WASHINGTON: Thousands of genetic “dimmer” switches, regions of DNA known as regulatory elements, were turned up high during human evolution in the developing cerebral cortex, according to new research from the Yale School of Medicine.
Unlike in rhesus monkeys and mice, these switches show increased activity in humans, where they may drive the expression of genes in the cerebral cortex, the region of the brain that is involved in conscious thought and language. This difference may explain why the structure and function of that part of the brain is so unique in humans compared to other mammals.
The research, led by James P. Noonan, Steven K. Reilly, and Jun Yin, is published March 6 in the journal Science.
In addition to creating a rich and detailed catalogue of human-specific changes in gene regulation, Noonan and his colleagues pinpointed several biological processes potentially guided by these regulatory elements that are crucial to human brain development.
“Building a more complex cortex likely involves several things: making more cells, modifying the functions of cortical areas, and changing the connections neurons make with each other. And the regulatory changes we found in humans are associated with those processes,” said Noonan, associate professor of genetics, an investigator with the Kavli Institute for Neuroscience, and senior author of the study. “This likely involves evolutionary modifications to cellular proliferation, cortical patterning, and other developmental processes that are generally well conserved across many species.”
Scientists have become adept at comparing the genomes of different species to identify the DNA sequence changes that underlie those differences. But many human genes are very similar to those of other primates, which suggests that changes in the way genes are regulated — in addition to changes in the genes themselves — is what sets human biology apart.
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