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Hernandez BJ, Skiba NP, Plössl K, Strain M, Liu Y, Grigsby D, Kelly U, Cady MA, Manocha V, Maminishkis A, Watkins T, Miller SS, Ashley‐Koch A, Stamer WD, Weber BHF, Bowes Rickman C, Klingeborn M. Polarized Desmosome and Hemidesmosome Shedding via Small Extracellular Vesicles is an Early Indicator of Outer Blood-Retina Barrier Dysfunction. J Extracell Biol 2023; 2:e116. [PMID: 38108061 PMCID: PMC10720597 DOI: 10.1002/jex2.116] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/18/2023] [Revised: 08/30/2023] [Accepted: 09/11/2023] [Indexed: 12/19/2023]
Abstract
The retinal pigmented epithelium (RPE) constitutes the outer blood-retinal barrier, enables photoreceptor function of the eye, and is constantly exposed to oxidative stress. As such, dysfunction of the RPE underlies pathology leading to development of age-related macular degeneration (AMD), the leading cause of vision loss among the elderly in industrialized nations. A major responsibility of the RPE is to process photoreceptor outer segments, which relies on the proper functioning of its endocytic pathways and endosomal trafficking. Exosomes and other extracellular vesicles (EVs) from RPE are an essential part of these pathways and may be early indicators of cellular stress. To test the role of small EVs (sEVs) including exosomes, that may underlie the early stages of AMD, we used a polarized primary RPE cell culture model under chronic subtoxic oxidative stress. Unbiased proteomic analyses of highly purified basolateral sEVs from oxidatively stressed RPE cultures revealed changes in proteins involved in epithelial barrier integrity. There were also significant changes in proteins accumulating in the basal-side sub-RPE extracellular matrix during oxidative stress, that could be prevented with an inhibitor of sEV release. Thus, chronic subtoxic oxidative stress in primary RPE cultures induces changes in sEV content, including basal-side specific desmosome and hemidesmosome shedding via sEVs. These findings provide novel biomarkers of early cellular dysfunction and opportunity for therapeutic intervention in age-related retinal diseases (e.g., AMD).
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Affiliation(s)
- Belinda J. Hernandez
- Department of Ophthalmology, Duke Eye CenterDuke UniversityDurhamNorth CarolinaUSA
| | - Nikolai P. Skiba
- Department of Ophthalmology, Duke Eye CenterDuke UniversityDurhamNorth CarolinaUSA
| | - Karolina Plössl
- Institute of Human GeneticsUniversity of RegensburgRegensburgGermany
| | - Madison Strain
- Duke Molecular Physiology Institute, Department of MedicineDuke UniversityDurhamNorth CarolinaUSA
| | - Yutao Liu
- Department of Cellular Biology and AnatomyAugusta UniversityAugustaGeorgiaUSA
| | - Daniel Grigsby
- Department of Ophthalmology, Duke Eye CenterDuke UniversityDurhamNorth CarolinaUSA
| | - Una Kelly
- Department of Ophthalmology, Duke Eye CenterDuke UniversityDurhamNorth CarolinaUSA
| | - Martha A. Cady
- Department of Ophthalmology, Duke Eye CenterDuke UniversityDurhamNorth CarolinaUSA
| | - Vikram Manocha
- Department of Ophthalmology, Duke Eye CenterDuke UniversityDurhamNorth CarolinaUSA
| | - Arvydas Maminishkis
- Ophthalmic Genetics and Visual Function Branch, Section on Epithelial and Retinal Physiology and DiseaseNational Eye Institute, National Institutes of HealthBethesdaMarylandUSA
