How paternal mitochondria disappear

Geneticists have found out why the DNA of special intracellular structures – mitochondria – is inherited on the maternal side

Marina Astvatsaturyan, Echo of Moscow, based on AAAS materials: Why fathers don't pass on mitochondria to offspring

Geneticists have found out why mitochondrial DNA is usually inherited from the maternal line – this fundamental question has occupied researchers for more than half a century

Studying the reproduction of the roundworm Caenorhabditis elegans, scientists from the University of Colorado Boulder and their colleagues from other scientific centers discovered a new function in the well-known cps–6 gene - encoding of the mitochondrial endonuclease enzyme, which destroys the mitochondrial DNA of the sperm immediately after it fertilizes the egg.

Normally, the protein encoded by the cps-6 gene controls the process of programmed cell death, thanks to which the body maintains the balance of old and new cells. But Ding Xue from Boulder noticed that during fertilization in worms, the CPS-6 protein penetrates into the inner part of the mitochondria and cuts the DNA there into pieces. Without instructions written on intact DNA, mitochondria cannot perform their functions.

Reporting this discovery in the journal Science (Zhou et al., Mitochondrial endonuclease G mediates breakdown of paternal mitochondria upon fertilization), the authors of the study note that the delay in the destruction of paternal mitochondrial DNA can be fatal for the embryo. Until now, it was known that inheritance on the maternal side is controlled by the processes that occur in the maternal germ cell, and the paternal mitochondria are absorbed by large intracellular structures, autophagosomes, as soon as the sperm enters the egg.

However, in a study by Professor Xue and colleagues, it was shown that the paternal mitochondria in roundworms begin to collapse before any autophagosome overtakes them. "It's like a suicide mechanism," says another author of the publication, Byung-Ho Kang from the Chinese University of Hong Kong.

The moment of the beginning of the self-destruction of the paternal mitochondria was observed by studying worms using an electron microscope and a tomograph. But a key component of this process, the cps-6 gene was detected by RNA profile analysis. When the gene was deleted, that is, removed, the paternal mitochondria survived, but this was accompanied by an increase in the frequency of embryo death.

As the authors write, "evidence has been obtained that the survival of paternal mitochondria threatens the development of animals, but the destruction of their DNA can stimulate the inheritance of mitochondria on the maternal side." "It remains to be seen that the same thing happens in humans," says Science News expert Vincent Galy from Pierre and Marie Curie University in Paris. "One can imagine such a mechanism, but it has not yet been demonstrated," the scientist adds.

Portal "Eternal youth" http://vechnayamolodost.ru  08.07.2016