Lack of MEF2A mutations in coronary artery disease

Effect of MEF2A and SLC22A3-LPAL2-LPA gene polymorphisms on warfarin sensitivity and responsiveness in Jordanian cardiovascular patients

AIMS

This study aims to investigate the influence of MEF2A and SLC22A3-LPAL2-LPA polymorphisms on cardiovascular disease susceptibility and responsiveness to warfarin medication in Jordanian patients, during the initiation and maintenance phases of treatment.

BACKGROUNDS

Several candidate genes have been reported to be involved in warfarin metabolism and studying such genes may help in finding an accurate way to determine the needed warfarin dose to lower the risk of adverse drug effects, resulting in more safe anticoagulant therapy.

METHODS

The study population included 212 cardiovascular patients and 213 healthy controls. Genotyping of MEF2A and SLC22A3-LPAL2-LPA polymorphisms was conducted to examine their effects on warfarin efficiency and cardiovascular disease susceptibility using PCR-based methods.

RESULTS

One SNP (SLC22A3-LPAL2-LPA rs10455872) has been associated with cardiovascular disease in the Jordanian population, whereas the other SNPs in the MEF2A gene and SLC22A3-LPAL2-LPA gene cluster did not have any significant differences between cardiovascular patients and healthy individuals. Moreover, SLC22A3-LPAL2-LPA rs10455872 was correlated with moderate warfarin sensitivity, the other SNPs examined in the current study have not shown any significant associations with warfarin sensitivity and responsiveness.

CONCLUSION

Our data refer to a lack of correlation between the MEF2A polymorphism and the efficacy of warfarin treatment in both phases of treatment, the initiation, and maintenance phases. However, only rs10455872 SNP was associated with sensitivity to warfarin during the initiation phase. Furthermore, rs3125050 has been found to be associated with the international normalized number treatment outcomes in the maintenance phase.

Diagnosis of Chromosome 15q-Terminal Deletion Syndrome through Elevated Fasting Serum Growth Hormone Levels

Chromosome 15q26-qter deletion syndrome is a rare disease that causes prenatal and postnatal growth retardation, microcephaly, developmental delay, and congenital heart diseases, mainly due to haploinsufficiency of IGF1R. In addition, patients with pathogenic variants of the IGF1R show similar symptoms. We report the case of a 5-month-old girl with prenatal and postnatal growth retardation, microcephaly, and congenital heart disease. At 5 months of age, her length was 54.7 cm (−4.3 SD), her weight was 4.4 kg (−3.1 SD), and her head circumference was 37.4 cm (−2.8 SD), thus presenting severe growth retardation. Repeated pre-feeding serum GH levels were abnormally high (26.1–85.5 ng/mL), and IGF-1 levels (+0.16 to +1.2 SD) were relatively high. The 15q sub-telomere fluorescence in situ hybridization analysis revealed a heterozygous deletion in the 15q terminal region. Whole-genome single nucleotide polymorphism microarray analysis showed a terminal deletion of 6.4 Mb on 15q26.2q26.3. This is the first report showing that fasting GH levels are high in early infancy in patients with IGF1R abnormalities. In addition to relatively high IGF-1 levels, elevated fasting GH levels in early infancy may contribute to the diagnosis of IGF1R abnormalities.

MEF2A Is the Trigger of Resveratrol Exerting Protection on Vascular Endothelial Cell

Both resveratrol and myocyte enhancer factor 2A (MEF2A) may protect vascular endothelial cell (VEC) through activating the expression of SIRT1. However, the relationship between resveratrol and MEF2A is unclear. We aimed to investigate the deeper mechanism of resveratrol in protecting vascular endothelial cells and whether MEF2A plays a key role in the protective function of resveratrol. Human umbilical vein endothelial cell (HUVEC) was used for in vitro study, and small interfere RNA was used for silencing MEF2A. Silencing MEF2A in the vascular endothelium (VE) of ApoE^−/− mice was performed by tail injection with adeno associated virus expressing si-mef2a-shRNA. The results showed that treatment of HUVEC with resveratrol significantly up-regulated MEF2A, and prevented H₂O₂-induced but not siRNA-induced down-regulation of MEF2A. Under various experimental conditions, the expression of SIRT1 changed with the level of MEF2A. Resveratrol could rescue from cell apoptosis, reduction of cell proliferation and viability induced by H₂O₂, but could not prevent against that caused by silencing MEF2A with siRNA. Silencing MEF2A in VE of apoE^−/− mice decreased the expression of SIRT1, increased the plasma LDL-c, and abrogated the function of resveratrol on reducing triglyceride. Impaired integrity of VE and aggravated atherosclerotic lesion were observed in MEF2A silenced mice through immunofluorescence and oil red O staining, respectively. In conclusion, resveratrol enhances MEF2A expression, and the upregulation of MEF2A is required for the endothelial protective benefits of resveratrol in vitro via activating SIRT1. Our work has also explored the in vivo relevance of this signaling pathway in experimental models of atherosclerosis and lipid dysregulation, setting the stage for more comprehensive phenotyping in vivo and further defining the molecular mechanisms.

Myocyte Enhancer Factor 2A Plays a Central Role in the Regulatory Networks of Cellular Physiopathology

Cell regulatory networks are the determinants of cellular homeostasis. Any alteration to these networks results in the disturbance of cellular homeostasis and induces cells towards different fates. Myocyte enhancer factor 2A (MEF2A) is one of four members of the MEF2 family of transcription factors (MEF2A-D). MEF2A is highly expressed in all tissues and is involved in many cell regulatory networks including growth, differentiation, survival and death. It is also necessary for heart development, myogenesis, neuronal development and differentiation. In addition, many other important functions of MEF2A have been reported. Recent studies have shown that MEF2A can regulate different, and sometimes even mutually exclusive cellular events. How MEF2A regulates opposing cellular life processes is an interesting topic and worthy of further exploration. Here, we reviewed almost all MEF2A research papers published in English and summarized them into three main sections: 1) the association of genetic variants in MEF2A with cardiovascular disease, 2) the physiopathological functions of MEF2A, and 3) the regulation of MEF2A activity and its regulatory targets. In summary, multiple regulatory patterns for MEF2A activity and a variety of co-factors cause its transcriptional activity to switch to different target genes, thereby regulating opposing cell life processes. The association of MEF2A with numerous signaling molecules establishes a central role for MEF2A in the regulatory network of cellular physiopathology.

