June 2, 2018
CBC Radio

Researchers in the U.S. and Europe have identified a unique human gene that seems to be an important factor in our oversized human brains, which are three times the size of our closest relatives, the chimpanzees.

The teams found that the gene works during brain development by creating a large population of neural stem cells — factories for producing neurons. When these stem cells are unleashed, they then explosively produce the 100 billion neurons found in the human brain.

They were also able to reconstruct the evolution of of this gene, which tells a fascinating tale of lucky accidents in our genetic history.

David Haussler, the director of the University of California Santa Cruz Genomics Institute, led the American team. The discovery had roots in work being done in his lab in 2012. They were culturing small patches of brain cells from humans and rhesus macaques, one of the best-known species of Old World monkeys, to look at the differences in how human and monkey genes operated as the tissue grew. What they saw was a big difference in the way the tissue was developing.

“That’s when we knew we had something very exciting,” says Haussler. The team was “shocked” to find out that there was one gene that was expressed very strongly in humans, and not expressed at all in macaque cerebral development. What they had discovered was a gene uniquely responsible for human brain size. They called it NOTCH2NL.


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