We’re pleased to announce the addition of a new coat color trait test for red pigment intensity to the Embark for Breeders product. Red pigment intensity is the concentration of red pigment (pheomelanin) in a dog’s hair, which produces colors ranging from light cream (like a West Highland Terrier) to deep red (like an Irish Setter).
About the Red Pigment Intensity Test
Intensity is not controlled by a single “I locus”; rather, it is a phenotype controlled by at least five genetic loci, although some are more impactful than others in specific breeds. Embark is the only test to look at markers at all five known intensity loci and is able to explain over 70% of the variation in the phenotype with these markers. We report dogs’ overall phenotypic expectation as well as their genotype results at each locus we test for (to see your dog’s results for red pigment intensity: click on “See Details” and then “Show Subloci Results” at the bottom of the page). If your dog was tested with an Embark for Breeders or Breed + Health kit (no matter which microarray version they were tested with), your dog’s trait results will be updated with their genotype. Please note that it may take a few weeks for the result to appear in all profiles. Because this is a complex genetic trait, more research in the future may lead to changes in the test to incorporate more variants or loci as they are discovered.
As part of our test, we obtain dogs’ genotypes for two intensity variants that were discovered by other research groups: the MFSD12 missense variant described in this publication, and the chromosome 15 copy number variant near the KITLG gene described in this publication. The MFSD12 test is a direct variant test, meaning that we obtain dogs’ genotypes at the causal missense variant, while the KITLG test is a linkage-based test. The causal variants for the other three loci are not yet known, but the tested markers are significantly associated with the trait. A peer-reviewed paper authored by members of Embark’s Discovery Team provides additional detail on exactly what genetic variants are used for the three novel associated regions we use in our test, and the full text will be publicly available (for free) once it is published.
We recognize that the KITLG variant reported by Weich et al. is most predictive in Poodles and Nova Scotia Duck Tolling Retrievers and doesn’t substantially impact coat color in the other breeds assessed in that study. However, Embark does report dogs’ genotypes at this locus as part of our commitment to provide customers with the most information available through our testing services (we perform the same trait tests on all dogs regardless of their breed). The mathematical model that we use to predict a dog’s intensity phenotype from its genotypes at the five loci we use for our test takes into account that some loci have a stronger impact on phenotype than others.
Red Pigment Intensity and Other Coat Color Loci
The Intensity results that we report impact pheomelanin (red pigment) and not eumelanin (black or brown pigment). Because the genetic basis of red pigment intensity is still not fully understood, our phenotype predictions may not always be correct – we can only provide the best prediction we can make using what is currently known.
When reviewing a result for a dog, the predicted phenotype, which is listed on the right-hand side of the top of the results, takes into account the dog’s genotype at the E, K, and A loci. For example, a dog would need to be ee, or kyky and express ay, aw, or at to have pheomelanin in their coat. While there is some evidence that the D locus may affect pheomelanin to some extent/in a breed-specific manner, in our research, we did not see a significant effect on coat pheomelanin intensity from the B or D locus.
How Can I Use This Test for Breeding?
A quick disclaimer: we do not recommend making breeding decisions solely based on coat color because – as many breeders know – doing this repeatedly can cause a rapid loss of genetic diversity in a line, which can lead to a higher prevalence of health problems. However, if, for example, you wanted to get puppies with deep red coats, the best way to increase the likelihood that your litter would have darker coats on average would be to breed two dogs that got overall results of “Any light hair likely apricot or red”.
Note: This trait is non-Mendelian, meaning that it doesn’t behave according to Mendel’s laws. As a result, predicting the percentage of puppies in a litter that will have low, intermediate, or high intensity is much more complicated and error-prone than it is for a trait like K locus, where a single gene determines the phenotype. We also can’t confidently say (for now) whether specific alleles or allele combinations are dominant/recessive to others. Consequently, we cannot make any guarantees that specific breedings will produce the desired results.
Research regarding Intensity is ongoing, and we appreciate you informing us of your dog’s predicted coat color was incorrect. We will use this information to improve our test in the future.
A big thanks to J. Caplan, Vicky Creamer, Jill Miller, Alisa Wold, S. Sengupta, and Anna Kennedy for lending their beautiful dogs’ images to illustrate the Intensity spectrum.