Debra Silver at Duke University and her colleagues have uncovered a stretch of DNA that appears to influence human brain size, as they report in Current Biology.
Silver and her team searched the human genome for rapidly evolving non-coding regions that appear to function as developmental enhancers in the neocortex, and homed in on HARE5, an enhancer of FZD8, which is a receptor of in Wnt pathway. They then added the human or chimpanzee versions of this enhancer to transgenic mice to find that the human version lead to an accelerated neural progenitor cell cycle and increased brain size — some 12 percent bigger, NPR's All Things Considered notes.
"What we discovered is that the human DNA turned on gene activity in neural stem cells, and these are cells which produce the neurons of our cerebral cortex," Silver tells NPR.
Katie Pollard from the University of California, San Francisco, who was not involved in the study, says these bigger brains in mice are "intriguing." However, she notes that determining their effect on cognition would be difficult to do.