75 results found
Lahrouchi N, Raju H, Lodder EM, et al., 2019, The yield of postmortem genetic testing in sudden death cases with structural findings at autopsy., Eur J Hum Genet
Sudden cardiac death (SCD) is often associated with structural abnormalities of the heart during autopsy. This study sought to compare the diagnostic yield of postmortem genetic testing in (1) cases with structural findings of uncertain significance at autopsy to (2) cases with autopsy findings diagnostic of cardiomyopathy. We evaluated 57 SCD cases with structural findings at cardiac autopsy. Next-generation sequencing using a panel of 77 primary electrical disorder and cardiomyopathy genes was performed. Pathogenic and likely pathogenic variants were classified using American College of Medical Genetics (ACMG) consensus guidelines. In 29 cases (51%) autopsy findings of uncertain significance were identified whereas in 28 cases (49%) a diagnosis of cardiomyopathy was established. We identified a pathogenic or likely pathogenic variant in 10 cases (18%); in 1 (3%) case with non-specific autopsy findings compared with 9 (32%) cases with autopsy findings diagnostic of cardiomyopathy (p = 0.0054). The yield of genetic testing in SCD cases with autopsy findings consistent with cardiomyopathy is comparable with the yield in cardiomyopathy patients that are alive. Genetic testing in cases with findings of uncertain significance offers lower clinical utility than in cardiomyopathy, with lower yields than detected previously. This highlights the need for stringent evaluation of variant pathogenicity.
Thomson KL, Ormondroyd E, Harper AR, et al., 2019, Analysis of 51 proposed hypertrophic cardiomyopathy genes from genome sequencing data in sarcomere negative cases has negligible diagnostic yield, Genetics in Medicine, Vol: 21, Pages: 1576-1584, ISSN: 1098-3600
PURPOSE: Increasing numbers of genes are being implicated in Mendelian disorders and incorporated into clinical test panels. However, lack of evidence supporting the gene-disease relationship can hinder interpretation. We explored the utility of testing 51 additional genes for hypertrophic cardiomyopathy (HCM), one of the most commonly tested Mendelian disorders. METHODS: Using genome sequencing data from 240 sarcomere gene negative HCM cases and 6229 controls, we undertook case-control and individual variant analyses to assess 51 genes that have been proposed for HCM testing. RESULTS: We found no evidence to suggest that rare variants in these genes are prevalent causes of HCM. One variant, in a single case, was categorized as likely to be pathogenic. Over 99% of variants were classified as a variant of uncertain significance (VUS) and 54% of cases had one or more VUS. CONCLUSION: For almost all genes, the gene-disease relationship could not be validated and lack of evidence precluded variant interpretation. Thus, the incremental diagnostic yield of extending testing was negligible, and would, we propose, be outweighed by problems that arise with a high rate of uninterpretable findings. These findings highlight the need for rigorous, evidence-based selection of genes for clinical test panels.
Corden B, Jarman J, Whiffin N, et al., Association between titin truncating variants and life-threatening cardiac arrhythmias in patients with dilated cardiomyopathy and implantable defibrillator, JAMA Network Open, ISSN: 2574-3805
Wei W, Tuna S, Keogh MJ, et al., 2019, Germline selection shapes human mitochondrial DNA diversity, Science, Vol: 364, ISSN: 0036-8075
INTRODUCTIONOnly 2.4% of the 16.5-kb mitochondrial DNA (mtDNA) genome shows homoplasmic variation at >1% frequency in humans. Migration patterns have contributed to geographic differences in the frequency of common genetic variants, but population genetic evidence indicates that selection shapes the evolving mtDNA phylogeny. The mechanism and timing of this process are not clear.Unlike the nuclear genome, mtDNA is maternally transmitted and there are many copies in each cell. Initially, a new genetic variant affects only a proportion of the mtDNA (heteroplasmy). During female germ cell development, a reduction in the amount of mtDNA per cell causes a “genetic bottleneck,” which leads to rapid segregation of mtDNA molecules and different levels of heteroplasmy between siblings. Although heteroplasmy is primarily governed by random genetic drift, there is evidence of selection occurring during this process in animals. Yet it has been difficult to demonstrate this convincingly in humans.RATIONALETo determine whether there is selection for or against heteroplasmic mtDNA variants during transmission, we studied 12,975 whole-genome sequences, including 1526 mother–offspring pairs of which 45.1% had heteroplasmy affecting >1% of mtDNA molecules. Harnessing both the mtDNA and nuclear genome sequences, we then determined whether the nuclear genetic background influenced mtDNA heteroplasmy, validating our findings in another 40,325 individuals.RESULTSPreviously unknown mtDNA variants were less likely to be inherited than known variants, in which the level of heteroplasmy tended to increase on transmission. Variants in the ribosomal RNA genes were less likely to be transmitted, whereas variants in the noncoding displacement (D)–loop were more likely to be transmitted. MtDNA variants predicted to affect the protein sequence tended to have lower heteroplasmy levels than synonymous variants. In 12,975 individuals, we identified a correlation between
Whiffin N, Karczewski K, Zhang X, et al., Characterising the loss-of-function impact of 5' untranslated region variants in 15,708 individuals, Nature Communications, ISSN: 2041-1723
Upstream open reading frames (uORFs) are tissue-specific cis-regulators of protein translation. Isolated reports have shown that variants that create or disrupt uORFs can cause disease. Here, in a systematic genome-wide study using 15,708 whole genome sequences, we show that variants that create new upstream start codons, and variants disrupting stop sites of existing uORFs, are under strong negative selection. This selection signal is significantly stronger for variants arising upstream of genes intolerant to loss-of-function variants. Furthermore, variants creating uORFs that overlap the coding sequence show signals of selection equivalent to coding loss-of-function variants. Finally, we identify specific genes where modification of uORFs likely represents an important disease mechanism, and report a novel uORF frameshift variant upstream of NF2 in neurofibromatosis. Our results highlight uORF-perturbing variants as an under-recognised functional class that contribute to penetrant human disease, and demonstrate the power of large-scale population sequencing data in studying non-coding variant classes.
