By IANS,
Washington: The genetic changes that account for the bulk of differences between humans and primates boils down to a single factor – gene duplication, which gave us an all powerful brain.
A study by scientists of the Scripps Institute has shown that an extra copy of a brain-development gene, SRGAP2, first appearing in our ancestral genomes 2.4 million years ago, allowed maturing neurons (brain/nerve cells) 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 senior study author Franck Polleux, professor at the Scripps Research Institute, the journal Cell reports.
“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 developmental disorders such as autism and schizophrenia,” said Polleux.
Polleux specialises in the study of human brain development, and several years ago, his lab began researching the function of the newly-discovered SRGAP2, according to a Scripps statement.
He and colleagues found that in mice, the gene’s protein product plays a key role during brain development: It deforms the membranes of young neurons outward, forcing the growth of root-like appendages called filopodia.
As young neurons sprout these filopodia, they migrate more slowly through the expanding brain. Eventually they reach their final position where they form connections.
Shortly after beginning the project, Polleux learned from other labs’ work that SRGAP2 was among the few genes (about 30) that had been duplicated in the human genome less than six million years ago after separation from other apes.
“These evolutionarily recent gene duplications are so nearly identical to the original genes that they aren’t detectable by traditional genome sequencing methods,” said Polleux.
According to Polleux, “only in the last five years have scientists developed methods to reliably map these hominid-specific duplications”, which account for vast differences between humans and their primate cousins.