Mutations In Animals Shed New Light on The Process of Aging

Genetic changes – known as somatic mutations – occur in all cells throughout the lifespan of an organism. While most of these mutations are harmless, some of them can impair normal cell functioning or even start a cell on the path to cancer.

Since the 1950s, scientists have speculated that these mutations may also play a role in aging processes. However, due to technological limitations, they could not properly test this hypothesis.

Now, a research team led by the Wellcome Sanger Institute has analyzed the genomes of 16 mammal species – ranging from mice, rats, and rabbits to horses, tigers, and giraffes – in order to shed more light on the role of these genetic changes in ageing.

They found that, despite huge variations in lifespan and size, different animal species tend to end their natural life with surprisingly similar numbers of somatic mutations. However, the results suggest that the longer the lifespan of a species, the slower the rate at which the mutations occur, thus lending support to the hypothesis that somatic mutations may play a crucial role in ageing.

“To find a similar pattern of genetic changes in animals as different from one another as a mouse and a tiger was surprising. But the most exciting aspect of the study has to be finding that lifespan is inversely proportional to the somatic mutation rate,” said study lead author Alex Cagan, a postdoctoral researcher on somatic evolution at the Wellcome Institute.

“This suggests that somatic mutations may play a role in ageing, although alternative explanations may be possible. Over the next few years, it will be fascinating to extend these studies into even more diverse species, such as insects or plants.”

“Animals often live much longer in zoos than they do in the wild, so our vets’ time is often spent dealing with conditions related to old age. The genetic changes identified in this study suggest that diseases of old age will be similar across a wide range of mammals, whether old age begins at seven months or 70 years, and will help us keep these animals happy and healthy in their later years,” added study co-author Simon Spiro, a wildlife veterinary pathologist at the Zoological Society of London.

Nevertheless, understanding the exact causes of ageing remains an unsolved question. Although somatic mutations appear to play a fundamental role in ageing, other processes such as protein aggregation and epigenetic changes are also likely to contribute to the molecular damage in our cells and tissues that is a well-known marker of old age. Further research is needed to compare the rates of all of these processes across species with different lifespans.

By Andrei Ionescu

Source: Mutations in animals shed new light on the process of aging • Earth.com

Critics:

By Catherine Barnette

Mutations can occur during the life of an animal (acquired—affecting only a single cell) or can be inherited from a parent (present in all of the body’s cells). When a cell is affected by a mutation, all cells arising from that cell are likely to carry the mutation. In the case of an acquired mutation, this may be only a small number of cells. In the case of a reproductive cell, the mutation will affect all of the offspring’s cells.

The effects of mutations depend on the size and location of the mutation. Much of an animal’s genetic code consists of what is called non-coding DNA. These non-coding regions do not contain genes that code for protein production. Mutations in this area may have no effect on the animal or its offspring.

If an acquired mutation occurs in a coding region of DNA, the effects will vary depending on the mutation. Perhaps the most concerning effect of an acquired mutation is the formation of cancer. For example, solar radiation damage can lead to cell mutations that may result in squamous cell carcinoma or other cancers.

Inherited mutations are mutations that occurred in a parent animal’s reproductive cells. These mutations are part of the genetic code that is found in every one of the offspring’s cells. For this reason, inherited mutations can have significant effects if found in vital, coding regions of the DNA.

A marker is a specific segment of DNA with known characteristics. While the specific sequences may vary between individual, there is enough consistency in the genetic code at that particular site on the genome to allow comparison between individuals. Markers are often located in non-coding areas of the DNA where a specific base pattern repeats many times and these repeating segments are known and mapped.

When a mutation occurs in a marker region, the mutation can be easily identified because the normal pattern of the repeating segment is known. Even if the marker region is located in non-coding DNA and the mutation has no visible effects, analyzing the marker region will allow scientists to see that a mutation has occurred.