Lota AS, Halliday BP, Hatipoglu S, et al., 2019, Risk prediction in patients with mild dilated cardiomyopathy by cardiovascular magnetic resonance: integrating assessment of myocardial mechanics with tissue characterisation, Publisher: WILEY, Pages: 406-407, ISSN: 1388-9842
Mazzarotto F, Tayal P, Buchan R, et al., 2019, RE-EVALUATING THE GENETIC CONTRIBUTION OF MONOGENIC DILATED CARDIOMYOPATHY, Annual Conference of the British-Cardiovascular-Society (BCS) - Digital Health Revolution, Publisher: BMJ PUBLISHING GROUP, Pages: A100-A100, ISSN: 1355-6037
Ingles J, Goldstein J, Thaxton C, et al., 2019, Evaluating the Clinical Validity of Hypertrophic Cardiomyopathy Genes, CIRCULATION, Vol: 139, Pages: 1745-1745, ISSN: 0009-7322
Ho CY, Day SM, Ashley EA, et al., 2019, Response by Ho et al to letter regarding article, "Genotype and lifetime burden of disease in hypertrophic cardiomyopathy: Insights from the sarcomeric human cardiomyopathy registry (SHaRe)"., Circulation, Vol: 139, Pages: 1559-1560, ISSN: 0009-7322
Garcia-Pavia P, Kim Y, Restrepo-Cordoba A, et al., Genetic variants associated with cancer therapy-induced cardiomyopathy, Circulation, ISSN: 0009-7322
BackgroundCancer therapy-induced cardiomyopathy (CCM) is associated with cumulative drug exposures and pre-existing cardiovascular disorders. These parametersincompletely account for substantial inter-individual susceptibility to CCM. We hypothesized that rare variants in cardiomyopathy genes contribute to CCM.MethodsWe studied 213 CCM patients from three cohorts: retrospectively recruited adults with diverse cancers (n=99), prospectively phenotyped breast cancer adults (n=73) and prospectively phenotyped children with acute myeloid leukemia (n=41). Cardiomyopathy genes, including nine pre-specified genes were sequenced. The prevalence of rare variants was compared between CCM cohorts and The Cancer Genome Atlas (TCGA) participants(n=2053), healthy volunteers(n=445), and ancestry-matchedreference population. Clinical characteristics and outcomes were assessed, stratified by genotypes. A prevalent CCM genotype was modeled in anthracycline-treated mice.ResultsCCM was diagnosed 0.4-9 years after chemotherapy; 90% of these patients received anthracyclines. Adult CCM patients had cardiovascular risk factors similar to the U.S. population. Among nine prioritized genes CCM patients had more rare protein-altering variants than comparative cohorts (p≤1.98e-04). Titin-truncating variants (TTNtv) predominated, occurring in 7.5% CCM patients versus 1.1% TCGA participants (p=7.36e-08), 0.7% healthy volunteers (p=3.42e-06), and 0.6% reference population (p=5.87e-14). Adult CCM patients with TTNtv experienced more heart failure and atrial fibrillation (p=0.003)and impaired myocardial recovery (p=0.03) than those without.Consistent with human data, anthracycline-treated TTNtv mice and isolated TTNtv cardiomyocytes showed sustained contractile dysfunction unlike wildtype (p=0.0004 and p<0.002, respectively).ConclusionsUnrecognized rare variants in cardiomyopathy-associated genes, particularly TTNtv, increased the risk for CCM in children and adults, and adverse cardiac events
Rhodes CJ, Batai K, Bleda M, et al., 2019, Genetic determinants of risk in pulmonary arterial hypertension: international case-control studies and meta-analysis, Lancet Respiratory Medicine, Vol: 7, Pages: 227-238, ISSN: 2213-2600
BackgroundRare genetic variants cause pulmonary arterial hypertension, but the contribution of common genetic variation to disease risk and natural history is poorly characterised. We tested for genome-wide association for pulmonary arterial hypertension in large international cohorts and assessed the contribution of associated regions to outcomes.MethodsWe did two separate genome-wide association studies (GWAS) and a meta-analysis of pulmonary arterial hypertension. These GWAS used data from four international case-control studies across 11 744 individuals with European ancestry (including 2085 patients). One GWAS used genotypes from 5895 whole-genome sequences and the other GWAS used genotyping array data from an additional 5849 individuals. Cross-validation of loci reaching genome-wide significance was sought by meta-analysis. Conditional analysis corrected for the most significant variants at each locus was used to resolve signals for multiple associations. We functionally annotated associated variants and tested associations with duration of survival. All-cause mortality was the primary endpoint in survival analyses.FindingsA locus near SOX17 (rs10103692, odds ratio 1·80 [95% CI 1·55–2·08], p=5·13 × 10–15) and a second locus in HLA-DPA1 and HLA-DPB1 (collectively referred to as HLA-DPA1/DPB1 here; rs2856830, 1·56 [1·42–1·71], p=7·65 × 10–20) within the class II MHC region were associated with pulmonary arterial hypertension. The SOX17 locus had two independent signals associated with pulmonary arterial hypertension (rs13266183, 1·36 [1·25–1·48], p=1·69 × 10–12; and rs10103692). Functional and epigenomic data indicate that the risk variants near SOX17 alter gene regulation via an enhancer active in endothelial cells. Pulmonary arterial hypertension risk variants determined haplotype-specific enhancer activity, and CRISPR-media
Ingles J, Goldstein J, Thaxton C, et al., 2019, Evaluating the clinical validity of hypertrophic cardiomyopathy genes, Circulation: Cardiovascular Genetics, Vol: 12, ISSN: 1942-325X
