Epigenetics Underlies Comparatively Accelerated Molecular Aging in Larger and Male Dogs

Domestic dogs offer a useful model for understanding the biology of aging because their lifespans vary dramatically with body size. Large dogs tend to be shorter lived than their smaller counterparts, but why? Headed by a team at Arizona State University, a study of nearly 900 dogs now suggests that the answer may be written into the animals’ epigenomes.

Research professor Noah Snyder-Mackler, PhD, at Arizona State University School of Life Sciences, and colleagues developed an epigenetic clock that predicted mortality in dogs and showed that epigenetic aging is fastest early in life. The study results indicated that male dogs and larger dogs undergo accelerated molecular aging, with male dogs exhibiting pronounced DNA methylation (DNAm) changes on the X chromosome, and larger animals exhibiting methylation changes at transposable elements (TEs), stretches of DNA that can influence genome stability and gene regulation.

Snyder-Mackler is senior and corresponding author of the researchers’ published paper in Science (“Epigenetic aging and transposon dysregulation reflect size-related lifespan compression in dogs,”) in which they concluded, “Our findings broadly establish companion dogs as a translational model for uncovering molecular mechanisms of lifespan variation, epigenomic instability, and age-related disease.”

Aging is a universal process, but its pace and biological mechanisms substantially differ between individuals within even the same species, the authors wrote. “Whether shorter-lived individuals simply die earlier or instead experience accelerated biological aging throughout life remains unclear,” they noted. And while comparative studies across species have identified mechanisms associated with exceptional longevity, they may not be as well suited to identifying the molecular drivers of aging variation. “Domestic dogs provide a model for addressing this challenge because body size strongly predicts lifespan, with larger breeds living substantially shorter lives than smaller breeds despite sharing many physiological and environmental conditions,” the team continued.

In fact, smaller breeds can live nearly twice as long as larger breeds. And companion dogs live in human environments, consume commercial diets, and receive routine medical care, making them a relevant translational model for studying how genetic background and environmental exposures shape aging, the investigators pointed out.

But how intrinsic factors such as size and biological sex influence variation in dog aging and lifespan remains unclear. “It is well established that size and sex influence lifespan in dogs, but it remains unclear whether shorter-lived dogs experience accelerated epigenetic aging,” they stated. Previous research has demonstrated that DNAm is a useful indicator of biological aging, with “epigenetic clocks” offering a way to understand the factors that accelerate or decelerate biological aging. “DNA methylation (DNAm) has emerged as a robust molecular biomarker of age, with ‘epigenetic clocks’ offering a quantitative framework for identifying factors that accelerate or decelerate biological age.”

For their newly reported study Snyder-Mackler, together with first author Blaise Mariner, PhD, and colleagues generated 1,640 methylomes from a cohort of 894 dogs in the Dog Aging Project. They combined the molecular data with detailed genetic and demographic data. The results indicated that molecular aging occurs most rapidly early in a dog’s life. The study also found that larger and male dogs—both of which have shorter lifespans than their respective counterparts—age more quickly at the molecular level.

The authors identified different epigenetic patterns underlying these effects. According to the findings, sex-related changes were concentrated on the X chromosome, while body-size-related changes were especially prominent in TEs. “Thus, size and sex, two axes associated with shorter expected lifespan in dogs, appear to shape aging through partially distinct epigenetic architectures,” they stated. “Larger dogs show greater methylation loss at TEs with age, consistent with increased immune remodeling and genomic instability … These data address a major gap in comparative epigenomics by providing evidence that, within a species, demographic groups with shorter expected lifespans show faster epigenetic aging.”

The post Epigenetics Underlies Comparatively Accelerated Molecular Aging in Larger and Male Dogs appeared first on GEN - Genetic Engineering and Biotechnology News.