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1.
J Biol Chem ; : 101228, 2021 Sep 30.
Artigo em Inglês | MEDLINE | ID: mdl-34600884

RESUMO

Pathogenic variants of the ACTA2 gene, which encodes smooth muscle (SM) α-actin, predispose to heritable thoracic aortic disease. The ACTA2 variant p.Arg149Cys (R149C) is the most common alteration; however only 60% of carriers have a dissection or undergo repair of an aneurysm by 70 years of age. A mouse model of ACTA2 p.Arg149Cys was generated using CRISPR/Cas9 technology to determine the etiology of reduced penetrance. Acta2R149C/+ mice had significantly decreased aortic contraction compared to wild type (WT) mice but did not form aortic aneurysms or dissections when followed to 24 months, even when hypertension was induced. In vitro motility assays found decreased interaction of mutant SM α-actin filaments with smooth muscle myosin. Polymerization studies using Total Internal Reflection Fluorescence (TIRF) microscopy showed enhanced nucleation of mutant SM α-actin by formin, which correlated with disorganized and reduced SM α-actin filaments in Acta2R149C/+ smooth muscle cells (SMCs). However, the most prominent molecular defect was the increased retention of mutant SM α-actin in the chaperonin-containing t-complex polypeptide (CCT) folding complex, which was associated with reduced levels of mutant compared to WT SM α-actin in Acta2R149C/+ SMCs. These data indicate that Acta2R149C/+ mice do not develop thoracic aortic disease despite decreased contraction of aortic segments and disrupted SM α-actin filament formation and function in Acta2R149C/+ SMCs. Enhanced binding of mutant SM α-actin to CCT decreases the mutant actin versus WT monomer levels in Acta2R149C/+ SMCs, thus minimizing the effect of the mutation on SMC function and potentially preventing aortic disease in the Acta2R149C/+ mice.

2.
Medicine (Baltimore) ; 100(30): e26431, 2021 Jul 30.
Artigo em Inglês | MEDLINE | ID: mdl-34397684

RESUMO

BACKGROUND: Sodium glucose cotransporter 2 (SGLT2) inhibitors and glucagon-like peptide 1 receptor agonists (GLP-1 RAs) have been demonstrated to be able to improve the cardiovascular and renal prognosis in patients with type 2 diabetes (T2D). However, the relative efficacy of various SGLT2 inhibitors and GLP-1 RAs on cardiorenal outcomes is unestablished. METHODS: We searched PubMed and Embase for relevant cardiovascular or renal outcome trials (CVOTs). Endpoints of interest were major adverse cardiovascular events (MACE), stroke, myocardial infarction (MI), cardiovascular death (CVD), all-cause death (ACD), kidney function progression (KFP), and hospitalization for heart failure (HHF). Bayesian network meta-analysis was conducted to produce pooled hazard ratio (HR) and 95% confidence interval (CI). We calculated the probability values of surface under the cumulative ranking curve to rank active and placebo interventions. RESULTS: Fourteen COVTs were included in analysis. Sotagliflozin (HR 0.76, 95% CI 0.61-0.94), subcutaneous semaglutide, and albiglutide lowered MACE versus lixisenatide among others. Sotagliflozin (HR 0.59, 95% CI 0.40-0.89), canagliflozin, and empagliflozin lowered HHF versus subcutaneous semaglutide among others. Dapagliflozin and empagliflozin lowered KFP versus exenatide among others. Empagliflozin and oral semaglutide lowered CVD versus dapagliflozin among others. Sotagliflozin (HR 0.65, 95% CI 0.47-0.91) and albiglutide lowered MI versus ertugliflozin among others. Sotagliflozin (HR 0.56, 95% CI 0.37-0.85) and subcutaneous semaglutide lowered stroke versus empagliflozin among others. Oral semaglutide and empagliflozin lowered ACD versus subcutaneous semaglutide among others. The maximum surface under the cumulative ranking curve values followed sotagliflozin, subcutaneous semaglutide, and albiglutide in lowering MACE; sotagliflozin, canagliflozin, and empagliflozin in lowering HHF; dapagliflozin and empagliflozin in lowering KFP; empagliflozin and oral semaglutide in lowering CVD; sotagliflozin and albiglutide in lowering MI; sotagliflozin and subcutaneous semaglutide in lowering stroke; and oral semaglutide and empagliflozin in lowering ACD. CONCLUSIONS: This updated network meta-analysis reproduced the findings in the first network meta-analysis, and moreover revealed that sotagliflozin was one of the most effective drugs as for lowering MI, stroke, MACE, and HHF, whereas ertugliflozin was not. These findings will provide the according evidence regarding the usage of specific SGLT2 inhibitors and GLP-1 RAs in T2D patients for prevention of specific cardiorenal endpoints.