| | - TeddiJo Watkins
- Department of Ophthalmology, Duke Eye CenterDuke UniversityDurhamNorth CarolinaUSA
- Office of Animal Welfare Assurance, Duke Animal Care and Use ProgramDuke UniversityDurhamNorth CarolinaUSA
| | - Sheldon S. Miller
- Ophthalmic Genetics and Visual Function Branch, Section on Epithelial and Retinal Physiology and DiseaseNational Eye Institute, National Institutes of HealthBethesdaMarylandUSA
| | - Allison Ashley‐Koch
- Duke Molecular Physiology Institute, Department of MedicineDuke UniversityDurhamNorth CarolinaUSA
| | - W. Daniel Stamer
- Department of Ophthalmology, Duke Eye CenterDuke UniversityDurhamNorth CarolinaUSA
- Department of Biomedical EngineeringDuke UniversityDurhamNorth CarolinaUSA
| | - Bernhard H. F. Weber
- Institute of Human GeneticsUniversity of RegensburgRegensburgGermany
- Institute of Clinical Human GeneticsUniversity Hospital RegensburgRegensburgGermany
| | - Catherine Bowes Rickman
- Department of Ophthalmology, Duke Eye CenterDuke UniversityDurhamNorth CarolinaUSA
- Department of Cell BiologyDuke UniversityDurhamNorth CarolinaUSA
| | - Mikael Klingeborn
- Department of Ophthalmology, Duke Eye CenterDuke UniversityDurhamNorth CarolinaUSA
- McLaughlin Research InstituteGreat FallsMontanaUSA
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Grigsby D, Klingeborn M, Kelly U, Chew LA, Asokan A, Devlin G, Smith S, Keyes L, Timmers A, Scaria A, Bowes Rickman C. AAV Gene Augmentation of Truncated Complement Factor H Differentially Rescues Ocular Complement Dysregulation in a Mouse Model. Invest Ophthalmol Vis Sci 2023; 64:25. [PMID: 37471073 PMCID: PMC10365136 DOI: 10.1167/iovs.64.10.25] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/21/2023] Open
Abstract
Purpose Complement dysregulation in the eye has been implicated in the pathogenesis of age-related macular degeneration (AMD), and genetic variants of complement factor H (CFH) are strongly associated with AMD risk. We therefore aimed to untangle the role of CFH and its splice variant, factor H-like 1 (FHL-1), in ocular complement regulation derived from local versus circulating sources. We assessed the therapeutic efficacy of adeno-associated viruses (AAVs) expressing human FHL-1 and a truncated version of CFH (tCFH), which retains the functional N- and C-terminal ends of the CFH protein, in restoring the alternative complement pathway in Cfh-/- mouse eyes and plasma. Methods Using Cfh-/- mice as a model of complement dysregulation, AAV vectors expressing tCFH or FHL-1 were injected subretinally or via tail vein, and the efficacy of the constructs was evaluated. Results Following subretinal injections, tCFH expression rescued factor B (FB) retention in the eye, but FHL-1 expression did not. By contrast, both constructs restored FB detection in plasma following tail vein injections. Both tCFH and FHL-1 proteins accumulated in the posterior eyecup from the circulation following liver transduction; however, neither was able to significantly regulate local ocular complement. Conclusions Our findings demonstrate that the C-terminus of human CFH is necessary for complement regulation in the murine eye. Furthermore, exogenous CFH must be synthesized locally to maximize complement regulation in the retina. These findings establish a critical foundation for development of CFH augmentation-based gene therapies for the eye.
