Are genes also to blame for stuttering?
Stuttering is a common speech disorder characterized by repetition and stretching of sounds, as well as impaired smoothness of speech, which affects about 60 million people worldwide. Stuttering is considered to be a psychological problem, but the results of studies involving twins and adopted individuals indicate that this disorder is inherited. And according to data obtained by scientists from the National Institute of Deafness and Other Communication Disorders of the USA (Bethesda, Maryland), working under the direction of Dennis Drayna, ten different mutations of three genes encoding lysosomal enzymes can be the cause.
The work, the results of which were published on February 10 in the on-line version of The New England Journal of Medicine in the article "Mutations in the Lysosomal Enzyme–Targeting Pathway and Persistent Stuttering", was based on data obtained by Draina and colleagues in 2005. Then scientists found that mutations in the 12th chromosome are the suspected cause of stuttering. As part of the latest work, the authors analyzed the genotypes of approximately 400 stutterers and identified 10 specific mutations of three genes of the long arm of the 12th chromosome, occurring in 9% of stutterers and practically not occurring in individuals of the control group who do not suffer from speech disorders.
A common feature of the three genes (GNPTAB, GNPTG and NAGPA), mutations of which are associated with stuttering, is that they encode enzymes of lysosomes – cellular organelles engaged in cleavage of cellular debris and sending cleavage products for reuse. Any of the mutations identified by the researchers can disrupt this process and lead to the accumulation of partially cleaved cell fragments in lysosomes.
To date, it is unclear how these mutations lead to stuttering, but Draina suggests that there are specific neurons in the brain responsible for the formation of speech and predisposed to the development of this anomaly.
In the future, the authors plan to create a mouse model of stuttering by mutating the discussed genes. However, first they have to figure out how similar stuttering violations of animal sounds sound.
The results obtained indicate the possibility of treating stuttering with the help of enzyme replacement therapy. Perhaps someday, in order to get rid of stuttering, periodic intravenous injections of enzymes that will support the normal functioning of neurons will be enough.
According to Draine, his work will help not only draw the attention of clinical medicine to stuttering, but also find an appropriate place for this condition in medical nosology. He also notes that stuttering in childhood often passes as a person grows up, but in some cases it persists throughout life and, unfortunately, sometimes has serious negative consequences on a person's life as a whole.
Evgeniya Ryabtseva
Portal "Eternal youth" http://vechnayamolodost.ru based on the materials of Nature: Genetic basis for stuttering identified.
15.02.2010