'Traditionally, when we have looked for genetic risk factors for, say, heart disease, we have assumed that the blood will tell us what's happening in the tissue. It now seems this is simply not the case. From a genetic perspective, therapeutic implications aside, the observation that not all cells are the same is extremely important. That's the bottom line,' he said.

'Genome-wide association studies were introduced with enormous hype several years ago, and people expected tremendous breakthroughs. They were going to draw blood samples from thousands or hundreds of thousands of individuals, and find the genes responsible for disease.

'Unfortunately, the reality of these studies has been very disappointing, and our discovery certainly could explain at least one of the reasons why,' added Gottlieb.

Co-researcher Morris Schweitzer said: 'This (discovery) will probably have repercussions for vascular disease in general. We have not yet looked at coronary or cerebral arteries, but I would suspect that this mutation may be present across the board.'

He said their discovery may lead to new treatments for vascular disease in the near future.

'The timeline might be five to 10 years. This is the first step, but it's an important step,' said the Canadian researcher.

The study appears in the July issue of the journal Human Mutation.