In 1 in 4000 births, mitochondrial DNA enters our genome

Researchers thought this hadn’t happened long before humans diverged from their primate cousins, but one study has proven just the opposite. The DNA from our mitochondria, those little batteries of cells, is able to integrate with our “main” DNA, which is contained in the cell’s nucleus. However, mitochondrial DNA can also cause cancer because it acts as a bond when damaged.

One in 4,000 births is a lot.”comments to science and future Patrick Chinnery, who directed this work published in the journal Nature. However, it is the frequency with which mitochondrial DNA (mtDNA) is introduced into the nucleus of one of our gametes and then into the DNA it contains. A modified DNA that is then passed on to offspring.

To understand this, we must remember that each of our cells contains a nucleus whose membrane is porous and which contains our long and essential DNA molecule. Surrounding them 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, work was published in PNAS Discover mtDNA inherited from the paternal line. How is it possible ?

NUMTs, these insertions of mitochondrial DNA into nuclear DNA

To solve this mystery, the team examined the genomes of more than 66,000 Britons, including more than 12,000 cancer patients, to find fragments of mtDNA. These inserts, called NUMTs (“nuclear mitochondrial segments”), were until then “considered ancient remains” past insertions,”often shared between related species”, the researchers explain. These NUMTs must therefore date from before our human ancestors differed from the apes, and possibly even earlier, since the mitochondria in our cells (as well as those of animals and plants) appeared and are 1.45 billion years old. But if so, all people should have the same NUMTs. The scientists didn’t find that out.

More than 90% of the insertions are new

Of 1,637 NUMTs found in these DNAs,”more than 90% (…) were inserted into the nuclear genome after divergence between humans and other primates”the researchers report in the publication.

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