Assuntos
Diabetes Mellitus Tipo 2/tratamento farmacológico , Receptor do Peptídeo Semelhante ao Glucagon 1/antagonistas & inibidores , Coração/efeitos dos fármacos , Rim/efeitos dos fármacos , Inibidores do Transportador 2 de Sódio-Glicose/efeitos adversos , Diabetes Mellitus Tipo 2/fisiopatologia , Receptor do Peptídeo Semelhante ao Glucagon 1/uso terapêutico , Coração/fisiopatologia , Humanos , Rim/fisiopatologia , Metanálise em Rede , Inibidores do Transportador 2 de Sódio-Glicose/uso terapêutico , Resultado do Tratamento
3.
Front Pharmacol ; 12: 724405, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-34381370

RESUMO

The association between sodium-glucose cotransporter 2 inhibitors (SGLT2is) and various cardiovascular and respiratory diseases is unestablished. This meta-analysis aimed to explore whether use of SGLT2is is significantly associated with the occurrences of 80 types of cardiovascular diseases and 55 types of respiratory diseases. Large randomized trials of SGLT2is were included in analysis. Meta-analysis was conducted to synthesize risk ratio (RR) and 95% confidence interval (CI). Nine large trials were included in analysis. Compared to placebo, SGLT2is were associated with the reduced risks of 9 types of cardiovascular diseases (e.g., atrial fibrillation [RR 0.78, 95% CI 0.67-0.91], bradycardia [RR 0.60, 95% CI 0.40-0.89], and hypertensive emergency [RR 0.29, 95% CI 0.12-0.72]) and 11 types of respiratory diseases (e.g., chronic obstructive pulmonary disease [RR 0.77, 95% CI 0.61-0.97], asthma [RR 0.57, 95% CI 0.35-0.95], and sleep apnoea syndrome [RR 0.36, 95% CI 0.15-0.87]). The results of random-effects meta-analysis were similar with those of fixed-effects meta-analysis. No heterogeneity or only little heterogeneity was found in most meta-analyses. No publication bias was observed in most of the meta-analyses conducted in this study. SGLT2is were not significantly associated with the other 115 cardiovascular and respiratory diseases. SGLT2is are associated with the reduced risks of 9 types of cardiovascular diseases (e.g., atrial fibrillation, bradycardia, and hypertensive emergency) and 11 types of respiratory diseases (e.g., chronic obstructive pulmonary disease, asthma, and sleep apnoea syndrome). This proposes the potential of SGLT2is to be used for prevention of these cardiovascular and respiratory diseases.

