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Brown SJ, Kline RA, Synowsky SA, Shirran SL, Holt I, Sillence KA, Claus P, Wirth B, Wishart TM, Fuller HR. The Proteome Signatures of Fibroblasts from Patients with Severe, Intermediate and Mild Spinal Muscular Atrophy Show Limited Overlap. Cells 2022; 11:cells11172624. [PMID: 36078032 PMCID: PMC9454632 DOI: 10.3390/cells11172624] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2022] [Revised: 08/17/2022] [Accepted: 08/18/2022] [Indexed: 12/04/2022] Open
Abstract
Most research to characterise the molecular consequences of spinal muscular atrophy (SMA) has focused on SMA I. Here, proteomic profiling of skin fibroblasts from severe (SMA I), intermediate (SMA II), and mild (SMA III) patients, alongside age-matched controls, was conducted using SWATH mass spectrometry analysis. Differentially expressed proteomic profiles showed limited overlap across each SMA type, and variability was greatest within SMA II fibroblasts, which was not explained by SMN2 copy number. Despite limited proteomic overlap, enriched canonical pathways common to two of three SMA severities with at least one differentially expressed protein from the third included mTOR signalling, regulation of eIF2 and eIF4 signalling, and protein ubiquitination. Network expression clustering analysis identified protein profiles that may discriminate or correlate with SMA severity. From these clusters, the differential expression of PYGB (SMA I), RAB3B (SMA II), and IMP1 and STAT1 (SMA III) was verified by Western blot. All SMA fibroblasts were transfected with an SMN-enhanced construct, but only RAB3B expression in SMA II fibroblasts demonstrated an SMN-dependent response. The diverse proteomic profiles and pathways identified here pave the way for studies to determine their utility as biomarkers for patient stratification or monitoring treatment efficacy and for the identification of severity-specific treatments.
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Affiliation(s)
- Sharon J. Brown
- School of Pharmacy and Bioengineering (PhaB), Keele University, Keele ST5 5BG, UK
- Wolfson Centre for Inherited Neuromuscular Disease, RJAH Orthopaedic Hospital, Oswestry SY10 7AG, UK
| | - Rachel A. Kline
- The Roslin Institute and Royal (Dick) School of Veterinary Studies, University of Edinburgh, Midlothian EH25 9RG, UK
- Euan MacDonald Centre, University of Edinburgh, Edinburgh EH16 4SB, UK
| | - Silvia A. Synowsky
- BSRC Mass Spectrometry and Proteomics Facility, University of St Andrews, St Andrews KY16 9ST, UK
| | - Sally L. Shirran
- BSRC Mass Spectrometry and Proteomics Facility, University of St Andrews, St Andrews KY16 9ST, UK
| | - Ian Holt
- Wolfson Centre for Inherited Neuromuscular Disease, RJAH Orthopaedic Hospital, Oswestry SY10 7AG, UK
| | | | - Peter Claus
- SMATHERIA gGmbH—Non-Profit Biomedical Research Institute, 30625 Hannover, Germany
| | - Brunhilde Wirth
- Institute of Human Genetics, University Hospital of Cologne, University of Cologne, 50931 Cologne, Germany
- Center for Rare Diseases, University Hospital of Cologne, University of Cologne, 50931 Cologne, Germany
- Center for Molecular Medicine Cologne, University of Cologne, 50931 Cologne, Germany
- Institute for Genetics, University of Cologne, 50931 Cologne, Germany
| | - Thomas M. Wishart
- The Roslin Institute and Royal (Dick) School of Veterinary Studies, University of Edinburgh, Midlothian EH25 9RG, UK
- Euan MacDonald Centre, University of Edinburgh, Edinburgh EH16 4SB, UK
| | - Heidi R. Fuller
- School of Pharmacy and Bioengineering (PhaB), Keele University, Keele ST5 5BG, UK
- Wolfson Centre for Inherited Neuromuscular Disease, RJAH Orthopaedic Hospital, Oswestry SY10 7AG, UK
- Correspondence: ; Tel.: +44-(0)1-782-734546
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Wong X, Luperchio TR, Reddy KL. NET gains and losses: the role of changing nuclear envelope proteomes in genome regulation. Curr Opin Cell Biol 2014; 28:105-20. [PMID: 24886773 DOI: 10.1016/j.ceb.2014.04.005] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2014] [Revised: 03/21/2014] [Accepted: 04/11/2014] [Indexed: 01/13/2023]
Abstract
In recent years, our view of the nucleus has changed considerably with an increased awareness of the roles dynamic higher order chromatin structure and nuclear organization play in nuclear function. More recently, proteomics approaches have identified differential expression of nuclear lamina and nuclear envelope transmembrane (NET) proteins. Many NETs have been implicated in a range of developmental disorders as well as cell-type specific biological processes, including genome organization and nuclear morphology. While further studies are needed, it is clear that the differential nuclear envelope proteome contributes to cell-type specific nuclear identity and functions. This review discusses the importance of proteome diversity at the nuclear periphery and highlights the putative roles of NET proteins, with a focus on nuclear architecture.
