hypothesis of dilated cardiomyopathy development in humans, which might be mutation-specific.
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Affiliation(s)
- Anna Fidziańska
- Neuromuscular Unit, Medical Research Center, Pol. Ac. Sci., Warsaw, Poland.
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78
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Burke B, Stewart CL. The laminopathies: the functional architecture of the nucleus and its contribution to disease. Annu Rev Genomics Hum Genet 2008; 7:369-405. [PMID: 16824021 DOI: 10.1146/annurev.genom.7.080505.115732] [Citation(s) in RCA: 120] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Most inherited diseases are associated with mutations in a specific gene. Often, mutations in two or more different genes result in diseases with a similar phenotype. Rarely do different mutations in the same gene result in a multitude of seemingly different and unrelated diseases. Mutations in the Lamin A gene (LMNA), which encodes largely ubiquitously expressed nuclear proteins (A-type lamins), are associated with at least eight different diseases, collectively called the laminopathies. Studies examining how different tissue-specific diseases arise from unique LMNA mutations are providing unanticipated insights into the structural organization of the nucleus, and how disruption of this organization relates to novel mechanisms of disease.
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Affiliation(s)
- Brian Burke
- Department of Anatomy and Cell Biology, University of Florida, Gainesville, Florida 32610
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79
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Dreuillet C, Harper M, Tillit J, Kress M, Ernoult-Lange M. Mislocalization of human transcription factor MOK2 in the presence of pathogenic mutations of lamin A/C. Biol Cell 2008; 100:51-61. [PMID: 17760566 DOI: 10.1042/bc20070053] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
BACKGROUND INFORMATION hsMOK2 (human MOK2) is a DNA-binding transcriptional repressor. For example, it represses the IRBP (interphotoreceptor retinoid-binding protein) gene by competing with the CRX (cone-rod homeobox protein) transcriptional activator for DNA binding. Previous studies have shown an interaction between hsMOK2 and nuclear lamin A/C. This interaction could be important to explain hsMOK2 ability to repress transcription. RESULTS In the present study, we have tested whether missense pathogenic mutations of lamin A/C, which are located in the hsMOK2-binding domain, could affect the interaction with hsMOK2. We find that none of the tested mutations is able to disrupt hsMOK2 binding in vitro or in vivo. However, we observe an aberrant cellular localization of hsMOK2 into nuclear aggregates when pathogenic lamin A/C mutant proteins are expressed. CONCLUSIONS These results indicate that pathogenic mutations in lamin A/C lead to sequestration of hsMOK2 into nuclear aggregates, which may deregulate MOK2 target genes.
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Affiliation(s)
- Caroline Dreuillet
- CNRS-FRE2937, Institut André Lwoff, 7 rue Guy Môquet, 94801 Villejuif, France
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80
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Parnaik VK. Role of Nuclear Lamins in Nuclear Organization, Cellular Signaling, and Inherited Diseases. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2008; 266:157-206. [DOI: 10.1016/s1937-6448(07)66004-3] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
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81
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Cohen TV, Stewart CL. Fraying at the edge mouse models of diseases resulting from defects at the nuclear periphery. Curr Top Dev Biol 2008; 84:351-84. [PMID: 19186248 DOI: 10.1016/s0070-2153(08)00607-8] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Eukaryotic cells compartmentalize their genetic material within the nucleus. The boundary separating the genetic material from the cytoplasm is the nuclear envelope (NE) and lamina. Historically, the NE was perceived as functioning primarily as a barrier regulating the entry and exit of macromolecules between the nucleus and cytoplasm via the nuclear pore complexes (NPCs) that traverse the nuclear membranes. However, recent findings have caused a fundamental reassessment with regard to NE and lamina functions. Evidence now points to the NE and lamina functioning as a "hub" in regulating and perhaps integrating critical cellular functions that include chromatin organization, transcriptional regulation, mechanical integrity of the cell, signaling pathways, as well as acting as a key component of the cytoskeleton. Such an integral role for the nuclear boundary has emerged from increased interest into the functions of the NE/lamina, which has been largely stimulated by the discovery that some 24 different diseases and anomalies are caused by defects in proteins of the NE and lamina.
