Showing papers in "Circulation-cardiovascular Genetics in 2016"

Epigenetic Signatures of Cigarette Smoking

Abstract: Background —DNA methylation leaves a long-term signature of smoking exposure and is one potential mechanism by which tobacco exposure predisposes to adverse health outcomes, such as cancers, osteoporosis, lung, and cardiovascular disorders. Methods and Results —To comprehensively determine the association between cigarette smoking and DNA methylation, we conducted a meta-analysis of genome-wide DNA methylation assessed using the Illumina BeadChip 450K array on 15,907 blood derived DNA samples from participants in 16 cohorts (including 2,433 current, 6,518 former, and 6,956 never smokers). Comparing current versus never smokers, 2,623 CpG sites (CpGs), annotated to 1,405 genes, were statistically significantly differentially methylated at Bonferroni threshold of p<1×10-7 (18,760 CpGs at False Discovery Rate (FDR)<0.05). Genes annotated to these CpGs were enriched for associations with several smoking-related traits in genome-wide studies including pulmonary function, cancers, inflammatory diseases and heart disease. Comparing former versus never smokers, 185 of the CpGs that differed between current and never smokers were significant p<1×10-7 (2,623 CpGs at FDR<0.05), indicating a pattern of persistent altered methylation, with attenuation, after smoking cessation. Transcriptomic integration identified effects on gene expression at many differentially methylated CpGs. Conclusions —Cigarette smoking has a broad impact on genome-wide methylation that, at many loci, persists many years after smoking cessation. Many of the differentially methylated genes were novel genes with respect to biologic effects of smoking, and might represent therapeutic targets for prevention or treatment of tobacco-related diseases. Methylation at these sites could also serve as sensitive and stable biomarkers of lifetime exposure to tobacco smoke.

Treatment Gaps in Adults With Heterozygous Familial Hypercholesterolemia in the United States: Data From the CASCADE-FH Registry.

Abstract: Background— Cardiovascular disease burden and treatment patterns among patients with familial hypercholesterolemia (FH) in the United States remain poorly described. In 2013, the FH Foundation launched the Cascade Screening for Awareness and Detection (CASCADE) of FH Registry to address this knowledge gap. Methods and Results— We conducted a cross-sectional analysis of 1295 adults with heterozygous FH enrolled in the CASCADE-FH Registry from 11 US lipid clinics. Median age at initiation of lipid-lowering therapy was 39 years, and median age at FH diagnosis was 47 years. Prevalent coronary heart disease was reported in 36% of patients, and 61% exhibited 1 or more modifiable risk factors. Median untreated low-density lipoprotein cholesterol (LDL-C) was 239 mg/dL. At enrollment, median LDL-C was 141 mg/dL; 42% of patients were taking high-intensity statin therapy and 45% received >1 LDL-lowering medication. Among FH patients receiving LDL-lowering medication(s), 25% achieved an LDL-C 1 LDL-lowering medication (1.80; 1.34–2.41). Conclusions— FH patients in the CASCADE-FH Registry are diagnosed late in life and often do not achieve adequate LDL-C lowering, despite a high prevalence of coronary heart disease and risk factors. These findings highlight the need for earlier diagnosis of FH and initiation of lipid-lowering therapy, more consistent use of guideline-recommended LDL-lowering therapy, and comprehensive management of traditional coronary heart disease risk factors.

International Registry of Patients Carrying TGFBR1 or TGFBR2 Mutations: Results of the MAC (Montalcino Aortic Consortium)

Abstract: Background—The natural history of aortic diseases in patients with TGFBR1 or TGFBR2 mutations reported by different investigators has varied greatly. In particular, the current recommendations for ...

Spectrum and Prevalence of CALM1-, CALM2-, and CALM3-Encoded Calmodulin Variants in Long QT Syndrome and Functional Characterization of a Novel Long QT Syndrome-Associated Calmodulin Missense Variant, E141G.

Abstract: Background—Calmodulin (CaM) is encoded by 3 genes, CALM1, CALM2, and CALM3, all of which harbor pathogenic variants linked to long QT syndrome (LQTS) with early and severe expressivity. These LQTS-...

Mendelian Randomization Studies Do Not Support a Role for Vitamin D in Coronary Artery Disease

Abstract: Background—Observational studies support a possible association between decreased vitamin D levels and risk of coronary artery disease (CAD); however, it remains unclear whether this relationship i...

Nutrigenomics, the Microbiome, and Gene-Environment Interactions: New Directions in Cardiovascular Disease Research, Prevention, and Treatment

Abstract: Cardiometabolic diseases are the leading cause of death worldwide and are strongly linked to both genetic and nutritional factors. The field of nutrigenomics encompasses multiple approaches aimed a...

Whole-Exome Molecular Autopsy After Exertion-Related Sudden Unexplained Death in the Young.

