Scientists Find Evidence for Gene
That Predisposes Individuals to Stuttering

By Dennis Drayna, Ph.D.

Dennis Drayna, Ph.D., of the NIH, is the senior author of a study that found evidence that a gene can predispose individuals to stuttering.

In a study published in the American Journal of Medical Genetics, scientists at the National Institutes of Health have found evidence that a gene can predispose individuals to stuttering.

The research enrolled over one thousand families in which more than one person stuttered, and from this group, 70 families were chosen for additional scrutiny. In a series of laboratory experiments, researchers examined genetic markers located along the length of each of the human chromosomes, and found a group of markers on chromosome 18 that tended to be inherited along with stuttering in these families. This co-inheritance indicates that stuttering in these family clusters is caused by a gene that resides on this chromosome.

"At this time, it's not clear how wide the impact of this gene is," said Dr. Dennis Drayna, the senior author of the study. "We know that many different genes are likely to be involved in inherited cases of stuttering. It's clear that this gene on chromosome 18 is involved in some cases, but we don't yet know whether it's involved in a large majority of cases.

"The good news is that we've shown this type of genetic study is actually possible for stuttering. These types of studies can lead to the ultimate identification of the variant gene itself, which would be a great advance in our understanding of the causes of stuttering. On a more general level, it adds yet another piece of evidence that inherited factors can be important in stuttering."

An additional aspect of the study suggests a second gene, located on chromosome 13, may also have some role in genetic causes of stuttering. This is of interest due to previous reports that implicated a gene on chromosome 13 in stuttering in another group of subjects. In a disorder such as stuttering, which is likely to have a mixture of genetic and non-genetic causes, such independent findings provide important confirmation of the role of these genes in this disorder. The identification of one specific gene could provide greater understanding of the structures and functions in the body that are involved in speech production, and how those functions go awry in stuttering. This understanding, in turn, can lead to improved therapies and treatments for stuttering.

The work was a collaboration of two main groups, the National Institute on Deafness and Other Communication Disorders at the National Institutes of Health, in Bethesda, MD, and the Center for Inherited Disease Research at Johns Hopkins University in Baltimore, MD. Additional assistance in finding and enrolling families was provided by the Stuttering Foundation of America. "Most important of all, we couldn't have done this research without the help and cooperation from our stuttering family members," said Dr. Drayna.