115 results on '"Mark T. Keating"'
Search Results
2. Matrix crosslinking enhances macrophage adhesion, migration, and inflammatory activation
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Jessica Y. Hsieh, Mark T. Keating, Tim D. Smith, Vijaykumar S. Meli, Elliot L. Botvinick, and Wendy F. Liu
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Biotechnology ,TP248.13-248.65 ,Medical technology ,R855-855.5 - Abstract
Macrophages are versatile cells of the innate immune system that can adopt a variety of functional phenotypes depending on signals in their environment. In previous work, we found that culture of macrophages on fibrin, the provisional extracellular matrix protein, inhibits their inflammatory activation when compared to cells cultured on polystyrene surfaces. Here, we sought to investigate the role of matrix stiffness in the regulation of macrophage activity by manipulating the mechanical properties of fibrin. We utilize a photo-initiated crosslinking method to introduce dityrosine crosslinks to a fibrin gel and confirm an increase in gel stiffness through active microrheology. We observe that matrix crosslinking elicits distinct changes in macrophage morphology, integrin expression, migration, and inflammatory activation. Macrophages cultured on a stiffer substrate exhibit greater cell spreading and expression of αM integrin. Furthermore, macrophages cultured on crosslinked fibrin exhibit increased motility. Finally, culture of macrophages on photo-crosslinked fibrin enhances their inflammatory activation compared to unmodified fibrin, suggesting that matrix crosslinking regulates the functional activation of macrophages. These findings provide insight into how the physical properties of the extracellular matrix might control macrophage behavior during inflammation and wound healing.
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- 2019
- Full Text
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3. Transcriptional Profiling of Caudal Fin Regeneration in Zebrafish
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Michael Schebesta, Ching-Ling Lien, Felix B. Engel, and Mark T. Keating
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Technology ,Medicine ,Science - Abstract
Regeneration of severed limbs in adult animals is restricted to urodele amphibians. Mammals, including humans, have very limited regenerative capabilities and even with proper treatment, only the tips of our digits can grow back. Teleost fish can regenerate amputated fins, the evolutionary ancestors of limbs. To elucidate the principles of limb-fin regeneration, we performed an Affymetrix microarray screen on regenerating caudal fins 12, 24, 48, and 72 h post amputation. Approximately 15,000 zebrafish transcripts were analyzed, identifying 829 transcripts as differentially expressed during regeneration. Of those, 563 were up-regulated and 266 were down-regulated. We constructed a comprehensive database containing expression data, functional assignment, and background information from the literature for each differentially expressed transcript. In order to validate our findings, we employed three approaches: (1) microarray expression analysis of genes previously implicated in fin regeneration, (2) RT-PCR analysis of genes newly identified as differentially expressed during regeneration, and (3) in situ hybridization of the up-regulated genes bambi, dlx5A, and her6. Moreover, we show that Smad 1/5/8 proteins, effector molecules of Bmp signaling, are phosphorylated during fin regeneration. Taken together, we provide a comprehensive database of fin regeneration that will serve as an important tool for understanding the molecular mechanisms of regeneration.
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- 2006
- Full Text
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4. Transcutaneous Flexible Sensor for In Vivo Photonic Detection of pH and Lactate
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Dat Nguyen, Micah M. Lawrence, Haley Berg, Monika Aya Lyons, Samir Shreim, Mark T. Keating, John Weidling, and Elliot L. Botvinick
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Fluid Flow and Transfer Processes ,Process Chemistry and Technology ,Bioengineering ,Instrumentation - Published
- 2022
5. Vascularization and innervation of slits within polydimethylsiloxane sheets in the subcutaneous space of athymic nude mice
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Rachel E Gurlin, Mark T Keating, Shiri Li, Jonathan RT Lakey, Sébastien de Feraudy, Bhupinder S Shergill, and Elliot L Botvinick
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Biochemistry ,QD415-436 - Abstract
Success of cell therapy in avascular sites will depend on providing sufficient blood supply to transplanted tissues. A popular strategy of providing blood supply is to embed cells within a functionalized hydrogel implanted within the host to stimulate neovascularization. However, hydrogel systems are not always amenable for removal post-transplantation; thus, it may be advantageous to implant a device that contains cells while also providing access to the circulation so retrieval is possible. Here we investigate one instance of providing access to a vessel network, a thin sheet with through-cut slits, and determine if it can be vascularized from autologous materials. We compared the effect of slit width on vascularization of a thin sheet following subcutaneous implantation into an animal model. Polydimethylsiloxane sheets with varying slit widths (approximately 150, 300, 500, or 1500 µm) were fabricated from three-dimensional printed molds. Subcutaneous implantation of sheets in immunodeficient mice revealed that smaller slit widths have evidence of angiogenesis and new tissue growth, while larger slit widths contain native mature tissue squeezing into the space. Our results show that engineered slit sheets may provide a simple approach to cell transplantation by providing a prevascularized and innervated environment.
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- 2017
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6. CPAP-to-Ventilator: Open-Source Documentation, UC Irvine
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Cody E. Dunn, Christian Crouzet, Mark T. Keating, Thinh Phan, Matthew Brenner, Elliot L. Botvinick, and Bernard Choi
- Published
- 2022
7. Gene expression analysis of zebrafish heart regeneration.
- Author
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Ching-Ling Lien, Michael Schebesta, Shinji Makino, Gerhard J Weber, and Mark T Keating
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Biology (General) ,QH301-705.5 - Abstract
Mammalian hearts cannot regenerate. In contrast, zebrafish hearts regenerate even when up to 20% of the ventricle is amputated. The mechanism of zebrafish heart regeneration is not understood. To systematically characterize this process at the molecular level, we generated transcriptional profiles of zebrafish cardiac regeneration by microarray analyses. Distinct gene clusters were identified based on temporal expression patterns. Genes coding for wound response/inflammatory factors, secreted molecules, and matrix metalloproteinases are expressed in regenerating heart in sequential patterns. Comparisons of gene expression profiles between heart and fin regeneration revealed a set of regeneration core molecules as well as tissue-specific factors. The expression patterns of several secreted molecules around the wound suggest that they play important roles in heart regeneration. We found that both platelet-derived growth factor-a and -b (pdgf-a and pdgf-b) are upregulated in regenerating zebrafish hearts. PDGF-B homodimers induce DNA synthesis in adult zebrafish cardiomyocytes. In addition, we demonstrate that a chemical inhibitor of PDGF receptor decreases DNA synthesis of cardiomyocytes both in vitro and in vivo during regeneration. Our data indicate that zebrafish heart regeneration is associated with sequentially upregulated wound healing genes and growth factors and suggest that PDGF signaling is required.
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- 2006
- Full Text
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8. Activin-βA Signaling Is Required for Zebrafish Fin Regeneration
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Mark T. Keating, Anna Jaźwińska, and Rossen Badakov
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animal structures ,Transcription, Genetic ,HUMDISEASE ,DEVBIO ,Biology ,General Biochemistry, Genetics and Molecular Biology ,Fin regeneration ,Animals ,Regeneration ,Inhibins ,Progenitor cell ,Zebrafish ,Agricultural and Biological Sciences(all) ,Epidermis (botany) ,Biochemistry, Genetics and Molecular Biology(all) ,Regeneration (biology) ,Cell migration ,Anatomy ,biology.organism_classification ,Activins ,Up-Regulation ,Cell biology ,General Agricultural and Biological Sciences ,Wound healing ,Blastema ,Signal Transduction - Abstract
Summary Vertebrate limb regeneration occurs in anamniotes such as newts, salamanders, and zebrafish [1–4]. After appendage amputation, the resection site is covered by a wound epidermis capping the underlying mature tissues of the stump from which the blastema emerges. The blastema is a mass of progenitor cells that constitute an apical growth zone. During outgrowth formation, the proximal blastemal cells progressively leave the zone and undergo the differentiation that results in the replacement of the amputated structures. Little is known about the mechanisms triggering regenerative events after injury. The zebrafish caudal fin provides a valuable model to study the mechanisms of regeneration [3, 5, 6]. Zebrafish blastemal cells express specific genes, such as the homeobox-containing transcription factors msxB and msxC [7], and secreted signal FGF20a [8]. In this study, we set out to identify signals that are transcriptionally upregulated after fin amputation and before blastema formation. Accordingly, a gene encoding a TGFβ-related ligand, activin-βA ( actβA ), was found to be strongly induced within 6 hr after fin amputation at the wound margin, and later in the blastema. Inhibition of Activin signaling through two specific chemical inhibitors, SB431542 and SB505124, lead to the early and complete block of regeneration. The morpholino knockdown of actβA and its receptor alk4 impaired the progression of regeneration. Closer examination of the phenotype revealed that Activin signaling is necessary for cell migration during wound healing and blastemal proliferation. These findings reveal a role of Activin-βA signaling in the tissue repair after injury and subsequent outgrowth formation during epigenetic regeneration of the vertebrate appendage.
- Published
- 2007
9. Periostin induces proliferation of differentiated cardiomyocytes and promotes cardiac repair
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Roger J. Hajjar, Bernhard Kühn, Djamel Lebeche, Federica del Monte, Yuh-Shin Chang, Shima Arab, and Mark T Keating
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Male ,Integrins ,medicine.medical_specialty ,Myocardial Infarction ,Periostin ,Biology ,General Biochemistry, Genetics and Molecular Biology ,Phosphatidylinositol 3-Kinases ,Mitotic cell cycle ,Internal medicine ,medicine ,Animals ,Humans ,Regeneration ,Myocyte ,Myocytes, Cardiac ,Rats, Wistar ,Progenitor cell ,Ventricular remodeling ,Mitosis ,Cells, Cultured ,Cell Proliferation ,Regeneration (biology) ,Cell Differentiation ,DNA ,Hypertrophy ,General Medicine ,Cell cycle ,medicine.disease ,Fibrosis ,Rats ,Cell biology ,Endocrinology ,Cell Adhesion Molecules - Abstract
Adult mammalian hearts respond to injury with scar formation and not with cardiomyocyte proliferation, the cellular basis of regeneration. Although cardiogenic progenitor cells may maintain myocardial turnover, they do not give rise to a robust regenerative response. Here we show that extracellular periostin induced reentry of differentiated mammalian cardiomyocytes into the cell cycle. Periostin stimulated mononucleated cardiomyocytes to go through the full mitotic cell cycle. Periostin activated alphaV, beta1, beta3 and beta5 integrins located in the cardiomyocyte cell membrane. Activation of phosphatidylinositol-3-OH kinase was required for periostin-induced reentry of cardiomyocytes into the cell cycle and was sufficient for cell-cycle reentry in the absence of periostin. After myocardial infarction, periostin-induced cardiomyocyte cell-cycle reentry and mitosis were associated with improved ventricular remodeling and myocardial function, reduced fibrosis and infarct size, and increased angiogenesis. Thus, periostin and the pathway that it regulates may provide a target for innovative strategies to treat heart failure.
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- 2007
10. CACNA1H Mutations in Autism Spectrum Disorders
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Igor Splawski, David E. Clapham, Stephanie C. Stotz, Allison Cherry, Mark T. Keating, and Dana S. Yoo
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DNA Mutational Analysis ,Mutation, Missense ,Timothy syndrome ,Epigenetics of autism ,Biology ,behavioral disciplines and activities ,Biochemistry ,Calcium Channels, T-Type ,mental disorders ,medicine ,CACNA1H ,Humans ,Missense mutation ,Heritability of autism ,Autistic Disorder ,Molecular Biology ,Conserved Sequence ,Family Health ,Genetics ,Molecular Epidemiology ,Calcium channel ,Cell Biology ,medicine.disease ,Phenotype ,Pedigree ,Electrophysiology ,Kinetics ,Case-Control Studies ,biology.protein ,Autism - Abstract
Autism spectrum disorders (ASD) are neurodevelopmental conditions characterized by impaired social interaction, communication skills, and restricted and repetitive behavior. The genetic causes for autism are largely unknown. Previous studies implicate CACNA1C (L-type Ca(V)1.2) calcium channel mutations in a disorder associated with autism (Timothy syndrome). Here, we identify missense mutations in the calcium channel gene CACNA1H (T-type Ca(V)3.2) in 6 of 461 individuals with ASD. These mutations are located in conserved and functionally relevant domains and are absent in 480 ethnically matched controls (p = 0.014, Fisher's exact test). Non-segregation within the pedigrees between the mutations and the ASD phenotype clearly suggest that the mutations alone are not responsible for the condition. However, functional analysis shows that all these mutations significantly reduce Ca(V)3.2 channel activity and thus could affect neuronal function and potentially brain development. We conclude that the identified mutations could contribute to the development of the ASD phenotype.
