Our closest animal relative is the chimpanzee, and our evolutionary split from chimps happened about five million years ago. Since then, our brains have advanced, and parts of our genome have evolved quickly.
Researchers at UC San Diego have taken a close look at one of those swiftly mutating genetic regions, with the belief it could explain the unique and advanced brain that makes humans who we are.
Cognitive scholars call these rapidly evolving genetic sequences Human Accelerated Regions, or HARs. One of them, HAR123, plays a key role in brain development and acts as a gene enhancer.
“I guess as an analogy, one can think of genes as being players in an orchestra, and enhancers are basically like the conductor,” said Miles Wilkinson, brain scholar and professor of reproductive sciences at UCSD.
Wilkinson and his research partners zeroed in on that genetic conductor, HAR123, to see what it did and what genes it activated. They found that it was very active in creating precursor cells that became neurons in the brain.
When they used gene editing to remove HAR123 from mice, they saw a dramatic reduction in those precursor cells.
Researchers are trying to understand why humans brains are so unique and so different from those of our primate cousins. Our brains are larger and devote more area to the cerebral cortex.
“Which is important for higher cognitive functions. And that’s much larger in primates than in nonprimates, but it’s even much larger in humans compared to chimps or other nonhuman primates,” Wilkinson said.
In mouse trials, researchers have shown HAR123 is critical for developing cognitive flexibility. Proof of that in humans is a long way off.
But Wilkinson adds studying this genomic region could also help explain the causes of neural diseases like autism or schizophrenia.
“HAR123 is important for forming the brain cells,” he said. “It regulates the generation of brain cells, neural cells and glial cells, (so) it stands to reason that if it is mutated or messed up in some individuals you could have neural disease.”
Wilkinson and his research teams published their study last week in the journal Science Advances.