Background:Genetic testing for families with hypertrophic cardiomyopathy (HCM) provides a significant opportunity to improve care. Recent trends to increase gene panel sizes often mean variants in genes with questionable association are reported to patients. Classification of HCM genes and variants is critical, as misclassification can lead to genetic misdiagnosis. We show the validity of previously reported HCM genes using an established method for evaluating gene-disease associations.Methods:A systematic approach was used to assess the validity of reported gene-disease associations, including associations with isolated HCM and syndromes including left ventricular hypertrophy. Genes were categorized as having definitive, strong, moderate, limited, or no evidence of disease causation. We also reviewed current variant classifications for HCM in ClinVar, a publicly available variant resource.Results:Fifty-seven genes were selected for curation based on their frequent inclusion in HCM testing and prior association reports. Of 33 HCM genes, only 8 (24%) were categorized as definitive (MYBPC3, MYH7, TNNT2, TNNI3, TPM1, ACTC1, MYL2, and MYL3); 3 had moderate evidence (CSRP3, TNNC1, and JPH2; 33%); and 22 (66%) had limited (n=16) or no evidence (n=6). There were 12 of 24 syndromic genes definitively associated with isolated left ventricular hypertrophy. Of 4191 HCM variants in ClinVar, 31% were in genes with limited or no evidence of disease association.Conclusions:The majority of genes previously reported as causative of HCM and commonly included in diagnostic tests have limited or no evidence of disease association. Systematically curated HCM genes are essential to guide appropriate reporting of variants and ensure the best possible outcomes for HCM families.
Miles C, Finocchiaro G, Papadakis M, et al., 2019, Sudden death and left ventricular involvement in arrhythmogenic cardiomyopathy, Circulation, Vol: 139, Pages: 1786-1797, ISSN: 0009-7322
BACKGROUND: Arrhythmogenic cardiomyopathy (ACM) is an inherited heart muscle disorder characterized by myocardial fibro-fatty replacement and an increased risk of sudden cardiac death (SCD). Originally described as a right ventricular (RV) disease, ACM is increasingly recognized as a biventricular entity. We evaluated pathological, genetic, and clinical associations in a large SCD cohort. METHODS: We investigated 5205 consecutive cases of SCD referred to a national cardiac pathology center between 1994 and 2018. Hearts and tissue blocks were examined by expert cardiac pathologists. Following comprehensive histological evaluation, 202 cases (4%) were diagnosed with ACM. Of these, 15 (7%) were diagnosed ante-mortem with dilated cardiomyopathy (DCM)(n=8) or ACM (n=7). Prior symptoms, medical history, circumstances of death, and participation in competitive sport were recorded. Post-mortem genetic testing was undertaken in 24/202 (12%). Rare genetic variants were classified according to American College of Medical Genetics and Genomics (ACMG) criteria. RESULTS: Of 202 ACM decedents (35.4±13.2 years; 82% male), 157 (78%) reported no prior cardiac symptoms. Forty-one decedents (41/202; 20%) were participants in competitive sport. The adjusted odds of dying during physical exertion were higher in males than females (OR 4.58; 95% CI 1.54-13.68; p=0.006) and in competitive athletes compared with non-athletes (OR 16.62; 95% CI 5.39-51.24; p<0.001). None of the decedents with an ante-mortem diagnosis of DCM fulfilled definite 2010 Task Force criteria. Macroscopic appearance of the heart was normal in 40/202 (20%) cases. There was left ventricular (LV) histopathological involvement in 176/202 (87%). Isolated RV disease was seen in 13%, isolated LV disease in 17%, and biventricular involvement in 70%. Among whole hearts, the most common areas of fibro-fatty infiltration were the LV posterobasal (68%) and anterolateral walls (58%). Post-mortem genetic testing yielded pa
Walsh R, Mazzarotto F, Whiffin N, et al., 2019, Quantitative approaches to variant classification increase the yield and precision of genetic testing in Mendelian diseases: The case of hypertrophic cardiomyopathy, Genome Medicine, Vol: 11, ISSN: 1756-994X
BackgroundInternational guidelines for variant interpretation in Mendelian disease set stringent criteria to report a variant as (likely) pathogenic, prioritising control of false-positive rate over test sensitivity and diagnostic yield. Genetic testing is also more likely informative in individuals with well-characterised variants from extensively studied European-ancestry populations. Inherited cardiomyopathies are relatively common Mendelian diseases that allow empirical calibration and assessment of this framework.MethodsWe compared rare variants in large hypertrophic cardiomyopathy (HCM) cohorts (up to 6179 cases) to reference populations to identify variant classes with high prior likelihoods of pathogenicity, as defined by etiological fraction (EF). We analysed the distribution of variants using a bespoke unsupervised clustering algorithm to identify gene regions in which variants are significantly clustered in cases.ResultsAnalysis of variant distribution identified regions in which variants are significantly enriched in cases and variant location was a better discriminator of pathogenicity than generic computational functional prediction algorithms. Non-truncating variant classes with an EF ≥ 0.95 were identified in five established HCM genes. Applying this approach leads to an estimated 14–20% increase in cases with actionable HCM variants, i.e. variants classified as pathogenic/likely pathogenic that might be used for predictive testing in probands’ relatives.ConclusionsWhen found in a patient confirmed to have disease, novel variants in some genes and regions are empirically shown to have a sufficiently high probability of pathogenicity to support a “likely pathogenic” classification, even without additional segregation or functional data. This could increase the yield of high confidence actionable variants, consistent with the framework and recommendations of current guidelines. The techniques outlined offer a consisten