- Published
- 2006
11. Transcriptional Profiling of Caudal Fin Regeneration in Zebrafish
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Mark T. Keating, Michael Schebesta, Felix B. Engel, and Ching-Ling Lien
- Subjects
Male ,Microarray ,fin ,lcsh:Medicine ,her ,Smad Proteins ,SMAD ,lcsh:Technology ,Mesoderm ,Databases, Genetic ,Basic Helix-Loop-Helix Transcription Factors ,lcsh:Science ,Zebrafish ,Oligonucleotide Array Sequence Analysis ,General Environmental Science ,Genetics ,Reverse Transcriptase Polymerase Chain Reaction ,General Medicine ,Up-Regulation ,Cell biology ,Female ,microarray ,Research Article ,Signal Transduction ,Tail ,Article Subject ,In situ hybridization ,Biology ,General Biochemistry, Genetics and Molecular Biology ,Fin regeneration ,Animals ,Regeneration ,Gene ,Homeodomain Proteins ,Wound Healing ,dlx ,lcsh:T ,Gene Expression Profiling ,lcsh:R ,Fish fin ,Reproducibility of Results ,Zebrafish Proteins ,bambi ,biology.organism_classification ,Gene Expression Regulation ,bmp ,lcsh:Q ,BAMBI ,Epidermis ,Transcription Factors - Abstract
Regeneration of severed limbs in adult animals is restricted to urodele amphibians. Mammals, including humans, have very limited regenerative capabilities and even with proper treatment, only the tips of our digits can grow back. Teleost fish can regenerate amputated fins, the evolutionary ancestors of limbs. To elucidate the principles of limb-fin regeneration, we performed an Affymetrix microarray screen on regenerating caudal fins 12, 24, 48, and 72 h post amputation. Approximately 15,000 zebrafish transcripts were analyzed, identifying 829 transcripts as differentially expressed during regeneration. Of those, 563 were up-regulated and 266 were down-regulated. We constructed a comprehensive database containing expression data, functional assignment, and background information from the literature for each differentially expressed transcript. In order to validate our findings, we employed three approaches: (1) microarray expression analysis of genes previously implicated in fin regeneration, (2) RT-PCR analysis of genes newly identified as differentially expressed during regeneration, and (3)in situ hybridizationof the up-regulated genes bambi,dlx5A, and her6. Moreover, we show that Smad 1/5/8 proteins, effector molecules of Bmp signaling, are phosphorylated during fin regeneration. Taken together, we provide a comprehensive database of fin regeneration that will serve as an important tool for understanding the molecular mechanisms of regeneration.
- Published
- 2006
12. Tissue inhibitor of metalloproteinase 1 regulates matrix metalloproteinase activity during newt limb regeneration
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Mark T. Keating, Vladimir Vinarsky, Shannon J. Odelberg, Donald L. Atkinson, and Tamara J. Stevenson
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Regulation of gene expression ,Wound Healing ,Metalloproteinase ,Tissue Inhibitor of Metalloproteinase-1 ,Regeneration (biology) ,Molecular Sequence Data ,Gene Expression Regulation, Developmental ,Extremities ,Anatomy ,Biology ,Matrix metalloproteinase ,Tissue inhibitor of metalloproteinase ,Salamandridae ,Up-Regulation ,Cell biology ,body regions ,Downregulation and upregulation ,Metalloproteases ,Animals ,Regeneration ,Amino Acid Sequence ,Wound healing ,Developmental Biology ,TIMP1 - Abstract
Matrix metalloproteinase (MMP) activity is important for newt limb regeneration. In most biological processes that require MMP function, MMP activity is tightly controlled by a variety of mechanisms, including the coexpression of natural inhibitors. Here, we show that gene expression of one such inhibitor, tissue inhibitor of metalloproteinase 1 (NvTIMP1), is upregulated during the wound healing and dedifferentiation stages of regeneration when several MMPs are at their maximal expression levels. Newt MMPs and NvTIMP1 also exhibit similar spatial expression patterns during the early stages of limb regeneration. NvTIMP1 inhibits the proteolytic activity of regeneration-related newt MMPs and, like human TIMP1, can induce a weak mitogenic response in certain cell types. These results suggest that NvTIMP1 may be functioning primarily to maintain optimal levels of MMP activity during the early stages of limb regeneration, while possibly serving a secondary role as a mitogen.
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- 2006
13. p38 MAP kinase inhibition enables proliferation of adult mammalian cardiomyocytes
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Yibin Wang, Huiping Jiang, Felix B. Engel, Shuxun Ren, Mychelle T. Duong, Michael Schebesta, Gang Lu, Jeffery B. Madwed, and Mark T. Keating
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MAP Kinase Signaling System ,Cellular differentiation ,Cyclin A ,Cyclin B ,Mitosis ,p38 Mitogen-Activated Protein Kinases ,Mice ,Genetics ,Animals ,Myocyte ,Myocytes, Cardiac ,Rats, Wistar ,Oligonucleotide Array Sequence Analysis ,Cyclin ,Mice, Knockout ,biology ,Gene Expression Profiling ,Cell Differentiation ,Research Papers ,Rats ,Cell biology ,Enzyme Activation ,Gene Expression Regulation ,Mitogen-activated protein kinase ,biology.protein ,Cytokinesis ,Developmental Biology - Abstract
Adult mammalian cardiomyocytes are considered terminally differentiated and incapable of proliferation. Consequently, acutely injured mammalian hearts do not regenerate, they scar. Here, we show that adult mammalian cardiomyocytes can divide. One important mechanism used by mammalian cardiomyocytes to control cell cycle is p38 MAP kinase activity. p38 regulates expression of genes required for mitosis in cardiomyocytes, including cyclin A and cyclin B. p38 activity is inversely correlated with cardiac growth during development, and its overexpression blocks fetal cardiomyocyte proliferation. Activation of p38 in vivo by MKK3bE reduces BrdU incorporation in fetal cardiomyocytes by 17.6%. In contrast, cardiac-specific p38α knockout mice show a 92.3% increase in neonatal cardiomyocyte mitoses. Furthermore, inhibition of p38 in adult cardiomyocytes promotes cytokinesis. Finally, mitosis in adult cardiomyocytes is associated with transient dedifferentiation of the contractile apparatus. Our findings establish p38 as a key negative regulator of cardiomyocyte proliferation and indicate that adult cardiomyocytes can divide.
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- 2005
14. Severe arrhythmia disorder caused by cardiac L-type calcium channel mutations
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Pradeep Kumar, Alan H. Beggs, Katherine W. Timothy, Niels Decher, Michael C. Sanguinetti, Igor Splawski, Mark T. Keating, and Frank B. Sachse
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Male ,medicine.medical_specialty ,Calcium Channels, L-Type ,Xenopus ,Long QT syndrome ,Molecular Sequence Data ,Glycine ,Mutation, Missense ,Timothy syndrome ,Action Potentials ,Biology ,QT interval ,Sudden death ,Exon ,Internal medicine ,medicine ,Animals ,Humans ,Missense mutation ,L-type calcium channel ,Amino Acid Sequence ,Syndactyly ,Multidisciplinary ,Myocardium ,Infant, Newborn ,Brain ,Infant ,Arrhythmias, Cardiac ,Exons ,Syndrome ,Biological Sciences ,medicine.disease ,Pedigree ,Electrophysiology ,Phenotype ,Endocrinology ,Child, Preschool ,Oocytes ,Female - Abstract
Timothy syndrome (TS) is a multisystem disorder that causes syncope and sudden death from cardiac arrhythmias. Prominent features include congenital heart disease, immune deficiency, intermittent hypoglycemia, cognitive abnormalities, and autism. All TS individuals have syndactyly (webbing of fingers and toes). We discovered that TS resulted from a recurrent, de novo cardiac L-type calcium channel (Ca V 1.2) mutation, G406R. G406 is located in alternatively spliced exon 8A, encoding transmembrane segment S6 of domain I. Here, we describe two individuals with a severe variant of TS (TS2). Neither child had syndactyly. Both individuals had extreme prolongation of the QT interval on electrocardiogram, with a QT interval corrected for heart rate ranging from 620 to 730 ms, causing multiple arrhythmias and sudden death. One individual had severe mental retardation and nemaline rod skeletal myopathy. We identified de novo missense mutations in exon 8 of Ca V 1.2 in both individuals. One was an analogous mutation to that found in exon 8A in classic TS, G406R. The other mutation was G402S. Exon 8 encodes the same region as exon 8A, and the two are mutually exclusive. The spliced form of Ca V 1.2 containing exon 8 is highly expressed in heart and brain, accounting for ≈80% of Ca V 1.2 mRNAs. G406R and G402S cause reduced channel inactivation, resulting in maintained depolarizing L-type calcium currents. Computer modeling showed prolongation of cardiomyocyte action potentials and delayed afterdepolarizations, factors that increase risk of arrhythmia. These data indicate that gain-of-function mutations of Ca V 1.2 exons 8 and 8A cause distinct forms of TS.
- Published
- 2005
15. The SRF Target Gene Fhl2 Antagonizes RhoA/MAL-Dependent Activation of SRF
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Alfred Nordheim, Judith M. Müller, Petra Galgoczy, Roland Schüle, Frank B. Gertler, Felix B. Engel, Ulrike Philippar, Martin Vingron, Christoph Dieterich, Gerhard Schratt, and Mark T. Keating
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Serum Response Factor ,RHOA ,genetic structures ,Proteolipids ,Recombinant Fusion Proteins ,LIM-Homeodomain Proteins ,Muscle Proteins ,Mice ,In vivo ,Coactivator ,Serum response factor ,Animals ,Gene ,Molecular Biology ,Homeodomain Proteins ,biology ,Reverse Transcriptase Polymerase Chain Reaction ,Gene Expression Profiling ,Myelin and Lymphocyte-Associated Proteolipid Proteins ,Stem Cells ,Membrane Transport Proteins ,Herpes Simplex Virus Protein Vmw65 ,Promoter ,Cell Biology ,musculoskeletal system ,Precipitin Tests ,Molecular biology ,Chromatin ,eye diseases ,FHL2 ,Gene expression profiling ,embryonic structures ,NIH 3T3 Cells ,cardiovascular system ,biology.protein ,rhoA GTP-Binding Protein ,Myelin Proteins ,Transcription Factors - Abstract
RhoA signaling regulates the activity of the transcription factor SRF (serum response factor) during muscle differentiation. How RhoA signaling is integrated at SRF target promoters to achieve muscle-lineage-specific expression is largely unknown. Using large-scale expression profiling combined with bioinformatic and biochemical approaches, we identified several SRF target genes, including Fhl2, encoding a transcriptional cofactor that is highly expressed in the heart. SRF binds the Fhl2 promoter in vivo and regulates Fhl2 expression in response to RhoA activation. FHL2 protein and SRF interact physically, and FHL2 binds the promoters of SRF-responsive smooth muscle (SM) genes, but not the promoters of immediate-early genes (IEGs), in response to RhoA. FHL2 antagonizes induction of SM genes, but not IEGs or cardiac genes, by competing with the coactivator MAL/MRTF-A for SRF binding. Our findings identify an autoregulatory mechanism to selectively regulate subsets of RhoA-activated SRF target genes.
