This ‘Junk’ DNA Makes Up 8% Of the Human Genome. It’s Absolutely Crucial to Our Lives.

dna strand
This ‘Junk’ DNA May Be Vital to Life on Earthdeliormanli - Getty Images
  • Some 8 to 10 percent of our DNA is actually leftover from ancient viruses that co-evolved with animal DNA for hundreds of a millions of years.

  • While scientists have long thought this DNA was “junk,” as it appeared to have no discernible function, a new study from the Spanish National Cancer Research Centre has revealed that these “endogenous retroviruses” are vital to embryonic development.

  • Understanding this important function could help researchers to create advancements in artificial embryos and regenerative medicine.

Although the DNA found throughout our bodies contains the biological blueprint that makes us who we are, it’s not exactly a clean spec sheet. All kinds of stuff that appears to have no function at all has made its way into our DNA over millions of years, and nearly half of our DNA has been previously dismissed as ‘junk.’

However, some scientists have begun questioning the inconsequential nature of this ‘dark matter’ of the genetic world. Scientists at the Spanish National Cancer Research Centre (CNIO) have discovered that the pieces of junk DNA that one might think should be the most detrimental—leftover material from ancient viruses—actually play a vital role in embryonic development. As these ‘endogenous retroviruses’ make up roughly 8 percent of our total DNA, the finding elevates this ‘junk’ DNA into a biological mechanism of utmost importance. The results were published on Wednesday in the journal Science Advances.

“Until recently, these viral remnants were considered to be ‘junk DNA,’ genetic material that was unusable or even harmful,” first author Sergio De la Rosa said in a press statement. “Intuitively, it was thought that having viruses in the genome could not be good. However, in recent years we are starting to realize that these retroviruses, which have co-evolved with us over millions of years, have important functions, such as regulating other genes.”

Although hard to fathom, you’re technically around 8 to 10 percent retrovirus. 500 million years ago, during the Cambrian Explosion, genetic material from ancient viruses integrated into animal DNA. Over the course of many geologic eras, this material co-evolved together and eventually gave rise to, well, us. And that’s a good thing, because this new study discovers that one retrovirus—the MERVL endogenous retrovirus—essentially “sets the pace” when it comes to embryonic development.

Hours after fertilization, a cell in the ovary called the oocyte transitions from two totipotent cells (which can “give rise” to any kind of cell in an adult body) to four pluripotent cells (which can “give rise” to any kind of cell in any body or embryo). This development is controlled by a URI gene, which is essentially modulated by this retrovirus. That means: no retrovirus, no you and me.

“It is a totally new role for endogenous retroviruses,” study co-author Nabil Djouder said in a press statement. “We discovered a new mechanism that explains how an endogenous retrovirus directly controls pluripotency factors.”

This new, critical role for retroviruses in human embryonic development could be big news for developing regenerative medicines or artificial embryos. And in a world that’s definitely filled with lots of bad news surrounding viruses, it’s important to remember their strange and amazing role in making life on Earth possible.

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