Genetic Mutation Behind Stuttering

by Garreth Myers

Stuttering or stammering is a speech disorder. In this, the flow of speech is disrupted, and there is involuntary repetition and prolongation of words and sounds. Apart from the visible symptoms of disruption of speech, emotional and psychological effects include embarrassment, fear and shame. These negative symptoms can be very detrimental to a person’s self-confidence and wellbeing. 

For centuries, the cause of stuttering has been a mystery. However, recently, researchers at the National Institute on Deafness and Other Communication Disorders in Bethesda, Maryland made a discovery with which they have been able to associate stuttering and genetics. This study is first of its kind and has been able to identify three genetic mutations as potential causes behind stuttering that affects almost 5% of the child population and about 1% adults. The researchers believe that this discovery on genetic stuttering will help them in broadening the options of treatments that are available for stuttering. It is also believed that the results of this study on genetic stuttering will help in identifying those children who are at a risk of developing speech disorders like stuttering in the future. This can be instrumental in helping the parents prevent this coming problem by making speech therapy available for the child at an early age. 

The Study

The research aimed at finding a link between stuttering and genetics was lead by Dr. Drayna, who is a geneticist with the NIDCD. Previously, Dr. Drayna conducted studies on genetic stuttering in a group of a volunteer family from Pakistan. From his study, he inferred that chromosome 12 holds a gene variant that is responsible for causing stuttering. In the latest research, Dr. Dennis Drayna and his team concentrated all their efforts on chromosome 12. In the research, they were able to identify genetic mutations in the people who stuttered in a gene called GNPTAB. This gene is present in all higher animals, and it is responsible for encoding a particular enzyme, which assists the process of breakdown and recycling of the cellular components. The genes linked with stuttering have also been found to be the cause for some metabolic disorders. People who have these metabolic disorders are unable to break down the cellular waste and a result the waste accumulates in their cells.

To further strengthen their discovery of the possible link between stuttering and genetics, the team analyzed genes of 123 individuals who stuttered. All these individuals were from Pakistan. In this group 46 were from the original families, 77 were unrelated and another 96 unrelated individuals who did not stutter. People from England and the United States also volunteered to be a part of this study. A total of 270 people who stuttered and 276 who did not stutter were included from these countries. The research team found that a number of individuals who stuttered had the same genetic mutations as was present in the large Pakistani family that volunteered in the study.

What's Next?

With the study, the researchers have been able to estimate that about 9% of the people who stutter possess genetic mutations. The team says that they will conduct another study at a larger scale that is on a global platform to be able to determine in a better way the number of people who carry one of the three mutations. The long-term goal of the research team is to apply the findings of their research to study how this mutation affects structures in the human brain that control speech or are responsible for fluent speech. Dr. Drayna hopes that his study will help in give a strong backing for classifying stuttering as a biological disorder and not solely a behavioral disorder.


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