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Affiliation(s)
- Xianrong Wong
- Johns Hopkins University, School of Medicine, Department of Biological Chemistry and Center for Epigenetics, 855N. Wolfe St., Rangos 574, Baltimore, MD 21044, United States
| | - Teresa R Luperchio
- Johns Hopkins University, School of Medicine, Department of Biological Chemistry and Center for Epigenetics, 855N. Wolfe St., Rangos 574, Baltimore, MD 21044, United States
| | - Karen L Reddy
- Johns Hopkins University, School of Medicine, Department of Biological Chemistry and Center for Epigenetics, 855N. Wolfe St., Rangos 574, Baltimore, MD 21044, United States.
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Genome regulation at the peripheral zone: lamina associated domains in development and disease. Curr Opin Genet Dev 2014; 25:50-61. [PMID: 24556270 DOI: 10.1016/j.gde.2013.11.021] [Citation(s) in RCA: 55] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2013] [Accepted: 11/29/2013] [Indexed: 12/18/2022]
Abstract
The nuclear periphery has been implicated in gene regulation and it has been proposed that proximity to the nuclear lamina and inner nuclear membrane (INM) leads to gene repression. More recently, it appears that there is a correlation and interdependence between lamina associated domains (LADs), the epigenome and overall three-dimensional architecture of the genome. However, the mechanisms of such organization at the 'peripheral zone' and the functional significance of these associations are poorly understood. The role these domains play in development and disease is an active and exciting area of research, expanding our knowledge of how the three-dimensional (3D) genome is regulated.
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Al-Haggar M, Shams A, Madej-Pilarczyk A, Barakat T, Puzianowska-Kuznicka M. Ultrastructural skin changes in Egyptian mandibuloacral dysplasia patients with p.Arg527Leu LMNA mutation and in their asymptomatic heterozygotic mothers. J Clin Pathol 2013; 66:1000-4. [PMID: 23775434 DOI: 10.1136/jclinpath-2013-201690] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
Affiliation(s)
- Mohammad Al-Haggar
- Genetics Unit, Pediatrics Department, Faculty of Medicine, Mansoura University, , Mansoura, Egypt
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5
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Kheterpal I, Ku G, Coleman L, Yu G, Ptitsyn AA, Floyd ZE, Gimble JM. Proteome of human subcutaneous adipose tissue stromal vascular fraction cells versus mature adipocytes based on DIGE. J Proteome Res 2011; 10:1519-27. [PMID: 21261302 PMCID: PMC3070065 DOI: 10.1021/pr100887r] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
Adipose tissue contains a heterogeneous population of mature adipocytes, endothelial cells, immune cells, pericytes, and preadipocytic stromal/stem cells. To date, a majority of proteomic analyses have focused on intact adipose tissue or isolated adipose stromal/stem cells in vitro. In this study, human subcutaneous adipose tissue from multiple depots (arm and abdomen) obtained from female donors was separated into populations of stromal vascular fraction cells and mature adipocytes. Out of 960 features detected by 2-D gel electrophoresis, a total of 200 features displayed a 2-fold up- or down-regulation relative to each cell population. The protein identity of 136 features was determined. Immunoblot analyses comparing SVF relative to adipocytes confirmed that carbonic anhydrase II was up-regulated in both adipose depots while catalase was up-regulated in the arm only. Bioinformatic analyses of the data set determined that cytoskeletal, glycogenic, glycolytic, lipid metabolic, and oxidative stress related pathways were highly represented as differentially regulated between the mature adipocytes and stromal vascular fraction cells. These findings extend previous reports in the literature with respect to the adipose tissue proteome and the consequences of adipogenesis. The proteins identified may have value as biomarkers for monitoring the physiology and pathology of cell populations within subcutaneous adipose depots.
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Affiliation(s)
- Indu Kheterpal
- Proteomics and Metabolomics Core Facility, Louisiana State University System, 6400 Perkins Road, Baton Rouge, LA 70808
- Protein Structural Biology, Louisiana State University System, 6400 Perkins Road, Baton Rouge, LA 70808
| | - Ginger Ku
- Proteomics and Metabolomics Core Facility, Louisiana State University System, 6400 Perkins Road, Baton Rouge, LA 70808
- Protein Structural Biology, Louisiana State University System, 6400 Perkins Road, Baton Rouge, LA 70808
| | - Liana Coleman
- Proteomics and Metabolomics Core Facility, Louisiana State University System, 6400 Perkins Road, Baton Rouge, LA 70808
| | - Gang Yu
- Stem Cell Biology Laboratory, Louisiana State University System, 6400 Perkins Road, Baton Rouge, LA 70808
| | - Andrey A. Ptitsyn
- Center for Bioinformatics, College of Veterinary Medicine and Biomedical Sciences Department of Microbiology Immunology & Pathology, Colorado State University, Fort Collins, CO 80523-1682
| | - Z. Elizabeth Floyd
- Ubiquitin Laboratory, Pennington Biomedical Research Center, Louisiana State University System, 6400 Perkins Road, Baton Rouge, LA 70808
| | - Jeffrey M. Gimble
- Stem Cell Biology Laboratory, Louisiana State University System, 6400 Perkins Road, Baton Rouge, LA 70808
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Scharner J, Brown CA, Bower M, Iannaccone ST, Khatri IA, Escolar D, Gordon E, Felice K, Crowe CA, Grosmann C, Meriggioli MN, Asamoah A, Gordon O, Gnocchi VF, Ellis JA, Mendell JR, Zammit PS. Novel LMNA mutations in patients with Emery-Dreifuss muscular dystrophy and functional characterization of four LMNA mutations. Hum Mutat 2011; 32:152-67. [PMID: 20848652 DOI: 10.1002/humu.21361] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2010] [Accepted: 09/01/2010] [Indexed: 12/20/2022]
Abstract
