MEF2A sequence variants and coronary artery disease: a change of heart?

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.

Plasma homocysteine and the genetics of cardiovascular disease

Cardiovascular disease (CVD) is extremely complex. It results from the interaction of many genetic and environmental factors. Several studies have demonstrated its genetic basis, estimating a heritability of approximately 60%. In the last 5 years, at least 19 genome-wide explorations for genes related to CVD have been undertaken, but none has yet unequivocally demonstrated a causal relationship with the disease. One method that can be used to find the causative genes is analyzing intermediate genetic phenotypes or risk factors, such as plasma homocysteine (Hcy). A recent genome-wide quantitative-trait-linkage analysis of Hcy plasma levels has found a previously unsuspected gene as the major genetic determinant of this risk factor. It codes for the enzyme nicotinamide N-methyltransferase, and this gene is now a candidate gene that explains a portion of the genetic basis of CVD. If confirmed, this finding will probably influence future research on the mechanisms underlying atherosclerosis and CVD, as well as other complex diseases related to plasma Hcy levels, such as Alzheimer's disease and osteoporosis.