Humans are alone on the planet in their use of language to communicate. Now a team of researchers has identified the first gene directly involved in speech, a discovery that may provide insights into how the brain processes language, and how and when language arose.
For a decade, efforts to pinpoint speech- and language-associated genes have centered around a British family known to researchers as "KE." Nearly half its members suffer from an inherited disorder whose symptoms include garbled pronunciation, putting words in the wrong order, and difficulty understanding speech.
It was a collaboration begun several years ago that, with a lucky break, finally pinned down the gene responsible for the disorder. A group led by cognitive neuroscientist Faraneh Vargha-Khadem, of the Institute of Child Health in London, and Oxford geneticist Anthony Monaco had localized the defect to a segment of chromosome 7, which they called SPCH1. While they were searching for the gene, they discovered a 5-year-old boy from another family with a similar disorder. Analysis of the boy's genome showed that a large segment of his chromosome 7 had switched places with a segment of chromosome 5, a genetic error known as a translocation.
The "breakpoint" of the boy's translocation turned out to be in the middle of a gene the researchers called FOXP2. When they screened the KE family to see if some carried a defect in this gene, all affected members turned out to share a specific mutation that apparently rendered FOXP2 inactive, the group reports in the 4 October issue of Nature. Although this seems to account for KE and the unrelated boy's language disorder, researchers caution against calling FOXP2 a "language" gene. Because the handicap extends to nonverbal sequences as well, like opening and closing the mouth when asked, the core disability may include a motor dysfunction as well as something specific to language. Brain studies have linked the disability to defects in the basal ganglia.
Still, "this is the first clear identification" of a gene "with direct relevance for language ability," says geneticist Svante Pääbo of the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany. His group is studying FOXP2 in nonhuman primates to see how it differs from the human version. But researchers caution that the function of the gene is not yet clear, and that it is probably only one of many genes involved in speech and language.