This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: Across mammals, larger species typically have longer lifespans, ranging from only a couple of years for mice to almost 200 years for some whales. However, when we look within species, we often see the opposite—smaller individuals outliving larger individuals.
Dog lovers and owners have long experienced this exception, as larger dog breeds tend to grow faster and die younger than smaller dogs. Scientists have been working to understand the underlying causes of these so-called "dog years" that can shorten dogs' time with their human companions. "Dogs provide an extraordinary model for understanding aging because they show dramatic variation in lifespan within a single species," said senior study author Noah Snyder-Mackler, a professor at Arizona State University's School of Life Sciences and Center for Evolution and Medicine.
Not only do big dogs die younger, but they are also more susceptible to many age-related diseases. And what scientists can learn about dog aging can provide an important window into human aging, too. "Because they are companion animals, they can also be a powerful model with immediate relevance to human health.
Living with us means that we share experiences and environments, while our love for our pets means we provide them food, exercise and lifelong health care—meaning we can translate many findings in our shorter-lived pets to humans," said Snyder-Mackler. A new study led by researchers at Arizona State University offers the first compelling molecular explanation of why large dogs live shorter lives: The answer may lie in how hallmarks of aging reshape dog DNA. The study is published in Science.
Drawing on data from 864 dogs enrolled in the Dog Aging Project, a team of scientists mapped genome-wide patterns of DNA methylation. DNA methylation is part of the epigenome, which influences how much genes are turned on or off without changing the sequence of DNA in each gene. The epigenome is also responsive to environmental cues, such as diet or stress, and, crucial to this work, DNA methylation is a well-established chemical signpost of aging and DNA regulation.
Their findings reveal that aging is associated with the widespread loss of these regulatory marks over time, particularly in regions of the genome known as "jumping genes" or transposable elements. A class of these jumping genes called LINE1s was found to be a key component of biological aging differences. The LINE1s can copy and insert themselves throughout the genome, jumping from chromosome to chromosome and damaging DNA in the process.
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