A new route to evolution: How DNA from our mitochondria works its way into our genomes

Some of the genetic code from our cells'batteries, which power our cells, can be found in one in every 4,000 births.

According to a study published today in Nature, researchers at the University of Cambridge and Queen Mary University of London found that some cancer genes have the same type of mitochondrial DNA as our genetic code.

Mitochondria are tiny 'organelles' that sit within our cells, where they act like batteries, providing energy in the form of the moleculeATP to power the cells The rest of the human genome is comprised of nuclear DNA, which is distinct from the Mitochondrion's mitochondrial DNA.

We inherit our mothers' genes from our fathers. The Cincinnati Children's Hospital Medical Center in the U.S. published a study in PNAS in which it was claimed that some of the paternal line had passed on their genes.

The Cambridge team looked at the genomes of 11,000 families recruited to the 100,000 Genomes Project to see if there were any patterns that looked like paternal inheritance. Mitochondrial DNA was found in the nuclear DNA of some children that weren't their parents. The US team might have reached the wrong conclusions, because what they had observed were not paternally-inherited mitochondrial DNA.

The team showed that the new inserts are actually happing all the time, showing a new way our genomes evolve.

Professor Patrick Chinnery from the Medical Research Council Mitochondrial Biology Unit and Department of Clinical Neurosciences at the University of Cambridge said that a primitive animal cell took in a bacterium that became what we now call mitochondria. The energy supplied to the cell allows it to function normally while removing oxygen which is toxic at high levels. The cell nucleus has bits of primitive mitochondria that allow their genomes to communicate.

This was thought to have happened a long time ago, but we have discovered that is not the case. We can see this happening right now, with bits of our genetic code going into the nuclear genome.

In every 4,000 births, the team estimates that mitochondrial and nuclear DNA transfer to each other. The team found that most of us carry five of the new inserts and one in seven of us carry very recent ones. A rare genetic form of cancer is one of the rare diseases that can be caused by the inserts.

Professor Chinnery says it is likely that the mother's egg cells will contain the mitochondrial DNA.

Mitochondrial DNA is more common in tumors than in other diseases, and in some cases it can cause the cancer.

The nuclear genetic code is being repaired all the time. The nuclear genetic code can be repaired with the help ofMitochondrial DNA. Sometimes this works, but on rare occasions it can make things worse.

The majority of the inserteds were in the regions of the genome that code for proteins The majority of the time, the body recognizes the invaders and silences them with a process known as methylation, in which a molecule sticks itself to the insert. Viruses insert themselves into our genes. Some of the mitochondrial DNA inserts go on to be copied and moved around the nucleus, which is not a good thing.

The team didn't find any evidence that the reverse could happen. There are a number of reasons why this should happen.

Cells only have two copies of nuclear DNA, but thousands of copies of Mitochondrial DNA, so the chances of them being broken and passing into the nucleus are much higher than the other way around.

It would be hard for nuclear DNA to get in because there are no holes in the membranes. If nuclear DNA is able to get out, holes in the membranes surrounding it would allow it to pass through with ease.

The 100,000 Genomes Project has unlocked the interplay between the genes in the nucleus of the cell. A new role in DNA repair is defined by this, but also one that could occasionally cause diseases.

More information: Patrick Chinnery, Nuclear-embedded mitochondrial DNA sequences in 66,083 human genomes, Nature (2022). DOI: 10.1038/s41586-022-05288-7. www.nature.com/articles/s41586-022-05288-7 Citation: A new route to evolution: How DNA from our mitochondria works its way into our genomes (2022, October 5) retrieved 5 October 2022 from https://phys.org/news/2022-10-route-evolution-dna-mitochondria-genomes.html This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only.