Researchers believed this didn’t happen long before humans split from their primate relatives, but a study has proven otherwise. The DNA of our mitochondria, these tiny cellular batteries, can integrate into our “core” DNA in the nucleus. The latter acts as a bandage when damaged, mitochondrial DNA can also cause cancer.
“About one in 4,000 births.”comments Science and the future Patrick Chinnery led the work published in the journal Nature. However, the frequency with which mitochondrial DNA (mtDNA) is introduced into the nucleus of one of our gametes, then the DNA it contains. The modified DNA is then passed on to offspring.
To understand, we must remember that each of our cells contains a nucleus, whose membrane contains pores and our long and essential DNA molecule. Surrounding it are several hundred mitochondria, the cell’s energy sources, each protected by its own membrane. Each of these mitochondria contains mtDNA, a DNA molecule uniquely inherited from its mother. However, in 2018, the works were published PNAS Detect paternally inherited mtDNA. How is that possible?
NUMTs, these insertions of mitochondrial DNA into nuclear DNA
To unravel this mystery, the team analyzed the genomes of more than 66,000 Britons, including more than 12,000 cancer patients, to find fragments of mtDNA. These insertions, known as NUMTs (“nuclear mitochondrial compartments”) were until then “considered an ancient relic” past insertions, “are often shared between related species”, researchers explain. Therefore, these NUMTs must have existed before our human ancestors split from the apes, and even before that, as mitochondria appeared in our cells (as well as animals and plants) dating back 1.45 billion years. But then, all humans must have the same NUMTs. This is not what scientists have discovered.
More than 90% of insertions are recent
Of the 1,637 NUMTs found in these DNAs, ““More than 90% (…) were inserted into the nuclear genome after the divergence between humans and other animals.”The researchers report in the publication.