Transcriptional Dysregulation Underlies Both Monogenic Arrhythmia Syndrome and Common Modifiers of Cardiac Repolarization.

BACKGROUND: Brugada syndrome (BrS) is an inherited arrhythmia syndrome caused by loss-of-function variants in the cardiac sodium channel gene SCN5A (sodium voltage-gated channel alpha subunit 5) in ≈20% of subjects. We identified a family with 4 individuals diagnosed with BrS harboring the rare G145R missense variant in the cardiac transcription factor TBX5 (T-box transcription factor 5) and no SCN5A variant. METHODS: We generated induced pluripotent stem cells (iPSCs) from 2 members of a family carrying TBX5-G145R and diagnosed with Brugada syndrome. After differentiation to iPSC-derived cardiomyocytes (iPSC-CMs), electrophysiologic characteristics were assessed by voltage- and current-clamp experiments (n=9 to 21 cells per group) and transcriptional differences by RNA sequencing (n=3 samples per group), and compared with iPSC-CMs in which G145R was corrected by CRISPR/Cas9 approaches. The role of platelet-derived growth factor (PDGF)/phosphoinositide 3-kinase (PI3K) pathway was elucidated by small molecule perturbation. The rate-corrected QT (QTc) interval association with serum PDGF was tested in the Framingham Heart Study cohort (n=1893 individuals). RESULTS: TBX5-G145R reduced transcriptional activity and caused multiple electrophysiologic abnormalities, including decreased peak and enhanced "late" cardiac sodium current (INa), which were entirely corrected by editing G145R to wild-type. Transcriptional profiling and functional assays in genome-unedited and -edited iPSC-CMs showed direct SCN5A down-regulation caused decreased peak INa, and that reduced PDGF receptor (PDGFRA [platelet-derived growth factor receptor α]) expression and blunted signal transduction to PI3K was implicated in enhanced late INa. Tbx5 regulation of the PDGF axis increased arrhythmia risk due to disruption of PDGF signaling and was conserved in murine model systems. PDGF receptor blockade markedly prolonged normal iPSC-CM action potentials and plasma levels of PDGF in the Framingham Heart Study were inversely correlated with the QTc interval (P<0.001). CONCLUSIONS: These results not only establish decreased SCN5A transcription by the TBX5 variant as a cause of BrS, but also reveal a new general transcriptional mechanism of arrhythmogenesis of enhanced late sodium current caused by reduced PDGF receptor-mediated PI3K signaling.

High-Throughput Reclassification of SCN5A Variants.

Partial or complete loss-of-function variants in SCN5A are the most common genetic cause of the arrhythmia disorder Brugada syndrome (BrS1). However, the pathogenicity of SCN5A variants is often unknown or disputed; 80% of the 1,390 SCN5A missense variants observed in at least one individual to date are variants of uncertain significance (VUSs). The designation of VUS is a barrier to the use of sequence data in clinical care. We selected 83 variants: 10 previously studied control variants, 10 suspected benign variants, and 63 suspected Brugada syndrome-associated variants, selected on the basis of their frequency in the general population and in individuals with Brugada syndrome. We used high-throughput automated patch clamping to study the function of the 83 variants, with the goal of reclassifying variants with functional data. The ten previously studied controls had functional properties concordant with published manual patch clamp data. All 10 suspected benign variants had wild-type-like function. 22 suspected BrS variants had loss of channel function (<10% normalized peak current) and 22 variants had partial loss of function (10%-50% normalized peak current). The previously unstudied variants were initially classified as likely benign (n = 2), likely pathogenic (n = 10), or VUSs (n = 61). After the patch clamp studies, 16 variants were benign/likely benign, 45 were pathogenic/likely pathogenic, and only 12 were still VUSs. Structural modeling identified likely mechanisms for loss of function including altered thermostability and disruptions to alpha helices, disulfide bonds, or the permeation pore. High-throughput patch clamping enabled reclassification of the majority of tested VUSs in SCN5A.

Humoral and cellular immune responses to the SARS-CoV-2 BNT162b2 vaccine among a cohort of solid organ transplant recipients and healthy controls.

