Transcription factor MEF2A mutations in patients with 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.

Potential Mechanism and Effects of Different Selenium Sources and Different Effective Microorganism Supplementation Levels on Growth Performance, Meat Quality, and Muscle Fiber Characteristics of Three-Yellow Chickens

A trial was conducted to investigate the effects of different Se sources, including sodium selenite (S-Se) and selenium yeast (Y-Se) and different effective microorganism (EM) addition levels on growth performance, meat quality, and muscle fiber characteristics of three-yellow chickens and its potential mechanism. A total of 400 birds were randomly distributed into 4 groups (S-Se, S-Se + EM, Y-Se, and Y-Se + EM groups) consisting of a 2 × 2 factorial arrangement. The main factors were the source of Se (I_Se = inorganic Se: 0.2 mg/kg S-Se; O_Se = organic Se: 0.2 mg/kg Y-Se) and the level of EM (H_EMB = high EM: 0.5% EM; Z_EMB = low EM: 0% EM). Each treatment had 5 replicates and each replicate consisted of 20 broiler chickens. The trial lasted for 70 days. The results showed that, in breast muscle, the broiler chickens fed O_Se source decreased the pH_24h, drip loss, shear force, perimeter, cross-sectional area, and diameter, but increased the a24h* and density compared with the broiler chickens fed I_Se source (p < 0.05); broiler chickens supplied with H_EMB level decreased the cross-sectional area and diameter, but increased the pH_24h, a24h,* and density compared with the broiler chickens supplied with Z_EMB level (p < 0.05). In thigh muscle, O_Se source and H_EMB level also could improve the meat quality and change muscle fiber characteristics of broiler chickens (p < 0.05). Meat quality was correlated with the muscle fiber characteristics (p < 0.05). O_Se source and H_EMB level could regulate the expression levels of muscle fiber-relative genes in the breast and thigh muscles (p < 0.05). In conclusion, O_Se source and H_EMB level could improve the meat quality of the breast and thigh muscles of three-yellow chickens by changing the muscle fiber characteristics, and they changed the muscle fiber characteristics by regulating the expression levels of muscle fiber-relative genes.

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.

15q26 deletion in a patient with congenital heart defect, growth restriction and intellectual disability: case report and literature review

Background

15q26 deletion is a relatively rare chromosomal disorder, and it is described only in few cases. Patients with this aberration show many signs and symptoms, particularly pre- and postnatal growth restriction, developmental delay, microcephaly, intellectual disability and various congenital malformations.

Case presentation

We report on a girl, 4 years old, of consanguineous parents, with a 15q26 deletion. Clinical manifestations included failure to thrive, developmental delay, microcephaly, dysmorphic facies with broad forehead, hypertelorism, narrowed eyelid slits and protruding columella. The patient also showed skeletal abnormalities, especially clinodactyly of the 5th finger, varus equine right foot and left club foot. Additionally, she had teething delay and divergent strabismus. Heart ultrasound displayed two atrial septal defects with left-to-right shunt, enlarging the right cavities. Routine cytogenetic analysis revealed a shortened 15q chromosome. Subsequent array analysis disclosed a terminal 9.15 Mb deletion at subband 15q26.1-q26.3. Four candidate genes associated with 15q26 deletion phenotype were within the deleted region, i.e. IGF1R, NR2F2, CHD2 and MEF2A.

Conclusion

We report on an additional case of 15q26 monosomy, characterized by array-CGH. Molecular cytogenetic analysis allowed us to identify the exact size of the deletion, and four candidate genes for genotype-phenotype correlation. 15q26 monosomy should be considered when growth retardation is associated with hearing anomalies and congenital heart defect, especially atrioventricular septal defects (AVSDs) and/or aortic arch anomaly (AAA).

Inflammation as a risk factor for stroke in atrial fibrillation: data from a microarray data analysis

Objective

Stroke is a severe complication of atrial fibrillation (AF). We aimed to discover key genes and microRNAs related to stroke risk in patients with AF using bioinformatics analysis.

Methods

GSE66724 microarray data, including peripheral blood samples from eight patients with AF and stroke and eight patients with AF without stroke, were downloaded from the Gene Expression Omnibus (GEO) database. Differentially expressed genes (DEGs) between AF patients with and without stroke were identified using the GEO2R online tool. Functional enrichment analysis was performed using the DAVID database. A protein–protein interaction (PPI) network was obtained using the STRING database. MicroRNAs (miRs) targeting these DEGs were obtained from the miRNet database. A miR–DEG network was constructed using Cytoscape software.

