You wouldn’t be the first person to be mesmerized by the piercing blue eyes of a Siberian Husky. While the breed standard indicates that the breed may have brown or blue eyes, one of each, or even parti-colored, perhaps it’s the “eyeliner” of pigment that makes the blue ones on this breed really stand out. From a scientific standpoint, now we know why.
The DNA of more than 6,070 dogs was studied by scientists at the Cornell University College of Veterinary Medicine through Embark Veterinary, Inc. DNA test kits purchased by their owners only too willing to participate.
Of those 6,070 dogs, 156 of them had solid blue or partially blue eyes, and by studying these dogs, researchers found a set of genetic variants known as a haplotype. 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 explains why their eyes are blue but they can still have dark coats.
Researchers found that a genetic mutation near a gene known as ALX4 on canine chromosome 18 is strongly associated with blue eyes in the breed. This mutation of the ALX4 gene in Sibes seems to result in decreased pigment production in the eye, and the lack of pigment causes the eye to appear blue. Put another way, there isn’t any blue pigment, its just the way the light enters and exits the eye that creates the appearance of blue much in the same way the sky looks blue, but outer space isn’t blue.
From past research, it was known that two genetic factors cause blue eyes in merle and piebald dogs – mutations of a protein that can also produce a patchy fur coat. This isn’t the case for Siberian Huskies. It’s why Siberian Huskies are among the only breeds that can have blue eyes completely independent of the merle gene. It’s also thought that a duplication of the same gene might be why some Australian shepherd dogs also have blue eyes.
The results were published in a paper accepted for publication in the journal PLOS Genetics.
Image: Siberian Husky/Deposit Photo