HOW A GENE DUPLICATION HELPED OUR BRAINS BECOME ‘HUMAN’
Scripps Research Institute Scientists Show How a Gene Duplication Helped our Brains Become 'Human'
Extra Copy of Brain-Development Gene Allowed Neurons to Migrate Farther and Develop More Connections; Findings May Offer Clue to Autism and Schizophrenia
(May 3, 2012) What genetic changes account for the vast behavioral differences between humans and other primates? Researchers so far have catalogued only a few, but now it seems that they can add a big one to the list. A team led by scientists at The Scripps Research Institute has shown that an extra copy of a brain-development gene, which appeared in our ancestors’ genomes about 2.4 million years ago, allowed maturing neurons to migrate farther and develop more connections.
Surprisingly, the added copy doesn’t augment the function of the original gene, SRGAP2, which makes neurons sprout connections to neighboring cells. Instead it interferes with that original function, effectively giving neurons more time to wire themselves into a bigger brain.
“This appears to be a major example of a genomic innovation that contributed to human evolution,” said Franck Polleux, a professor at The Scripps Research Institute. “The finding that a duplicated gene can interact with the original copy also suggests a new way to think about how evolution occurs and might give us clues to human-specific developmental disorders such as autism and schizophrenia.”