A Common Allele on Chromosome 9 Associated With Coronary Heart Disease

Coronary heart disease (CHD), the commonest cause of death worldwide, is highly heritable, but the DNA sequence variations associated with elevated cardiovascular risk are largely unknown. The investigators planned a genome-wide associational study based on 100,000 single nucleotide polymorphisms and involving 3 sequential case-control comparisons made at a nominal significance threshold of P < 0.025. The study population included more than 23,000 participants from 4 Caucasian populations. Cases had severe, premature CHD starting before age 60 years and leading to coronary artery revascularization. Controls were healthy Caucasian men over age 65 and women over age 70 who lacked symptoms and a history of CHD. Individuals with diabetes or hypercholesterolemia were excluded. A 58-kilobase interval on chromosome 9p21 was consistently associated with CHD. The interval is near the CDKN2A and CDKN2B genes. It contains no annotated genes and is not associated with established CHD risk factors such as diabetes, plasma lipoproteins, or hypertension. Between 20% and 25% of Caucasians are homozygous for the risk allele, and they have an approximately 30%–40% increased risk of CHD. Mechanisms for the association between the risk allele and CHD remain incompletely understood. The allele might promote the development of atherosclerotic plaque, augment thrombogenesis, or increase the tendency of plaques to rupture. The association persisted after controlling for numerous possible confounding factors including age, gender, plasma lipid levels, blood pressure, diabetes, and plasma levels of C-reactive protein. The researchers believe that the effect of the risk allele on chromosome 9 on CHD is not mediated by established risk factors for cardiovascular disease. The present findings support the use of the whole-genome association approach for studying conditions as complex as CHD.