Brain Expansion : from junk DNA genes (Evolution)

by David Turell , Friday, February 24, 2023, 15:38 (428 days ago) @ David Turell

A very important finding:

https://www.science.org/content/article/human-gene-linked-bigger-brains-was-born-seemin...

"Now, a study identifies mutations that transform seemingly useless DNA sequences into potential genes by endowing their encoded RNA with the skill to escape the cell nucleus—a critical step toward becoming translated into a protein. The study’s authors highlight 74 human protein genes that appear to have arisen in this de novo way—more than half of which emerged after the human lineage branched off from chimpanzees. Some of these newcomer genes may have played a role in the evolution of our relatively large and complex brains. When added to mice, one made the rodent brains grow bigger and more humanlike, the authors report this week in Nature Ecology & Evolution.

“'This work is a big advance,” says Anne-Ruxandra Carvunis, an evolutionary biologist at the University of Pittsburgh, who was not involved with the research. It “suggests that de novo gene birth may have played a role in human brain evolution.”

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"A decade ago, Chuan-Yun Li, an evolutionary biologist at Peking University, and colleagues discovered that some human protein genes bore a striking resemblance to DNA sequences in rhesus monkeys that got transcribed into long noncoding RNAs (lncRNAs), which didn’t make proteins or have any other apparent purpose. Li couldn’t figure out what it had taken for those stretches of monkey DNA to become true protein-coding genes in humans.

"A clue emerged when Li’s postdoc, Ni A. An, discovered that many lncRNAs have a hard time exiting the nucleus. The researchers used a sophisticated computer program to identify differences between protein-coding genes whose mRNA got out of the nucleus and the DNA sequences that produced RNAs that did not. The program homed in on stretches of DNA known as U1 elements, which when transcribed into RNA make the strand too sticky to make a clean escape. In protein-coding genes, these elements have mutations that make the RNA less sticky. So, for an lncRNA to escape the nucleus and give its instructions to a ribosome, the parental DNA must acquire those key U1 mutations or somehow make that transcribed section get cut out of the RNA strands altogether.

“'This makes perfect sense because for an RNA to be translated, it needs to go the cytoplasm [where ribosomes are found] first,” says Maria Del Mar Albà, an evolutionary biologist at Hospital del Mar Medical Research Institute.

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"Overall, the findings suggest these de novo human genes “may have a role in brain development and may have been a driver of cognition during the evolution of humans,” says Erich Bornberg-Bauer, an evolutionary biophysicist at the University of Münster.

"Manyuan Long, an evolutionary biologist at the University of Chicago, calls the new study “a breakthrough in the understanding of the molecular evolutionary processes that generate [new] genes.” In an indication of how widespread those processes may be, Long’s group has found that most of the recognizable de novo genes in rice were once lncRNAs, and that lncRNAs also helped form new genes in bamboo. But he is more cautious about interpreting the role of de novo genes in brain evolution. Organoids are far simpler tissues than the brain itself, he notes, and human and mouse brains have evolved along very different paths.

Comment: tremendously complex research. Could such a complex arrangement to invent a new gene have come from a chance search for a mutation? Looks like design with purpose to me. God, who had a goal to produce us, would do it exactly this way!