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- 2004
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16. Spectrum and prevalence of cardiac sodium channel variants among black, white, Asian, and Hispanic individuals: Implications for arrhythmogenic susceptibility and Brugada/long QT syndrome genetic testing
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Monica Chadha, Igor Splawski, Richard S. Judson, David J. Tester, J. Claiborne Stephens, Michael J. Ackerman, Melissa L. Will, Mark T. Keating, Gregg S. Jones, Mark E. Curran, Jonathan C. Makielski, Christopher R. Burrow, Chuanbo Xu, and Katherine W. Timothy
- Subjects
Long QT syndrome ,Bundle-Branch Block ,DNA Mutational Analysis ,Mutation, Missense ,Sudden death ,Sodium Channels ,NAV1.5 Voltage-Gated Sodium Channel ,Gene Frequency ,Polymorphism (computer science) ,Physiology (medical) ,medicine ,Genetic predisposition ,Humans ,Missense mutation ,Genetic Predisposition to Disease ,Chromatography, High Pressure Liquid ,Polymorphism, Single-Stranded Conformational ,Brugada syndrome ,Genetic testing ,Genetics ,medicine.diagnostic_test ,business.industry ,Racial Groups ,Exons ,Syndrome ,Sudden infant death syndrome ,medicine.disease ,Long QT Syndrome ,Ventricular Fibrillation ,Cardiology and Cardiovascular Medicine ,business - Abstract
Objectives The purpose of this study was to determine the prevalence and spectrum of nonsynonymous polymorphisms (amino acid variants) in the cardiac sodium channel among healthy subjects. Background Pathogenic mutations in the cardiac sodium channel gene, SCN5A , cause approximately 15 to 20% of Brugada syndrome (BrS1), 5 to 10% of long QT syndrome (LQT3), and 2 to 5% of sudden infant death syndrome. Methods Using single-stranded conformation polymorphism, denaturing high-performance liquid chromatography, and/or direct DNA sequencing, mutational analysis of the protein-encoding exons of SCN5A was performed on 829 unrelated, anonymous healthy subjects: 319 black, 295 white, 112 Asian, and 103 Hispanic. Results In addition to the four known common polymorphisms (R34C, H558R, S1103Y, and R1193Q), four relatively ethnic-specific polymorphisms were identified: R481W, S524Y, P1090L, and V1951L. Overall, 39 distinct missense variants (28 novel) were elucidated. Nineteen variants (49%) were found only in the black cohort. Only seven variants (18%) localized to transmembrane-spanning domains. Four variants (F1293S, R1512W, and V1951L cited previously as BrS1-causing mutations and S1787N previously published as a possible LQT3-causing mutation) were identified in this healthy cohort. Conclusions This study provides the first comprehensive determination of the prevalence and spectrum of cardiac sodium channel variants in healthy subjects from four distinct ethnic groups. This compendium of SCN5A variants is critical for proper interpretation of SCN5A genetic testing and provides an essential hit list of targets for future functional studies to determine whether or not any of these variants mediate genetic susceptibility for arrhythmias in the setting of either drugs or disease.
- Published
- 2004
17. CaV1.2 Calcium Channel Dysfunction Causes a Multisystem Disorder Including Arrhythmia and Autism
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Katherine W. Timothy, Helen Tager-Flusberg, Carlo Napolitano, Mark T. Keating, Michael C. Sanguinetti, Peter J. Schwartz, Raffaella Bloise, Silvia G. Priori, Leah M. Sharpe, Robert M. Joseph, Pradeep Kumar, Karen Condouris, Igor Splawski, and Niels Decher
- Subjects
Male ,medicine.medical_specialty ,Calcium Channels, L-Type ,Heart disease ,Limb Deformities, Congenital ,Mutation, Missense ,Timothy syndrome ,Action Potentials ,CHO Cells ,General Biochemistry, Genetics and Molecular Biology ,Cav1.2 ,Mice ,Xenopus laevis ,Cricetinae ,Internal medicine ,medicine ,Animals ,Humans ,Missense mutation ,Repolarization ,Abnormalities, Multiple ,Myocytes, Cardiac ,Calcium Signaling ,Autistic Disorder ,Child ,Brain Chemistry ,Neurons ,Calcium metabolism ,biology ,Voltage-dependent calcium channel ,Biochemistry, Genetics and Molecular Biology(all) ,Calcium channel ,Cell Membrane ,Genetic Diseases, Inborn ,Infant, Newborn ,Brain ,Arrhythmias, Cardiac ,Heart ,Syndrome ,medicine.disease ,Pedigree ,Endocrinology ,Oocytes ,biology.protein ,Calcium ,Female - Abstract
Ca(V)1.2, the cardiac L-type calcium channel, is important for excitation and contraction of the heart. Its role in other tissues is unclear. Here we present Timothy syndrome, a novel disorder characterized by multiorgan dysfunction including lethal arrhythmias, webbing of fingers and toes, congenital heart disease, immune deficiency, intermittent hypoglycemia, cognitive abnormalities, and autism. In every case, Timothy syndrome results from the identical, de novo Ca(V)1.2 missense mutation G406R. Ca(V)1.2 is expressed in all affected tissues. Functional expression reveals that G406R produces maintained inward Ca(2+) currents by causing nearly complete loss of voltage-dependent channel inactivation. This likely induces intracellular Ca(2+) overload in multiple cell types. In the heart, prolonged Ca(2+) current delays cardiomyocyte repolarization and increases risk of arrhythmia, the ultimate cause of death in this disorder. These discoveries establish the importance of Ca(V)1.2 in human physiology and development and implicate Ca(2+) signaling in autism.
- Published
- 2004
18. Compound Mutations
- Author
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Michael C. Sanguinetti, Mark T. Keating, Katherine W. Timothy, Peter D. Westenskow, and Igor Splawski
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Male ,Proband ,ERG1 Potassium Channel ,medicine.medical_specialty ,Patch-Clamp Techniques ,Potassium Channels ,Long QT syndrome ,hERG ,medicine.disease_cause ,Sudden death ,QT interval ,Ion Channels ,Sodium Channels ,NAV1.5 Voltage-Gated Sodium Channel ,Xenopus laevis ,Physiology (medical) ,Internal medicine ,medicine ,Animals ,Humans ,KvLQT1 ,Cells, Cultured ,Genetics ,Mutation ,KCNQ Potassium Channels ,biology ,business.industry ,Electric Conductivity ,KCNE2 ,medicine.disease ,Ether-A-Go-Go Potassium Channels ,Pedigree ,Long QT Syndrome ,Endocrinology ,Potassium Channels, Voltage-Gated ,KCNQ1 Potassium Channel ,Mutagenesis, Site-Directed ,biology.protein ,Female ,Cardiology and Cardiovascular Medicine ,business - Abstract
Background— Long QT syndrome (LQTS) predisposes affected individuals to sudden death from cardiac arrhythmias. Although most LQTS individuals do not have cardiac events, significant phenotypic variability exists within families. Probands can be very symptomatic. The mechanism of this phenotypic variability is not understood. Methods and Results— Genetic analyses of KVLQT1, HERG , KCNE1 , KCNE2 , and SCN5A detected compound mutations in 20 of 252 LQTS probands (7.9%). Carriers of 2 mutations had longer QTc intervals (527±54 versus 489±44 ms; P P P Xenopus oocytes was used to characterize the properties of variant slow delayed rectifier potassium ( I Ks ) channels identified in 7 of the probands. When wild-type and variant subunits were coexpressed in appropriate ratios to mimic the genotype of the proband, the reduction in I Ks density was equivalent to the additive effects of the single mutations. Conclusions— LQTS-associated compound mutations cause a severe phenotype and are more common than expected. Individuals with compound mutations need to be identified, and their management should be tailored to their increased risk for arrhythmias.
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- 2004
19. Location of Mutation in the KCNQ1 and Phenotypic Presentation of Long QT Syndrome
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Peter J. Schwartz, Carlo Napolitano, G. Michael Vincent, Arthur J. Moss, Wojciech Zareba, Jeffrey A. Towbin, Gloria Sheu, Silvia G. Priori, Mark L. Andrews, Jesaia Benhorin, Elizabeth S. Kaufman, Mark T. Keating, W. Jackson Hall, Jennifer L. Robinson, and Ming Qi
- Subjects
Adult ,Male ,medicine.medical_specialty ,Potassium Channels ,Long QT syndrome ,Molecular Sequence Data ,hERG ,medicine.disease_cause ,Risk Assessment ,QT interval ,Sudden death ,Disease-Free Survival ,Electrocardiography ,Sequence Analysis, Protein ,Physiology (medical) ,Internal medicine ,Humans ,Medicine ,Genetic Predisposition to Disease ,Amino Acid Sequence ,Gene ,Genetics ,Mutation ,KCNQ Potassium Channels ,biology ,business.industry ,Gene Expression Profiling ,medicine.disease ,Phenotype ,United States ,Long QT Syndrome ,Potassium Channels, Voltage-Gated ,KCNQ1 Potassium Channel ,biology.protein ,Cardiology ,Population study ,Female ,Cardiology and Cardiovascular Medicine ,business ,Sequence Alignment - Abstract
Introduction: Recent data showed that long QT syndrome (LQTS) patients with mutations in the pore region of the HERG (LQT2) gene have significantly higher risk of cardiac events than subjects with mutations in the non-pore region. The aim of this study was to determine whether there is an association between the location of mutations in the KCNQ1 gene and cardiac events in LQT1 patients. Methods and Results: The study population consisted of 294 LQT1 patients with KCNQ1 gene mutations. Demographic, clinical, and follow-up information was compared among subjects with different locations of KCNQ1 mutations defined as pre-pore region including N-terminus (1–278), pore region (279–354), and post-pore region including C-terminus (>354). Cardiac events observed during follow-up from birth until age of last contact or age 40 years were defined as syncope, cardiac arrest, or sudden death. There were 164 (56%) LQT1 patients with pre-pore mutations, 101 (34%) with pore mutations, and 29 (10%) with post-pore mutations. QTc duration did not differ significantly among the three subgroups (mean QTc = 494, 487, and 501 ms, respectively). There was no significant difference between groups with regard to the risk of cardiac events by age 40 years. Conclusion: There are no significant differences in clinical presentation, ECG parameters, and cardiac events among LQT1 patients with different locations of KCNQ1 mutations. These findings indicate that factors other than location of mutation influence clinical phenotype in patients with LQT1 mutations. (J Cardiovasc Electrophysiol, Vol. 14, pp. 1149-1153, November 2003)
- Published
- 2003
20. GTF2I hemizygosity implicated in mental retardation in Williams syndrome: Genotype-phenotype analysis of five families with deletions in the Williams syndrome region
- Author
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Patricia A. Spallone, Annemarie Sommer, Holly H. Hobart, Carolyn B. Mervis, Jacquelyn Bertrand, Gregory J. Ensing, Colleen A. Morris, Mark T. Keating, Cynthia A. Moore, Ronald G. Gregg, Lucy R. Osborne, Kendra W. Kimberley, Robert J. Hopkin, and A. Dean Stock
- Subjects
Adult ,Male ,Williams Syndrome ,Adolescent ,Genotype ,Loss of Heterozygosity ,Hemizygosity ,Protein Serine-Threonine Kinases ,LIMK1 ,Biology ,Loss of heterozygosity ,Transcription Factors, TFII ,Intellectual Disability ,medicine ,Humans ,Child ,Genetics (clinical) ,Intelligence Tests ,Genetics ,Lim Kinases ,medicine.disease ,Phenotype ,Pedigree ,DNA-Binding Proteins ,Developmental disorder ,Child, Preschool ,Female ,Williams syndrome ,Chromosome Deletion ,Haploinsufficiency ,Protein Kinases ,Chromosomes, Human, Pair 7 - Abstract
Most individuals with Williams syndrome (WS) have a 1.6 Mb deletion in chromosome 7q11.23 that encompasses the elastin (ELN) gene, while most families with autosomal dominant supravalvar aortic stenosis (SVAS) have point mutations in ELN. The overlap of the clinical phenotypes of the two conditions (cardiovascular disease and connective tissue abnormalities such as hernias) is due to the effect of haploinsufficiency of ELN. SVAS families often have affected individuals with some WS facial features, most commonly in infancy, suggesting that ELN plays a role in WS facial gestalt as well. To find other genes contributing to the WS phenotype, we studied five families with SVAS who have small deletions in the WS region. None of the families had mental retardation, but affected family members had the Williams Syndrome Cognitive Profile (WSCP). All families shared a deletion of LIMK1, which encodes a protein strongly expressed in the brain, supporting the hypothesis that LIMK1 hemizygosity contributes to impairment in visuospatial constructive cognition. While the deletions from the families nearly spanned the WS region, none had a deletion of FKBP6 or GTF2I, suggesting that the mental retardation seen in WS is associated with deletion of either the centromeric and/or telomeric portions of the region. Comparison of these five families with reports of other individuals with partial deletions of the WS region most strongly implicates GTF2I in the mental retardation of WS.