A Genomic Approach to Characterize the Vulnerable Patient – a Clinical Update

Atherosclerosis is the elemental precondition for any cardiovascular disease and the predominant cause of ischemic heart disease that often leads to myocardial infarction. Systemic risk factors play an important role in the starting and progression of atherosclerosis. The complexity of the disease is caused by its multifactorial origin. Besides the traditional risk factors, genetic predisposition is also a strong risk factor. Many studies have intensively researched cardioprotective drugs, which can relieve myocardial ischemia and reperfusion injury, thereby reducing infarct size. A better understanding of abnormal epigenetic pathways in the myocardial pathology may result in new treatment options. Individualized therapy based on genome sequencing is important for an effective future medical treatment. Studies based on multiomics help to better understand the pathophysiological mechanism of several diseases at a molecular level. Epigenomic, transcriptomic, proteomic, and metabolomic research may be essential in detecting the pathological phenotype of myocardial ischemia and ischemic heart failure.

Variants in MEF2A gene in relation with coronary artery disease in Saudi population

This study investigated the association of variants in myocyte enhancer factor 2A (MEF2A) gene with coronary artery disease (CAD) via case control study on Saudi population. Several studies have indicated a high expression of MEF2A in the human coronary endothelium. The entire (exon 11 putative susceptibility exon) of MEF2A gene was sequenced using direct DNA sequencing method in 120 sporadic patients and 100 controls. Total number of variants were identified and crude odds ratio (OR) with 95% confidence interval (CI) was calculated. In total, three variants were identified, namely, CAG repeats, AGC deletion, and SNP rs: 325400. No significant link was observed between the common (CAG) _n polymorphism, AGC deletion, and CAD risk as reported in other populations, but interestingly, rs325400 (G1323T) in Saudis was found to be associated with the CAD with odds ratio 2.0102 (CI = 1.3405-3.0146) and significance of p = 0.00048. None of Saudi subjects (normal as well as diseased) showed 21-bp deletion as reported previously for other populations. In addition, genotype TT of rs325400 is associated with significantly higher levels of LDL-C and lower level of HDL-C. Among the quantitative parameters, lower HDL-C and higher LDL-C was found to be associated with disease. We report that MEF2A gene based on SNP rs325400 (G1323T) can be considered as a susceptibility factor for CAD and presence of T allele makes Saudis at more risk to CAD, while other variants detected in this gene do not have any association in Saudi population.

EFHC1 variants in juvenile myoclonic epilepsy: reanalysis according to NHGRI and ACMG guidelines for assigning disease causality

PURPOSE

EFHC1 variants are the most common mutations in inherited myoclonic and grand mal clonic-tonic-clonic (CTC) convulsions of juvenile myoclonic epilepsy (JME). We reanalyzed 54 EFHC1 variants associated with epilepsy from 17 cohorts based on National Human Genome Research Institute (NHGRI) and American College of Medical Genetics and Genomics (ACMG) guidelines for interpretation of sequence variants.

METHODS

We calculated Bayesian LOD scores for variants in coinheritance, unconditional exact tests and odds ratios (OR) in case-control associations, allele frequencies in genome databases, and predictions for conservation/pathogenicity. We reviewed whether variants damage EFHC1 functions, whether efhc1^-/- KO mice recapitulate CTC convulsions and "microdysgenesis" neuropathology, and whether supernumerary synaptic and dendritic phenotypes can be rescued in the fly model when EFHC1 is overexpressed. We rated strengths of evidence and applied ACMG combinatorial criteria for classifying variants.

RESULTS

Nine variants were classified as "pathogenic," 14 as "likely pathogenic," 9 as "benign," and 2 as "likely benign." Twenty variants of unknown significance had an insufficient number of ancestry-matched controls, but ORs exceeded 5 when compared with racial/ethnic-matched Exome Aggregation Consortium (ExAC) controls.

CONCLUSIONS

NHGRI gene-level evidence and variant-level evidence establish EFHC1 as the first non-ion channel microtubule-associated protein whose mutations disturb R-type VDCC and TRPM2 calcium currents in overgrown synapses and dendrites within abnormally migrated dislocated neurons, thus explaining CTC convulsions and "microdysgenesis" neuropathology of JME.Genet Med 19 2, 144-156.

Genetics of Coronary Artery Disease

Genetic factors contribute importantly to the risk of coronary artery disease (CAD), and in the past decade, there has been major progress in this area. The tools applied include genome-wide association studies encompassing >200,000 individuals complemented by bioinformatic approaches, including 1000 Genomes imputation, expression quantitative trait locus analyses, and interrogation of Encyclopedia of DNA Elements, Roadmap, and other data sets. close to 60 common SNPs (minor allele frequency>0.05) associated with CAD risk and reaching genome-wide significance (P<5 × 10(-8)) have been identified. Furthermore, a total of 202 independent signals in 109 loci have achieved a false discovery rate (q<0.05) and together explain 28% of the estimated heritability of CAD. These data have been used successfully to create genetic risk scores that can improve risk prediction beyond conventional risk factors and identify those individuals who will benefit most from statin therapy. Such information also has important applications in clinical medicine and drug discovery by using a Mendelian randomization approach to interrogate the causal nature of many factors found to associate with CAD risk in epidemiological studies. In contrast to genome-wide association studies, whole-exome sequencing has provided valuable information directly relevant to genes with known roles in plasma lipoprotein metabolism but has, thus far, failed to identify other rare coding variants linked to CAD. Overall, recent studies have led to a broader understanding of the genetic architecture of CAD and demonstrate that it largely derives from the cumulative effect of multiple common risk alleles individually of small effect size rather than rare variants with large effects on CAD risk. Despite this success, there has been limited progress in understanding the function of the novel loci; the majority of which are in noncoding regions of the genome.

