1
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Li P, Rietscher K, Jopp H, Magin TM, Omary MB. Posttranslational modifications of keratins and their associated proteins as therapeutic targets in keratin diseases. Curr Opin Cell Biol 2023; 85:102264. [PMID: 37925932 DOI: 10.1016/j.ceb.2023.102264] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2023] [Revised: 09/04/2023] [Accepted: 09/24/2023] [Indexed: 11/07/2023]
Abstract
The keratin cytoskeleton protects epithelia against mechanical, nonmechanical, and physical stresses, and participates in multiple signaling pathways that regulate cell integrity and resilience. Keratin gene mutations cause multiple rare monoallelic epithelial diseases termed keratinopathies, including the skin diseases Epidermolysis Bullosa Simplex (EBS) and Pachyonychia Congenita (PC), with limited available therapies. The disease-related keratin mutations trigger posttranslational modifications (PTMs) in keratins and their associated proteins that can aggravate the disease. Recent findings of drug high-throughput screening have led to the identification of compounds that may be repurposed, since they are used for other human diseases, to treat keratinopathies. These drugs target unique PTM pathways and sites, including phosphorylation and acetylation of keratins and their associated proteins, and have shed insights into keratin regulation and interactions. They also offer the prospect of testing the use of drug mixtures, with the long view of possible beneficial human use coupled with increased efficacy and lower side effects.
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Affiliation(s)
- Pei Li
- Center for Advanced Biotechnology and Medicine, Rutgers University, Piscataway, NJ, USA
| | - Katrin Rietscher
- Division of Cell and Developmental Biology, Institute of Biology, Leipzig University, Leipzig, Germany
| | - Henriette Jopp
- Division of Cell and Developmental Biology, Institute of Biology, Leipzig University, Leipzig, Germany
| | - Thomas M Magin
- Division of Cell and Developmental Biology, Institute of Biology, Leipzig University, Leipzig, Germany.
| | - M Bishr Omary
- Center for Advanced Biotechnology and Medicine, Rutgers University, Piscataway, NJ, USA.
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2
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Kiener S, Mauldin EA, Jagannathan V, Casal ML, Leeb T. KRT5 missense variant in a Cardigan Welsh Corgi with epidermolysis bullosa simplex. Anim Genet 2022; 53:892-896. [PMID: 36004757 PMCID: PMC9804678 DOI: 10.1111/age.13257] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2022] [Revised: 07/19/2022] [Accepted: 08/17/2022] [Indexed: 01/09/2023]
Abstract
Epidermolysis bullosa (EB) is a group of blistering disorders that includes several subtypes, classified according to their level of cleavage. Typical clinical signs are blisters and erosions resulting from minimal trauma. The disease has been described in many mammalian species and pathogenic variants in at least 18 different genes have been identified. In the present study, we investigated a Cardigan Welsh Corgi with congenital clinical signs consistent with epidermolysis bullosa. The puppy had blisters and erosions on the paw pads, and the oral mucosa. Histologic examination demonstrated the typical clefting between the dermis and epidermis and confirmed the clinical suspicion. We obtained whole genome sequencing data from the affected puppy and searched for variants in candidate genes known to cause EB. This revealed a heterozygous missense variant, KRT5:p.(E476K), affecting the highly conserved KLLEGE motif of keratin 5. The mutant allele in the affected puppy arose owing to a de novo mutation event as it was absent from both unaffected parents. Knowledge of the functional impact of KRT5 variants in other species together with the demonstration of the de novo mutation event establishes KRT5:p.(E476K) as causative variant for the observed EBS.
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Affiliation(s)
- Sarah Kiener
- Vetsuisse Faculty, Institute of GeneticsUniversity of BernBernSwitzerland,DermFocusUniversity of BernBernSwitzerland
| | - Elizabeth A. Mauldin
- School of Veterinary MedicineUniversity of PennsylvaniaPhiladelphiaPennsylvaniaUSA
| | - Vidhya Jagannathan
- Vetsuisse Faculty, Institute of GeneticsUniversity of BernBernSwitzerland,DermFocusUniversity of BernBernSwitzerland
| | - Margret L. Casal
- School of Veterinary MedicineUniversity of PennsylvaniaPhiladelphiaPennsylvaniaUSA
| | - Tosso Leeb
- Vetsuisse Faculty, Institute of GeneticsUniversity of BernBernSwitzerland,DermFocusUniversity of BernBernSwitzerland
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3
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Badowski C, Tan TS, Aliev T, Trudil D, Larina M, Argentova V, Firdaus MJ, Benny P, Woo VS, Lane EB. Detrimental Effects of IFN-γ on an Epidermolysis Bullosa Simplex Cell Model and Protection by a Humanized Anti-IFN-γ Monoclonal Antibody. JID INNOVATIONS 2022; 2:100096. [PMID: 35265936 PMCID: PMC8899047 DOI: 10.1016/j.xjidi.2022.100096] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2021] [Revised: 10/14/2021] [Accepted: 11/17/2021] [Indexed: 12/12/2022] Open
Abstract
Epidermolysis bullosa is a group of severe skin blistering disorders, which currently have no cure. The pathology of epidermolysis bullosa is recognized as having an inflammatory component, but the role of inflammation in different epidermolysis bullosa disorders is unclear. Epidermolysis bullosa simplex (EBS) is primarily caused by sequence variants in keratin genes; its most severe form, EBS generalized severe, is characterized by aggregates of keratin proteins, and cell models of EBS generalized severe show constitutively elevated stress. IFN-γ is a major mediator of inflammation, and we show that the addition of IFN-γ alone to disease model keratinocytes promotes keratin aggregation, decreases cell-cell junctions, delays wound closure, and reduces cell proliferation. IFN-γ exposure weakens the intercellular cohesion of monolayers on mechanical stress, with IFN-γ-treated EBS monolayers more fragmented than IFN-γ-treated wild-type monolayers. A humanized monoclonal antibody to IFN-γ neutralized the detrimental effects on keratinocytes, restoring cell proliferation, increasing cell-cell adhesion, accelerating wound closure in the presence of IFN-γ, and reducing IFN-γ-mediated keratin aggregation in EBS cells. These suggest that treatment with IFN-γ blocking antibodies may constitute a promising new therapeutic strategy for patients with EBS and may also have ameliorating effects on other inflammatory skin diseases.
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Affiliation(s)
- Cedric Badowski
- Institute of Medical Biology, Agency for Science, Technology and Research (ASTAR), Singapore, Singapore
| | - Tong San Tan
- Institute of Medical Biology, Agency for Science, Technology and Research (ASTAR), Singapore, Singapore
- Skin Research Institute of Singapore (SRIS), Agency for Science, Technology and Research (ASTAR), Singapore, Singapore
| | - Teimur Aliev
- Faculty of Chemistry, Lomonosov Moscow State University, Moscow, Russia
| | - David Trudil
- NHDetect Corporation, Reisterstown, Maryland, USA
| | - Maria Larina
- Shemyakin–Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Moscow, Russia
| | | | - Muhammad Jasrie Firdaus
- Institute of Medical Biology, Agency for Science, Technology and Research (ASTAR), Singapore, Singapore
- Skin Research Institute of Singapore (SRIS), Agency for Science, Technology and Research (ASTAR), Singapore, Singapore
- Lee Kong Chian School of Medicine, Nanyang Technological University, Singapore, Singapore
| | - Paula Benny
- Institute of Medical Biology, Agency for Science, Technology and Research (ASTAR), Singapore, Singapore
| | - Vivien S.T. Woo
- Institute of Medical Biology, Agency for Science, Technology and Research (ASTAR), Singapore, Singapore
- Department of Pathology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, Singapore
| | - E. Birgitte Lane
- Institute of Medical Biology, Agency for Science, Technology and Research (ASTAR), Singapore, Singapore
- Skin Research Institute of Singapore (SRIS), Agency for Science, Technology and Research (ASTAR), Singapore, Singapore
- Department of Pathology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, Singapore
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4
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Kocher T, Koller U. Advances in gene editing strategies for epidermolysis bullosa. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2021; 182:81-109. [PMID: 34175052 DOI: 10.1016/bs.pmbts.2020.12.007] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Epidermolysis bullosa represents a monogenetic disease comprising a variety of heterogeneous mutations in at least 16 genes encoding structural proteins crucial for skin integrity. Due to well-defined mutations but still lacking causal treatment options for the disease, epidermolysis bullosa represents an ideal candidate for gene therapeutic interventions. Recent developments and improvements in the genome editing field have paved the way for the translation of various gene repair strategies into the clinic. With the ability to accurately predict and monitor targeting events within the human genome, the translation might soon be possible. Here, we describe current advancements in the genome editing field for epidermolysis bullosa, along with a discussion of aspects and strategies for precise and personalized gene editing-based medicine, in order to develop efficient and safe ex vivo as well as in vivo genome editing therapies for epidermolysis bullosa patients in the future.
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Affiliation(s)
- Thomas Kocher
- EB House Austria, Research Program for Molecular Therapy of Genodermatoses, Department of Dermatology and Allergology, University Hospital of the Paracelsus Medical University Salzburg, Salzburg, Austria
| | - Ulrich Koller
- EB House Austria, Research Program for Molecular Therapy of Genodermatoses, Department of Dermatology and Allergology, University Hospital of the Paracelsus Medical University Salzburg, Salzburg, Austria.
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5
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Lee CH, Kim MS, Li S, Leahy DJ, Coulombe PA. Structure-Function Analyses of a Keratin Heterotypic Complex Identify Specific Keratin Regions Involved in Intermediate Filament Assembly. Structure 2020; 28:355-362.e4. [PMID: 31995743 DOI: 10.1016/j.str.2020.01.002] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2019] [Revised: 10/20/2019] [Accepted: 01/07/2020] [Indexed: 11/29/2022]
Abstract
Intermediate filaments (IFs) provide vital mechanical support in a broad array of cell types. Interference with this role causes cell fragility and accounts for a large number of human diseases. Gaining an understanding of the structure of IFs is paramount to understanding their function and designing therapeutic agents for relevant diseases. Here, we report the 2.6-Å resolution crystal structure of a complex of interacting 2B domains of keratin 5 (K5) and K14. K5 and K14 form a long-range, left-handed coiled coil, with participating α helices aligned in parallel and in register. Follow-up mutagenesis revealed that specific contacts between interacting 2B domains play a crucial role during 10-nm IF assembly, likely at the step of octamer-octamer association. The resulting structural model represents an atomic-resolution visualization of 2B-2B interactions important to filament assembly and provides insight into the defects introduced by mutations in IF genes associated with human skin diseases.
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Affiliation(s)
- Chang-Hun Lee
- Department of Biochemistry and Molecular Biology, Bloomberg School of Public Health, Johns Hopkins University, Baltimore, MD 21205, USA
| | - Min-Sung Kim
- Integrative Bioscience and Biotechnology, Pohang University of Science and Technology, Pohang, Gyeongbuk 37673, Republic of Korea
| | - Shuang Li
- Department of Biochemistry and Molecular Biology, Bloomberg School of Public Health, Johns Hopkins University, Baltimore, MD 21205, USA
| | - Daniel J Leahy
- Department of Molecular Biosciences, College of Natural Sciences, The University of Texas at Austin, Austin, TX 78712, USA
| | - Pierre A Coulombe
- Department of Biochemistry and Molecular Biology, Bloomberg School of Public Health, Johns Hopkins University, Baltimore, MD 21205, USA; Department of Cell and Developmental Biology, University of Michigan Medical School, Ann Arbor, MI 48109, USA; Department of Dermatology, University of Michigan Medical School, Ann Arbor, MI 48109, USA.