Mutations in LMNA cause a variety of diseases affecting striated muscle including autosomal Emery-Dreifuss muscular dystrophy (EDMD), LMNA-associated congenital muscular dystrophy (L-CMD), and limb-girdle muscular dystrophy type 1B (LGMD1B). Here, we describe novel and recurrent LMNA mutations identified in 50 patients from the United States and Canada, which is the first report of the distribution of LMNA mutations from a large cohort outside Europe. This augments the number of LMNA mutations known to cause EDMD by 16.5%, equating to an increase of 5.9% in the total known LMNA mutations. Eight patients presented with either p.R249W/Q or p.E358K mutations and an early onset EDMD phenotype: two mutations recently associated with L-CMD. Importantly, 15 mutations are novel and include eight missense mutations (p.R189P, p.F206L, p.S268P, p.S295P, p.E361K, p.G449D, p.L454P, and p.W467R), three splice site mutations (c.IVS4 + 1G>A, c.IVS6 - 2A>G, and c.IVS8 + 1G>A), one duplication/in frame insertion (p.R190dup), one deletion (p.Q355del), and two silent mutations (p.R119R and p.K270K). Analysis of 4 of our lamin A mutations showed that some caused nuclear deformations and lamin B redistribution in a mutation specific manner. Together, this study significantly augments the number of EDMD patients on the database and describes 15 novel mutations that underlie EDMD, which will contribute to establishing genotype-phenotype correlations.
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Affiliation(s)
- Juergen Scharner
- Randall Division of Cell and Molecular Biophysics, King's College London, United Kingdom
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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: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
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8
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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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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: 145] [Impact Index Per Article: 8.1] [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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10
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McClintock D, Gordon LB, Djabali K. Hutchinson-Gilford progeria mutant lamin A primarily targets human vascular cells as detected by an anti-Lamin A G608G antibody. Proc Natl Acad Sci U S A 2006; 103:2154-9. [PMID: 16461887 PMCID: PMC1413759 DOI: 10.1073/pnas.0511133103] [Citation(s) in RCA: 158] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
Hutchinson-Gilford progeria syndrome (HGPS; Online Mendelian Inheritance in Man accession no. 176670) is a rare disorder that is characterized by segmental premature aging and death between 7 and 20 years of age from severe premature atherosclerosis. Mutations in the LMNA gene are responsible for this syndrome. Approximately 80% of HGPS cases are caused by a G608 (GGC-->GGT) mutation within exon 11 of LMNA, which elicits a deletion of 50 aa near the C terminus of prelamin A. In this article, we present evidence that the mutant lamin A (progerin) accumulates in the nucleus in a cellular age-dependent manner. In human HGPS fibroblast cultures, we observed, concomitantly to nuclear progerin accumulation, severe nuclear envelope deformations and invaginations preventable by farnesyltransferase inhibition. Nuclear alterations affect cell-cycle progression and cell migration and elicit premature senescence. Strikingly, skin biopsy sections from a subject with HGPS showed that the truncated lamin A accumulates primarily in the nuclei of vascular cells. This finding suggests that accumulation of progerin is directly involved in vascular disease in progeria.
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Affiliation(s)
- Dayle McClintock
- *Department of Dermatology, College of Physicians and Surgeons, Columbia University, New York, NY 10032; and
| | - Leslie B. Gordon
- Department of Pediatrics, Brown Medical School, Providence, RI 02912
| | - Karima Djabali
- *Department of Dermatology, College of Physicians and Surgeons, Columbia University, New York, NY 10032; and
- To whom correspondence should be addressed. E-mail:
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11
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Paradisi M, McClintock D, Boguslavsky RL, Pedicelli C, Worman HJ, Djabali K. Dermal fibroblasts in Hutchinson-Gilford progeria syndrome with the lamin A G608G mutation have dysmorphic nuclei and are hypersensitive to heat stress. BMC Cell Biol 2005; 6:27. [PMID: 15982412 PMCID: PMC1183198 DOI: 10.1186/1471-2121-6-27] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2004] [Accepted: 06/27/2005] [Indexed: 11/10/2022] Open
Abstract
Background Hutchinson-Gilford progeria syndrome (HGPS, OMIM 176670) is a rare sporadic disorder with an incidence of approximately 1 per 8 million live births. The phenotypic appearance consists of short stature, sculptured nose, alopecia, prominent scalp veins, small face, loss of subcutaneous fat, faint mid-facial cyanosis, and dystrophic nails. HGPS is caused by mutations in LMNA, the gene that encodes nuclear lamins A and C. The most common mutation in subjects with HGPS is a de novo single-base pair substitution, G608G (GGC>GGT), within exon 11 of LMNA. This creates an abnormal splice donor site, leading to expression of a truncated protein. Results We studied a new case of a 5 year-old girl with HGPS and found a heterozygous point mutation, G608G, in LMNA. Complementary DNA sequencing of RNA showed that this mutation resulted in the deletion of 50 amino acids in the carboxyl-terminal tail domain of prelamin A. We characterized a primary dermal fibroblast cell line derived from the subject's skin. These cells expressed the mutant protein and exhibited a normal growth rate at early passage in primary culture but showed alterations in nuclear morphology. Expression levels and overall distributions of nuclear lamins and emerin, an integral protein of the inner nuclear membrane, were not dramatically altered. Ultrastructural analysis of the nuclear envelope using electron microscopy showed that chromatin is in close association to the nuclear lamina, even in areas with abnormal nuclear envelope morphology. The fibroblasts were hypersensitive to heat shock, and demonstrated a delayed response to heat stress. Conclusion Dermal fibroblasts from a subject with HGPS expressing a mutant truncated lamin A have dysmorphic nuclei, hypersensitivity to heat shock, and delayed response to heat stress. This suggests that the mutant protein, even when expressed at low levels, causes defective cell stability, which may be responsible for phenotypic abnormalities in the disease.