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Affiliation(s)
- Daniel Grigsby
- Department of Ophthalmology, Duke University School of Medicine, Durham, North Carolina, United States
| | - Mikael Klingeborn
- Department of Ophthalmology, Duke University School of Medicine, Durham, North Carolina, United States
- McLaughlin Research Institute, Great Falls, Montana, United States
| | - Una Kelly
- Department of Ophthalmology, Duke University School of Medicine, Durham, North Carolina, United States
| | - Lindsey A Chew
- Department of Ophthalmology, Duke University School of Medicine, Durham, North Carolina, United States
- Department of Cell Biology, Duke University School of Medicine, Durham, North Carolina, United States
| | - Aravind Asokan
- Departments of Surgery, Molecular Genetics and Microbiology, and Biomedical Engineering, Duke University School of Medicine, Durham, North Carolina, United States
| | - Garth Devlin
- Departments of Surgery, Molecular Genetics and Microbiology, and Biomedical Engineering, Duke University School of Medicine, Durham, North Carolina, United States
| | - Sharon Smith
- Applied Genetic Technologies Corporation, Alachua, Florida, United States
| | - Lisa Keyes
- Pfizer, Morrisville, North Carolina, United States
| | - Adrian Timmers
- Editas Medicine, Cambridge, Massachusetts, United States
| | - Abraham Scaria
- Applied Genetic Technologies Corporation, Alachua, Florida, United States
| | - Catherine Bowes Rickman
- Department of Ophthalmology, Duke University School of Medicine, Durham, North Carolina, United States
- Department of Cell Biology, Duke University School of Medicine, Durham, North Carolina, United States
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Hernandez BJ, Skiba NP, Plößl K, Strain M, Grigsby D, Kelly U, Cady MA, Manocha V, Maminishkis A, Watkins T, Miller SS, Ashley-Koch A, Stamer WD, Weber BHF, Rickman CB, Klingeborn M. Polarized Desmosome and Hemidesmosome Shedding via Exosomes is an Early Indicator of Outer Blood-Retina Barrier Dysfunction. bioRxiv 2023:2023.06.12.544677. [PMID: 37398366 PMCID: PMC10312606 DOI: 10.1101/2023.06.12.544677] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/04/2023]
Abstract
The retinal pigmented epithelium (RPE) constitutes the outer blood-retinal barrier, enables photoreceptor function of the eye, and is constantly exposed to oxidative stress. As such, dysfunction of the RPE underlies pathology leading to development of age-related macular degeneration (AMD), the leading cause of vision loss among the elderly in industrialized nations. A major responsibility of the RPE is to process photoreceptor outer segments, which relies on the proper functioning of its endocytic pathways and endosomal trafficking. Exosomes and other extracellular vesicles from RPE are an essential part of these pathways and may be early indicators of cellular stress. To test the role of exosomes that may underlie the early stages of AMD, we used a polarized primary RPE cell culture model under chronic subtoxic oxidative stress. Unbiased proteomic analyses of highly purified basolateral exosomes from oxidatively stressed RPE cultures revealed changes in proteins involved in epithelial barrier integrity. There were also significant changes in proteins accumulating in the basal-side sub-RPE extracellular matrix during oxidative stress, that could be prevented with an inhibitor of exosome release. Thus, chronic subtoxic oxidative stress in primary RPE cultures induces changes in exosome content, including basal-side specific desmosome and hemidesmosome shedding via exosomes. These findings provide novel biomarkers of early cellular dysfunction and opportunity for therapeutic intervention in age-related retinal diseases, (e.g., AMD) and broadly from blood-CNS barriers in other neurodegenerative diseases.
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Kelly UL, Grigsby D, Cady MA, Landowski M, Skiba NP, Liu J, Remaley AT, Klingeborn M, Bowes Rickman C. High-density lipoproteins are a potential therapeutic target for age-related macular degeneration. J Biol Chem 2020; 295:13601-13616. [PMID: 32737203 DOI: 10.1074/jbc.ra119.012305] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2019] [Revised: 07/22/2020] [Indexed: 02/02/2023] Open
Abstract
Strong evidence suggests that dysregulated lipid metabolism involving dysfunction of the retinal pigmented epithelium (RPE) underlies the pathogenesis of age-related macular degeneration (AMD), the leading cause of irreversible blindness in the elderly. A hallmark of AMD is the overproduction of lipid- and protein-rich extracellular deposits that accumulate in the extracellular matrix (Bruch's membrane (BrM)) adjacent to the RPE. We analyzed apolipoprotein A-1 (ApoA-1)-containing lipoproteins isolated from BrM of elderly human donor eyes and found a unique proteome, distinct from high-density lipoprotein (HDL) isolated from donor plasma of the same individuals. The most striking difference is higher concentrations of ApoB and ApoE, which bind to glycosaminoglycans. We hypothesize that this interaction promotes lipoprotein deposition onto BrM glycosaminoglycans, initiating downstream effects that contribute to RPE dysfunction/death. We tested this hypothesis using two potential therapeutic strategies to alter the lipoprotein/protein profile of these extracellular deposits. First, we used short heparan sulfate oligosaccharides to remove lipoproteins already deposited in both the extracellular matrix of RPE cells and aged donor BrM tissue. Second, an ApoA-1 mimetic, 5A peptide, was demonstrated to modulate the composition and concentration of apolipoproteins secreted from primary porcine RPE cells. Significantly, in a mouse model of AMD, this 5A peptide altered the proteomic profile of circulating HDL and ameliorated some of the potentially harmful changes to the protein composition resulting from the high-fat, high-cholesterol diet in this model. Together, these results suggest that targeting HDL interactions with BrM represents a new strategy to slow AMD progression in humans.