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6
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Zhang J, Ding Y, Li M, Yao Z, Zhuang Y. Known and novel mutations responsible for epidermolysis bullosa simplex cases in a Chinese population. Exp Ther Med 2019; 18:4661-4664. [PMID: 31772641 PMCID: PMC6862070 DOI: 10.3892/etm.2019.8130] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2019] [Accepted: 10/10/2019] [Indexed: 11/20/2022] Open
Abstract
Epidermolysis bullosa simplex, generalized severe (EBS-gen sev) is one of the major forms of EBS, caused by mutations of the keratin 5 (KRT5) or keratin 14 (KRT14). However, it is rarely reported in the Chinese population. The current study was performed on three unrelated Chinese families with five patients clinically suspicious for distinct stages of EBS. Mutation screening was performed by direct sequencing of the entire coding regions of KRT5 and KRT14 genes. A diagnosis of EBS-gen sev for patients in these three families was confirmed by revealing missense mutations c.373C>T (p.Arg125Cys), c.374G>T (p.Arg125Leu), and a novel frameshift mutation c.1231delG (p.Glu411Argfs*31) in KRT14. Considering two previously reported cases and the results of the current report, amino acid residue 125 is likely the most frequent hotspot of EBS-gen sev in the Chinese population. The current study further indicated that the symptoms of EBS-gen sev patients decline with age.
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Affiliation(s)
- Jia Zhang
- Department of Dermatology, Xinhua Hospital Affiliated to Shanghai Jiaotong University School of Medicine, Shanghai 200092, P.R. China
| | - Yu Ding
- Dermatology Department, Mianyang Central Hospital, Mianyang, Sichuan 621000, P.R. China
| | - Ming Li
- Department of Dermatology, Xinhua Hospital Affiliated to Shanghai Jiaotong University School of Medicine, Shanghai 200092, P.R. China
| | - Zhirong Yao
- Department of Dermatology, Xinhua Hospital Affiliated to Shanghai Jiaotong University School of Medicine, Shanghai 200092, P.R. China
| | - Yin Zhuang
- Department of Dermatology, Xinhua Hospital Affiliated to Shanghai Jiaotong University School of Medicine, Shanghai 200092, P.R. China
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7
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Aushev M, Koller U, Mussolino C, Cathomen T, Reichelt J. Traceless Targeting and Isolation of Gene-Edited Immortalized Keratinocytes from Epidermolysis Bullosa Simplex Patients. MOLECULAR THERAPY-METHODS & CLINICAL DEVELOPMENT 2017; 6:112-123. [PMID: 28765827 PMCID: PMC5527154 DOI: 10.1016/j.omtm.2017.06.008] [Citation(s) in RCA: 36] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/31/2017] [Accepted: 06/30/2017] [Indexed: 12/20/2022]
Abstract
Epidermolysis bullosa simplex (EBS) is a blistering skin disease caused by dominant-negative mutations in either KRT5 or KRT14, resulting in impairment of keratin filament structure and epidermal fragility. Currently, nearly 200 mutations distributed across the entire length of these genes are known to cause EBS. Genome editing using programmable nucleases enables the development of ex vivo gene therapies for dominant-negative genetic diseases. A clinically feasible strategy involves the disruption of the mutant allele while leaving the wild-type allele unaffected. Our aim was to develop a traceless approach to efficiently disrupt KRT5 alleles using TALENs displaying unbiased monoallelic disruption events and devise a strategy that allows for subsequent screening and isolation of correctly modified keratinocyte clones without the need for selection markers. Here we report on TALENs that efficiently disrupt the KRT5 locus in immortalized patient-derived EBS keratinocytes. Inactivation of the mutant allele using a TALEN working at sub-optimal levels resulted in restoration of intermediate filament architecture. This approach can be used for the functional inactivation of any mutant keratin allele regardless of the position of the mutation within the gene and is furthermore applicable to the treatment of other inherited skin disorders.
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Affiliation(s)
- Magomet Aushev
- Wellcome Trust Centre for Mitochondrial Research, Institute of Genetic Medicine, Biomedicine West Wing, Centre for Life, Times Square, Newcastle upon Tyne NE1 3BZ, UK
| | - Ulrich Koller
- EB House Austria, Research Program for Molecular Therapy of Genodermatoses and Department of Dermatology, University Hospital of the Paracelsus Medical University Salzburg, 5020 Salzburg, Austria
| | - Claudio Mussolino
- Institute for Transfusion Medicine and Gene Therapy, Medical Center - University of Freiburg, Hugstetter Strasse 55, 79106 Freiburg, Germany.,Center for Chronic Immunodeficiency, Medical Center - University of Freiburg, Breisacherstrasse 115, 79106 Freiburg, Germany.,Faculty of Medicine, University of Freiburg, 79106 Freiburg, Germany
| | - Toni Cathomen
- Institute for Transfusion Medicine and Gene Therapy, Medical Center - University of Freiburg, Hugstetter Strasse 55, 79106 Freiburg, Germany.,Center for Chronic Immunodeficiency, Medical Center - University of Freiburg, Breisacherstrasse 115, 79106 Freiburg, Germany.,Faculty of Medicine, University of Freiburg, 79106 Freiburg, Germany
| | - Julia Reichelt
- EB House Austria, Research Program for Molecular Therapy of Genodermatoses and Department of Dermatology, University Hospital of the Paracelsus Medical University Salzburg, 5020 Salzburg, Austria
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8
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Consequences of Keratin Phosphorylation for Cytoskeletal Organization and Epithelial Functions. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2017; 330:171-225. [DOI: 10.1016/bs.ircmb.2016.09.005] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
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9
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Chen R, Shi L, Hakenberg J, Naughton B, Sklar P, Zhang J, Zhou H, Tian L, Prakash O, Lemire M, Sleiman P, Cheng WY, Chen W, Shah H, Shen Y, Fromer M, Omberg L, Deardorff MA, Zackai E, Bobe JR, Levin E, Hudson TJ, Groop L, Wang J, Hakonarson H, Wojcicki A, Diaz GA, Edelmann L, Schadt EE, Friend SH. Analysis of 589,306 genomes identifies individuals resilient to severe Mendelian childhood diseases. Nat Biotechnol 2016; 34:531-8. [PMID: 27065010 DOI: 10.1038/nbt.3514] [Citation(s) in RCA: 209] [Impact Index Per Article: 26.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2015] [Accepted: 02/12/2016] [Indexed: 12/21/2022]
Abstract
Genetic studies of human disease have traditionally focused on the detection of disease-causing mutations in afflicted individuals. Here we describe a complementary approach that seeks to identify healthy individuals resilient to highly penetrant forms of genetic childhood disorders. A comprehensive screen of 874 genes in 589,306 genomes led to the identification of 13 adults harboring mutations for 8 severe Mendelian conditions, with no reported clinical manifestation of the indicated disease. Our findings demonstrate the promise of broadening genetic studies to systematically search for well individuals who are buffering the effects of rare, highly penetrant, deleterious mutations. They also indicate that incomplete penetrance for Mendelian diseases is likely more common than previously believed. The identification of resilient individuals may provide a first step toward uncovering protective genetic variants that could help elucidate the mechanisms of Mendelian diseases and new therapeutic strategies.
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Affiliation(s)
- Rong Chen
- Department of Genetics and Genomic Sciences, Icahn School of Medicine at Mount Sinai, New York, New York, USA.,Icahn Institute for Genomics and Multiscale Biology, Icahn School of Medicine at Mount Sinai, New York, New York, USA
| | - Lisong Shi
- Department of Genetics and Genomic Sciences, Icahn School of Medicine at Mount Sinai, New York, New York, USA.,Icahn Institute for Genomics and Multiscale Biology, Icahn School of Medicine at Mount Sinai, New York, New York, USA
| | - Jörg Hakenberg
- Department of Genetics and Genomic Sciences, Icahn School of Medicine at Mount Sinai, New York, New York, USA.,Icahn Institute for Genomics and Multiscale Biology, Icahn School of Medicine at Mount Sinai, New York, New York, USA
| | | | - Pamela Sklar
- Department of Genetics and Genomic Sciences, Icahn School of Medicine at Mount Sinai, New York, New York, USA.,Icahn Institute for Genomics and Multiscale Biology, Icahn School of Medicine at Mount Sinai, New York, New York, USA.,Friedman Brain Institute and Department of Psychiatry, Icahn School of Medicine at Mount Sinai, New York, New York, USA
| | | | | | - Lifeng Tian
- Center for Applied Genomics, The Children's Hospital of Philadelphia, Philadelphia, Pennsylvania, USA
| | - Om Prakash
- Department of Clinical Sciences, Diabetes &Endocrinology, Lund University Diabetes Center, Skåne University Hospital, Lund University, Malmö, Sweden
| | - Mathieu Lemire
- Ontario Institute for Cancer Research, Toronto, Ontario, Canada
| | - Patrick Sleiman
- Center for Applied Genomics, The Children's Hospital of Philadelphia, Philadelphia, Pennsylvania, USA
| | - Wei-Yi Cheng
- Department of Genetics and Genomic Sciences, Icahn School of Medicine at Mount Sinai, New York, New York, USA.,Icahn Institute for Genomics and Multiscale Biology, Icahn School of Medicine at Mount Sinai, New York, New York, USA
| | | | - Hardik Shah
- Department of Genetics and Genomic Sciences, Icahn School of Medicine at Mount Sinai, New York, New York, USA.,Icahn Institute for Genomics and Multiscale Biology, Icahn School of Medicine at Mount Sinai, New York, New York, USA
| | | | - Menachem Fromer
- Department of Genetics and Genomic Sciences, Icahn School of Medicine at Mount Sinai, New York, New York, USA.,Icahn Institute for Genomics and Multiscale Biology, Icahn School of Medicine at Mount Sinai, New York, New York, USA.,Friedman Brain Institute and Department of Psychiatry, Icahn School of Medicine at Mount Sinai, New York, New York, USA
| | | | - Matthew A Deardorff
- Center for Applied Genomics, The Children's Hospital of Philadelphia, Philadelphia, Pennsylvania, USA
| | - Elaine Zackai
- Center for Applied Genomics, The Children's Hospital of Philadelphia, Philadelphia, Pennsylvania, USA
| | - Jason R Bobe
- Department of Genetics and Genomic Sciences, Icahn School of Medicine at Mount Sinai, New York, New York, USA.,Icahn Institute for Genomics and Multiscale Biology, Icahn School of Medicine at Mount Sinai, New York, New York, USA
| | - Elissa Levin
- Department of Genetics and Genomic Sciences, Icahn School of Medicine at Mount Sinai, New York, New York, USA.,Icahn Institute for Genomics and Multiscale Biology, Icahn School of Medicine at Mount Sinai, New York, New York, USA
| | - Thomas J Hudson
- Ontario Institute for Cancer Research, Toronto, Ontario, Canada
| | - Leif Groop
- Department of Clinical Sciences, Diabetes &Endocrinology, Lund University Diabetes Center, Skåne University Hospital, Lund University, Malmö, Sweden
| | | | - Hakon Hakonarson
- Center for Applied Genomics, The Children's Hospital of Philadelphia, Philadelphia, Pennsylvania, USA
| | | | - George A Diaz
- Department of Genetics and Genomic Sciences, Icahn School of Medicine at Mount Sinai, New York, New York, USA.,Icahn Institute for Genomics and Multiscale Biology, Icahn School of Medicine at Mount Sinai, New York, New York, USA
| | - Lisa Edelmann
- Department of Genetics and Genomic Sciences, Icahn School of Medicine at Mount Sinai, New York, New York, USA.,Icahn Institute for Genomics and Multiscale Biology, Icahn School of Medicine at Mount Sinai, New York, New York, USA
| | - Eric E Schadt
- Department of Genetics and Genomic Sciences, Icahn School of Medicine at Mount Sinai, New York, New York, USA.,Icahn Institute for Genomics and Multiscale Biology, Icahn School of Medicine at Mount Sinai, New York, New York, USA
| | - Stephen H Friend
- Department of Genetics and Genomic Sciences, Icahn School of Medicine at Mount Sinai, New York, New York, USA.,Icahn Institute for Genomics and Multiscale Biology, Icahn School of Medicine at Mount Sinai, New York, New York, USA.,Sage Bionetworks, Seattle, Washington, USA
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10
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Herzog J, Rid R, Wagner M, Hundsberger H, Eger A, Bauer J, Önder K. Whole-transcriptome gene expression profiling in an epidermolysis bullosa simplex Dowling-Meara model keratinocyte cell line uncovered novel, potential therapeutic targets and affected pathways. BMC Res Notes 2015; 8:785. [PMID: 26666517 PMCID: PMC4678661 DOI: 10.1186/s13104-015-1783-7] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2015] [Accepted: 12/01/2015] [Indexed: 12/28/2022] Open
Abstract
Background To be able to develop effective therapeutics for epidermolysis bullosa simplex (EBS), it is necessary to elucidate the molecular pathomechanisms that give rise to the disease’s characteristic severe skin-blistering phenotype. Results Starting with a whole-transcriptome microarray analysis of an EBS Dowling-Meara model cell line (KEB7), we identified 207 genes showing differential expression relative to control keratinocytes. A complementary qRT-PCR study of 156 candidates confirmed 76.58 % of the selected genes to be significantly up-regulated or down-regulated (p-value <0.05) within biological replicates. Our hit list contains previously identified genes involved in epithelial cell proliferation, cell-substrate adhesion, and responses to diverse biological stimuli. In addition, we identified novel candidate genes and potential affected pathways not previously considered as relevant to EBS pathology. Conclusions Our results broaden our understanding of the molecular processes dysregulated in EBS. Electronic supplementary material The online version of this article (doi:10.1186/s13104-015-1783-7) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Julia Herzog
- Division of Molecular Dermatology, Department of Dermatology, Paracelsus Private Medical University Salzburg, Salzburg, Austria.