Results

We identified 165 DEGs (141 upregulated and 24 downregulated). Enrichment analysis showed enrichment of certain inflammatory processes. The miR–DEG network revealed key genes, including MEF2A, CAND1, PELI1, and PDCD4, and microRNAs, including miR-1, miR-1-3p, miR-21, miR-21-5p, miR-192, miR-192-5p, miR-155, and miR-155-5p.

Conclusion

Dysregulation of certain genes and microRNAs involved in inflammation may be associated with a higher risk of stroke in patients with AF. Evaluating these biomarkers could improve prediction, prevention, and treatment of stroke in patients with AF.

Detection and functional characterization of a novel MEF2A variation responsible for familial dilated cardiomyopathy

OBJECTIVES

Dilated cardiomyopathy (DCM) represents the most frequent form of cardiomyopathy, leading to heart failure, cardiac arrhythmias and death. Accumulating evidence convincingly demonstrates the crucial role of genetic defects in the pathogenesis of DCM, and over 100 culprit genes have been implicated with DCM. However, DCM is of substantial genetic heterogeneity, and the genetic determinants underpinning DCM remain largely elusive.

METHODS

Whole-exome sequencing and bioinformatical analyses were implemented in a consanguineous Chinese family with DCM. A total of 380 clinically annotated control individuals and 166 more DCM index cases then underwent Sanger sequencing analysis for the identified genetic variation. The functional characteristics of the variant were delineated by utilizing a dual-luciferase assay system.

RESULTS

A heterozygous variation in the MEF2A gene (encoding myocyte enhancer factor 2A, a transcription factor pivotal for embryonic cardiogenesis and postnatal cardiac adaptation), NM_001365204.1: c.718G>T; p. (Gly240*), was identified, and verified by Sanger sequencing to segregate with autosome-dominant DCM in the family with complete penetrance. The nonsense variation was neither detected in 760 control chromosomes nor found in 166 more DCM probands. Functional analyses revealed that the variant lost transactivation on the validated target genes MYH6 and FHL2, both causally linked to DCM. Furthermore, the variation nullified the synergistic activation between MEF2A and GATA4, another key transcription factor involved in DCM.

CONCLUSIONS

The findings firstly indicate that MEF2A loss-of-function variation predisposes to DCM in humans, providing novel insight into the molecular mechanisms of DCM and suggesting potential implications for genetic testing and prognostic evaluation of DCM patients.

Hematopoietic Stem Cell Transcription Factors in Cardiovascular Pathology

Transcription factors as multifaceted modulators of gene expression that play a central role in cell proliferation, differentiation, lineage commitment, and disease progression. They interact among themselves and create complex spatiotemporal gene regulatory networks that modulate hematopoiesis, cardiogenesis, and conditional differentiation of hematopoietic stem cells into cells of cardiovascular lineage. Additionally, bone marrow-derived stem cells potentially contribute to the cardiovascular cell population and have shown potential as a therapeutic approach to treat cardiovascular diseases. However, the underlying regulatory mechanisms are currently debatable. This review focuses on some key transcription factors and associated epigenetic modifications that modulate the maintenance and differentiation of hematopoietic stem cells and cardiac progenitor cells. In addition to this, we aim to summarize different potential clinical therapeutic approaches in cardiac regeneration therapy and recent discoveries in stem cell-based transplantation.

Landscape of DNA binding signatures of myocyte enhancer factor-2B reveals a unique interplay of base and shape readout

Myocyte enhancer factor-2B (MEF2B) has the unique capability of binding to its DNA target sites with a degenerate motif, while still functioning as a gene-specific transcriptional regulator. Identifying its DNA targets is crucial given regulatory roles exerted by members of the MEF2 family and MEF2B's involvement in B-cell lymphoma. Analyzing structural data and SELEX-seq experimental results, we deduced the DNA sequence and shape determinants of MEF2B target sites on a high-throughput basis in vitro for wild-type and mutant proteins. Quantitative modeling of MEF2B binding affinities and computational simulations exposed the DNA readout mechanisms of MEF2B. The resulting binding signature of MEF2B revealed distinct intricacies of DNA recognition compared to other transcription factors. MEF2B uses base readout at its half-sites combined with shape readout at the center of its degenerate motif, where A-tract polarity dictates nuances of binding. The predominant role of shape readout at the center of the core motif, with most contacts formed in the minor groove, differs from previously observed protein-DNA readout modes. MEF2B, therefore, represents a unique protein for studies of the role of DNA shape in achieving binding specificity. MEF2B-DNA recognition mechanisms are likely representative for other members of the MEF2 family.