BACKGROUND: Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection is associated with increased morbidity and mortality in solid organ transplant (SOT) recipients. Despite exclusion from SARS-CoV-2 vaccine clinical trials, these individuals were identified as high-risk and prioritized for vaccination in public health guidelines. METHODS: We prospectively evaluated humoral and cellular immune responses to two doses of the SARS-CoV-2 mRNA vaccine, BNT162b2, in 56 SOT recipients and 26 healthy controls (HCs). Blood specimens collected from participants prior to each dose and following the second dose were tested for SARS-CoV-2-specific antibodies, as well as CD4+ and CD8+ T-cell responses. RESULTS: SOT recipients demonstrated lower mean anti-SARS-CoV-2 antibody levels compared to HCs after each dose, and only 21.6% achieved an antibody response after the second dose within the range of HC responses. Similarly, the percentage of responsive CD4+ and CD8+ T cells in SOT recipients was lower than in HCs. While most HCs showed notable humoral and cellular responses, responses were less concordant in SOT recipients, with some showing evidence of either humoral or cellular response, but not both. CONCLUSION: Humoral and cellular immune responses to the BNT162b2 vaccine are markedly reduced in SOT recipients as compared to HCs, suggesting that SOT recipients may benefit from more tailored regimens such as higher dose and/or additional vaccinations.

Electrophysiologic and molecular mechanisms of a frameshift NPPA mutation linked with familial atrial fibrillation.

A frameshift (fs) mutation in the natriuretic peptide precursor A (NPPA) gene, encoding a mutant atrial natriuretic peptide (Mut-ANP), has been linked with familial atrial fibrillation (AF) but the underlying mechanisms by which the mutation causes AF remain unclear. We engineered 2 transgenic (TG) mouse lines expressing the wild-type (WT)-NPPA gene (H-WT-NPPA) and the human fs-Mut-NPPA gene (H-fsMut-NPPA) to test the hypothesis that mice overexpressing the human NPPA mutation are more susceptible to AF and elucidate the underlying electrophysiologic and molecular mechanisms. Transthoracic echocardiography and surface electrocardiography (ECG) were performed in H-fsMut-NPPA, H-WT-NPPA, and Non-TG mice. Invasive electrophysiology, immunohistochemistry, Western blotting and patch clamping of membrane potentials were performed. To examine the role of the Mut-ANP in ion channel remodeling, we measured plasma cyclic guanosine monophosphate (cGMP) and cyclic adenosine monophosphate (cAMP) levels and protein kinase A (PKA) activity in the 3 groups of mice. In H-fsMut-NPPA mice mean arterial pressure (MAP) was reduced when compared to H-WT-NPPA and Non-TG mice. Furthermore, injection of synthetic fs-Mut-ANP lowered the MAP in H-WT-NPPA and Non-TG mice while synthetic WT-ANP had no effect on MAP in the 3 groups of mice. ECG characterization revealed significantly prolonged QRS duration in H-fsMut-NPPA mice when compared to the other two groups. Trans-Esophageal (TE) atrial pacing of H-fsMut-NPPA mice showed increased AF burden and AF episodes when compared with H-WT-NPPA or Non-TG mice. The cardiac Na+ (NaV1.5) and Ca2+ (CaV1.2/CaV1.3) channel expression and currents (INa, ICaL) and action potential durations (APD90/APD50/APD20) were significantly reduced in H-fsMut-NPPA mice while the rectifier K+ channel current (IKs) was markedly increased when compared to the other 2 groups of mice. In addition, plasma cGMP levels were only increased in H-fsMut-NPPA mice with a corresponding reduction in plasma cAMP levels and PKA activity. In summary, we showed that mice overexpressing an AF-linked NPPA mutation are more prone to develop AF and this risk is mediated in part by remodeling of the cardiac Na+, Ca2+ and K+ channels creating an electrophysiologic substrate for reentrant AF.

Genome-wide association and pathway analysis of left ventricular function after anthracycline exposure in adults.