| | - Raphaela Rid
- Division of Molecular Dermatology, Department of Dermatology, Paracelsus Private Medical University Salzburg, Salzburg, Austria.
| | - Martin Wagner
- Division of Molecular Dermatology, Department of Dermatology, Paracelsus Private Medical University Salzburg, Salzburg, Austria.
| | - Harald Hundsberger
- Department of Medical and Pharmaceutical Biotechnology, University of Applied Sciences, Krems, Austria.
| | - Andreas Eger
- Department of Medical and Pharmaceutical Biotechnology, University of Applied Sciences, Krems, Austria.
| | - Johann Bauer
- Division of Molecular Dermatology, Department of Dermatology, Paracelsus Private Medical University Salzburg, Salzburg, Austria.
| | - Kamil Önder
- Division of Molecular Dermatology, Department of Dermatology, Paracelsus Private Medical University Salzburg, Salzburg, Austria.
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11
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Feng X, Coulombe PA. Complementary roles of specific cysteines in keratin 14 toward the assembly, organization, and dynamics of intermediate filaments in skin keratinocytes. J Biol Chem 2015. [PMID: 26216883 DOI: 10.1074/jbc.m115.654749] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
We recently showed that inter-keratin disulfide bonding plays an important role in the assembly, organization, and dynamics of keratin intermediate filaments in skin keratinocytes. In particular, cysteine 367 located in the central α-helical rod domain of keratin 14 is necessary for the formation of a stable perinuclear network of keratin filaments (with type II partner keratin 5) in skin keratinocytes analyzed by static and live cell imaging. Here, we show that two additional cysteine residues located in the non-helical head domain of K14, Cys-4 and Cys-40, also participate in inter-keratin disulfide bonding and tandemly play a key role complementary to that of Cys-367 in the assembly, organization, and dynamics of keratin filaments in skin keratinocytes in primary culture. Analysis of K14 variants with single or multiple substitutions of cysteine residues points to a spatial and temporal hierarchy in how Cys-4/Cys-40 and Cys-367 regulate keratin assembly in vitro and filament dynamics in live keratinocytes in culture. Our findings substantiate the importance and complexity of a novel determinant, namely inter-keratin disulfide bonding, for the regulation of several aspects of keratin filaments in surface epithelia.
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Affiliation(s)
- Xia Feng
- From the Department of Biochemistry and Molecular Biology, Bloomberg School of Public Health, Johns Hopkins University, Baltimore, Maryland 21205 and
| | - Pierre A Coulombe
- From the Department of Biochemistry and Molecular Biology, Bloomberg School of Public Health, Johns Hopkins University, Baltimore, Maryland 21205 and the Departments of Biological Chemistry, Dermatology, and Oncology, School of Medicine, Johns Hopkins University, Baltimore, Maryland 21205
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12
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Alonso A, Greenlee M, Matts J, Kline J, Davis KJ, Miller RK. Emerging roles of sumoylation in the regulation of actin, microtubules, intermediate filaments, and septins. Cytoskeleton (Hoboken) 2015; 72:305-39. [PMID: 26033929 PMCID: PMC5049490 DOI: 10.1002/cm.21226] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2014] [Revised: 05/25/2015] [Accepted: 05/27/2015] [Indexed: 12/29/2022]
Abstract
Sumoylation is a powerful regulatory system that controls many of the critical processes in the cell, including DNA repair, transcriptional regulation, nuclear transport, and DNA replication. Recently, new functions for SUMO have begun to emerge. SUMO is covalently attached to components of each of the four major cytoskeletal networks, including microtubule-associated proteins, septins, and intermediate filaments, in addition to nuclear actin and actin-regulatory proteins. However, knowledge of the mechanisms by which this signal transduction system controls the cytoskeleton is still in its infancy. One story that is beginning to unfold is that SUMO may regulate the microtubule motor protein dynein by modification of its adaptor Lis1. In other instances, cytoskeletal elements can both bind to SUMO non-covalently and also be conjugated by it. The molecular mechanisms for many of these new functions are not yet clear, but are under active investigation. One emerging model links the function of MAP sumoylation to protein degradation through SUMO-targeted ubiquitin ligases, also known as STUbL enzymes. Other possible functions for cytoskeletal sumoylation are also discussed.
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Affiliation(s)
- Annabel Alonso
- Department of Biochemistry and Molecular BiologyOklahoma State UniversityStillwaterOklahoma
| | - Matt Greenlee
- Department of Biochemistry and Molecular BiologyOklahoma State UniversityStillwaterOklahoma
| | - Jessica Matts
- Department of Biochemistry and Molecular BiologyOklahoma State UniversityStillwaterOklahoma
| | - Jake Kline
- Department of Biochemistry and Molecular BiologyOklahoma State UniversityStillwaterOklahoma
| | - Kayla J. Davis
- Department of Biochemistry and Molecular BiologyOklahoma State UniversityStillwaterOklahoma
| | - Rita K. Miller
- Department of Biochemistry and Molecular BiologyOklahoma State UniversityStillwaterOklahoma
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13
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Fichna JP, Karolczak J, Potulska-Chromik A, Miszta P, Berdynski M, Sikorska A, Filipek S, Redowicz MJ, Kaminska A, Zekanowski C. Two desmin gene mutations associated with myofibrillar myopathies in Polish families. PLoS One 2014; 9:e115470. [PMID: 25541946 PMCID: PMC4277352 DOI: 10.1371/journal.pone.0115470] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2014] [Accepted: 11/24/2014] [Indexed: 11/29/2022] Open
Abstract
Desmin is a muscle-specific intermediate filament protein which forms a network connecting the sarcomere, T tubules, sarcolemma, nuclear membrane, mitochondria and other organelles. Mutations in the gene coding for desmin (DES) cause skeletal myopathies often combined with cardiomyopathy, or isolated cardiomyopathies. The molecular pathomechanisms of the disease remain ambiguous. Here, we describe and comprehensively characterize two DES mutations found in Polish patients with a clinical diagnosis of desminopathy. The study group comprised 16 individuals representing three families. Two mutations were identified: a novel missense mutation (Q348P) and a small deletion of nine nucleotides (A357_E359del), previously described by us in the Polish population. A common ancestry of all the families bearing the A357_E359del mutation was confirmed. Both mutations were predicted to be pathogenic using a bioinformatics approach, including molecular dynamics simulations which helped to rationalize abnormal behavior at molecular level. To test the impact of the mutations on DES expression and the intracellular distribution of desmin muscle biopsies were investigated. Elevated desmin levels as well as its atypical localization in muscle fibers were observed. Additional staining for M-cadherin, α-actinin, and myosin heavy chains confirmed severe disruption of myofibrill organization. The abnormalities were more prominent in the Q348P muscle, where both small atrophic fibers as well large fibers with centrally localized nuclei were observed. We propose that the mutations affect desmin structure and cause its aberrant folding and subsequent aggregation, triggering disruption of myofibrils organization.