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Affiliation(s)
- Tatiana V Cohen
- Center for Genetic Medicine, Children's National Medical Center, N.W. Washington, DC 20010, USA
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82
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LMNA Messenger RNA Expression in Highly Active Antiretroviral Therapy-Treated HIV-Positive Patients. J Acquir Immune Defic Syndr 2007; 46:384-9. [DOI: 10.1097/qai.0b013e31815aba1b] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
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83
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Stewart CL, Roux KJ, Burke B. Blurring the Boundary: The Nuclear Envelope Extends Its Reach. Science 2007; 318:1408-12. [DOI: 10.1126/science.1142034] [Citation(s) in RCA: 208] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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84
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Stewart CL, Kozlov S, Fong LG, Young SG. Mouse models of the laminopathies. Exp Cell Res 2007; 313:2144-56. [PMID: 17493612 PMCID: PMC1949387 DOI: 10.1016/j.yexcr.2007.03.026] [Citation(s) in RCA: 87] [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: 01/21/2007] [Revised: 03/05/2007] [Accepted: 03/12/2007] [Indexed: 12/25/2022]
Abstract
The A and B type lamins are nuclear intermediate filament proteins that comprise the bulk of the nuclear lamina, a thin proteinaceous structure underlying the inner nuclear membrane. The A type lamins are encoded by the lamin A gene (LMNA). Mutations in this gene have been linked to at least nine diseases, including the progeroid diseases Hutchinson-Gilford progeria and atypical Werner's syndromes, striated muscle diseases including muscular dystrophies and dilated cardiomyopathies, lipodystrophies affecting adipose tissue deposition, diseases affecting skeletal development, and a peripheral neuropathy. To understand how different diseases arise from different mutations in the same gene, mouse lines carrying some of the same mutations found in the human diseases have been established. We, and others have generated mice with different mutations that result in progeria, muscular dystrophy, and dilated cardiomyopathy. To further our understanding of the functions of the lamins, we also created mice lacking lamin B1, as well as mice expressing only one of the A type lamins. These mouse lines are providing insights into the functions of the lamina and how changes to the lamina affect the mechanical integrity of the nucleus as well as signaling pathways that, when disrupted, may contribute to the disease.
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Affiliation(s)
- Colin L Stewart
- Laboratory of Cancer and Developmental Biology, National Cancer Institute, Frederick, Maryland 21702, USA.
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85
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Worman HJ, Bonne G. "Laminopathies": a wide spectrum of human diseases. Exp Cell Res 2007; 313:2121-33. [PMID: 17467691 PMCID: PMC2964355 DOI: 10.1016/j.yexcr.2007.03.028] [Citation(s) in RCA: 496] [Impact Index Per Article: 27.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2007] [Revised: 03/08/2007] [Accepted: 03/12/2007] [Indexed: 12/23/2022]
Abstract
Mutations in genes encoding the intermediate filament nuclear lamins and associated proteins cause a wide spectrum of diseases sometimes called "laminopathies." Diseases caused by mutations in LMNA encoding A-type lamins include autosomal dominant Emery-Dreifuss muscular dystrophy and related myopathies, Dunnigan-type familial partial lipodystrophy, Charcot-Marie-Tooth disease type 2B1 and developmental and accelerated aging disorders. Duplication in LMNB1 encoding lamin B1 causes autosomal dominant leukodystrophy and mutations in LMNB2 encoding lamin B2 are associated with acquired partial lipodystrophy. Disorders caused by mutations in genes encoding lamin-associated integral inner nuclear membrane proteins include X-linked Emery-Dreifuss muscular dystrophy, sclerosing bone dysplasias, HEM/Greenberg skeletal dysplasia and Pelger-Huet anomaly. While mutations and clinical phenotypes of "laminopathies" have been carefully described, data explaining pathogenic mechanisms are only emerging. Future investigations will likely identify new "laminopathies" and a combination of basic and clinical research will lead to a better understanding of pathophysiology and the development of therapies.
