'Why huskies have blue eyes decoded'

DNA testing of over 6,000 dogs has revealed that a duplication on canine chromosome 18 is strongly associated with blue eyes in Siberian Huskies, scientists say.

The research, published in the journal PLOS Genetics, is the first ever consumer genomics study conducted in a non-human model and the largest canine genome-wide association study to date.

Although two genetic variants are known to underlie blue eye colour in some dogs, these do not explain the trait in some other dogs, like Siberian Huskies, said researchers at Embark Veterinary, a dog DNA startup company in the US.

The researchers used a diverse panel of 6,070 genetically tested dogs with owners that contributed phenotype data via web-based surveys and photo uploads.

They found that a duplication on chromosome 18 near the ALX4 gene, which plays an important role in mammalian eye development, was strongly associated with variation in blue eye colour, primarily in Siberian Huskies but also in non-merle Australian Shepherds.

One copy of the variant was enough 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 are still involved, researchers said.

"Using genetic data from the pets of our customers, combined with eye colours reported by customers for those same animals, we have discovered a genetic duplication that is strongly associated with blue eye colour," said Aaron Sams from Embark Veterinary.

Future studies of the functional mechanism underlying this association may lead to the discovery of a novel pathway by which blue eyes develop in mammals, he said.