What’s missing from the human genome compared to the genomes of other primates could have been just as crucial to humanity’s development as what’s been added during our evolutionary history, according to a new study led by researchers at Yale and the Broad Institute. from MIT and Harvard.
The new findings, published April 28 in the journal Science, fill an important gap in what is known about historical changes in the human genome. While a revolution in the ability to collect data from the genomes of different species has allowed scientists to identify additions that are specific to the human genome, such as a gene that was instrumental in humans developing the ability to speak, less attention has been paid. . paid to what is missing in the human genome.
For the new study, the researchers used an even deeper genomic dive into primate DNA to show that the loss of around 10,000 bits of genetic information, most as small as a few DNA base pairs, over the course of of our evolutionary history differentiate humans from chimpanzees, our closest primate relative. Some of those “deleted” pieces of genetic information are closely related to genes involved in neural and cognitive functions, including one associated with the formation of cells in the developing brain.
These 10,000 missing pieces of DNA, which are present in the genomes of other mammals, are common to all humans, the Yale team found.
The fact that these gene deletions have been conserved in all humans, the authors say, attests to their evolutionary importance, suggesting that they conferred some biological advantage.
“We often think that new biological functions must require new pieces of DNA, but this work shows us that knocking out the genetic code can have profound consequences for the traits that make us unique as a species,” said Steven Reilly, an assistant professor of genetics at the Yale School. of Medicine and main author of the article.
The paper was one of several published in Science by the Zoonomia Project, an international research collaboration that catalogs the diversity in mammalian genomes by comparing the DNA sequences of 240 species of mammals that exist today.
In their study, the Yale team found that some genetic sequences found in the genomes of most other mammalian species, from mice to whales, disappeared in humans. But instead of altering human biology, they say, some of these deletions created new genetic codings that removed elements that would normally turn genes off.
Removing this genetic information, Reilly said, had an effect equivalent to removing three characters, “n’t,” from the word “isn’t” to create a new word, “is.”
“[Such deletions] can slightly modify the meaning of the instructions on how to make a human being, which helps explain our larger brains and complex cognition,” he said.
The researchers used a technology called Massively Parallel Reporter Assays (MPRA), which can simultaneously detect and measure the function of thousands of genetic changes between species.
“These tools have the ability to allow us to begin to identify the many small molecular building blocks that make us unique as a species,” Reilly said.
James Xue of the Broad Institute is the lead author of the study.
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