Abstract: Background —Targeted postmortem genetic testing of the four major channelopathy-susceptibility genes ( KCNQ1 , KCNH2 , SCN5A , and RYR2 ) have yielded putative pathogenic mutations in up to 25-30% of autopsy-negative sudden unexplained death in the young (SUDY) cases with highest yields derived from the subset of exertion-related SUDY. Here, we evaluate the role of whole exome sequencing (WES) in exertion-related SUDY cases. Methods and Results —From 1998-2010, 32 cases of exertion-related SUDY were referred by Medical Examiners for a cardiac channel molecular autopsy. A mutational analysis of the major long QT syndrome (LQTS)-susceptibility genes ( KCNQ1 , KCNH2 , and SCN5A ) and catecholaminergic polymorphic ventricular tachycardia (CPVT)-susceptibility gene ( RYR2 ) identified a putative pathogenic mutation in 11 cases. WES was performed on the remaining 21 targeted gene-negative SUDY cases. Following WES, a gene-specific surveillance of all genes (N=100) implicated in sudden death was performed to identify putative pathogenic mutation(s). Three of these 21 decedents had a clinically "actionable", pathogenic mutation (CALM2-F90L, CALM2-N98S, and PKP2-N634fs). Of the 18 remaining cases, 7 hosted at least one variant of unknown significance with a minor allele frequency < 1:20,000. The overall yield of pathogenic mutations was higher among decedents 1-10 years (10/11, 91%) than those 11-19 years of age (4/21, 19%, p=0.0001). Conclusions —Molecular screening in this clinical scenario is appropriate with a pathogenic mutation detection rate of 44% using direct DNA sequencing followed by WES. Only 5 of the 100 interrogated sudden death genes hosted "actionable" pathogenic mutations for over one third of these exertion related, autopsy negative SUDY cases.

CD36 Is a Matrix Metalloproteinase-9 Substrate That Stimulates Neutrophil Apoptosis and Removal during Cardiac Remodeling

Abstract: Background —After myocardial infarction (MI), the left ventricle (LV) undergoes a wound healing response that includes the robust infiltration of neutrophils and macrophages to facilitate removal of dead myocytes as well as turnover of the extracellular matrix (ECM). Matrix metalloproteinase (MMP)-9 is a key enzyme that regulates post-MI LV remodeling. Methods and Results —Infarct regions from wild type and MMP-9 null mice (n=8/group) analyzed by glycoproteomics showed that of 541 N -glycosylated proteins quantified, 45 proteins were at least two-fold up- or down-regulated with MMP-9 deletion (all p<0.05). Cartilage intermediate layer protein (CILP) and platelet glycoprotein 4 (CD36) were identified as having the highest fold increase in MMP-9 null mice. By immunoblotting, CD36 but not CILP decreased steadily over the time course post-MI, which identified CD36 as a candidate MMP-9 substrate. MMP-9 was confirmed in vitro and in vivo to proteolytically degrade CD36. In vitro stimulation of day 7 post-MI macrophages with MMP-9 or a CD36 blocking peptide reduced phagocytic capacity. Dual immunofluorescence revealed concomitant accumulation of apoptotic neutrophils in the MMP-9 null group compared to WT. In vitro stimulation of isolated neutrophils with MMP-9 decreased neutrophil apoptosis, indicated by reduced caspase-9 expression. Conclusions —Our data reveals a new cell signaling role for MMP-9 through CD36 degradation to regulate macrophage phagocytosis and neutrophil apoptosis.

Combination of Whole Genome Sequencing, Linkage, and Functional Studies Implicates a Missense Mutation in Titin as a Cause of Autosomal Dominant Cardiomyopathy With Features of Left Ventricular Noncompaction.

Abstract: Background —High throughput next generation sequencing techniques have made whole genome sequencing accessible in clinical practice, however, the abundance of variation in the human genomes makes the identification of a disease-causing mutation on a background of benign rare variants challenging. Methods and Results —Here we combine whole genome sequencing with linkage analysis in a three-generation family affected by cardiomyopathy with features of autosomal dominant left-ventricular non-compaction cardiomyopathy. A missense mutation in the giant protein titin is the only plausible disease-causing variant that segregates with disease amongst the eight surviving affected individuals, with interrogation of the entire genome excluding other potential causes. This A178D missense mutation, affecting a conserved residue in the second immunoglobulin-like domain of titin, was introduced in a bacterially expressed recombinant protein fragment and biophysically characterised in comparison to its wild-type counterpart. Multiple experiments, including size exclusion chromatography, small angle X-ray scattering and circular dichroism spectroscopy suggest partial unfolding and domain destabilisation in the presence of the mutation. Moreover, binding experiments in mammalian cells show that the mutation markedly impairs binding to the titin ligand telethonin. Conclusions —Here we present genetic and functional evidence implicating the novel A178D missense mutation in titin as the cause of a highly penetrant familial cardiomyopathy with features of left-ventricular non-compaction. This expands the spectrum of titin's roles in cardiomyopathies. It furthermore highlights that rare titin missense variants, currently often ignored or left un-interpreted, should be considered to be relevant for cardiomyopathies and can be identified by the approach presented here.