- Published
- 2003
21. Positional cloning of a temperature-sensitive mutant emmental reveals a role for sly1 during cell proliferation in zebrafish fin regeneration
- Author
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Stephen L. Johnson, Kenneth D. Poss, Alex Nechiporuk, and Mark T. Keating
- Subjects
Male ,DNA, Complementary ,Positional cloning ,Cell division ,Molecular Sequence Data ,Mutant ,Gene Expression ,Biology ,Fin regeneration ,03 medical and health sciences ,0302 clinical medicine ,Sequence Homology, Nucleic Acid ,Genetics ,Animals ,Regeneration ,Amino Acid Sequence ,Blastema ,Cloning, Molecular ,Molecular Biology ,Zebrafish ,In Situ Hybridization ,030304 developmental biology ,0303 health sciences ,Base Sequence ,Sequence Homology, Amino Acid ,Sly1 ,Regeneration (biology) ,Fin ,Temperature ,Chromosome Mapping ,emmental ,Extremities ,Cell Biology ,Zebrafish Proteins ,biology.organism_classification ,Temperature-sensitive mutant ,Molecular biology ,Mutation ,Female ,Laminin ,Cell Division ,030217 neurology & neurosurgery ,Developmental Biology - Abstract
Here, we used classical genetics in zebrafish to identify temperature-sensitive mutants in caudal fin regeneration. Gross morphological, histological, and molecular analyses revealed that one of these strains, emmental (emm), failed to form a functional regeneration blastema. Inhibition of emm function by heat treatment during regenerative outgrowth rapidly blocked regeneration. This block was associated with reduced proliferation in the proximal blastema and expansion of the nonproliferative distal blastemal zone. Positional cloning revealed that the emm phenotype is caused by a mutation in the orthologue of yeast sly1, a gene product involved in protein trafficking. sly1 is upregulated in the newly formed blastema as well as during regenerative outgrowth. Thus, sly1 is essential for blastemal organization and proliferation during two stages of fin regeneration.
- Published
- 2003
22. Increased Risk of Arrhythmic Events in Long-QT Syndrome With Mutations in the Pore Region of the Human Ether-a-go-go–Related Gene Potassium Channel
- Author
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Eric J. Gartman, Derick R. Peterson, Elizabeth S. Kaufman, Aharon Medina, W. Jackson Hall, Jeffrey A. Towbin, Li Zhang, Wojciech Zareba, Jennifer L. Robinson, Jesaia Benhorin, Mark L. Andrews, Peter J. Schwartz, G. Michael Vincent, Changyong Feng, Mark T. Keating, Zhiqing Wang, Silvia G. Priori, and Arthur J. Moss
- Subjects
Male ,Models, Molecular ,ERG1 Potassium Channel ,Potassium Channels ,DNA Mutational Analysis ,medicine.disease_cause ,Electrocardiography ,Odds Ratio ,Registries ,Cation Transport Proteins ,Mutation ,biology ,Prognosis ,Potassium channel ,DNA-Binding Proteins ,Long QT Syndrome ,Phenotype ,Potassium Channels, Voltage-Gated ,Ether-A-Go-Go Potassium Channels ,Disease Progression ,Regression Analysis ,Female ,Cardiology and Cardiovascular Medicine ,Adult ,medicine.medical_specialty ,Adolescent ,Long QT syndrome ,hERG ,Risk Assessment ,Sudden death ,QT interval ,Transcriptional Regulator ERG ,Physiology (medical) ,Internal medicine ,medicine ,Humans ,Gene ,Proportional Hazards Models ,Binding Sites ,business.industry ,Arrhythmias, Cardiac ,medicine.disease ,Survival Analysis ,Endocrinology ,Trans-Activators ,biology.protein ,business ,Follow-Up Studies - Abstract
Background — The hereditary long-QT syndrome is characterized by prolonged ventricular repolarization and a variable clinical course with arrhythmia-related syncope and sudden death. Mutations involving the human ether-a-go-go–related gene (HERG) channel are responsible for the LQT2 form of long-QT syndrome, and in cellular expression studies these mutations are associated with reduction in the rapid component of the delayed rectifier repolarizing current (I Kr ). We investigated the clinical features and prognostic implications of mutations involving pore and nonpore regions of the HERG channel in the LQT2 form of this disorder. Methods and Results — A total of 44 different HERG mutations were identified in 201 subjects, with 14 mutations located in the pore region (amino acid residues 550 through 650). Thirty-five subjects had mutations in the pore region and 166 in nonpore regions. Follow-up extended through age 40 years. Subjects with pore mutations had more severe clinical manifestations of the genetic disorder and experienced a higher frequency (74% versus 35%; P P Conclusion — Patients with mutations in the pore region of the HERG gene are at markedly increased risk for arrhythmia-related cardiac events compared with patients with nonpore mutations.
- Published
- 2002
23. ETL, a Novel Seven-transmembrane Receptor That Is Developmentally Regulated in the Heart
- Author
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Lisa D. Urness, Mark T. Keating, and Tamilla Nechiporuk
- Subjects
Differential display ,COS cells ,Epidermal growth factor ,Extracellular ,Cell Biology ,Secretin family ,Biology ,Receptor ,Molecular Biology ,Biochemistry ,Molecular biology ,Peptide sequence ,Transmembrane protein - Abstract
Using differential display of rat fetal and postnatal cardiomyocytes, we have identified a novel seven-transmembrane receptor, ETL. The cDNA-predicted amino acid sequence of ETL indicated that it encodes a 738-aa protein composed of a large extracellular domain with epidermal growth factor (EGF)-like repeats, a seven-transmembrane domain, and a short cytoplasmic tail. ETL belongs to the secretin family of G-protein-coupled peptide hormone receptors and the EGF-TM7 subfamily of receptors. The latter are characterized by a variable number of extracellular EGF and cell surface domains and conserved seven transmembrane-spanning regions. ETL mRNA expression is up-regulated in the adult rat and human heart. In situ hybridization analyses revealed expression in rat cardiomyocytes and abundant expression in vascular and bronchiolar smooth muscle cells. In COS-7 cells transfected with Myc-tagged rat ETL, rat ETL exists as a stable dimer and undergoes endoproteolytic cleavage of the extracellular domain. The proteolytic activity can be abolished by a specific mutation, T455A, in this domain. In transfected mammalian cells, ETL is associated with cell membranes and is also observed in cytoplasmic vesicles. ETL is the first seven-transmembrane receptor containing EGF-like repeats that is developmentally regulated in the heart.
- Published
- 2001
24. Dedifferentiation of Mammalian Myotubes Induced by msx1
- Author
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Angela Kollhoff, Shannon J. Odelberg, and Mark T. Keating
- Subjects
Cellular differentiation ,Muscle Fibers, Skeletal ,Gene Expression ,Muscle Proteins ,Biology ,MyoD ,General Biochemistry, Genetics and Molecular Biology ,Mice ,Multinucleate ,Animals ,Regeneration ,Myogenin ,Homeodomain Proteins ,MSX1 Transcription Factor ,Mammals ,Biochemistry, Genetics and Molecular Biology(all) ,Myogenesis ,Stem Cells ,food and beverages ,Cell Differentiation ,Clone Cells ,Cell biology ,Adipogenesis ,Cancer research ,Ectopic expression ,C2C12 ,Cell Division ,Signal Transduction ,Transcription Factors - Abstract
The process of cellular differentiation culminating in terminally differentiated mammalian cells is thought to be irreversible. Here, we present evidence that terminally differentiated murine myotubes can be induced to dedifferentiate. Ectopic expression of msx1 in C2C12 myotubes reduced the nuclear muscle proteins MyoD, myogenin, MRF4, and p21 to undetectable levels in 20%–50% of the myotubes. Approximately 9% of the myotubes cleave to produce either smaller multinucleated myotubes or proliferating, mononucleated cells. Finally, clonal populations of the myotube-derived mononucleated cells can be induced to redifferentiate into cells expressing chondrogenic, adipogenic, myogenic, and osteogenic markers. These results suggest that terminally differentiated mammalian myotubes can dedifferentiate when stimulated with the appropriate signals and that msx1 can contribute to the dedifferentiation process.
- Published
- 2000
25. Spectrum of Mutations in Long-QT Syndrome Genes
- Author
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Jennifer L. Robinson, Peter J. Schwartz, Michael H. Lehmann, G. Michael Vincent, Igor Splawski, Arthur J. Moss, Silvia G. Priori, Jiaxiang Shen, Mark T. Keating, Katherine W. Timothy, and Jeffrey A. Towbin
- Subjects
Adult ,Male ,congenital, hereditary, and neonatal diseases and abnormalities ,medicine.medical_specialty ,Adolescent ,Genotype ,Long QT syndrome ,DNA Mutational Analysis ,hERG ,Mutation, Missense ,Sudden death ,QT interval ,Physiology (medical) ,Internal medicine ,medicine ,Humans ,KvLQT1 ,Child ,Frameshift Mutation ,Aged ,biology ,business.industry ,KCNE2 ,Middle Aged ,medicine.disease ,Romano–Ward syndrome ,Long QT Syndrome ,Jervell and Lange-Nielsen syndrome ,Phenotype ,Endocrinology ,biology.protein ,Cardiology ,Female ,Cardiology and Cardiovascular Medicine ,business - Abstract
Background —Long-QT Syndrome (LQTS) is a cardiovascular disorder characterized by prolongation of the QT interval on ECG and presence of syncope, seizures, and sudden death. Five genes have been implicated in Romano-Ward syndrome, the autosomal dominant form of LQTS: KVLQT1 , HERG , SCN5A , KCNE1 , and KCNE2 . Mutations in KVLQT1 and KCNE1 also cause the Jervell and Lange-Nielsen syndrome, a form of LQTS associated with deafness, a phenotypic abnormality inherited in an autosomal recessive fashion. Methods and Results —We used mutational analyses to screen a pool of 262 unrelated individuals with LQTS for mutations in the 5 defined genes. We identified 134 mutations in addition to the 43 that we previously reported. Eighty of the mutations were novel. The total number of mutations in this population is now 177 (68% of individuals). Conclusions — KVLQT1 (42%) and HERG (45%) accounted for 87% of identified mutations, and SCN5A (8%), KCNE1 (3%), and KCNE2 (2%) accounted for the other 13%. Missense mutations were most common (72%), followed by frameshift mutations (10%), in-frame deletions, and nonsense and splice-site mutations (5% to 7% each). Most mutations resided in intracellular (52%) and transmembrane (30%) domains; 12% were found in pore and 6% in extracellular segments. In most cases (78%), a mutation was found in a single family or an individual.