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Affiliation(s)
- Howard J Worman
- Department of Medicine, College of Physicians and Surgeons, Columbia University, 630 West 168th Street, New York, NY 10032, USA.
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86
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Gieni RS, Hendzel MJ. Mechanotransduction from the ECM to the genome: Are the pieces now in place? J Cell Biochem 2007; 104:1964-87. [PMID: 17546585 DOI: 10.1002/jcb.21364] [Citation(s) in RCA: 105] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
A multitude of biochemical signaling processes have been characterized that affect gene expression and cellular activity. However, living cells often need to integrate biochemical signals with mechanical information from their microenvironment as they respond. In fact, the signals received by shape alone can dictate cell fate. This mechanotrasduction of information is powerful, eliciting proliferation, differentiation, or apoptosis in a manner dependent upon the extent of physical deformation. The cells internal "prestressed" structure and its "hardwired" interaction with the extra-cellular matrix (ECM) appear to confer this ability to filter biochemical signals and decide between divergent cell functions influenced by the nature of signals from the mechanical environment. In some instances mechanical signaling through the tissue microenvironment has been shown to be dominant over genomic defects, imparting a normal phenotype on cells that otherwise have transforming genetic lesions. This mechanical control of phenotype is postulated to have a central role in embryogenesis, tissue physiology as well as the pathology of a wide variety of diseases, including cancer. We will briefly review studies showing physical continuity between the external cellular microenvironment and the interior of the cell nucleus. Newly characterized structures, termed nuclear envelope lamina spanning complexes (NELSC), and their interactions will be described as part of a model for mechanical transduction of extracellular cues from the ECM to the genome.
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Affiliation(s)
- Randall S Gieni
- Cross Cancer Institute and Department of Oncology, Faculty of Medicine, University of Alberta, Edmonton, Alberta, Canada
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87
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Hegele RA, Oshima J. Phenomics and lamins: From disease to therapy. Exp Cell Res 2007; 313:2134-43. [PMID: 17466974 DOI: 10.1016/j.yexcr.2007.03.023] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2007] [Revised: 03/19/2007] [Accepted: 03/22/2007] [Indexed: 11/19/2022]
Abstract
Systematic correlation of phenotype with genotype is a key goal of the emerging field of phenomics, which is expected to help define complex diseases. Careful evaluation of phenotype-genotype associations in monogenic disorders, such as laminopathies, might provide new hypotheses to be tested with molecular and cellular studies and might also suggest potential new intervention strategies. For instance, evaluation of the clinical features of carriers of mutant LMNA in kindreds with familial partial lipodystrophy suggests rational, staged intervention using established pharmaceutical agents to prevent cardiovascular complications not just for patients with lipodystrophy but by extension for patients with the common metabolic syndrome. Careful non-invasive imaging shows phenotypic differences between partial lipodystrophy due to mutant LMNA and not due to mutant LMNA. Furthermore, hierarchical cluster analysis detects systematic relationships between organ involvement in laminopathies and mutation position in the LMNA genomic sequence. However, sometimes the same LMNA mutation can underlie markedly different clinical phenotypes; cellular and molecular experiments can help to explain the mechanistic basis for such differences. Finally, promising novel treatment modalities for laminopathies, such as farnesyl transferase inhibition and gene-based therapies, might help not only to illuminate mechanisms that link genotype to phenotype, but also to provide hope for patients suffering with laminopathies, since these treatments are designed to modulate key early or proximal steps in the pathogenesis of these disorders.
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Affiliation(s)
- Robert A Hegele
- Schulich School of Medicine and Dentistry, University of Western Ontario and Vascular Biology Research Group, Robarts Research Institute, London, Ontario, Canada N6A 5K8.