Utilization of Whole Exome Sequencing to Identify Causative Mutations in Familial Congenital Heart Disease.

Abstract: Background— Congenital heart disease (CHD) is the most common type of birth defect with family- and population-based studies supporting a strong genetic cause for CHD. The goal of this study was to determine whether a whole exome sequencing (WES) approach could identify pathogenic-segregating variants in multiplex CHD families. Methods and Results— WES was performed on 9 kindreds with familial CHD, 4 with atrial septal defects, 2 with patent ductus arteriosus, 2 with tetralogy of Fallot, and 1 with pulmonary valve dysplasia. Rare variants (<1% minor allele frequency) that segregated with disease were identified by WES, and variants in 69 CHD candidate genes were further analyzed. These selected variants were subjected to in silico analysis to predict pathogenicity and resulted in the discovery of likely pathogenic mutations in 3 of 9 (33%) families. A GATA4 mutation in the transactivation domain, p.G115W, was identified in familial atrial septal defects and demonstrated decreased transactivation ability in vitro. A p.I263V mutation in TLL1 was identified in an atrial septal defects kindred and is predicted to affect the enzymatic functionality of TLL1. A disease-segregating splice donor site mutation in MYH11 (c.4599+1delG) was identified in familial patent ductus arteriosus and found to disrupt normal splicing of MYH11 mRNA in the affected individual. Conclusions— Our findings demonstrate the clinical utility of WES to identify causative mutations in familial CHD and demonstrate the successful use of a CHD candidate gene list to allow for a more streamlined approach enabling rapid prioritization and identification of likely pathogenic variants from large WES data sets. Clinical Trial Registration— URL: ; Unique Identifier: NCT0112048.

Enhancing Literacy in Cardiovascular Genetics: A Scientific Statement From the American Heart Association

Abstract: Advances in genomics are enhancing our understanding of the genetic basis of cardiovascular diseases, both congenital and acquired, and stroke. These advances include finding genes that cause or increase the risk for childhood and adult-onset diseases, finding genes that influence how patients respond to medications, and the development of genetics-guided therapies for diseases. However, the ability of cardiovascular and stroke clinicians to fully understand and apply this knowledge to the care of their patients has lagged. This statement addresses what the specialist caring for patients with cardiovascular diseases and stroke should know about genetics; how they can gain this knowledge; how they can keep up-to-date with advances in genetics, genomics, and pharmacogenetics; and how they can apply this knowledge to improve the care of patients and families with cardiovascular diseases and stroke.

Elevated Plasma Cardiac Troponin T Levels Caused by Skeletal Muscle Damage in Pompe Disease

Abstract: Background— Elevated plasma cardiac troponin T (cTnT) levels in patients with neuromuscular disorders may erroneously lead to the diagnosis of acute myocardial infarction or myocardial injury. Methods and Results— In 122 patients with Pompe disease, the relationship between cTnT, cardiac troponin I, creatine kinase (CK), CK-myocardial band levels, and skeletal muscle damage was assessed. ECG and echocardiography were used to evaluate possible cardiac disease. Patients were divided into classic infantile, childhood-onset, and adult-onset patients. cTnT levels were elevated in 82% of patients (median 27 ng/L, normal values <14 ng/L). Cardiac troponin I levels were normal in all patients, whereas CK-myocardial band levels were increased in 59% of patients. cTnT levels correlated with CK levels in all 3 subgroups ( P <0.001). None of the abnormal ECGs recorded in 21 patients were indicative of acute myocardial infarction, and there were no differences in cTnT levels between patients with and without (n=90) abnormalities on ECG (median 28 ng/L in both groups). The median left ventricular mass index measured with echocardiography was normal in all the 3 subgroups. cTnT mRNA expression in skeletal muscle was not detectable in controls but was strongly induced in patients with Pompe disease. cTnT protein was identified by mass spectrometry in patient-derived skeletal muscle tissue. Conclusions— Elevated plasma cTnT levels in patients with Pompe disease are associated with skeletal muscle damage, rather than acute myocardial injury. Increased cTnT levels in Pompe disease and likely other neuromuscular disorders should be interpreted with caution to avoid unnecessary cardiac interventions.

Genotype-Dependent Effects of Dalcetrapib on Cholesterol Efflux and Inflammation: Concordance With Clinical Outcomes.

Abstract: Background—Dalcetrapib effects on cardiovascular outcomes are determined by adenylate cyclase 9 gene polymorphisms. Our aim was to determine whether these clinical end point results are also associ...

Homozygous Familial Hypercholesterolemia in Spain: Prevalence and Phenotype-Genotype Relationship.

