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Remodeling of the cardiac sodium channel, connexin43, and plakoglobin at the intercalated disk in patients with arrhythmogenic cardiomyopathy.
Noorman, M, Hakim, S, Kessler, E, Groeneweg, JA, Cox, MG, Asimaki, A, van Rijen, HV, van Stuijvenberg, L, Chkourko, H, van der Heyden, MA, et al
Heart rhythm. 2013;(3):412-9
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BACKGROUND Arrhythmogenic cardiomyopathy (AC) is closely associated with desmosomal mutations in a majority of patients. Arrhythmogenesis in patients with AC is likely related to remodeling of cardiac gap junctions and increased levels of fibrosis. Recently, using experimental models, we also identified sodium channel dysfunction secondary to desmosomal dysfunction. OBJECTIVE To assess the immunoreactive signal levels of the sodium channel protein NaV1.5, as well as connexin43 (Cx43) and plakoglobin (PKG), in myocardial specimens obtained from patients with AC. METHODS Left and right ventricular free wall postmortem material was obtained from 5 patients with AC and 5 controls matched for age and sex. Right ventricular septal biopsies were taken from another 15 patients with AC. All patients fulfilled the 2010 revised Task Force Criteria for the diagnosis of AC. Immunohistochemical analyses were performed using antibodies against Cx43, PKG, NaV1.5, plakophilin-2, and N-cadherin. RESULTS N-cadherin and desmoplakin immunoreactive signals and distribution were normal in patients with AC compared to controls. Plakophilin-2 signals were unaffected unless a plakophilin-2 mutation predicting haploinsufficiency was present. Distribution was unchanged compared to that in controls. Immunoreactive signal levels of PKG, Cx43, and NaV1.5 were disturbed in 74%, 70%, and 65% of the patients, respectively. CONCLUSIONS A reduced immunoreactive signal of PKG, Cx43, and NaV1.5 at the intercalated disks can be observed in a large majority of the patients. Decreased levels of Nav1.5 might contribute to arrhythmia vulnerability and, in the future, potentially could serve as a new clinically relevant tool for risk assessment strategies.
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Role of cystic fibrosis transmembrane conductance regulator in patients with chronic sinopulmonary disease.
Gonska, T, Choi, P, Stephenson, A, Ellis, L, Martin, S, Solomon, M, Dupuis, A, Dorfman, R, Zielenski, J, Ooi, CY, et al
Chest. 2012;(4):996-1004
Abstract
BACKGROUND Previous studies report a high frequency of mutations in the cystic fibrosis (CF) transmembrane conductance regulator gene (CFTR) in patients with idiopathic bronchiectasis. However, most studies have based their findings on preselected patient groups or have performed limited testing for CF transmembrane conductance regulator (CFTR) dysfunction. The objective of our study was to evaluate the prevalence of CFTR gene mutations and/or CFTR-related ion channel abnormalities among subjects with idiopathic chronic sinopulmonary disease and the prevalence of CF or a CFTR-related disorder in this population. METHODS We evaluated 72 prospectively enrolled patients from 1995 to 2005 at the Hospital for Sick Children and St. Michael’s Hospital with idiopathic chronic sinopulmonary disease for evidence of CFTR-mediated abnormalities. We performed CFTR genotyping and assessed CFTR function using sweat testing and nasal potential difference testing. The results were compared with data from healthy control subjects, CF heterozygotes, and patients with CF. RESULTS The CFTR functional tests in idiopathic sinopulmonary patients showed a continuous spectrum, ranging from normal to values typically seen in individuals with CF. Forty-eight patients (66%) demonstrated CFTR mutations and/or abnormalities of CFTR function. Twenty-two (31%) fulfilled criteria for a diagnosis of CF and 26 (36%) for a CFTR-related disorder with a strong female preponderance. Functional tests, more than genotyping, were instrumental in establishing a CF diagnosis. Clinical features failed to distinguish subjects with CF from those with CFTR-related or idiopathic disease. CONCLUSIONS The high prevalence of CF and CFTR dysfunction among patients with idiopathic chronic sinopulmonary disease underscores the need for extensive diagnostic evaluation for CF.
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Transient outward current (I(to)) gain-of-function mutations in the KCND3-encoded Kv4.3 potassium channel and Brugada syndrome.