5.
Endocr J ; 68(6): 739-742, 2021 Jun 28.
Artigo em Inglês | MEDLINE | ID: mdl-34024887

RESUMO

The PIONEER and SUSTAIN serial trials are designed to assess the efficacy outcomes with semaglutide in patients with type 2 diabetes, but are not powered to assess various safety outcomes. We sought to assess the risk of semaglutide in leading to various serious adverse events (SAEs) in patients with type 2 diabetes. Studies eligible for inclusion were the PIONEER and SUSTAIN trials of semaglutide. We conducted meta-analysis to generate pooled risk ratios (RRs) and 95% confidence intervals (CIs). Meta-analysis was performed using both random-effects and fixed-effects model to evaluate the robustness of pooled results. We implemented subgroup analysis according to drug dosages and routes of administration and type of comparators. Twenty-one trials were included. Semaglutide versus control significantly reduced total SAEs (RR 0.92, 95% CI 0.87-0.97; I2 = 0) and atrial fibrillation (RR 0.69, 95% CI 0.50-0.95; I2 = 0), but significantly increased deep vein thrombosis (RR 3.66, 95% CI 1.09-12.25; I2 = 0) and diarrhoea (RR 2.66, 95% CI 1.19-5.95; I2 = 0). Semaglutide had no significant effects on 248 other kinds of SAEs. No statistically significant subgroup effects were observed. Semaglutide has a good safety profile in general and reduces atrial fibrillation by 31%, but increases diarrhoea by 166% and deep vein thrombosis by 266%. These findings may guide that semaglutide should be preferred or avoided in T2D patients with specific susceptibility factors.

6.
J Cell Mol Med ; 24(21): 12599-12607, 2020 11.
Artigo em Inglês | MEDLINE | ID: mdl-32940422

RESUMO

MiR-148 is a negative regulator of autophagy 16-like 1 (ATG16L1), a gene implicated in the pathogenesis of ventilator-associated pneumonia (VAP). Therefore, the role of miR-148 polymorphism in the pathogenesis of VAP was studied here. The expression of miR-148, ATG16L1, Beclin-I, LC3-II, TNF-α and IL-6 in serum and peripheral blood mononuclear cells (PBMCs) of VAP patients was detected to study their relationship in the pathogenesis of VAP. Chronic obstructive pulmonary disease patients carrying the AA/AG genotypes of miR-148 rs4719839 single nucleotide polymorphism (SNP) were more prone to VAP due to the higher expression of miR-148, TNF-α and IL-6 along with suppressed expression of ATG16L1, Beclin-I and LC3-II in their serum and PBMCs. Transfection of miR-148 mimics to primary PBMCs genotyped as GG and AA decreased the expression of ATG16L1, Beclin-I and LC3-II. Finally, cells carrying the AA genotype of rs4719839 SNP were more sensitive to the role of LPS stimulation in suppressing ATG16L1, Beclin-I and LC3-II expression while activating TNF-α and IL-6 expression. Our work presented detailed evidence, suggesting that the rs4719839 polymorphism can affect the risk of VAP.


Assuntos
Proteínas Relacionadas à Autofagia/genética , Autofagia/genética , Regulação da Expressão Gênica , Predisposição Genética para Doença , MicroRNAs/genética , Pneumonia Associada à Ventilação Mecânica/genética , Polimorfismo de Nucleotídeo Único/genética , Idoso , Alelos , Estudos de Casos e Controles , Regulação para Baixo/genética , Feminino , Humanos , Incidência , Interleucina-6/sangue , Leucócitos Mononucleares/metabolismo , Lipopolissacarídeos/farmacologia , Masculino , MicroRNAs/metabolismo , Pessoa de Meia-Idade , Pneumonia Associada à Ventilação Mecânica/complicações , Pneumonia Associada à Ventilação Mecânica/epidemiologia , Doença Pulmonar Obstrutiva Crônica/complicações , Doença Pulmonar Obstrutiva Crônica/genética , Fatores de Risco , Fator de Necrose Tumoral alfa/sangue
7.
Eur J Hum Genet ; 27(7): 1054-1060, 2019 07.
Artigo em Inglês | MEDLINE | ID: mdl-30809044

RESUMO

SMAD4 pathogenic variants cause juvenile polyposis (JPS) and hereditary hemorrhagic telangiectasia (HHT), and 40% of affected individuals also have thoracic aortic disease. At the same time, SMAD4 pathogenic variants have not been reported in thoracic aortic disease families without JPS-HHT. A SMAD4 heterozygous variant, c.290G>T, p.(Arg97Leu), not present in population databases and predicted to be damaging to protein function, was identified in a family with thoracic aortic disease and no evidence of HHT or JPS. Cellular studies revealed that the SMAD4 p.(Arg97Leu) alteration increased SMAD4 ubiquitination and 26S proteasome-mediated protein degradation. Smooth muscle cells (SMCs) infected with lentivirus expressing the SMAD4 p.(Arg97Leu) variant demonstrated reduced contractile protein gene expression when compared to that of wild-type SMAD4. In addition, two rare variants were identified in individuals with early age of onset of thoracic aortic dissection. These results suggest that SMAD4 rare missense variants can lead to thoracic aortic disease in individuals who do not have JPS or HHT.