Myocyte enhancer factor 2A delays vascular endothelial cell senescence by activating the PI3K/p-Akt/SIRT1 pathway

Myocyte enhancer factor 2A (MEF2A) dysfunction is closely related to the occurrence of senile diseases such as cardiocerebrovascular diseases, but the underlying molecular mechanism is unclear. Here, we studied the effects of MEF2A on the senescent phenotype of vascular endothelial cells (VEC) and downstream signaling pathway, and the association between plasma MEF2A levels and coronary artery disease (CAD). Results showed that MEF2A silencing promoted cell senescence and down-regulated PI3K/p-AKT/Sirtuin 1 (SIRT1) expression. MEF2A overexpression delayed cell senescence and up-regulated PI3K/p-AKT/SIRT1. Hydrogen peroxide (H₂O₂) treatment induced cellular senescence and down-regulated the expression of MEF2A and PI3K/p-AKT/SIRT1. MEF2A overexpression inhibited cellular senescence and the down-regulation of PI3K/p-AKT/SIRT1 induced by H₂O₂. Further study revealed that MEF2A directly up-regulated the expression of PIK3CA and PIK3CG through MEF2 binding sites in the promoter region. Pearson correlation and logistic regression analysis showed that the plasma level of MEF2A was negatively correlated with CAD, and with age in the controls. These results suggested that MEF2A can directly up-regulate PI3K gene expression, and one of the molecular mechanisms of delaying effect of MEF2A on VEC cell senescence was SIRT1-expression activation through the PI3K/p-Akt pathway. Moreover, the plasma MEF2A levels may be a potential biomarker for CAD risk prediction.

Analysis of Differentially Expressed Genes in Coronary Artery Disease by Integrated Microarray Analysis

Coronary artery disease (CAD) is a major cause of end-stage cardiac disease. Although profound efforts have been made to illuminate the pathogenesis, the molecular mechanisms of CAD remain to be analyzed. To identify the candidate genes in the advancement of CAD, microarray dataset GSE23766 was downloaded from the Gene Expression Omnibus database. The differentially expressed genes (DEGs) were identified, and pathway and gene ontology (GO) enrichment analyses were performed. The protein-protein interaction network was constructed and the module analysis was performed using the Biological General Repository for Interaction Datasets (BioGRID) and Cytoscape. Additionally, target genes-miRNA regulatory network and target genes-TF regulatory network were constructed and analyzed. There were 894 DEGs between male human CAD samples and female human CAD samples, including 456 up regulated genes and 438 down regulated genes. Pathway enrichment analyses revealed that DEGs (up and down regulated) were mostly enriched in the superpathway of steroid hormone biosynthesis, ABC transporters, oxidative ethanol degradation III and Complement and coagulation cascades. Similarly, geneontology enrichment analyses revealed that DEGs (up and down regulated) were mostly enriched in the forebrain neuron differentiation, filopodium membrane, platelet degranulation and blood microparticle. In the PPI network and modules (up and down regulated), MYC, NPM1, TRPC7, UBC, FN1, HEMK1, IFT74 and VHL were hub genes. In the target genes-miRNA regulatory network and target genes—TF regulatory network (up and down regulated), TAOK1, KHSRP, HSD17B11 and PAH were target genes. In conclusion, the pathway and GO ontology enriched by DEGs may reveal the molecular mechanism of CAD. Its hub and target genes, MYC, NPM1, TRPC7, UBC, FN1, HEMK1, IFT74, VHL, TAOK1, KHSRP, HSD17B11 and PAH were expected to be new targets for CAD. Our finding provided clues for exploring molecular mechanism and developing new prognostics, diagnostic and therapeutic strategies for CAD.

MEF2A alters the proliferation, inflammation-related gene expression profiles and its silencing induces cellular senescence in human coronary endothelial cells

Background

Myocyte enhancer factor 2A (MEF2A) plays an important role in cell proliferation, differentiation and survival. Functional deletion or mutation in MEF2A predisposes individuals to cardiovascular disease mainly caused by vascular endothelial dysfunction. However, the effect of the inhibition of MEF2A expression on human coronary artery endothelial cells (HCAECs) is unclear. In this study, expression of MEF2A was inhibited by specific small interference RNA (siRNA), and changes in mRNA profiles in response to MEF2A knockdown were analyzed using an Agilent human mRNA array.

