Expanding Cognitive Capacities: The Genetic Alteration Responsible for Enlarging Human Brains and Enhancing Intelligence
In a groundbreaking discovery, scientists have found that a microscopic genetic enhancer called HARE5, located near the Frizzled gene, holds the key to understanding the evolution of the human brain. This genetic enhancer, which carries four human-specific mutations, has been found to play a crucial role in brain development.
When HARE5 is inserted into mice, the brains of these genetically modified creatures grow larger and are packed with more neurons. The growth of excitatory neurons, which enable advanced thinking, is higher in these mice, suggesting a possible reason for the cognitive advancements seen in humans.
This discovery reshapes our understanding of human uniqueness. It suggests that it was not a single "intelligence gene," but rather precision tweaks to ancient regulatory code, that made us smarter. The full instruction manual behind the human brain may be revealed through the study of HARs (genetic enhancers like HARE5).
Interestingly, the chimp version of HARE5 produces fewer neural progenitors compared to the human version. This finding further emphasises the significance of HARE5 in human brain development.
The cerebral cortex of humans is three times larger than that of chimpanzees, a fact that has long puzzled scientists. This discovery sheds light on this mystery, as the neocortex of the genetically modified mice was found to be 12% bigger. Furthermore, these mice showed greater functional autonomy between brain regions, reflective of higher-level cognition.
The role of HARE5 in brain development could shape the future of medicine, particularly in treating disorders like microcephaly and autism. Understanding HARE5's role could potentially lead to repairing defective development or creating smarter neural organoids for drug testing.
Research in recent years has focused on species such as chimpanzees and other primates to determine if they possess a similar, mutated version of HARE5 like humans. Blocking WNT signaling in human brain organoids erases the proliferation advantage of human cells compared to chimpanzee cells, providing further evidence of HARE5's unique role in human brain development.
The search for evolutionary secrets hidden in our genome has only just begun. HARE5 prolongs the phase of self-renewal in radial glial cells, the brain's neural stem cells during early development. It is likely just one of many molecular switches waiting to be uncovered in evolutionary neuroscience.
This discovery opens up a new avenue for research into the evolution of the human brain and the potential treatment of neurological disorders. As our understanding of HARE5 and its role in brain development continues to grow, so too will our ability to unlock the secrets of the human mind.