BACKGROUND: Anthracyclines are important chemotherapeutic agents, but their use is limited by cardiotoxicity. Candidate gene and genome-wide studies have identified putative risk loci for overt cardiotoxicity and heart failure, but there has been no comprehensive assessment of genomic variation influencing the intermediate phenotype of anthracycline-related changes in left ventricular (LV) function. The purpose of this study was to identify genetic factors influencing changes in LV function after anthracycline chemotherapy. METHODS: We conducted a genome-wide association study (GWAS) of change in LV function after anthracycline exposure in 385 patients identified from BioVU, a resource linking DNA samples to de-identified electronic medical record data. Variants with P values less than 1×10 were independently tested for replication in a cohort of 181 anthracycline-exposed patients from a prospective clinical trial. Pathway analysis was performed to assess combined effects of multiple genetic variants. RESULTS: Both cohorts were middle-aged adults of predominantly European descent. Among 11 candidate loci identified in discovery GWAS, one single nucleotide polymorphism near PR domain containing 2, with ZNF domain (PRDM2), rs7542939, had a combined P value of 6.5×10 in meta-analysis. Eighteen Kyoto Encyclopedia of Gene and Genomes pathways showed strong enrichment for variants associated with the primary outcome. Identified pathways related to DNA repair, cellular metabolism, and cardiac remodeling. CONCLUSION: Using genome-wide association we identified a novel candidate susceptibility locus near PRDM2. Variation in genes belonging to pathways related to DNA repair, metabolism, and cardiac remodeling may influence changes in LV function after anthracycline exposure.

Pre-existing Psychiatric Illness is Associated With Increased Risk of Recurrent Takotsubo Cardiomyopathy.

BACKGROUND: The increased prevalence of psychiatric illness among patients with takotsubo cardiomyopathy (TC) has been previously described. OBJECTIVES: We sought to assess the effect of pre-existing psychiatric illness on clinical outcomes following the diagnosis of TC. METHODS: Adults diagnosed with TC at Vanderbilt University Medical Center between 1999 and 2015 were included in the study. Medical records were retrospectively reviewed to identify any pre-existing mood, anxiety, or schizophrenia-spectrum illness before TC presentation. Multivariable logistic regression was used to test for independent association of pre-existing psychiatric illness with 30-day mortality and recurrent TC; Cox proportional hazard analysis was used to evaluate for association with long-term mortality. RESULTS: Among 306 patients diagnosed with TC during the study period, 114 (37%) had a pre-existing psychiatric illness. In all, 43 (14%) and 88 (29%) patients died within 30 days of index diagnosis and as of last medical record review, respectively. Of the 269 who survived their index hospitalization, 19 (7%) had a confirmed recurrent episode of TC. In multivariable analyses, pre-existing psychiatric illness was not associated with increased 30-day (P = 0.320) or long-term (P = 0.621) mortality. Pre-existing psychiatric illness was associated with higher risk of recurrent TC (odds ratio = 7.44, 95% CI: 2.30-24.01, P < 0.001). CONCLUSIONS: Pre-existing psychiatric illness was associated with an increased risk of recurrent TC. No significant association was noted between pre-existing psychiatric illness and survival.

Whole-exome sequencing in familial atrial fibrillation.

AIMS: Positional cloning and candidate gene approaches have shown that atrial fibrillation (AF) is a complex disease with familial aggregation. Here, we employed whole-exome sequencing (WES) in AF kindreds to identify variants associated with familial AF. METHODS AND RESULTS: WES was performed on 18 individuals in six modestly sized familial AF kindreds. After filtering very rare variants by multiple metrics, we identified 39 very rare and potentially pathogenic variants [minor allele frequency (MAF) ≤0.04%] in genes not previously associated with AF. Despite stringent filtering >1 very rare variants in the 5/6 of the kindreds were identified, whereas no plausible variants contributing to familial AF were found in 1/6 of the kindreds. Two candidate AF variants in the calcium channel subunit genes (CACNB2 and CACNA2D4) were identified in two separate families using expression data and predicted function. CONCLUSION: By coupling family data with exome sequencing, we identified multiple very rare potentially pathogenic variants in five of six families, suggestive of a complex disease mechanism, whereas none were identified in the remaining AF pedigree. This study highlights some important limitations and challenges associated with performing WES in AF including the importance of having large well-curated multi-generational pedigrees, the issue of potential AF misclassification, and limitations of WES technology when applied to a complex disease.

Common SCN10A variants modulate PR interval and heart rate response during atrial fibrillation.