Results

Silencing of MEF2A in HCAECs accelerated cell senescence and suppressed cell proliferation. Microarray analysis identified 962 differentially expressed genes (DEGs) between the MEF2A knockdown group and the negative control group. Annotation clustering analysis showed that the DEGs were preferentially enriched in gene ontology (GO) terms and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways related to proliferation, development, survival, and inflammation. Furthermore, 61 of the 578 downregulated DEGs have at least one potential MEF2A binding site in the proximal promoter and were mostly enriched in the GO terms “reproduction” and “cardiovascular.” The protein–protein interaction network analyzed for the downregulated DEGs and the DEGs in the GO terms “cardiovascular” and “aging” revealed that PIK3CG, IL1B, IL8, and PRKCB were included in hot nodes, and the regulation of the longevity-associated gene PIK3CG by MEF2A has been verified at the protein level, suggesting that PIK3CG might play a key role in MEF2A knockdown induced HCAEC senescence.

Conclusions

MEF2A knockdown accelerates HCAEC senescence, and the underlying molecular mechanism may be involved in down-regulation of the genes related with cell proliferation, development, inflammation and survival, in which PIK3CG may play a key role.

Electronic supplementary material

The online version of this article (10.1186/s12867-019-0125-z) contains supplementary material, which is available to authorized users.

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.

Mapping genetic variants for cranial vault shape in humans

The shape of the cranial vault, a region comprising interlocking flat bones surrounding the cerebral cortex, varies considerably in humans. Strongly influenced by brain size and shape, cranial vault morphology has both clinical and evolutionary relevance. However, little is known about the genetic basis of normal vault shape in humans. We performed a genome-wide association study (GWAS) on three vault measures (maximum cranial width [MCW], maximum cranial length [MCL], and cephalic index [CI]) in a sample of 4419 healthy individuals of European ancestry. All measures were adjusted by sex, age, and body size, then tested for association with genetic variants spanning the genome. GWAS results for the two cohorts were combined via meta-analysis. Significant associations were observed at two loci: 15p11.2 (lead SNP rs2924767, p = 2.107 × 10⁻⁸) for MCW and 17q11.2 (lead SNP rs72841279, p = 5.29 × 10⁻⁹) for MCL. Additionally, 32 suggestive loci (p < 5x10^-6) were observed. Several candidate genes were located in these loci, such as NLK, MEF2A, SOX9 and SOX11. Genome-wide linkage analysis of cranial vault shape in mice (N = 433) was performed to follow-up the associated candidate loci identified in the human GWAS. Two loci, 17q11.2 (c11.loc44 in mice) and 17q25.1 (c11.loc74 in mice), associated with cranial vault size in humans, were also linked with cranial vault size in mice (LOD scores: 3.37 and 3.79 respectively). These results provide further insight into genetic pathways and mechanisms underlying normal variation in human craniofacial morphology.

Generation of a mef2aa:EGFP transgenic zebrafish line that expresses EGFP in muscle cells

Transgenesis is an important tool for exploring gene expression and function. The myocyte enhancer factor 2a (mef2a) gene encodes a member of the Mef2 protein family that is involved in vertebrate skeletal, cardiac, and smooth muscle development and differentiation during myogenesis. According to studies on human and animal models, mef2a is highly expressed in the heart and somites. To explore the potential of mef2a as a tool for selective labeling of muscle cells in living zebrafish embryos, we constructed a transgene mef2aa:EGFP to induce the expression of green fluorescent protein (GFP) under the control of mef2a promoter. A ~2-kb DNA fragment, upstream of the translational start site of mef2aa, was identified to drive muscle-specific expression of EGFP in zebrafish embryos. Interestingly, the cranial muscles, abductor muscle, and adductor muscle were clearly labeled with EGFP in the established line Tg(mef2aa:EGFP) ^ntu803 . In addition, we showed that mef2aa mRNA was highly present in adult zebrafish heart, but not the skeleton muscle, whereas it was expressed in both embryonic heart and myotome, suggesting that mef2a is vital to the function of adult heart in vertebrates.

