Premature myocardial infarction novel susceptibility locus on chromosome 1P34-36 identified by genomewide linkage analysis

Genetics of atherosclerosis

Atherosclerosis, the primary cause of coronary artery disease (CAD) and stroke, is a disorder with multiple genetic and environmental contributions. Genetic-epidemiologic studies have identified a surprisingly long list of genetic and nongenetic risk factors for CAD. However, such studies indicate that family history is the most significant independent risk factor (15, 52, 77). Many Mendelian disorders associated with atherosclerosis, such as familial hypercholesterolemia (FH), have been characterized, but they explain only a small percentage of disease susceptibility (although a substantial fraction of early CAD). Most cases of myocardial infarction (MI) and stroke result from the interactions of multiple genetic and environmental factors, none of which can cause disease by itself. Successful discovery of these genetic factors will require using complementary approaches with animal models, large-scale human genetic studies, and functional experiments. This review emphasizes the common, complex forms of CAD.

Transcription factor MEF2A mutations in patients with coronary artery disease

Coronary artery disease (CAD), including its most serious complication myocardial infraction (MI), is the leading cause of death in the US and developed countries. We recently discovered that a seven-amino acid deletion in MEF2A, a transcription factor with a high level of expression in the endothelium of coronary arteries, co-segregates with CAD/MI in one family, and it suppresses transcription activation activity of MEF2A by a dominant-negative mechanism. In this study, we used single-strand conformation polymorphism and DNA sequence analyses to identify mutations in MEF2A in 207 independent CAD/MI patients and 191 controls with normal angiograms. We identified three novel mutations in exon 7 of MEF2A in four of 207 CAD/MI patients (1.93%). No mutations were detected in the 191 controls. The mutations identified here include N263S identified in two independent CAD patients, P279L in one patient and his father with the diagnosis of CAD and G283D in one patient. These mutations are clustered within or close to the major transcriptional activation domain of MEF2A. They significantly reduce the transcriptional activation activity of MEF2A and act by a loss-of-function mechanism. The gene carriers with loss-of-function mutations appear to be associated with less severe CAD. These results suggest that CAD/MI can result from a spectrum of MEF2A transcription dysfunctions ranging from loss-of-function to dominant-negative suppression and that a significant percent of the CAD/MI population (1.93%) may carry mutations in MEF2A, although further definition of the prevalence of MEF2A mutations is warranted.

A genomewide scan for early-onset coronary artery disease in 438 families: the GENECARD Study

A family history of coronary artery disease (CAD), especially when the disease occurs at a young age, is a potent risk factor for CAD. DNA collection in families in which two or more siblings are affected at an early age allows identification of genetic factors for CAD by linkage analysis. We performed a genomewide scan in 1,168 individuals from 438 families, including 493 affected sibling pairs with documented onset of CAD before 51 years of age in men and before 56 years of age in women. We prospectively defined three phenotypic subsets of families: (1) acute coronary syndrome in two or more siblings; (2) absence of type 2 diabetes in all affected siblings; and (3) atherogenic dyslipidemia in any one sibling. Genotypes were analyzed for 395 microsatellite markers. Regions were defined as providing evidence for linkage if they provided parametric two-point LOD scores >1.5, together with nonparametric multipoint LOD scores >1.0. Regions on chromosomes 3q13 (multipoint LOD = 3.3; empirical P value <.001) and 5q31 (multipoint LOD = 1.4; empirical P value <.081) met these criteria in the entire data set, and regions on chromosomes 1q25, 3q13, 7p14, and 19p13 met these criteria in one or more of the subsets. Two regions, 3q13 and 1q25, met the criteria for genomewide significance. We have identified a region on chromosome 3q13 that is linked to early-onset CAD, as well as additional regions of interest that will require further analysis. These data provide initial areas of the human genome where further investigation may reveal susceptibility genes for early-onset CAD.