- Published
- 2000
26. Complete physical map of the common deletion region in Williams syndrome and identification and characterization of three novel genes
- Author
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Xun Meng, Hillary Massa, Eric D. Green, Zhizhong Li, Colleen A. Morris, Xiaojun Lu, Mark T. Keating, and Barbara J. Trask
- Subjects
Williams Syndrome ,Sequence analysis ,DNA Mutational Analysis ,Molecular Sequence Data ,Hemizygosity ,Biology ,Homology (biology) ,Gene mapping ,GTP-Binding Proteins ,Genetics ,medicine ,Humans ,Amino Acid Sequence ,Transducin ,Gene ,In Situ Hybridization, Fluorescence ,Genetics (clinical) ,Base Sequence ,Contig ,Basic Helix-Loop-Helix Leucine Zipper Transcription Factors ,Helix-Loop-Helix Motifs ,Membrane Proteins ,Proteins ,Sequence Analysis, DNA ,Physical Chromosome Mapping ,medicine.disease ,Elastin ,DNA-Binding Proteins ,Williams syndrome ,DNA Probes ,Haploinsufficiency ,Sequence Alignment ,Chromosomes, Human, Pair 7 ,Gene Deletion ,Microsatellite Repeats - Abstract
Williams syndrome (WS) is a contiguous gene deletion disorder caused by haploinsufficiency of genes at 7q11.23. We have shown that hemizygosity of elastin is responsible for one feature of WS, supravalvular aortic stenosis (SVAS). We have also implicated LIM-kinase 1 hemizygosity as a contributing factor to impaired visual-spatial constructive cognition in WS. However, the common WS deletion region has not been completely characterized, and genes for additional features of WS, including mental retardation, infantile hypercalcemia, and unique personality profile, are yet to be discovered. Here, we present a physical map encompassing 1.5 Mb DNA that is commonly deleted in individuals with WS. Fluorescence in situ hybridization analysis of 200 WS individuals shows that WS individuals have the consistent deletion interval. In addition, we identify three novel genes from the common deletion region: WS-betaTRP, WS-bHLH, and BCL7B. WS-betaTRP has four putative beta-transducin (WD40) repeats, and WS-bHLH is a novel basic helix-loop-helix leucine zipper (bHLHZip) gene. BCL7B belongs to a novel family of highly conserved genes. We describe the expression profile and genomic structure for each of these genes. Hemizygous deletion of one or more of these genes may contribute to developmental defects in WS.
- Published
- 1998
27. Influence of the Genotype on the Clinical Course of the Long-QT Syndrome
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Wojciech Zareba, Arthur J. Moss, Peter J. Schwartz, G. Michael Vincent, Jennifer L. Robinson, Silvia G. Priori, Jesaia Benhorin, Emanuela H. Locati, Jeffrey A. Towbin, Mark T. Keating, Michael H. Lehmann, W. Jackson Hall, Mark L. Andrews, Carlo Napolitano, Katherine Timothy, Li Zhang, Aharon Medina, and Jean W. MacCluer
- Subjects
Genetics ,congenital, hereditary, and neonatal diseases and abnormalities ,biology ,business.industry ,Long QT syndrome ,hERG ,Locus (genetics) ,General Medicine ,medicine.disease ,QT interval ,Sudden death ,Locus heterogeneity ,Genotype ,biology.protein ,Medicine ,KvLQT1 ,business - Abstract
Background The congenital long-QT syndrome, caused by mutations in cardiac potassium-channel genes (KVLQT1 at the LQT1 locus and HERG at the LQT2 locus) and the sodium-channel gene (SCN5A at the LQT3 locus), has distinct repolarization patterns on electrocardiography, but it is not known whether the genotype influences the clinical course of the disease. Methods We determined the genotypes of 541 of 1378 members of 38 families enrolled in the International Long-QT Syndrome Registry: 112 had mutations at the LQT1 locus, 72 had mutations at the LQT2 locus, and 62 had mutations at the LQT3 locus. We determined the cumulative probability and lethality of cardiac events (syncope, aborted cardiac arrest, or sudden death) occurring from birth through the age of 40 years according to genotype in the 246 gene carriers and in all 1378 members of the families studied. Results The frequency of cardiac events was higher among subjects with mutations at the LQT1 locus (63 percent) or the LQT2 locus (46 percent) than am...
- Published
- 1998
28. A Novel Human GeneFKBP6Is Deleted in Williams Syndrome
- Author
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Xiaojun Lu, Mark T. Keating, Xun Meng, and Colleen A. Morris
- Subjects
Williams Syndrome ,Molecular Sequence Data ,Gene Expression ,Hemizygosity ,Biology ,Tacrolimus Binding Proteins ,Exon ,Genetics ,medicine ,Humans ,Amino Acid Sequence ,Immunophilins ,Base Sequence ,Sequence Homology, Amino Acid ,Exons ,Sequence Analysis, DNA ,Physical Chromosome Mapping ,medicine.disease ,Introns ,Tetratricopeptide ,FKBP ,Genes ,Cosmid ,Williams syndrome ,Chromosome Deletion ,Haploinsufficiency ,Sequence Alignment ,Supravalvular aortic stenosis ,Chromosomes, Human, Pair 7 ,Gene Deletion - Abstract
Williams syndrome (WS) is a developmental disorder caused by haploinsufficiency of genes at 7q11.23. We have shown that hemizygosity of elastin is responsible for one feature of WS, supravalvular aortic stenosis. We have also implicated LIM-kinase 1 hemizygosity as a contributing factor to impaired visual–spatial constructive cognition in WS. Here we identify and characterize a novel gene, FKBP6, within the common WS deletion region. FKBP6 shows homology to the FK-506 binding protein (FKBP) class of immunophilins. FKBP6 has a putative N-terminal FK-506 binding and peptidylproyl isomerase (rotamase) domain and, like known high-molecular-weight FKBPs, an imperfect C-terminal tetratricopeptide repeat domain. FKBP6 is expressed in testis, heart, skeletal muscle, liver, and kidney. FKBP6 consists of nine exons and is completely contained within a 35-kb cosmid clone. Fluorescence in situ hybridization experiments show that FKBP6 gene is deleted in 40/40 WS individuals. Hemizygous deletion of FKBP6 may contribute to certain defects such as hypercalcemia and growth delay in WS.
- Published
- 1998
29. Genetic basis and molecular mechanism for idiopathic ventricular fibrillation
- Author
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Angel Moya, Charles Antzelevitch, Qiuyun Chen, Ramon Brugada, Qing Wang, Eric Schulze-Bahr, Jeffrey A. Towbin, Rocio Ortiz-Lopez, Martin Borggrefe, Josep Brugada, Glenn E. Kirsch, Mark T. Keating, Domenico Potenza, Richard E. O'Brien, Pedro Brugada, Zhiqing Wang, Günter Breithardt, and Danmei Zhang
- Subjects
Male ,medicine.medical_specialty ,Xenopus ,DNA Mutational Analysis ,Action Potentials ,Nav1.5 ,Sudden death ,Protein Structure, Secondary ,Sodium Channels ,NAV1.5 Voltage-Gated Sodium Channel ,Frameshift mutation ,Electrocardiography ,Internal medicine ,medicine ,Animals ,Humans ,Missense mutation ,Frameshift Mutation ,Polymorphism, Single-Stranded Conformational ,Brugada syndrome ,Multidisciplinary ,biology ,Short QT syndrome ,medicine.disease ,Recombinant Proteins ,Pedigree ,Electrophysiology ,Kinetics ,Endocrinology ,Mutation ,Ventricular Fibrillation ,Ventricular fibrillation ,cardiovascular system ,biology.protein ,Cardiology ,Female ,Ion Channel Gating ,Familial atrial fibrillation - Abstract
Ventricular fibrillation causes more than 300,000 sudden deaths each year in the USA alone. In approximately 5-12% of these cases, there are no demonstrable cardiac or non-cardiac causes to account for the episode, which is therefore classified as idiopathic ventricular fibrillation (IVF). A distinct group of IVF patients has been found to present with a characteristic electrocardiographic pattern. Because of the small size of most pedigrees and the high incidence of sudden death, however, molecular genetic studies of IVF have not yet been done. Because IVF causes cardiac rhythm disturbance, we investigated whether malfunction of ion channels could cause the disorder by studying mutations in the cardiac sodium channel gene SCN5A. We have now identified a missense mutation, a splice-donor mutation, and a frameshift mutation in the coding region of SCN5A in three IVF families. We show that sodium channels with the missense mutation recover from inactivation more rapidly than normal and that the frameshift mutation causes the sodium channel to be non-functional. Our results indicate that mutations in cardiac ion-channel genes contribute to the risk of developing IVF.
- Published
- 1998
30. On the trail of genetic culprits in Williams syndrome
- Author
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Mark T. Keating
- Subjects
Williams Syndrome ,Genetics ,Positional cloning ,Physiology ,Infant, Newborn ,Chromosome ,Biology ,Genetic code ,DNA sequencing ,Elastin ,Drug Hypersensitivity ,chemistry.chemical_compound ,Phenotype ,chemistry ,Physiology (medical) ,Humans ,Human genome ,Vitamin D ,Cardiology and Cardiovascular Medicine ,Gene ,Gene Deletion ,DNA ,Sequence (medicine) - Abstract
Time for primary review 21 days. In times past—in point of fact, not very long ago: only in the years after the genetic code was deciphered—the genetic basis of certain human diseases could only be extrapolated from knowledge of biochemical correlates. A critical enzyme was missing, for example, as in phenylketonuria, or a defective hemoglobin resulted in sickle-cell anemia. Determining the DNA sequence of a defective gene was a worthwhile exercise though, because if the basis for a disorder could be identified at the coding level, investigators might be able to devise novel approaches to prevention or treatment. But for hundreds, even thousands, of heritable disorders, not to speak of common and apparently sporadic illnesses, first causes remained mysterious; with no known protein culprit, then, how could the responsible (gene)s be discovered and the physiological consequences of mutations be evaluated? One solution—‘molecular genetics’, a major advance in molecular biology, using recombinant DNA technology to map the human genome with anonymous (non-gene) DNA markers—has gained astonishing speed within the past 15 years [1]. Localization of markers—now available in thousands—to chromosomes permits investigators to track inherited diseases in pedigrees according to linkage (i.e., co-inheritance) of a defective allele to a marker of known location [2]. As regards cardiovascular diseases, the linkage approach led to the mapping of three loci that can carry mutations responsible for long QT syndrome, on chromosomes 11p15.5, 7q35–36, and 3p21–24, respectively [3–5]. Once the site on a chromosome is determined, techniques of manipulating fragments of DNA come into play until a specific gene in the region can be shown to contain abnormalities in structure or sequence in affected family members as compared to normal individuals. Using this strategy, known as ‘positional cloning’, we eventually identified the LQT genes on 7q as HERG , a putative …
- Published
- 1997
31. The IPL Gene on Chromosome 11p15.5 is Imprinted in Humans and Mice and is Similar to TDAG51, Implicated in Fas Expression and Apoptosis
- Author
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Long Zhao, Qing Wang, Benjamin Tycko, Denise S. O'Keefe, Mark T. Keating, Naifeng Qian, Dale Frank, Colum P. Walsh, Diem Dao, and Luwa Yuan
- Subjects
Male ,Placenta ,Molecular Sequence Data ,Gene Expression ,Apoptosis ,Biology ,Genomic Imprinting ,Mice ,Gene mapping ,Gene expression ,Genetics ,Animals ,Humans ,Amino Acid Sequence ,fas Receptor ,Cloning, Molecular ,Imprinting (psychology) ,Molecular Biology ,Gene ,Genetics (clinical) ,Chromosome 7 (human) ,Base Sequence ,Chromosomes, Human, Pair 11 ,Intron ,Chromosome Mapping ,Nuclear Proteins ,Proteins ,Sequence Analysis, DNA ,General Medicine ,Fas receptor ,Molecular biology ,Mice, Inbred C57BL ,Liver ,Organ Specificity ,Female ,sense organs ,Genomic imprinting - Abstract
We searched for novel imprinted genes in a region of human chromosome 11p15.5, which contains several known imprinted genes. Here we describe the cloning and characterization of the IPL ( I mprinted in P lacenta and L iver) gene, which shows tissue-specific expression and functional imprinting, with the maternal allele active and the paternal allele relatively inactive, in many human and mouse tissues. Human IPL is highly expressed in placenta and shows low but detectable expression in fetal and adult liver and lung. Mouse Ipl maps to the region of chromosome 7 which is syntenic with human 11p15.5 and this gene is expressed in placenta and at higher levels in extraembryonic membranes (yolk sac), fetal liver and adult kidney. Mouse and human IPL show sequence similarity to TDAG51 , a gene which was shown to be essential for Fas expression and susceptibility to apoptosis in a T lymphocyte cell line. Like several other imprinted genes, mouse and human IPL genes are small and contain small introns. These data expand the repertoire of known imprinted genes and will be helpful in testing the mechanism of genomic imprinting and the role of imprinted genes in growth regulation.