Halliday BP, Wassall R, Lota A, et al., 2019, Withdrawal of pharmacological treatment for heart failure in patients with recovered dilated cardiomyopathy (TRED-HF): an open-label, pilot, randomised trial, The Lancet, Vol: 393, Pages: 61-73, ISSN: 0140-6736
BackgroundPatients with dilated cardiomyopathy whose symptoms and cardiac function have recovered often ask whether their medications can be stopped. The safety of withdrawing treatment in this situation is unknown.MethodsWe did an open-label, pilot, randomised trial to examine the effect of phased withdrawal of heart failure medications in patients with previous dilated cardiomyopathy who were now asymptomatic, whose left ventricular ejection fraction (LVEF) had improved from less than 40% to 50% or greater, whose left ventricular end-diastolic volume (LVEDV) had normalised, and who had an N-terminal pro-B-type natriuretic peptide (NT-pro-BNP) concentration less than 250 ng/L. Patients were recruited from a network of hospitals in the UK, assessed at one centre (Royal Brompton and Harefield NHS Foundation Trust, London, UK), and randomly assigned (1:1) to phased withdrawal or continuation of treatment. After 6 months, patients in the continued treatment group had treatment withdrawn by the same method. The primary endpoint was a relapse of dilated cardiomyopathy within 6 months, defined by a reduction in LVEF of more than 10% and to less than 50%, an increase in LVEDV by more than 10% and to higher than the normal range, a two-fold rise in NT-pro-BNP concentration and to more than 400 ng/L, or clinical evidence of heart failure, at which point treatments were re-established. The primary analysis was by intention to treat. This trial is registered with ClinicalTrials.gov, number NCT02859311.FindingsBetween April 21, 2016, and Aug 22, 2017, 51 patients were enrolled. 25 were randomly assigned to the treatment withdrawal group and 26 to continue treatment. Over the first 6 months, 11 (44%) patients randomly assigned to treatment withdrawal met the primary endpoint of relapse compared with none of those assigned to continue treatment (Kaplan-Meier estimate of event rate 45·7% [95% CI 28·5–67·2]; p=0·0001). After 6 months, 25 (96%) of 2
Whiffin N, Roberts AM, Minikel E, et al., 2019, Using high-resolution variant frequencies empowers clinical genome interpretation and enables investigation of genetic architecture, American Journal of Human Genetics, Vol: 104, Pages: 187-190, ISSN: 0002-9297
Ho CY, Day SM, Ashley EA, et al., 2018, Genotype and Lifetime Burden of Disease in Hypertrophic Cardiomyopathy:Insights from the Sarcomeric Human Cardiomyopathy Registry (SHaRe), Circulation Journal, Vol: 138, Pages: 1387-1398, ISSN: 1346-9843
Background:A better understanding of the factors that contribute to heterogeneous outcomes and lifetime disease burden in hypertrophic cardiomyopathy (HCM) is critically needed to improve patient management and outcomes. The SHaRe registry (Sarcomeric Human Cardiomyopathy Registry) was established to provide the scale of data required to address these issues, aggregating longitudinal data sets curated by 8 international HCM specialty centers.Methods:Data on 4591 patients with HCM (2763 genotyped) followed up for a mean of 5.4±6.9 years (24 791 patient-years; median, 2.9 years; interquartile range, 0.3–7.9 years) were analyzed for cardiac arrest, cardiac transplantation, appropriate implantable cardioverter-defibrillator therapy, all-cause death, atrial fibrillation, stroke, New York Heart Association functional class III/IV symptoms (all making up the overall composite end point), and left ventricular ejection fraction <35%. Outcomes were analyzed individually and as composite end points.Results:Median age at diagnosis was 45.8 (interquartile range, 30.9–58.1) years, and 37% of patients were female. Age at diagnosis and sarcomere mutation status were predictive of outcomes. Patients <40 years old at diagnosis had a 77% (95% CI, 72–80) cumulative incidence of the overall composite outcome by 60 years of age compared with 32% (95% CI, 29–36) by 70 years of age for patients diagnosed at >60 years old. Young patients with HCM (age, 20–29 years) had 4-fold higher mortality than the general US population at a similar age. Patients with pathogenic/likely pathogenic sarcomere mutations had a 2-fold greater risk for adverse outcomes compared with patients without mutations; sarcomere variants of uncertain significance were associated with intermediate risk. Heart failure and atrial fibrillation were the most prevalent adverse events, although typically not emerging for several years after diagnosis. Ventricular arrhythmias
Hosseini SM, Kim R, Udupa S, et al., 2018, Reappraisal of reported genes for sudden arrhythmic death: an evidence-based evaluation of gene validity for Brugada syndrome, Circulation, Vol: 138, Pages: 1195-1205, ISSN: 0009-7322
