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An Oklahoma Medical Research Foundation scientist's work may explain why lupus occurs more in women.

Dr. Amr Sawalha discovered a gene on the X chromosome that likely plays a role in the autoimmune disorder. Women carry two X chromosomes but men carry only one.

Women develop lupus nine times more than men.

Chromosomes are long pieces of DNA found in cells. Humans have 23 pairs.

"This is the first gene to be related to adult (onset) lupus on the X chromosome,” Sawalha said, adding that he hopes the finding helps researchers understand why lupus is more common in women.

The gene Sawalha studied, , plays a role in controlling many other genes, and a mutation in it likely predisposes a person to lupus. If the gene is unable to do its job, as in lupus patients, immune system T cells become overactive, resulting in the immune system turning on the body.

"Basically, it makes the T cells abnormally active — hyperactive,” Sawalha said.

Sawalha's findings appeared last month in the journal Plos One. The gene's discovery could lead to new therapies for lupus. Some 2 million Americans and 15 million people worldwide have the disease.

Sawalha also is an assistant professor of medicine at the University of Oklahoma Health Sciences Center and a staff physician with the Veteran's Administration Hospital in Oklahoma City.

Lupus can affect multiple organs, joints and skin. It can be life-threatening and has no cure. Patients are treated with drugs that suppress their immune systems.

Researchers long have suspected the X chromosome played an important role in lupus, according to the report. Men who have Klinefelter's syndrome, in which they have an extra X chromosome, have a lupus risk similar to women's.

Because lupus' causes are unknown, Sawalha and others are focusing on identifying genes that are more often seen in lupus patients than in those who don't have the disease.

He said lupus likely is "polygenic,” meaning it is caused by two or more genes, and has environmental triggers as well.

The next step, he said, will be to study the mutated gene's chemical sequence to potentially treat or diagnose lupus.

"We want to know exactly where it is and what it will do,” he said.

Fellow OMRF lupus researcher Dr. John Harley and an international consortium in January identified 13 genes they think contribute to lupus.

OMRF is home to the Lupus Family Registry and Repository, a collection of blood samples from lupus patients and family members without lupus. By studying the differences among closely related donors, researchers seek to determine which genes predispose a person to developing lupus.

Samples from the repository were used in Sawalha's study.

OMRF President Dr. Stephen Prescottcommended the foundation that Sawalha's work lays.

"Sometimes understanding the basics of a disease is the key to finding more effective treatments,” Prescott said of the recent findings.