Using lab-grown mini-brains, scientists have discovered why humans have larger brains than clowns.
About 5 million to 8 million years ago, humans and Ape Different from a common ancestor. Some time after that, humans began to develop larger brains; Now The human brain About three times the size of a chimpanzee’s brain, our closest relatives.
“The most obvious answer is size,” said Sylvia Benito-Kiwinski, lead author of the postcolonial researcher in molecular biology at the MRC Laboratory in the United Kingdom. “The big brain has been strongly selected and so it seems that our big brain has something to do with our unique cognitive abilities.”
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2.6 million and 11,700 years ago, the human brain grew, doubling in size, Formerly a living science report. Due to the lack of fossil records of the period of expansion of the human brain, scientists cannot easily decipher What Humans were asked to grow big brains; But in modern times, we can see now how Our brain develops differently than the clown brain.
Benito-Kvinsinski told living science that in the early stages of development, human and ape-like brains grow rapidly in the surface area, scientists hypothesized that differences occur very soon after conception, before cells mature into brain cells. Benito-Quisinski told living science. But because early human and ape fetal brain tissue is not readily accessible for research, previous studies have focused primarily on subsequent developmental stages when neurons already form the brain landscape.
But the advent of organoid technology, which is a sample of organ grown in the lab, now makes it possible to look at these earlier stages. Scientists make these brain organoids from stem cells or cells that can morph into any type of cell in the body, and reprogram those cells to grow into brain-like structures.
While this is not a real brain, it is still an impressive copy; Previously, scientists have created brain organoids that can grow their own blood vessels or produce their own brain waves. Living science previously reported.
In a new study, Sylvia Benito-Quinkiski chimpanzee’s “minibrains” increased, Gorilla And lab men (this is the first time a gorilla brain organoid has been created). Before mature stem cells mature in brain cells – they mimic the early stages of the embryonic body that began with a 3D ball of cells called embroidered bodies. They then placed these cells in gel matrices and allowed them to develop “emerging structures” or neural progenitor cells, which are stem cells that would eventually turn into brain cells.
“The reason these progenitor cells are interesting depends, after all, on the number of neurons produced.[s] On the number of progenitor cells, said Benito-Kivinsinski. “In other words, the more often the progenitors divide, the more neurons eventually form. These progenitor cells are cylindrical in shape, but as they mature, they begin to lengthen. And become more spindle-like. .
These elongated cells are much slower to divide than their cylindrical precursors. Eventually, spindle-like cells become fully developed neurons.
Researchers have found that in the human brain, neural progenitor cells take a few days to mature into slow-dividing enlarged cells than in chimpanzee and gorilla brains.
Benito-Kivinsky said, “It seems as if humans are delayed in transition,” in a spindle-like shape. In this extra time before the transition, the cells of the human race divide more than their equivalent counterparts, forming more cells that mature into brain cells, and therefore larger brains.
To understand why, researchers looked at genes that turned on and off during this early stage of brain development in different organisms. They found that the ZEB2 gene was turned on in gorilla brain organoids earlier than in human organoids. “ZB2” seems to be the regulator of this cell shape change, “said Benito-Kivinsky.
Sure enough, while researchers delayed the activation of ZB2 in gorilla progenitor cells, the transition to enlarged cells took longer, with gorilla organoid cells growing more like human organoid cells. When they quickly converted JUB2 into human organoids, the opposite happened: the cells of human organoids began to grow more like the cells of molecular organoids, i.e. they migrated rapidly into enlarged cells.
It is not clear how, after being released from the clutches of humans, the expression of this gene began to change; And he doesn’t even know that other genes are involved. Benito-Kivinsky and his team now hope to understand what controls the expression of ZEB2, and therefore why these genes are expressed later in humans.
The findings were published in the journal Wednesday (March 24) Cell.
Published on Original Living Science.