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MESH Headings
- Adult
- DNA Mutational Analysis
- Desmin/chemistry
- Desmin/genetics
- Female
- Genetic Association Studies
- Humans
- Male
- Middle Aged
- Molecular Dynamics Simulation
- Muscle Fibers, Skeletal/chemistry
- Muscle Fibers, Skeletal/metabolism
- Muscle Fibers, Skeletal/pathology
- Mutation, Missense
- Myopathies, Structural, Congenital/genetics
- Myopathies, Structural, Congenital/metabolism
- Myopathies, Structural, Congenital/pathology
- Pedigree
- Poland
- Sequence Deletion
- Young Adult
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Affiliation(s)
- Jakub Piotr Fichna
- Department of Neurodegenerative Disorders, Mossakowski Medical Research Centre, Polish Academy of Sciences, Warszawa, Poland
| | - Justyna Karolczak
- Department of Biochemistry, Nencki Institute of Experimental Biology, Polish Academy of Sciences, Warszawa, Poland
| | | | - Przemyslaw Miszta
- Faculty of Chemistry and Biological and Chemical Research Centre, University of Warsaw, Warszawa, Poland
| | - Mariusz Berdynski
- Department of Neurodegenerative Disorders, Mossakowski Medical Research Centre, Polish Academy of Sciences, Warszawa, Poland
| | - Agata Sikorska
- Department of Biochemistry, Nencki Institute of Experimental Biology, Polish Academy of Sciences, Warszawa, Poland
| | - Slawomir Filipek
- Faculty of Chemistry and Biological and Chemical Research Centre, University of Warsaw, Warszawa, Poland
| | - Maria Jolanta Redowicz
- Department of Biochemistry, Nencki Institute of Experimental Biology, Polish Academy of Sciences, Warszawa, Poland
| | - Anna Kaminska
- Department of Neurology, Medical University of Warsaw, Warszawa, Poland
- Neuromuscular Unit, Mossakowski Medical Research Centre, Polish Academy of Sciences, Warszawa, Poland
| | - Cezary Zekanowski
- Department of Neurodegenerative Disorders, Mossakowski Medical Research Centre, Polish Academy of Sciences, Warszawa, Poland
- * E-mail:
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14
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Coulombe PA, Lee CH. Defining keratin protein function in skin epithelia: epidermolysis bullosa simplex and its aftermath. J Invest Dermatol 2012; 132:763-75. [PMID: 22277943 PMCID: PMC3279600 DOI: 10.1038/jid.2011.450] [Citation(s) in RCA: 87] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Epidermolysis bullosa simplex (EBS) is a rare genetic condition typified by superficial bullous lesions following incident frictional trauma to the skin. Most cases of EBS are due to dominantly acting mutations in keratin 14 (K14) or K5, the type I and II intermediate filament (IF) proteins that copolymerize to form a pancytoplasmic network of 10 nm filaments in basal keratinocytes of epidermis and related epithelia. Defects in K5-K14 filament network architecture cause basal keratinocytes to become fragile, and account for their rupture upon exposure to mechanical trauma. The discovery of the etiology and pathophysiology of EBS was intimately linked to the quest for an understanding of the properties and function of keratin filaments in skin epithelia. Since then, continued cross-fertilization between basic science efforts and clinical endeavors has highlighted several additional functional roles for keratin proteins in the skin, suggested new avenues for effective therapies for keratin-based diseases, and expanded our understanding of the remarkable properties of the skin as an organ system.
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Affiliation(s)
- Pierre A Coulombe
- Department of Biochemistry and Molecular Biology, Bloomberg School of Public Health, Johns Hopkins University, Baltimore, Maryland 21205, USA.
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15
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Bowden PE. Gene therapy for keratin genodermatoses: striving forward but obstacles persist. J Invest Dermatol 2011; 131:1403-5. [PMID: 21673708 DOI: 10.1038/jid.2011.121] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
D'Alessandro and colleagues have investigated stress responses in keratinocyte cell lines lacking keratin 14 (K14-null mutation). In this issue, they describe the use of this model to assess the extent of phenotypic rescue achievable by wild-type K14 in the absence of a dominant negative mutation. This work provides proof that, in principle, transfection of wild-type K14 on a null background can significantly normalize the cell and reduce stress responses. However, hurdles to gene therapy in vivo persist because the majority of patients with keratin genodermatoses have heterozygous dominant negative mutations, which are more disruptive than those of the null state. Although correction in the laboratory is now relatively routine, gene delivery to the skin of patients and stable correction of mutations remain major challenges.
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Affiliation(s)
- Paul E Bowden
- Department of Dermatology and Wound Healing, School of Medicine, Cardiff University, Heath Park, Cardiff, UK.
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16
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Bolling MC, Lemmink HH, Jansen GHL, Jonkman MF. Mutations in KRT5 and KRT14 cause epidermolysis bullosa simplex in 75% of the patients. Br J Dermatol 2011; 164:637-44. [PMID: 21375516 DOI: 10.1111/j.1365-2133.2010.10146.x] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
BACKGROUND Epidermolysis bullosa simplex (EBS) is a mechanobullous genodermatosis that may be caused by mutations in the genes KRT5 and KRT14 encoding the basal epidermal keratins 5 (K5) and 14 (K14). Three main clinical subtypes of EBS exist, differing in onset, distribution and severity of skin blistering. Previous reports of KRT5 and KRT14 mutations suggest a correlation between the location of the mutation and the severity of the associated EBS phenotype. OBJECTIVES The prevalence of KRT5/KRT14 mutations and the genotype-phenotype correlation in the largest tissue-confirmed EBS population is investigated. METHODS KRT5 and KRT14 genomic DNA and cDNA sequences of 76 clinically well-defined unrelated EBS probands were amplified and then subjected to direct sequencing and product length analysis. Immunofluorescence microscopy on patients' skin biopsies with antibodies against K5 and K14 was performed to study protein expression. RESULTS In 57 of 76 (75%) probands 41 different KRT5 and KRT14 mutations were identified, of which 12 were novel. Mutations affecting the highly conserved helix boundary motifs of the rod domains of K5 and K14, and the K14 helix initiation motif in particular, were associated with the severest, EBS Dowling-Meara, phenotype. In 21 EBS probands (37%) the mutation was de novo. In 19 probands (25%) KRT5 or KRT14 mutations were excluded. CONCLUSIONS The phenotype-genotype correlation observed in this large EBS population underscores the importance of helix boundary motifs for keratin assembly. Only three-quarters of biopsy-confirmed EBS probands have KRT5 or KRT14 mutations, indicating genetic heterogeneity in EBS. Alternative gene candidates are discussed.
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Affiliation(s)
- M C Bolling
- Center for Blistering Diseases, Department of Dermatology, University Medical Center Groningen, the Netherlands.
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17
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D'Alessandro M, Coats SE, Jonkman MF, Jonkmann MF, Leigh IM, Lane EB. Keratin 14-null cells as a model to test the efficacy of gene therapy approaches in epithelial cells. J Invest Dermatol 2011; 131:1412-9. [PMID: 21326298 DOI: 10.1038/jid.2011.19] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Skin fragility disorders caused by keratin mutations are incurable, and a better understanding of their etiology is needed to find new ways to improve and treat these conditions. The best-studied skin fragility disorder is epidermolysis bullosa simplex (EBS), an autosomal dominant condition caused by mutations in keratin 5 (K5) or K14. To analyze disease mechanisms and develop gene therapy strategies, we have used keratinocyte cell lines derived from EBS patients as model systems. Here, we describe two cell lines established from EBS patients with K14-null mutations. We analyze the responses of these cells to stress assays previously shown to discriminate between wild-type and keratin-mutant keratinocytes, to directly evaluate the efficacy of rescuing K14-null cells by supplementation with wild-type K14 complementary DNA (cDNA). The K14-null cells show elevated levels of stress correlating with reduced normal keratin function. By transfecting wild-type K14 into these cells, we demonstrate "proof of principle" that an add-back approach can significantly rescue the normal keratinocyte behavior profile. These K14-null cell lines provide a disease model for studying the effects of keratin ablation in EBS patients and to test the efficacy of gene add-back and other therapy approaches in keratinocytes.
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Affiliation(s)
- Mariella D'Alessandro
- CR UK Cell Structure Research Group, Division of Molecular Medicine, College of Life Sciences, University of Dundee, Dundee, UK.
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18
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Kim JS, Lee CH, Coulombe PA. Modeling the self-organization property of keratin intermediate filaments. Biophys J 2011; 99:2748-56. [PMID: 21044571 DOI: 10.1016/j.bpj.2010.09.023] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2010] [Revised: 09/10/2010] [Accepted: 09/15/2010] [Indexed: 11/18/2022] Open
Abstract
Keratin intermediate filaments (IFs) fulfill an important function of structural support in epithelial cells. The necessary mechanical attributes require that IFs be organized into a crosslinked network and accordingly, keratin IFs are typically organized into large bundles in surface epithelia. For IFs comprised of keratins 5 and 14 (K5, K14), found in basal keratinocytes of epidermis, bundling can be self-driven through interactions between K14's carboxy-terminal tail domain and two regions in the central α-helical rod domain of K5. Here, we exploit theoretical principles and computational modeling to investigate how such cis-acting determinants best promote IF crosslinking. We develop a simple model where keratin IFs are treated as rigid rods to apply Brownian dynamics simulation. Our findings suggest that long-range interactions between IFs are required to initiate the formation of bundlelike configurations, while tail domain-mediated binding events act to stabilize them. Our model explains the differences observed in the mechanical properties of wild-type versus disease-causing, defective IF networks. This effort extends the notion that the structural support function of keratin IFs necessitates a combination of intrinsic and extrinsic determinants, and makes specific predictions about the mechanisms involved in the formation of crosslinked keratin networks in vivo.
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Affiliation(s)
- Jin Seob Kim
- Department of Biochemistry and Molecular Biology, Bloomberg School of Public Health, Johns Hopkins University, Baltimore, Maryland, USA.
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19
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Hickerson RP, Leachman SA, Pho LN, Gonzalez-Gonzalez E, Smith FJD, McLean WHI, Contag CH, Leake D, Milstone LM, Kaspar RL. Development of quantitative molecular clinical end points for siRNA clinical trials. J Invest Dermatol 2010; 131:1029-36. [PMID: 21191405 DOI: 10.1038/jid.2010.372] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
RNA interference (RNAi) is an evolutionarily conserved mechanism that results in specific gene inhibition at the mRNA level. The discovery that short interfering RNAs (siRNAs) are selective, potent, and can largely avoid immune surveillance has resulted in keen interest to develop these inhibitors as therapeutics. A single nucleotide-specific siRNA (K6a_513a.12, also known as TD101) was recently evaluated in a phase 1b clinical trial for the rare skin disorder, pachyonychia congenita (PC). To develop a clinical trial molecular end point for this type of trial, methods were developed to: (1) isolate total RNA containing amplifiable mRNA from human skin and callus material; (2) quantitatively distinguish the single-nucleotide mutant mRNA from wild-type K6a mRNA in both patient-derived keratinocytes and patient callus; and (3) demonstrate that repeated siRNA treatment results in sustained inhibition of mutant K6a mRNA in patient-derived keratinocyte cultures. These methods allow noninvasive sampling and monitoring of gene expression from patient-collected shavings and may be useful in evaluating the effectiveness of RNAi-based therapeutics, including inhibitors that specifically target single-nucleotide mutations.
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20
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Wiradjaja F, DiTommaso T, Smyth I. Basement membranes in development and disease. ACTA ACUST UNITED AC 2010; 90:8-31. [PMID: 20301220 DOI: 10.1002/bdrc.20172] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Basement membranes (BMs) are specializations of the extracellular matrix that act as key mediators of development and disease. Their sheet like protein matrices typically serve to separate epithelial or endothelial cell layers from underlying mesenchymal tissues, providing both a biophysical support to overlying tissue as well as a hub to promote and regulate cell-cell and cell-protein interactions. In the latter context, the BM is increasingly being recognized as a mediator of growth factor interactions during development. In this review, we discuss recent findings regarding the structure of the BM and its roles in mediating the normal development of the embryo, and we examine congenital diseases affecting the BM which impact embryonic development and health in later life.
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Affiliation(s)
- Fenny Wiradjaja
- Department of Biochemistry and Molecular Biology, Monash University, Clayton, Melbourne, Australia
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21
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Abstract
Inherited epidermolysis bullosa encompasses dozens of diseases characterized by mechanical fragility of the skin, blister formation, and abnormal wound healing. Most of the more severe subtypes are associated with clinically significant extracutaneous complications. Some subtypes may lead to death, even in early infancy. Over the past two decades substantial advances have been made to our understanding of the underlying molecular basis for each member of this protean group of diseases. Research has now shifted toward the identification of therapeutic interventions, to include gene therapy, recombinant protein infusions, intradermal injection of allogeneic fibroblasts, and stem cell transplantation, that might eventually lead to a definitive cure for this disease. Other developing therapies being explored are directed toward the enhancement of wound healing and the prevention of potentially life-threatening skin cancers in these patients.