Background -Implicit in the genetic evaluation of patients with suspected genetic diseases is the assumption that the genes evaluated are causative for the disease based on robust scientific and statistical evidence. However, in the past 20 years considerable variability has existed in the study design and quality of evidence supporting reported gene-disease associations raising concerns of the validity of many published disease-causing genes. Brugada syndrome (BrS) is an arrhythmia syndrome with a risk of sudden death. More than 20 genes have been reported to cause BrS and are assessed routinely on genetic testing panels in the absence of a systematic, evidence-based evaluation of the evidence supporting the causality of these genes. Methods -We evaluated the clinical validity of genes tested by diagnostic laboratories for BrS by assembling three gene curation teams. Using an evidence-based semi-quantitative scoring system of genetic and experimental evidence for gene-disease associations, curation teams independently classified genes as demonstrating Limited, Moderate, Strong or Definitive evidence for disease causation in BrS. The classification of curator teams was reviewed by a Clinical Domain Expert Panel who could modify the classifications based on their independent review and consensus. Results -Of 21 genes curated for clinical validity, biocurators classified only 1 gene (SCN5A) as Definitive evidence, while all other genes were classified as Limited evidence. Following comprehensive review by the Clinical Domain Expert Panel, all 20 genes classified as Limited evidence were re-classified as Disputed in regards to any assertions of disease causality for BrS. Conclusions -Our results contest the clinical validity of all but one gene clinically tested and reported to be associated with BrS. These findings warrant a systematic, evidence-based evaluation for reported gene-disease associations prior to use in patient care.
Ma D, Liu Z, Loh LJ, et al., 2018, Identification of an INa-dependent and Ito-mediated proarrhythmic mechanism in cardiomyocytes derived from pluripotent stem cells of a Brugada syndrome patient, Scientific Reports, Vol: 8, ISSN: 2045-2322
Brugada syndrome (BrS) is an inherited cardiac arrhythmia commonly associated with SCN5A mutations, yet its ionic mechanisms remain unclear due to a lack of cellular models. Here, we used human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) from a BrS patient (BrS1) to evaluate the roles of Na+ currents (INa) and transient outward K+ currents (Ito) in BrS induced action potential (AP) changes. To understand the role of these current changes in repolarization we employed dynamic clamp to "electronically express" IK1 and restore normal resting membrane potentials and allow normal recovery of the inactivating currents, INa, ICa and Ito. HiPSC-CMs were generated from BrS1 with a compound SCN5A mutation (p. A226V & p. R1629X) and a healthy sibling control (CON1). Genome edited hiPSC-CMs (BrS2) with a milder p. T1620M mutation and a commercial control (CON2) were also studied. CON1, CON2 and BrS2, had unaltered peak INa amplitudes, and normal APs whereas BrS1, with over 75% loss of INa, displayed a loss-of-INa basal AP morphology (at 1.0 Hz) manifested by a reduced maximum upstroke velocity (by ~80%, p < 0.001) and AP amplitude (p < 0.001), and an increased phase-1 repolarization pro-arrhythmic AP morphology (at 0.1 Hz) in ~25% of cells characterized by marked APD shortening (~65% shortening, p < 0.001). Moreover, Ito densities of BrS1 and CON1 were comparable and increased from 1.0 Hz to 0.1 Hz by ~ 100%. These data indicate that a repolarization deficit could be a mechanism underlying BrS.
Oates EC, Jones KJ, Donkervoort S, et al., 2018, Congenital titinopathy: comprehensive characterisation and pathogenic insights, Annals of Neurology, Vol: 83, Pages: 1105-1124, ISSN: 0364-5134
Objective: Comprehensive clinical characterisation of congenital titinopathy to facilitate diagnosis and management of this important emerging disorder.Methods: Using massively parallel sequencing we identified 30 patients from 27 families with two pathogenic nonsense, frameshift and/or splice site TTN mutations in trans. We then undertook a detailed analysis of the clinical, histopathology and imaging features of these patients.Results: All patients had prenatal‐ or early‐onset hypotonia and/or congenital contractures. None had ophthalmoplegia. Scoliosis and respiratory insufficiency typically developed early and progressed rapidly, whereas limb weakness was often slowly progressive, and usually did not prevent independent walking. Cardiac involvement was present in 46% of patients. Relatives of two patients had dilated cardiomyopathy. Creatine kinase levels were normal to moderately elevated. Increased fibre size variation, internalised nuclei and cores were common histopathological abnormalities. Cap‐like structures, whorled or ring fibres, and mitochondrial accumulations were also observed. Muscle MRI showed gluteal, hamstring and calf muscle involvement. Western blot analysis showed a near‐normal sized titin protein in all samples.The presence of two mutations predicted to impact both N2BA and N2B cardiac isoforms appeared to be associated with greatest risk of cardiac involvement. One third of patients had one mutation predicted to impact exons present in fetal skeletal muscle, but not included within the mature skeletal muscle isoform transcript. This strongly suggests developmental isoforms are involved in the pathogenesis of this congenital/early‐onset disorder.Interpretation: This detailed clinical reference dataset will greatly facilitate diagnostic confirmation and management of patients and has provided important insights into disease pathogenesis.
