Gene mutation that makes dogs small existed in ancient wolves

Date:
January 27, 2022
Source:
Cell Press
Summary:
Popular belief has been that small dogs, such as Pomeranians and
Chihuahuas, exist because once dogs were domesticated, humans wanted
small, cute companions. But researchers now identify a genetic
mutation in a growth hormone-regulating gene that corresponds to
small body size in dogs that was present in wolves over 50,000
years ago, long before domestication.



FULL STORY ========================================================================== Popular belief has been that small dogs, such as Pomeranians and
Chihuahuas, exist because once dogs were domesticated, humans wanted
small, cute companions. But in the journal Current Biology on January
27, researchers at the National Institutes of Health (NIH) identify a
genetic mutation in a growth hormone-regulating gene that corresponds to
small body size in dogs that was present in wolves over 50,000 years ago,
long before domestication.


==========================================================================
The search for this mutation had been ongoing at the NIH for over
a decade, but researchers didn't find it until Jocelyn Plassais (@JocelynPlassais), a postdoc in geneticist Elaine Ostrander's lab,
suggested that they search for sequences around the gene that were
positioned backwards and confirm if any were present in other canids and ancient DNA. With this approach, their team found a reverse form of the insulin-like growth factor 1 (IGF1) gene with variants that correlated
to dog body size. "We looked at 200 breeds, and it held up beautifully,"
says Ostrander.

The researchers then collaborated with evolutionary biologists Greger
Larson (@Greger_Larson) at Oxford University and Laurent Franz at Ludwig Maximilian University to look through ancient wolf DNA to see when the
IGF-1 mutation first showed up. Scientists have theorized that dogs
started out large and became smaller about 20,000 years ago, when they
were domesticated, but this discovery presents the possibility of a new evolutionary narrative.

Indeed, when the team looked at the DNA of a 54,000-year-old Siberian
wolf (Canis lupus campestris) they found that it, too, possessed the
growth hormone mutation. "It's as though Nature had kept it tucked in
her back pocket for tens of thousands of years until it was needed,"
says Ostrander.

The finding holds not just for dogs and wolves, but also for coyotes,
jackals, African hunting dogs, and other members of the family of
animals referred to as canids. "This is tying together so much about
canine domestication and body size, and the things that we think are
very modern are actually very ancient," says Ostrander.

Ostrander and her team plan to continue to investigate the genes that
regulate body size in dogs. "One of the things that is pretty cool about
dogs is that because they have evolved so recently there aren't actually
a lot of body size genes," she says. Canids have only 25 known genes that regulate body size, compared to several hundred in humans. "I really want
to understand the whole continuum -- from Chihuahuas to Great Danes,"
says Ostrander.

This work was supported by funding from the Intramural Program of the
National Human Genome Research Institute.

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


========================================================================== Journal Reference:
1. Plassais et al. Natural and human-driven selection of a single
non-coding
body size variant in ancient and modern canids. Current Biology,
2022 DOI: 10.1016/j.cub.2021.12.036 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2022/01/220127114340.htm

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