Giudicessi, JR, Ye, D, Tester, DJ, Crotti, L, Mugione, A, Nesterenko, VV, Albertson, RM, Antzelevitch, C, Schwartz, PJ, Ackerman, MJ
Heart rhythm. 2011;(7):1024-32
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BACKGROUND Brugada syndrome (BrS) is a sudden death-predisposing genetic condition characterized electrocardiographically by ST segment elevation in the leads V(1)-V(3). Given the prominent role of the transient outward current (I(to)) in BrS pathogenesis, we hypothesized that rare gain-of-function mutations in KCND3 may serve as a pathogenic substrate for BrS. METHODS Comprehensive mutational analysis of KCND3-encoded Kv4.3 (I(to)) was conducted using polymerase chain reaction, denaturing high performance liquid chromatography, and direct sequencing of DNA derived from 86 unrelated BrS1-8 genotype-negative BrS patients. DNA from 780 healthy individuals was examined to assess allelic frequency for nonsynonymous variants. Putative BrS-associated Kv4.3 mutations were engineered and coexpressed with wild-type KChIP2 in HEK293 cells. Wild-type and mutant I(to) ion currents were recorded using whole-cell patch clamp. RESULTS Two BrS1-8 genotype-negative cases possessed novel Kv4.3 missense mutations. Both Kv4.3-L450F and Kv4.3-G600R were absent in 1,560 reference alleles and involved residues highly conserved across species. Both Kv4.3-L450F and Kv4.3-G600R demonstrated a gain-of-function phenotype, increasing peak I(to) current density by 146.2% (n = 15, P <.05) and 50.4% (n = 15, P <.05), respectively. Simulations using a Luo-Rudy II action potential (AP) model demonstrated the stable loss of the AP dome as a result of the increased I(to) maximal conductance associated with the heterozygous expression of either L450F or G600R. CONCLUSIONS These findings provide the first molecular and functional evidence implicating novel KCND3 gain-of-function mutations in the pathogenesis and phenotypic expression of BrS, with the potential for a lethal arrhythmia being precipitated by a genetically enhanced I(to) current gradient within the right ventricle where KCND3 expression is the highest.
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T-wave morphology abnormalities in benign, potent, and arrhythmogenic I(kr) inhibition.
Couderc, JP, Xia, X, Peterson, DR, McNitt, S, Zhao, H, Polonsky, S, Moss, AJ, Zareba, W
Heart rhythm. 2011;(7):1036-43
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BACKGROUND There is a consensus on the limited value of the QTc interval prolongation as a surrogate marker of drug cardiotoxicity and as a risk stratifier in inherited long QT syndrome (LQTS) patients. OBJECTIVE We investigated the interest of repolarization morphology in the acquired and the inherited LQTS. METHODS We analyzed 2 retrospective electrocardiographic (ECG) datasets from healthy on/off moxifloxacin and from genotyped KCNH2 patients. We measured QT, RR, and T-peak to T-end intervals, early repolarization duration (ERD) and late repolarization duration, T-roundness, T-amplitude, left (αL) and right slopes of T-waves. We designed multivariate logistic models to predict the presence of the KCNH2 mutation or moxifloxacin while adjusting for the level of QTc prolongation and the level of heart rate in LQT2 patients. Independent learning and validation sets were used. A list of 4,874 ECGs from 411 healthy individuals, 293 from 143 LQT2 carriers and 150 noncarrier family members were analyzed. RESULTS In the moxifloxacin model, ERD was associated with the presence of the drug (odds ratio = 1.15 per ms increase, confidence interval 1.04 to 1.26, P = .0001) after adjustment for QTc. The model for the LQT2 revealed that left slope was associated with the presence of the KCNH2 mutation (odds ratio = 0.38 per 1.5 μV/ms decrease, confidence interval 0.23 to 0.64, P = .0002). Only T-roundness complemented QTc in the model investigating cardiac events in LQT2. CONCLUSIONS These observations demonstrate that the phenotypic expression of KCNH2 mutations and the effect of IKr-inhibitory drug on the surface electrocardiogram are specific. Future research should investigate whether this phenomenon is linked to different level/form of loss functions of Ikr channels, and whether they could result in different arrhythmogenic mechanisms.
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Genome-wide association study of smoking behaviours in patients with COPD.