Abstract: Background —Homozygous familial hypercholesterolemia (HoFH) is a rare disease characterized by elevated plasma levels of low-density lipoprotein cholesterol (LDL-C) and extremely high risk of premature atherosclerotic cardiovascular disease (ASCVD) HoFH is caused by mutations in several genes, including LDL receptor ( LDLR ), apolipoprotein B ( APOB ), proprotein convertase subtilisin/kexin type 9 ( PCSK9 ), and LDL protein receptor adaptor 1 ( LDLRAP1 ) No epidemiological studies have assessed HoFH prevalence, or the clinical and molecular characteristics of this condition Here we aimed to characterize HoFH in Spain Methods and Results —Data were collected from the Spanish Dyslipidemia Registry of the Spanish Atherosclerosis Society and from all molecular diagnoses performed for FH in Spain between 1996 and 2015 (n=16,751) Clinical data included baseline lipid levels and ASCVD events A total of 97 subjects were identified as having HoFH-of whom, 47 were true homozygous (1 for APOB , 5 for LDLRAP1 , and 41 for LDLR ), 45 compound heterozygous for LDLR , 3 double heterozygous for LDLR and PSCK9 , and 2 double heterozygous for LDLR and APOB No PSCK9 homozygous cases were identified Two variants in LDLR were identified in 48% of the molecular studies Over 50% of patients did not meet the classical HoFH diagnosis criteria The estimated HoFH prevalence was 1:450,000 Compared to compound heterozygous cases, true homozygous cases showed more aggressive phenotypes with higher LDL-C and more ASCVD events Conclusions —HoFH frequency in Spain was higher than expected Clinical criteria would underestimate the actual prevalence of individuals with genetic HoFH, highlighting the importance of genetic analysis to improve FH diagnosis accuracy

Genetic Susceptibility to Lipid Levels and Lipid Change Over Time and Risk of Incident Hyperlipidemia in Chinese Populations

Abstract: Background—Multiple genetic loci associated with lipid levels have been identified predominantly in Europeans, and the issue of to what extent these genetic loci can predict blood lipid levels incr...

Rare Exome Sequence Variants in CLCN6 Reduce Blood Pressure Levels and Hypertension Risk.

Abstract: Background— Rare genetic variants influence blood pressure (BP). Methods and Results— Whole-exome sequencing was performed on DNA samples from 17 956 individuals of European ancestry and African ancestry (14 497, first-stage discovery and 3459, second-stage discovery) to examine the effect of rare variants on hypertension and 4 BP traits: systolic BP, diastolic BP, pulse pressure, and mean arterial pressure. Tests of ≈170 000 common variants (minor allele frequency, ≥1%; statistical significance, P ≤2.9×10−7) and gene-based tests of rare variants (minor allele frequency, <1%; ≈17 000 genes; statistical significance, P ≤1.5×10−6) were evaluated for each trait and ancestry, followed by multiethnic meta-analyses. In the first-stage discovery, rare coding variants (splicing, stop-gain, stop-loss, nonsynonymous variants, or indels) in CLCN6 were associated with lower diastolic BP (cumulative minor allele frequency, 1.3%; β =−3.20; P =4.1×10−6) and were independent of a nearby common variant (rs17367504) previously associated with BP. CLCN6 rare variants were also associated with lower systolic BP ( β =−4.11; P =2.8×10−4), mean arterial pressure ( β =−3.50; P =8.9×10−6), and reduced hypertension risk (odds ratio, 0.72; P =0.017). Meta-analysis of the 2-stage discovery samples showed that CLCN6 was associated with lower diastolic BP at exome-wide significance (cumulative minor allele frequency, 1.1%; β =−3.30; P =5.0×10−7). Conclusions— These findings implicate the effect of rare coding variants in CLCN6 in BP variation and offer new insights into BP regulation.

Multiethnic Exome-Wide Association Study of Subclinical Atherosclerosis

Abstract: Background —The burden of subclinical atherosclerosis in asymptomatic individuals is heritable and associated with elevated risk of developing clinical coronary heart disease (CHD). We sought to identify genetic variants in protein-coding regions associated with subclinical atherosclerosis and the risk of subsequent CHD. Methods and Results —We studied a total of 25,109 European ancestry and African-American participants with coronary artery calcification (CAC) measured by cardiac computed tomography and 52,869 with common carotid intima media thickness (CIMT) measured by ultrasonography within the Cohorts for Heart and Aging Research in Genomic Epidemiology (CHARGE) Consortium. Participants were genotyped for 247,870 DNA sequence variants (231,539 in exons) across the genome. A meta-analysis of exome-wide association studies was performed across cohorts for CAC and CIMT. APOB p.Arg3527Gln was associated with four-fold excess CAC ( P = 3×10 -10 ). The APOE e2 allele (p.Arg176Cys) was associated with both 22.3% reduced CAC ( P = 1×10 -12 ) and 1.4% reduced CIMT ( P = 4×10 -14 ) in carriers compared with non-carriers. In secondary analyses conditioning on LDL cholesterol concentration, the e2 protective association with CAC, although attenuated, remained strongly significant. Additionally, the presence of e2 was associated with reduced risk for CHD (OR 0.77; P = 1×10 -11 ). Conclusions —Exome-wide association meta-analysis demonstrates that protein-coding variants in APOB and APOE associate with subclinical atherosclerosis. APOE e2 represents the first significant association for multiple subclinical atherosclerosis traits across multiple ethnicities as well as clinical CHD.