- Published
- 1997
32. Role of Delayed Rectifier Potassium Channels in Cardiac Repolarization and Arrhythmias
- Author
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Mark T. Keating and Michael C. Sanguinetti
- Subjects
Cardiac transient outward potassium current ,medicine.medical_specialty ,Atrial action potential ,Physiology ,Potassium ,chemistry.chemical_element ,Cardiac action potential ,Cardiac repolarization ,Delayed Rectifier Potassium Channels ,chemistry ,Internal medicine ,cardiovascular system ,medicine ,Cardiology ,Repolarization - Abstract
Cardiac action potentials are long because the magnitude of some potassium currents is reduced at depolarized potentials. The slow onset of repolarization is initiated by the opening of delayed rectifier potassium channels. A decrease in function of these channels resulting from gene mutations or pharmacological block increases risk of life-threatening ventricular arrhythmias.
- Published
- 1997
33. Defining the Molecular Genetic Basis of Idiopathic Dilated Cardiomyopathy
- Author
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Timothy M. Olson and Mark T. Keating
- Subjects
Genetics ,medicine.medical_specialty ,business.industry ,Pedigree chart ,Dilated cardiomyopathy ,Disease ,musculoskeletal system ,medicine.disease ,complex mixtures ,Pathogenesis ,Molecular genetics ,Idiopathic dilated cardiomyopathy ,cardiovascular system ,Etiology ,Medicine ,cardiovascular diseases ,Cardiology and Cardiovascular Medicine ,business ,Gene - Abstract
Dilated cardiomyopathy (DCM) is a significant health care problem. The etiology is idiopathic in approximately half of the patients. Recognition that 20%–25% of idiopathic DCM cases are familial has advanced the hypothesis that single gene defects are important in the disease's pathogenesis. General linkage analyses in rare, large DCM families have determined the chromosome location of five idiopathic DCM genes. Candidate-gene mutational analyses in more typical, small pedigrees represent an alternative strategy for DCM gene identification. Human molecular genetics will play a fundamental role in defining pathogenic mechanisms for DCM with the prospect of new, molecular-based diagnostic and therapeutic approaches . (Trends Cardiovasc Med 1997;7:60–63). © 1997, Elsevier Science Inc .
- Published
- 1997
34. Age-Gender Influence on the Rate-Corrected QT Interval and the QT-Heart Rate Relation in Families With Genotypically Characterized Long QT Syndrome
- Author
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Michael H. Lehmann, Katherine W. Timothy, Arthur J. Moss, R. Thomas Taggart, Debra Frankovich, Barbara S. Fromm, Emanuela H. Locati, Jeffrey A. Towbin, Mark T. Keating, Peter J. Schwartz, and G. Michael Vincent
- Subjects
Adult ,Male ,medicine.medical_specialty ,Adolescent ,Genotype ,Heart disease ,Genetic Linkage ,Heart block ,Long QT syndrome ,QT interval ,Electrocardiography ,Sex Factors ,Heart Rate ,Torsades de Pointes ,Internal medicine ,Heart rate ,medicine ,Humans ,cardiovascular diseases ,Child ,medicine.diagnostic_test ,business.industry ,Chromosomes, Human, Pair 11 ,Age Factors ,Corrected qt ,medicine.disease ,Long QT Syndrome ,Endocrinology ,Cardiology ,Regression Analysis ,Interval (graph theory) ,Female ,Chromosomes, Human, Pair 3 ,business ,Cardiology and Cardiovascular Medicine ,Chromosomes, Human, Pair 7 - Abstract
Objectives. We sought to analyze age-gender differences in the rate-corrected QT (QTc) interval in the presence of a QT-prolonging gene.Background. Compared with men, women exhibit a longer QTc interval and an increased propensity toward torsade de pointes. In normal subjects, the QTc gender difference reflects QTc interval shortening in men during adolescence.Methods. QTc intervals were analyzed according to age (
- Published
- 1997
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35. Genetically Defined Therapy of Inherited Long-QT Syndrome
- Author
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Steve J. Compton, Katie R. Strelich, Larry S. Green, Matthew R. Ramsey, Robert L. Lux, Jay W. Mason, Michael C. Sanguinetti, and Mark T. Keating
- Subjects
Adult ,Male ,medicine.medical_specialty ,Genetic Linkage ,Heart block ,Long QT syndrome ,hERG ,QT interval ,Electrocardiography ,Physiology (medical) ,Internal medicine ,medicine ,Humans ,Repolarization ,Sinus rhythm ,medicine.diagnostic_test ,biology ,business.industry ,Middle Aged ,medicine.disease ,Potassium channel ,Long QT Syndrome ,Endocrinology ,Potassium ,biology.protein ,Female ,Cardiology and Cardiovascular Medicine ,business ,Chromosomes, Human, Pair 7 - Abstract
Background Many members of families with inherited long-QT (LQT) syndrome have mutations in HERG , a gene encoding a cardiac potassium channel that is modulated by extracellular potassium. We hypothesized that an increase in serum potassium would normalize repolarization in these patients. Methods and Results We studied seven subjects with chromosome 7–linked LQT syndrome and five normal control subjects. Repolarization was measured by ECG and body surface potential mapping during sinus rhythm, exercise, and atrial pacing, before and after serum potassium increase. Potassium administration improved repolarization in the LQT syndrome. At baseline, LQT subjects differed from control subjects: resting corrected QT interval (QT c , 627±90 versus 425±25 ms, P =.0007), QT c dispersion (133±62 versus 36±9 ms, P =.009), QT/RR slope (0.35±0.08 versus 0.24±0.07, P =.04), and global root-mean-square QT interval (RMS-QT c ; 525±68 versus 393±22, P =.002). All LQT subjects had biphasic or notched T waves. After administration of potassium, the LQT group had a 24% reduction in resting QT c interval (from 617±92 to 469±23 ms, P =.004) compared with a 4% reduction among control subjects (from 425±25 to 410±45 ms, P >.05). The reduction was significantly greater in LQT subjects ( P =.018). QT dispersion became normal in LQT subjects and did not change in control subjects. The slope of the relation between QT interval and cycle length (QT/RR slope) decreased toward normal. T-wave morphology improved in six of seven LQT subjects. The LQT group had a greater reduction in RMS-QT c than control subjects ( P =.04). Conclusions An increase in serum potassium corrects abnormalities of repolarization duration, T-wave morphology, QT/RR slope, and QT dispersion in patients with chromosome 7–linked LQT.
- Published
- 1996
36. Genomic Organization of the HumanSCN5AGene Encoding the Cardiac Sodium Channel
- Author
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Zhizhong Li, Mark T. Keating, Jiaxiang Shen, and Qing Wang
- Subjects
congenital, hereditary, and neonatal diseases and abnormalities ,Candidate gene ,Molecular Sequence Data ,Locus (genetics) ,Biology ,Gene mutation ,Sudden death ,Sodium Channels ,NAV1.5 Voltage-Gated Sodium Channel ,Evolution, Molecular ,Exon ,Gene mapping ,Genetics ,Humans ,Amino Acid Sequence ,cardiovascular diseases ,Cloning, Molecular ,Repetitive Sequences, Nucleic Acid ,Genomic organization ,Polymorphism, Genetic ,Base Sequence ,Intron ,Exons ,Sequence Analysis, DNA ,Introns ,Long QT Syndrome ,Mutation ,cardiovascular system - Abstract
The voltage-gated cardiac sodium channel, SCN5A, is responsible for the initial upstroke of the action potential. Mutations in the human SCN5A gene cause susceptibility to cardiac arrhythmias and sudden death in the long QT syndrome (LQT). In this report we characterize the genomic structure of SCN5A. SCN5A consists of 28 exons spanning approximately 80 kb on chromosome 3p21. We describe the sequences of all intron/exon boundaries and a dinucleotide repeat polymorphism in intron 16. Oligonucleotide primers based on exon-flanking sequences amplify all SCN5A exons by PCR. This work establishes the complete genomic organization of SCN5A and will enable high-resolution analyses of this locus for mutations associated with LQT and other phenotypes for which SCN5A may be a candidate gene. 40 refs., 4 figs., 2 tabs.
- Published
- 1996
37. Class III Antiarrhythmic Drugs Block HERG, a Human Cardiac Delayed Rectifier K + Channel
- Author
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Mark T. Keating, Michael C. Sanguinetti, Mark E. Curran, and Peter S. Spector
- Subjects
ERG1 Potassium Channel ,congenital, hereditary, and neonatal diseases and abnormalities ,Patch-Clamp Techniques ,Potassium Channels ,Pyridines ,Physiology ,Xenopus ,Long QT syndrome ,hERG ,Gating ,Pharmacology ,chemistry.chemical_compound ,Piperidines ,Transcriptional Regulator ERG ,Potassium Channel Blockers ,medicine ,Animals ,Humans ,Myocyte ,Benzopyrans ,cardiovascular diseases ,Cation Transport Proteins ,Cells, Cultured ,Ion transporter ,biology ,Chemistry ,medicine.disease ,Ether-A-Go-Go Potassium Channels ,Potassium channel ,DNA-Binding Proteins ,Potassium Channels, Voltage-Gated ,Trans-Activators ,biology.protein ,E-4031 ,Cardiology and Cardiovascular Medicine ,Anti-Arrhythmia Agents ,Ion Channel Gating - Abstract
Abstract We recently reported that mutations in HERG, a potassium channel gene, cause long QT syndrome. Heterologous expression of HERG in Xenopus oocytes revealed that this channel had biophysical properties nearly identical to a cardiac delayed rectifier K + current, I Kr , but had dissimilar pharmacological properties. Class III antiarrhythmic drugs such as E-4031 and MK-499 are potent and specific blockers of I Kr in cardiac myocytes. Our initial studies indicated that these compounds did not block HERG at a concentration of 1 μmol/L. In the present study, we used standard two-microelectrode voltage-clamp techniques to further characterize the effects of these drugs on HERG channels expressed in oocytes. Consistent with initial findings, 1 μmol/L MK-499 and E-4031 had no effect on HERG when oocytes were voltage clamped at a negative potential and not pulsed during equilibration with the drug. However, MK-499 did block HERG current if oocytes were repetitively pulsed, or clamped at a voltage positive to the threshold potential for channel activation. This finding is in contrast to previous studies that showed significant block of I Kr in isolated myocytes by similar drugs, even in the absence of pulsing. This apparent discrepancy may be due to differences in channel characteristics (HERG versus guinea pig and mouse I Kr ), tissue (oocytes versus myocytes), or specific drugs. Under steady state conditions, block of HERG by MK-499 was half maximal at 123±12 nmol/L at a test potential of −20 mV. MK-499 (150 nmol/L) did not affect the voltage dependence of activation and rectification nor the kinetics of activation and deactivation of HERG. These data indicate that MK-499 preferentially blocks open HERG channels and further support the conclusion that HERG subunits form I Kr channels in cardiac myocytes.
- Published
- 1996
38. Fast inactivation causes rectification of the IKr channel
- Author
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Michael C. Sanguinetti, Mark T. Keating, Anruo Zou, Mark E. Curran, and Peter S. Spector
- Subjects
congenital, hereditary, and neonatal diseases and abnormalities ,DNA, Complementary ,Patch-Clamp Techniques ,Potassium Channels ,Physiology ,Xenopus ,hERG ,Molecular Sequence Data ,Membrane Potentials ,Animals ,Humans ,Magnesium ,Patch clamp ,cardiovascular diseases ,Membrane potential ,biology ,Base Sequence ,Chemistry ,Myocardium ,Depolarization ,Articles ,Hyperpolarization (biology) ,Potassium channel ,Electrophysiology ,Biochemistry ,Ether-A-Go-Go Potassium Channels ,Biophysics ,biology.protein ,Oocytes ,Ion Channel Gating - Abstract
The mechanism of rectification of HERG, the human cardiac delayed rectifier K+ channel, was studied after heterologous expression in Xenopus oocytes. Currents were measured using two-microelectrode and macropatch voltage clamp techniques. The fully activated current-voltage (I-V) relationship for HERG inwardly rectified. Rectification was not altered by exposing the cytoplasmic side of a macropatch to a divalent-free solution, indicating this property was not caused by voltage-dependent block of outward current by Mg2+ or other soluble cytosolic molecules. The instantaneous I-V relationship for HERG was linear after removal of fast inactivation by a brief hyperpolarization. The time constants for the onset of and recovery from inactivation were a bell-shaped function of membrane potential. The time constants of inactivation varied from 1.8 ms at +50 mV to 16 ms at -20 mV; recovery from inactivation varied from 4.7 ms at -120 mV to 15 ms at -50 mV. Truncation of the NH2-terminal region of HERG shifted the voltage dependence of activation and inactivation by +20 to +30 mV. In addition, the rate of deactivation of the truncated channel was much faster than wild-type HERG. The mechanism of HERG rectification is voltage-gated fast inactivation. Inactivation of channels proceeds at a much faster rate than activation, such that no outward current is observed upon depolarization to very high membrane potentials. Fast inactivation of HERG and the resulting rectification are partly responsible for the prolonged plateau phase typical of ventricular action potentials.