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Affiliation(s)
- Mauro Paradisi
- VII Divisione, Dermatologia Pediatrica, Istituto Dermopatico Dell'Immacolata IRCCS, Rome, Italy
| | - Dayle McClintock
- Department of Dermatology, Columbia University, College of Physicians & Surgeons, New York, New York, USA
| | - Revekka L Boguslavsky
- Department of Medicine and Department of Anatomy and Cell Biology, Columbia University, College of Physicians & Surgeons, New York, New York, USA
| | - Christina Pedicelli
- VII Divisione, Dermatologia Pediatrica, Istituto Dermopatico Dell'Immacolata IRCCS, Rome, Italy
| | - Howard J Worman
- Department of Medicine and Department of Anatomy and Cell Biology, Columbia University, College of Physicians & Surgeons, New York, New York, USA
| | - Karima Djabali
- Department of Dermatology, Columbia University, College of Physicians & Surgeons, New York, New York, USA
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Abstract
Nuclear lamins form a fibrous nucleoskeletal network of intermediate-sized filaments that underlies the inner nuclear membrane. It associates with this membrane through interactions with specific integral nuclear membrane proteins, while within this flattened lamin lattice the nuclear pore complexes are embedded. Next to this peripheral network, the lamins can form intranuclear structures. The lamins are the evolutionary progenitors of the cytoplasmic intermediate filament proteins and have profound influences on nuclear structure and function. These influences require that lamins have dynamic properties and dual identities as structural building blocks on the one hand, and transcription regulators on the other. Which of these identities underlies the laminopathies, a myriad of genetic diseases caused by mutations in lamins or lamin-associated proteins, is a topic of intense debate.
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Affiliation(s)
- Jos L V Broers
- Department of Molecular Cell Biology, Research Institutes CARIM, GROW, and EURON, University of Maastricht, The Netherlands
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Nikolova V, Leimena C, McMahon AC, Tan JC, Chandar S, Jogia D, Kesteven SH, Michalicek J, Otway R, Verheyen F, Rainer S, Stewart CL, Martin D, Feneley MP, Fatkin D. Defects in nuclear structure and function promote dilated cardiomyopathy in lamin A/C-deficient mice. J Clin Invest 2004; 113:357-69. [PMID: 14755333 PMCID: PMC324538 DOI: 10.1172/jci19448] [Citation(s) in RCA: 173] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2003] [Accepted: 11/04/2003] [Indexed: 02/01/2023] Open
Abstract
Laminopathies are a group of disorders caused by mutations in the LMNA gene that encodes the nuclear lamina proteins, lamin A and lamin C; their pathophysiological basis is unknown. We report that lamin A/C-deficient (Lmna(-/-)) mice develop rapidly progressive dilated cardiomyopathy (DCM) characterized by left ventricular (LV) dilation and reduced systolic contraction. Isolated Lmna(-/-) myocytes show reduced shortening with normal baseline and peak amplitude of Ca(2+) transients. Lmna(-/-) LV myocyte nuclei have marked alterations of shape and size with central displacement and fragmentation of heterochromatin; these changes are present but less severe in left atrial nuclei. Electron microscopy of Lmna(-/-) cardiomyocytes shows disorganization and detachment of desmin filaments from the nuclear surface with progressive disruption of the cytoskeletal desmin network. Alterations in nuclear architecture are associated with defective nuclear function evidenced by decreased SREBP1 import, reduced PPARgamma expression, and a lack of hypertrophic gene activation. These findings suggest a model in which the primary pathophysiological mechanism in Lmna(-/-) mice is defective force transmission resulting from disruption of lamin interactions with the muscle-specific desmin network and loss of cytoskeletal tension. Despite severe DCM, defects in nuclear function prevent Lmna(-/-) cardiomyocytes from developing compensatory hypertrophy and accelerate disease progression.
