DNA Mutation Raises Heart Disease Risk In Whites
WASHINGTON (Reuters) - A hunt for genes has found that up to three quarters
of people of European descent have DNA that raises their risk for heart
disease — and these genes are close to a stretch of DNA linked to diabetes.
The findings, made by two independent groups of researchers, may help
explain why so many people have heart disease even if they do not have clear
risk factors such as smoking, high cholesterol or high blood pressure.
And they could lead to a test to predict the risk of heart disease, the
biggest cause of death across the globe.
"I think this is a stunner," Dr. Francis Collins, director of the National
Human Genome Research Institute, told reporters.
"It seems like this one place carries all of that weight for two very common
and very dangerous diseases."
Both teams used a new method of combing the genome for disease genes called
a genome-wide association study, which was not possible until the full human
genome was published in 2003. Now scientists can map the DNA of people with
a disease, compare them to this template genome or to people without a
disease, and find what is different.
The two studies, using 40,000 people, found the same thing — a stretch of
DNA called 9q21 carried certain mutations in people with heart disease. It
is an area that had not previously been identified as a gene, which may make
it more difficult to determine how it causes disease, scientists said.
Dr. Ruth McPherson of the University of Ottawa Heart Institute and
colleagues scanned blood samples from 23,000 people.
Anna Helgadottir of Iceland-based deCODE Genetics Inc. in Reykjavik and U.S.
colleagues at Emory University in Atlanta, the University of Pennsylvania
and Duke University in North Carolina tested 17,000 people.
HEART ATTACK RISK
The deCODE team found that about 21 percent of the people they tested had
mutations in both copies of this DNA stretch, giving them a 64 percent
higher risk of a heart attack than people who carried no copies of the
mutation.
McPherson’s team said 20 to 25 percent of Caucasians they tested carrying
two mutated copies of 9q21 and had a 30 to 40 percent higher risk of
coronary heart disease than people without the mutation. Half the people had
one copy and they had a 15 percent to 20 percent higher risk of heart
disease.
Africans did not appear to carry the mutations, and in African-Americans,
the mutations were not associated with heart disease risk, McPherson’s team
wrote.
The region is not associated with inherited tendencies to have high
cholesterol or high blood pressure.
But 9q21 is found near two genes called CDKN2A and CDKN2B, which four
international teams of researchers last week reported they had identified in
their own genome-wide association study looking for diabetes.
Collins said the coincidence was astonishing.
"We are in the same place in the genome. Here is CDKN2B and 2A, their
signal, exactly in the same place as where we found an association for
type-2 diabetes," Collins told reporters.
While diabetes raises the risk of heart disease, the heart disease
researchers made sure that the patients they scanned did not have diabetes.
Collins said researchers will now have to look for a mechanism that explains
why a single stretch of DNA could cause both conditions.
In the meantime, deCODE plans to find practical uses.
"DeCODE plans to bundle this discovery with other genetic variants it has
linked to risk of heart attack into a DNA-based test for gauging inherited
risk of (heart attack)," the company said in a statement.