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Affiliation(s)
- Jo-David Fine
- Department of Medicine (Dermatology), Vanderbilt University School of Medicine, National Epidermolysis Bullosa Registry, Nashville, TN, USA.
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22
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Coulombe PA, Kerns ML, Fuchs E. Epidermolysis bullosa simplex: a paradigm for disorders of tissue fragility. J Clin Invest 2009; 119:1784-93. [PMID: 19587453 PMCID: PMC2701872 DOI: 10.1172/jci38177] [Citation(s) in RCA: 143] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Epidermolysis bullosa (EB) simplex is a rare genetic condition typified by superficial bullous lesions that result from frictional trauma to the skin. Most cases are due to dominantly acting mutations in either keratin 14 (K14) or K5, the type I and II intermediate filament (IF) proteins tasked with forming a pancytoplasmic network of 10-nm filaments in basal keratinocytes of the epidermis and in other stratified epithelia. Defects in K5/K14 filament network architecture cause basal keratinocytes to become fragile and account for their trauma-induced rupture. Here we review how laboratory investigations centered on keratin biology have deepened our understanding of the etiology and pathophysiology of EB simplex and revealed novel avenues for its therapy.
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Affiliation(s)
- Pierre A Coulombe
- Department of Biochemistry and Molecular Biology, Bloomberg School of Public Health, Johns Hopkins University, Baltimore, MD 21205, USA.
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23
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Farasat S, Wei MH, Herman M, Liewehr DJ, Steinberg SM, Bale SJ, Fleckman P, Toro JR. Novel transglutaminase-1 mutations and genotype-phenotype investigations of 104 patients with autosomal recessive congenital ichthyosis in the USA. J Med Genet 2008; 46:103-11. [PMID: 18948357 DOI: 10.1136/jmg.2008.060905] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
Abstract
BACKGROUND Autosomal recessive congenital ichthyosis (ARCI) is a rare hereditary disorder of cornification. Mutations in the transglutaminase-1 (TGM1) gene, which encodes for the epidermal enzyme transglutaminase-1 (TGase-1), are one of the causes of ARCI. METHODS The TGM1 mutation spectrum was characterised and genotype-phenotype correlations investigated in 104 patients with ARCI ascertained through the National Registry for Ichthyosis and Related Disorders in the USA. Methods: Germline mutations in TGM1 were identified in 55% (57/104) of patients with ARCI. Arginine residues in TGase-1 were mutated in 39% (22/57) of patients overall and 54% (20/37) of those with missense mutations. In total, 55% (12/22) of missense mutations were within CpG dinucleotides and 92% (11/12) of these mutations were C-->T or G-->A transitions. The genotype-phenotype investigation found that ARCI with TGM1 mutations was significantly associated with presence of collodion membrane at birth (p = 0.006), ectropion (p = 0.001), plate-like scales (p = 0.005) and alopecia (p = 0.001). Patients who had at least one mutation predicted to truncate TGase-1 were more likely to have more severe hypohidrosis (p = 0.001) and overheating (p = 0.0007) at onset of symptoms than were those with exclusively TGM1 missense mutations. A logistic model was developed, which predicted that individuals with collodion membrane, alopecia and/or eye problems are about four times more likely to have TGM1 mutations than patients without these findings. CONCLUSION This is the largest investigation of patients with ARCI to date. It expands the TGM1 mutation spectrum and confirms that despite genetic and phenotypic heterogeneity in ARCI, TGM1 is the main causative gene for this disorder. The high frequency of mutated arginine codons in TGM1 may be due to the deamination of CpG dinucleotides.
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Affiliation(s)
- S Farasat
- Division of Cancer Epidemiology and Genetics, National Cancer Institute, National Institutes of Health, 6120 Executive Boulevard, Rockville, MD 20892-4562, USA
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24
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Leachman SA, Hickerson RP, Hull PR, Smith FJD, Milstone LM, Lane EB, Bale SJ, Roop DR, McLean WHI, Kaspar RL. Therapeutic siRNAs for dominant genetic skin disorders including pachyonychia congenita. J Dermatol Sci 2008; 51:151-7. [PMID: 18495438 DOI: 10.1016/j.jdermsci.2008.04.003] [Citation(s) in RCA: 94] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2008] [Accepted: 04/02/2008] [Indexed: 01/02/2023]
Abstract
The field of science and medicine has experienced a flood of data and technology associated with the human genome project. Over 10,000 human diseases have been genetically defined, but little progress has been made with respect to the clinical application of this knowledge. A notable exception to this exists for pachyonychia congenita (PC), a rare, dominant-negative keratin disorder. The establishment of a non-profit organization, PC Project, has led to an unprecedented coalescence of patients, scientists, and physicians with a unified vision of developing novel therapeutics for PC. Utilizing the technological by-products of the human genome project, such as RNA interference (RNAi) and quantitative RT-PCR (qRT-PCR), physicians and scientists have collaborated to create a candidate siRNA therapeutic that selectively inhibits a mutant allele of KRT6A, the most commonly affected PC keratin. In vitro investigation of this siRNA demonstrates potent inhibition of the mutant allele and reversal of the cellular aggregation phenotype. In parallel, an allele-specific quantitative real-time RT-PCR assay has been developed and validated on patient callus samples in preparation for clinical trials. If clinical efficacy is ultimately demonstrated, this "first-in-skin" siRNA may herald a paradigm shift in the treatment of dominant-negative genetic disorders.
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Affiliation(s)
- Sancy A Leachman
- Department of Dermatology and Huntsman Cancer Institute, University of Utah, Salt Lake City, UT, United States.
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25
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Szeverenyi I, Cassidy AJ, Chung CW, Lee BTK, Common JEA, Ogg SC, Chen H, Sim SY, Goh WLP, Ng KW, Simpson JA, Chee LL, Eng GH, Li B, Lunny DP, Chuon D, Venkatesh A, Khoo KH, McLean WHI, Lim YP, Lane EB. The Human Intermediate Filament Database: comprehensive information on a gene family involved in many human diseases. Hum Mutat 2008; 29:351-60. [PMID: 18033728 DOI: 10.1002/humu.20652] [Citation(s) in RCA: 257] [Impact Index Per Article: 16.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
We describe a revised and expanded database on human intermediate filament proteins, a major component of the eukaryotic cytoskeleton. The family of 70 intermediate filament genes (including those encoding keratins, desmins, and lamins) is now known to be associated with a wide range of diverse diseases, at least 72 distinct human pathologies, including skin blistering, muscular dystrophy, cardiomyopathy, premature aging syndromes, neurodegenerative disorders, and cataract. To date, the database catalogs 1,274 manually-curated pathogenic sequence variants and 170 allelic variants in intermediate filament genes from over 459 peer-reviewed research articles. Unrelated cases were collected from all of the six sequence homology groups and the sequence variations were described at cDNA and protein levels with links to the related diseases and reference articles. The mutations and polymorphisms are presented in parallel with data on protein structure, gene, and chromosomal location and basic information on associated diseases. Detailed statistics relating to the variants records in the database are displayed by homology group, mutation type, affected domain, associated diseases, and nucleic and amino acid substitutions. Multiple sequence alignment algorithms can be run from queries to determine DNA or protein sequence conservation. Literature sources can be interrogated within the database and external links are provided to public databases. The database is freely and publicly accessible online at www.interfil.org (last accessed 13 September 2007). Users can query the database by various keywords and the search results can be downloaded. It is anticipated that the Human Intermediate Filament Database (HIFD) will provide a useful resource to study human genome variations for basic scientists, clinicians, and students alike.
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26
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Kerns ML, DePianto D, Dinkova-Kostova AT, Talalay P, Coulombe PA. Reprogramming of keratin biosynthesis by sulforaphane restores skin integrity in epidermolysis bullosa simplex. Proc Natl Acad Sci U S A 2007; 104:14460-5. [PMID: 17724334 PMCID: PMC1964870 DOI: 10.1073/pnas.0706486104] [Citation(s) in RCA: 76] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Epidermolysis bullosa simplex (EBS) is a rare inherited condition in which the epidermis loses its integrity after mechanical trauma. EBS is typified by the dysfunction of intermediate filaments in basal keratinocytes of epidermis. Most cases of EBS are due to mutations in the keratin 5 or 14 gene (K5 and K14), whose products copolymerize to form intermediate filaments in basal keratinocytes. Available treatments for this disorder are only palliative. Here we exploit functional redundancy within the keratin gene family as the basis for therapy. We show that genetic activation of Gli2 or treatment with a pharmacological activator of Nrf2, two transcription factors eliciting distinct transcriptional programs, alleviates the blistering caused by a K14 deficiency in an EBS mouse model, correlating with K17 induction in basal epidermal keratinocytes. Nrf2 induction is brought about by treatment with sulforaphane, a natural product. Sulforaphane thus represents an attractive option for the prevention of skin blistering associated with K14 mutations in EBS.
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Affiliation(s)
| | | | | | - Paul Talalay
- Pharmacology and Molecular Sciences, and
- To whom correspondence may be addressed. E-mail: or
| | - Pierre A. Coulombe
- Departments of *Biological Chemistry
- Dermatology, 725 North Wolfe Street, The Johns Hopkins University School of Medicine, Baltimore, MD 21205
- To whom correspondence may be addressed. E-mail: or
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27
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Kim S, Coulombe PA. Intermediate filament scaffolds fulfill mechanical, organizational, and signaling functions in the cytoplasm. Genes Dev 2007; 21:1581-97. [PMID: 17606637 DOI: 10.1101/gad.1552107] [Citation(s) in RCA: 227] [Impact Index Per Article: 13.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Intermediate filaments (IFs) are cytoskeletal polymers whose protein constituents are encoded by a large family of differentially expressed genes. Owing in part to their properties and intracellular organization, IFs provide crucial structural support in the cytoplasm and nucleus, the perturbation of which causes cell and tissue fragility and accounts for a large number of genetic diseases in humans. A number of additional roles, nonmechanical in nature, have been recently uncovered for IF proteins. These include the regulation of key signaling pathways that control cell survival, cell growth, and vectorial processes including protein targeting in polarized cellular settings. As this discovery process continues to unfold, a rationale for the large size of this family and the context-dependent regulation of its members is finally emerging.
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Affiliation(s)
- Seyun Kim
- Department of Biological Chemistry, The Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
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Saeki H, Nakamura K, Tsunemi Y, Komine M, Tamaki K. Novel mutation (Asp158Val) in H1 domain of keratin 5 gene in a Japanese patient with Köbner-type epidermolysis bullosa simplex. J Dermatol 2006; 33:692-5. [PMID: 17040498 DOI: 10.1111/j.1346-8138.2006.00160.x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
We describe a 19-year-old Japanese male with Köbner-type epidermolysis bullosa simplex (EBS-KB) with a novel keratin gene mutation. The patient developed blisters on the feet, palms, elbows and knees soon after birth. His father is similarly affected with blistering, but his mother and younger brother are not affected. Histological examination revealed that the primary separation in the blister occurred within the basal cell layer. Sequence analysis demonstrated an A-to-T transition at the second position of codon 158 in the keratin 5 (K5) gene. The amino acid at codon 158 was deduced to have changed from asparagine to valine. We identified a novel mutation (Asp158Val) in the H1 domain of the K5 gene in this Japanese patient with EBS-KB. This is the first gene mutation report of EBS-KB in the H1 domain of the K5 gene.