Dysregulation of RBFOX2 Is an Early Event in Cardiac Pathogenesis of Diabetes

Alternative splicing (AS) defects that adversely affect gene expression and function have been identified in diabetic hearts; however, the mechanisms responsible are largely unknown. Here, we show that the RNA-binding protein RBFOX2 contributes to transcriptome changes under diabetic conditions. RBFOX2 controls AS of genes with important roles in heart function relevant to diabetic cardiomyopathy. RBFOX2 protein levels are elevated in diabetic hearts despite low RBFOX2 AS activity. A dominant-negative (DN) isoform of RBFOX2 that blocks RBFOX2-mediated AS is generated in diabetic hearts. DN RBFOX2 interacts with wild-type (WT) RBFOX2, and ectopic expression of DN RBFOX2 inhibits AS of RBFOX2 targets. Notably, DN RBFOX2 expression is specific to diabetes and occurs at early stages before cardiomyopathy symptoms appear. Importantly, DN RBFOX2 expression impairs intracellular calcium release in cardiomyocytes. Our results demonstrate that RBFOX2 dysregulation by DN RBFOX2 is an early pathogenic event in diabetic hearts.

Novel 6-bp deletion in MEF2A linked to premature coronary artery disease in a large Chinese family

The aim of the present study was to identify the genetic defect responsible for familial coronary artery disease/myocardial infarction (CAD/MI), which exhibited an autosomal dominant pattern of inheritance, in an extended Chinese Han pedigree containing 34 members. Using exome and Sanger sequencing, a novel 6-base pair (bp) 'CAGCCG' deletion in exon 11 of the myocyte enhancer factor 2A (MEF2A) gene was identified, which cosegregated with CAD/MI cases in this family. This 6-bp deletion was not detected in 311 sporadic cases of premature CAD/MI or in 323 unrelated healthy controls. Determination of a genetic risk profile has a key role in understanding the pathogenesis of CAD and MI. Among the reported risk conferring genes and their variants, mutations in MEF2A have been reported to segregate with CAD/MI in Caucasian families. Causative missense mutations have also been detected in sporadic CAD/MI cases. However, this suggested genetic linkage is controversial, since it could not be confirmed by ensuing studies. The discovery of a novel MEF2A mutation in a Chinese family with premature CAD/MI suggests that MEF2A may have a significant role in the pathogenesis of premature CAD/MI. To better understand this association, further in vitro and in vivo studies are required.

Myocyte Enhancer Factor-2A Gene Mutation and Coronary Artery Disease

BACKGROUND

Premature ventricular contractions (PVCs) are common in the general population, and frequent PVCs may result in the poor quality of life or even the damage of cardiac function. We examined the efficacy and safety of a traditional Chinese medicine Wenxin Keli for the treatment of frequent PVCs among a relatively large Chinese cohort.

METHODS

We performed a randomized, double-blind, placebo-controlled, parallel-group, multicenter trial. A total of 1200 eligible participants were randomly assigned in a ratio of 1:1 to receive Wenxin Keli or the placebo for 4 weeks. The primary and secondary endpoint was the change of PVC numbers and PVC-related symptoms after a 4-week treatment compared with baseline, respectively. In addition, vital signs, laboratory values, and electrocardiographic parameters were assessed in a safety analysis.

RESULTS

At the initial evaluation, no significant differences in the baseline characteristics were observed between the Wenxin Keli group and the placebo group. A smaller number of PVCs was observed after the 4-week treatment than at baseline, in both the Wenxin Keli group (5686 ± 5940 vs. 15,138 ± 7597 beats/d, P < 0.001) and the placebo group (10,592 ± 8009 vs. 14,529 ± 5929 beats/d, P < 0.001); moreover, the Wenxin Keli group demonstrated a significantly greater reduction in the frequency of PVCs than the placebo group (P < 0.001). In a full analysis set, patients in the Wenxin Keli group exhibited significantly higher total effective responses in the reduction of PVCs compared to those in the placebo group (83.8% vs. 43.5%,P < 0.001). The per-protocol analysis yielded similar results (83.0% vs. 39.3%,P < 0.001). Treatment with Wenxin Keli also demonstrated superior performance compared to the placebo with respect to PVC-related symptoms. No severe adverse effects attributable to Wenxin Keli were reported.

CONCLUSIONS

Wenxin Keli treatment effectively reduced the overall number of PVCs and alleviated PVC-related symptoms in patients without structural heart diseases and had no severe side effects.

Genetics of coronary artery disease and myocardial infarction

Atherosclerotic coronary artery disease (CAD) comprises a broad spectrum of clinical entities that include asymptomatic subclinical atherosclerosis and its clinical complications, such as angina pectoris, myocardial infarction (MI) and sudden cardiac death. CAD continues to be the leading cause of death in industrialized society. The long-recognized familial clustering of CAD suggests that genetics plays a central role in its development, with the heritability of CAD and MI estimated at approximately 50% to 60%. Understanding the genetic architecture of CAD and MI has proven to be difficult and costly due to the heterogeneity of clinical CAD and the underlying multi-decade complex pathophysiological processes that involve both genetic and environmental interactions. This review describes the clinical heterogeneity of CAD and MI to clarify the disease spectrum in genetic studies, provides a brief overview of the historical understanding and estimation of the heritability of CAD and MI, recounts major gene discoveries of potential causal mutations in familial CAD and MI, summarizes CAD and MI-associated genetic variants identified using candidate gene approaches and genome-wide association studies (GWAS), and summarizes the current status of the construction and validations of genetic risk scores for lifetime risk prediction and guidance for preventive strategies. Potential protective genetic factors against the development of CAD and MI are also discussed. Finally, GWAS have identified multiple genetic factors associated with an increased risk of in-stent restenosis following stent placement for obstructive CAD. This review will also address genetic factors associated with in-stent restenosis, which may ultimately guide clinical decision-making regarding revascularization strategies for patients with CAD and MI.

Myocardial Infarction-Associated SNP at 6p24 Interferes With MEF2 Binding and Associates With PHACTR1 Expression Levels in Human Coronary Arteries

OBJECTIVE

Coronary artery disease (CAD), including myocardial infarction (MI), is the main cause of death in the world. Genome-wide association studies have identified dozens of single nucleotide polymorphisms (SNPs) associated with CAD/MI. One of the most robust CAD/MI genetic associations is with intronic SNPs in the gene PHACTR1 on chromosome 6p24. How these PHACTR1 SNPs influence CAD/MI risk, and whether PHACTR1 itself is the causal gene at the locus, is currently unknown.