AIMS: SCN10A encodes the sodium channel Nav1.8 implicated by genome-wide association studies as a modulator of atrioventricular conduction (PR interval). In a cohort of patients with atrial fibrillation (AF), we examined whether there was an association between common variants in SCN10A and both the PR interval during normal sinus rhythm and the heart rate response during AF. METHODS AND RESULTS: Patients prospectively enrolled in the Vanderbilt AF registry with electrocardiograms in normal sinus rhythm and/or AF within 1 year of enrollment were genotyped for two common SCN10A variants rs6795970 and rs12632942. Both variants were associated with the PR interval duration in a gene-dose effect on unadjusted analysis; after adjustment for the covariates age, gender, body mass index, hypertension, congestive heart failure, and medication usage, the association remained for rs6795970 only (P = 0.012, partial R(2) = 0.0139). On unadjusted analysis, heart rate response during AF was associated with rs6795970 (P = 0.035, partial R(2) = 0.015), but not with rs12632942 (P = 0.89), and neither association was significant after adjustment for covariates. CONCLUSION: The common variant rs6795970 in SCN10A is associated with the PR interval duration among healthy patients and those with AF. In addition, this single nucleotide polymorphism trended towards an association with heart rate response during AF indicating the importance of this common SCN10A polymorphism as a marker of atrioventricular conduction.

A KCNJ8 mutation associated with early repolarization and atrial fibrillation.

AIM: The Kir 6.1 K(atp) channel is believed to play an important role in ventricular repolarization as determined from both functional and genetic studies of the potassium inwardly-rectifying channel, subfamily J, member 8 (KCNJ8)-S422L missense mutation in patients with J-wave syndromes. Although Kir6.1 is also present in atrial tissue, it is unknown whether this channel modulates atrial repolarization and hence whether the S422L mutation portends a greater risk of atrial arrhythmias. This study sought to examine whether there was an increased frequency of the KCNJ8-S422L mutation among patients with atrial fibrillation (AF) and early repolarization (ER) as a possible novel susceptibility gene for AF. METHODS AND RESULTS: A total of 325 lone AF probands were identified from the Vanderbilt AF Registry, a collection of clinical data and DNA from consented, consecutively enrolled participants. The coding regions of KCNJ8 were sequenced, and the patient's presenting electrocardiogram (ECG) was reviewed by two independent physicians for ER abnormalities. The KCNJ8-S422L mutation was identified in two AF probands while no other candidate gene variants were identified in these cases. Twenty-two (7%) patients were found to have ER on the ECG, including the two probands carrying the S422L variant. In one small AF kindred, the S422L variant co-segregated with AF and ER. CONCLUSIONS: The KCNJ8-S422L variant is associated with both increased AF susceptibility and ER indicating a role for Kir 6.1 K(atp) channel in both ventricular and atrial repolarization.

A new locus for autosomal dominant generalized epilepsy associated with mild mental retardation on chromosome 3p.

PURPOSE: Generalized epilepsies are clinically and genetically heterogeneous syndromes. Idiopathic generalized epilepsy (IGE), which has a strong genetic background, is not associated with any additional clinical features, such as mental retardation (MR). Herein we report results of linkage analysis in a large family with autosomal dominant (AD) generalized epilepsy associated with MR. METHODS: We identified a four-generation kindred with several affected members with generalized epilepsy without any evidence for secondary causes. Electroencephalography (EEG) studies and magnetic resonance imaging (MRI) results were reviewed when available. We performed a genome-wide linkage analysis. KEY FINDINGS: Fourteen individuals were classified as affected and an additional three were considered as nonpenetrant obligatory carriers. Thirteen affected individual had a history of generalized tonic-clonic seizures, and absence seizures were reported in nine affected individuals. There was no history of preceding febrile seizures. MR was present in nine affected individuals with epilepsy but the other affected individuals had normal intelligence. Neuroimaging did not reveal any structural abnormalities and EEG studies were consistent with IGE rather than symptomatic generalized epilepsy. Genetic analysis detected a group of markers with logarithmic (base 10) of odds (LOD) score >3 on chromosome 3p spanning a 5.5 Mbp region. Sequencing of several candidate genes, including dynein light chain-A, golgin subfamily a4, leucine rich repeat (in FLII) interacting gene, serine/threonine-protein kinase DCAMKL3 (doublecortin- like and CAM kinase-like 3), laforin (EPM2A) interacting protein 1 (EPM2AIP1, programmed cell death 6 interacting protein, and CLIP-associating protein 2 (cytoplasmic linker-associated protein 2) (hOrbit2) genes did not identify the disease-causing mutations. SIGNIFICANCE: We report the identification of a genetic locus for generalized epilepsy associated with MR on chromosome 3p. Affected individuals have a form of genetic epilepsy with generalized seizures variably associated with MR. Despite the presence of MR in several affected patients, epilepsy phenotype was not fully consistent with symptomatic epilepsy and suggests a biologic continuum between symptomatic epilepsies and IGE.

