This genetic mutation has helped scientists track the evolution of domestic dogs

On appearances alone, it can be hard to believe that dogs like fluffy Pomeranians or lively Chihuahuas are truly descended from wolves. Corn new search both illuminates and solidifies this relationship, while providing a new explanation for why owners are even able to pick Teacup Poodles and Shortnose Shih Tzus out of the pack.

Domestic dogs have more sizes than any other species of mammal on Earth. This is the result of human preference and selective breeding – but this wide size range is basically possible due to a recently discovered genetic mutation. This mutation corresponds to a small body size and it appeared in wolves before they were domesticated.

This discovery was announced Wednesday in the journal Current Biology.

“I think most people don’t realize that dogs were only domesticated 20,000 years ago, which evolutionarily is just a tiny part of a tiny drop in the bucket. “said the lead author. Elaine OstranderChief and Distinguished Principal Investigator of the Cancer Genetics and Comparative Genomics Branch at the National Institutes of Health.

“Putting together ancient wolf and dog DNA is so exciting,” Ostrander said. “You can see all these variations running around a dog park and saying, ‘I know what your DNA looked like 50,000 years ago.'”

While humans have several hundred genes that regulate body size, domestic dogs have only 20 body size genes. The strongest is insulin-like growth factor 1 (IGF-1), which controls 15% of body size variation in dogs. For nearly a decade, Ostrander and his colleagues searched for a mutation linked to IGF-1 – a genetic signal they could find in canids, the group of mammals that includes wolves, coyotes and domestic dogs. .

It finally came to light once the team looked at the non-coding strand of the gene, or antisense. An analysis of 1,431 genomic sequences spanning 13 species of ancestral and modern canids revealed a variant, or gene mutation, within the antisense that interacts with the IGF-1 gene. It was “really the key that unlocked everything,” Ostrander said.

This mutation creates a point of variation, resulting in what the team describes as either a small allele or a large allele. Alleles are alternate forms of genes that arise through mutation and are found in the same place on a chromosome. Subsequently, this mutation may explain the differences in body size between ancient and modern canids.

These alleles have conferred “morphological plasticity” on modern dogs; because both alleles circulate within the global dog population, people can selectively breed dogs of vastly different sizes. For example, there are three sizes of schnauzers: toy, miniature, and standard. The toy and miniature schnauzers analyzed in the study contained the small allele, while the giant schnauzers contained the large allele.

An analysis of ancient canids also revealed that the large allele was more often found in wolves extracted from northern latitude sites, while the small allele was more frequently identified in wolves extracted from southern latitude sites – primarily from the region. Mediterranean. This dovetails with a concept known as Bergmann’s Rule, which, simplified, states that being tall is more beneficial if one lives in a northern climate.

The study suggests that this large allele most likely appeared in wolves over 53,000 years ago, possibly due to natural selection. These wolves lived during the Pleistocene, also known as ‘tthe Ice Age.” Lower temperatures likely made this allele a fixed feature of northern wolves, while the small allele persisted in wolves living in warmer southern regions.

This makes the small allele the ancestral allele – a trait that derives from the common ancestor of canids. However, “what it was doing before 53,000 years ago, we have no idea,” Ostrander said. “We don’t know why nature maintained it.”

These findings could bring pet owners one step closer to understanding man’s best friend, but the primary goal of the study is to improve human health. All 25 genes linked to body size in domestic dogs are found in humans, and these genes may be responsible for diseases like cancer.

“We’re looking at where the mutations are, what’s tolerated and what’s not tolerated, and what’s going on around it,” Ostrander said. “Then we look at human mutations and we can start to piece together a story about which parts of the gene are critical and which parts are responsible for poor health.”

Bette C. Alvarado