BACKGROUND-Brugada syndrome (BrS) is a common heritable channelopathy. Mutations in the SCN5A-encoded sodium channel (BrS1) culminate in the most common genotype.

BACKGROUND Long QT syndrome (LQTS) is a potentially lethal, highly treatable cardiac channelopathy for which genetic testing has matured from discovery to translation and now clinical implementation. OBJECTIVES Here we examine the spectrum and prevalence of mutations found in the first 2,500 unrelated cases referred for the FAMILION® LQTS clinical genetic test. METHODS Retrospective analysis of the first 2,500 cases (1,515 female patients, average age at testing 23 ± 17 years, range 0 to 90 years) scanned for mutations in 5 of the LQTS-susceptibility genes: KCNQ1 (LQT1), KCNH2 (LQT2), SCN5A (LQT3), KCNE1 (LQT5), and KCNE2 (LQT6). RESULTS Overall, 903 referral cases (36%) hosted a possible LQTS-causing mutation that was absent in >2,600 reference alleles; 821 (91%) of the mutation-positive cases had single genotypes, whereas the remaining 82 patients (9%) had >1 mutation in ≥1 gene, including 52 cases that were compound heterozygous with mutations in >1 gene. Of the 562 distinct mutations, 394 (70%) were missense, 428 (76%) were seen once, and 336 (60%) are novel, including 92 of 199 in KCNQ1, 159 of 226 in KCNH2, and 70 of 110 in SCN5A. CONCLUSION This cohort increases the publicly available compendium of putative LQTS-associated mutations by >50%, and approximately one-third of the most recently detected mutations continue to be novel. Although control population data suggest that the great majority of these mutations are pathogenic, expert interpretation of genetic test results will remain critical for effective clinical use of LQTS genetic test results.

Objectives Identify SNPs associated with mild statin-induced side effects. Background Statin-induced side effects can interfere with therapy. SNPs in cytochrome P450 enzymes impair statin metabolism; the reduced function SLCO1B1*5 allele impairs statin clearance and is associated with simvastatin-induced myopathy with CK elevation. Methods The STRENGTH study was a pharmacogenetics study of statin efficacy and safety. Subjects (n=509) were randomized to atorvastatin 10mg, simvastatin 20mg, or pravastatin 10mg followed by 80mg, 80mg, and 40mg, respectively. We defined a composite adverse event (CAE) as discontinuation for any side effect, myalgia, or CK>3× baseline during follow-up. We sequenced CYP2D6, CYP2C8, CYP2C9, CYP3A4, and SLCO1B1 and tested seven reduced function alleles for association with the CAE. Results The CAE occurred in 99 subjects (54 discontinuations, 49 myalgias, and nine CK elevations). Sex was associated with CAE (percent female in CAE vs. no CAE groups, 66% vs. 50%, p<0.01). SLCO1B1*5 was associated with CAE (percent with ≥ 1 allele in CAE vs. no CAE groups, 37% vs. 25%, p=0.03) and those with CAE with no significant CK elevation (p≤ 0.03). Furthermore, there was evidence for a gene-dose effect (percent with CAE in those with 0, 1, or 2 alleles: 19%, 27%, and 50%, trend p = 0.01). Finally, the CAE risk appeared to be highest in those carriers assigned to simvastatin. Conclusions SLCO1B1*5 genotype and female sex were associated mild statin-induced side effects. These findings expand the results of a recent genome wide association study of statin myopathy with CK > 3 times normal to milder, statin-induced, muscle side effects.

No abstract

This study is the first to comprehensively evaluate genetic variation in healthy controls for the ARVC susceptibility genes. Radical mutations are high-probability ARVC-associated mutations, whereas rare missense mutations should be interpreted in the context of race and ethnicity, mutation location, and sequence conservation.

Background-Genetic testing for long-QT syndrome (LQTS) has diagnostic, prognostic, and therapeutic implications.Hundreds of causative mutations in 12 known LQTS-susceptibility genes have been identified. Genetic testing that includes the 3 most commonly mutated genes is available clinically. Distinguishing pathogenic mutations from innocuous rare variants is critical to the interpretation of test results. We sought to quantify the value of mutation type and gene/protein region in determining the probability of pathogenicity for mutations. Methods and Results-Type, frequency, and location of mutations across KCNQ1 (LQT1), KCNH2 (LQT2), and SCN5A (LQT3) were compared between 388 unrelated "definite" (clinical diagnostic score Ն4 and/or QTc Ն480 ms) cases of LQTS and Ͼ1300 healthy controls for each gene. From these data, estimated predictive values (percent of mutations found in definite cases that would cause LQTS) were determined according to mutation type and location. Mutations were 10 times more common in cases than controls (0.58 per case versus 0.06 per control). Missense mutations were the most common, accounting for 78%, 67%, and 89% of mutations in KCNQ1, KCNH2, and SCN5A in cases and Ͼ95% in controls. Nonmissense mutations have an estimated predictive value Ͼ99% regardless of location. In contrast, location appears to be critical for characterizing missense mutations. Relative frequency of missense mutations between cases and controls ranged from Ϸ1:1 in the SCN5A interdomain linker to infinity in the pore, transmembrane, and linker in KCNH2. These correspond to estimated predictive values ranging from 0% in the interdomain linker of SCN5A to 100% in the transmembrane/linker/pore regions of KCNH2. The estimated predictive value is also high in the linker, pore, transmembrane, and C terminus of KCNQ1 and the transmembrane/linker of SCN5A. Conclusions-Distinguishing pathogenic mutations from rare variants is of critical importance in the interpretation of genetic testing in LQTS. Mutation type, mutation location, and ethnic-specific background rates are critical factors in predicting the pathogenicity of novel mutations. Novel mutations in low-estimated predictive value regions such as the interdomain linker of SCN5A should be viewed as variants of uncertain significance and prompt further investigation to clarify the likelihood of disease causation. However, mutations in regions such as the transmembrane, linker, and pore of KCNQ1 and KCNH2 may be defined confidently as high-probability LQTS-causing mutations. These findings will have implications for other genetic disorders involving mutational analysis. (Circulation. 2009;120:1752-1760.)

BACKGROUND-The prevalence of atrial fibrillation (AF) in the young (age <50 years) is 0.1%, or 1:1,000 persons. Mutations in KCNQ1-, KCNH2-, and KCNA5-encoded potassium channels and SCN5A-encoded sodium channels have been reported in familial AF. A mechanism of atrial torsade has been suggested to occur in patients with congenital long QT syndrome (LQTS).

Objective-To determine whether maternal/fetal SNPs in candidate genes are associated with preterm prelabor rupture of membranes (pPROM).Study Design-A case-control study was conducted in patients with pPROM (225 mothers and 155 fetuses) and 599 mothers and 628 fetuses with a normal pregnancy; 190 candidate genes and 775 SNPs were studied. Single locus/haplotype association analyses were performed; FDR was used to correct for multiple testing (q*=0.15)].Results-1) A SNP in TIMP2 in mothers was significantly associated with pPROM(OR=2.12 95% CI [1.47-3.07], p = 0.000068), and this association remained significant after correction for multiple comparisons; 2) Haplotypes for COL4A3 in the mother were associated with pPROM (global p = 0.003); 3) Multilocus analysis identified a three locus model, which included maternal SNPs in COL1A2, DEFA5, and EDN1.Conclusion-DNA variants in a maternal gene involved in extracellular matrix metabolism doubled the risk of pPROM.