Siedlinski, M, Cho, MH, Bakke, P, Gulsvik, A, Lomas, DA, Anderson, W, Kong, X, Rennard, SI, Beaty, TH, Hokanson, JE, et al
Thorax. 2011;(10):894-902
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Background Cigarette smoking is a major risk factor for chronic obstructive pulmonary disease (COPD) and COPD severity. Previous genome-wide association studies (GWAS) have identified numerous single nucleotide polymorphisms (SNPs) associated with the number of cigarettes smoked per day (CPD) and a dopamine beta-hydroxylase (DBH) locus associated with smoking cessation in multiple populations. Objective To identify SNPs associated with lifetime average and current CPD, age at smoking initiation, and smoking cessation in patients with COPD. Methods GWAS were conducted in four independent cohorts encompassing 3441 ever-smoking patients with COPD (Global Initiative for Obstructive Lung Disease stage II or higher). Untyped SNPs were imputed using the HapMap (phase II) panel. Results from all cohorts were meta-analysed. Results Several SNPs near the HLA region on chromosome 6p21 and in an intergenic region on chromosome 2q21 showed associations with age at smoking initiation, both with the lowest p=2×10(-7). No SNPs were associated with lifetime average CPD, current CPD or smoking cessation with p<10(-6). Nominally significant associations with candidate SNPs within cholinergic receptors, nicotinic, alpha 3/5 (CHRNA3/CHRNA5; eg, p=0.00011 for SNP rs1051730) and cytochrome P450, family 2, subfamily A, polypeptide 6 (CYP2A6; eg, p=2.78×10(-5) for a non-synonymous SNP rs1801272) regions were observed for lifetime average CPD, however only CYP2A6 showed evidence of significant association with current CPD. A candidate SNP (rs3025343) in DBH was significantly (p=0.015) associated with smoking cessation. Conclusion The authors identified two candidate regions associated with age at smoking initiation in patients with COPD. Associations of CHRNA3/CHRNA5 and CYP2A6 loci with CPD and DBH with smoking cessation are also likely of importance in the smoking behaviours of patients with COPD.
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Effect of pravastatin therapy on coronary events in carriers of the KIF6 719Arg allele from the cholesterol and recurrent events trial.
Shiffman, D, Sabatine, MS, Louie, JZ, Kirchgessner, TG, Iakoubova, OA, Campos, H, Devlin, JJ, Sacks, FM
The American journal of cardiology. 2010;(9):1300-5
Abstract
A previous genetic analysis of the Cholesterol and Recurrent Events (CARE) trial found that carriers of the 719Arg allele of the kinesin family member 6 gene (KIF6) (rs20455), but not noncarriers, received significant event reduction from pravastatin therapy. However, that previous analysis of CARE included only Caucasian patients and was limited to the myocardial infarction components of the primary end point. Therefore, the aim of this study was to investigate whether pravastatin therapy reduced primary end point events in KIF6 719Arg carriers and noncarriers, separately, in the combined ethnic groups of CARE. The effect of pravastatin therapy on primary end point events (fatal coronary event or nonfatal myocardial infarction) was investigated in Cox regression models that adjusted for population structure using either self-reported ethnicity or the principal components of genetic heterogeneity. After adjustment for age, gender, and self-reported ethnicity, pravastatin therapy reduced events in carriers of KIF6 719Arg (hazard ratio [HR] 0.63, 95% confidence interval [CI] 0.49 to 0.83) but not in noncarriers (HR 1.01, 95% CI 0.69 to 1.45) (p for interaction = 0.049). After adjustment for age, gender, traditional risk factors, and principal components, pravastatin therapy reduced events in carriers of 719Arg (HR 0.64, 95% CI 0.49 to 0.85) but not in noncarriers (HR 0.90, 95% CI 0.62 to 1.32) (p for interaction = 0.14). In conclusion, in an analysis that included CARE patients of all ethnic groups, pravastatin therapy significantly and substantially reduced primary end point events in carriers of the KIF6 719Arg allele but not in noncarriers.
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A nanodosimetric model of radiation-induced clustered DNA damage yields.
Garty, G, Schulte, R, Shchemelinin, S, Leloup, C, Assaf, G, Breskin, A, Chechik, R, Bashkirov, V, Milligan, J, Grosswendt, B
Physics in medicine and biology. 2010;(3):761-81
Abstract
We present a nanodosimetric model for predicting the yield of double strand breaks (DSBs) and non-DSB clustered damages induced in irradiated DNA. The model uses experimental ionization cluster size distributions measured in a gas model by an ion counting nanodosimeter or, alternatively, distributions simulated by a Monte Carlo track structure code developed to simulate the nanodosimeter. The model is based on a straightforward combinatorial approach translating ionizations, as measured or simulated in a sensitive gas volume, to lesions in a DNA segment of one-two helical turns considered equivalent to the sensitive volume of the nanodosimeter. The two model parameters, corresponding to the probability that a single ion detected by the nanodosimeter corresponds to a single strand break or a single lesion (strand break or base damage) in the equivalent DNA segment, were tuned by fitting the model-predicted yields to previously measured double-strand break and double-strand lesion yields in plasmid DNA irradiated with protons and helium nuclei. Model predictions were also compared to both yield data simulated by the PARTRAC code for protons of a wide range of different energies and experimental DSB and non-DSB clustered DNA damage yield data from the literature. The applicability and limitations of this model in predicting the LET dependence of clustered DNA damage yields are discussed.
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[Separation of proteins on microchip electrophoresis and its comparison with DNA migration].
