Siberian huskies are very different from golden retrievers or miniature schnauzers. They obviously share a common ancestor ( dogs split from wolves about 40,000 years ago ), but Huskies, with their hunting and sled-shooting skills, are fascinating to us. However, it is possible that what differentiates these Arctic dogs the most from their companions is the color of their eyes, pale blue. Now science unravels its mystery.
Scientists from Cornell University and dog DNA testing company Embark Veterinary, Inc. recently teamed up to find out why Siberian huskies have blue eyes. In a study published in the journal PLOS Genetics , experts reveal that it is most likely a DNA molecule called canine chromosome 18.
The team determined that there is a very strong association between a tandem duplication (identical adjacent chromosome segments) on canine chromosome 18, which is located near the ALX4 gene.
“We think it is an important functional candidate because it is close to the ALX4 gene, which other researchers have shown plays a key role in mammalian eye development and pigmentation,” said Embark lead scientist Aaron J. Sams. “ Our hypothesis, which still needs to be tested, is that this duplication can alter the expression of ALX4, which can lead to the repression of the genes involved in ocular pigmentation “, clarifies the expert.
This study, the first consumer genomic study conducted on a non-human animal, examined genetic data from 6,070 dogs owned by Embark customers. While some genetic variants are known to lead to blue eyes in species such as the Dalmatian or Australian Shepherd – which sometimes have blue or blue and brown eyes – those variants are related to the coloration of dogs. For example, dogs with a mottled spot pattern of color or a pale pattern (a mostly white dog with colored spots) often contain these genetic variants. However, these variants have not been enough to explain why Australian tri-colored sheepdogs and Siberian Huskies also have blue eyes.
“It turns out that [tri-colored Australian Shepherds and Siberian huskies] carry the duplication we’ve identified,” explains Sams. “ So it was a fun mystery to solve!”
Specifically, they discovered that a duplication of 98.6 kilobases on chromosome 18 near the ALX4 gene was closely linked to the variation in the color of the blue eye, mainly in Siberian Huskies, but also in the Australian Shepherds that we have mentioned.
One copy of the variant was sufficient to cause blue eyes or heterochromia (blue and brown eyes), although some dogs with the variant did not have blue eyes, so other genetic or environmental factors must be involved – and not discovered.
Future studies on the functional mechanism underlying this association may lead to the discovery of a new pathway by which blue eyes develop in mammals. From a broader perspective, the results underscore the power of consumer data-driven discovery in non-human species, especially dogs, where there is intense interest from owners in their pets’ personal genomic information.
“This study demonstrates the power of the approach Embark is taking to improve canine health. In a single year, we gathered enough data to conduct the largest canine study of its kind. Embark is currently conducting similar research projects on a variety of morphological and health-related characteristics, and we look forward to continuing to use our platform to advance canine genetics and health in a very real way, “concludes Sams.
Reference: Direct-to-consumer DNA testing of 6,000 dogs reveals 98.6-kb duplication associated with blue eyes and heterochromia in Siberian Huskies. Petra E. Deane-Coe, Erin T. Chu, Andrea Slavney, Adam R. Boyko, Aaron J. Sams Plos Genetics. DOI: https://doi.org/10.1371/journal.pgen.1007648