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Affiliation(s)
- Una L Kelly
- Department of Ophthalmology, Duke University Medical Center, Durham, North Carolina, USA
| | - Daniel Grigsby
- Department of Ophthalmology, Duke University Medical Center, Durham, North Carolina, USA
| | - Martha A Cady
- Department of Ophthalmology, Duke University Medical Center, Durham, North Carolina, USA
| | - Michael Landowski
- Department of Ophthalmology, Duke University Medical Center, Durham, North Carolina, USA
| | - Nikolai P Skiba
- Department of Ophthalmology, Duke University Medical Center, Durham, North Carolina, USA
| | - Jian Liu
- Division of Chemical Biology and Medicinal Chemistry, Eshelman School of Pharmacy, University of North Carolina, Chapel Hill, North Carolina, USA
| | - Alan T Remaley
- Lipoprotein Metabolism Section, Pulmonary and Vascular Medicine Branch, NHLBI, National Institutes of Health, Bethesda, Maryland, USA
| | - Mikael Klingeborn
- Department of Ophthalmology, Duke University Medical Center, Durham, North Carolina, USA.
| | - Catherine Bowes Rickman
- Department of Ophthalmology, Duke University Medical Center, Durham, North Carolina, USA; Department of Cell Biology, Duke University Medical Center, Durham, North Carolina, USA.
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Du J, Price MP, Taugher RJ, Grigsby D, Ash JJ, Stark AC, Hossain Saad MZ, Singh K, Mandal J, Wemmie JA, Welsh MJ. Transient acidosis while retrieving a fear-related memory enhances its lability. eLife 2017; 6:e22564. [PMID: 28650315 PMCID: PMC5484615 DOI: 10.7554/elife.22564] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2016] [Accepted: 06/13/2017] [Indexed: 02/02/2023] Open
Abstract
Attenuating the strength of fearful memories could benefit people disabled by memories of past trauma. Pavlovian conditioning experiments indicate that a retrieval cue can return a conditioned aversive memory to a labile state. However, means to enhance retrieval and render a memory more labile are unknown. We hypothesized that augmenting synaptic signaling during retrieval would increase memory lability. To enhance synaptic transmission, mice inhaled CO2 to induce an acidosis and activate acid sensing ion channels. Transient acidification increased the retrieval-induced lability of an aversive memory. The labile memory could then be weakened by an extinction protocol or strengthened by reconditioning. Coupling CO2 inhalation to retrieval increased activation of amygdala neurons bearing the memory trace and increased the synaptic exchange from Ca2+-impermeable to Ca2+-permeable AMPA receptors. The results suggest that transient acidosis during retrieval renders the memory of an aversive event more labile and suggest a strategy to modify debilitating memories.