- Published
- 1996
39. Effectiveness of sotalol treatment in symptomatic Brugada syndrome
- Author
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Mark T. Keating, Nipavan Chiamvimonvat, Kathryn A. Glatter, Shenghan Chen, Qing Kenneth Wang, and Melvin M. Scheinman
- Subjects
Adult ,Male ,congenital, hereditary, and neonatal diseases and abnormalities ,medicine.medical_specialty ,Heart disease ,medicine.medical_treatment ,Antiarrhythmic agent ,Diagnosis, Differential ,Electrocardiography ,Pharmacotherapy ,Internal medicine ,medicine ,Humans ,Genetic Predisposition to Disease ,cardiovascular diseases ,Family history ,Brugada syndrome ,Genetic testing ,medicine.diagnostic_test ,business.industry ,Sotalol ,Syndrome ,Middle Aged ,medicine.disease ,Pedigree ,Ventricular Fibrillation ,Cardiology ,Female ,Cardiology and Cardiovascular Medicine ,business ,Anti-Arrhythmia Agents ,medicine.drug - Abstract
We describe a 53-year-old man with recurrent syncopal events and a malignant family history who was treated for 13 years with sotalol drug therapy with no further occurrence of Brugada syndrome symptoms. Genetic testing revealed that he carried a Brugada syndrome sodium channel SCN5A mutation (4189delT). This finding suggests that sotalol may be of therapeutic benefit in such patients.
- Published
- 2004
40. ECG T-Wave Patterns in Genetically Distinct Forms of the Hereditary Long QT Syndrome
- Author
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Emanuela H. Locati, Wojciech Zareba, Jean W. MacCluer, Peter J. Schwartz, Michael H. Lehmann, Mark T. Keating, G. Michael Vincent, Jennifer L. Robinson, Arthur J. Moss, W. Jackson Hall, Jeffrey A. Towbin, Jesaia Benhorin, and Katherine W. Timothy
- Subjects
Adult ,Male ,Genotype ,Heart disease ,Genetic Linkage ,Heart block ,Long QT syndrome ,Biology ,QT interval ,Ion Channels ,Electrocardiography ,Genetic linkage ,Physiology (medical) ,medicine ,Humans ,Repolarization ,Genetics ,medicine.diagnostic_test ,Chromosomes, Human, Pair 11 ,Chromosome Mapping ,Heart ,medicine.disease ,Long QT Syndrome ,Phenotype ,Mutation ,Female ,Chromosomes, Human, Pair 3 ,Cardiology and Cardiovascular Medicine ,Chromosomes, Human, Pair 7 - Abstract
Background The long QT syndrome is an inherited disorder with prolonged ventricular repolarization and a propensity to ventricular tachyarrhythmias and sudden arrhythmic death. Recent linkage studies have demonstrated three separate loci for this disorder on chromosomes 3, 7, and 11, and specific mutated genes for long QT syndrome have been identified on two of these chromosomes. We investigated ECG T-wave patterns (phenotypes) in members of families linked to three genetically distinct forms of the long QT syndrome. Methods and Results Five quantitative ECG repolarization parameters, ie, four Bazett-corrected time intervals (QT onset-c , QT peak-c , QT c , and T duration-c , in milliseconds) and the absolute height of the T wave (T amplitude , in millivolts), were measured in 153 members of six families with long QT syndrome linked to markers on chromosomes 3 (n=47), 7 (n=30), and 11 (n=76). Genotypic data were used to define each family member as being affected or unaffected with long QT syndrome. Affected members of all six families had longer QT intervals (QT onset-c , QT peak-c , or QT c ) than unaffected family members ( P onset-c was unusually prolonged in those individuals with mutations involving the cardiac sodium channel gene SCN5A on chromosome 3 (lead II QT onset-c [mean±SD]: chromosome 3, 341±42 ms; chromosome 7, 290±56 ms; chromosome 11, 243±73 ms; P amplitude was generally quite small in the chromosome 7 genotype (lead II T amplitude , mV: chromosome 3, 0.36±0.14; chromosome 7, 0.13±0.07; chromosome 11, 0.37±0.17; P duration was particularly long in the chromosome 11 genotype (lead II T duration-c : chromosome 3, 187±33 ms; chromosome 7, 191±51 ms; chromosome 11, 262±65 ms; P 5 . A considerable variability exists in the quantitative repolarization parameters associated with each genotype, with overlap in the T-wave patterns among the three genotypes. Conclusions Three separate genetic loci for the long QT syndrome including mutations in two cardiac ionic channel genes were associated with different phenotypic T-wave patterns on the ECG. This study provides insight into the influence of genetic factors on ECG manifestations of ventricular repolarization.
- Published
- 1995
41. Genetic Approaches to Cardiovascular Disease
- Author
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Mark T. Keating
- Subjects
medicine.medical_specialty ,Positional cloning ,Long QT syndrome ,Disease ,Sodium Channels ,Electrocardiography ,Physiology (medical) ,Molecular genetics ,Humans ,Medicine ,Genetics ,biology ,business.industry ,Chromosome Mapping ,Aortic Valve Stenosis ,Syndrome ,medicine.disease ,Elastin ,Long QT Syndrome ,Aortic valve stenosis ,Mutation ,biology.protein ,Williams syndrome ,Cardiology and Cardiovascular Medicine ,business ,Supravalvular aortic stenosis - Abstract
Background Although family history can be an important risk factor for cardiovascular disease, relatively little is known about the nature of specific genetic risk factors. One approach to this problem is to identify and characterize genes responsible for inherited disorders in the hope that this information will also provide mechanistic insight into common forms of cardiovascular disease. Methods and Results Over the last decade, it has become possible to identify genes that cause human disease by use of the techniques of molecular genetics, specifically genetic linkage analysis, positional cloning, and mutational analyses. We have used these techniques to study three inherited cardiovascular disorders: supravalvular aortic stenosis, Williams syndrome, and long-QT syndrome. We have discovered that the vascular pathology of supravalvular aortic stenosis and Williams syndrome results from mutations involving the elastin gene on chromosome 7q11.23. These mutations include intragenic deletions, translocations, and complete deletion of the elastin gene, suggesting that a quantitative reduction in elastin during vascular development is pathogenically important. To date, only the elastin gene has proved important for supravalvular aortic stenosis. By contrast, genetic linkage analyses in families with long-QT syndrome indicate that at least four distinct genes can cause this disorder. We have identified three LQT loci: LQT1 on chromosome 11p15.5, LQT2 on 7q35-36, and LQT3 on 3p21-24. Recently, we demonstrated that mutations in a putative cardiac potassium channel gene, HERG , are responsible for the chromosome 7–linked form of long-QT syndrome, whereas mutations in the cardiac sodium channel gene SCN5A cause the chromosome 3–linked form of this disorder. HERG mutations and potassium channel biophysics suggest a dominant-negative molecular mechanism and reduced repolarization currents. By contrast, SCN5A mutations probably cause subtle alterations of cardiac sodium channel function and prolonged depolarizing currents. Conclusions Molecular genetic analyses of long-QT syndrome, supravalvular aortic stenosis, and Williams syndrome have begun to unravel the mechanisms underlying these inherited disorders. Rapid genetic testing for Williams syndrome is now available using a simple cytogenetic test, fluorescence in situ hybridization, but additional work will be required for long-QT syndrome and autosomal-dominant supravalvular aortic stenosis. Improved diagnosis and mechanistic understanding of these disorders should lead to rational treatment and prevention.
- Published
- 1995
42. A mechanistic link between an inherited and an acquird cardiac arrthytmia: HERG encodes the IKr potassium channel
- Author
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Changan Jiang, Michael C. Sanguinetti, Mark E. Curran, and Mark T. Keating
- Subjects
ERG1 Potassium Channel ,congenital, hereditary, and neonatal diseases and abnormalities ,DNA, Complementary ,Patch-Clamp Techniques ,Potassium Channels ,Microinjections ,Xenopus ,Long QT syndrome ,hERG ,030204 cardiovascular system & hematology ,Pharmacology ,General Biochemistry, Genetics and Molecular Biology ,Membrane Potentials ,03 medical and health sciences ,chemistry.chemical_compound ,0302 clinical medicine ,Transcriptional Regulator ERG ,Lanthanum ,medicine ,Animals ,Humans ,cardiovascular diseases ,KvLQT1 ,Cloning, Molecular ,Cation Transport Proteins ,030304 developmental biology ,0303 health sciences ,biology ,Voltage-gated ion channel ,Biochemistry, Genetics and Molecular Biology(all) ,Electric Conductivity ,KCNE2 ,KCNE3 ,Cobalt ,medicine.disease ,Ether-A-Go-Go Potassium Channels ,Recombinant Proteins ,Potassium channel ,DNA-Binding Proteins ,Long QT Syndrome ,chemistry ,Potassium Channels, Voltage-Gated ,Oocytes ,Potassium ,Trans-Activators ,biology.protein ,E-4031 ,Nucleotides, Cyclic ,Ion Channel Gating - Abstract
Mutations in HERG cause an inherited cardiac arrhythmia, long OT syndrome (LOT). To define the function of HERG, we expressed the protein in Xenopus oocytes. The biophysical properties of expressed HERG are nearly identical to the rapidly activating delayed rectifier K+ current (IKr) in cardiac myocytes. HERG current is K+ selective, declines with depolarizations above 0 mV, is activated by extracellular K+, and is blocked by lanthanum. Interestingly, HERG current is not blocked by drugs that specifically block IKr in cardiac myocytes. These data indicate that HERG proteins form IKr channels but that an additional subunit may be required for drug sensitivity. Since block of IKr is a known mechanism for drug-induced cardiac arrhythmias, the finding that HERG encodes IKr channels provides a mechanistic link between certain forms of inherited and acquired LOT.
- Published
- 1995
43. SCN5A mutations associated with an inherited cardiac arrhythmia, long QT syndrome
- Author
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Qing Kenneth Wang, Mark T. Keating, Arthur J. Moss, Zhizhong Li, Jennifer L. Robinson, Jiaxiang Shen, Igor Splawski, Donald L. Atkinson, and Jeffrey A. Towbin
- Subjects
Male ,Genetic Linkage ,Long QT syndrome ,DNA Mutational Analysis ,Molecular Sequence Data ,Nav1.5 ,Sudden death ,General Biochemistry, Genetics and Molecular Biology ,Sodium Channels ,medicine ,Humans ,KvLQT1 ,Amino Acid Sequence ,cardiovascular diseases ,Cloning, Molecular ,Polymorphism, Single-Stranded Conformational ,Sequence Deletion ,Genetics ,biology ,Base Sequence ,Biochemistry, Genetics and Molecular Biology(all) ,Cardiac arrhythmia ,KCNE2 ,medicine.disease ,Romano–Ward syndrome ,Pedigree ,Jervell and Lange-Nielsen syndrome ,Long QT Syndrome ,biology.protein ,cardiovascular system ,Female - Abstract
Long OT syndrome (LOT) is an inherited disorder that causes sudden death from cardiac arrhythmias, specifically torsade de pointes and ventricular fibrillation. We previously mapped three LQT loci: LQT1 on chromosome 11p15.5, LQT2 on 7835-36, and LQT3 on 3p21-24. Here we report genetic linkage between LQT3 and polymorphisms within SCN5A, the cardiac sodium channel gene. Single strand conformation polymorphism and DNA sequence analyses reveal identical intragenic deletions of SCN5A in affected members of two unrelated LOT families. The deleted sequences reside in a region that is important for channel inactivation. These data suggest that mutations in SCN5A cause chromosome 3-linked LOT and indicate a likely cellular mechanism for this disorder.
