In the 1990s, scientists in Britain came across a family, now referred to as the "KE family," in which almost half of its members suffered specific language impairments — so much so that their speech was unintelligible to others. Researchers had known for some time that speech impairments often occurred in more than one member of the same family and were more likely to occur in identical twins than fraternal, suggesting a hereditary component, but they did not know much about the genes involved.
The high proportion of affected members of the KE family suggested the disorder might point to a single gene — and that it was perhaps transmitted by the standard dominant/recessive pattern and not due to a combination of genes. Genetic studies performed on affected members of the KE family narrowed the location of the FOXP2 gene to a region of chromosome 7 that contained about 70 genes. At roughly the same time, another researcher identified a British boy, known now as "CS," who was unrelated to the KE family but suffered an almost identical language disorder. Analysis of his DNA showed a visible defect in the same chromosome, 7, which specifically affects the FOXP2 gene. As lead researcher Anthony Monaco of the University of Oxford said at the time, "The defect was like a signpost, precisely highlighting the gene responsible for the speech disorder."
Since then, FOXP2 has often been dubbed the "language gene" as modifications or mutations in it can result in speech and language problems, including slow language development, difficulties in controlling speech organs, speaking words and forming sentences. As such, scientists continue to study it in the process of understanding speech and language disorders, including autism. — Laura Ricks