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88
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Abstract
Emery-Dreifuss muscular dystrophy (EDMD) is inherited in an X-linked or autosomal manner. X-linked EDMD is caused by mutations in EMD, which encodes an integral protein of the nuclear envelope inner membrane called emerin. Autosomally inherited EDMD is caused by mutations in LMNA, which encodes A-type nuclear lamins, intermediate filament proteins associated with inner nuclear membrane. Although the causative mutations have been described and mouse models have been created, the pathogenic processes by which mutations in genes encoding nuclear envelope proteins cause striated muscle abnormalities in EDMD remain obscure. Working hypotheses include effects on nuclear structural integrity, increased cellular susceptibility to mechanical stress damage, alterations in gene expression in response to nuclear envelope changes, and effects on cell proliferation and differentiation.
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Affiliation(s)
- Antoine Muchir
- Department of Medicine, College of Physicians and Surgeons, Columbia University, New York, NY 10032, USA
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89
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Roux KJ, Burke B. Nuclear envelope defects in muscular dystrophy. Biochim Biophys Acta Mol Basis Dis 2007; 1772:118-27. [PMID: 16904876 DOI: 10.1016/j.bbadis.2006.06.001] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2006] [Accepted: 06/03/2006] [Indexed: 11/29/2022]
Abstract
Muscular dystrophies are a heterogeneous group of disorders linked to defects in 20-30 different genes. Mutations in the genes encoding a pair of nuclear envelope proteins, emerin and lamin A/C, have been shown to cause the X-linked and autosomal forms respectively of Emery-Dreifuss muscular dystrophy. A third form of muscular dystrophy, limb girdle muscular dystrophy 1b, has also been linked to mutations in the lamin A/C gene. Given that these two genes are ubiquitously expressed, a major goal is to determine how they can be associated with tissue specific diseases. Recent results suggest that lamin A/C and emerin contribute to the maintenance of nuclear envelope structure and at the same time may modulate the expression patterns of certain mechanosensitive and stress induced genes. Both emerin and lamin A/C may play an important role in the response of cells to mechanical stress and in this way may help to maintain muscle cell integrity.
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Affiliation(s)
- Kyle J Roux
- Department of Anatomy and Cell Biology, The University of Florida College of Medicine, 1600 SW Archer Road, Gainesville, FL 32606, USA
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90
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Heydemann A, Doherty KR, McNally EM. Genetic modifiers of muscular dystrophy: Implications for therapy. Biochim Biophys Acta Mol Basis Dis 2007; 1772:216-28. [PMID: 16916601 DOI: 10.1016/j.bbadis.2006.06.013] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2006] [Accepted: 06/22/2006] [Indexed: 10/24/2022]
Abstract
The genetic understanding of the muscular dystrophies has advanced considerably in the last two decades. Over 25 different individual genes are now known to produce muscular dystrophy, and many different "private" mutations have been described for each individual muscular dystrophy gene. For the more common forms of muscular dystrophy, phenotypic variability can be explained by precise mutations. However, for many genetic mutations, the presence of the identical mutation is associated with marked phenotypic range that affects muscle function as well as cardiac function. The explanation for phenotype variability in the muscular dystrophies is only now being explored. The availability of genetically engineered animal models has allowed the generation of single mutations on the background of highly inbred strain. Phenotypic variation that is altered by genetic background argues for the presence of genetic modifier loci that can ameliorate or enhance aspects of the dystrophic phenotype. A number of individual genes have been implicated as modifiers of muscular dystrophy by studies in genetically engineered mouse models of muscular dystrophy. The value of these genes and products is that the pathways identified through these experiments may be exploited for therapy.