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Affiliation(s)
- Vesna Nikolova
- Molecular Cardiology Program, Victor Chang Cardiac Research Institute, Darlinghurst, New South Wales, Australia
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Manilal S, Randles KN, Aunac C, Nguyen MT, Morris GE. A lamin A/C beta-strand containing the site of lipodystrophy mutations is a major surface epitope for a new panel of monoclonal antibodies. Biochim Biophys Acta Gen Subj 2004; 1671:87-92. [PMID: 15026149 DOI: 10.1016/j.bbagen.2004.01.008] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2003] [Revised: 01/28/2004] [Accepted: 01/29/2004] [Indexed: 11/24/2022]
Abstract
Using a phage-displayed peptide library, we have identified the epitope recognized by a new panel of five monoclonal antibodies (mAbs) raised against full-length recombinant human lamin A. The mAbs were found to recognize both lamin A and C by Western blotting and immunolocalization at the nuclear rim. A nine-amino acid consensus sequence PLLTYRFPP in the common immunoglobulin-like (Ig-like) domain of lamin A/C contains the binding site for all five mAbs. Three-dimensional structure of the Ig-like domain of lamin A/C shows this sequence is a complete beta-strand. This sequence includes arginine-482 (R482) which is mutated in most cases of Dunnigan-type familial partial lipodystrophy (FPLD). R482 may be part of an interaction site on the surface of lamin A/C for lamin-binding proteins associated with lipodystrophy.
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Affiliation(s)
- Sushila Manilal
- MRIC Biochemistry Group, North East Wales Institute, Mold Road, Wrexham, LL11 2AW, UK
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15
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Nikolova V, Leimena C, McMahon AC, Tan JC, Chandar S, Jogia D, Kesteven SH, Michalicek J, Otway R, Verheyen F, Rainer S, Stewart CL, Martin D, Feneley MP, Fatkin D. Defects in nuclear structure and function promote dilated cardiomyopathy in lamin A/C–deficient mice. J Clin Invest 2004. [DOI: 10.1172/jci200419448] [Citation(s) in RCA: 287] [Impact Index Per Article: 14.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
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16
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Capanni C, Cenni V, Mattioli E, Sabatelli P, Ognibene A, Columbaro M, Parnaik VK, Wehnert M, Maraldi NM, Squarzoni S, Lattanzi G. Failure of lamin A/C to functionally assemble in R482L mutated familial partial lipodystrophy fibroblasts: altered intermolecular interaction with emerin and implications for gene transcription. Exp Cell Res 2003; 291:122-34. [PMID: 14597414 DOI: 10.1016/s0014-4827(03)00395-1] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Familial partial lipodystrophy is an autosomal dominant disease caused by mutations of the LMNA gene encoding alternatively spliced lamins A and C. Abnormal distribution of body fat and insulin resistance characterize the clinical phenotype. In this study, we analyzed primary fibroblast cultures from a patient carrying an R482L lamin A/C mutation by a morphological and biochemical approach. Abnormalities were observed consisting of nuclear lamin A/C aggregates mostly localized close to the nuclear lamina. These aggregates were not bound to either DNA-containing structures or RNA splicing intranuclear compartments. In addition, emerin did not colocalize with nuclear lamin A/C aggregates. Interestingly, emerin failed to interact with lamin A in R482L mutated fibroblasts in vivo, while the interaction with lamin C was preserved in vitro, as determined by coimmunoprecipitation experiments. The presence of lamin A/C nuclear aggregates was restricted to actively transcribing cells, and it was increased in insulin-treated fibroblasts. In fibroblasts carrying lamin A/C nuclear aggregates, a reduced incorporation of bromouridine was observed, demonstrating that mutated lamin A/C in FPLD cells interferes with RNA transcription.
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Affiliation(s)
- Cristina Capanni
- Laboratory of Cell Biology, Istituti Ortopedici Rizzoli, Bologna, Italy
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17
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Holt I, Ostlund C, Stewart CL, Man NT, Worman HJ, Morris GE. Effect of pathogenic mis-sense mutations in lamin A on its interaction with emerin in vivo. J Cell Sci 2003; 116:3027-35. [PMID: 12783988 DOI: 10.1242/jcs.00599] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Mutations in lamin A/C can cause Emery-Dreifuss muscular dystrophy (EDMD) or a related cardiomyopathy (CMD1A). Using transfection of lamin-A/C-deficient fibroblasts, we have studied the effects of nine pathogenic mutations on the ability of lamin A to assemble normally and to localize emerin normally at the nuclear rim. Five mutations in the rod domain (L85R, N195K, E358K, M371K and R386K) affected the assembly of the lamina. With the exception of mutant L85R, all rod domain mutants induced the formation of large nucleoplasmic foci in about 10% of all nuclei. The presence of emerin in these foci suggests that the interaction of lamin A with emerin is not directly affected by the rod domain mutations. Three mutations in the tail region, R453W, W520S and R527P, might directly affect emerin binding by disrupting the structure of the putative emerin-binding site, because mutant lamin A localized normally to the nuclear rim but its ability to trap emerin was impaired. Nucleoplasmic foci rarely formed in these three cases (<2%) but, when they did so, emerin was absent, consistent with a direct effect of the mutations on emerin binding. The lipodystrophy mutation R482Q, which causes a different phenotype and is believed to act through an emerin-independent mechanism, was indistinguishable from wild-type in its localization and its ability to trap emerin at the nuclear rim. The novel hypothesis suggested by the data is that EDMD/CMD1A mutations in the tail domain of lamin A/C work by direct impairment of emerin interaction, whereas mutations in the rod region cause defective lamina assembly that might or might not impair emerin capture at the nuclear rim. Subtle effects on the function of the lamina-emerin complex in EDMD/CMD1A patients might be responsible for the skeletal and/or cardiac muscle phenotype.