APPROACH AND RESULTS

Using genetic fine-mapping and DNA resequencing experiments, we prioritized an intronic SNP (rs9349379) in PHACTR1 as causal variant. We showed that this variant is an expression quantitative trait locus for PHACTR1 expression in human coronary arteries. Experiments in endothelial cell extracts confirmed that alleles at rs9349379 are differentially bound by the transcription factors myocyte enhancer factor-2. We engineered a deletion of this myocyte enhancer factor-2-binding site using CRISPR/Cas9 genome-editing methodology. Heterozygous endothelial cells carrying this deletion express 35% less PHACTR1. Finally, we found no evidence that PHACTR1 expression levels are induced when stimulating human endothelial cells with vascular endothelial growth factor, tumor necrosis factor-α, or shear stress.

CONCLUSIONS

Our results establish a link between intronic SNPs in PHACTR1, myocyte enhancer factor-2 binding, and transcriptional functions at the locus, PHACTR1 expression levels in coronary arteries and CAD/MI risk. Because PHACTR1 SNPs are not associated with the traditional risk factors for CAD/MI (eg, blood lipids or pressure, diabetes mellitus), our results suggest that PHACTR1 may influence CAD/MI risk through as yet unknown mechanisms in the vascular endothelium.

RNA interference of myocyte enhancer factor 2A accelerates atherosclerosis in apolipoprotein E-deficient mice

Objective

Myocyte enhancer factor-2A (MEF 2A) has been shown to be involved in atherosclerotic lesion development, but its role in preexisting lesions is still unclear. In the present study we aim to assess the role of MEF 2A in the progression of pre-existing atherosclerosis.

Methods

Eighty apolipoprotein E-deficient mice (APOE KO) were randomly allocated to control, scramble and MEF 2A RNA interference (RNAi) groups, and constrictive collars were used to induce plaque formation. Six weeks after surgery, lentiviral shRNA construct was used to silence the expression of MEF 2A. Carotid plaques were harvested for analysis 4 weeks after viral vector transduction. Inflammatory gene expression in the plasma and carotid plaques was determined by using ELISAs and real-time RT-PCR.

Results

The expression level of MEF 2A was significantly reduced in plasma and plaque in the RNAi group, compared to the control and NC groups, whereas the expression level of pro-inflammatory cytokines was markedly increased. Silencing MEF 2A using lentiviral shRNA significantly reduced the plaque collagen content and fibrous cap thickness, as well as increased plaque area. However, silencing MEF 2A had no obvious effect on plaque lipid content.

Conclusions

Lentivirus-mediated MEF 2A shRNA accelerates inflammation and atherosclerosis in APOE KO mice, but has no effect on lipoprotein levels in plasma.

Guidelines for investigating causality of sequence variants in human disease

The discovery of rare genetic variants is accelerating, and clear guidelines for distinguishing disease-causing sequence variants from the many potentially functional variants present in any human genome are urgently needed. Without rigorous standards we risk an acceleration of false-positive reports of causality, which would impede the translation of genomic research findings into the clinical diagnostic setting and hinder biological understanding of disease. Here we discuss the key challenges of assessing sequence variants in human disease, integrating both gene-level and variant-level support for causality. We propose guidelines for summarizing confidence in variant pathogenicity and highlight several areas that require further resource development.

Association of MEF2A gene polymorphisms with coronary artery disease

Background:

Coronary Artery Disease (CAD) is the most common cause of death worldwide. MEF2A directly regulates target genes in the process of muscle development. This gene product is a transcription factor. MEF2A protein in homodimer or heterodimer forms binds to A/T-rich cis elements with conserved sequence in promoter, regulator, and enhancer of many genes, which are determining in evolution and development of skeletal, heart, and smooth muscle cells, especially endothelial cells. In fact, this protein maximizes the activity of these elements.

Objectives:

The two MEF2A gene polymorphisms that were proposed to have an association with CAD are rs34851361 (A/G) and rs325400 (T/G) SNPs. This study aimed to examine these associations.

Patients and Methods:

This study was a molecular case-control study. Blood samples were collected from 300 patients with CAD and 150 healthy people from Golestan and Imam Khomeini Hospitals, Ahvaz, Iran. In both groups, angiography had confirmed the presence or lack of stenosis. Association of rs34851361 and rs325400 with CAD was evaluated by PCR and then restriction fragment length polymorphism (RFLP) analysis was performed.

Results:

Chi square test showed no association between rs34851361 SNP and CAD (χ² = 3.59, df = 2, and P = 0.16); however, there was an association between rs325400 SNP and CAD (χ² = 24.77, df = 2, and P < 0.001). A/T haplotype showed association with CAD and G/G and G/T showed protective effect against CAD.

Conclusions:

The results of this study show that rs325400 polymorphism is in association with CAD; meanwhile, none of the rs34851361 genotypes was associated with CAD.

Mutation in ST6GALNAC5 identified in family with coronary artery disease

We aimed to identify the genetic cause of coronary artery disease (CAD) in an Iranian pedigree. Genetic linkage analysis identified three loci with an LOD score of 2.2. Twelve sequence variations identified by exome sequencing were tested for segregation with disease. A p.Val99Met causing mutation in ST6GALNAC5 was considered the likely cause of CAD. ST6GALNAC5 encodes sialyltransferase 7e. The variation affects a highly conserved amino acid, was absent in 800 controls, and was predicted to damage protein function. ST6GALNAC5 is positioned within loci previously linked to CAD-associated parameters. While hypercholesterolemia was a prominent feature in the family, clinical and genetic data suggest that this condition is not caused by the mutation in ST6GALNAC5. Sequencing of ST6GALNAC5 in 160 Iranian patients revealed a candidate causative stop-loss mutation in two other patients. The p.Val99Met and stop-loss mutations both caused increased sialyltransferase activity. Sequence data from combined Iranian and US controls and CAD affected individuals provided evidence consistent with potential role of ST6GALNAC5 in CAD. We conclude that ST6GALNAC5 mutations can cause CAD. There is substantial literature suggesting a relation between sialyltransferase and sialic acid levels and coronary disease. Our findings provide strong evidence for the existence of this relation.

