Background: The proliferation of genetic profiling has revealed many associations between genetic variations and disease. However, large-scale phenotyping efforts in largely healthy populations, coupled with DNA sequencing, suggest variants currently annotated as pathogenic are more common in healthy populations than previously thought. In addition, novel and rare variants are frequently observed in genes associated with disease both in healthy individuals and those under suspicion of disease. This raises the question of whether these variants can be useful predictors of disease. To answer this question, we assessed the degree to which the presence of a variant in the cardiac potassium channel gene KCNH2 was diagnostically predictive for the autosomal dominant long QT syndrome. Methods: We estimated the probability of a long QT diagnosis given the presence of each KCNH2 variant using Bayesian methods that incorporated variant features such as changes in variant function, protein structure, and in silico predictions. We call this estimate the posttest probability of disease. Our method was applied to over 4000 individuals heterozygous for 871 missense or in-frame insertion/deletion variants in KCNH2 and validated against a separate international cohort of 933 individuals heterozygous for 266 missense or in-frame insertion/deletion variants. Results: Our method was well-calibrated for the observed fraction of heterozygotes diagnosed with long QT syndrome. Heuristically, we found that the innate diagnostic information one learns about a variant from 3-dimensional variant location, in vitro functional data, and in silico predictors is equivalent to the diagnostic information one learns about that same variant by clinically phenotyping 10 heterozygotes. Most importantly, these data can be obtained in the absence of any clinical observations. Conclusions: We show how variant-specific features can inform a prior probability of disease for rare variants even in the absence of clinically phenotyped heterozygotes.
We investigated the effects of a newly synthesized compound, 1-(5-chloronaphthalene-1-sulfonyl)-1H-hexahydro-1,4-diazepine (ML-9), a myosin light chain kinase (MLCK) inhibitor of superprecipitation of actomyosin, isometric tension development, and phosphorylation of the 20,000-Da myosin light chain (LC20) in vascular smooth muscle. Superprecipitation of actomyosin from bovine aorta was inhibited by the addition of ML-9 in a dose-dependent manner. In chemically skinned smooth muscles of the rabbit mesenteric artery, ML-9 inhibited the Ca2+-independent contraction provoked by application of trypsin-treated MLCK. In the intact rabbit mesenteric artery, increases in LC20 phosphorylation reached a maximal value of 0.49 mol of Pi/mol of LC20 within 10 sec from a resting value of 0.15 mol of Pi/mol of LC20 and then declined to near the basal level during the maintained isometric force developed in response to 50 mM KCl. Preincubation with 10-30 microM ML-9 for 30 min significantly inhibited both the maximal rate and extent of KCl-induced contraction and the phosphorylation of LC20, in a dose-dependent manner. There was a linear relationship between the initial rate of tension development and the extent of LC20 phosphorylation at 10 sec after stimulation. ML-9 nonspecifically antagonized the contraction induced by various contractile agonists, such as CaCl2, norepinephrine, serotonin, histamine, and angiotensin II. ML-9 dose dependently produced a shift to the right and down, in the dose-response curves, to all the agonists tested. These results suggest that ML-9 inhibits the actin-myosin interaction through the modulation of LC20 phosphorylation via the inhibition of MLCK activity. Thus, ML-9 may be a useful compound for investigating the physiologic role of myosin light chain phosphorylation by MLCK in living cells and tissues as well as in vitro.
Background: Congenital long QT syndrome (LQTS) is a monogenic predisposition to lethal cardiac arrhythmias.Despite decades of investigation and discovery of multiple responsible genes, a molecular ...
Abstract On Behalf SADS-TW BrS registry Background Brugada syndrome (BrS) is an inheritable arrhythmic disease responsible for sudden cardiac death. Information on the prevalence and role of SCN10A variants in BrS is limited and equivocal. Purpose We aimed to investigate the prevalence and role of SCN10A variants in BrS in Han Chinese. Methods From 2000 to 2017, we prospectively and consecutively enrolled 176 unrelated BrS patients from the Han Chinese population in Taiwan (the SADS-TW BrS registry). Thirty-four BrS-related genes were screened by next-generation sequencing, using Taiwan Biobank as the population reference. The pathogenicity was evaluated by literature review and in silico analyses, including the SKAT-O algorithm. Results The SKAT-O algorithm showed that rare variants of SCN10A, but not common variants, were significantly different between BrS patients and healthy controls in the additive and dominant models (p-value <0.001), suggesting that rare SCN10A variants may play a role in BrS. Six likely pathogenic SCN10A variants were found in 6 patients and were compared to 25 pathogenic or likely pathogenic SCN5A variants found in 29 patients. The patients with likely pathogenic SCN10A variants tended to exhibit sudden death in older age and have a shorter QRS interval than those carrying