Assuntos
Aneurisma Dissecante , Aneurisma da Aorta Torácica , Família , Mutação de Sentido Incorreto , Proteína Smad4 , Substituição de Aminoácidos , Aneurisma Dissecante/genética , Aneurisma Dissecante/metabolismo , Aneurisma da Aorta Torácica/genética , Aneurisma da Aorta Torácica/metabolismo , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Complexo de Endopeptidases do Proteassoma/genética , Complexo de Endopeptidases do Proteassoma/metabolismo , Proteólise , Proteína Smad4/genética , Proteína Smad4/metabolismo , Ubiquitinação/genética
8.
Zhongguo Dang Dai Er Ke Za Zhi ; 21(1): 82-88, 2019 Jan.
Artigo em Chinês | MEDLINE | ID: mdl-30675869

RESUMO

OBJECTIVE: To systematically review the effect of probiotic supplementation during pregnancy and infancy in preventing atopic dermatitis in children. METHODS: RevMan5.3 was used to perform a Meta analysis of randomized controlled trials on the effect of probiotic supplementation during pregnancy and infancy in preventing atopic dermatitis in children published between January 2008 and May 2018 across the world. A subgroup analysis was conducted according to the type of probiotics for intervention, follow-up time, time of probiotic supplementation, and study areas. RESULTS: A total of 22 articles were selected, with 3 280 cases in the intervention group and 3 281 cases in the control group. The results of pooled effect size showed that probiotic supplementation during pregnancy and/or infancy significantly reduced the incidence rate of atopic dermatitis (RR=0.81, 95%CI: 0.70-0.93, P<0.05). According to the subgroup analysis, the intervention with Lactobacillus and Bifidobacterium had a significant effect (RR=0.68, 95%CI: 0.52-0.90, P<0.05); probiotic supplementation during both pregnancy and infancy also had a significant effect (RR=0.77, 95%CI: 0.66-0.90, P<0.05); probiotic supplementation during pregnancy and/or infancy had a better effect in preventing atopic dermatitis in children aged ≤2 years than in those aged >2 years (RR=0.74, 95%CI: 0.61-0.90, P<0.05); probiotic supplementation had a significant effect in Australia (RR=0.83, 95%CI: 0.73-0.96, P<0.05) and Europe/the United States (RR=0.74, 95%CI: 0.61-0.91, P<0.05). Heterogeneity was mainly due to follow-up time (I2=62.7%) and time of probiotic supplementation (I2=53.5%). CONCLUSIONS: Probiotic supplementation during pregnancy and infancy helps to prevent atopic dermatitis in children, and mixed Lactobacillus-Bifidobacterium intervention has a better effect.


Assuntos
Dermatite Atópica , Probióticos , Bifidobacterium , Pré-Escolar , Feminino , Humanos , Lactente , Lactobacillus , Gravidez
9.
Am J Hum Genet ; 103(1): 138-143, 2018 07 05.
Artigo em Inglês | MEDLINE | ID: mdl-29961567

RESUMO

Thoracic aortic aneurysms leading to acute aortic dissections are a preventable cause of premature deaths if individuals at risk can be identified. Individuals with early-onset aortic dissections without a family history or syndromic features have an increased burden of rare genetic variants of unknown significance (VUSs) in genes with pathogenic variants for heritable thoracic aortic disease (HTAD). We assessed the role of VUSs in the development of disease using both in vitro enzymatic assays and mouse models. VUSs in LOX and MYLK identified in individuals with acute aortic dissections were assayed to determine whether they disrupted enzymatic activity. A subset of VUSs reduced enzymatic activity compared to the wild-type proteins but less than pathogenic variants. Additionally, a Myh11 variant, p.Arg247Cys, which does not cause aortic disease in either humans or mice, was crossed with the Acta2-/- mouse, which has aortic enlargement with age while Acta2+/- mice do not. Acta2+/-Myh11R247C/R247C mice have aortic dilation by 3 months of age without medial degeneration, indicating that two variants not known to cause disease do lead to aortic enlargement in combination. Furthermore, the addition of Myh11R247C/R247C to the Acta2-/- mouse model accelerates aortic enlargement and increases medial degeneration. Therefore, our results emphasize the need for a classification system for variants in Mendelian genes that goes beyond the 5-tier system of pathogenic, likely pathogenic, VUS, likely benign, and benign, and includes a designation for low-penetrant "risk variants" that trigger disease either in combination with other risk factors or in a stochastic manner.


