Study: "jumping genes" may speed up ageing in large dog breeds
Researchers at Arizona State University in the US, analysing the DNA of 894 dogs, found that methylation loss around LINE1 elements is faster in large breeds. This may partly explain why small dogs live longer.
Scientists have identified a possible explanation for why small dog breeds usually live longer than large ones: in bigger dogs, signs of ageing appear faster at the genetic level. The research was carried out by Arizona State University (US) scientists, who analysed genetic material from 894 dogs. The portal "HVG" reported on the findings.
An unusual pattern in the animal world
In dogs, smaller breeds live longer, even though among mammals in general the opposite is usually true. Mice, for example, live only a few years, elephants about 70 years, and Greenland whales can reach as much as 200 years. Larger dog breeds typically grow faster, more often develop age-related diseases and have a shorter average lifespan.
What the researchers found
The scientists studied DNA methylation, a process that regulates gene activity without changing the DNA structure itself. It is also used as an ageing biomarker. They paid particular attention to so-called "jumping genes", or LINE1 elements, which are mobile DNA fragments able to move around the genome or make copies of themselves. Their activity is normally restrained, including by DNA methylation. If this control weakens, the elements can become more active and potentially damage genetic material.
The study found that as dogs age, methylation levels fall in more than 40 percent of genome regions linked to LINE1 elements, and this happens at different rates in different dogs. In heavier dogs the loss was considerably faster: each year the decline was about 35 percent greater than in smaller dogs.
Co-author Blaise Mariner said this is one of the clearest molecular signals observed so far in connection with canine ageing. In his view, the results suggest that faster ageing in large breeds may be at least partly linked to a weakened ability of the body to control these elements.
Relevance for humans and limitations
The scientists suggest the mechanism could matter for other mammals too, including humans. If further studies confirm that LINE1 activity plays a significant role in ageing, therapies to control these elements might be developed in future. For now, the researchers stress that additional studies are needed to prove a direct causal link, and the finding does not mean a way to extend dogs' lives has been found. A dog's lifespan is still influenced by genetics, breed, size, health, diet and daily care.