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Affiliation(s)
- Hidehisa Saeki
- Department of Dermatology, Faculty of Medicine, University of Tokyo, Hongo 7-3-1, Bunkyo-ku, Tokyo 113-8655, Japan.
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29
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Abstract
Cytosine methylation is a common form of post-replicative DNA modification seen in both bacteria and eukaryotes. Modified cytosines have long been known to act as hotspots for mutations due to the high rate of spontaneous deamination of this base to thymine, resulting in a G/T mismatch. This will be fixed as a C-->T transition after replication if not repaired by the base excision repair (BER) pathway or specific repair enzymes dedicated to this purpose. This hypermutability has led to depletion of the target dinucleotide CpG outside of special CpG islands in mammals, which are normally unmethylated. We review the importance of C-->T transitions at non-island CpGs in human disease: When these occur in the germline, they are a common cause of inherited diseases such as epidermolysis bullosa and mucopolysaccharidosis, while in the soma they are frequently found in the genes for tumor suppressors such as p53 and the retinoblastoma protein, causing cancer. We also examine the specific repair enzymes involved, namely the endonuclease Vsr in Escherichia coli and two members of the uracil DNA glycosylase (UDG) superfamily in mammals, TDG and MBD4. Repair brings its own problems, since it will require remethylation of the replacement cytosine, presumably coupling repair to methylation by either the maintenance methylase Dnmt1 or a de novo enzyme such as Dnmt3a. Uncoupling of methylation from repair may be one way to remove methylation from DNA. We also look at the possible role of specific cytosine deaminases such as Aid and Apobec in accelerating deamination of methylcytosine and consequent DNA demethylation.
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Affiliation(s)
- C P Walsh
- Centre for Molecular Biosciences, School of Biomedical Sciences, University of Ulster, Northern Ireland
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Bär H, Mücke N, Kostareva A, Sjöberg G, Aebi U, Herrmann H. Severe muscle disease-causing desmin mutations interfere with in vitro filament assembly at distinct stages. Proc Natl Acad Sci U S A 2005; 102:15099-104. [PMID: 16217025 PMCID: PMC1250230 DOI: 10.1073/pnas.0504568102] [Citation(s) in RCA: 107] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Desmin is the major intermediate filament (IF) protein of muscle. Recently, mutations of the desmin gene have been reported to cause familial or sporadic forms of human skeletal, as well as cardiac, myopathy, termed desmin-related myopathy (DRM). The impact of any of these mutations on filament assembly and integration into the cytoskeletal network of myocytes is currently not understood, despite the fact that all cause the same histopathological defect, i.e., desmin aggregation. To gain more insight into the molecular basis of this process, we investigated how mutations within the alpha-helical rod domain of desmin affect both the assembly of the recombinant protein in vitro as well as the filament-forming capacity in cDNA-transfected cells. Whereas 6 of 14 mutants assemble into seemingly normal IFs in the test tube, the other mutants interfere with the assembly process at distinct stages, i.e., tetramer formation, unit-length filament (ULF) formation, filament elongation, and IF maturation. Correspondingly, the mutants with in vitro assembly defects yield dot-like aggregates in transfected cells, whereas the mutants that form IFs constitute a seemingly normal IF cytoskeleton in the cellular context. At present, it is entirely unclear why the latter mutant proteins also lead to aggregate formation in myocytes. Hence, these findings may be a starting point to dissect the contribution of the individual subdomains for desmin pathology and, eventually, the development of therapeutic interventions.
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Affiliation(s)
- Harald Bär
- Department of Molecular Genetics, German Cancer Research Center, D-69120 Heidelberg, Germany
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31
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Gu LH, Coulombe PA. Defining the properties of the nonhelical tail domain in type II keratin 5: insight from a bullous disease-causing mutation. Mol Biol Cell 2005; 16:1427-38. [PMID: 15647384 PMCID: PMC551504 DOI: 10.1091/mbc.e04-06-0498] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2004] [Accepted: 01/03/2005] [Indexed: 12/24/2022] Open
Abstract
Inherited mutations in the intermediate filament (IF) proteins keratin 5 (K5) or keratin 14 (K14) cause epidermolysis bullosa simplex (EBS), in which basal layer keratinocytes rupture upon trauma to the epidermis. Most mutations are missense alleles affecting amino acids located in the central alpha-helical rod domain of K5 and K14. Here, we study the properties of an unusual EBS-causing mutation in which a nucleotide deletion (1649delG) alters the last 41 amino acids and adds 35 residues to the C terminus of K5. Relative to wild type, filaments coassembled in vitro from purified K5-1649delG and K14 proteins are shorter and exhibit weak viscoelastic properties when placed under strain. Loss of the C-terminal 41 residues contributes to these alterations. When transfected in cultured epithelial cells, K5-1649delG incorporates into preexisting keratin IFs and also forms multiple small aggregates that often colocalize with hsp70 in the cytoplasm. Aggregation is purely a function of the K5-1649delG tail domain; in contrast, the cloned 109 residue-long tail domain from wild type K5 is distributed throughout the cytoplasm and colocalizes partly with keratin IFs. These data provide a mechanistic basis for the cell fragility seen in individuals bearing the K5-1649delG allele, and point to the role of the C-terminal 41 residues in determining K5's assembly properties.
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Affiliation(s)
- Li-Hong Gu
- Departments of Biological Chemistry and Dermatology, The Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
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32
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Hess JF, Budamagunta MS, FitzGerald PG, Voss JC. Characterization of structural changes in vimentin bearing an epidermolysis bullosa simplex-like mutation using site-directed spin labeling and electron paramagnetic resonance. J Biol Chem 2004; 280:2141-6. [PMID: 15556930 PMCID: PMC2904505 DOI: 10.1074/jbc.m412254200] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Mutations in intermediate filament protein genes are responsible for a number of inherited genetic diseases including skin blistering diseases, corneal opacities, and neurological degenerations. Mutation of the arginine (Arg) residue of the highly conserved LNDR motif has been shown to be causative in inherited disorders in at least four different intermediate filament (IF) proteins found in skin, cornea, and the central nervous system. Thus this residue appears to be broadly important to IF assembly and/or function. While the genetic basis for these diseases has been clearly defined, the inability to determine crystal structure for IFs has precluded a determination of how these mutations affect assembly/structure/function of IFs. To investigate the impact of mutation at this site in IFs, we have mutated the LNDR to LNDS in vimentin, a Type III intermediate filament protein, and have examined the impact of this change on assembly using electron paramagnetic resonance. Compared with wild type vimentin, the mutant shows normal formation of the coiled coil dimer, with a slight reduction in the stability of the dimer in rod domain 1. Probing the dimer-dimer interactions shows the formation of normal dimer centered on residue 191 but a failure of dimerization at residue 348 in rod domain 2. These data point toward a specific stage of assembly at which a common disease-causing mutation in IF proteins interrupts assembly.
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Affiliation(s)
- John F. Hess
- Department of Cell Biology and Human Anatomy, School of Medicine, University of California, Davis, California 95616
| | - Madhu S. Budamagunta
- Department of Biological Chemistry, School of Medicine, University of California, Davis, California 95616
| | - Paul G. FitzGerald
- Department of Cell Biology and Human Anatomy, School of Medicine, University of California, Davis, California 95616
- To whom correspondence should be addressed. Tel.: 530-752-7130; Fax: 530-752-8520;
| | - John C. Voss
- Department of Biological Chemistry, School of Medicine, University of California, Davis, California 95616
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Uitto J, Richard G. Progress in epidermolysis bullosa: Genetic classification and clinical implications. ACTA ACUST UNITED AC 2004; 131C:61-74. [PMID: 15468152 DOI: 10.1002/ajmg.c.30035] [Citation(s) in RCA: 70] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
Epidermolysis bullosa (EB), a heterogenous group of genodermatoses, is characterized by fragility and blistering of the skin associated with extracutaneous manifestations. Based on clinical severity, constellation of the phenotypic manifestations, and the level of tissue separation within the cutaneous basement membrane zone (BMZ), EB has been divided into distinct subcategories. Traditionally, these include the simplex, junctional, and dystrophic forms of EB, and recently attention has been drawn to hemidesmosomal variants demonstrating tissue separation at the level of the hemidesmosomes. Specific mutations in ten distinct genes expressed within the cutaneous BMZ have been delineated in >500 families with different variants of EB. The types of mutations, their positions along the affected genes, and their consequences at the mRNA and protein levels provide explanation for the phenotypic variability and genetic heterogeneity of this group of genodermatoses. Elucidation of mutations in different forms of EB has direct translational applications for improved diagnosis and molecularly based classification with prognostic implications as well as for genetic counseling and DNA-based prenatal testing in families with EB.
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Affiliation(s)
- Jouni Uitto
- Department of Dermatology and Cutaneous Biology, Jefferson Medical College, Philadelphia, PA 19107, USA.
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Abstract
The association of keratin mutations with genetic skin fragility disorders is now one of the best-established examples of cytoskeleton disorders. It has served as a paradigm for many other diseases and has been highly informative for the study of intermediate filaments and their associated components, in helping to understand the functions of this large family of structural proteins. The keratin diseases have shown unequivocally that, at least in the case of the epidermal keratins, a major function of intermediate filaments is to provide physical resilience for epithelial cells. This review article reflects on the variety of phenotypes arising from mutations in keratins and the reasons for this variation.
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Affiliation(s)
- E B Lane
- Cancer Research UK Cell Structure Research Group, Division of Cell and Developmental Biology, University of Dundee School of Life Sciences, MSI/WTB Complex, Dow Street, Dundee DD1 5EH, UK.
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35
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Smith TA, Steinert PM, Parry DAD. Modeling effects of mutations in coiled-coil structures: case study using epidermolysis bullosa simplex mutations in segment 1a of K5/K14 intermediate filaments. Proteins 2004; 55:1043-52. [PMID: 15146501 DOI: 10.1002/prot.20089] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
The sequence of a protein chain determines both its conformation and its function in vivo. An attempt is made to gain an understanding of the classes of deformations that can arise in an important structural motif, the alpha-helical coiled coil, as a consequence of mutations occurring in its underlying heptad substructure. In order to do so we consider the model structure of segment 1A in intermediate filaments and then investigate the structures arising from each of the 22 mutations observed in cytokeratin K5/K14 molecules that lead to variants of epidermolysis bullosa simplex. These are refined separately using a molecular dynamics protocol. The mutations often result in a significant distortion of the backbone over a turn or so of the alpha helix in either the chain itself or its constituent partner, leading to the likelihood of impaired chain aggregation and hence molecular assembly. One mutant (K14-L143P; 1A-28) gave rise to structural distortion along almost the entire length of segment 1A. The remaining structures showed less deformation, and normal-looking intermediate filaments are likely in vivo. In addition, an identical mutation in the same position in each of the chains in the heterodimer did not necessarily give equivalent structural distortions. Although proline mutations frequently lead to the most severe structural deformations, a non-proline substitution (K14-R125S; 1A-10) gave rise to the largest local structural disruption that was observed. Unexpectedly, mutations in positions a and d were not always of the greatest structural significance, although three in position a were shown by AGADIR to result in a significant increase in alpha-helix stability.