Systematic Characterization of Long Noncoding RNAs Reveals the Contrasting Coordination of Cis- and Trans-Molecular Regulation in Human Fetal and Adult Hearts.

Abstract: Background— The molecular regulation of heart development is regulated by cis - and trans -factors acting on the genome and epigenome. As a class of important regulatory RNAs, the role of long noncoding RNAs (lncRNAs) in human heart development is still poorly understood. Furthermore, factors that interact with lncRNAs in this process are not well characterized. Methods and Results— Using RNA sequencing, we systematically define the contrasting lncRNA expression patterns between fetal and adult hearts. We report that lncRNAs upregulated in adult versus fetal heart have different sequence features and distributions. For example, the adult heart expresses more sense lncRNAs compared with fetal heart. We also report the coexpression of lncRNAs and neighboring coding genes that have important functions in heart development. Importantly, the regulation of lncRNA expression during fetal to adult heart development seems to be due, in part, to the coordination of specific developmental epigenetic modifications, such as H3K4me1 and H3k4me3. The expression of promoter-associated lncRNAs in adult and fetal hearts also seems to be related to these epigenetic states. Finally, transcription factor–binding analysis suggests that lncRNAs are directly regulating cardiac gene expression during development. Conclusions— We provide a systematic analysis of lncRNA control of heart development that gives clues to the roles that specific lncRNAs play in fetal and adult hearts.

Clinical Utility of Multimarker Genetic Risk Scores for Prediction of Incident Coronary Heart Disease

Abstract: Background —We evaluated whether including multi-locus genetic risk scores (GRS's) into the Framingham Risk Equation improves the predictive capacity, discrimination and reclassification of asymptomatic individuals with respect to coronary heart disease (CHD) risk Methods and Results —We performed a cohort study among 51,954 European-ancestry members of a Northern California integrated health care system (67% female; mean age 59) free of CHD at baseline (2007-08) Four GRS's were constructed using between 8 and 51 previously identified genetic variants After a mean (± SD) follow-up of 59 (± 15) years, 1,864 incident CHD events were documented All GRS's were linearly associated with CHD in a model adjusted by individual risk factors: HR [95%CI] per SD unit: 121 [115-126] for GRS\_8, 120 [115-126] for GRS\_12, 123 [117-128] for GRS\_36 and 123 [117-128] for GRS\_51 Inclusion of the GRS's improved the C-statistic (Δc-statistic=0008 for GRS\_8 and GRS\_36; 0007 for GRS\_12; and 0009 for GRS\_51; all p<0001) The net reclassification improvement (NRI) was 5% for GRS\_8, GRS\_12 and GRS\_36 and 4% for GRS\_51 in the entire cohort, and was (after correcting for bias) 9% for GRS\_8 and GRS\_12, and 7% for GRS\_36 and GRS\_51 when analyzing those classified as intermediate Framingham risk (10-20%) The number required to treat to prevent 1 CHD after selectively treating with statins up-reclassified subjects on the basis of genetic information was 36 for GRS\_8 and GRS\_12, 41 for GRS\_36 and 43 for GRS\_51 Conclusions —Our results demonstrate significant and clinically relevant incremental discriminative/predictive capability of four multi-locus GRS's for incident CHD among subjects of European ancestry

International Genome-Wide Association Study Consortium Identifies Novel Loci Associated With Blood Pressure in Children and Adolescents

Abstract: Background— Our aim was to identify genetic variants associated with blood pressure (BP) in childhood and adolescence. Methods and Results— Genome-wide association study data from participating European ancestry cohorts of the Early Genetics and Lifecourse Epidemiology (EAGLE) Consortium was meta-analyzed across 3 epochs; prepuberty (4–7 years), puberty (8–12 years), and postpuberty (13–20 years). Two novel loci were identified as having genome-wide associations with systolic BP across specific age epochs: rs1563894 ( ITGA11 , located in active H3K27Ac mark and transcription factor chromatin immunoprecipitation and 5′-C-phosphate-G-3′ methylation site) during prepuberty ( P =2.86×10–8) and rs872256 during puberty ( P =8.67×10–9). Several single-nucleotide polymorphism clusters were also associated with childhood BP at P <5×10–3. Using a P value threshold of <5×10–3, we found some overlap in variants across the different age epochs within our study and between several single-nucleotide polymorphisms in any of the 3 epochs and adult BP-related single-nucleotide polymorphisms. Conclusions— Our results suggest that genetic determinants of BP act from childhood, develop over the lifecourse, and show some evidence of age-specific effects.

New Insights Into the Genetic Basis of Inherited Arrhythmia Syndromes.