Mutation in CYP27A1 identified in family with coronary artery disease

Coronary artery disease (CAD) is a leading cause of death worldwide. Myocardial infarction is the most severe outcome of CAD. Despite extensive efforts, the genetics of CAD is poorly understood. We aimed to identify the genetic cause of CAD in a pedigree with several affected individuals. Exome sequencing led to identification of a mutation in CYP27A1 that causes p.Arg225His in the encoded protein sterol 27-hydroxylase as the likely cause of CAD in the pedigree. The enzyme is multifunctional, and several of its functions including its functions in vitamin D metabolism and reverse cholesterol transport (RCT) are relevant to the CAD phenotype. Measurements of vitamin D levels suggested that the mutation does not affect CAD by affecting this parameter. We suggest that the mutation may cause CAD by affecting RCT. Screening of all coding regions of the CYP27A1 in 100 additional patients led to finding four variations (p.Arg14Gly, p.Arg26Lys, p.Ala27Arg, and p.Val86Met) in seven patients that may contribute to their CAD status. CYP27A1 is the known causative gene of cerebrotendinous xanthomatosis, a disorder which is sometimes accompanied by early onset atherosclerosis. This and the observation of potentially harmful variations in unrelated CAD patients provide additional evidence for the suggested causative role of the p.Arg225His mutation in CAD.

A novel clinician interface to improve clinician access to up-to-date genetic results

OBJECTIVES

To understand the impact of GeneInsight Clinic (GIC), a web-based tool designed to manage genetic information and facilitate communication of test results and variant updates from the laboratory to the clinics, we measured the use of GIC and the time it took for new genetic knowledge to be available to clinicians.

METHODS

Usage data were collected across four study sites for the GIC launch and post-GIC implementation time periods. The primary outcome measures were the time (average number of days) between variant change approval and notification of clinic staff, and the time between notification and viewing the patient record.

RESULTS

Post-GIC, time between a variant change approval and provider notification was shorter than at launch (average days at launch 503.8, compared to 4.1 days post-GIC). After e-mail alerts were sent at launch, providers clicked into the patient record associated with 91% of these alerts. In the post period, clinic providers clicked into the patient record associated with 95% of the alerts, on average 12 days after the e-mail was sent.

DISCUSSION

We found that GIC greatly increased the likelihood that a provider would receive updated variant information as well as reduced the time associated with distributing that variant information, thus providing a more efficient process for incorporating new genetic knowledge into clinical care.

CONCLUSIONS

Our study results demonstrate that health information technology systems have the potential effectively to assist providers in utilizing genetic information in patient care.

Lack of Association between the MEF2A Gene and Coronary Artery Disease in Iranian Families

OBJECTIVE(S)

Coronary artery disease (CAD) which may lead to myocardial infarction (MI) is a complex one. Great effort has been devoted to identification of genes that increase susceptibility to CAD or provide protection. A 21-bp deletion in the MEF2A gene, which encodes a member of the myocyte enhancer factor 2 family of transcription factors, has been reported in patients of a single pedigree that exhibited autosomal-dominant inheritance of CAD. Subsequent analysis of genetic variants within the gene in CAD and MI case-control settings produced inconsistent results. Here, we aimed at assessing the contribution of MEF2A to CAD in a cohort of Iranian CAD patients.

MATERIALS AND METHODS

Exon 11 of MEF2A wherein the above mentioned 21-bp deletion and a polyglutamine (CAG)n polymorphism are positioned was sequenced by the dideoxy-nucleotide termination protocol. In 52 CAD patients from 12 families (3-7 affected members per family) and 76 Iranian control individuals. All exons of the gene were sequenced in 10 patients and 10 controls.

RESULTS

The 21-bp deletion was observed neither among the patients nor the control individuals. Four alleles of the polyglutamine (CAG)n polymorphism were found, but there were no significant differences in allelic frequencies between patients and controls. Sequencing of all exons of MEF2A revealed the presence of 12 novel sequence variations in introns and flanking regions of MEF2A gene, not associated with disease status.

CONCLUSION

Our data do not support a role for MEF2A in coronary artery disease in the Iranian patients studied.

Analysis of MEF2A mutations in a Chinese population with premature coronary artery disease

AIMS

To assess the relationship between mutations of the myocyte enhancer factor 2A (MEF2A) and premature coronary artery disease (PCAD) in a Chinese population.

METHODS AND RESULTS

The mutations in the exons 8 and 12 of the MEF2A gene were analyzed in both PCAD families and sporadic cases using direct sequencing of polymerase chain reaction products. In one PCAD family, seven members of the third generation were all diagnosed with CAD, and five of them had PCAD. All five members with PCAD displayed a mutation of the TT genotype in the site of 1353 G/T. Moreover, three of them (3/5) had a mutation of the DW genotype in the site of 1291-1293 CCG W/D. In sporadic cases, we also found that the haplotype of 1291-1293 CCG D+1305 G+1353 T was significantly associated with PCAD.

CONCLUSIONS

The mutations of MEF2A exon 12 are implicated in PCAD, suggesting a strong genetic component in the pathogenesis of PCAD in the Chinese population.

Whole-exome sequencing of a pedigree segregating asthma

Background

Despite the success of genome-wide association studies for asthma, few, if any, definitively causal variants have been identified and there is still a substantial portion of the heritability of the disease yet to be discovered. Some of this “missing heritability” may be accounted for by family-specific coding variants found to be segregating with asthma.

Methods

To identify family-specific variants segregating with asthma, we recruited one family from a previous study of asthma as reporting multiple asthmatic and non-asthmatic children. We performed whole-exome sequencing on all four children and both parents and identified coding variants segregating with asthma that were not found in other variant databases.

Results

Ten novel variants were identified that were found in the two affected offspring and affected mother, but absent in the unaffected father and two unaffected offspring. Of these ten, variants in three genes (PDE4DIP, CBLB, and KALRN) were deemed of particular interest based on their functional prediction scores and previously reported function or asthma association. We did not identify any common risk variants segregating with asthma, however, we did observe an increase in the number of novel, nonsynonymous variants in asthma candidate genes in the asthmatic children compared to the non-asthmatic children.

Conclusions

This is the first report applying exome sequencing to identify asthma susceptibility variants. Despite having sequenced only one family segregating asthma, we have identified several potentially functional variants in interesting asthma candidate genes. This will provide the basis for future work in which more families will be sequenced to identify variants across families that cluster within genes.