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Affiliation(s)
- Thomasin A Smith
- Institute of Fundamental Sciences, Massey University, Palmerston North, New Zealand
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36
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D'Alessandro M, Morley SM, Ogden PH, Liovic M, Porter RM, Lane EB. Functional improvement of mutant keratin cells on addition of desmin: an alternative approach to gene therapy for dominant diseases. Gene Ther 2004; 11:1290-5. [PMID: 15215887 DOI: 10.1038/sj.gt.3302301] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
A major challenge to the concept of gene therapy for dominant disorders is the silencing or repairing of the mutant allele. Supplementation therapy is an alternative approach that aims to bypass the defective gene by inducing the expression of another gene, with similar function but not susceptible to the disrupting effect of the mutant one. Epidermolysis bullosa simplex (EBS) is a genetic skin fragility disorder caused by mutations in the genes for keratins K5 or K14, the intermediate filaments present in the basal cells of the epidermis. Keratin diseases are nearly all dominant in their inheritance. In cultured keratinocytes, mutant keratin renders cells more sensitive to a variety of stress stimuli such as osmotic shock, heat shock or scratch wounding. Using a 'severe' disease cell culture model system, we demonstrate reversion towards wild-type responses to stress after transfection with human desmin, an intermediate filament protein normally expressed in muscle cells. Such a supplementation therapy approach could be widely applicable to patients with related individual mutations and would avoid some of the financial obstacles to gene therapy for rare diseases.
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Affiliation(s)
- M D'Alessandro
- Cancer Research UK Cell Structure Research Group, School of Life Sciences, University of Dundee, MSI/WTB Complex, Dundee, Scotland, UK
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37
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Owens DW, Wilson NJ, Hill AJM, Rugg EL, Porter RM, Hutcheson AM, Quinlan RA, van Heel D, Parkes M, Jewell DP, Campbell SS, Ghosh S, Satsangi J, Lane EB. Human keratin 8 mutations that disturb filament assembly observed in inflammatory bowel disease patients. J Cell Sci 2004; 117:1989-99. [PMID: 15090596 DOI: 10.1242/jcs.01043] [Citation(s) in RCA: 77] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
We have identified miss-sense mutations in keratin 8 in a subset of patients with inflammatory bowel disease (Crohn disease and ulcerative colitis). Inflammatory bowel diseases are a group of disorders that are polygenic in origin and involve intestinal epithelial breakdown. We investigated the possibility that these keratin mutations might contribute to the course of the disease by adversely affecting the keratin filament network that provides mechanical support to cells in epithelia. The mutations (Gly62 to Cys, Ile63 to Val and Lys464 to Asn) all lie outside the major mutation hotspots associated with severe disease in epidermal keratins, but using a combination of in vitro and cell culture assays we show that they all have detrimental effects on K8/K18 filament assembly in vitro and in cultured cells. The G62C mutation also gives rise to homodimer formation on oxidative stress to cultured intestinal epithelial cells, and homodimers are known to be polymerization incompetent. Impaired keratin assembly resulting from the K8 mutations found in some inflammatory bowel disease patients would be predicted to affect the maintenance and re-establishment of mechanical resilience in vivo, as required during keratin cytoskeleton remodeling in cell division and differentiation, which may lead to epithelial fragility in the gut. Simple epithelial keratins may thus be considered as candidates for genes contributing to a risk of inflammatory bowel disease.
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Affiliation(s)
- D W Owens
- Cancer Research UK Cell Structure Research Group, School of Life Science, University of Dundee, Dundee, DD1 5EH, UK
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38
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Werner NS, Windoffer R, Strnad P, Grund C, Leube RE, Magin TM. Epidermolysis bullosa simplex-type mutations alter the dynamics of the keratin cytoskeleton and reveal a contribution of actin to the transport of keratin subunits. Mol Biol Cell 2003; 15:990-1002. [PMID: 14668478 PMCID: PMC363056 DOI: 10.1091/mbc.e03-09-0687] [Citation(s) in RCA: 82] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Dominant keratin mutations cause epidermolysis bullosa simplex by transforming keratin (K) filaments into aggregates. As a first step toward understanding the properties of mutant keratins in vivo, we stably transfected epithelial cells with an enhanced yellow fluorescent protein-tagged K14R125C mutant. K14R125C became localized as aggregates in the cell periphery and incorporated into perinuclear keratin filaments. Unexpectedly, keratin aggregates were in dynamic equilibrium with soluble subunits at a half-life time of <15 min, whereas filaments were extremely static. Therefore, this dominant-negative mutation acts by altering cytoskeletal dynamics and solubility. Unlike previously postulated, the dominance of mutations is limited and strictly depends on the ratio of mutant to wild-type protein. In support, K14R125C-specific RNA interference experiments resulted in a rapid disintegration of aggregates and restored normal filaments. Most importantly, live cell inhibitor studies revealed that the granules are transported from the cell periphery inwards in an actin-, but not microtubule-based manner. The peripheral granule zone may define a region in which keratin precursors are incorporated into existing filaments. Collectively, our data have uncovered the transient nature of keratin aggregates in cells and offer a rationale for the treatment of epidermolysis bullosa simplex by using short interfering RNAs.
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Affiliation(s)
- Nicola Susann Werner
- Institut fuer Physiologische Chemie, Abteilung fuer Zellbiochemie, Universitaetsklinikum Bonn, 53115 Bonn, Germany
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Dillman JF, McGary KL, Schlager JJ. Sulfur mustard induces the formation of keratin aggregates in human epidermal keratinocytes☆1Current address: University of Texas at Austin, Cell & Molecular Biology, 1 University Station C0930, Austin, TX 78712-0253, USA. Toxicol Appl Pharmacol 2003; 193:228-36. [PMID: 14644625 DOI: 10.1016/j.taap.2003.08.003] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
The vesicant sulfur mustard is an alkylating agent that has the capacity to cross-link biological molecules. We are interested in identifying specific proteins that are altered upon sulfur mustard exposure. Keratins are particularly important for the structural integrity of skin, and several genetically inherited blistering diseases have been linked to mutations in keratin 5 and keratin 14. We examined whether sulfur mustard exposure alters keratin biochemistry in cultured human epidermal keratinocytes. Western blotting with specific monoclonal antibodies revealed the formation of stable high-molecular-weight "aggregates" containing keratin 14 and/or keratin 5. These aggregates begin to form within 15 min after sulfur mustard exposure. These aggregates display a complex gel electrophoresis pattern between approximately 100 and approximately 200 kDa. Purification and analysis of these aggregates by one- and two-dimensional gel electrophoresis and mass spectrometry confirmed the presence of keratin 14 and keratin 5 and indicate that at least some of the aggregates are composed of keratin 14-keratin 14, keratin 14-keratin 5, or keratin 5-keratin 5 dimers. These studies demonstrate that sulfur mustard induces keratin aggregation in keratinocytes and support further investigation into the role of keratin aggregation in sulfur mustard-induced vesication.
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Affiliation(s)
- James F Dillman
- Applied Pharmacology Branch, U.S. Army Medical Research Institute of Chemical Defense, Aberdeen Proving Ground, MD 21010-5400, USA.
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40
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Gu LH, Kim SC, Ichiki Y, Park J, Nagai M, Kitajima Y. A usual frameshift and delayed termination codon mutation in keratin 5 causes a novel type of epidermolysis bullosa simplex with migratory circinate erythema. J Invest Dermatol 2003; 121:482-5. [PMID: 12925204 DOI: 10.1046/j.1523-1747.2003.12424.x] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
We report here two unrelated families in Japan and Korea having patients with a unique type of epidermolysis bullosa simplex and a novel mutation in the keratin gene KRT5, i.e., a frameshift and delayed stop codon inconsistent with any subtype described before. The patients showed migratory circinate erythema and multiple vesicles on the circular belt-like areas affected by erythema. Electron microscopy of skin biopsies showed a reduction in the number of keratin intermediate filaments in the basal cells without tonofilament clumping. We identified a novel heterozygous deletion mutation (1649delG of KRT5) in both cases. This deletion is predicted to produce a mutant keratin 5 protein with a frameshift of its terminal 41 amino acids and 35 amino acids longer than the wild-type keratin 5 protein due to a delayed termination codon. As the same abnormal elongated mutant KRT5 gene was found in the independent families, the predicted abnormal elongated keratin protein is likely to lead to an atypical clinical phenotype that has never been reported, possibly by interfering with the functional interaction between keratin and its associated proteins.
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Affiliation(s)
- Li-Hong Gu
- Department of Dermatology, Gifu University School of Medicine, Tsukasa-Machi 40, Gifu 500-8705, Japan
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41
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Sørensen CB, Andresen BS, Jensen UB, Jensen TG, Jensen PKA, Gregersen N, Bolund L. Functional testing of keratin 14 mutant proteins associated with the three major subtypes of epidermolysis bullosa simplex. Exp Dermatol 2003; 12:472-9. [PMID: 12930305 DOI: 10.1034/j.1600-0625.2002.120416.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Epidermolysis bullosa simplex (EBS) is a group of autosomal dominantly inherited skin disorders characterized by the development of intra-epidermal skin blisters on mild mechanical trauma. The three major clinical subtypes (Weber-Cockayne, Koebner and Dowling-Meara) are all caused by mutations in either the keratin 5 (KRT5) or keratin 14 (KRT14) gene. Previously, we identified three novel KRT14 missense mutations in Danish EBS patients associated with the three different forms of EBS (1). The identified KRT14 mutations represent the full spectrum of the classical EBS subtypes. In the present study we investigated these mutations in a cellular expression system in order to analyse their effects on the keratin cytoskeleton. KRT14 expression vectors were constructed by fusing the nucleotide sequence encoding the FLAG reporter peptide to the 3' end of the KRT14 cDNA sequences. The expression vectors were transiently transfected into normal human primary keratinocytes (NHK), HaCaT or HeLa cells in order to analyze the ability of the mutant K14 proteins to integrate into the existing endogenous keratin filament network (KFN). No effect on the keratin cytoskeleton was observed upon transfection of NHK with the various K14 constructs neither with nor without a subsequently induced heat-stress. In contrast, all constructs, including wild-type K14, caused collapse of the endogenous KFN in a small fraction of the transfected HeLa and HaCaT cells. However, overexpression of the mutation associated with the most severe form of the disease, EBS Dowling-Meara, resulted in a higher number of transfected HaCaT cells with KFN collapse (P < 0.001). Thus, although a background KFN perturbance was observed upon transfection with the wild-type K14 construct, the mutant protein associated with the most severe form of EBS worsened the KFN perturbation significantly compared with the mutant proteins associated with the milder forms of the disease and the normal K14 protein. This shows that the clinical severity of disease-associated mutations identified in patients can be tested using this expression system, although it can not at present be used to discriminate between the milder forms. Assessment of the endogenous K14 protein expression in NHK and HaCaT cells indicated that the higher level of endogenous keratin expression in NHK might make these cells more resistant to perturbation of the keratin cytoskeleton by overexpressed K14 protein than HaCaT cells.