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Affiliation(s)
- Ahlke Heydemann
- Department of Medicine, Section of Cardiology, The University of Chicago, Chicago, IL 60637, USA
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91
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Brachner A, Reipert S, Foisner R, Gotzmann J. LEM2 is a novel MAN1-related inner nuclear membrane protein associated with A-type lamins. J Cell Sci 2007; 118:5797-810. [PMID: 16339967 DOI: 10.1242/jcs.02701] [Citation(s) in RCA: 121] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
The LEM (lamina-associated polypeptide-emerin-MAN1) domain is a motif shared by a group of lamin-interacting proteins in the inner nuclear membrane (INM) and in the nucleoplasm. The LEM domain mediates binding to a DNA-crosslinking protein, barrier-to-autointegration factor (BAF). We describe a novel, ubiquitously expressed LEM domain protein, LEM2, which is structurally related to MAN1. LEM2 contains an N-terminal LEM motif, two predicted transmembrane domains and a MAN1-Src1p C-terminal (MSC) domain highly homologous to MAN1, but lacks the MAN1-specific C-terminal RNA-recognition motif. Immunofluorescence microscopy of digitonin-treated cells and subcellular fractionation identified LEM2 as a lamina-associated protein residing in the INM. LEM2 binds to the lamin C tail in vitro. Targeting of LEM2 to the nuclear envelope requires A-type lamins and is mediated by the N-terminal and transmembrane domains. Highly overexpressed LEM2 accumulates in patches at the nuclear envelope and forms membrane bridges between nuclei of adjacent cells. LEM2 structures recruit A-type lamins, emerin, MAN1 and BAF, whereas lamin B and lamin B receptor are excluded. Our data identify LEM2 as a novel A-type-lamin-associated INM protein involved in nuclear structure organization.
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Affiliation(s)
- Andreas Brachner
- Department of Medical Biochemistry, Max F. Perutz Laboratories, Vienna Biocenter, Medical University of Vienna, Dr Bohrgasse 9/3, A-1030 Vienna, Austria
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92
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Abstract
Experiments were performed to characterize a prominent nuclear matrix (NM) protein isolated from tissue cultured mouse lens epithelial cells. This NM protein was separated by SDS-PAGE and the stained gel band was analyzed by mass spectroscopy. Blast analysis of the amino acid sequence derived by mass spectroscopy revealed the presence of Lamin C in the NM of the mouse lens epithelial cells. We also examined nuclear proteins of adult and fetal human lenses. Data collected from these experiments showed the presence of Lamin C in both adult and fetal lens cells. However fetal lens cells only show Lamin C dimers, whereas adult human lens contained dimers, monomers and degraded Lamin C. Early and late passaged tissue cultured mouse lens epithelial cells also contained Lamin C in the nucleus with a preponderance of the dimer in the early passaged cells. The biological significance of the presence of dimers in human fetal lens cells and early passaged mouse lens cells is not known. However, it could suggest an enhanced docking capability of Lamin C dimers for other physiologically important nuclear proteins.
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Affiliation(s)
- M Bagchi
- Department of Anatomy and Cell Biology, Wayne State University, School of Medicine, Detroit, MI 48201, USA.
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93
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Abstract
Hutchinson-Gilford progeria syndrome (HGPS) is caused by a LMNA mutation that leads to the synthesis of a mutant prelamin A that is farnesylated but cannot be further processed to mature lamin A. A more severe progeroid disorder, restrictive dermopathy (RD), is caused by the loss of the prelamin A-processing enzyme, ZMPSTE24. The absence of ZMPSTE24 prevents the endoproteolytic processing of farnesyl-prelamin A to mature lamin A and leads to the accumulation of farnesyl-prelamin A. In both HGPS and RD, the farnesyl-prelamin A is targeted to the nuclear envelope, where it interferes with the integrity of the nuclear envelope and causes misshapen cell nuclei. Recent studies have shown that the frequency of misshapen nuclei can be reduced by treating cells with a farnesyltransferase inhibitor (FTI). Also, administering an FTI to mouse models of HGPS and RD ameliorates the phenotypes of progeria. These studies have prompted interest in testing the efficacy of FTIs in children with HGPS.
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Affiliation(s)
- Stephen G Young
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, California 90095, USA.
