A genome-wide search for susceptibility loci to human essential hypertension.

We undertook a systematic search of the entire human genome with the affected sibling-pair model to identify major susceptibility loci to essential hypertension. Affected nuclear families (n=263) were recruited and divided according to definite or probable genetic contribution to hypertension depending on number of hypertensive siblings. The largest nuclear families were first screened with a set of microsatellite markers. Regions on the genome with P<0.05 were tested against the second set of smaller families. An exclusion map was generated to identify regions in which hypertension-causing genes are unlikely to reside. Sibling-pair linkage analysis identified a single locus on chromosome 11q (P<0.004) in the first pass. A second pass with nuclear families that had only affected sibling pairs was, as expected, insufficient to support linkage to 11q. Multipoint exclusion-linkage analysis showed that 3 genetic loci are necessary to explain familial aggregation of essential hypertension. Our preliminary findings suggest that no single region within the human genome contains genes with a major contribution to essential hypertension. We show that the disease is indeed polygenic, with each gene providing a relatively small risk. Our exclusion map will help future investigators to concentrate on areas likely to contain these genes. The region on chromosome 11 is the first to point to a new candidate gene for hypertension that has arisen out of a genome search, but replication of these results at a higher significance is necessary before positional cloning can be justified.

A common variant of the endothelial nitric oxide synthase (Glu298-->Asp) is a major risk factor for coronary artery disease in the UK.

BACKGROUND: Endothelium-derived nitric oxide (NO) is synthesised from L-arginine by endothelial nitric oxide synthase (eNOS) encoded by the NOS 3 gene on chromosome 7. Because reduced NO synthesis has been implicated in the development of coronary atherosclerosis, which has a heritable component, we hypothesised that polymorphisms of NOS 3 might be associated with increased susceptibility to this disorder. METHODS AND RESULTS: Single-strand conformation polymorphism analysis of NOS 3 identified a G-->T polymorphism in exon 7 of the gene which encodes a Glu-->Asp amino acid substitution at residue 298 of eNOS. We investigated the relationship between this Glu(298)-->Asp variant and atherosclerotic coronary artery disease (CAD) using 2 independent case-controlled studies. In the first study (CHAOS), cases consisted of 298 unrelated patients with positive coronary angiograms and controls were 138 unrelated healthy individuals ascertained through a population health screen. In the second study (CHAOS II), the cases were 249 patients with recent myocardial infarction (MI), and a further 183 unrelated controls. There was an excess of homozygotes for the Asp298 variant among patients with angiographic CAD, and among patients with recent MI when compared with their respective controls (35.9% versus 10.2%, P<0.0001 in CHAOS, and 18.1% versus 8.7%, P<0.02 in CHAOS II). In comparison to Glu(298) homozygotes, homozygosity for Asp(298) was associated with an odds ratio of 4.2 (95% CI, 2.3 to 7.9) for angiographic CAD and 2.5 (95% CI, 1.3 to 4.2) for MI. CONCLUSIONS: Homozygosity for a common NOS 3 polymorphism (894 G-->T) which encodes a Glu298-->Asp amino acid substitution in eNOS is a risk factor for angiographic CAD and recent MI in this population.