Variants in exon 11 of MEF2A gene and coronary artery disease: evidence from a case-control study, systematic review, and meta-analysis

Background

Coronary artery disease (CAD) is the most common heart disease worldwide. Association of CAD with variants in the myocyte enhancer factor 2A (MEF2A) gene, the first identified CAD-causing gene, has attracted special attention but the results are controversial. We aimed to evaluate this genetic association via a case-control study and meta-analysis.

Methodology/Principal Findings

We performed a case-control association study to investigate the relationship between variations in exon 11 of MEF2A gene and CAD in 1045 sporadic patients and 1008 controls enrolled angiographically among southern Chinese population, and then the data from this study were compared and discussed in a systematic review and meta-analysis with all available published studies on MEF2A gene and CAD. In total, eight variants were identified (21-bp deletion, CAG repeats, CCG repeats, a CCA deletion and four SNPs). No significant link was observed between the common (CAG)_n polymorphism and CAD, whereas the rare 21-bp deletion was detected only in five affected individuals. The meta-analysis of (CAG)_n polymorphism and CAD risk, including nine studies with 3801 CAD patients and 4020 controls, also provided no convincing evidence for the genetic association, even upon stratification by race (mainly Whites and Chinese). However, the 21-bp deletion was regarded as a potentially logical, albeit undetermined, candidate for CAD in the following systematic review.

Conclusions/Significance

Our findings failed to demonstrate a correlation between (CAG)_n polymorphism with CAD, however, we concluded that the rare 21-bp deletion might have a more compelling effect on CAD than the common (CAG)_n polymorphism, and MEF2A genetic variant might be a rare but specific cause of CAD/MI.

Promoter variant-dependent mRNA expression of the MEF2A in longissimus dorsi muscle in cattle

The myocyte enhancer factor 2A (MEF2A) gene encodes a member of the myocyte enhancer factor 2 (MEF2) protein family that is involved in vertebrate skeletal, cardiac, and smooth muscle development and differentiation during myogenesis. According to recent studies, MEF2 genes might be major regulators of postnatal skeletal muscle growth; thus, they are considered to be important, novel candidates for muscle development and body growth in farm animals. The aim of the present study was to search for polymorphisms in the bovine MEF2A gene and analyze their effect on the MEF2A mRNA expression level in the longissimus dorsi muscle of Polish Holstein-Fresian cattle. In total, 4094 bp of the whole coding sequence and the promoter region of MEF2A were re-sequenced in 30 animals, resulting in the detection of 6 novel variants as well as one previously reported SNP. Three linked mutations in the promoter region (-780T/G, g.-768T/G, and g.-222A/G) and only two genotypes were identified in two Polish breeds (TTA/TTA and TTA/GGG). Three SNPs in the coding region [g.1599G/A (421aa), g.1626G/A (429aa), and g.1641G/A (434aa)] appeared to be silent substitutions and segregated as two intragene haplotypes: GGG and AAA. Expression analysis showed that the mutations in the promoter region are highly associated with the MEF2A mRNA level in the longissimus dorsi muscle of bulls carrying two different genotypes. The higher MEF2A mRNA level was estimated in the muscle of bulls carrying the TTA/TTA (p<0.01) genotype as compared with those with TTA/GGG. The results obtained suggest that the nucleotide sequence mutation in MEF2A might be useful marker for body growth traits in cattle.

"My parents died of myocardial infarction: is that my destiny?"

This article presents an overview of clinical and molecular genetics of myocardial infarction (MI). Discussion includes the partial overlapping of risk factors for myocardial infarction and atherosclerosis, the impact of a positive family history on the risk of MI, the "familial" nongenetic, environmental factors, the inherited risk associated with the low-dose input of many genes, and a simple approach to stratify the individual risk in genetic counseling.

Exon 11 deletion in the myocyte enhancer factor (MEF)2A and early onset coronary artery disease gene in a Sicilian family

AIMS

We investigated the prevalence of the myocyte enhancer factor (MEF)2A exon 11 deletion, a putative coronary artery disease (CAD) susceptibility gene, in patients referred for coronary angiography.

METHODS AND RESULTS

In total, 1079 consecutive patients referred for coronary angiography in the GENICA Study were genotyped and 301 low-risk subjects were used as controls. One patient with early onset three vessels CAD, carrying the MEF2A deletion was found in the GENICA Study cohort and none in the control group.

CONCLUSION

In a cohort of patients undergoing coronary angiography for suspected CAD the MEF2A exon 11 deletion occurred in 0.09%.

Genetics of coronary artery disease

Coronary artery disease and its clinical manifestations, including myocardial infarction, are heritable traits, consistent with a role for inherited DNA sequence variation in conferring risk for disease. Knowledge of the new sequence variations in the genome that confer risk has the potential to illuminate new causal biologic pathways in humans and to thereby further improve diagnosis and treatment. Here, we review recent progress in mapping genetic loci related to coronary disease and risk factor phenotypes, including plasma lipoprotein concentrations. Genome-wide linkage (in families) and association (in populations) studies have identified more than a dozen genetic loci related to coronary disease. A key challenge now is to move from mapping loci to pinpointing causal genes and variants, and to develop a molecular understanding of how these genes lead to coronary disease.

Structural changes in exon 11 of MEF2A are not related to sporadic coronary artery disease in Han Chinese population

BACKGROUND

A mutation in MEF2A (myocyte enhancer factor-2A) had been reported to be the first gene linked directly to coronary artery disease (CAD). However, an opposing opinion was proposed recently that MEF2A mutations are not a common cause of sporadic CAD. In this study, we screened exon 11 of the MEF2A gene in people of the Han nationality in China and finished some functional analysis of found variations.

MATERIALS AND METHODS

A gene structural investigation of MEF2A in 257 CAD patients and 154 control individuals were developed in this study. Subsequently, typical MEF2A variations were cloned and expressed in HeLa or 293T cell line to illustrate whether found structure changes could influence the main biological functions of these proteins. At last, another set of gene structural screen was initialized to get more reliable conclusions.

RESULTS

Totally 16 different variations were detected in exon 11 of this gene in the first set of gene structural screen. By cloning and expressing typical MEF2A proteins in cultured cells, all the acquired MEF2A variations had transcriptional activation capabilities and subcellular localization patterns similar to those of the wild-type protein. Further larger scale genetic screening also revealed that the reported genetic variations of MEF2A did not differ significantly between CAD patients and healthy controls.

