Stuttering may be the result of a glitch in the daily process by which cellular components in key regions of the brain are broken down and recycled, says a new study, which associates a gene mutation with the disorder.
The study, led by researchers from the National Institute on Deafness and Other Communication Disorders (NIDCD), has identified three genes as a source of stuttering in volunteers in Pakistan, the US and Britain.
Stuttering is a speech disorder in which a person repeats or prolongs sounds, syllables, or words, disrupting the normal flow of speech. It can severely hinder communication and a person's quality of life.
Mutations in two of the genes have already been implicated in other rare metabolic disorders also involved in cell recycling, while mutations in a third, closely related, gene have now been shown to be associated for the first time with a disorder in humans.
“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, director of the NIDCD.
“This is the first study to pinpoint specific gene mutations as the potential cause of stuttering, a disorder that affects three million Americans, and by doing so, might lead to a dramatic expansion in our options for treatment.”
Stuttering tends to run in families, and researchers have long suspected a genetic component. Previous studies of stuttering in a group of families from Pakistan had been done by Dennis Drayna, geneticist with the NIDCD, which indicated a place on chromosome 12 that was likely to harbour a gene variant that caused this disorder.
Mr. Drayna and his team refined the location of this place on chromosome 12 and focused their efforts on the new site. They then analysed the genes of 123 Pakistani individuals who stutter - 46 from the original families and 77 who are unrelated - as well as 96 unrelated Pakistanis who don't stutter, and who served as controls.
Individuals from the US and Britain also took part in the study, 270 who stutter and 276 who don't, said a NIDCD release.
Researchers found some individuals who stutter possessed the same mutation as that found in the large Pakistani family. They also identified three other mutations in a gene which showed up in several unrelated individuals who stutter but not in the controls.
These findings were published in the February online First issue of the New England Journal of Medicine.