Ware JS, Amor-Salamanca A, Tayal U, et al., 2018, A genetic etiology for alcohol-induced cardiac toxicity, Journal of the American College of Cardiology, Vol: 71, Pages: 2293-2302, ISSN: 0735-1097
Background: Alcoholic cardiomyopathy (ACM) is defined by a dilated and impaired left ventricle due to chronic excess alcohol consumption. It is largely unknown what factors determine cardiac toxicity on exposure to alcohol.Objectives: We sought to evaluate the role of variation in cardiomyopathy-associated genes in the pathophysiology of ACM, and to examine the effects of alcohol intake and genotype on DCM severity.Methods: We characterized 141 ACM cases, 716 dilated cardiomyopathy (DCM) cases and 445 healthy volunteers. We compared the prevalence of rare, protein-altering variants in 9 genes associated with inherited DCM. We evaluated the effect of genotype and alcohol-consumption on phenotype in DCM.Results: Variants in well-characterized DCM-causing genes were more prevalent in patients with ACM than controls (13.5% vs 2.9%; P=1.2e-05), but similar between patients with ACM and DCM (19.4%; P=0.12) and with a predominant burden of Titin-truncating variants (TTNtv, 9.9%). Separately, we identified an interaction between TTN genotype and excess alcohol consumption in a cohort of DCM patients not meeting ACM criteria. On multivariate analysis, DCM patients with a TTNtv who consumed excess alcohol had an 8.7% absolute reduction in ejection fraction (95% CI -2.3 to -15.1, P<0.007) compared with those without TTNtv and excess alcohol consumption. The presence of TTNtv did not predict phenotype, outcome or functional recovery on treatment in ACM patients. Conclusions: TTNtv represent a prevalent genetic predisposition for ACM, and are also associated with a worse LVEF in DCM patients who consume alcohol above recommended levels. Familial evaluation and genetic testing should be considered in patients presenting with ACM.
Lahrouchi N, Raju H, Lodder E, et al., Yield and clinical utility of the ‘molecular autopsy’ in cases of the Sudden Arrhythmic Death Syndrome (SADS) and their families, Journal of the American College of Cardiology, ISSN: 1558-3597
Post-mortem genetic testing (‘molecular autopsy’) of sudden arrhythmicdeath syndrome (SADS) cases can establish a clear molecular diagnosis in a substantial minority.This complements family evaluation. Classification of pathogenicity of genetic variants must,however, be stringent in order to avoid the over calling of variants of unknown significance ascausative. Children and young adults presenting with seizures and syncope, especially whenassociated with stress or exercise, require thorough cardiac evaluation in order to not misscatecholaminergic polymorphic ventricular tachycardia. Molecular autopsy should not howeverbe restricted to the young as cases over 35 years old also carry diagnostic variants.
Whiffin N, walsh R, Govind R, et al., 2018, CardioClassifier: disease- and gene-specific computational decision support for clinical genome interpretation, Genetics in Medicine, Vol: 20, Pages: 1246-1254, ISSN: 1098-3600
PurposeInternationally adopted variant interpretation guidelines from the American College of Medical Genetics and Genomics (ACMG) are generic and require disease-specific refinement. Here we developed CardioClassifier (http://www.cardioclassifier.org), a semiautomated decision-support tool for inherited cardiac conditions (ICCs).MethodsCardioClassifier integrates data retrieved from multiple sources with user-input case-specific information, through an interactive interface, to support variant interpretation. Combining disease- and gene-specific knowledge with variant observations in large cohorts of cases and controls, we refined 14 computational ACMG criteria and created three ICC-specific rules.ResultsWe benchmarked CardioClassifier on 57 expertly curated variants and show full retrieval of all computational data, concordantly activating 87.3% of rules. A generic annotation tool identified fewer than half as many clinically actionable variants (64/219 vs. 156/219, Fisher’s P = 1.1 × 10−18), with important false positives, illustrating the critical importance of disease and gene-specific annotations. CardioClassifier identified putatively disease-causing variants in 33.7% of 327 cardiomyopathy cases, comparable with leading ICC laboratories. Through addition of manually curated data, variants found in over 40% of cardiomyopathy cases are fully annotated, without requiring additional user-input data.ConclusionCardioClassifier is an ICC-specific decision-support tool that integrates expertly curated computational annotations with case-specific data to generate fast, reproducible, and interactive variant pathogenicity reports, according to best practice guidelines.
