Five generations of a family in Dallas, Texas have helped scientists discover a genetic mutation that causes a common birth defect and contributes to Heart disease in adults.

Researchers at the University of Texas Southwestern Medical Center in Dallas studied DNA from 11 members of the family, including children and adults, who suffered from aortic Heart disease.

They found that all of them had a mutation on a gene called NOTCH1.

“Mutations in NOTCH1 cause an early developmental defect in the aortic valve,” said Dr Vidu Garg, an assistant professor of pediatrics and molecular biology.

Researchers found a second mutation on the same gene in members of a smaller family in San Diego, which they said confirmed their finding.

The aortic valve is normally composed of three flaps of tissue that open and close to enable blood to flow in one direction.

But about one or two percent of the population are born with valves with only two flaps which make them susceptible to aortic valve stenosis. The condition, which narrows the passage through which blood exits the heart, can require surgery at birth.

In severe cases the heart does not develop properly in the fetus and the child is born with an illness called hypoplastic left Hypoplastic left heart syndrome, a leading cause of Heart disease deaths in children.

“We know that aortic valve problems cause those deaths, so we think NOTCH1 mutations are likely the cause of some cases of Hypoplastic left heart syndrome as well,” said Dr Deepak Srivastava, of the University of California, San Francisco, who contributed to the research.

The scientists said the finding, which is reported in the science journal Nature, could help to identify people at risk of the problem. When researchers better understand the full impact of the mutation it could pave the way for new treatments for the heart ailments, according to the researchers.