Liu, C, Xu, X, Zhang, J, Chen, J
Se pu = Chinese journal of chromatography. 2010;(3):296-300
Abstract
The efficient separation of six standard proteins on a home-made poly (dimethylsiloxane) microchip with an auto-deducting background diode laser induced fluorescence detector was accomplished within 6.4 min under the sieving matrix of 10 g/L hydroxyethyl cellulose (HEC), 1 g/L sodium dodecyl sulphonate (SDS), 40 mmol/L phosphate buffer at pH 7.0. The experimental results showed that the reproducibility of protein separation was satisfactory and the relative standard deviations (RSDs) of protein migration time were less than 10%. The migration times of the proteins are analyzed by a quantitative mathematical model of deoxyribonucleic acid (DNA) proposed by ourselves previously. The results showed that the migration character of SDS-protein complexes was similar with DNA. However, the linear relationships between the mobilities of SDS-protein complexes and their relative molecular mass as well as electric field strength became worse, which indicated the mathematical model for DNA separation should be revised before it is used for protein separation.
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The fat-mass and obesity-associated (FTO) gene, physical activity, and risk of incident cardiovascular events in white women.
Ahmad, T, Chasman, DI, Mora, S, Paré, G, Cook, NR, Buring, JE, Ridker, PM, Lee, IM
American heart journal. 2010;(6):1163-9
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BACKGROUND Variation in the Fat-Mass and Obesity-Associated (FTO) gene has been associated with obesity, diabetes, and hypertension. However, its association with cardiovascular disease (CVD) in healthy populations and any interaction with physical activity remain unclear. METHODS The FTO rs8050136 allele was determined in a prospective cohort study of 21,674 apparently healthy White US women in the Women's Genome Health Study. RESULTS During a mean follow-up of 12.7±2.0 years, 664 incident CVD events occurred. The risk allele (A) was associated with higher prevalence of hypertension, diabetes, and metabolic syndrome (all P<.05). In a multivariate model, there was significant association of the risk allele with CVD (hazard ratio [HR] per allele copy 1.14, 95% CI 1.01-1.28) that was no longer significant after additional adjustment for body mass index (BMI) (HR 1.10, 95% CI 0.97-1.23). There was statistical evidence of an interaction between FTO and physical activity (P=.048). We found a significant association of FTO with CVD only among less-active (≤8.8 metabolic equivalent-h/wk) women (HR 1.19, 95% CI 1.02-1.38) in multivariate analyses that included BMI. More-active women did not have this increased risk (HR 0.96, 95% CI 0.79-1.16]). In a model that adjusted for BMI, less-active/high-risk (A/A) women were at 54% increased risk of developing CVD (HR 1.54, 95% CI 1.13-2.11), compared to more-active/low-risk (C/C) women. CONCLUSIONS Carriers of the FTO risk allele have an increased risk of CVD mediated by BMI. There appears to be an interaction with physical activity, such that this risk increase is only in less-active women.
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COMT genotype influences the effect of alcohol on blood pressure: results from the COMBINE study.
Stewart, SH, Oroszi, G, Randall, PK, Anton, RF
American journal of hypertension. 2009;(1):87-91
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BACKGROUND Heavy drinking can cause chronic hypertension, possibly due to effects on the autonomic nervous system. Catechol- O-methyltransferase (COMT) inactivates catecholamines, and a G to A substitution in codon 108 in the soluble COMT mRNA (or codon 158 in the membrane-bound form) substitutes methionine for valine and alters enzyme activity. METHODS We evaluated the association of COMT genotype at this locus with blood pressure (BP) in 839 alcohol-dependent individuals before and during participation in an alcoholism treatment trial. Hierarchical linear models were used to account for within-subject correlation on repeated BP measurements, and findings were adjusted for age, gender, ethnicity, alcohol use, body mass index, current smoking, hypertension history, and study site. RESULTS Relative to those with the val-val genotype, those with the met-met genotype had higher adjusted systolic (+4.9 mm Hg, P < 0.01) and diastolic (+3.2 mm Hg, P < 0.01) BP at baseline. Those with the val-met genotype did not significantly differ from the val-val genotype. Changes in BP between baseline and 4 weeks of alcohol treatment also differed by genotype. Relative to the val-val genotype, the met-met genotype had a greater reduction in adjusted systolic pressure (-3.9 mm Hg, P < 0.01) and diastolic pressure (-2.8 mm Hg, P < 0.01). Corresponding relative reductions for the val-met genotype were -2.2 mm Hg systolic (P = 0.070) and -1.5 mm Hg diastolic (P < 0.05). CONCLUSION Findings suggest that alcohol-induced BP elevation may be related to the effects of catecholamines and their genetically determined inactivation.