Thursday, November 12, 2009

Researchers have found a crucial genetic difference between humans and chimps that could help explain our language and speech abilities. The difference lies in a gene called FOXP2 which encodes for a protein of the same name. This acts as a transcription factor, controlling the activity of other genes.

The human and chimp versions of the protein differ in only two of their 740 amino acid components, but when researchers at the University of California, Los Angeles, replaced the human gene with the chimp version in neurons grown in the laboratory, they found it affected the expression of at least 116 other genes.

The results are detailed in a paper published on Thursday in the scientific journal Nature.

Author of the study Dr. Daniel Geschwind, of the David Geffen School of Medicine at UCLA, said the gene had a “major role” in differences between chimps and humans. “We showed that the human and chimp versions of FOXP2 not only look different but function differently too.”

Some of the affected genes control the formation of connections in the brain, whilst others relate to facial movements. Several have already been found to be involved in language disorders. Mutations in FOXP2 itself were also known to affect speech and language; the gene was first identified in members of a family suffering from language problems who were found to share a genetic mutation.

Frances Vargha-Khadem at University College London has studied patients with FOXP2 mutations, and agrees with the new research. As well as language problems, some of her subjects have changes in the shape of their jaws, mouths and tongues. She thinks that chimps may also have these differences.

“We believe FOXP2 is not only important for the higher order cognitive aspect of language but also for the motor aspect of speech and language,” said Genevieve Konopka, one of the authors of the paper at UCLA.

Previous research indicates that the changes in FOXP2 occurred around 200,000 years ago with the rise of modern humans. Geschwind also suggests that several of the related genes may have evolved together. Preliminary studies have shown signs that they too emerged relatively recently.

Scientists are now keen to further study FOXP2 and the genes that it affects. Geschwind believes this could eventually lead to breakthroughs in treatment for disorders such as autism and schizophrenia, which affect language skills.

The study was funded by the National Institute of Mental Health, the A.P. Giannini Foundation and the National Alliance for Research on Schizophrenia and Depression.