- Published
- 1995
- Full Text
- View/download PDF
44. A new form of long QT syndrome associated with syndactyly
- Author
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Melinda L. Marks, Sandra L. Whisler, Carol L. Clericuzio, and Mark T. Keating
- Subjects
Male ,medicine.medical_specialty ,Pacemaker, Artificial ,Heart disease ,Heart block ,Long QT syndrome ,Timothy syndrome ,QT interval ,Sudden death ,Cutaneous syndactyly ,Fingers ,Internal medicine ,medicine ,Humans ,Syndactyly ,Ductus Arteriosus, Patent ,business.industry ,Infant ,Toes ,medicine.disease ,Combined Modality Therapy ,Surgery ,Long QT Syndrome ,Child, Preschool ,Cardiology ,business ,Cardiology and Cardiovascular Medicine - Abstract
Objectives . The purpose of this study was to characterize a possible association between long QT syndrome and syndactyly. Background . Long QT syndrome causes syncope and sudden death from ventricular arrhythmias. Syndactyly is a developmental disorder that causes webbing of the hands and feet. Both disorders can be inherited as isolated, autosomal dominant traits, but an association between them has not been established. Methods . We identified three children with long QT syndrome, atrioventricular (AV) block and simple syndactyly. Phenotypic and laboratory data were obtained from families, attending physicians and medical records. Results . All patients had bilateral cutaneous syndactyly and were diagnosed with long QT syndrome within the 1st 2 years of life. Structural heart disease, particularly a patent ductus arteriosus, was present in all three patients. Analysis of electrocardiograms showed marked prolongation of the QT intervals with rate-corrected QT intervals of 633, 628 and 680 ms, respectively. Transient AV block was also noted. Two of the three children died suddenly despite treatment with beta-adrenergic blocking agents and permanent pacing. Conclusions . We postulate that these children have a new form of long QT syndrome associated with syndactyly and a high risk of sudden death. The association of syndactyly with long QT syndrome may provide insight into the mechanisms underlying both disorders. Patients with syndactyly should be evaluated for the presence of long QT syndrome, and if it is found, aggressive treatment may be warranted.
- Published
- 1995
- Full Text
- View/download PDF
45. Two long QT syndrome loci map to chromosomes 3 and 7 with evidence for further heterogeneity
- Author
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Changan Jiang, Donald Atkinson, Jeffrey A. Towbin, Igor Splawski, Michael H. Lehmann, Hua Li, Katherine Timothy, R. Thomas Taggart, Peter J. Schwartz, G. Michael Vincent, Arthur J. Moss, and Mark T. Keating
- Subjects
Genetics ,Jervell and Lange-Nielsen syndrome ,Gene mapping ,Genetic heterogeneity ,Long QT syndrome ,medicine ,Chromosome ,Cardiac arrhythmia ,Locus (genetics) ,Biology ,medicine.disease ,Sudden death - Abstract
Cardiac arrhythmias cause sudden death in 300,000 United States citizens every year. In this study, we describe two new loci for an inherited cardiac arrhythmia, long QT syndrome (LQT). In 1991 we reported linkage of LQT to chromosome 11p15.5. In this study we demonstrate further linkage to D7S483 in nine families with a combined lod score of 19.41 and to D3S1100 in three families with a combined score of 6.72. These findings localize major LQT genes to chromosomes 7q35-36 and 3p21-24, respectively. Linkage to any known locus was excluded in three families indicating that additional heterogeneity exists. Proteins encoded by different LQT genes may interact to modulate cardiac repolarization and arrhythmia risk.
- Published
- 1994
46. Supravalvular aortic stenosis associated with a deletion disrupting the elastin gene
- Author
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Weishan Jin, Amanda K. Ewart, Colleen A. Morris, Mark T. Keating, and Donald L. Atkinson
- Subjects
Male ,Molecular Sequence Data ,Locus (genetics) ,Biology ,Exon ,medicine ,Humans ,Gene ,Genetics ,Base Sequence ,Breakpoint ,Autosomal dominant trait ,General Medicine ,Aortic Stenosis, Subvalvular ,medicine.disease ,Elastin ,Electrophoresis, Gel, Pulsed-Field ,Mutation ,cardiovascular system ,biology.protein ,Female ,Williams syndrome ,Supravalvular aortic stenosis ,Gene Deletion ,Research Article - Abstract
Supravalvular aortic stenosis (SVAS) is an inherited vascular disease that can cause heart failure and death. SVAS can be inherited as an autosomal dominant trait or as part of a developmental disorder, Williams syndrome (WS). In recent studies we presented evidence suggesting that a translocation disrupting the elastin gene caused SVAS in one family while deletions involving the entire elastin locus caused WS. In this study, pulsed-field, PCR, and Southern analyses showed that a 100-kb deletion of the 3' end of the elastin gene cosegregated with the disease in another SVAS family. DNA sequence analysis localized the breakpoint between elastin exons 27 and 28, the same region disrupted by the SVAS-associated translocation. These data indicate that mutations in the elastin gene cause SVAS and suggest that elastin exons 28-36 may encode critical domains for vascular development.
- Published
- 1994
47. Elastin and vascular disease
- Author
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Mark T. Keating
- Subjects
medicine.medical_specialty ,Aorta ,Pathology ,biology ,Vascular disease ,Autosomal dominant trait ,medicine.disease ,Developmental disorder ,Internal medicine ,medicine.artery ,medicine ,biology.protein ,Cardiology ,Williams syndrome ,Allele ,Cardiology and Cardiovascular Medicine ,Elastin ,Supravalvular aortic stenosis - Abstract
Supravalvular aortic stenosis (SVAS) is a vascular disease that primarily affects large arteries, like the aorta and pulmonary arteries. SVAS can be inherited as an isolated, autosomal dominant trait or as part of a complex developmental disorder, Williams syndrome. Molecular genetic studies indicate that mutations affecting part of an elastin allele cause autosomal dominant SVAS while submicroscopic deletions that disrupt the entire elastin gene (and presumably adjacent loci) are responsible for Williams syndrome. These studies suggest that loss of vascular elasticity from any cause may contribute to vascular obstruction.
- Published
- 2011
48. Locus heterogeneity of autosomal dominant long QT syndrome
- Author
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Arthur J. Moss, Vincent Gm, Katherine W. Timothy, Mark Leppert, Mark T. Keating, M Curran, and Donald L. Atkinson
- Subjects
Genetic Markers ,Male ,Genetic Linkage ,Long QT syndrome ,Locus (genetics) ,Biology ,Polymerase Chain Reaction ,Sudden death ,Centimorgan ,Genetic linkage ,Locus heterogeneity ,medicine ,Humans ,Genes, Dominant ,Genetics ,Chromosomes, Human, Pair 11 ,Haplotype ,Chromosome Mapping ,General Medicine ,medicine.disease ,Pedigree ,Romano–Ward syndrome ,Long QT Syndrome ,Genes, ras ,Phenotype ,Haplotypes ,Female ,Lod Score ,Polymorphism, Restriction Fragment Length ,Research Article - Abstract
Autosomal dominant long QT syndrome (LQT) is an inherited disorder that causes syncope and sudden death from cardiac arrhythmias. In genetic linkage studies of seven unrelated families we mapped a gene for LQT to the short arm of chromosome 11 (11p15.5), near the Harvey ras-1 gene (H ras-1). To determine if the same locus was responsible for LQT in additional families, we performed linkage studies with DNA markers from this region (H ras-1 and MUC2). Pairwise linkage analyses resulted in logarithm of odds scores of -2.64 and -5.54 for kindreds 1977 and 1756, respectively. To exclude the possibility that rare recombination events might account for these results, we performed multipoint linkage analyses using additional markers from chromosome 11p15.5 (tyrosine hydroxylase and D11S860). Multipoint analyses excluded approximately 25.5 centiMorgans of chromosome 11p15.5 in K1756 and approximately 13 centiMorgans in K1977. These data demonstrate that the LQT gene in these kindreds is not linked to H ras-1 and suggest that mutations in at least two genes can cause LQT. While the identification of locus heterogeneity of LQT will complicate genetic diagnosis, characterization of additional LQT loci will enhance our understanding of this disorder.
- Published
- 1993
49. A human vascular disorder, supravalvular aortic stenosis, maps to chromosome 7
- Author
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Mark Leppert, Amanda K. Ewart, Colleen A. Morris, Gregory J. Ensing, James Loker, Mark T. Keating, and Cynthia Moore
- Subjects
Genetic Markers ,Male ,medicine.medical_specialty ,Genetic Linkage ,Molecular Sequence Data ,Polymerase Chain Reaction ,Genetic linkage ,Internal medicine ,medicine ,Humans ,Recombination, Genetic ,Genetics ,Chromosome 7 (human) ,Multidisciplinary ,Base Sequence ,biology ,Vascular disease ,Chromosome Mapping ,Aortic Valve Stenosis ,DNA ,medicine.disease ,Elastin ,Pedigree ,Phenotype ,Oligodeoxyribonucleotides ,Aortic valve stenosis ,Vascular Disorder ,cardiovascular system ,biology.protein ,Cardiology ,Female ,Williams syndrome ,Lod Score ,Supravalvular aortic stenosis ,Chromosomes, Human, Pair 7 ,Research Article - Abstract
The pathogenesis of vascular disease is unclear, but genetic factors play an important role. In this study we performed linkage analyses in two families with supravalvular aortic stenosis, an inherited vascular disorder that causes narrowing of major arteries and may lead to cardiac overload and failure. DNA markers on the long arm of chromosome 7 (D7S371, D7S395, D7S448, and ELN) were linked to supravalvular aortic stenosis in both families with a combined logarithm of likelihood for linkage (lod score) of 5.9 at the ELN locus. These findings indicate that a gene for supravalvular aortic stenosis is located in the same chromosomal subunit as elastin, which becomes a candidate for the disease gene.
- Published
- 1993
50. The elastin gene is disrupted by a translocation associated with supravalvular aortic stenosis
- Author
-
Mark T. Keating, Amanda K. Ewart, Donald L. Atkinson, Mark Leppert, Mark E. Curran, and Colleen A. Morris
- Subjects
Male ,Pathology ,medicine.medical_specialty ,Genetic Linkage ,Molecular Sequence Data ,Chromosomal translocation ,Hybrid Cells ,Biology ,medicine.disease_cause ,Translocation, Genetic ,General Biochemistry, Genetics and Molecular Biology ,Exon ,medicine ,Humans ,Amino Acid Sequence ,Gene ,Genetics ,Mutation ,Base Sequence ,Vascular disease ,Chromosome Mapping ,Aortic Valve Stenosis ,Syndrome ,medicine.disease ,Elastin ,Pedigree ,Vascular Disorder ,cardiovascular system ,biology.protein ,Chromosomes, Human, Pair 6 ,Female ,Supravalvular aortic stenosis ,Chromosomes, Human, Pair 7 ,Polymorphism, Restriction Fragment Length - Abstract
To identify genes involved in vascular disease, we investigated patients with supravalvular aortic stenosis (SVAS), an inherited vascular disorder that causes hemodynamically significant narrowing of large elastic arteries. Pulsed-field gel and Southern analyses showed that a translocation near the elastin gene cosegregated with SVAS in one family. DNA sequence analyses demonstrated that the translocation disrupted the elastin gene and localized the breakpoint to exon 28. Taken together with our previous study linking SVAS to the elastin gene in two additional families and existing knowledge of vascular biology, these data suggest that mutations in the elastin gene can cause SVAS.
- Published
- 1993
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