How old is your dog in human years? New method better than 'multiply by
7'

Date:
July 2, 2020
Source:
Cell Press
Summary:
How old is your tail-wagging bundle of joy in human years? According
to the well-known ''rule of paw,'' one dog year is the equivalent
of 7 years. Now scientists say it's wrong. Dogs are much older
than we think, and researchers devised a more accurate formula to
calculate a dog's age based on the chemical changes in the DNA as
organisms grow old.



FULL STORY ==========================================================================
How old is your tail-wagging bundle of joy in human years? According
to the well-known "rule of paw," one dog year is the equivalent of 7
years. Now, in a study published July 2, in the journal Cell Systems, scientists say it's wrong.

Dogs are much older than we think, and researchers devised a more accurate formula to calculate a dog's age based on the chemical changes in the
DNA as organisms grow old.


==========================================================================
Dogs share the same environment as their owners and receive almost the
same standard of health care as humans, providing a unique opportunity
for scientists to understand aging across species. Like humans, dogs
follow similar developmental trajectories that lead them to grey and
become more susceptible to age-related diseases over time. However,
how they age on a molecular level is more complicated -- aging rapidly
at first and slowing down later in life.

"In terms of how physiologically mature a 1-year-old dog is, a 9-month-old
dog can have puppies. Right away, you know that if you do the math, you
don't just times seven," says senior author Trey Ideker (@TreyIdeker) of
the University of California, San Diego. "What's surprising is exactly how
old that one-year-old dog is -- it's like a 30-year old human." Human and
dog DNA, which codes who we are, doesn't change much throughout the course
of life, but chemical marks on the DNA, called methylation marks, do.

Ideker considers these marks like wrinkles in the genome. "I tend to
think of it very much like when you look at someone's face and guess
their age based on their wrinkles, gray hair, and other features," he
says. "These are just similar kinds of features on the molecular level."
The researchers studied 104 Labrador retrievers spanning from few-week-old puppies to 16-year-old dogs with the help of two canine experts, Danika Bannasch of the University of California, Davis, and Elaine Ostrander
of the National Institutes of Health. They compared the changes in the methylation pattern to humans.

The comparison revealed a new formula that better matches the canine-human
life stages: human age = 16 ln(dog age) + 31. Based on the new function,
an 8-week- old dog is approximately the age of a 9-month-old baby, both
being in the infant stage where puppies and babies develop teeth. The
average 12-year lifespan of Labrador retrievers also corresponds to the worldwide life expectancy of humans, 70 years.

"I like to take my dogs on runs, and so I'm a little bit more sympathetic
to the 6-year-old now," says Ideker, who realized that his dog is pushing
60 according to the new calculation.

In both species, they found that the age-driven methylation largely
happens in developmental genes that are hotly fired up to create body
plans in utero and regulating childhood development. By the time one
becomes an adult and stops growing, "you've largely shut off these
genes, but they're still smoldering," says Ideker. "If you look at the methylation marks on those developmental genes, they're still changing." Focusing on the smoldering developmental genes, the team developed a clock
that can measure age and physiological states across different species,
while other methylation-quantifying age-predicting methods only do well
in one species.

Ideker also noted that future investigation in different dog breeds with various lifespans could provide more insight into the new clock. The
clock may not only serve as a tool to understand cross-species aging
but also apply as clinical practice for veterinarians to take proactive
steps to treat animals.


========================================================================== Story Source: Materials provided by Cell_Press. Note: Content may be
edited for style and length.


========================================================================== Journal Reference:
1. Tina Wang, Jianzhu Ma, Andrew N. Hogan, Samson Fong, Katherine
Licon,
Brian Tsui, Jason F. Kreisberg, Peter D. Adams, Anne-Ruxandra
Carvunis, Danika L. Bannasch, Elaine A. Ostrander, Trey
Ideker. Quantitative Translation of Dog-to-Human Aging by
Conserved Remodeling of the DNA Methylome. Cell Systems, 2020;
DOI: 10.1016/j.cels.2020.06.006 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/07/200702113649.htm

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