The duplication of chromosome 18, and its location in the DNA of the dog are the reasons that explain the existence of the blue color in dogs, especially the breed of siberian husky.

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The first contact we have with a person are their eyes. We can draw more attention or less, but when its color is clear we tend not to lose them of view. The majority of spaniards have brown eyes, therefore, when we see someone with blue eyes, we captured the moment.

The first manifestation of the blue color in the human being was in the europeans. His “appearance” could have been supported by a sexual selection due to an aesthetic preference for phenotypic variants rare. A decision that is acted on OCA2, a protein controlling the transport of melanin within the iris, causing a reduced synthesis of the same. In few words, that sexual selection may be the cause of the occurrence of the color blue in the eyes. However, this trait does not just appear in people. There are animals that also have the ability to hypnotize with their eyes.

as soon as you name the dog breed from the siberian Husky, it is inevitable to think in their fur white and their eyes are clear blue, a trait not so common in other breeds such as Border Collie or Welsh Corgi. To date, scientists believed that the feature that causes this color on the eyes is the same as that of the fur patched, due to the protein premelanosa, which can give one or two eyes of blue when there are regions desimpegmentadas. This was the cause that explained the existence of the blue in the eyes perrunos until now, but research in the USA has found another way to explain this trait, so distinctive.

First steps

Year: 2016. Place: laboratories Embark Inc. The scientists Adam Broyke and Aaron Sams, along with his team, created the first DNA test for dogs in research degree. With this, they get to collect traits, complete data for canine health and results of ancestry. But it was not a test either or obtained in the traditional way in the consultations. In this case, the internet and a database were the key: “Thousands of customers, with much taste, complemented by surveys on the internet for the scientists to have the opportunity to discover new genetic associations in the dogs”, explains Adam Broyke, one of the leaders of the study published in PLOS Genetics recently.

These researchers came to collect information from more than 6,000 dogs by means of surveys and by the publication of photos. Of them, nearly 3,000 have served as an object of study for these biologists. Their work has managed to position itself as the first study of the genomics of the consumer made in a model non-human: a study of blue eyes, based on thousands of dogs.

These huskies have heterecronomía, an abnormality which causes a blue eye and the other brown JAIME LESZCAK

“The examination of 3,000 dogs from the database has brought to light the existence of a duplication of chromosome 18,” explains Boyke. In his search for the source of the duplication, these scientists believed, in a principle, in the theory of the dose: “To date, the most familiar examples of duplications that affect the phenotype are dose-related. In these cases one or more duplication events increase the number of copies of the gene and, therefore, the amount of protein product translated available for cell function,” declare in the study.

chromosome 18 as the protagonist

dogs have a total of 39 pairs of chromosomes and its location is a decisive factor to explain why they are as they are, an important factor in the doubling of the chromosome and, therefore, the existence of blue eyes. On chromosome 18 are two of the crucial elements for this character: the gene CD82 and ALX4. The first is not associated to the determinant role of the color of eyes, but ALX4 yes. “This gene is strongly associated with the variation of the color blue, mainly in the siberian huskies”, says Boyke.

With all the genetic information collected and studied, the researchers gave the following explanation to the matter: “we propose that this large duplication in a regulatory region could cause blue eyes to increase the expression of the gene ALX4, which leads to a reduction of melanin in the iris”, explains Boyke.

“The high proportion of this trait in our analyses (53% of the dogs with blue eyes) suggests that the duplication, if it is causal, it is dominant in its effect on the DNA,” argue the scientists in the study. However, in 47% of dogs remaining longer dominates the duplication and, therefore, the colour brown comes in.

From a research to another

The genomic duplication as a justification of the blue color in the eyes only been able to validate, to date, in cases of canine: “it Would be interesting to see if there are similar mutations in the human; this is not one of the regions of the human genome that has been associated with the color of eyes above, so that it is not clear if this is a region of the genome that is overlooked or if the dogs actually have something unique. In addition, it would not be the first time that the dog as an object of study makes known genetic data of human,” says Boyke.

seeing that the canine studies may help to understand further the genetics of the human being, the Embark is not satisfied with having created the first study of genomics to the consumer in a model non-human. With the help of “citizen scientists” and studies based on the subject matter, this team of researchers is confident that the genetic, either animal or human, will give them more of a surprise.

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