Scientists Find Risk Factor for Tears in the Aorta

People who have too many copies of genes in a certain chromosome may have a 12-times greater risk of developing bulges and tears in their aorta, the main artery that carries blood from the heart to the rest of body, U.S. researchers said on Thursday.

The findings, published in the journal PLoS Genetics, could be used to help predict which patients are at risk for such bulges, known as aortic aneurysms, and related tears that kill 10,000 people each year in the United States, the team said.

They said people with too many copies of genes in a specific region of chromosome 16 may have an aggressive form of thoracic aortic disease that makes bulges in the artery called aneurysms more prone to tearing, an urgent condition that can lead to sudden death.

The findings are based on a new way of studying genetic variation that looks for extra copies or deletions in sections of DNA, referred to as copy number changes or variants.

These variants can cause people to have too many copies or not enough copies of a particular gene.

"We're just starting to understand copy number variants and their link to disease," said Dr. Dianna Milewicz of the University of Texas Medical School at Houston.

In the current study, Milewicz and colleagues zeroed in on a particular region of chromosome 16 known as 16p13.1. This region contains nine genes.

About one in every 1,000 people have duplications of genes in this area, and having these can raise a person's risk of schizophrenia and attention-deficit hyperactivity disorder.

One of the genes in this region known as MYH11 affects smooth muscle cell tissue in major arteries in the body, including the thoracic aorta.

Prior studies have shown that inherited mutations in this gene can causes weakness in the lining of the thoracic aorta.

Milewicz and colleagues decided to see if extra copies of genes in this region could raise the risk of aneurysms in people who do not have a family history of the disease.

They studied patients who had non-familial aneurysms and tears in the aorta and found duplications in this region in eight out of 765 patients, compared with just four in a group of nearly 5,000 control patients.

The findings suggest that people with duplications of this gene are 12 times more likely to develop aortic disease than people who do not.

"The results of this study could affect clinical care because it appears patients with 16p13.1 duplications have an aggressive form of the thoracic aortic disease that causes aneurysms to dissect at smaller diameters," Milewicz said in a statement.

Companies are developing powerful new machines that will be able to quickly and cheaply sequence the entire human genome, and some researchers predict these tools could soon be within patients' reach in the next two years.

Milewicz said once that was possible, doctors would be able to identify patients with duplications in this chromosome region and monitor them for aortic disease.