CONCLUSIONS

Our results reveal that structural changes of exon 11 in MEF2A are not involved in sporadic CAD in the Han population of China.

A study of the role of the Myocyte-specific Enhancer Factor-2A gene in coronary artery disease

We evaluated the role of the MEF2A as a risk factor for coronary artery disease (CAD) in 1186 subjects with angiographically documented disease compared with 885 CAD-free individuals in the Saudi population. Screening the gene revealed exon 11 as the most polymorphic of all coding regions, harbouring several substitution polymorphisms and insertion/deletions (indels) at a locus containing an 11 CAG trinucleotide chain and a CCGCCGCCA sequence, which introduced frameshifts and premature stop codons at nt146637 and nt146647, nt146780 or nt146783. While these indels were not significantly associated with CAD, a causative relationship was established for rs1059759 G>C [1.21(1.02-1.43); p=0.029], and a borderline one for rs34851361 A>G [1.22(0.9-1.54); p=0.088]. Importantly, a haplotype 1A-2G-3G-4A-5C-6G-7G-8A constructed from the studied SNPs was also associated with CAD [6.39(0.93-43.75); p=0.0052]. These results identify MEF2A gene as a susceptibility gene for CAD.

Creating a genetic risk score for coronary artery disease

Coronary artery disease (CAD) and its sequelae represent a significant health burden. Over the past two decades, numerous studies have attempted to link DNA sequence variation with the risk of CAD and related phenotypes. There has been significant evolution in technology from the early linkage studies within kindreds, and now we are able to use high-density genotyping to facilitate large-scale genome-wide association studies. The first novel genetic risk factor for CAD, 9p21.3, has been confirmed, and other loci are awaiting replication studies. The relative importance of each locus from a global standpoint and the incremental information conferred by testing for genetic variants remain to be determined.

Association and functional analyses of MEF2A as a susceptibility gene for premature myocardial infarction and coronary artery disease

BACKGROUND

Mutations in the MEF2A gene, coding for a member of the myocyte enhancer factor 2 family of transcription factors, have been reported in patients with coronary artery disease and myocardial infarction (MI). In particular, a 21-bp deletion and 3 missense mutations were demonstrated either to reduce MEF2A transcriptional activity or to impair its nuclear translocation. However, the association of MEF2A with coronary artery disease/MI was not confirmed in other studies. We analyzed the role of MEF2A in the pathogenesis of MI in 2008 Italian patients with premature MI and in 2008 controls.

METHODS AND RESULTS

Mutational screening of exon 8 (containing all so-far reported point mutations) disclosed 5 novel and 2 previously described missense mutations. Microsatellite genotyping and sequencing revealed the presence of the 21-bp deletion (located in exon 12) in 5 cases and in none of the controls. Functional studies on mutant proteins showed no alteration, neither in the transactivating properties (all mutants) nor in the nuclear localization (21-bp deletion). Furthermore, an association analysis performed using 3 microsatellites at the MEF2A locus showed no significant association with MI. These results were confirmed in a replication study performed on an independent Italian population with coronary artery disease.

CONCLUSIONS

All together, our data do not support MEF2A as a susceptibility gene for coronary artery disease/MI in the Italian population.

CAG repeat polymorphism of the MEF2A gene is not associated with the risk of coronary artery disease among Taiwanese

A 21-bp deletion mutation of the exon 11 of the myocyte enhancer factor-2A (MEF2A) gene was shown to cause familial coronary artery disease. This finding raises the possibility that MEF2A variants may contribute to the risk of coronary artery disease. In total, 258 patients with coronary artery disease and 258 controls were analyzed for the MEF2A variants. The analysis revealed that all patients were negative for Pro279Leu and 21-bp deletion mutations in exons 7 and 11, respectively. The distribution of the allele frequencies of MEF2A exon 11 CAG repeat (CAG)n polymorphism was similar in both patients and controls; Further, no significant association was noted between MEF2A exon 11 (CAG)n polymorphism and the risk of myocardial infarction. Our data suggest that there is no evidence of an association between the MEF2A exon 11 (CAG)n polymorphism and the risk of coronary artery disease/myocardial infarction in the Chinese population in Taiwan.

Genetics of premature myocardial infarction

Common multigene disorders account for 80% of deaths in the world and all have significant genetic predisposition. Coronary artery disease and myocardial infarction (MI) account for more than 40% of these deaths. The genetic component is due to multiple genes, each contributing only minimally to the phenotype. Linkage analysis, which has been successful in identifying rare disorders that cause MI, is not sensitive for multigene disorders. The recent candidate case-control approach has been equally unsuccessful. Multigene disorders require genome-wide association studies involving genotyping hundreds of thousands of DNA markers in thousands of individuals with replication in independent populations. Platforms with 500,000 and 1 million single nucleotide polymorphisms provide the necessary high-throughput genotyping for genome-wide association. The first confirmed common locus, 9p21, is independent of conventional risk factors. Identifying the 9p21 gene will elucidate novel mechanisms responsible for MI. Comprehensive prevention of MI based on individual genetic variants (personalized medicine) is expected in the next decade.

Common and rare alleles as causes of complex phenotypes

A full understanding of the molecular basis for genetically determined human traits, including susceptibility to disease, appears to be within reach following recent breakthroughs. How fully this promise will be realized, and by which combination of study designs, will depend to a large extent on the allelic architecture of each trait, which is still unknown in most cases. The prevailing belief that traits common in the general population must depend on common variants is challenged by theoretical predictions based on the mutation-selection model. This model states that if disease variants are subject to even weak purifying selection, their presence can be maintained only by new mutations, resulting in a multitude of rare alleles at each locus. Predictions favoring each scenario have relied on biased evidence and unverifiable assumptions, respectively. However, unbiased factual testing of them may soon be possible, as data accumulate from genome-wide association studies and high-throughput resequencing. Because the models are not mutually exclusive, the question should be not which model is correct, but rather what is the relative contribution of each, which is something that may vary dramatically among traits.