Abstract: Inherited arrhythmia syndromes encompass several different diseases, including long QT syndrome (LQTS), Brugada syndrome (BrS), catecholaminergic polymorphic ventricular tachycardia (CPVT), short QT syndrome (SQTS), idiopathic ventricular fibrillation (IVF), and progressive cardiac conduction system disease (PCCD).1 The heart is typically structurally normal with no evidence of disease macroscopically. They are an important cause for sudden cardiac death in the young, and an autopsy is typically negative.2,3 Ventricular arrhythmias are caused by mutations of ion channels and their interacting proteins, predominantly involving potassium, sodium, and calcium handling.4 Genetic studies have identified the specific genetic abnormalities that underpin these diseases, even permitting diagnosis in the deceased using postmortem genetic testing (the molecular autopsy).3 Most arrhythmia syndromes are inherited in an autosomal dominant manner, such that first-degree family members have a 50% chance of inheriting the disease. Identification of the mutation allows for predictive genetic testing in other living family members.4 Variable penetrance is common in all arrhythmia syndromes, the same mutation in the same family causing wide variation in phenotype.4 This suggests that other factors such as genetic modifiers and environmental factors may influence the phenotype. This review will highlight the latest developments in understanding the genetic basis of inherited arrhythmia syndromes and discusses the new opportunities and challenges faced with evolving genetic technologies including determining pathogenicity and the utility of large genetic databases. Finally, we will discuss newly described entities that continue the evolving theme of genetic syndromes with phenotypic overlap. Early views that a single genotype associates with a particular phenotype continue to be challenged by our greater understanding of the genotype–phenotype relationship. ### Long QT Syndrome Congenital LQTS is diagnosed in the presence of a prolonged corrected QT (QTc) interval after secondary causes (eg, QT-prolonging medications or electrolyte abnormalities) are excluded.1 The 2013 Heart Rhythm …

Genetic Variation in the SLC8A1 Calcium Signaling Pathway Is Associated With Susceptibility to Kawasaki Disease and Coronary Artery Abnormalities.

Abstract: Background—Kawasaki disease (KD) is an acute pediatric vasculitis in which host genetics influence both susceptibility to KD and the formation of coronary artery aneurysms. Variants discovered by g...

Decoding the Long Noncoding RNA During Cardiac Maturation A Roadmap for Functional Discovery

Abstract: Background —Cardiac maturation during perinatal transition of heart is critical for functional adaptation to hemodynamic load and nutrient environment. Perturbation in this process has major implications in congenital heart defects (CHDs). Transcriptome programming during perinatal stages is important information but incomplete in current literature, particularly, the expression profiles of the long noncoding RNAs (lncRNAs) are not fully elucidated. Methods and Results —From comprehensive analysis of transcriptomes derived from neonatal mouse heart left and right ventricles, a total of 45,167 unique transcripts were identified, including 21,916 known and 2,033 novel lncRNAs. Among these lncRNAs, 196 exhibited significant dynamic regulation along maturation process. By implementing parallel weighted gene co-expression network analysis (WGCNA) of mRNA and lncRNA datasets, several lncRNA modules coordinately expressed in a developmental manner similar to protein coding genes, while few lncRNAs revealed chamber specific patterns. Out of 2,262 lncRNAs located within 50 KBs of protein coding genes, 5% significantly correlate with the expression of their neighboring genes. The impact of Ppp1r1b-lncRNA on the corresponding partner gene Tcap was validated in cultured myoblasts. This concordant regulation was also conserved in human infantile hearts. Furthermore, the Ppp1r1b-lncRNA/Tcap expression ratio was identified as a molecular signature that differentiated CHD phenotypes. Conclusions —The study provides the first high-resolution landscape on neonatal cardiac lncRNAs and reveals their potential interaction with mRNA transcriptome during cardiac maturation. Ppp1r1b-lncRNA was identified as a regulator of Tcap expression with dynamic interaction in postnatal cardiac development and CHDs.

Search for Rare Copy-Number Variants in Congenital Heart Defects Identifies Novel Candidate Genes and a Potential Role for FOXC1 in Patients With Coarctation of the Aorta

Abstract: Background— Congenital heart defects are the most frequent malformations among newborns and a frequent cause of morbidity and mortality. Although genetic variation contributes to congenital heart defects, their precise molecular bases remain unknown in the majority of patients. Methods and Results— We analyzed, by high-resolution array comparative genomic hybridization, 316 children with sporadic, nonsyndromic congenital heart defects, including 76 coarctation of the aorta, 159 transposition of the great arteries, and 81 tetralogy of Fallot, as well as their unaffected parents. We identified by array comparative genomic hybridization, and validated by quantitative real-time polymerase chain reaction, 71 rare de novo (n=8) or inherited (n=63) copy-number variants (CNVs; 50 duplications and 21 deletions) in patients. We identified 113 candidate genes for congenital heart defects within these CNVs, including BTRC , CHRNB3 , CSRP2BP , ERBB2 , ERMARD , GLIS3 , PLN , PTPRJ , RLN3 , and TCTE3 . No de novo CNVs were identified in patients with transposition of the great arteries in contrast to coarctation of the aorta and tetralogy of Fallot ( P =0.002; Fisher exact test). A search for transcription factor binding sites showed that 93% of the rare CNVs identified in patients with coarctation of the aorta contained at least 1 gene with FOXC1-binding sites. This significant enrichment ( P <0.0001; permutation test) was not observed for the CNVs identified in patients with transposition of the great arteries and tetralogy of Fallot. We hypothesize that these CNVs may alter the expression of genes regulated by FOXC1. Foxc1 belongs to the forkhead transcription factors family, which plays a critical role in cardiovascular development in mice. Conclusions— These data suggest that deregulation of FOXC1 or its downstream genes play a major role in the pathogenesis of coarctation of the aorta in humans.