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Affiliation(s)
- Jianyang Du
- Departments of Internal Medicine, Roy J and Lucille A Carver College of Medicine, University of Iowa, Iowa City, United States
- Department of Biological Sciences, University of Toledo, Toledo, United States
| | - Margaret P Price
- Departments of Internal Medicine, Roy J and Lucille A Carver College of Medicine, University of Iowa, Iowa City, United States
| | - Rebecca J Taugher
- Department of Psychiatry, Roy J and Lucille A Carver College of Medicine, University of Iowa, Iowa City, United States
| | - Daniel Grigsby
- Departments of Internal Medicine, Roy J and Lucille A Carver College of Medicine, University of Iowa, Iowa City, United States
| | - Jamison J Ash
- Departments of Internal Medicine, Roy J and Lucille A Carver College of Medicine, University of Iowa, Iowa City, United States
| | - Austin C Stark
- Departments of Internal Medicine, Roy J and Lucille A Carver College of Medicine, University of Iowa, Iowa City, United States
| | | | - Kritika Singh
- Department of Biological Sciences, University of Toledo, Toledo, United States
| | - Juthika Mandal
- Department of Biological Sciences, University of Toledo, Toledo, United States
| | - John A Wemmie
- Department of Psychiatry, Roy J and Lucille A Carver College of Medicine, University of Iowa, Iowa City, United States
- Department of Molecular Physiology and Biophysics, Roy J and Lucille A Carver College of Medicine, University of Iowa, Iowa City, United States
- Department of Neurosurgery, Roy J and Lucille A Carver College of Medicine, University of Iowa, Iowa City, United States
| | - Michael J Welsh
- Departments of Internal Medicine, Roy J and Lucille A Carver College of Medicine, University of Iowa, Iowa City, United States
- Department of Molecular Physiology and Biophysics, Roy J and Lucille A Carver College of Medicine, University of Iowa, Iowa City, United States
- Department of Neurosurgery, Roy J and Lucille A Carver College of Medicine, University of Iowa, Iowa City, United States
- Howard Hughes Medical Institute, Roy J and Lucille A Carver College of Medicine, University of Iowa, Iowa City, United States
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Noginov M, Novak J, Grigsby D, Zhu G, Bahoura M. Optimization of the transport mean free path and the absorption length in random lasers with non-resonant feedback. Opt Express 2005; 13:8829-8836. [PMID: 19498915 DOI: 10.1364/opex.13.008829] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
We have studied numerically the optimal range of the transport mean free path lt and the absorption length (at the pumping wavelength) la, which minimize the threshold and maximize the slope efficiency of a random laser with non-resonant feedback. The results of the calculations are in a good agreement with the experimental results obtained in the GaAs/Al2O3 random laser.
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Hoe NP, Vuopio-Varkila J, Vaara M, Grigsby D, De Lorenzo D, Fu YX, Dou SJ, Pan X, Nakashima K, Musser JM. Distribution of streptococcal inhibitor of complement variants in pharyngitis and invasive isolates in an epidemic of serotype M1 group A Streptococcus infection. J Infect Dis 2001; 183:633-9. [PMID: 11170990 DOI: 10.1086/318543] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2000] [Revised: 11/07/2000] [Indexed: 11/03/2022] Open
Abstract
Streptococcal inhibitor of complement (Sic) is a highly polymorphic extracellular protein made predominantly by serotype M1 group A Streptococcus (GAS). New variants of the Sic protein frequently appear in M1 epidemics as a result of positive natural selection. To gain further understanding of the molecular basis of M1 epidemics, the sic gene was sequenced from 471 pharyngitis and 127 pyogenic and blood isolates recovered from 598 patients living in metropolitan Helsinki, Finland, during a 37-month population-based surveillance study. Most M1 GAS subclones recovered from pyogenic infections and blood were abundantly represented in the pool of subclones causing pharyngitis. Alleles shared among the pharyngitis, pyogenic, and blood samples were identified in throat isolates a mean of 9.8 months before their recovery from pyogenic infections and blood, which indicates that selection of most sic variants occurs on mucosal surfaces. In contrast, no variation was identified in the emm and covR/covS genes.
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Affiliation(s)
- N P Hoe
- Laboratory of Human Bacterial Pathogenesis, Rocky Mountain Laboratories, National Institute of Allergy and Infectious Diseases, National Institutes of Health, 903 S. 4th St., Hamilton, Montana 59840, USA
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Elam C, Grigsby D, Nora LM, Wilson E. University of Kentucky College of Medicine. Acad Med 2000; 75:S130-S132. [PMID: 10995657 DOI: 10.1097/00001888-200009001-00036] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
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Hoe NP, Nakashima K, Lukomski S, Grigsby D, Liu M, Kordari P, Dou SJ, Pan X, Vuopio-Varkila J, Salmelinna S, McGeer A, Low DE, Schwartz B, Schuchat A, Naidich S, De Lorenzo D, Fu YX, Musser JM. Rapid selection of complement-inhibiting protein variants in group A Streptococcus epidemic waves. Nat Med 1999; 5:924-9. [PMID: 10426317 DOI: 10.1038/11369] [Citation(s) in RCA: 86] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
Serotype M1 group A Streptococcus strains cause epidemic waves of human infections long thought to be mono- or pauciclonal. The gene encoding an extracellular group A Streptococcus protein (streptococcal inhibitor of complement) that inhibits human complement was sequenced in 1,132 M1 strains recovered from population-based surveillance of infections in Canada, Finland and the United States. Epidemic waves are composed of strains expressing a remarkably heterogeneous array of variants of streptococcal inhibitor of complement that arise very rapidly by natural selection on mucosal surfaces. Thus, our results enhance the understanding of pathogen population dynamics in epidemic waves and infectious disease reemergence.
