Scientists from the Wellcome Trust Centre for Human Genetics in Oxford and the Institute of Child Health in London have identified a gene linked to the disruption of speech and language development. The genetic link may show why some people suffer from particular language impairments. Professor Anthony Monaco from the Wellcome Trust Centre said that the discovery is 'the first evidence of a particular gene that has been pinpointed as having a mutation leading to a language disorder'.
The team of scientists studied three generations of a British family affected by a language impediment in which there are difficulties identifying basic speech sounds, understanding grammar and articulating speech. Previous studies of the family had indicated a region on chromosome seven where there might be a defect. Then a similar impairment was found in an unrelated boy, who had a visibly odd version of chromosome seven. This allowed the search for the mutated gene to be narrowed down.
The scientists found that an error in the DNA sequence of a gene called FOXP2, in which a single nucleotide is substituted by another, is the cause of the impairment. The FOXP2 gene is thought to code for a protein that controls additional genes involved in speech and language. When the gene is mutated, both speech and language become disrupted.
The discovery might also eventually help us understand how humans ever began to speak. Scientists have already started to look for the same gene in other primates. It is also thought that knowledge of a genetic cause for one type of language disorder will motivate the search for other types, and for possible genetic causes of cognitive and learning disorders.