Assuntos
Aorta Torácica/patologia , Aneurisma da Aorta Torácica/genética , Doenças da Aorta/genética , Variação Genética/genética , Actinas/genética , Aneurisma Dissecante/genética , Animais , Modelos Animais de Doenças , Humanos , Camundongos
10.
Am J Hum Genet ; 100(1): 21-30, 2017 Jan 05.
Artigo em Inglês | MEDLINE | ID: mdl-27939641

RESUMO

Fibromuscular dysplasia (FMD) is a heterogeneous group of non-atherosclerotic and non-inflammatory arterial diseases that primarily involves the renal and cerebrovascular arteries. Grange syndrome is an autosomal-recessive condition characterized by severe and early-onset vascular disease similar to FMD and variable penetrance of brachydactyly, syndactyly, bone fragility, and learning disabilities. Exome-sequencing analysis of DNA from three affected siblings with Grange syndrome identified compound heterozygous nonsense variants in YY1AP1, and homozygous nonsense or frameshift YY1AP1 variants were subsequently identified in additional unrelated probands with Grange syndrome. YY1AP1 encodes yin yang 1 (YY1)-associated protein 1 and is an activator of the YY1 transcription factor. We determined that YY1AP1 localizes to the nucleus and is a component of the INO80 chromatin remodeling complex, which is responsible for transcriptional regulation, DNA repair, and replication. Molecular studies revealed that loss of YY1AP1 in vascular smooth muscle cells leads to cell cycle arrest with decreased proliferation and increased levels of the cell cycle regulator p21/WAF/CDKN1A and disrupts TGF-ß-driven differentiation of smooth muscle cells. Identification of YY1AP1 mutations as a cause of FMD indicates that this condition can result from underlying genetic variants that significantly alter the phenotype of vascular smooth muscle cells.


Assuntos
Displasia Fibromuscular/genética , Músculo Liso Vascular/metabolismo , Músculo Liso Vascular/patologia , Mutação , Proteínas Nucleares/genética , Fatores de Transcrição/genética , Adolescente , Adulto , Osso e Ossos/patologia , Braquidactilia/genética , Pontos de Checagem do Ciclo Celular/genética , Proteínas de Ciclo Celular , Exoma/genética , Feminino , Genes Recessivos , Heterozigoto , Homozigoto , Humanos , Deficiências da Aprendizagem/genética , Masculino , Pessoa de Meia-Idade , Linhagem , Sindactilia/genética , Síndrome
11.
J Clin Invest ; 126(3): 948-61, 2016 Mar 01.
Artigo em Inglês | MEDLINE | ID: mdl-26854927

RESUMO

The ascending thoracic aorta is designed to withstand biomechanical forces from pulsatile blood. Thoracic aortic aneurysms and acute aortic dissections (TAADs) occur as a result of genetically triggered defects in aortic structure and a dysfunctional response to these forces. Here, we describe mutations in the forkhead transcription factor FOXE3 that predispose mutation-bearing individuals to TAAD. We performed exome sequencing of a large family with multiple members with TAADs and identified a rare variant in FOXE3 with an altered amino acid in the DNA-binding domain (p.Asp153His) that segregated with disease in this family. Additional pathogenic FOXE3 variants were identified in unrelated TAAD families. In mice, Foxe3 deficiency reduced smooth muscle cell (SMC) density and impaired SMC differentiation in the ascending aorta. Foxe3 expression was induced in aortic SMCs after transverse aortic constriction, and Foxe3 deficiency increased SMC apoptosis and ascending aortic rupture with increased aortic pressure. These phenotypes were rescued by inhibiting p53 activity, either by administration of a p53 inhibitor (pifithrin-α), or by crossing Foxe3-/- mice with p53-/- mice. Our data demonstrate that FOXE3 mutations lead to a reduced number of aortic SMCs during development and increased SMC apoptosis in the ascending aorta in response to increased biomechanical forces, thus defining an additional molecular pathway that leads to familial thoracic aortic disease.


