Why Do Huskies Have Blue Eyes?

Piercing blue eyes are just one of the characteristics that make Siberian huskies among the most prized dogs in the world. And now scientists believe they know why these animals have such hypnotizing stares.

The answer lies in the breed's genetic makeup: specifically, the canine chromosome 18, according to scientists at Cornell University College of Veterinary Medicine.

The study is believed to be the first genomic-wide association study on dogs using a consumer genetics service. In such an approach, markers in the genomes of many subjects (usually humans, but in this case animals) are scanned to pinpoint the genetic variations of a disease or a trait, such as blue eyes.

In recent years, personal DNA testing companies that promise to offer insight into our traits, ancestry and risk of disease have exploded in popularity. Last year, more people took consumer genetic genealogy tests than ever before—more than 12 million, according to industry estimates cited by MIT Technology Review.

Past research has revealed that two genetic factors cause blue eyes in merle and piebald dogs, which are due to mutations of a protein that can also produce a patchy fur coat. But this isn't the case for huskies.

The team analyzed the DNA of 6,070 purebred and mixed-breed dogs to get to the bottom of the Siberian husky's crystal-like eyes. Their owners also sent the researchers photos of the dogs and filled out web-based surveys on their pets. Of the total, 156 dogs had solid blue eyes or partially blue eyes.

By studying the canines, the researchers discovered what is known as a haplotype, or a set of genetic variants that are found on a chromosome.

The duplication of a variant of the homeobox gene, which plays a key role in how the eyes of mammals develop, appeared to be isolated to Siberian huskies and explained why their eyes were blue.

The duplication of the same gene might also explain why some Australian shepherd dogs have blue eyes, the authors believe.

The study, published in the journal PLOS Genetics, was a collaboration between Cornell University researchers and a dog DNA startup company called Embark, which funded the study.

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Aaron Sams, of Embark Veterinary Inc., told Newsweek: "The biggest surprise for me was that this duplication, which primarily explains blue eyes in huskies, can also explain blue eyes in a subset of Australian shepherds that are tri-colored (non-merle), which was until now unexplained."

He continued: "There is definitely more work to be done to fully understand eye color in dogs. For example, while dogs that carry a single copy of this mutation typically have completely or partially blue eyes, in rare cases a dog will carry this mutation but not have blue eyes, which means that other genetic or environmental factors are affecting the expression of this trait.

"In the future, this could give dog breeders control over the eye color of the litters they breed," said Sams.

The study is the latest to provide insight on the inner workings of our four-legged friends. Earlier this year, researchers at the University of Bari Aldo Moro in Italy concluded that dogs could understand human emotions based on facial expressions. If a dog detects a human is having a bad day, for example, its heart rate might rise, according to the study published in the journal Springer Learning & Behavior.