Thursday, October 20, 2016

Mice’s love songs go wrong when ‘language gene’ is messed up

Is it me you
Is it me you’re looking for?

COLIN VARNDELL/SCIENCE PHOTO LIBRARY

By Clare Wilson

Mouse squeaks may have more in common with human speech than we realised. Tinkering with a gene associated with language in humans has been found to mess up mice’s mating calls.

The gene, called FOXP2, is one of the most-studied genes involved in human brain evolution. It was discovered in the 1990s in a study of a British family that had 16 relatives who had difficulty making certain mouth movements and complex sounds.

The gene turned out to encode a protein that is found in the brain while we develop in the womb, and its shape suggests it works by helping to turn other genes on and off. Other studies have shown that, while FOXP2 has stayed mostly unchanged throughout mammal evolution, there have been two mutations in the gene since we split from our closest living relatives, chimpanzees.

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It is thought that these mutations enabled us to evolve superior vocal abilities. But the mutation seen in the original family is different, and it is not known how exactly it affects speech. Putting this mutated gene into mice helps us unravel what has gone wrong, and might let us understand other genetic speech disorders, says Simon Fisher at the Max Planck Institute for Psycholinguistics in Nijmegen in The Netherlands.

Courting interrupted

Mouse studies have found some evidence that changing FOXP2 changes the ultrasonic squeaks that pups use to call for their mother. One study found that disrupting the gene resulted in the pups making fewer calls, but another study did not.

But it may be more informative to look at the adults’ courting songs, says Fisher, as the babies’ calls are just simple squeaks. The courting songs, on the other hand, are complex sequences of rapid chirps swooping up and down in pitch, lasting tens of seconds. If lowered for human hearing they sound similar to bird song.

Fisher’s team found that songs by the mice with the FOXP2 mutation were shorter and less complex than those of unaltered mice. “We found properties that are strikingly reminiscent of some of the key features of the human FOXP2 disorder.”

In other studies, mice have been given the normal human version of FOXP2. This seemed to make them better at learning to do a task automatically, hinting that it helps infants learn to talk by giving them unconscious control over their lips and tongue.

A tantalising question is what would happen if a chimp was given the human version of FOXP2. But no one has tried this, as it is much harder to create genetically modified primates than mice, and chimp research is only allowed where there is important medical need. “It would be unethical to try,” says Fisher.

Journal reference: Frontiers in Behavioural Neuroscience, DOI: 10.3389/fnbeh.2016.00197

Read more: How humans evolved language, and who said what first

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