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Release: July 7, 1999

UI researchers show prominence of gene mutation that causes inherited deafness

IOWA CITY, Iowa — One in 33 normal hearing people in the Midwest has a mutated gene that causes inherited deafness, according to recent University of Iowa Health Care research findings.

The mutated gene known as GJB2, which can be passed on from parent to offspring, is thought to be the leading cause of childhood deafness. Although having the mutation does not necessarily mean that the individual will be born deaf, UI researchers showed that 35 percent of their 52 study subjects who were deaf had the mutated gene.

The UI study helps make it possible for families with children who are born with severe hearing impairments or total deafness to know the reason for the condition. This genetic test eliminates the need for other more dangerous and less effective diagnostic tests.

"This is significant," said Glenn Green, M.D., UI research fellow in otolaryngology and lead researcher in the UI investigation. "If you don’t know the cause, it’s hard to know how best to rehabilitate the patient."

Based on their work, Green and his colleagues know that cochlear implants work especially well on patients with the GJB2 mutation. However, the UI investigators plan to look at other strategies to find out if there is an even better way of treating these individuals. Cochlear implants are electronic devices that a physician surgically places in a person's cochlea. The device, which receives signals from a processor worn outside the body, takes the place of damaged or absent cochlear hair cells. The device converts acoustic information into electrical signals that can be transmitted to the brain and perceived as sound.

In addition to evaluating treatments, the UI researchers plan to start looking at other genes that may lead to deafness as well as develop more precise tests for detecting severe-to-profound deafness due to genetics.

About one in every 1,000 children is born with severe hearing impairment or total deafness. For some time, researchers have suspected that the deafness was genetic, but there had not been any focus on identifying the exact problem until relatively recently. The UI conclusions are consistent with evidence from France and Australia.

An article on the UI findings concerning GJB2 mutation appeared in a recent issue of the Journal of the American Medical Association. The work was supported by grants from the National Institute on Deafness and Other Communications Disorders, and the National Center for Human Genome Research.