Were the eggs of ancient primates protected from alterations?

Were the eggs of ancient primates protected from alterations?

A new study showed that the mutation frequency in mitochondrial DNA decreased, and increased less with age, in the precursors of the egg than in the cells of other organisms in the egg. primate. Mitochondrial DNA was sequenced in liver, bone marrow, and single oocyte samples from 1- to 23-year-old rhesus macaques. The new changes increased with age the faster the liver, and the slower the oocytes. Replication of oocytes is often increased until age 9. The source of replication (OriL), which is responsible for copying mitochondrial genomes, is known to be a hot spot of accumulation with age. in the liver. Photo: Barbara Arbeithuber

Recent changes are occurring in the increase in the mitochondrial genomes of developing egg cells in older rhesus monkeys, but the increase has been observed in recent years and has not been as large as including those found in non -reproductive cells, such as the flesh and liver. A new study using highly accurate DNA sequencing techniques suggests that there may be a barrier to keeping the mutation rate of reproductive cells very low compared to other tissues in the family. of primates, which is a fact related to primate – and therefore human – propensity that has re -emerged in recent years.

“Because human diseases are caused by changes in the mitochondrial genome and how new human groups have children in old age, it is important to understand how the collection of mutations with age, ”said Kateryna Makova, Verne M. Willaman Chair of Life Sciences at Penn State and leader of the research team.

“My lab has been interested in studying mutations – including mutations in mitochondrial DNA – for a long time. We’re also interested in evolution, so we wanted to see how mutations accumulate in mitochondrial DNA in reproductive cells because these changes can be passed down. The next generation. ” A paper describing the study, led by researchers at Penn State, will be available online the week of April 4, 2022 at Proceedings of the National Academy of Sciences.

Mitochondria are cellular organelles – often referred to as the cellular powerhouse because of their role in producing energy – have a genome that is very different from the “nuclear genome” of the cell, is in the nucleus and that is what we often think of. “ka” genome. Mitochondrial DNA mutations are associated with many human diseases but it is difficult to study the mutations because it is difficult for true mutations to be different from erroneous ones, which stand at a higher level compared to the mutation rate. for most sequencing technologies.

“To overcome this challenge, we used a technique called‘ duplex sequencing, ’” said Barbara Arbeithuber, a postdoctoral researcher at Penn State at the time of the study who is now a research team leader. and Johannes Kepler University Linz in Austria. “DNA is made up of two connecting strings, but most sequencing techniques only look at the sequences from one strand at a time. They can be the same location on the two strings, so we can see to the change in the two strings, we can be confident that it shows a real mutation. ”

The team isolated the mitochondrial genome from tissue, liver cells, and oocytes – precursor cells in the ovary that can become eggs – in rhesus macaques from 1 to at 23 years of age. These years mark almost the entire reproductive life of monkeys. The skins were collected to study for many years from primate clinics when animals died of natural causes and were sacrificed for non -birth diseases. Oocytes were used, not sperm cells, because mitochondria were only transmitted through the maternal line.

Overall, the researchers found that the mutation frequency increased in the muscles tested as the macaques aged. The most significant change was seen with a 3.5-fold increase in mutation frequency over the next 20 years. The mutation frequency in the meat was increased to 2.8 times at the same time. The mutation frequency in oocytes was increased by 2.5-fold up to nine years of age, during which time it was stable.

“From a reproductive biology perspective, oocytes are interesting and unique,” ​​said Francisco Diaz, associate professor of reproductive biology at Penn State. “They are formed before birth and live in the ovary for years and years and years, and then some of them are raised at each birth cycle. See how to collect changes for a while and then they don’t.This seems to indicate that the germ line – producers such as eggs and sperm – is more complex than we thought . ”

In addition to changing the magnitude of the mutation over time, the research team also found changes in mutation frequency across the mitochondrial genome, including hot spots where the mutation most often occurred. More than you might think in terms of the flesh. Some of the hottest spots in the world are responsible for copying mitochondrial genomes.

“While it’s very difficult to do a study like this in humans, using some kind of primate model gives us a closer look,” Makova said. “Our results show that primate oocytes have a function that protects or repairs their mitochondrial DNA, a mutation that helps allow for subsequent reproduction. In order to eliminate deficient mitochondria. or oocytes.


Recent changes are gathering in the breeding rooms of older mice


More information:
High age increases the 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

Presented by Pennsylvania State University

Directions: Were the eggs of ancient primates protected from alterations? (2022, April 4) Retrieved 4 April 2022 from https://phys.org/news/2022-04-egg-cells-aging-primates-mutations.html

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