pathogenic or likely pathogenic SCN5A variants or no variants in either gene (p = 0.06, 0.07, respectively). Collectively, the prevalence of likely pathogenic SCN10A variants was 3.4% in Han Chinese patients with BrS in Taiwan. Conclusions SCN10A likely pathogenic variants were present in 3.4% of Han Chinese BrS patients. Rare SCN10A variants may play a role in BrS, and may have impact on clinical and electrocardiographic manifestations. Table 1. Patient Nucleotide Amino acid TWB gnomAD_EA REVEL CADD PHRED SIFT Polyphen-2 GERP++ 1 c.5789A > T p.D1930V 0.001318 0.0008700 0.479 24.5 Damaging Possibly damaging 4.22 2 c.2341G > A p.G781R 0 0.00005301 0.866 33 Damaging Probably damaging 4.83 3 c.5587C > T p.R1863W 0.000502 0 0.832 27.8 Damaging Probably damaging 1.97 4 c.2161C > T p.P721S 0.000989 0.0009016 0.933 28.5 Damaging Probably damaging 4.19 5 c.3749G > A p.R1250Q 0 0 0.907 31 Damaging Probably damaging 4.23 6 c.1825A > T p.R609W 0.000659 0.0001591 0.811 32 Damaging Probably damaging 4.28 Clinical and predicted functional characteristics of 6 likely pathogenic SCN10A variants. EA = East Asian; GERP = Genomic Evolutionary Rate Profiling; TWB = Taiwan Biobank. Transcript: NM_006514.3. Abstract 299 Figure. Location of the SCN10A variants
Background The effects of carperitide on left atrial pressure ( LAP ) in dogs with mitral valve disease (mitral regurgitation, MR ) have not been documented. Objective The objective was to compare the short‐term effects of carperitide versus furosemide on LAP and neurohumoral factors in MR dogs. Animals Six healthy Beagle dogs weighing 9.8–12.6 kg (2 males and 4 females; aged 3 years) were used. Methods Experimental, randomized, cross‐over, and interventional study. Carperitide 0.1 μg/kg/min or furosemide 0.17 mg/kg/h (1 mg/kg/6 h) was administered to dogs with surgically induced MR for 6 hours, and after a 14 day wash‐out period, the other drug was administered. LAP , plasma renin activity, plasma aldosterone, and echocardiographic variables were measured. Results Left atrial pressure was decreased similarly after the administration of carperitide 0.1 μg/kg/min and furosemide 0.17 mg/kg/h (1 mg/kg/6 h) compared with baseline in dogs with MR (Baseline 14.75 ± 3.74 mmHg, carperitide 10.24 ± 4.97 mmHg, P < .01, furosemide 10.77 ± 5.06 mmHg, P < .05). Plasma renin activity and plasma aldosterone were significantly lower after the administration of carperitide than after the administration of furosemide ( P < .05, respectively). Conclusions and Clinical Importance Carperitide significantly decreased LAP in dogs with acute MR caused by experimental chordal rupture. Carperitide can have additional benefits from the viewpoint of minimal activation of neurohumoral factors in the treatment of dogs with MR . Additional studies in dogs with spontaneous disease are warranted.
membrane of myocytes (Figure C), and disruption of the nuclear membrane (Figure D).Genetic analysis revealed a heterozygous splicing mutation (IVS1+1G>A) of the lamin gene (LMNA) in both the proband and her 26-yearold son, who recorded a normal ECG; the proband had a PPM implanted.Clinicopathological decision, as well as histopathological findings, lead to the possibility of lamin A/C cardiomyopathy.
Abstract Desmin‐related myopathy (DRM) is a rare heritable cardiac and skeletal muscle disease caused by mutations in the desmin gene ( DES ). DRM is generally characterized by skeletal muscle weakness, conduction disturbance, and dilated cardiomyopathy. However, the clinical cardiac phenotypes of DRM are not yet fully understood. Herein, we report the first case of DRM with the de novo missense DES mutation, R454W, that is characterized by left ventricular non‐compaction cardiomyopathy, progressive cardiac conduction defect, spontaneous coronary artery dissection, and no skeletal muscle weakness. Our case findings suggest that clinicians should genetically test patients who have cardiomyopathy, progressive cardiac conduction defect, and coronary artery dissection, even if the patient has neither family history of DRM nor skeletal muscle symptoms.
Brugada syndrome (BrS) is an inherited channelopathy responsible for almost 20% of sudden cardiac deaths in patients with nonstructural cardiac diseases. Approximately 70% of BrS patients, the causative gene mutation(s) remains unknown. In this study, we used whole exome sequencing to investigate candidate mutations in a family clinically diagnosed with BrS. A heterozygous 1616G>A substitution (R539Q mutation) was identified in the transmembrane protein 168 (TMEM168) gene of symptomatic individuals. Similar to endogenous TMEM168, both TMEM168 wild-type (WT) and mutant proteins that were ectopically induced in HL-1 cells showed nuclear membrane localization. A significant decrease in Na+ current and Nav1.5 protein expression was observed in HL-1 cardiomyocytes expressing mutant TMEM168. Ventricular tachyarrhythmias and conduction disorders were induced in the heterozygous Tmem168 1616G>A knock-in mice by pharmacological stimulation, but not in WT mice. Na+ current was reduced in ventricular cardiomyocytes isolated from the Tmem168 knock-in heart, and Nav1.5 expression was also impaired. This impairment was dependent on increased Nedd4-2 binding to Nav1.5 and subsequent ubiquitination. Collectively, our results show an association between the TMEM168 1616G>A mutation and arrhythmogenesis in a family with BrS.