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Affiliation(s)
- Ian Holt
- Biochemistry Group, North East Wales Institute, Wrexham LL11 2AW, UK
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18
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Wilkinson FL, Holaska JM, Zhang Z, Sharma A, Manilal S, Holt I, Stamm S, Wilson KL, Morris GE. Emerin interacts in vitro with the splicing-associated factor, YT521-B. EUROPEAN JOURNAL OF BIOCHEMISTRY 2003; 270:2459-66. [PMID: 12755701 DOI: 10.1046/j.1432-1033.2003.03617.x] [Citation(s) in RCA: 78] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Emerin is a nuclear membrane protein that interacts with lamin A/C at the nuclear envelope. Mutations in either emerin or lamin A/C cause Emery-Dreifuss muscular dystrophy (EDMD). The functions of emerin are poorly understood, but EDMD affects mainly skeletal and cardiac muscle. We used a high-stringency yeast two-hybrid method to screen a human heart cDNA library, with full-length emerin as bait. Four out of five candidate interactors identified were nuclear proteins: lamin A, splicing factor YT521-B, proteasome subunit PA28 gamma and transcription factor vav-1. Specific binding between emerin and the functional C-terminal domain of YT521-B was confirmed by pull-down assays and biomolecular interaction analysis (BIAcore). Inhibition by emerin of YT521-B-dependent splice site selection in vivo suggests that the interaction is physiologically significant. A 'bipartite' binding site for YT521-B in emerin was identified using alanine substitution or disease-associated mutations in emerin. The transcription factor GCL (germ cell-less) has previously been shown to bind to the same site. The results are consistent with an emerging view that lamins and lamina-associated proteins, like emerin, have a regulatory role, as well as a structural role in the nucleus. YT521-B joins a growing list of candidates for a role in a gene expression model of the pathogenesis of EDMD.
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Abstract
Several neuromuscular diseases are caused by mutations in emerin and A-type lamins, proteins of the nuclear envelope. Emery-Dreifuss muscular dystrophy is caused by mutations in emerin (X-linked) or A-type lamins (autosomal dominant). Mutations in A-type lamins also cause limb-girdle muscular dystrophy type 1B, dilated cardiomyopathy with conduction defect, and Charcot-Marie-Tooth disorder type 2B1. They also cause partial lipodystrophy syndromes. The functions of emerin and A-type lamins and the mechanisms of how mutations in these proteins cause tissue-specific diseases are not well understood. The mutated proteins may cause structural damage to cells but may also affect processes such as gene regulation. This review gives an overview of this topic and describes recent advances in identification of disease-causing mutations, studies of cells and tissues from subjects with these diseases, and animal and cell culture models.
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Affiliation(s)
- Cecilia Ostlund
- Department of Medicine, College of Physicians and Surgeons, Columbia University, 630 West 168th Street, Tenth Floor, New York, New York 10032, USA
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20
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Affiliation(s)
- Elif Arioglu Oral
- Department of Internal Medicine, Division of Endocrinology and Metabolism, University of Michigan, Ann Arbor, MI 48109, USA.
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21
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Aronson IK, Fiedler VC. Of mice and men: the road to understanding the complex nature of adipose tissue and lipoatrophy. ARCHIVES OF DERMATOLOGY 2003; 139:81-3. [PMID: 12533172 DOI: 10.1001/archderm.139.1.81] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Affiliation(s)
- Iris K Aronson
- University of Illinois, Department of Dermatology, College of Medicine, Chicago 60612, USA
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22
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Abstract
Inherited disorders of the nuclear lamina present some of the most intriguing puzzles in cell biology. Mutations in lamin A and lamin C - nuclear intermediate filament proteins that are expressed in nearly all somatic cells - cause tissue-specific diseases that affect striated muscle, adipose tissue and peripheral nerve or skeletal development. Recent studies provide clues about how different mutations in these proteins cause either muscle disease or partial lipodystrophy. Although the precise pathogenic mechanisms are currently unknown, the involvement of lamins in several different disorders shows that research on the nuclear lamina will shed light on common human pathologies.
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Affiliation(s)
- Howard J Worman
- Dept of Medicine, College of Physicians and Surgeons, Columbia University, New York, NY 10032, USA.
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23
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Abstract
We have assembled references of 700 articles published in 2001 that describe work performed using commercially available optical biosensors. To illustrate the technology's diversity, the citation list is divided into reviews, methods and specific applications, as well as instrument type. We noted marked improvements in the utilization of biosensors and the presentation of kinetic data over previous years. These advances reflect a maturing of the technology, which has become a standard method for characterizing biomolecular interactions.
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Affiliation(s)
- Rebecca L Rich
- Center for Biomolecular Interaction Analysis, University of Utah, Salt Lake City, UT 84132, USA
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24
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Abstract
Intermediate filament (IF) proteins are the building blocks of cytoskeletal filaments, the main function of which is to maintain cell shape and integrity. The lamins are thought to be the evolutionary progenitors of IF proteins and they have profound influences on both nuclear structure and function. These influences require the lamins to have dynamic properties and dual identities--as building blocks and transcriptional regulators. Which one of these identities underlies a myriad of genetic diseases is a topic of intense debate.
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Affiliation(s)
- Christopher J Hutchison
- Department of Biological and Biomedical Sciences, University of Durham, South Road, Durham DH1 3LE, UK.
