Are egg cells in aging primates protected from mutations?

The increases in the number of egg cells in aging rhesus monkeys are not as large as those seen in non-reproductive cells, but they do occur at a certain age. A new study using incredibly accurate DNA sequencing methodology suggests that there may be a protective mechanism that keeps the mutation rate in reproductive cells relatively lower compared to other tissues in primates, a fact that could be related to the primate.

Kateryna Makova, Verne M. Willaman said that because of the diseases in humans caused by mutations in the mitochondrial genome and the trend in modern human societies to have children at an older age, it's vital to understand how mutations accumulate with age.

For a long time, my lab has been interested in studying the different types of genes. A paper about the study led by researchers at Penn State appeared online the week of April 4, 2022.

Mitochondria are the powerhouse of the cell because of their role in energy production, and they have a genome of their own separate from the cell's nuclear genome. It's difficult to study new mutations because they are hard to distinguish from the true ones, which can occur at a higher rate.

The method we used to overcome this difficulty was calledduplex sequencing, and it was used by Barbara Arbeithuber, who is now a research group leader at Johannes Kepler University Linz in Austria. We compare the two strands individually and then build a consensus sequence for each strand. Errors are not likely to happen at the same place on both strands, so when we see change on both strands, we can be confident that it is a true mutation.

In rhesus macaques that ranged in age from 1 to 23 years, the team was able to sequence the mitochondrial genome from muscle cells, liver cells, and oocytes. The age range covers the entire reproductive lifespan of monkeys. When animals died of natural causes or were sacrificed because of diseases not related to reproduction, the primate research centers collected the tissue for the study. Oocytes and not sperm cells were used.

As the macaques aged, the researchers saw an increase in the frequencies of their genes. The most dramatic change was the 3.5-fold increase in the number of mutations. Over the same time period, the muscle's mutation frequencies increased by more than twofold. At the age of nine, the mutation frequency in oocytes increased by 2.5 times.

Oocytes are special cells that are generated prior to birth and sit in the ovary for many years. You would expect them to accumulate a lot of mutations over that time, but instead we see that they do not. It seems that the germ line may be more resistant than we thought.

The research team found that there was variation in the rate of mutations across the mitochondrial genome, as well as a number of areas where the rate of change was much more frequent than you would expect. The region where one of the hotspots was located was responsible for copying of the Mitochondrial genomes.

It is very challenging to do a study like this in humans, but using a primate model gives us a close approximation. The precise mechanism leading to the plateau in oocytes remains enigmatic, but it might act at the level of elimination of defects.

More information: Advanced age increases frequencies of de novo mitochondrial 2 mutations in macaque oocytes and somatic tissues, Proceedings of the National Academy of Sciences (2022). doi.org/10.1073/pnas.2118740119 Journal information: Proceedings of the National Academy of Sciences Citation: Are egg cells in aging primates protected from mutations? (2022, April 4) retrieved 5 April 2022 from https://phys.org/news/2022-04-egg-cells-aging-primates-mutations.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.