Augmented potassium current is a shared phenotype for two genetic defects associated with familial atrial fibrillation.

Mutations in multiple genes have been implicated in familial atrial fibrillation (AF), but the underlying mechanisms, and thus implications for therapy, remain ill-defined. Among 231 participants in the Vanderbilt AF Registry, we found a mutation in KCNQ1 (encoding the alpha-subunit of slow delayed rectifier potassium current [I(Ks)]) and separately a mutation in natriuretic peptide precursor A (NPPA) gene (encoding atrial natriuretic peptide, ANP), both segregating with early onset lone AF in different kindreds. The functional effects of these mutations yielded strikingly similar I(Ks) "gain-of-function." In Chinese Hamster Ovary (CHO) cells, coexpression of mutant KCNQ1 with its ancillary subunit KCNE1 generated approximately 3-fold larger currents that activated much faster than wild-type (WT)-I(Ks). Application of the WT NPPA peptide fragment produced similar changes in WT-I(Ks), and these were exaggerated with the mutant NPPA S64R peptide fragment. Anantin, a competitive ANP receptor antagonist, completely inhibited the changes in I(Ks) gating observed with NPPA S64R. Computational simulations identified accelerated transitions into open states as the mechanism for variant I(Ks) gating. Incorporating these I(Ks) changes into computed human atrial action potentials (AP) resulted in 37% shortening (120 vs. 192 ms at 300 ms cycle length), reflecting loss of the phase II dome which is dependent on L-type calcium channel current. We found striking functional similarities due to mutations in KCNQ1 and NPPA genes which led to I(Ks) "gain-of-function", atrial AP shortening, and consequently altered calcium current as a common mechanism between diverse familial AF syndromes.

Initial changes in peak aortic jet velocity and mean gradient predict progression to severe aortic stenosis.

BACKGROUND: There is significant interindividual variability in the rate of aortic stenosis (AS) progression that is not accounted for in the current surveillance algorithms. We sought to examine the association between changes in peak aortic jet velocity (Vmax) and mean gradient (MG) among patients with mild or moderate AS and risk of progression to severe disease. METHODS: Adult subjects referred for echocardiography at a single academic referral center with a diagnosis of mild or moderate AS and ≥2 additional surveillance echocardiograms were included in the study. Changes in Vmax and MG between the first two echocardiograms were indexed to time and tested for association with future progression to severe AS. RESULTS: Among three hundred and sixty-four subjects, the median time between first and second echocardiograms was 1.3 years and initial changes in Vmax and MG indexed to time were +0.16 m/s per year and +1.44 mmHg per year, respectively. Fifty-three (15%) and fifty-six (15%) subjects progressed to severe AS defined by Vmax and MG, respectively. In multivariable logistic regression, initial increase in Vmax (OR = 4.19, 95% CI 1.93-9.10, p < 0.001) and initial increase in MG (OR = 1.12, 95% CI 1.06-1.18, p < 0.001) were associated with progression to severe AS. CONCLUSIONS: Initial changes in Vmax and MG among patients with mild or moderate AS are strongly associated with risk of progression to severe AS and may help guide individualized surveillance strategies.

High-throughput discovery of trafficking-deficient variants in the cardiac potassium channel KV11.1.

