We may have parted ways with our primate cousins millions of years ago, but a new study shows how humans continue to evolve in ways we never imagined.
Researchers at the Alexander Fleming (BSRC Flemming) Biomedical Sciences Research Center in Greece and Trinity College Dublin in Ireland have identified 155 genes in our genome that arise from small non-coding segments of DNA. Many play a critical role in our biology and reveal how quickly entirely new genes can evolve.
New genes usually arise through mechanisms known as recurrence eventswhere our genetic machinery accidentally produces copies of preexisting genes that can adapt to new functions over time.
However, the 155 microgenes identified in this study appear to have emerged from scratch in DNA. previously did not contain instructions which our body uses to make molecules.
Because the proteins encoded by these new genes will be incredibly small, these DNA sequences hard to find and difficult to study and therefore often overlooked in research.
“This project started in 2017 because I was interested in new gene evolution and understanding how these genes arise” says evolutionary geneticist Nikolaos VakirlisFrom BSRC Flemming in Greece.
“It was put on ice for a few years until another study was published with very interesting data that allowed this work to begin.”
This other researchPublished in 2020 by a team of researchers at the University of California, San Francisco, it cataloged a cluster of microproteins produced by non-coding regions. once described as “junk DNA”..
The team behind this new study then created a genetic ancestry tree to trace the evolution of genes over time to compare the small sequences found in our genomes with those found in 99 other vertebrate species.
Some of the new “microgenes” identified in this new study can be traced back to the earliest times of mammals, while others are more recent additions. The researchers found that two of the genes identified in the study appeared after the human-chimpanzee split.
“We sought to identify and investigate cases of human progeny of small proteins that arise from previously non-coding sequences and gain function either immediately or shortly thereafter,” the team writes. their published article.
“This is doubly important: to understand the fascinating and still mysterious phenomenon of de novo gene birth, but also to appreciate the full functional potential of the human genome.”
Microproteins are now known to have a variety of functions, from helping to regulate the expression of other genes to associating with larger proteins, including our cell membranes. However, while some microproteins perform vital biological tasks, others are clearly useless.
“When you start getting into these small sizes of DNA, they’re really at the edge of what can be interpreted from genome sequencing, and they’re in the zone where it’s hard to know if it’s biologically meaningful.” you explain Trinity College Dublin geneticist Aoife McLysaght.
A gene that plays a role in building our heart tissue emerged when a common ancestor for humans and chimpanzees branched off from a gorilla ancestor. If indeed this microgene emerged within the last few million years, it is striking evidence that these evolving parts of our DNA can quickly become essential to the body.
The researchers then tested the functions of the sequences by deleting the genes one by one in lab-grown cells. 44 of the cell cultures continued to show growth defects, confirming that the now-missing parts of the DNA play an important role in how we function.
In other comparative analyses, the researchers also identified variants known to be associated with the disease in three of the new genes. The presence of these random mutations at a single base position in DNA may suggest some association with muscular dystrophy, retinitis pigmentosa, and Alazami syndrome, but further studies will be needed to clarify these links.
In light of modern technology and medicine, it can be difficult to appreciate the extent of the biological changes humans have experienced as a species at the hands of natural selection. But we had fitness significantly formed with pressures from the diet and disease for millennia and will undoubtedly continue to adapt even in a technologically advanced world.
Exactly how the spontaneous creation of new genes in the non-coding region occurs is not yet clear, but with our newfound ability to monitor these genes, we may be closer to finding out.
“If we’re right about what we think is here, there’s a lot more functionally related stuff hiding in the human genome.” he says McLysaght.
The study was published Cell reports.
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