Gene breakthrough--a ray of hope for stuttering people

Until now, it had been assumed that stuttering was a symptom of severe anxiety. But the novel research suggests that stuttering is biological in origin and not the result of poor parenting, emotional distress or other nebulous factors.

U.S. researchers have discovered three genes that appear to be linked to the speech disorder, which affects three million Americans and five percent of young children.

Key to stuttering identified
Researchers at the National Institute on Deafness and Other Communication Disorders (NIDCD) in America have identified these genes as a source of stuttering in volunteers in Pakistan, the United States, and England.

"For hundreds of years, the cause of stuttering has remained a mystery for researchers and health care professionals alike, not to mention people who stutter and their families," said James F. Battey, Jr., M.D., Ph.D., director of the NIDCD, part of the National Institutes of Health.

The research team has discovered a likely location of gene variants that appear to be linked to the condition. The researchers say mutations in two of the genes have already been implicated in other rare metabolic disorders also involved in cell recycling, while a third, closely related, mutated gene has now been shown to be linked for the first time to a disorder in humans.

"This is the first study to pinpoint specific gene mutations as the potential cause of stuttering, a disorder that affects 3 million Americans, and by doing so, might lead to a dramatic expansion in our options for treatment," Battey added.

"We're extremely fortunate that these genes are extremely well-known and studied by people who have been in this field for decades," says Dennis Drayna, a geneticist at the NIDCD.

Study details
Drayna and colleagues reached their findings by analyzing the genes of 123 Pakistani individuals who stutter (46 from the original families and 77 who are unrelated) and 96 who did not. They then did the same for 270 stutterers in the U.S. and England and 276 non-stutters in the same countries.

They identified mutations in a gene known as GNPTAB in the family members who stuttered. The team noticed that some individuals who stutter possessed the same mutation as that found in the large Pakistani family. They also identified three other mutations in the GNPTAB gene which showed up in several unrelated individuals who stutter but were not there in the controls.

The GNPTAB mutations were present in many of the stuttering individuals but in none of the non-stutterers.

Drayna and his team hope they may be able to modify the current therapies to help people with a stutter.

"We identified three in this paper, but it is clear there are more genes on other chromosomes to be found," he said. "We think there is really a lot of hope for future progress in understanding the genetic causes of this disorder."

Stuttering
Stuttering, also referred to as stammering, is a speech disorder that begins during childhood and, in some cases, lasts throughout life. In the condition, a person repeats or prolongs sounds, syllables, or words, disrupting the normal flow of speech.

The therapies for adult stutters have focused on such strategies as reducing anxiety, regulating breathing and rate of speech, and using electronic devices to help improve fluency.

The study is published in the Feb. 10 Online First issue of the New England Journal of Medicine.