Genome-wide methylation profiles in coronary artery ectasia

Coronary artery ectasia (CAE) is a disease characterized by abnormally dilated coronary arteries. The mechanism of CAE remains unclear, and its treatment is limited. Previous studies have shown that risk factors for CAE were related to changes in DNA methylation. However, no systematic investigation of methylation profiles has been performed. Therefore, we compared methylation profiles between 12 CAE patients and 12 propensity-matched individuals with normal coronary arteries using microarrays. Wilcoxon's rank sum tests revealed 89 genes with significantly different methylation levels (P<0.05 and Δβ > |0.1|). Functional characterization using the DAVID database and gene set enrichment analysis indicated that these genes were involved in immune and inflammatory responses. Of these genes 6 were validated in 29 CAE patients and 87 matched individuals with CAE, using pyro-sequencing. TLR6 and NOTCH4 showed significant differences in methylation between the two groups, and lower protein levels of toll-like receptor 6 (TLR6) were detected in CAE patients. In conclusion, this genome-wide analysis of methylation profiles in CAE patients showed that significant changes in both methylation and expression of TLR6 deserve further study to elucidate their roles in CAE.

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.

Cross-Tissue Regulatory Gene Networks in Coronary Artery Disease

Inferring molecular networks can reveal how genetic perturbations interact with environmental factors to cause common complex diseases. We analyzed genetic and gene expression data from seven tissues relevant to coronary artery disease (CAD) and identified regulatory gene networks (RGNs) and their key drivers. By integrating data from genome-wide association studies, we identified 30 CAD-causal RGNs interconnected in vascular and metabolic tissues, and we validated them with corresponding data from the Hybrid Mouse Diversity Panel. As proof of concept, by targeting the key drivers AIP, DRAP1, POLR2I, and PQBP1 in a cross-species-validated, arterial-wall RGN involving RNA-processing genes, we re-identified this RGN in THP-1 foam cells and independent data from CAD macrophages and carotid lesions. This characterization of the molecular landscape in CAD will help better define the regulation of CAD candidate genes identified by genome-wide association studies and is a first step toward achieving the goals of precision medicine.

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.

Association Study between Coronary Artery Disease and rs1333049 and rs10757274 Polymorphisms at 9p21 Locus in South-West Iran

Objective

Coronary artery disease (CAD) is a multi-factorial and heterogenic disease with atherosclerosis plaques formation in internal wall of coronary artery. Plaque formation results to limitation of the blood reaching to myocardium leading to appearance of some problems, such as ischemia, sudden thrombosis veins and myocardial infarction (MI). Several environmental and genetic factors are involved in prevalence and incident of CAD as follows: hypertension, high low density lipoprotein-cholesterol (LDL-C), age, diabetes mellitus, family history of early-onset heart disease and smoking. According to genome wide association studies (GWAS), five polymorphisms in the 9p21 locus seem to be associated with the CAD. We aimed to evaluate the remarkable association of two polymorphisms at 9p21 locus, rs1333049 and rs10757274, with CAD.

Materials and Methods

This experimental study was conducted in Golestan, Aria Hospitals and Genetics Lab of Shahid Chamran University in the city of Ahvaz, Iran, in 2010- 2011. The collected blood samples belonging to 170 CAD patients (case group) and 100 healthy individuals (control group) were analyzed by tetra-primer amplification refractory mutation system (ARMS)-polymerase chain reaction (PCR) technique. The results were analyzed using software package used for statistical analysis (SPSS; SPSS Inc., USA) version 16. A value of p<0.05 and an odd ratio (OR) with 95% confidence intervals (CI) were considered significant.

Results

The frequencies of CC, CG and GG genotypes for rs1333049 polymorphism in patients were 18.2, 65.3 and 16.5%, while in controls, the related values were 25, 67 and 8%, respectively. GG genotypes of rs1333049 polymorphism in CAD patients were more than control cases (OR: 0.354, 95%CI: 0.138-0.912, p=0.032). The frequencies of AA, AG and GG genotypes for rs10757274 in CAD patients were 8.2, 58.3 and 33.5%, while in controls, the related values were 35, 63 and 2%, respectively. GG Genotype in rs10757274 polymorphism in CAD patients was found more than control cases (OR: 0.014, 95% CI: 0.003 -0.065, p=0.0001).

Conclusion

The rs1333049 polymorphism at 9p21 locus shows a weak association with CAD, whereas rs10757274 polymorphism reveals a significant association with CAD. These variants may help the identification of patients with increased risk for coronary artery disease.

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.