BACKGROUND: KCHN2 encodes the KV11.1 potassium channel responsible for IKr, a major repolarization current during the cardiomyocyte action potential. Variants in KCNH2 that lead to decreased IKr have been associated with long QT syndrome type 2 (LQT2). The mechanism of LQT2 is most often induced loss of KV11.1 trafficking to the cell surface. Accurately discriminating between variants with normal and abnormal trafficking would aid in understanding the deleterious nature of these variants; however, the volume of reported nonsynonymous KCNH2 variants precludes the use of conventional methods for functional study. OBJECTIVE: The purpose of this study was to report a high-throughput, multiplexed screening method for KCNH2 genetic variants capable of measuring the cell surface abundance of hundreds of missense variants in the resulting KV11.1 channel. METHODS: We developed a method to quantitate KV11.1 variant trafficking on a pilot region of 11 residues in the S5 helix. RESULTS: We generated trafficking scores for 220 of 231 missense variants in the pilot region. For 5 of 5 variants, high-throughput trafficking scores validated when tested in single variant flow cytometry and confocal microscopy experiments. We further explored these results with planar patch electrophysiology and found that loss-of-trafficking variants do not produce IKr. Conversely, but expectedly, some variants that traffic normally were still functionally compromised. CONCLUSION: We describe a new method for detecting KV11.1 trafficking-deficient variants in a multiplexed assay. This new method accurately generated trafficking data for variants in KV11.1 and is extendable both to all residues in KV11.1 and to other cell surface proteins.

Reappraisal of the role of the DRD3 gene in essential tremor.

OBJECTIVES: Analyze the distribution of polymorphism in the dopamine receptor D3 (DRD3) gene, which was previously reported as a susceptibility risk for essential tremor (ET), in a large cohort of ET. METHODS: The role of 312G>A DRD3 polymorphism was analyzed using linkage analysis, association study and transmission disequilibrium test in a group of 433 ET patients, and two unrelated control groups with 121 and 151 individuals. RESULTS: Allelic frequencies of glycine and serine forms of the DRD3 gene did not differ between patients and both control groups, and were in Hardy-Weinberg equilibrium. Linkage analysis identified obligatory recombinants in every large pedigree, even in those with relatively high frequency of glycine allele, thus excluding the linkage to this locus. Both alleles were transmitted with an equal likelihood to affected offspring. We also failed to replicate the relationship between glycine homozygosity and an earlier age of onset or more severe tremor course. CONCLUSIONS: Our comprehensive genetic analysis in a large ET cohort strongly argues against the role of the DRD3 gene in ET pathogenesis.

Infantile onset of hereditary spastic paraplegia poorly predicts the genotype.

Age of symptom onset of hereditary spastic paraplegia varies from infancy to the eighth decade. Infantile onset of hereditary spastic paraplegia without a positive family history may cause difficulties in reaching the correct diagnosis and misdiagnosis as a diplegic form of cerebral palsy is particularly common. Infantile onset of hereditary spastic paraplegia caused by mutations in the spastin gene (SPAST) is very rare and previously was mostly associated with codominant mutations in this gene. We present a kindred with infantile onset of spastic paraplegia in three successive generations caused by confirmed de novo novel mutation 1537G>A (G471D) in SPAST. Several family members were previously diagnosed as having cerebral palsy. Infantile onset of hereditary spastic paraplegia may be caused by mutations in multiple genes, and this phenotype does not reliably predict the genotype. Pediatric neurologists need to be aware of relatively frequent de novo mutations in hereditary spastic paraplegia genes and a possibility that this condition presents in infancy without a positive family history.

Prognostic Significance of Early Rehospitalization After Takotsubo Cardiomyopathy.

Short-term complications, particularly rehospitalization, after a diagnosis of takotsubo cardiomyopathy (TTC) are poorly described. We sought to characterize the rates, causes, clinical associations, and prognostic implications of early rehospitalization in this patient population. We performed a retrospective observational study of all adult subjects diagnosed with TTC at an academic tertiary care hospital from 2005 to 2015. The primary outcome was rehospitalization within 30 days of index discharge. Multivariable logistic regression was used to test for association between clinical variables and rehospitalization. Association between rehospitalization and survival after index discharge was assessed as a secondary outcome using a multivariable Cox proportional hazard model. Two hundred sixty-three subjects met the inclusion criteria for the study. There were 38 rehospitalizations among 32 subjects (12%). Ninety-five percent of rehospitalizations were due to nonheart failure causes, and 76% were related to noncardiovascular complaints. In multivariable analysis, recent hospitalization before TTC diagnosis and increased length of index hospitalization were associated with greater risk of rehospitalization (odds ratio 4.58, 95% CI 1.97 to 10.65, p <0.001 and odds ratio 1.05, 95% CI 1.01 to 1.10, p = 0.026, respectively). Early rehospitalization after TTC was associated with decreased survival (hazard ratio 3.17, 95% CI 1.53 to 6.56, p = 0.002).