Cardiovascular Risk Factors Associated With Blood Metabolite Concentrations and Their Alterations During a 4-Year Period in a Population-Based Cohort.

Abstract: Background —The effects of lifestyle risk-factors considered collectively on the human metabolism are so far unknown We aim to investigate the association of these risk-factors with metabolites and their changes over 4 years Methods and Results —163 metabolites were measured in serum samples with the AbsoluteIDQ kit p150 (Biocrates) following a targeted metabolomics approach, in a population-based cohort of 1030 individuals, aged 45-83 at baseline We evaluated associations between metabolite concentrations (28 acylcarnitines, 14 amino acids, 9 lyso-phosphocholines, 72 phosphocholines, 10 sphingomyelins and sum of hexoses) and 5 lifestyle risk factors (BMI, alcohol consumption, smoking, diet and exercise) Multilevel or simple linear regression modelling adjusted for relevant covariates was used for the evaluation of cross-sectional and longitudinal associations respectively, multiple testing correction was based on false discovery rate BMI, alcohol and smoking were associated with lipid metabolism (reduced lyso- and acyl-alkyl-phosphatidylcholines and increased diacylphosphatidylcholines concentrations) Smoking showed positive associations with acylcarnitines and BMI correlated inversely with nonessential amino acids Fewer metabolites showed relative changes that were associated with baseline risk-factors: increases in 5 different acyl-alkyl phosphatidylcholines were associated with lower alcohol consumption and BMI, and with a healthier diet Increased levels of tyrosine were associated with BMI Sex-specific effects of smoking and BMI were found specifically related to acylcarnitine metabolism: in women higher BMI and in men more pack-years were associated with increases in acylcarnitines Conclusions —This study showed sex-specific effects of lifestyle risks factors on human metabolism and highlighted their long-term metabolic consequences

SPARC-Dependent Cardiomyopathy in Drosophila.

Abstract: Background —The Drosophila heart is an important model for studying the genetics underpinning mammalian cardiac function. The system comprises contractile cardiomyocytes, adjacent to which are pairs of highly endocytic pericardial nephrocytes that modulate cardiac function by uncharacterized mechanisms. Identifying these mechanisms and the molecules involved is important because they may be relevant to human cardiac physiology. Methods and Results —This work aimed to identify circulating cardiomodulatory factors of potential relevance to humans using the Drosophila nephrocyte-cardiomyocyte system. A Kruppel-Like Factor 15 ( dKlf15 ) loss-of-function strategy was used to ablate nephrocytes and then heart function and the hemolymph proteome were analysed. Ablation of nephrocytes led to a severe cardiomyopathy characterized by a lengthening of diastolic interval. Rendering adult nephrocytes dysfunctional by disrupting their endocytic function or temporally-conditional knock-down of dKlf15 led to a similar cardiomyopathy. Proteomics revealed that nephrocytes regulate the circulating levels of many secreted proteins, the most notable of which was the evolutionarily conserved matricellular protein SPARC (Secreted Protein Acidic and Rich in Cysteine), a protein involved in mammalian cardiac function. Finally, reducing SPARC gene dosage ameliorated the cardiomyopathy that developed in the absence of nephrocytes. Conclusions —The data implicate SPARC in the non-cell autonomous control of cardiac function in Drosophila and suggest that modulation of SPARC gene expression may ameliorate cardiac dysfunction in humans.

Novel Genetic Loci Associated With Retinal Microvascular Diameter.

Abstract: Background-There is increasing evidence that retinal microvascular diameters are associated with cardiovascular and cerebrovascular conditions. The shared genetic effects of these associations are currently unknown. The aim of this study was to increase our understanding of the genetic factors that mediate retinal vessel size. Methods and Results-This study extends previous genome-wide association study results using 24 000+ multiethnic participants from 7 discovery cohorts and 5000+ subjects of European ancestry from 2 replication cohorts. Using the Illumina HumanExome BeadChip, we investigate the association of single-nucleotide polymorphisms and variants collectively across genes with summary measures of retinal vessel diameters, referred to as the central retinal venule equivalent and the central retinal arteriole equivalent. We report 4 new loci associated with central retinal venule equivalent, one of which is also associated with central retinal arteriole equivalent. The 4 single-nucleotide polymorphisms are rs7926971 in TEAD1 (P=3.1×10- 11; minor allele frequency=0.43), rs201259422 in TSPAN10 (P=4.4×10-9; minor allele frequency=0.27), rs5442 in GNB3 (P=7.0×10-10; minor allele frequency=0.05), and rs1800407 in OCA2 (P=3.4×10-8; minor allele frequency=0.05). The latter single-nucleotide polymorphism, rs1800407, was also associated with central retinal arteriole equivalent (P=6.5×10-12). Results from the gene-based burden tests were null. In phenotype look-ups, single-nucleotide polymorphism rs201255422 was associated with both systolic (P=0.001) and diastolic blood pressures (P=8.3×10-04). Conclusions-Our study expands the understanding of genetic factors influencing the size of the retinal microvasculature. These findings may also provide insight into the relationship between retinal and systemic microvascular disease.

