Abstract
Cardiac calsequestrin (Casq2) associates with the ryanodine receptor 2 channel in the junctional sarcoplasmic reticulum to regulate Ca2+ release into the cytoplasm. Patients carrying ...mutations in CASQ2 display low resting heart rates under basal conditions and stress-induced polymorphic ventricular tachycardia (CPVT). In this study, we generate and characterize novel conditional deletion and conditional rescue mouse models to test the influence of developmental programs on the heart rate and CPVT phenotypes. We also compare the requirements for Casq2 function in the cardiac conduction system (CCS) and in working cardiomyocytes. Our study shows that the CPVT phenotype is dependent upon concurrent loss of Casq2 function in both the CCS and in working cardiomyocytes. Accordingly, restoration of Casq2 in only the CCS prevents CPVT. In addition, occurrence of CPVT is independent of the developmental history of Casq2-deficiency. In contrast, resting heart rate depends upon Casq2 gene activity only in the CCS and upon developmental history. Finally, our data support a model where low basal heart rate is a significant risk factor for CPVT.
Clinically pertinent electrocardiogram (ECG) data from model systems, such as zebrafish, are crucial for illuminating factors contributing to human cardiac electrophysiological abnormalities and ...disease. Current zebrafish ECG collection strategies have not adequately addressed the consistent acquisition of high-quality traces or sources of phenotypic variation that could obscure data interpretation. Thus, we developed a novel platform to ensure high-quality recording of in vivo subdermal adult zebrafish ECGs and zebrafish ECG reading GUI (zERG), a program to acquire measurements from traces that commercial software cannot examine owing to erroneous peak calling. We evaluate normal ECG trait variation, revealing highly reproducible intervals and wave amplitude variation largely driven by recording artifacts, and identify sex and body size as potential confounders to PR, QRS and QT intervals. With this framework, we characterize the effect of the class I anti-arrhythmic drug flecainide acetate on adults, provide support for the impact of a Long QT syndrome model, and establish power calculations for this and other studies. These results highlight our pipeline as a robust approach to evaluate zebrafish models of human cardiac electrophysiological phenotypes.
Abstract only
Introduction:
Atrial fibrillation (AF) is the most common cardiac arrhythmia, affecting >33 million people worldwide. EKG is a powerful tool to diagnose AF. Earlier studies found common ...and rare genetic variants associated with EKG traits and AF risk. However, each individual genome has thousands of RVs which have not been systematically characterized in EKG traits.
Hypothesis
Individuals with outlier levels of omic measurements in EKG relevant genes are enriched with functional RVs which contribute to AF risk.
Methods
We analyzed transcriptomic, methylomic, proteomic, and whole genome sequencing data from 1319 individuals in TOPMed Multi-Ethnic Study of Atherosclerosis. We prioritized RVs with Watershed integrating genomic annotations and omic outlier signals (Fig A). We applied Watershed posterior probabilities as weights for EKG trait association using 30 million RVs in 4559 individuals. We developed a polygenic risk score (PRS) using RV posteriors to assess risk stratification for PR interval.
Results
The multiomic Watershed model prioritized RVs with large effects as identified by PR interval GWAS (
Fig B
). Each signal contributed to distinct sets of variants. Watershed confirmed known EKG gene associations and implicated splicing outliers in
NDUFB8
as a novel association with QT interval. When incorporated in SKAT test, Watershed leveraged 10x more noncoding RVs and replicated associations between PR interval and
SCN5A
,
MYH6
,
NEBL
, and
GORASP1
(missed by the default SKAT model). An RV score synthesized across 494 genes was correlated with PR interval after adjusting for common variant PRS (
Fig C
), suggesting that Watershed-prioritized RVs can complement common variants to improve patient risk stratification.
Conclusions
Watershed is a promising framework to characterize RVs with functional effects, which informed trait-gene associations and improved patient risk stratification, enhancing mechanistic insights into EKG traits and AF diagnosis.
Metabolomics genome wide association study (GWAS) help outline the genetic contribution to human metabolism. However, studies to date have focused on relatively healthy, population-based samples of ...White individuals. Here, we conducted a GWAS of 537 blood metabolites measured in the Chronic Renal Insufficiency Cohort (CRIC) Study, with separate analyses in 822 White and 687 Black study participants. Trans-ethnic meta-analysis was then applied to improve fine-mapping of potential causal variants. Mean estimated glomerular filtration rate was 44.4 and 41.5 mL/min/1.73m2 in the White and Black participants, respectively. There were 45 significant metabolite associations at 19 loci, including novel associations at PYROXD2, PHYHD1, FADS1-3, ACOT2, MYRF, FAAH, and LIPC. The strength of associations was unchanged in models additionally adjusted for estimated glomerular filtration rate and proteinuria, consistent with a direct biochemical effect of gene products on associated metabolites. At several loci, trans-ethnic meta-analysis, which leverages differences in linkage disequilibrium across populations, reduced the number and/or genomic interval spanned by potentially causal single nucleotide polymorphisms compared to fine-mapping in the White participant cohort alone. Across all validated associations, we found strong concordance in effect sizes of the potentially causal single nucleotide polymorphisms between White and Black study participants. Thus, our study identifies novel genetic determinants of blood metabolites in chronic kidney disease, demonstrates the value of diverse cohorts to improve causal inference in metabolomics GWAS, and underscores the shared genetic basis of metabolism across race.
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Polygenic risk scores (PRSs) for coronary artery disease (CAD) potentially improve cardiovascular risk prediction. However, their relationship with histopathologic features of CAD has never been ...examined systematically.
From 4327 subjects referred to CVPath by the State of Maryland Office Chief Medical Examiner for sudden death between 1994 and 2015, 2455 cases were randomly selected for genotyping. We generated PRS from 291 known CAD risk loci. Detailed histopathologic examination of the coronary arteries was performed in all subjects. The primary study outcome measurements were histopathologic plaque features determining severity of atherosclerosis, including %stenosis, calcification, thin-cap fibroatheromas, and thrombotic CAD.
After exclusion of cases with insufficient DNA sample quality or with missing data, 954 cases (mean age, 48.8±14.7 years; 75.7% men) remained in the final study cohort. Subjects in the highest PRS quintile exhibited more severe atherosclerosis compared with subjects in the lowest quintile, with greater %stenosis (80.3%±27.0% versus 50.4%±38.7%; adjusted
<0.001) and a higher frequency of calcification (69.6% versus 35.8%; adjusted
=0.004) and thin-cap fibroatheroma (26.7% versus 9.5%; adjusted
=0.007). Even after adjustment for traditional CAD risk factors, subjects within the highest PRS quintile had higher odds of severe atherosclerosis (ie, ≥75% stenosis; adjusted odds ratio, 3.77 95% CI, 2.10-6.78;
<0.001) and plaque rupture (adjusted odds ratio, 4.05 95% CI, 2.26-7.24;
<0.001). Moreover, subjects within the highest quintile had higher odds of CAD-associated cause of death, especially among those aged ≤50 years (adjusted odds ratio, 4.08 95% CI, 2.01-8.30;
<0.001). No statistically significant associations were observed with plaque erosion after adjusting for covariates.
This is the first autopsy study investigating associations between PRS and atherosclerosis severity at the histopathologic level in subjects with sudden death. Our pathological analysis suggests PRS correlates with plaque burden and features of advanced atherosclerosis and may be useful as a method for CAD risk stratification, especially in younger subjects.
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