Ware JS, 2018, Adaptation and validation of the ACMG/AMP variant classification framework for MYH7-associated inherited cardiomyopathies: Recommendations by ClinGen's Inherited Cardiomyopathy Expert Panel, Genetics in Medicine, Vol: 20, Pages: 351-359, ISSN: 1098-3600
PurposeIntegrating genomic sequencing in clinical care requires standardization of variant interpretation practices. The Clinical Genome Resource has established expert panels to adapt the American College of Medical Genetics and Genomics/Association for Molecular Pathology classification framework for specific genes and diseases. The Cardiomyopathy Expert Panel selected MYH7, a key contributor to inherited cardiomyopathies, as a pilot gene to develop a broadly applicable approach.MethodsExpert revisions were tested with 60 variants using a structured double review by pairs of clinical and diagnostic laboratory experts. Final consensus rules were established via iterative discussions.ResultsAdjustments represented disease-/gene-informed specifications (12) or strength adjustments of existing rules (5). Nine rules were deemed not applicable. Key specifications included quantitative frameworks for minor allele frequency thresholds, the use of segregation data, and a semiquantitative approach to counting multiple independent variant occurrences where fully controlled case-control studies are lacking. Initial inter-expert classification concordance was 93%. Internal data from participating diagnostic laboratories changed the classification of 20% of the variants (n = 12), highlighting the critical importance of data sharing.ConclusionThese adapted rules provide increased specificity for use in MYH7-associated disorders in combination with expert review and clinical judgment and serve as a stepping stone for genes and disorders with similar genetic and clinical characteristics.
Ware JS, Cook SA, 2017, Role of titin in cardiomyopathy: from DNA variants to patient stratification, Nature Reviews Cardiology, Vol: 15, Pages: 241-252, ISSN: 1759-5002
Dilated cardiomyopathy (DCM) affects approximately 1 in 250 individuals and is the leading indication for heart transplantation. DCM is often familial, and the most common genetic predisposition is a truncating variation in the giant sarcomeric protein, titin, which occurs in up to 15% of ambulant patients with DCM and 25% of end-stage or familial cases. In this article, we review the evidence for the role of titin truncation in the pathogenesis of DCM and our understanding of the molecular mechanisms and pathophysiological consequences of variation in the gene encoding titin (TTN). Such variation is common in the general population (up to 1% of individuals), and we consider key features that discriminate variants with disease-causing potential from those that are benign. We summarize strategies for clinical interpretation of genetic variants for use in the diagnosis of patients and the evaluation of their relatives. Finally, we consider the contemporary and potential future role for genetic stratification in cardiomyopathy and in the general population, evaluating titin variation as a predictor of outcome and treatment response for precision medicine.
Miller DC, Harmer SC, Poliandri A, et al., 2017, Ajmaline blocks INa and IKr without eliciting differences between Brugada syndrome patient and control human pluripotent stem cell-derived cardiac clusters, Stem Cell Research, Vol: 25, Pages: 233-244, ISSN: 1873-5061
The class Ia anti-arrhythmic drug ajmaline is used clinically to unmask latent type I ECG in Brugada syndrome (BrS) patients, although its mode of action is poorly characterised.Our aims were to identify ajmaline's mode of action in human induced pluripotent stem cell (hiPSC)-derived cardiomyocytes (CMs), and establish a simple BrS hiPSC platform to test whether differences in ajmaline response could be determined between BrS patients and controls.Control hiPSCs were differentiated into spontaneously contracting cardiac clusters. It was found using multi electrode array (MEA) that ajmaline treatment significantly lengthened cluster activation-recovery interval. Patch clamping of single CMs isolated from clusters revealed that ajmaline can block both INa and IKr.Following generation of hiPSC lines from BrS patients (absent of pathogenic SCN5A sodium channel mutations), analysis of hiPSC-CMs from patients and controls revealed that differentiation and action potential parameters were similar. Comparison of cardiac clusters by MEA showed that ajmaline lengthened activation-recovery interval consistently across all lines.We conclude that ajmaline can block both depolarisation and repolarisation of hiPSC-CMs at the cellular level, but that a more refined integrated tissue model may be necessary to elicit differences in its effect between BrS patients and controls.
Tayal U, Newsome S, Buchan R, et al., 2017, Phenotype and Clinical Outcomes of Titin Cardiomyopathy, Journal of the American College of Cardiology, Vol: 70, Pages: 2264-2274, ISSN: 0735-1097
Background Improved understanding of dilated cardiomyopathy (DCM) due to titin truncation (TTNtv) may help guide patient stratification.Objectives The purpose of this study was to establish relationships among TTNtv genotype, cardiac phenotype, and outcomes in DCM.Methods In this prospective, observational cohort study, DCM patients underwent clinical evaluation, late gadolinium enhancement cardiovascular magnetic resonance, TTN sequencing, and adjudicated follow-up blinded to genotype for the primary composite endpoint of cardiovascular death, and major arrhythmic and major heart failure events.Results Of 716 subjects recruited (mean age 53.5 ± 14.3 years; 469 men [65.5%]; 577 [80.6%] New York Heart Association function class I/II), 83 (11.6%) had TTNtv. Patients with TTNtv were younger at enrollment (49.0 years vs. 54.1 years; p = 0.002) and had lower indexed left ventricular mass (5.1 g/m2 reduction; padjusted = 0.03) compared with patients without TTNtv. There was no difference in biventricular ejection fraction between TTNtv+/− groups. Overall, 78 of 604 patients (12.9%) met the primary endpoint (median follow-up 3.9 years; interquartile range: 2.0 to 5.8 years), including 9 of 71 patients with TTNtv (12.7%) and 69 of 533 (12.9%) without. There was no difference in the composite primary outcome of cardiovascular death, heart failure, or arrhythmic events, for patients with or without TTNtv (hazard ratio adjusted for primary endpoint: 0.92 [95% confidence interval: 0.45 to 1.87]; p = 0.82).Conclusions In this large, prospective, genotype-phenotype study of ambulatory DCM patients, we show that prognostic factors for all-cause DCM also predict outcome in TTNtv DCM, and that TTNtv DCM does not appear to be associated with worse medium-term prognosis.
