Human brain may have two ancient origins
The human brain develops from two distinct populations of progenitor cells rather than a single shared source, suggesting that evolution may have combined two ancient nervous systems into one organ, reports a Qazinform News Agency correspondent.
The Stanford Medicine study, published in Nature Neuroscience, examined the earliest stages of brain formation in mouse embryos.
Researchers identified one cell population expressing the Otx2 gene, which develops into the forebrain and midbrain, and another expressing Gbx2, which forms the hindbrain. The populations followed separate developmental pathways and displayed different chromatin configurations from the beginning.
“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,” said senior author Kyle Loh, associate professor of developmental biology at Stanford.
The forebrain supports language, consciousness and abstract reasoning, while the hindbrain controls essential automatic functions such as breathing, heartbeat, sleep and hunger. It also contains neurons governing facial, throat and tongue muscles.
Using the findings, the researchers successfully guided human pluripotent stem cells into functional hindbrain motor neurons. The laboratory-grown cells generated electrical signals and proteins associated with regions controlling swallowing and facial movement.
The breakthrough could improve research into amyotrophic lateral sclerosis, also known as ALS, and spinal muscular atrophy, or SMA, because both diseases damage hindbrain neurons.
“Now we have a model to better understand these devastating diseases, and work toward regenerative therapies for them,” co-first author Rayyan Jokhai said.
Evidence of the same developmental division was found in chickens, zebrafish and acorn worms, tracing the pattern back more than 500 million years.
“Our research suggests that evolution took two existing neural systems and pushed them together spatially,” Loh said. “We rely on this primordial way to make the brain as two separate pieces.”
Earlier, Qazinform News Agency reported that human brain immune cells known as microglia can take four to eight years to mature, compared with only about three weeks in mice, a difference that may contribute to humans’ advanced cognitive abilities.