Human Language Gene Gets Mice Moving

No Gift for Gab

March 7, 2008 -- Scurrying mice would seem to have little to do with human language, but new research has found that a slightly different version of a gene associated with human speech also governs movement in rodents.

The finding gives new meaning to the phrase "loose lips," since the researchers who conducted the study believe that the human ability to speak evolved, in part, from the capacity to move the lips around efficiently.

Scientists first began to zero in on the gene, called Foxp2, when they noticed that people with defects in it had trouble speaking.

"Foxp2 is the only gene thus far to be linked to human speech and language," co-author Simon Fisher explained to Discovery News. "In humans who carry a [defect] in the gene, it leads to them having problems with learning to make rapid sequences of mouth movements."

Fisher is a Royal Society research fellow and head of the Molecular Neuroscience group at the Wellcome Trust Center for Human Genetics at the University of Oxford.

Since Foxp2 in healthy humans is just a mutated form of a gene present in all vertebrates, including rodents, Fisher and his team introduced a defective form of the gene into mouse brains to see what would happen.

While mice with the defective gene appeared to have relatively normal brain structure and development, further testing proved otherwise.

The researchers provided the gene-altered mice with an angled, rotating running track in their cages. Mounted on a greased, steel axle, the track operated like an off-kilter carousel, powered by little mouse legs.

 

Just as pet mice take to exercise wheels, the lab mice quickly jumped on the track and ran. They got better at it over time, as evidenced by the length of their track-trotting sessions.

The gene-mutated mice, however, "displayed slower increases in bout length than [their normal] littermates," the researchers found. Their running speeds were slower, too, another indicator of motor-skill learning.

"This suggests that in common ancestors of mouse and man, perhaps Foxp2 had general functions in learning to produce movement sequences, and it has been recruited towards speech functions during human evolution," Fisher said.

The findings are published in the latest online edition of Current Biology.

Humans may not have been the only species to recruit the gene for communication, either. A recent study on zebra finches found that when the bird's version of the gene was mutated, young songbirds had trouble accurately copying songs sung to them by adult bird "tutors."

Even Neanderthals were recently discovered to have a version of Foxp2. Their anatomy probably would have allowed rapid mouth movements, and scientists believe they may have also been able to speak.

Robert Berwick, a professor of computational linguistics at the Massachusetts Institute of Technology, advises to avoid drawing too many conclusions based on the Foxp2 discoveries, however, particularly when they're linked to language. The complex skill still stumps researchers and almost defies description.

"If you can't define what it is, why study it from an evolutionary point of view?" Berwick questioned.

Nevertheless, Fisher and his team hope future work on the "language gene" may lead to a better understanding of how the gift for gab emerged in humans. The research may also lead to treatments for people suffering from speech disorders caused by genetic defects.