Human beings and chimpanzees share more than 96% of their protein-coding DNA, yet human brains are approximately 3 times bigger and much more complicated. New research study led by Lund University researchers recommends that part of the description might depend on a viral infection that struck chimpanzee forefathers countless years back and never ever reached ours.
Gerdes et alprogram that LINC00662a human-specific records revealed throughout brain advancement, contributes in neuronal maturation, axon outgrowth, and neural organoid advancement. Image credit: Johannes Sobotta.
“Over the previous 5 to 7 million years, people and chimpanzees have actually diverged in brain size, structure, and cognition in spite of high preservation of protein-coding genes,”stated Lund University’s Professor Johan Jakobsson, senior author of the research study.
“A big percentage of primate genome series is comprised of transposable aspects, with one significant household being endogenous retroviruses, which have actually broadened throughout primate development.”
“In people and chimpanzees, a minimum of 8% of the genome includes retroviruses.”
In their research study, Professor Jakobsson and his coworkers concentrated on a retrovirus called PTERV1.
It attacked the bacterium line of African ape forefathers approximately 5 to 7 million years back and left behind its hereditary code.
The chimpanzee genome brings a minimum of 150 insertions of PTERV1, while the human genome has none.
“The infection we examined particularly impacted chimpanzees,” Professor Jakobsson stated.
“Yet people and chimpanzees have mostly the very same hereditary makeup. That is why it is necessary to comprehend the distinctions in how genes are managed.”
The scientists grew little clusters of establishing brain tissue, referred to as neural organoids, from stem cells of chimpanzees and human beings.
Utilizing long-read DNA sequencing, they discovered that almost all PTERV1 insertions they recognized in the chimpanzee genome were greatly chemically tagged with methyl groups, a mark related to gene silencing.
The researchers then tried to find genes which contain a PTERV1 insertion and act in a different way in the 2 types.
LINC00662a gene that produces a long noncoding RNA, stuck out. It was extremely active in human organoids however quiet in chimpanzee ones.
In chimpanzees, an approximately 7,000-letter viral insertion sits inside the gene, and the DNA around it is greatly methylated.
The insertion seems present in chimpanzees and bonobos however not in other apes analyzed.
“The gene was highly revealed in the human organoids, however not in the chimpanzee organoids,” stated very first author Patricia Gerdes, a postdoctoral scientist at Lund University.
In human cells, LINC00662 was most active in early fetal brain advancement.
When the scientists silenced the gene in human organoids, tissue at 30 days revealed weaker staining for a marker of young nerve cells in the area where brand-new nerve cells extend fibers.
Genes associated with axon and dendrite development were more active, which they analyze as a possible offsetting reaction.
“Our findings expose a system by which endogenous retroviral insertions added to human-chimpanzee brain divergence,” the researchers concluded.
The research study was released October 23 in the journal Science Advances
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Patricia Gerdes et al2026. Retroviral insertions added to the divergence of human and chimpanzee brains. Science Advances 12 (43 ); doi: 10.1126/ sciadv.aeg5791
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