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Shirakata Y, Tamai K, Nakaoka H, Tokumaru S, Sayama K, Murakami S, Hashimoto K. Severe palmo-plantar hyperkeratosis in Koebner epidermolysis bullosa simplex. J Dermatol 2003; 30:135-40. [PMID: 12692381 DOI: 10.1111/j.1346-8138.2003.tb00361.x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2002] [Accepted: 11/21/2002] [Indexed: 11/30/2022]
Abstract
A 22-year-old Japanese woman with Koebner epidermolysis bullosa simplex presented with severe palmo-plantar hyperkeratosis. Skin biopsy specimens from the palm revealed hyperkeratosis and acanthosis with blistering in the basal cell layer. An electron microscopic study showed cytolysis of basal cells and clumping of tonofilaments forming thick bundles and perinuclear electron-dense bodies. Hand contractures were released and covered with full thickness autografts or split thickness autografts. The donor site was successfully treated with cultured epidermal autografts.
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Affiliation(s)
- Yuji Shirakata
- Department of Dermatology, Ehime University School of Medicine, Japan
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43
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Jensen TG, Sørensen CB, Jensen UB, Bolund L. Epidermolysis bullosa simplex keratinocytes with extended lifespan established by ectopic expression of telomerase. Exp Dermatol 2003; 12:71-7. [PMID: 12631249 DOI: 10.1034/j.1600-0625.2003.120109.x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
As part of a strategy to develop somatic gene therapy of epidermolysis bullosa simplex (EBS) we have established patient keratinocytes with expanded lifespan by ectopic expression of the human telomerase gene (hTert). The presence of an active telomerase enzyme was demonstrated by the telomerase repeat amplification protocol (TRAP). The hTert(+) cells have a normal karyotype and the cells have, until now, undergone more than 80 population doublings (PDs) after hTert retroviral transduction while control cells exhibited senescence-associated proliferation arrest after 8 PDs. In organotypic culture the hTert(+) cells are capable of forming a stratified epidermis illustrating their preserved ability to differentiate.
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Affiliation(s)
- Thomas G Jensen
- Department of Human Genetics, University of Aarhus, 8000 Aarhus C, Denmark.
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44
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Affiliation(s)
- Amy S Paller
- Division of Dermatology, Children's Memorial Hospital, The Feinberg School of Medicine, Northwestern University, Chicago, IL 60614, USA.
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45
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D'Alessandro M, Russell D, Morley SM, Davies AM, Lane EB. Keratin mutations of epidermolysis bullosa simplex alter the kinetics of stress response to osmotic shock. J Cell Sci 2002; 115:4341-51. [PMID: 12376565 DOI: 10.1242/jcs.00120] [Citation(s) in RCA: 93] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
The intermediate filament cytoskeleton is thought to confer physical resilience on tissue cells, on the basis of extrapolations from the phenotype of cell fragility that results from mutations in skin keratins. There is a need for functional cell assays in which the impact of stress on intermediate filaments can be induced and analyzed. Using osmotic shock, we have induced cytoskeleton changes that suggest protective functions for actin and intermediate filament systems. Induction of the resulting stress response has been monitored in keratinocyte cells lines carrying K5 or K14 mutations, which are associated with varying severity of epidermolysis bullosa simplex. Cells with severe mutations were more sensitive to osmotic stress and took longer to recover from it. Their stress-activated response pathways were induced faster, as seen by early activation of JNK, ATF-2 and c-Jun. We demonstrate that the speed of a cell's response to hypotonic stress, by activation of the SAPK/JNK pathway, is correlated with the clinical severity of the mutation carried. The response to hypo-osmotic shock constitutes a discriminating stress assay to distinguish between the effects of different keratin mutations and is a potentially valuable tool in developing therapeutic strategies for keratin-based skin fragility disorders.
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Affiliation(s)
- Mariella D'Alessandro
- Cancer Research UK Cell Structure Research Group, University of Dundee School of Life Sciences, MSI/WTB Complex, Dow Street, Dundee DD1 5EH, UK
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Yasukawa K, Sawamura D, McMillan JR, Nakamura H, Shimizu H. Dominant and recessive compound heterozygous mutations in epidermolysis bullosa simplex demonstrate the role of the stutter region in keratin intermediate filament assembly. J Biol Chem 2002; 277:23670-4. [PMID: 11973334 DOI: 10.1074/jbc.m200974200] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Keratin intermediate filaments are important cytoskeletal structural proteins involved in maintaining cell shape and function. Mutations in the epidermal keratin genes, keratin 5 or keratin 14 lead to the disruption of keratin filament assembly, resulting in an autosomal dominant inherited blistering skin disease, epidermolysis bullosa simplex (EBS). We investigated a large EBS kindred who exhibited a markedly heterogeneous clinical presentation and detected two distinct keratin 5 mutations in the proband, the most severely affected. One missense mutation (E170K) in the highly conserved helix initiation peptide sequence of the 1A rod domain was found in all the affected family members. In contrast, the other missense mutation (E418K) was found only in the proband. The E418K mutation was located in the stutter region, an interruption in the heptad repeat regularity, whose function as yet remains unclear. We hypothesized that this mutated stutter allele was clinically silent when combined with the wild type allele but aggravates the clinical severity of EBS caused by the E170K mutation on the other allele. To confirm this in vitro, we transfected mutant keratin 5 cDNA into cultured cells. Although only 12.7% of the cells transfected with the E170K mutation alone showed disrupted keratin filament aggregations, significantly more cells (30.0%) cotransfected with both E170K and E418K mutations demonstrated keratin aggregation (p < 0.05). These transfection assay results corresponded to the heterogeneous clinical findings of the EBS patient in this kindred. We have identified the first case of both compound heterozygous dominant (E170K) and recessive (E418K) mutations in any keratin gene and confirmed the significant involvement of the stutter region in the assembly and organization of the keratin intermediate filament network in vitro.
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Affiliation(s)
- Kana Yasukawa
- Department of Dermatology, Hokkaido University Graduate School of Medicine, Kita 15, Nishi 7, Kita-Ku, Sapporo 060-8638, Japan
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Lavedan C, Buchholtz S, Nussbaum RL, Albin RL, Polymeropoulos MH. A mutation in the human neurofilament M gene in Parkinson's disease that suggests a role for the cytoskeleton in neuronal degeneration. Neurosci Lett 2002; 322:57-61. [PMID: 11958843 DOI: 10.1016/s0304-3940(01)02513-7] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Parkinson's disease (PD) is a common neurodegenerative movement disorder characterized by the destruction of dopaminergic neurons of the substantia nigra. We have identified a new mutation (Gly336Ser) in the medium neurofilament subunit in a patient of French-Canadian origin with early onset severe PD. This finding suggests, for the first time, that aberrations in neuronal molecules involved in the cytoskeleton could lead to the development of the pathology seen in PD.
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Affiliation(s)
- Christian Lavedan
- Novartis Pharmaceuticals Corporation, Pharmacogenetics, 9 W Watkins Mill Road, Gaithersburg, MD 20878, USA
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Gu LH, Ichiki Y, Sato M, Kitajima Y. A novel nonsense mutation at E106 of the 2B rod domain of keratin 14 causes dominant epidermolysis bullosa simplex. J Dermatol 2002; 29:136-45. [PMID: 11990248 DOI: 10.1111/j.1346-8138.2002.tb00236.x] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Epidermolysis bullosa simplex (EBS) is classified into three main types and is caused, in most cases, by missense mutations in the genes encoding keratin (K) 5 and K14. In this study, we clinically, ultrastructurally, immunohistochemically, and molecularly studied a patient with a dominant EBS, Köbner type. Using sequence analysis of genomic DNA, a novel K14 nonsense mutation was identified. A heterozygous mutation G1231T of KRT14 was found to be associated with the disease in the patient. The mutation created a premature stop codon (amino acid codon 411, residue 106 of the 2B helix) in the K14 molecule. This residue lies in a highly conserved region and was recently found to be absolutely required for molecular stability and intermediate filament assembly in K5 and K14. The E411X (E106X) heterozygous ablation, missing the last 16 amino acid residues of the 2B and the entire tail domain of K14, led to disease but did not result in clumping of keratin filaments. It is the first premature stop codon mutation of K14 found in dominant EBS.
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Affiliation(s)
- Li-Hong Gu
- Department of Dermatology, Gifu University, School of Medicine, Japan
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Premaratne C, Klingberg S, Glass I, Wright K, Murrell D. Epidermolysis bullosa simplex Dowling-Meara due to an arginine to cysteine substitution in exon 1 of keratin 14. Australas J Dermatol 2002; 43:28-34. [PMID: 11869205 DOI: 10.1046/j.1440-0960.2002.00548.x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Epidermolysis bullosa simplex (EBS) is a blistering disorder affecting the basal layer of the epidermis usually inherited in an autosomal dominant fashion. Most cases are caused by mutations in the genes encoding keratin 5 (K5) and keratin 14 (K14) and are characterized by cytolysis within the basal layer of the epidermis. We report a patient manifesting the Dowling-Meara variant of EBS in whom we characterized a cytosine to thymine transition at codon 125 (R125C) in K14. This missense mutation is located at the amino terminus of the helical rod domain of the keratin 14 molecule, resulting in defective pairing with K5, thereby disrupting keratin tonofibril integrity.
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Affiliation(s)
- Champi Premaratne
- Department of Dermatology, St George Hospital, University of New South Wales, Sydney, Australia
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50
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Herrmann H, Wedig T, Porter RM, Lane EB, Aebi U. Characterization of early assembly intermediates of recombinant human keratins. J Struct Biol 2002; 137:82-96. [PMID: 12064936 DOI: 10.1006/jsbi.2002.4466] [Citation(s) in RCA: 93] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
The intermediate filaments (IFs) form major structural elements of the cytoskeleton. In vitro analyses of these fibrous proteins reveal very different assembly properties for the nuclear and cytoplasmic IF proteins. However, keratins in particular, the largest and most heterogenous group of cytoplasmic IF proteins, have been difficult to analyze due to their rapid assembly dynamics under the near-physiological conditions used for other IF proteins. We show here that keratins, like other cytoplasmic IF proteins, go through a stage of assembling into full-width soluble complexes, i.e., "unit-length filaments" (ULFs). In contrast to other IF proteins, however, longitudinal annealing of keratin ULFs into long filaments quasi-coincides with their formation. In vitro assembly of IF proteins into filaments can be initiated by an increase of the ionic strength and/or lowering of the pH of the assembly buffer. We now document that 23-mer peptides from the head domains of various IF proteins can induce filament formation even under conditions of low salt and high pH. This suggests that the "heads" are involved in the formation and longitudinal association of the ULFs. Using a Tris-buffering protocol that causes formation of soluble oligomers at pH 9, the epidermal keratins K5/14 form less regular filaments and less efficiently than the simple epithelial keratins K8/18. In sodium phosphate buffers (pH 7.5), however, K5/14 were able to form long partially unraveled filaments which compacted into extended, regular filaments upon addition of 20 mM KCl. Applying the same assembly regimen to mutant K14 R125H demonstrated that mutations causing a severe disease phenotype and morphological filament abnormalities can form long, regular filaments with surprising efficiency in vitro.
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Affiliation(s)
- Harald Herrmann
- Division for Cell Biology, German Cancer Research Center, Heidelberg, Germany.
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