RP1-13D10.2 Is a Novel Modulator of Statin-Induced Changes in Cholesterol

Abstract: Background— Numerous genetic contributors to cardiovascular disease risk have been identified through genome-wide association studies; however, identifying the molecular mechanism underlying these associations is not straightforward. The Justification for the Use of Statins in Primary Prevention: An Intervention Trial Evaluating Rosuvastatin (JUPITER) trial of rosuvastatin users identified a sub–genome-wide association of rs6924995, a single-nucleotide polymorphism ≈10 kb downstream of myosin regulatory light chain interacting protein ( MYLIP , aka IDOL and inducible degrader of low-density lipoprotein receptor [LDLR]), with LDL cholesterol statin response. Interestingly, although this signal was initially attributed to MYLIP , rs6924995 lies within RP1-13D10.2 , an uncharacterized long noncoding RNA. Methods and Results— Using simvastatin and sham incubated lymphoblastoid cell lines from participants of the Cholesterol and Pharmacogenetics (CAP) simvastatin clinical trial, we found that statin-induced change in RP1-13D10.2 levels differed between cell lines from the tails of the white and black low-density lipoprotein cholesterol response distributions, whereas no difference in MYLIP was observed. RP1-13D10.2 overexpression in Huh7 and HepG2 increased LDLR transcript levels, increased LDL uptake, and decreased media levels of apolipoprotein B. In addition, we found a trend of slight differences in the effects of RP1-13D10.2 overexpression on LDLR transcript levels between hepatoma cells transfected with the rs6924995 A versus G allele and a suggestion of an association between rs6924995 and RP1-10D13.2 expression levels in the CAP lymphoblastoid cell lines. Finally, RP1-13D10.2 expression levels seem to be sterol regulated, consistent with its potential role as a novel lipid regulator. Conclusions— RP1-13D10.2 is a long noncoding RNA that regulates LDLR and may contribute to low-density lipoprotein cholesterol response to statin treatment. These findings highlight the potential role of noncoding RNAs as determinants of interindividual variation in drug response.

Endothelial Cell Bioenergetics and Mitochondrial DNA Damage Differ in Humans Having African or West Eurasian Maternal Ancestry.

Abstract: Background—We hypothesized that endothelial cells having distinct mitochondrial genetic backgrounds would show variation in mitochondrial function and oxidative stress markers concordant with known...

SCARB1 Gene Variants Are Associated With the Phenotype of Combined High High-Density Lipoprotein Cholesterol and High Lipoprotein (a).

Abstract: Background— SR-B1 (scavenger receptor class B type 1), encoded by the gene SCARB1 , is a lipoprotein receptor that binds both high-density lipoprotein (HDL) and low-density lipoprotein. We reported that SR-B1 is also a receptor for lipoprotein (a) (Lp(a)), mediating cellular uptake of Lp(a) in vitro and promoting clearance of Lp(a) in vivo. Although genetic variants in SCARB1 are associated with variations in HDL level, no SCARB1 variants affecting Lp(a) have been reported. Methods and Results— In an index subject with high levels of HDL cholesterol and Lp(a), SCARB1 was sequenced and demonstrated a missense mutation resulting in an S129L substitution in exon 3. To follow up, 2 cohorts (GeneSTAR, the family-based Genetic Study of Atherosclerosis Risk [n=543], and CCHS, the population-based Copenhagen City Heart Study [n=5835]) were screened for combined HDL cholesterol and Lp(a) elevations. Subjects with the extreme phenotype (HDL >80 mg/dL and Lp(a) >100 nmol/L in GeneSTAR, n=8, and >100 mg/dL in CCHS, n=9) underwent sequencing of SCARB1 exons; 15 of 18 from the combined population demonstrated genetic variants, including rare or uncommon missense or splice site mutations in 9 and homozygous synonymous variants in 6. Functional studies with 4 of the SCARB1 variants (c.386C>T, c.631-14T>G, c.4G>A, and c.631-53mC>T & c.726+55mCG>CA) showed decreased receptor function in vitro. Conclusions— Human SCARB1 gene variants are associated with a new lipid phenotype, characterized by high levels of both HDL cholesterol and Lp(a). SCARB1 exonic variants often result in diminished function of translated SR-B1 via reduced binding/intracellular transport of Lp(a).