Source : Perth Now news
The human brain may look like one highly complex organ, but scientists say it is actually made from two ancient nervous systems that evolved separately.
Researchers at Stanford University found that the front and back of the brain follow fundamentally different developmental pathways, suggesting they were once separate systems that were eventually brought together through evolution.
The hindbrain controls vital automatic functions including breathing, sleep, heartbeat and hunger, while the forebrain and midbrain are responsible for higher-level abilities such as language, consciousness, reasoning, vision and voluntary movement.
Dr Kyle Loh, an author of the study, said: “We’ve shown for the first time that the front of the brain arises from a totally different progenitor cell than the back of the brain.”
The team studied developing mouse embryos and found that cells destined to become the forebrain and midbrain express a gene called Otx2, while hindbrain cells express Gbx2.
They also discovered major differences in the way DNA is packaged in the two regions.
The finding could have major implications for studying diseases affecting the brain and nervous system.
Scientists have previously struggled to grow human hindbrain neurons in laboratories, limiting research into conditions including spinal muscular atrophy and amyotrophic lateral sclerosis (ALS).
Using their new understanding of how the hindbrain develops, the Stanford researchers were able to create functional hindbrain motor neurons in the laboratory for the first time.
Dr Rayyan Jokhai, a co-author of the study, said: “Previous attempts to make hindbrain neurons likely tried to coax forebrain and midbrain progenitors into hindbrain cells, which our study shows is not possible.”
He added: “Now we have a model to better understand these devastating diseases, and work toward regenerative therapies for them. This is a very exciting new frontier in brain research.”
The researchers also looked back more than 550 million years into evolutionary history, finding the same two-origin pattern in chickens, zebrafish and acorn worms.
Dr Loh said: “Our research suggests that evolution took two existing neural systems and pushed them together spatially.
“Having the brain as one organ would probably be more efficient, but we rely on this primordial way to make the brain as two separate pieces.”
