Chromosomal signals for genes underlying stuttering: a preliminary report
Presenter: Ehud Yairi, University of Illinois
By Dr Steve Davis, University College London

The fact that stuttering runs in families has been recognised for a long time and has led to substantial research about the role of a genetic component to the disorder. Previous research has been primarily based on family history surveys that allow the prevalence of stuttering in families to be established. Recent advances in genetic research have enabled researchers to look more closely at how stuttering is passed from generation to generation.

Cells are the fundamental working units of every living system. All the instructions needed to direct their activities are contained within the chemical DNA (deoxyribonucleic acid). DNA in the human genome is arranged into 24 distinct chromosomes - each chromosome contains many genes, the basic physical and functional units of heredity.

Dr Yairi presented a preliminary report on the chromosomal analysis of families of people who stutter from the USA, Sweden and Israel. Blood samples of 481 relatives from 105 families were analysed. Chromosomal signals detected in the analysis supported the notion that different genes were responsible for transmission of the disorder in males and females. Findings from the study indicated that persistent and recovered stuttering (approximately 75% of people who stutter will recover before adolescence) are genetically different forms of the disorder.

The study revealed that several of the chromosomal regions that were implicated in stuttering have also been implicated in genotype mapping studies of other language disorders. One of the regions implicated in this study, chromosome 7, is close to the Foxp2 gene, a mutation of which is linked to other disorders that affect speech, including autism and specific language impairment. Another was chromosome 21 which has been linked to Down's syndrome - a disorder which is known to affect the ability to understand and produce speech and language.

Dr Yairi stressed that this was a preliminary report and that the number of participants was small for this type of analysis. He suggested that chromosomal analysis should be used in conjunction with other areas of research in a multifactor approach investigating the cause and development of the disorder.

From the Winter 2005 edition of Speaking Out

Internet link
On the Gender Factor in Stuttering - Autumn 2005 article by Dr Yairi on Stuttering Foundation of America website, including links of gender and genetics research