Mutations in GABRA1, GABRA5, GABRG2 and GABRD receptor genes are not a major factor in the pathogenesis of familial focal epilepsy preceded by febrile seizures.

GABA(A) receptors mutations have been reported in few epilepsy families with febrile seizures (FS) followed by generalized epilepsy. It is not known if such mutations may underlie FS followed by partial epilepsy, which is a more common type of epilepsy. We searched for disease-causing mutations in the genes of the alpha1, alpha5, gamma2 and delta subunits of the GABA-A receptor that were previously shown to contain epilepsy-causing mutations or epilepsy susceptibility polymorphisms. All coding and untranslated exons of these four GABA(A) subunit genes were screened in 74 unrelated patients with familial partial epilepsy preceded by FS. Most patients had temporal lobe epilepsy (TLE). We did not detect any disease-causing mutations that would be consistent with missense, nonsense or splice site mutations in any of the four analyzed genes. We conclude that these genes are not a major genetic factor in familial TLE preceded by FS.

Mutations in the GABRA1 and EFHC1 genes are rare in familial juvenile myoclonic epilepsy.

Juvenile myoclonic epilepsy (JME), accounting for approximately 25% of idiopathic generalized epilepsies, is genetically heterogeneous. Mutations in the alpha-1 subunit of the GABAA receptor (GABRA1) and EFHC1 genes have been reported in a few families with autosomal dominant (AD) JME. We have investigated the contribution of these two genes to familial JME in our cohort of 54 JME Caucasian families. Syndromic classification of JME was based on previously published criteria. We considered kindreds with at least one affected first-degree relative and the evidence of a vertical transmission as definite AD JME, and families with at least one affected second-degree relative as probable AD JME. We included 33 families meeting criteria for definitive AD JME and 21 that were classified as probable AD JME. None of these families were considered informative enough to analyze candidate loci for JME using linkage analysis. We have systematically screened coding exons of these two genes using temperature gradient capillary electrophoresis. Every heteroduplex with an abnormal mobility was sequenced. No disease-causing mutations in the GABRA1 gene were identified. Analysis of EFHC1 gene found one putative disease-causing mutation R221H that was previously reported as a tandem mutation. Several synonymous and non-synonymous coding polymorphisms were identified but the allelic frequency did not differ between controls and affected individuals. Our data suggests that the majority of familial AD JME is not caused by mutations in the GABRA1 and EFHC1 genes.

Genetic and clinical risk prediction model for postoperative atrial fibrillation.

BACKGROUND: Postoperative atrial fibrillation (PoAF) is common after coronary artery bypass grafting. We previously showed that atrial fibrillation susceptibility single nucleotide polymorphisms (SNPs) at the chromosome 4q25 locus are associated with PoAF. Here, we tested the hypothesis that a combined clinical and genetic model incorporating atrial fibrillation risk SNPs would be superior to a clinical-only model. METHODS AND RESULTS: We developed and externally validated clinical and clinical/genetic risk models for PoAF. The discovery and validation cohorts included 556 and 1164 patients, respectively. Clinical variables previously associated with PoAF and 13 SNPs at loci associated with atrial fibrillation in genome-wide association studies were considered. PoAF occurred in 30% and 29% of patients in the discovery and validation cohorts, respectively. In the discovery cohort, a logistic regression model with clinical factors had good discrimination, with an area under the receiver operator characteristic curve of 0.76. The addition of 10 SNPs to the clinical model did not improve discrimination (area under receiver operator characteristic curve, 0.78; P=0.14 for difference between the 2 models). In the validation cohort, the clinical model had good discrimination (area under the receiver operator characteristic curve, 0.69) and addition of genetic variables resulted in a marginal improvement in discrimination (area under receiver operator characteristic curve, 0.72; P<0.0001). CONCLUSIONS: We developed and validated a model for the prediction of PoAF containing common clinical variables. Addition of atrial fibrillation susceptibility SNPs did not improve model performance. Tools to accurately predict PoAF are needed to risk stratify patients undergoing coronary artery bypass grafting and identify candidates for prophylactic therapies.