A recent study published in Nature has shed light on the small differences in our DNA that contribute to our unique human brain characteristics. Researchers found that 98.8% of our DNA is shared with chimpanzees, but it’s the remaining 1.2% that makes us human.
Led by Professor Debby Silver and her team, scientists focused on a specific region called Human Accelerated Regions (HARs), which are highly conserved stretches of DNA near genes involved in brain development. They discovered how small changes can significantly impact the development of the cerebral cortex, the part of the brain responsible for higher cognitive functions.
The researchers created genetically engineered mice with human HAR and observed that they had larger cerebral cortexes and more neurons than control mice. This change was linked to activity in the Wnt signaling pathway, a key regulator of progenitor cell proliferation and neuronal differentiation.
When they edited human stem cells to include the chimpanzee version of the HAR, neural progenitor proliferation decreased, while adding the human sequence led to increased proliferation. The study’s findings reinforce the importance of studying this locus, particularly in relation to autism, as gene variants associated with the condition were found within the HAR sequence.
While the study highlights the complexities of our unique brain characteristics, it also acknowledges that these changes may come with an increased risk for disease. As Silver noted, “Over the course of evolution, we’ve acquired changes that have helped us become human, but with those changes, there’s also a propensity for disease.” The researchers emphasize that their study is just one piece of the puzzle, and further research is needed to fully understand what makes us human.
Source: https://medschool.duke.edu/news/what-makes-us-human