Assuntos
Aneurisma Dissecante/genética , Aneurisma da Aorta Torácica/genética , Fatores de Transcrição Forkhead/genética , Adulto , Aneurisma Dissecante/metabolismo , Aneurisma Dissecante/patologia , Animais , Aorta/metabolismo , Aorta/patologia , Aneurisma da Aorta Torácica/metabolismo , Aneurisma da Aorta Torácica/patologia , Apoptose , Células Cultivadas , Inibidor de Quinase Dependente de Ciclina p21/metabolismo , Feminino , Expressão Gênica , Estudos de Associação Genética , Predisposição Genética para Doença , Humanos , Masculino , Camundongos Endogâmicos C57BL , Camundongos Knockout , Pessoa de Meia-Idade , Músculo Liso Vascular/patologia , Mutação de Sentido Incorreto , Miócitos de Músculo Liso/fisiologia , Linhagem , Proteína Supressora de Tumor p53/genética , Remodelação Vascular , Peixe-Zebra
12.
Cell Stem Cell ; 13(5): 577-89, 2013 Nov 07.
Artigo em Inglês | MEDLINE | ID: mdl-24209761

RESUMO

Abnormal stem cell function makes a known contribution to many malignant tumors, but the role of stem cells in benign tumors is not well understood. Here, we show that ossifying fibroma (OF) contains a stem cell population that resembles mesenchymal stem cells (OFMSCs) and is capable of generating OF-like tumor xenografts. Mechanistically, OFMSCs show enhanced TGF-ß signaling that induces aberrant proliferation and deficient osteogenesis via Notch and BMP signaling pathways, respectively. The elevated TGF-ß activity is tightly regulated by JHDM1D-mediated epigenetic regulation of thrombospondin-1 (TSP1), forming a JHDM1D/TSP1/TGF-ß/SMAD3 autocrine loop. Inhibition of TGF-ß signaling in OFMSCs can rescue their abnormal osteogenic differentiation and elevated proliferation rate. Furthermore, chronic activation of TGF-ß can convert normal MSCs into OF-like MSCs via establishment of this JHDM1D/TSP1/TGF-ß/SMAD3 autocrine loop. These results reveal that epigenetic regulation of TGF-ß signaling in MSCs governs the benign tumor phenotype in OF and highlight TGF-ß signaling as a candidate therapeutic target.


Assuntos
Fatores de Transcrição de Zíper de Leucina e Hélice-Alça-Hélix Básicos/genética , Epigênese Genética/genética , Fibroma Ossificante/metabolismo , Fibroma Ossificante/patologia , Células-Tronco Neoplásicas , Proteína Smad3/genética , Fator de Crescimento Transformador beta/genética , Animais , Humanos , Camundongos , Células-Tronco Neoplásicas/citologia , Células-Tronco Neoplásicas/metabolismo
13.
Adv Pharmacol Sci ; 2013: 192408, 2013.
Artigo em Inglês | MEDLINE | ID: mdl-23401679

RESUMO

In the present study, we investigated the feasibility of the vaginal administration of drospirenone silicone IVR. The in vitro release characteristics of matrix-type and reservoir-type IVR were compared under sink conditions in 21 days. At the same time, API excipients compatibility and preformulation study was performed by HPLC, IR, and DSC methods. Biocompatibility of reservoir system was evaluated by tolerability on tissue level in rats. It was found that, under strong light exposure, high temperature, and high humidity conditions, drospirenone and excipients had no significant interactions. The daily release of reservoir-type IVR was about 0.5 mg/d sustaining 21 days, which significantly decreased the burst effect compared with the matrix system. When drospirenone was modified by the PVPk30 in the reservoir system formulation, the daily release rate increased to 1.0 mg/d sustaining 21 days. The cumulative release of reservoir-type IVR was fitted to zero release equation. In addition, biocompatibility of drospirenone IVR system in this dosage is safe. It is feasibility feasibile to further developed for safe, convenient, and effective contraceptive drug delivery with reduced dosing interval.

