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.”