A new study published in Science identifies a possible explanation for why large breed dogs live shorter than small ones. The authors suggest that, with age, their DNA more quickly loses some chemical “tags” that control so-called “jumping genes”.
There can be tens of kilos of difference between a Chihuahua and a Great Dane, but also a notable one difference in lifespan. In general, in fact, small breed dogs live longer of large ones, a phenomenon that has long intrigued scientists. But what does it depend on? A new study published in the journal Science suggests a possible explanation: As dogs age, they lose some DNA chemical signals which help regulate its functioning. This process appears to be faster in large breeds and involves in particular certain genetic sequences called LINE1also known as “hopping geniuses“. Research, conducted by analyzing the DNA of almost 900 dogscould help us better understand not only why our four-legged friends age at different rates, but also some of the mechanisms of aging in mammals in general.
“Jumping genes” and their role in the aging of large breed dogs
To understand what scientists have discovered, we must imagine the DNA like a huge instruction manual that cells use to function. Not all instructions, however, are read at the same time: the organism has different mechanisms to regulate which genes to activate and which to keep under control. One of these is the DNA methylationa chemical process that consists of adding a precise group of atoms, called methyl groupat certain points in the DNA. It’s a bit like applying labels, which help regulate the use of genetic instructions without changing their letters.
As the years pass, some of these labels may be lost. And this could also have consequences on particular DNA sequences called transposable elementsnicknamed “hopping genes” because they can move or produce new copies in other areas of the genome. Among these we find LINE1, elements which, when they become active, can insert themselves into new positions and interfere with the functioning of DNA. Normally, methylation helps keep them in check.
To understand how this system changes over time, the researchers studied the DNA methylation patterns of approximately 900 dogs involved in the Dog Aging Project. The results showed that larger dogs had a demethylation of transposable elements associated with the age of 31% stronger than smaller dogs.
In other words, larger dogs appear to lose some of the chemical signals that help control these genetic elements more quickly. This could be one of the reasons why they age earlier, even if the study does not yet demonstrate a direct cause-effect relationship: further research will be needed to understand whether the loss of methylation really contributes to shortening the lives of dogs.
The possible link with human aging: DNA studies
Studying the aging of dogs could help us understand that of humans too. Indeed, dogs and people they share many biological mechanisms. Additionally, dogs often live in the same environments as us and are exposed to some similar environmental factors. Differences in lifespan between breeds of the same species therefore offer researchers a valuable opportunity to study which biological processes are associated with more rapid aging.
If further studies confirm that LINE1 actively contributes to the aging process, the mechanisms that keep them under control could become an interesting starting point for new research on health and longevity. For now, however, we don’t know whether intervening on these elements can really extend life.