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Affiliation(s)
- N P Hoe
- Institute for the Study of Human Bacterial Pathogenesis, Department of Pathology, Baylor College of Medicine, Houston, Texas 77030, USA
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Hoe N, Nakashima K, Grigsby D, Pan X, Dou SJ, Naidich S, Garcia M, Kahn E, Bergmire-Sweat D, Musser JM. Rapid molecular genetic subtyping of serotype M1 group A Streptococcus strains. Emerg Infect Dis 1999; 5:254-63. [PMID: 10221878 PMCID: PMC2640708 DOI: 10.3201/eid0502.990210] [Citation(s) in RCA: 85] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
Serotype M1 group A Streptococcus, the most common cause of invasive disease in many case series, generally have resisted extensive molecular subtyping by standard techniques (e.g., multilocus enzyme electrophoresis, pulsed-field gel electrophoresis). We used automated sequencing of the sic gene encoding streptococcal inhibitor of complement and of a region of the chromosome with direct repeat sequences to unambiguously differentiate 30 M1 isolates recovered from 28 patients in Texas with invasive disease episodes temporally clustered and thought to represent an outbreak. Sequencing of the emm gene was less useful for M1 strain differentiation, and restriction fragment length polymorphism analysis with IS1548 or IS1562 as Southern hybridization probes did not provide epidemiologically useful subtyping information. Sequence polymorphism in the direct repeat region of the chromosome and IS1548 profiling data support the hypothesis that M1 organisms have two main evolutionary lineages marked by the presence or absence of the speA2 allele encoding streptococcal pyrogenic exotoxin A2.
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Affiliation(s)
- N Hoe
- Baylor College of Medicine, Houston, Texas 77030, USA
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Stockbauer KE, Grigsby D, Pan X, Fu YX, Mejia LM, Cravioto A, Musser JM. Hypervariability generated by natural selection in an extracellular complement-inhibiting protein of serotype M1 strains of group A Streptococcus. Proc Natl Acad Sci U S A 1998; 95:3128-33. [PMID: 9501227 PMCID: PMC19706 DOI: 10.1073/pnas.95.6.3128] [Citation(s) in RCA: 64] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
In many countries, M1 strains of the human pathogenic bacterium group A Streptococcus are the most common serotype recovered from patients with invasive disease episodes. Strains of this serotype express an extracellular protein that inhibits complement [streptococcal inhibitor of complement (Sic)] and is therefore believed to be a virulence factor. Comparative sequence analysis of the 915-bp sic gene in 165 M1 organisms recovered from diverse localities and infection types identified 62 alleles. Inasmuch as multilocus enzyme electrophoresis and pulsed-field gel electrophoresis previously showed that most M1 organisms represent a distinct streptococcal clone, the extent of sic gene polymorphism was unexpected. The level of polymorphism greatly exceeds that recorded for all other genes examined in serotype M1 strains. All insertions and deletions are in frame, and virtually all nucleotide substitutions alter the amino acid sequence of the Sic protein. These molecular features indicate that structural change in Sic is mediated by natural selection. Study of 70 strains recovered from two temporally distinct epidemics of streptococcal infections in the former East Germany found little sharing of Sic variants among strains recovered in the different time periods. Taken together, the data indicate that sic is a uniquely variable gene and provide insight into a potential molecular mechanism contributing to fluctuations in streptococcal disease frequency and severity.
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Affiliation(s)
- K E Stockbauer
- Institute for the Study of Human Bacterial Pathogenesis, Department of Pathology, Baylor College of Medicine, One Baylor Plaza, Houston, TX 77030, USA
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