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94
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Parnaik VK, Manju K. Laminopathies: multiple disorders arising from defects in nuclear architecture. J Biosci 2006; 31:405-21. [PMID: 17006023 DOI: 10.1007/bf02704113] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Lamins are the major structural proteins of the nucleus in an animal cell. In addition to being essential for nuclear integrity and assembly, lamins are involved in the organization of nuclear processes such as DNA replication, transcription and repair. Mutations in the human lamin A gene lead to highly debilitating genetic disorders that primarily affect muscle, adipose, bone or neuronal tissues and also cause premature ageing syndromes. Mutant lamins alter nuclear integrity and hinder signalling pathways involved in muscle differentiation and adipocyte differentiation, suggesting tissue-specific roles for lamins. Furthermore, cells expressing mutant lamins are impaired in their response to DNA damaging agents. Recent reports indicate that certain lamin mutations act in a dominant negative manner to cause nuclear defects and cellular toxicity, and suggest a possible role for aberrant lamins in normal ageing processes.
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Affiliation(s)
- Veena K Parnaik
- Centre for Cellular and Molecular Biology, Hyderabad, India.
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95
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Lammerding J, Fong LG, Ji JY, Reue K, Stewart CL, Young SG, Lee RT. Lamins A and C but not lamin B1 regulate nuclear mechanics. J Biol Chem 2006; 281:25768-80. [PMID: 16825190 DOI: 10.1074/jbc.m513511200] [Citation(s) in RCA: 519] [Impact Index Per Article: 27.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Mutations in the nuclear envelope proteins lamins A and C cause a broad variety of human diseases, including Emery-Dreifuss muscular dystrophy, dilated cardiomyopathy, and Hutchinson-Gilford progeria syndrome. Cells lacking lamins A and C have reduced nuclear stiffness and increased nuclear fragility, leading to increased cell death under mechanical strain and suggesting a potential mechanism for disease. Here, we investigated the contribution of major lamin subtypes (lamins A, C, and B1) to nuclear mechanics by analyzing nuclear shape, nuclear dynamics over time, nuclear deformations under strain, and cell viability under prolonged mechanical stimulation in cells lacking both lamins A and C, cells lacking only lamin A (i.e. "lamin C-only" cells), cells lacking wild-type lamin B1, and wild-type cells. Lamin A/C-deficient cells exhibited increased numbers of misshapen nuclei and had severely reduced nuclear stiffness and decreased cell viability under strain. Lamin C-only cells had slightly abnormal nuclear shape and mildly reduced nuclear stiffness but no decrease in cell viability under strain. Interestingly, lamin B1-deficient cells exhibited normal nuclear mechanics despite having a significantly increased frequency of nuclear blebs. Our study indicates that lamins A and C are important contributors to the mechanical stiffness of nuclei, whereas lamin B1 contributes to nuclear integrity but not stiffness.
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Affiliation(s)
- Jan Lammerding
- Cardiovascular Division, Department of Medicine, and Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts 02139, USA.
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96
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Hübner S, Eam JE, Wagstaff KM, Jans DA. Quantitative analysis of localization and nuclear aggregate formation induced by GFP-lamin A mutant proteins in living HeLa cells. J Cell Biochem 2006; 98:810-26. [PMID: 16440304 DOI: 10.1002/jcb.20791] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Although A-type lamins are ubiquitously expressed, their role in the tissue-specificity of human laminopathies remains enigmatic. In this study, we generate a series of transfection constructs encoding missense lamin A mutant proteins fused to green fluorescent protein and investigate their subnuclear localization using quantitative live cell imaging. The mutant constructs used included the laminopathy-inducing lamin A rod domain mutants N195K, E358K, M371K, R386K, the tail domain mutants G465D, R482L, and R527P, and the Hutchinson-Gilford progeria syndrome-causing deletion mutant, progerin (LaA delta50). All mutant derivatives induced nuclear aggregates, except for progerin, which caused a more lobulated phenotype of the nucleus. Quantitative analysis revealed that the frequency of nuclear aggregate formation was significantly higher (two to four times) for the mutants compared to the wild type, although the level of lamin fusion proteins within nuclear aggregates was not. The distribution of endogenous A-type lamins was altered by overexpression of the lamin A mutants, coexpression experiments revealing that aberrant localization of the N195K and R386K mutants had no effect on the subnuclear distribution of histones H2A or H2B, or on nuclear accumulation of H2A overexpressed as a DsRed2 fusion protein. The GFP-lamin fusion protein-expressing constructs will have important applications in the future, enabling live cell imaging of nuclear processes involving lamins and how this may relate to the pathogenesis of laminopathies.
