A study shows that mitochondrial DNA can be transmitted to fathers – what does this mean for genetics?

Some things you learn at school are false, for example, there are only five senses or three states of matter. Advanced research has now been added to the list, proving that mitochondria (the sources of energy in our cells) came from both our parents and not – as students of biology are taught – from our mothers only.

The research, published in PNAS, conclusively showed that in three unrelated families, mitochondria of the father's sperm had been transmitted to the children for several generations. Reversing the scientific understanding of this fundamental "truth" paves the way for better treatment of mitochondrial disorders, which devastate many families with devastating disease.

Mitochondria convert the sugars, fats and proteins we consume into molecules that our cells use to self-feed. So, when they have gone wrong, the result is often catastrophic, resulting in lifetime problems or even the death of a touched baby in the womb.

MELAS syndrome, for example, begins in infancy and results in seizures and dementia. Kearns-Sayre syndrome causes vision and hearing problems, leaving the subject blind and deaf.

The DNA of a cell is largely contained in its nucleus, but the mitochondria are found separately inside the cell and have their own DNA. Indeed, mitochondria are thought to have started as distinct organisms, which entered the first cells about 1.45 billion years ago and never left. They breed and pbad from one generation to the next by "hitching a lift" in the egg.

During fertilization, the father's sperm transfers his sperm. The DNA in an egg, but little or no sperm mitochondria enter it. Where appropriate, there are mechanisms designed to destroy them. The new research found that in a small number of families, the father's mitochondria in the egg were not destroyed, although we still do not know enough to say why. There was also evidence that this mitochondrial DNA from the father might have been copied while the fertilized egg would become an even larger embryo than the mother's.

It is possible that previous research has also uncovered examples of mitochondrial transmission. fathers but that these results were expected and badumed to result from the contamination of the sample. But with ever increasing technological progress, a cheaper and more thorough DNA badysis is possible. It is therefore likely that more and more cases will now be reported.

This work could affect scientists studying the movement of human beings around the planet. Human mitochondrial DNA tends to change very little over time because even very small changes are often fatal and are not transmitted to future generations. This means that a person's mitochondrial DNA will probably be very similar to that of his distant ancestors and other people from his ethnic group.

Thus, by studying mitochondrial DNA in different populations, scientists were also able to follow the movement of these groups. around the world and even identify a potential female common ancestor for all humans, called "mitochondrial watch". All of this work, however, is based on the fact that mitochondria transmit only the female line, which we now know to be false.

Better Treatments

The most important consequences of these results are staggering. because a better understanding of how mitochondria are transmitted gives us a much better chance of developing treatments for mitochondrial disorders. It may even be possible to encourage properly functioning mitochondria to multiply in a fertilized egg at the expense of broken eggs.

Any treatment would probably be controversial because it would involve influencing a person's DNA in order to inherit it subsequently. generations. But the only other current treatment is also controversial and involves inserting the nucleus of a fertilized egg into a donor egg containing normal mitochondria. This is often described as producing "three-parent babies" and is not allowed in most countries, although the first baby of this type was born in April 2016. It may therefore be best to handle mitochondria from the parent.

With regard to the use of mitochondrial DNA to study human evolution and migration, the scarcity of cases identified by the new study means that it will have no impact important on our understanding of this area. But if further research suggests that father's legacy of mitochondrial DNA is more common, it may be necessary to change our understanding of human migration.