Horses have provided an animal model for studying genetic mechanisms behind some important traits in humans, but it remains unclear which genes are responsible for the grey coat color and the concurrent increased melanoma risk observed in this species. Through implication of the type and expression level of genes related to coat color, this work offer insights into the relationship between gene expression, coat color and health outcomes, provide a better understanding of those traits in equids and may enable a more efficient management of those traits in equine populations.
The Genetics of Greying
The grey horse is known for its spectacular change in coat color from their original hue to a dazzling white. But researchers have since found that this under pigment development is associated with an increased number of copies of a particular DNA sequence in the Syntaxin 17 gene.
Horses with two copies of this duplicated sequence (the G2 variant) were found to grey more slowly, and those with three copies (the G3 variant) turned white much faster. This striking dosage effect underscores the dramatic ability of genetic variations to literally sculpt the appearance of these magnificent beast.
Grey Mutation Aids Risk for Melanoma
However, unlike the more commonly recognized connections between gene variants and coat colors in the animal kingdom, this piece of genetic information has far deeper implications than just hair color. In addition, the G3 variant possessing a higher syntaxin 17 expression had more than double the risk of developing melanoma compared to grey horses that did not carry this variant.
On white horses that carry the Grey mutation, these skin tumours can appear and vary from benign forms to malignant ones. Horses with the Grey mutation are also different from one another as individuals; for example, some horses with the Grey mutation develop melanoma while others do not and all of these horses have black skin, regardless of their coat color (so that sun exposure cannot explain this difference).
There is a significant impact on welfare to the findings of skin cancer in horses, because it will informs veterinarians and horse owners that they have an opportunity for early detection and management which is extremely time sensitive. This strategy would enable horse owners and breeders to identify those high-risk individuals with the genetic test described in this study and be extra vigilant on such horses, as they might suffer from insulin sensitivity.
Conclusion
Although we have only pinpointed those genetic variants today, this is an important discovery related to hair greying and melanoma risk in the horse and allows us to better understand these complex traits. However, this not only gives new and important information about the complex systems underlying fur colour and skin health in these animals but also opens up a path to developing diagnostic tools and possibly even therapies to improve animal welfare. These advances have made a significant impact on the field of equine genetics and when researchers finally uncover some of these truths related to the Grey mutation it will drive even more exciting advancements.