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Affiliation(s)
- S Hübner
- Nuclear Signaling Laboratory, Department of Biochemistry and Molecular Biology, PO Box 13D, Monash University, Clayton, Victoria 3800, Australia.
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97
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Nitta RT, Jameson SA, Kudlow BA, Conlan LA, Kennedy BK. Stabilization of the retinoblastoma protein by A-type nuclear lamins is required for INK4A-mediated cell cycle arrest. Mol Cell Biol 2006; 26:5360-72. [PMID: 16809772 PMCID: PMC1592700 DOI: 10.1128/mcb.02464-05] [Citation(s) in RCA: 64] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
Mutations in the LMNA gene, which encodes all A-type lamins, including lamin A and lamin C, cause a variety of tissue-specific degenerative diseases termed laminopathies. Little is known about the pathogenesis of these disorders. Previous studies have indicated that A-type lamins interact with the retinoblastoma protein (pRB). Here we probe the functional consequences of this association and further examine links between nuclear structure and cell cycle control. Since pRB is required for cell cycle arrest by p16(ink4a), we tested the responsiveness of multiple lamin A/C-depleted cell lines to overexpression of this CDK inhibitor and tumor suppressor. We find that the loss of A-type lamin expression results in marked destabilization of pRB. This reduction in pRB renders cells resistant to p16(ink4a)-mediated G(1) arrest. Reintroduction of lamin A, lamin C, or pRB restores p16(ink4a)-responsiveness to Lmna(-/-) cells. An array of lamin A mutants, representing a variety of pathologies as well as lamin A processing mutants, was introduced into Lmna(-/-) cells. Of these, a mutant associated with mandibuloacral dysplasia (MAD R527H), as well as two lamin A processing mutants, but not other disease-associated mutants, failed to restore p16(ink4a) responsiveness. Although our findings do not rule out links between altered pRB function and laminopathies, they fail to support such an assertion. These findings do link lamin A/C to the functional activation of a critical tumor suppressor pathway and further the possibility that somatic mutations in LMNA contribute to tumor progression.
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Affiliation(s)
- Ryan T Nitta
- Department of Biochemistry, University of Washington, Seattle, WA 98195, USA.
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98
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Broers JLV, Ramaekers FCS, Bonne G, Yaou RB, Hutchison CJ. Nuclear Lamins: Laminopathies and Their Role in Premature Ageing. Physiol Rev 2006; 86:967-1008. [PMID: 16816143 DOI: 10.1152/physrev.00047.2005] [Citation(s) in RCA: 432] [Impact Index Per Article: 22.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
It has been demonstrated that nuclear lamins are important proteins in maintaining cellular as well as nuclear integrity, and in maintaining chromatin organization in the nucleus. Moreover, there is growing evidence that lamins play a prominent role in transcriptional control. The family of laminopathies is a fast-growing group of diseases caused by abnormalities in the structure or processing of the lamin A/C ( LMNA) gene. Mutations or incorrect processing cause more than a dozen different inherited diseases, ranging from striated muscular diseases, via fat- and peripheral nerve cell diseases, to progeria. This broad spectrum of diseases can only be explained if the responsible A-type lamin proteins perform multiple functions in normal cells. This review gives an overview of current knowledge on lamin structure and function and all known diseases associated with LMNA abnormalities. Based on the knowledge of the different functions of A-type lamins and associated proteins, explanations for the observed phenotypes are postulated. It is concluded that lamins seem to be key players in, among others, controlling the process of cellular ageing, since disturbance in lamin protein structure gives rise to several forms of premature ageing.