Heinig M, Adriaens ME, Schafer S, et al., 2017, Natural genetic variation of the cardiac transcriptome in non-diseased donors and patients with dilated cardiomyopathy, Genome Biology, Vol: 18, ISSN: 1474-7596
Background: Genetic variation is an important determinant of RNA transcription and splicing, which in turncontributes to variation in human traits, including cardiovascular diseases.Results: Here we report the first in-depth survey of heart transcriptome variation using RNA-sequencing in 97patients with dilated cardiomyopathy and 108 non-diseased controls. We reveal extensive differences of geneexpression and splicing between dilated cardiomyopathy patients and controls, affecting known as well as noveldilated cardiomyopathy genes. Moreover, we show a widespread effect of genetic variation on the regulation oftranscription, isoform usage, and allele-specific expression. Systematic annotation of genome-wide association SNPsidentifies 60 functional candidate genes for heart phenotypes, representing 20% of all published heart genome-wideassociation loci. Focusing on the dilated cardiomyopathy phenotype we found that eQTL variants are also enriched fordilated cardiomyopathy genome-wide association signals in two independent cohorts.Conclusions: RNA transcription, splicing, and allele-specific expression are each important determinants of the dilatedcardiomyopathy phenotype and are controlled by genetic factors. Our results represent a powerful resource for thefield of cardiovascular genetics.
Ware JS, Wain LV, Channavajjhala SK, et al., 2017, Phenotypic and pharmacogenetic evaluation of patients with thiazide-induced hyponatremia., Journal of Clinical Investigation, Vol: 127, Pages: 3367-3374, ISSN: 0021-9738
Thiazide diuretics are among the most widely used treatments for hypertension, but thiazide-induced hyponatremia (TIH), a clinically significant adverse effect, is poorly understood. Here, we have studied the phenotypic and genetic characteristics of patients hospitalized with TIH. In a cohort of 109 TIH patients, those with severe TIH displayed an extended phenotype of intravascular volume expansion, increased free water reabsorption, urinary prostaglandin E2 excretion, and reduced excretion of serum chloride, magnesium, zinc, and antidiuretic hormone. GWAS in a separate cohort of 48 TIH patients and 2,922 controls from the 1958 British birth cohort identified an additional 14 regions associated with TIH. We identified a suggestive association with a variant in SLCO2A1, which encodes a prostaglandin transporter in the distal nephron. Resequencing of SLCO2A1 revealed a nonsynonymous variant, rs34550074 (p.A396T), and association with this SNP was replicated in a second cohort of TIH cases. TIH patients with the p.A396T variant demonstrated increased urinary excretion of prostaglandin E2 and metabolites. Moreover, the SLCO2A1 phospho-mimic p.A396E showed loss of transporter function in vitro. These findings indicate that the phenotype of TIH involves a more extensive metabolic derangement than previously recognized. We propose one mechanism underlying TIH development in a subgroup of patients in which SLCO2A1 regulation is altered.
Whiffin N, Walsh R, Govind R, et al., 2017, CardioClassifier – demonstrating the power of disease- and gene-specific computational decision support for clinical genome interpretation, Publisher: Cold Spring Harbor Laboratory
<jats:title>ABSTRACT</jats:title><jats:sec><jats:title>Purpose</jats:title><jats:p>Internationally-adopted variant interpretation guidelines from the American College of Medical Genetics and Genomics (ACMG) are generic and require disease-specific refinement. Here we developed CardioClassifier (<jats:ext-link xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="uri" xlink:href="http://www.cardioclassifier.org">www.cardioclassifier.org</jats:ext-link>), a semi-automated decision-support tool for inherited cardiac conditions (ICCs).</jats:p></jats:sec><jats:sec><jats:title>Methods</jats:title><jats:p>CardioClassifier integrates data retrieved from multiple sources with user-input case-specific information, through an interactive interface, to support varian interpretation. Combining disease- and gene-specific knowledge with variant observations in large cohorts of cases and controls, we refined 14 computational ACMG criteria and created three ICC-specific rules.</jats:p></jats:sec><jats:sec><jats:title>Results</jats:title><jats:p>We benchmarked CardioClassifier on 57 expertly-curated variants and show full retrieval of all computational data, concordantly activating 87.3% of rules. A generic annotation tool identified fewer than half as many clinically-actionable variants (64/219 vs 156/219, Fisher’s <jats:bold>P</jats:bold>=1.1x10-18), with important false positives; illustrating the critical importance of disease and gene-specific annotations. CardioClassifier identified putatively disease-causing variants in 33.7% of 327 cardiomyopathy cases, comparable with leading ICC laboratories. Through addition of manually-curated data, variants found in over 40% of cardiomyopathy cases are fully annotated, without requiring additional user-input data.</jats:p></jats:sec><jats:sec><jat
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