Power of genome-wide association studies in the presence of interacting loci

Though multiple interacting loci are likely involved in the etiology of complex diseases, early genome-wide association studies (GWAS) have depended on the detection of the marginal effects of each locus. Here, we evaluate the power of GWAS in the presence of two linked and potentially associated causal loci for several models of interaction between them and find that interacting loci may give rise to marginal relative risks that are not generally considered in a one-locus model. To derive power under realistic situations, we use empirical data generated by the HapMap ENCODE project for both allele frequencies and linkage disequilibrium (LD) structure. The power is also evaluated in situations where the causal single nucleotide polymorphisms (SNPs) may not be genotyped, but rather detected by proxy using a SNP in LD. A common simplification for such power computations assumes that the sample size necessary to detect the effect at the tSNP is the sample size necessary to detect the causal locus directly divided by the LD measure r(2) between the two. This assumption, which we call the "proportionality assumption", is a simplification of the many factors that contribute to the strength of association at a marker, and has recently been criticized as unreasonable (Terwilliger and Hiekkalinna [2006] Eur J Hum Genet 14(4):426-437), in particular in the presence of interacting and associated loci. We find that this assumption does not introduce much error in single locus models of disease, but may do so in so in certain two-locus models.

Identifying genes for coronary artery disease: An idea whose time has come

BACKGROUND

Coronary artery disease (CAD) remains the number one killer in the western world. Genetics accounts for greater than 50% of the risk for CAD. Genetic screening and early prevention in individuals identified as being at increased risk could dramatically reduce the prevalence of CAD, thus necessitating the identification of genes predisposing to CAD. Studies of genes identified by the candidate gene approach have not been replicated due, in part, to inadequate sample size. Genome-wide scan association studies have been limited by the use of thousands of markers rather than the hundreds of thousands required, and by the use of hundreds of individuals rather than the thousands required. Replication of positive findings in an independent population is essential. To detect a minor allele frequency of 5% or greater with an odds ratio for risk of 1.3 or greater and 90% power, an estimated 14,000 (9000 affected and 5000 control) subjects are required.

METHODS

The Affymetrix GeneChip Human Mapping 500K Array Set (Affymetrix Inc, USA) provides a marker every 6000 base pairs as required, and is being used to genotype 1000 cases of premature CAD and 1000 normal subjects, followed by replication in 8000 affected individuals and 4000 control subjects. The phenotype is confirmed or excluded by coronary arteriograms by catheterization or multislice computed tomography.

RESULTS

Since 2005, more than 800 million genotypes have been performed and analyses performed on 500 control subjects and 500 affected individuals. Several thousand significant single nucleotide polymorphisms and 130 clusters associated with CAD have been identified.

CONCLUSIONS

This is the first genome-wide scan using the 500,000 marker set in a case-control association study for CAD genes. Several genes associated with CAD appear promising.

Relationship of the CAG repeat polymorphism of the MEF2A gene and coronary artery disease in a Chinese population

BACKGROUND

Recently, a mutation in the human myocyte enhancer factor-2A (MEF2A) gene was reported to be responsible for an autosomal dominant form of coronary artery disease (CAD). In addition, missense mutations in sporadic CAD patients were also described. Both results support the disease-causing relationship between MEF2A and CAD/myocardial infarction. On the other hand, conflicting hypotheses have been put forward in other studies.

METHODS

We screened exons 7 and 11 of MEF2A through single-stranded conformation polymorphism PCR and direct sequencing to clarify the relationship between MEF2A and CAD in an independent case-control study involving 726 individuals in China.

RESULTS

Exon 11 showed a high degree of heterogeneity, which was caused by a polyglutamine (CAG)n polymorphism. Frequencies for the different (CAG)n alleles were not the same between patient and control groups. Of note, the distribution frequency of the (CAG)9 allele was higher in the patient group than in the control group (p<0.001). This effect was independent of age, gender, hypertension, diabetes mellitus, hyperlipidemia and smoking in a logistic regression model (p=0.001, odds ratio 1.245, 95% CI 1.095-1.417). It was also observed that the (CAG)9 allele was related to the extent of CAD, which was defined as no CAD, or single-, double- or triple-vessel disease (p trend 0.000).

CONCLUSIONS

Based on our data, we speculate that the CAG repeat polymorphism is associated with coronary heart disease in the Chinese population and the (CAG)9 allele may be an independent predictive factor for CAD.

MEF2A sequence variants in Turkish population

Myocyte enhancer factor 2 (MEF2) is present in skeletal, cardiac, and smooth muscles and in neurons. MEF2A gene encodes a transcription factor which was on 15q26. The objective was to study the MEF2A gene in patients with premature MI. The control group consisted of 87 subjects who were older than 45 years with no history of cardiovascular disease or MI and no family history of CAD. The premature MI group consisted of 69 patients with documented MI younger than 45 years. No abnormal bands with single strand conformation polymorphism were detected after screening exon 1 through exon 8. This is the first study that detected 145408: T>C polymorphism in intron 10. In both study groups, the rare polymorphism P279L in exon 7, T>C polymorphism in intron 10, and 21-bp deletion in exon 11 of the gene were not found. The data supported the previous studies indicating no association between MEF2A gene and premature MI.

Lack of association between the MEF2A gene and myocardial infarction

BACKGROUND

Coronary artery disease (CAD) and myocardial infarction (MI) are caused in part by genetic factors. Recently, the MEF2A gene was linked to MI/CAD in a single pedigree with autosomal-dominant pattern of inheritance. In addition, genetic variants within the gene have been associated with MI in case-control settings, producing inconsistent results.

METHODS AND RESULTS

The MEF2A gene was sequenced in MI patients from 23 MI families (> or =5 affected members per family), but no mutation was identified in any of these extended families. Moreover, the Pro279Leu variant in exon 7 was analyzed in 1181 unrelated MI patients with a positive family history for MI/CAD, in 533 patients with sporadic MI, and in 2 control populations (n=1021 and n=1055), showing no evidence for association with MI/CAD. In addition, a (CAG)n repeat in exon 11 was genotyped in 543 sporadic MI patients and in 1190 controls without evidence for association with MI. Finally, analyzing 11 single-nucleotide polymorphisms from the GeneChip Mapping 500K Array, genotyped in 1644 controls and 753 cases, failed to provide evidence for association (region-wide P=0.23).

CONCLUSIONS

Studying independent samples of >1700 MI patients, 2 large control populations, and multiple families with apparently mendelian inheritance of the disease, we found no evidence for any linkage or association signal in the MEF2A gene.