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Affiliation(s)
- J L V Broers
- Department of Molecular Cell Biology, University of Maastricht, Research Institutes CARIM, GROW, and EURON, The Netherlands
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99
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Taylor MRG, Slavov D, Gajewski A, Vlcek S, Ku L, Fain PR, Carniel E, Di Lenarda A, Sinagra G, Boucek MM, Cavanaugh J, Graw SL, Ruegg P, Feiger J, Zhu X, Ferguson DA, Bristow MR, Gotzmann J, Foisner R, Mestroni L. Thymopoietin (lamina-associated polypeptide 2) gene mutation associated with dilated cardiomyopathy. Hum Mutat 2006; 26:566-74. [PMID: 16247757 DOI: 10.1002/humu.20250] [Citation(s) in RCA: 130] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Thymopoietin or TMPO (indicated by its alternative gene symbol, LAP2, in this work) has been proposed as a candidate disease gene for dilated cardiomyopathy (DCM), since a LAP2 product associates with nucleoplasmic lamins A/C, which are encoded by the DCM gene LMNA. We developed a study to screen for genetic mutations in LAP2 in a large collection of DCM patients and families. A total of 113 subjects from 88 families (56 with familial DCM (FDC) and 32 with sporadic DCM) were screened for LAP2 mutations using denaturing high-performance liquid chromatography and sequence analysis. We found a single putative mutation affecting the LAP2alpha isoform in one FDC pedigree. The mutation predicts an Arg690Cys substitution (c.2068C>T; p.R690C) located in the C-terminal domain of the LAP2alpha protein, a region that is known to interact with lamin A/C. RT-PCR, Western blot analyses, and immunolocalization revealed low-level LAP2alpha expression in adult cardiac muscle, and localization to a subset of nuclei. Mutated Arg690Cys LAP2alpha expressed in HeLa cells localized to the nucleoplasm like wild-type LAP2alpha, with no effect on peripheral and nucleoplasmic lamin A distribution. However, the in vitro interaction of mutated LAP2alpha with the pre-lamin A C-terminus was significantly compromised compared to the wild-type protein. LAP2 mutations may represent a rare cause of DCM. The Arg690Cys mutation altered the observed LAP2alpha interaction with A-type lamins. Our finding implicates a novel nuclear lamina-associated protein in the pathogenesis of genetic forms of dilated cardiomyopathy.
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Affiliation(s)
- Matthew R G Taylor
- CU-Cardiovascular Institute, University of Colorado Health Sciences Center, Denver, Colorado, USA.
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100
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Manju K, Muralikrishna B, Parnaik VK. Expression of disease-causing lamin A mutants impairs the formation of DNA repair foci. J Cell Sci 2006; 119:2704-14. [PMID: 16772334 DOI: 10.1242/jcs.03009] [Citation(s) in RCA: 113] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
A-type lamins are components of the nuclear lamina. Mutations in the gene encoding lamin A are associated with a range of highly degenerative diseases termed laminopathies. To evaluate sensitivity to DNA damage, GFP-tagged lamin A cDNAs with disease-causing mutations were expressed in HeLa cells. The inner nuclear membrane protein emerin was mislocalised upon expression of the muscular dystrophy mutants G232E, Q294P or R386K, which aberrantly assembled into nuclear aggregates, or upon expression of mutants causing progeria syndromes in vivo (lamin A del50, R471C, R527C and L530P). The ability of cells expressing these mutants to form DNA repair foci comprising phosphorylated H2AX in response to mild doses of cisplatin or UV irradiation was markedly diminished, unlike the nearly normal response of cells expressing wild-type GFP-lamin A or disease-causing H222P and R482L mutants. Interestingly, mutants that impaired the formation of DNA repair foci mislocalised ATR (for ;ataxia telangiectasia-mutated and Rad3-related') kinase, which is a key sensor in the response to DNA damage. Our results suggest that a subset of lamin A mutants might hinder the response of components of the DNA repair machinery to DNA damage by altering interactions with chromatin.
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Affiliation(s)
- Kaliyaperumal Manju
- Centre for Cellular and Molecular Biology, Uppal Road, Hyderabad 500007, India
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