The molecular characterization and temporal-spatial expression of myocyte enhancer factor 2 genes in the goat and their association with myofiber traits

The myocyte enhancer factor-2 (MEF2) gene family in vertebrates includes MEF2A, MEF2B, MEF2C, and MEF2D, which have important functions in the regulation of muscular growth and development. To investigate their temporal-spatial expression and functions in the goat, these genes were cloned (accession nos. JN967621-24) and their expression patterns characterized at five postnatal stages (3, 30, 60, 90, and 120days). Association analysis was then applied regarding MEF2 expression levels and myofiber diameter and density. MEF2B was shown to be weakly homologous with other species, the distant branches with other members and the lowest expression levels, suggesting that it is distinct from other family members. Expression of the other three MEF2 genes was widely distributed, but this was largely accumulated in the skeletal muscle and myocardium compared with the viscera at all developmental stages. MEF2A and MEF2D expression levels were higher overall than MEF2B and MEF2C in six tissues, and were significantly positively correlated with the myofiber diameter of the longissimus dorsi. These findings suggest that goat MEF2 genes mainly function in the skeletal muscle and myocardium, and that MEF2A and MEF2D are likely to effectively promote muscular growth and development during postnatal stages. MEF2A expression was highest in the myocardium, where MEF2C expression increased with age, implying that both gene products are related to the growth and development of postnatal myocardium.

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.

Reactivation of fetal splicing programs in diabetic hearts is mediated by protein kinase C signaling

Diabetic cardiomyopathy is one of the complications of diabetes that eventually leads to heart failure and death. Aberrant activation of PKC signaling contributes to diabetic cardiomyopathy by mechanisms that are poorly understood. Previous reports indicate that PKC is implicated in alternative splicing regulation. Therefore, we wanted to test whether PKC activation in diabetic hearts induces alternative splicing abnormalities. Here, using RNA sequencing we identified a set of 22 alternative splicing events that undergo a developmental switch in splicing, and we confirmed that splicing reverts to an embryonic pattern in adult diabetic hearts. This network of genes has important functions in RNA metabolism and in developmental processes such as differentiation. Importantly, PKC isozymes α/β control alternative splicing of these genes via phosphorylation and up-regulation of the RNA-binding proteins CELF1 and Rbfox2. Using a mutant of CELF1, we show that phosphorylation of CELF1 by PKC is necessary for regulation of splicing events altered in diabetes. In summary, our studies indicate that activation of PKCα/β in diabetic hearts contributes to the genome-wide splicing changes through phosphorylation and up-regulation of CELF1/Rbfox2 proteins. These findings provide a basis for PKC-mediated cardiac pathogenesis under diabetic conditions.

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.

Genetic susceptibility to atherosclerosis

Atherosclerosis is a complex multifocal arterial disease involving interactions of multiple genetic and environmental factors. Advances in techniques of molecular genetics have revealed that genetic ground significantly influences susceptibility to atherosclerotic vascular diseases. Besides further investigations of monogenetic diseases, candidate genes, genetic polymorphisms, and susceptibility loci associated with atherosclerotic diseases have been identified in recent years, and their number is rapidly increasing. This paper discusses main genetic investigations fields associated with human atherosclerotic vascular diseases. The paper concludes with a discussion of the directions and implications of future genetic research in arteriosclerosis with an emphasis on prospective prediction from an early age of individuals who are predisposed to develop premature atherosclerosis as well as to facilitate the discovery of novel drug targets.

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.

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.

Lack of association between endothelin-1 gene variants and myocardial infarction

AIM

Endothelin-1 (ET-1) promotes vasoconstriction and cell proliferation, and has been implicated in hypertension and coronary artery disease. Our aim was to analyse the role of the ET-1 gene (EDN1) in the risk for atherosclerosis/myocardial infarction (MI) in a population with smoking as the prevalent risk factor.

METHODS

The study included 316 patients with early onset MI (<55 years old). All were male with at least one diseased coronary vessel. Denaturing high performance liquid chromatography (DHPLC), single-strand conformation analysis (SSCA), and direct sequencing were used to search for DNA variants in the five EDN1 exons and the promoter region. To determine the association of EDN1 polymorphisms with MI, we genotyped the patients and controls (n=350) and compared the allele and genotype frequencies between groups.

RESULTS

We found six common nucleotide changes: -1394 (T/G) and -974 C/A (promoter), +120 ins/del A (exon 1, 5' UTR), 568 A/G (exon 3, E106E), 844 G/T (exon 5, K198N), and 1617 T/C (exon 5, 3' UTR). No rare EDN1-variants specific to the MIpatients were found. None of the EDN1 polymorphisms were significantly associated with early-onset MI in our population. The two promoter polymorphisms were in linkage disequilibrium with K198N, but no haplotype was associated with MI risk.

