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Gene Study Probes 7 Common Diseases

Disease Genes Found to Be Risk Factors, Not Fates
By
WebMD Health News
Reviewed by Louise Chang, MD

researcher

June 6, 2007 - An analysis of 17,000 Britons has linked specific gene variants to bipolar disorder, high blood pressure, coronary artery disease, Crohn's disease, type 1 and type 2 diabetes, and rheumatoid arthritis.

The treasure-trove of genomic data comes from a consortium of 50 British groups called the Wellcome Trust Case Control Consortium, or WTCCC.

"The field of human genetics has hoped for a decade or more to discover these genetic variants and how they interact and affect risk of disease," WTCCC Chairman Peter Donnelly, PhD, of the University of Oxford, said at a news conference.

The study already has yielded important new insights into the root causes of these seven common diseases.

The most important of these insights is that having a gene variant linked to disease doesn't mean you are fated to get that disease. It only means you're at higher risk of the disease -- or at lower risk, as some of the genes are linked to protection against disease.

"These are risk factors, rather than genetics predicting who will get a disease," Donnelly said. "There is a large other part of the story: people's diets, and lifestyles, and so on."

The study analyzed the genomes of about 2,000 patients with each disease and compared their genetic codes to a shared group of about 3,000 healthy individuals. For each individual in the study, researchers analyzed 500,000 areas of their genomes.

"If you think of the human genome as a very long road where you are trying to find something in the dark, previously we were able to turn the lights on only in a very few places," Donnelly said. "It turns out that by turning on half a million lights along the genome, as we have done, you get to see a very large proportion of the variation that is there."

The Genetics of Common Diseases

Why look for genes linked to common diseases? The main reason is that very little is known about what causes these diseases.

"Genetics gives us a completely new way of looking at the problem," Donnelly said. "If we can understand the genetic basis of the disease, it gives us insight into what goes wrong and what triggers the disease. And then we can move on to develop new treatments and, potentially, new drug therapies."

If the diseases are common, so are the genes that affect them. Nearly everybody -- at least everybody in Britain -- carries one or more of the genes identified in the study.

"This is very different from rare mutations that always cause disease; the genes we have discovered are very common. All of us have them; all of us have more or less susceptibility to diabetes, for example," University of Cambridge researcher John A. Todd, PhD, said at the news conference. "This means we can study healthy people who haven't developed diabetes yet, and see what factors alter those characteristics.

"That is what is exciting about common genes," Todd added. "These genes are completely dominated by environmental effects. Now we can actually work out what environmental factors are altering the common genetic characteristics."

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