16 December 2019

Twice as long as it should be

A new study by Australian scientists from the State Association of Scientific and Applied Research (CSIRO), published in the journal Scientific Reports, showed how the DNA of an animal changes with age, how it varies from species to species and how it is related to the life span of an animal.

The Mystery of aging

As the animals grow older, there is a decrease in biological functions, leading to a limitation of their life expectancy. Until now, it has been difficult to determine how many years an animal can live.

DNA is an obvious place to look for information about aging. However, no one has been able to find differences in DNA sequences that explain the differences in life expectancy.

Life expectancy among vertebrates is very different. Thus, the dwarf bullhead fish (Eviota sigillata) lives for only eight weeks, while individual Greenland sharks (Somniosus microcephalus) live for more than 400 years.

Knowing the life span of wild animals is of great importance for wildlife conservation. In endangered species, it can be used to understand which populations are more viable. In fisheries, life expectancy is used in population models to determine catch limits.

However, the life expectancy of most animals is unknown. Many estimates were obtained from a small number of individuals living in captivity, whose age at the time of death was known. It is difficult to know the life expectancy of long-lived species, since they can outlive a generation of researchers.

Using DNA changes to measure age

Over the past few years, researchers have developed a "molecular clock" that can determine how old an animal is by a special type of change in DNA methylation.

DNA methylation is an epigenetic mechanism that does not change the main sequence of genes, but regulates their activity. DNA methylation in certain genes is associated with the maximum lifespan of some mammals, including primates.

It is known that aging is associated with epigenetic changes, but no research has so far used them as a method for estimating the life expectancy of animals.

In this study, scientists used the genomes of 252 vertebrate species that other researchers collected and made publicly available in an online database. Then they were compared with a database of known life expectancy of animals.

Using these data, the researchers found that it is possible to assume the lifespan of vertebrates by estimating the density of targets for methylation, CpG sites (cytosine and guanine separated by phosphate binding these two nucleotides), in the promoters of 42 specific genes. This method also allows us to estimate the life expectancy of long-lived and extinct species.


Extinct species

It was found that the estimated life expectancy of the bowhead whale, which is considered the longest-lived mammal in the world, is 268 years. This is 57 years higher than the oldest specimen found. The extinct woolly mammoth had a theoretical life expectancy of 60 years, which corresponds to the 65-year life of the modern African elephant. The extinct giant turtle of Pinta Island had a life expectancy of 120 years. The last representative of this species, Lonely George, died in 2012 at the age of 112.

Interestingly, Neanderthals and Denisovans, the extinct ancestors of modern man, had a maximum life expectancy of 37.8 years.

Based on DNA analysis, the researchers estimated the "natural" life expectancy of modern people at 38 years. This corresponds to some anthropological estimates for early modern humans. However, today people may be an exception to this study due to advances in medicine and lifestyle.

Thus, the life expectancy of many animals can be estimated using a new method. This is of great importance for wildlife conservation.

Article B.Mayne et al. A genomic predictor of lifespan in vertebrates is published in the journal Scientific Reports.

Aminat Adzhieva, portal "Eternal Youth" http://vechnayamolodost.ru based on The Conversation: A new study shows an animal's lifespan is written in the DNA. For humans, it’s 38 years.

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