CONCLUSIONS

In our population, the EDN1 variation did not contribute to early-onset MI.

Novel roles of GATA1 in regulation of angiogenic factor AGGF1 and endothelial cell function

AGGF1 is an angiogenic factor, and its deregulation is associated with a vascular malformation consistent with Klippel-Trenaunay syndrome (KTS). This study defines the molecular mechanism for transcriptional regulation of AGGF1 expression. Transcription of AGGF1 starts at two nearby sites, -367 and -364 bp upstream of the translation start site. Analyses of 5'- and 3'-serial promoter deletions defined the core promoter/regulatory elements, including two repressor sites (from -1971 to -3990 and from -7521 to -8391, respectively) and two activator sites (a GATA1 consensus binding site from -295 to -300 and a second activator site from -129 to -159). Both the GATA1 site and the second activator site are essential for AGGF1 expression. A similar expression profile was found for GATA1 and AGGF1 in cells (including various endothelial cells) and tissues. Electrophoretic mobility shift assay and chromatin immunoprecipitation assays demonstrated that GATA1 was able to bind to the AGGF1 DNA in vitro and in vivo. Overexpression of GATA1 increased expression of AGGF1. We identified one rare polymorphism -294C>T in a sporadic KTS patient, which is located in the GATA1 site, disrupts binding of GATA1 to DNA, and abolishes the GATA1 stimulatory effect on transcription of AGGF1. Knockdown of GATA1 expression by siRNA reduced expression of AGGF1, and resulted in endothelial cell apoptosis and inhibition of endothelial capillary vessel formation and cell migration, which was rescued by purified recombinant human AGGF1 protein. These results demonstrate that GATA1 regulates expression of AGGF1 and reveal a novel role for GATA1 in endothelial cell biology and angiogenesis.

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.

Rapid recruitment of temporally distinct vascular gene sets by estrogen

Cardiovascular disease is the leading cause of mortality for both men and women in developed countries. The sex steroid hormone estrogen is required for normal vascular physiology. Estrogen functions by binding to intracellular estrogen receptors (ER), ERalpha and ERbeta, ligand-activated transcription factors that are expressed in both vascular endothelial and smooth muscle cells. We recently demonstrated that long-term (8 d) estrogen treatment in vivo in mice recruits distinct vascular gene sets mediated by ERalpha and ERbeta and that the promoters from these gene sets are enriched for binding sites of specific transcription factors, leading to the hypothesis that estrogen initiates a cascade of early transcriptional events that modulate gene expression in the vasculature. Here we test this hypothesis using gene expression profiling to examine initial transcriptional events (2-8 h) mediated by estrogen in blood vessels. Our data reveal that 1) estrogen regulates temporally distinct cascades of vascular gene expression, 2) initially, estrogen-mediated vascular gene repression predominates, 3) the earliest estrogen-recruited gene program is enriched in vascular transcription factors that can interact with binding sites present in estrogen-regulated vascular genes recruited subsequently, and 4) estrogen-regulated genes recruited next have specific functions, including lipid metabolism and cellular growth and proliferation that are potentially important for estrogen's known vascular functions. In summary, estrogen directly and rapidly recruits specific transcriptional factors that then propagate distinct cascades of gene expression. These data define the temporal recruitment of specific vascular genes by estrogen and enable further analysis of the mechanisms by which estrogen directly regulates vascular function.

Genetic variations of Mrf-2/ARID5B confer risk of coronary atherosclerosis in the Japanese population

