An international team of neuroscientists led by the Center for Regenerative Therapy at the Dresden University of Technology has identified a new factor that influences the growth of the neocortex, the brain’s highly developed outer layer. The finding appears in a leading science journal as part of ongoing work to map how the brain’s outer shell becomes more intricate over time.
The neocortex is the folded surface that covers much of the brain. It plays a key role in advanced thinking, problem solving, language, and planning, and it is generally regarded as the youngest major brain region in evolutionary terms.
Researchers note that the precise molecular steps driving neocortical expansion remain only partly understood.
To uncover growth-promoting factors, the team studied brains from mice, gorillas, and humans using organoids — laboratory-grown miniature brain models derived from stem cells. Through these models, they identified a protein called epiregulin as a factor that can drive neocortical expansion in developing tissues.
Epiregulin is present across many mammals, including primates and rodents. Yet in mice, the gene responsible for producing this protein is inactive, meaning it is not used in that species.
When scientists compared the effects of epiregulin on human and gorilla brain organoids, they found that gorilla organoids began to show growth in response to the protein, while human organoids demonstrated a noticeably weaker response to the same signal.
Experts suggest that the stronger sensitivity in gorilla tissue may reflect a different trajectory in neocortical development between species. In humans, the neocortex is already highly developed, which could reduce the apparent impact of this single growth factor in later stages of development.
Previous studies have noted a long-term trend of increasing brain size in humans. In the past century, average brain volume has shown a modest rise, highlighting continued physiological changes in human evolution and development. These observations help frame how new discoveries about growth factors fit into the broader picture of brain biology. [Citation: EMBO]