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25
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Abstract
The nuclear lamina is composed of both A- and B-type lamins and lamin-binding proteins. Many lamin-binding proteins are integral proteins of the inner nuclear membrane. Lamins and inner nuclear membrane proteins are important for a variety of cell functions, including nuclear assembly, replication, transcription, and nuclear integrity. Recent advances in the field in the past year include the identification of a family of spectrin-repeat-containing inner nuclear membrane proteins and other novel inner-membrane proteins, and the discovery of a nuclear membrane fusion complex. There is also growing evidence that A- and B-type lamins and their binding partners have distinct roles during nuclear assembly and interphase.
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Affiliation(s)
- James M Holaska
- Department of Cell Biology, The Johns Hopkins University School of Medicine, 725 North Wolfe Street, Baltimore, MD 21205, USA
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26
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Krimm I, Ostlund C, Gilquin B, Couprie J, Hossenlopp P, Mornon JP, Bonne G, Courvalin JC, Worman HJ, Zinn-Justin S. The Ig-like structure of the C-terminal domain of lamin A/C, mutated in muscular dystrophies, cardiomyopathy, and partial lipodystrophy. Structure 2002; 10:811-23. [PMID: 12057196 DOI: 10.1016/s0969-2126(02)00777-3] [Citation(s) in RCA: 210] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Lamins are nuclear intermediate filaments that, together with lamin-associated proteins, maintain nuclear shape and provide a structural support for chromosomes and replicating DNA. We have determined the solution structure of the human lamin A/C C-terminal globular domain which contains specific mutations causing four different heritable diseases. This domain encompasses residues 430-545 and adopts an Ig-like fold of type s. We have also characterized by NMR and circular dichroism the structure and thermostability of three mutants, R453W and R482W/Q, corresponding to "hot spots" causing Emery-Dreifuss muscular dystrophy and Dunnigan-type lipodystrophy, respectively. Our structure determination and mutant analyses clearly show that the consequences of the mutations causing muscle-specific diseases or lipodystrophy are different at the molecular level.
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Affiliation(s)
- Isabelle Krimm
- Département d'Ingénierie et d'Etudes des Protéines, CEA Saclay, 91191, Gif-sur-Yvette, France
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27
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Bonne G, Capeau J, De Visser M, Duboc D, Merlini L, Morris GE, Muntoni F, Recan D, Sewry C, Squarzoni S, Stewart C, Talim B, van der Kooi A, Worman H, Schwartz K. 82nd ENMC international workshop, 5th international Emery-Dreifuss muscular dystrophy (EDMD) workshop, 1st Workshop of the MYO-CLUSTER project EUROMEN (European muscle envelope nucleopathies), 15-16 September 2000, Naarden, The Netherlands. Neuromuscul Disord 2002; 12:187-94. [PMID: 11738362 DOI: 10.1016/s0960-8966(01)00243-7] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Affiliation(s)
- Gisèle Bonne
- INSERM UR523-Institut de Myologie, Bâtiment Babinski, G.H. Pitié-Salpétrière, 47, Boulevard de l'Hôpital, 75651 Paris Cedex 13, France.
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28
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Vigouroux C, Auclair M, Dubosclard E, Pouchelet M, Capeau J, Courvalin JC, Buendia B. Nuclear envelope disorganization in fibroblasts from lipodystrophic patients with heterozygous R482Q/W mutations in the lamin A/C gene. J Cell Sci 2001; 114:4459-68. [PMID: 11792811 DOI: 10.1242/jcs.114.24.4459] [Citation(s) in RCA: 168] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Dunnigan-type familial partial lipodystrophy (FPLD), characterized by an abnormal body fat redistribution with insulin resistance, is caused by missense heterozygous mutations in A-type lamins (lamins A and C). A- and B-type lamins are ubiquitous intermediate filament proteins that polymerize at the inner face of the nuclear envelope. We have analyzed primary cultures of skin fibroblasts from three patients harboring R482Q or R482W mutations. These cells were euploid and able to cycle and divide. A subpopulation of these cells had abnormal blebbing nuclei with A-type lamins forming a peripheral meshwork, which was frequently disorganized. Inner nuclear membrane protein emerin, an A-type lamin-binding protein, strictly colocalized with this abnormal meshwork. Cells from lipodystrophic patients often had other nuclear envelope defects, mainly consisting of nuclear envelope herniations that were deficient in B-type lamins, nuclear pore complexes, lamina-associated protein 2 beta, and chromatin. The mechanical properties of nuclear envelopes were altered, as judged from the extensive deformations observed in nuclei from heat-shocked cells, and from the low stringency of extraction of their components. These structural nuclear alterations were caused by the lamins A/C mutations, as the same changes were introduced in human control fibroblasts by ectopic expression of R482W mutated lamin A.
