A study of nearly 900 dogs has identified molecular differences that may help explain why larger breeds tend to have shorter lives than smaller ones. The research, led by scientists at Arizona State University and published in Science, examined DNA samples from dogs in the Dog Aging Project.
The team tracked DNA methylation--chemical marks that help regulate gene activity and change as animals age. These patterns enabled the researchers to estimate biological age, which was also associated with survival during the study's follow-up period.
DNA sequences that may lose their safeguards
The most notable size-related differences appeared in repetitive DNA sequences known as transposable elements. Some, including LINE1, can copy themselves and insert into other parts of the genome. Cells typically use methylation and other mechanisms to keep them in check.
As dogs aged, the researchers observed a decline in some of the chemical marks associated with controlling these sequences. The changes were more pronounced in larger dogs--about 31% greater overall, and 35% greater for LINE1-related regions--suggesting that their molecular safeguards may shift more quickly with age.
The findings do not prove that these DNA changes cause faster aging: the researchers measured methylation, not whether the sequences became more active or damaged DNA. Growth-related biological trade-offs and other processes may also contribute. The study found distinct age-related patterns in male dogs, pointing to partly different pathways linked to size and sex.
By revealing molecular patterns shared in some ways by dogs and humans, this work may help guide future studies of aging. Further research will be needed to determine whether these DNA changes can inform strategies for healthier aging across species.
