Researchers from the National Institutes of Health have discovered the first genes linked to stuttering — a complex of three mutated genes that may be responsible for one in every 11 stuttering cases, especially in people of Asian descent [Los Angeles Times]. Scientists have long suspected that stuttering has genetic roots, as it’s often seen in families and twins, but this is the first time they’ve identified genes linked to the problem.

Dennis Drayna, the geneticist who led the study, said he was shocked that two of the implicated genes were linked to rare, fatal metabolic disorders [USA Today], but noted that must stutterers don’t suffer from those disorders. Surprisingly, the genes that were altered in the stutterers are involved in removing metabolic waste from brain cells.

The researchers analyzed a section of chromosome 12 in a large Pakistani family and found that there were several mutations in three particular genes. “We think a special group of cells in the brain are particularly sensitive to these subtle mutations in these genes,” Drayna said [BusinessWeek]. He suspects that the mutated genes still partially function, but likened the system to a car that needs a tune-up: “It still runs but not quite right. Some cells in the body need this to run like a Ferrari in order to function properly and those cells are involved in the production of speech in the brain,” he continued [BusinessWeek].

Drayna said that this finding, published in the New England Journal of Medicine, would be instrumental in identifying children who might develop a speech impediment later on in life. This could help parents preclude future problems by getting the child into speech therapy early on. The National Institutes of Health estimates that there are 3 million people in the United States afflicted with this speech impediment–many of them children. About 60 percent of these people have at least one family member who stutters. Researchers believe that other genes will be found that also play a role in stuttering.

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