We may have diverged from 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 Biomedical Sciences Research Center (BSRC Flemming) in Greece and Trinity College Dublin, Ireland have identified 155 genes in our genome that arose from small sections of non-coding DNA. Many appear to play critical roles in our biology, revealing how entirely new genes can rapidly evolve to become essential.
New genes typically arise through well-known mechanisms such as duplication eventswhere our genetic machinery accidentally produces copies of pre-existing genes that can end up adapting to new functions over time.
But the 155 microgenes identified in this study appear to have appeared from scratch, in stretches of DNA that did not previously contain instructions that our bodies use to build molecules.
Since the proteins thought to code for these new genes would be incredibly small, these DNA sequences are hard to find and difficult to study and are therefore often overlooked in research.
“This project started in 2017 because I was interested in the evolution of new genes and finding out how these genes originate.” says evolutionary geneticist Nikolaos Vakirlisfrom BSRC Flemming in Greece.
“It was frozen for a few years, until another study was published that had some very interesting data, which allowed us to get started on this work.”
That another studypublished in 2020 by a team of researchers at the University of California, San Francisco, cataloged a stack of microproteins produced by non-coding regions once described as ‘junk DNA’.
The team behind this new study subsequently created a genetic ancestral tree to compare those tiny sequences found in our genomes with those of 99 other vertebrate species, tracking the evolution of genes over time.
Some of the new ‘microgenes’ identified in this new study can be traced back to the earliest days of mammals, while others are more recent additions. Two of the genes identified by the study appear to have arisen from the split between humans and chimpanzees, the researchers found.
“We sought to identify and examine instances in the human lineage of small proteins that evolved from previously non-coding sequences and acquired function immediately or shortly thereafter,” the team writes in your published article.
“This is doubly important: for our understanding of the intriguing and still largely mysterious phenomenon of de novo gene birth, but also for our appreciation of the full functional potential of the human genome.”
Microproteins are already known to have a wide range of functions, from helping to regulate the expressions of other genes to joining forces with larger proteins, including our cell membranes. However, while some microproteins perform vital biological tasks, others are simply useless.
“When you start to get into these small sizes of DNA, they’re really on the edge of what can be interpreted from a genome sequence, and they’re in that zone where it’s hard to tell if it’s biologically significant.” Explain Aoife McLysaght, a geneticist at Trinity College Dublin.
A gene with a role in building our heart tissue arose when a common ancestor to humans and chimpanzees diverged from gorilla ancestry. If this microgene did in fact arose in 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 genes, one by one, in cells grown in the lab. Forty-four of the cell cultures showed growth defects, confirming that the now-missing sections of DNA play a critical role in keeping us functioning.
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 the DNA may suggest some connection to muscular dystrophy, retinitis pigmentosa, and Alazami syndrome, but further research will be required to clarify these relationships.
In light of modern technology and medicine, appreciating the scale of biological change humans have experienced as a species at the hands of natural selection can be challenging. But our physical state has been in big shape by pressure diet Y disease throughout the millennia, and will no doubt continue to adapt even within a technologically advanced world.
Exactly how the spontaneous creation of new genes within the non-coding region occurs is not yet clear, but with our new ability to track these genes, we may be closer to finding out.
“If we’re right in what we think we have here, there’s a lot more functionally relevant stuff hidden away in the human genome.” He says McLysaght.
The research has been published in cell reports.