14.
Mol Microbiol ; 55(1): 206-20, 2005 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-15612929

RESUMO

Social (S)-motility in Myxococcus xanthus is a flagellum-independent gliding motility system that allows bacteria to move in groups on solid surfaces. S-motility has been shown to require type IV pili (TFP), exopolysaccharide (EPS; a component of fibrils) and lipopolysaccharide (LPS). Previously, information concerning EPS biogenesis in M. xanthus was lacking. In this study, we screened 5000 randomly mutagenized colonies for defects in S-motility and EPS and identified two genetic regions essential for EPS biogenesis: the EPS synthesis (eps) region and the EPS-associated (eas) region. Mutants with insertions in the eps and eas regions were defective in S-motility and fruiting body formation. These mutants failed to bind the dye calcofluor white, indicating that they lacked EPS; however, they retained normal TFP and LPS. Analysis of the eps locus showed several open reading frames (ORFs) that encode homologues to glycosyltransferases, glucanases and EPS transporters as well as regulatory proteins; the eas locus contains two ORFs: one exhibits homology to hypothetical proteins with a conserved domain of unknown function and the other displays no apparent homology to other proteins in the database. Further genetic mutagenesis analysis indicates that the whole eps region is involved in the biosynthesis of fibrils and fibril EPS. The operon at the proximal end of the eps region was analysed by generating in-frame deletion mutations. These mutants showed varying degrees of defects in the bacterium's ability to produce EPS or perform EPS-related functions, confirming the involvement of these genes in M. xanthus EPS biogenesis.


Assuntos
Myxococcus xanthus/genética , Polissacarídeos Bacterianos/genética , DNA Bacteriano , Fímbrias Bacterianas/metabolismo , Regulação Bacteriana da Expressão Gênica , Genes Bacterianos , Lipopolissacarídeos/biossíntese , Mutação , Myxococcus xanthus/fisiologia , Fases de Leitura Aberta , Óperon , Polissacarídeos Bacterianos/biossíntese , Polissacarídeos Bacterianos/fisiologia , Sequências Reguladoras de Ácido Nucleico , Análise de Sequência de DNA
15.
Microbiology (Reading) ; 150(Pt 12): 4085-93, 2004 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-15583161

RESUMO

Myxococcus xanthus is a gliding bacterium that possesses two motility systems, the adventurous (A-motility) and social (S-motility) systems. A-motility is used for individual cell gliding, while S-motility is used for gliding in multicellular groups. Video microscopy studies showed that nla24 cells are non-motile on agar surfaces, suggesting that the nla24 gene product is absolutely required for both A-motility and S-motility under these assay conditions. S-motility requires functional type IV pili, wild-type LPS O-antigen, and an extracellular matrix of exopolysaccharide (EPS) and protein called fibrils. The results of expression studies and tethering assays indicate that the nla24 mutant has functional type IV pili. The nla24 mutant also produces wild-type LPS. However, several lines of evidence suggest that the nla24 mutant is defective for production of the EPS portion of the fibril matrix. The nla24 mutant is also defective for transcription of two genes (aglU and cglB) known to be required for A-motility, which is consistent with the idea that nla24 cells are defective for A-motility. Based on these findings, it is proposed that the putative transcriptional activator Nla24 regulates a subset of genes that are important for A-motility and S-motility in M. xanthus.


Assuntos
Proteínas de Bactérias/genética , Regulação Bacteriana da Expressão Gênica , Mutação , Myxococcus xanthus/fisiologia , Proteínas de Bactérias/metabolismo , Microscopia de Vídeo , Movimento , Myxococcus xanthus/genética
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