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Epigenetics study updates the dog-to-human age formula with implications for cross-species comparison to help understand human aging processes

Epigenetics is the study of chemical features that attach to genes and affect their activity. Mammals share similar life stages, yet little was known about whether specific epigenetic changes linked to these life stages look the same for different animals. A new study, in part supported by NIA, used epigenetics to compare aging of dogs and humans. Such epigenetic changes may help researchers better understand human aging processes. Findings updated the previous “one dog year equal to seven human years” formula and were recently published in Cell Systems.

Woman walking with a dog down a bricked paved walkway through the woods.Researchers from the University of California (UC), San Diego, National Human Genome Research Institute (part of the National Institutes of Health), Sanford Burnham Prebys Medical Discovery Institute in San Diego, University of Pittsburgh School of Medicine, and UC Davis looked at DNA methylation — a common type of epigenetic change where methyl groups (small molecules) attach to and turn off or silence a particular gene. Methylation patterns change over time in a consistent way across humans, which some believe can be used as an epigenetic clock to predict age. To help understand whether the epigenetic clocks in other animals differ from humans, the researchers studied the lifespan methylation of both dogs and humans. Domesticated, or pet, dogs are animals similar in their environment, level of health care, and aging patterns to humans, providing a good model for comparison.

DNA Methylation data were collected from blood samples of 104 Labrador retrievers (puppies to 16 years of age) and compared to DNA methylation patterns of 320 humans (one to 103 years of age). Researchers found similar DNA methylation patterns between the dogs and humans, especially in the early and late life stages. Changes in DNA methylation across shared developmental genes were key to lining up dog and human DNA methylation patterns. Researchers used the analyzed patterns to relate the epigenetic clock of humans with dogs and created a new formula to calculate dog-to-human age. In this calculation, similar life stages matched to estimate an 8-week-old puppy as about the age of a 9-month-old baby, and a 12-year-old senior Labrador as about the age of a 70-year-old adult.

By comparing DNA methylation patterns, this study demonstrates the use of epigenetics to translate age and aging between species. Such translation may be a helpful tool for understanding aging and studying healthy aging interventions. Next steps include testing the formula with other dog breeds, and further exploring epigenetic changes in developmental genes as they relate to aging.

This research was supported in part by NIA grant P01AG031862.

Reference: Wang T, et al. Quantitative translation of dog-to-human aging by conserved remodeling of the DNA methylome. Cell Systems. 2020;11(2):176-185.e6. doi: 10.1016/j.cels.2020.06.006.