A phenotypic change of smooth muscle cells (SMCs) is considered to be critical in the pathogenesis of atherosclerotic lesions such as coronary artery disease (CAD). Mrf-2/ARID5B, a member of the AT-rich interaction domain family of transcription factors, is highly expressed in the cardiovascular system and is believed to play essential roles in the phenotypic change of SMCs through its regulation of SMC differentiation. In addition, recent studies on gene-engineered mice suggested that this transcriptional factor is involved in obesity and adipogenesis, which are critical aspects for the pathogenesis of atherosclerosis. Thus, we hypothesized that genetic variations of the Mrf-2 gene might be associated with susceptibility to CAD. We investigated 11 common genetic variations of Mrf-2 to determine whether they were associated with susceptibility to CAD in 475 CAD subjects and 310 control subjects. The prevalence of homozygotes for the minor allele G of SNP4 (rs2893880) and minor allele G of SNP6 (rs7087507) were significantly more frequent in the control subjects than in patients with CAD (P=0.0002, rs2893880, P=0.0058, rs7087507). Four nearby SNPs (SNP4 to SNP7) (rs2893880, rs10740055, rs7087507 and rs10761600) showed almost complete linkage disequilibrium, and haplotype analysis revealed that the haplotype G (rs2893880)-C (rs10740055)-G (rs7087507)-A (rs10761600) was also significantly negatively associated with susceptibility to CAD (P=0.049). Moreover, these negative disease associations still existed after logistic regression analysis was taken into account to eliminate confounding conventional coronary risk factors. The results implicate possible disease relevance of the polymorphisms in the Mrf-2 gene with susceptibility to CAD. However, a larger scale prospective study is needed to clarify these findings.

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.

Future use of genomics in coronary artery disease

Coronary artery disease (CAD) remains the number one cause of death in industrialized countries despite our collective efforts to minimize attributable risk from known contributors to CAD such as hypertension, dyslipidemia, and smoking. In addition, clinical trials have consistently demonstrated a family history of coronary disease to be predictive for future cardiovascular events beyond that which would be explained by traditional risk factors. These findings support and have prompted widespread investigation into the genomic basis of CAD and myocardial infarction (MI). Recent advances in genotyping technology have allowed for easier identification and confirmation of susceptibility genes for complex traits across different cohorts via increased power of studies stemming from faster accrual of cases and control subjects and more precise genetic mapping. These technological advances have resulted in defining the genes contributing to a substantial or even majority of population-attributable risk for type 2 diabetes and age-related macular degeneration (AMD) cases. Similar progress in replicating novel susceptibility genes for CAD and specifically MI is now rapidly occurring, with a recent gene marker on chromosome 9p21 representing a highly significant and common variant susceptibility factor. With improved resequencing technology and better phenotypic characterization of our CAD cases and control subjects, we should achieve successes in gene identification and confirmation similar to diabetes and AMD, thereby allowing us to better quantify CAD risk earlier in life and institute more effective therapy reducing the individual propensity to develop CAD.

Genetic and genomic insights into the molecular basis of atherosclerosis

Atherosclerosis is a complex disease involving genetic and environmental risk factors, acting on their own or in synergy. Within the general population, polymorphisms within genes in lipid metabolism, inflammation, and thrombogenesis are probably responsible for the wide range of susceptibility to myocardial infarction, a fatal consequence of atherosclerosis. Genetic linkage studies have been carried out in both humans and mouse models to identify these polymorphisms. Approximately 40 quantitative trait loci for atherosclerotic disease have been found in humans, and approximately 30 in mice. Recently, genome-wide association studies have been used to identify atherosclerosis-susceptibility polymorphisms. Although discovering new atherosclerosis genes through these approaches remains challenging, the pace at which these polymorphisms are being found is accelerating due to rapidly improving bioinformatics resources and biotechnologies. The outcome of these efforts will not only unveil the molecular basis of atherosclerosis but also facilitate the discovery of drug targets and individualized medication against the disease.

Mef2s are required for thick filament formation in nascent muscle fibres

During skeletal muscle differentiation, the actomyosin motor is assembled into myofibrils, multiprotein machines that generate and transmit force to cell ends. How expression of muscle proteins is coordinated to build the myofibril is unknown. Here we show that zebrafish Mef2d and Mef2c proteins are required redundantly for assembly of myosin-containing thick filaments in nascent muscle fibres, but not for the earlier steps of skeletal muscle fibre differentiation, elongation, fusion or thin filament gene expression. mef2d mRNA and protein is present in myoblasts, whereas mef2c expression commences in muscle fibres. Knockdown of both Mef2s with antisense morpholino oligonucleotides or in mutant fish blocks muscle function and prevents sarcomere assembly. Cell transplantation and heat-shock-driven rescue reveal a cell-autonomous requirement for Mef2 within fibres. In nascent fibres, Mef2 drives expression of genes encoding thick, but not thin, filament proteins. Among genes analysed, myosin heavy and light chains and myosin-binding protein C require Mef2 for normal expression, whereas actin, tropomyosin and troponin do not. Our findings show that Mef2 controls skeletal muscle formation after terminal differentiation and define a new maturation step in vertebrate skeletal muscle development at which thick filament gene expression is controlled.