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Affiliation(s)
- C Vigouroux
- INSERM U. 402, Faculté de Médecine Saint-Antoine, 75012 Paris, France
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29
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Raharjo WH, Enarson P, Sullivan T, Stewart CL, Burke B. Nuclear envelope defects associated withLMNAmutations cause dilated cardiomyopathy and Emery-Dreifuss muscular dystrophy. J Cell Sci 2001; 114:4447-57. [PMID: 11792810 DOI: 10.1242/jcs.114.24.4447] [Citation(s) in RCA: 155] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Nuclear lamin A and C alleles that are linked to three distinct human diseases have been expressed both in HeLa cells and in fibroblasts derived from Lmna null mice. Point mutations that cause dilated cardiomyopathy (L85R and N195K) and autosomal dominant Emery-Dreifuss muscular dystrophy (L530P) modify the assembly properties of lamins A and C and cause partial mislocalization of emerin, an inner nuclear membrane protein, in HeLa cells. At the same time, these mutant lamins interfere with the targeting and assembly of endogenous lamins and in this way may cause significant changes in the molecular organization of the nuclear periphery. By contrast, lamin A and C molecules harboring a point mutation (R482W), which gives rise to a dominant form of familial partial lipodystrophy, behave in a manner that is indistinguishable from wild-type lamins A and C, at least with respect to targeting and assembly within the nuclear lamina. Taken together, these results suggest that nuclear structural defects could contribute to the etiology of both dilated cardiomyopathy and autosomal dominant Emery-Dreifuss muscular dystrophy.
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Affiliation(s)
- W H Raharjo
- Department of Cell Biology and Anatomy, University of Calgary, 3330 Hospital Drive NW, Calgary, Alberta T2N 4N1, Canada
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30
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Ostlund C, Bonne G, Schwartz K, Worman HJ. Properties of lamin A mutants found in Emery-Dreifuss muscular dystrophy, cardiomyopathy and Dunnigan-type partial lipodystrophy. J Cell Sci 2001; 114:4435-45. [PMID: 11792809 DOI: 10.1242/jcs.114.24.4435] [Citation(s) in RCA: 146] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Autosomal dominant Emery-Dreifuss muscular dystrophy is caused by mutations in the LMNA gene, which encodes lamin A and lamin C. Mutations in this gene also give rise to limb girdle muscular dystrophy type 1B, dilated cardiomyopathy with atrioventricular conduction defect and Dunnigan-type partial lipodystrophy. The properties of the mutant lamins that cause muscular dystrophy, lipodystrophy and dilated cardiomyopathy are not known. We transfected C2C12 myoblasts with cDNA encoding wild-type lamin A and 15 mutant forms found in patients affected by these diseases. Immunofluorescence microscopy showed that four mutants, N195K, E358K, M371K and R386K, could have a dramatically aberrant localization, with decreased nuclear rim staining and formation of intranuclear foci. The distributions of endogenous lamin A/C, lamin B1 and lamin B2 were also altered in cells expressing these four mutants and three of them caused a loss of emerin from the nuclear envelope. In the yeast two-hybrid assay, the 15 lamin A mutants studied interacted with themselves and with wild-type lamin A and lamin B1. Pulse-chase experiments showed no decrease in the stability of several representative lamin A mutants compared with wild-type. These results indicate that some lamin A mutants causing disease can be aberrantly localized, partially disrupt the endogenous lamina and alter emerin localization, whereas others localize normally in transfected cells.
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Affiliation(s)
- C Ostlund
- Department of Medicine, College of Physicians and Surgeons, Columbia University, New York, NY 10032, USA
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31
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Abstract
The X-linked form of Emery-Dreifuss muscular dystrophy (X-EDMD) is caused by absence, or greatly reduced amounts, of the inner nuclear-membrane protein, emerin. The autosomal dominant form (AD-EDMD) is caused by missense mutations in lamins A and C, two components of the nuclear lamina that interact directly with emerin. Lamin A/C mutations also cause one form of dilated cardiomyopathy (CMD1A) and one form of limb-girdle muscular dystrophy (LGMD1B), both of which have clinical features in common with EDMD, as well as a rare, unrelated form of lipodystrophy (FPLD). Evidence is now emerging that defective assembly of the nuclear lamina is a feature of all these diseases, although not necessarily the direct cause. Why only heart and skeletal muscle, and possibly connective tissue, are affected in EDMD and why expression of the disease is so extremely variable between individuals remains to be explained.
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Affiliation(s)
- G E Morris
- MRIC Biochemistry Group, The North East Wales Institute, Wrexham, UK LL11 2AW.
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32
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Holt I, Clements L, Manilal S, Morris GE. How does a g993t mutation in the emerin gene cause Emery-Dreifuss muscular dystrophy? Biochem Biophys Res Commun 2001; 287:1129-33. [PMID: 11587540 DOI: 10.1006/bbrc.2001.5708] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
X-linked Emery-Dreifuss muscular dystrophy is usually caused by absence of the nuclear membrane protein, emerin, due to nonsense mutations or deletions, but a few missense mutations also exist. A pathogenic g993t mutation causes a Q133H change in the nuclear targeting region of emerin, but it may also reduce emerin levels by affecting mRNA splicing. We have introduced the g993t mutation by in vitro mutagenesis and studied the effect of Q133H on nuclear targeting by transfection of COS-7 cells. No qualitative or quantitative differences in nuclear targeting were observed between normal and mutant emerin. Quantitative BIAcore analysis showed no significant change in lamin A binding to emerin when the mutation was present. We conclude that Q133 is not essential for nuclear targeting of emerin or its interaction with lamin A. Reduced emerin levels due to altered splicing or defective interaction with an unidentified binding partner remain possible pathogenic mechanisms.
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Affiliation(s)
- I Holt
- MRIC Biochemistry Group, North East Wales Institute, Mold Road, Wrexham, Wales, LL11 2AW, United Kingdom
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