Roan Coat Color in the American Quarter Horse: Tested, Validated & Published | Welcome to Roan

Team Etalon has released a peer-reviewed research publication in which genetic markers identified are found in American Quarter Horses with the Roan coat color pattern.

Testing for Roan 1 (RN1) and Roan 2 (RN2) roan coat color genetic markers are now available and included in the Pro Package 2.0 and Pro + Ancestry Bundle 2.0.

Roan is a coat color pattern in horses often characterized by an even mixture of white hairs interspersed throughout the base coat color and can even appear more white than base colored hair but still evenly spread out over the body. The horse's head, lower legs, mane, and tail usually remain the solid or darker base coat color. This gives the horse a unique "frosted" or "ticked" appearance. Roan is reported to be caused by a dominant allele of the RN gene.

History of Roan Genetic Testing in Horses

So what’s the back story with testing for Roan?

Imagine you have a favorite roan mare that you’d love to breed, not only because she’s talented with a great mind, but because you can’t stop looking at her beautiful coat. You can see that she’s a roan, but you’re not sure if she’ll reproduce that same look or if you’ll need to increase your chances by also choosing a roan stallion. Now, being a responsible breeder, you go and order a genetic test, and the results are stunning…but not in a good way: Her test results say she’s negative for Roan. In other words, the lab report says she is not a roan. Whut??!

Don’t stress, you’re not alone. It’s estimated that up to 30% of these prior tests may have ended in this interesting scenario. Read on, dear horse person, to understand why.

Here’s what might have happened and why:

It’s not commonly known, but there are possibly multiple alleles for roan much as there are many variants and alleles for other white markings (Splashed White 1, Tobiano, Lethal White Overo, etc.) In the scenario described above, the mare with the obvious roan phenotype, simply has a type of roan that is not the same as in the test or marker ordered by the owner. Because there is limited information out there, and the testing is limited by either technology, validation or range, the client may have a hard time understanding “your mare is negative for that type of roan only”, however she is possibly positive for another type.

Fun Fact #1:

There may be multiple "roan alleles" in horses, not just one, but this complexity is rarely discussed in the horse community.

Fun Fact #2:

To date, only one Roan marker haplotype (RN1) has been published, originally found in Noriker horses. Grilz-Seger et al 2020.

Fun Fact #3:

The Roan 2 (RN2) marker, believed most common in the American Quarter Horse, has never been published or validated—what was tested for remains unknown; Etalon’s research and peer-reviewed publication confirms a known and validated marker.

Fun Fact #4:

Through collaboration with the horse community, Team Etalon has identified, validated, and published key information on Roan genetic markers—reaffirming RN1 and fully revealing and publishing RN2.

Funest Fact #5:

Additional Roan markers are in development—stay tuned for Roan 3 (RN3), coming soon to a stable near you!

What is a genetic “marker” or “correlation” versus a “causative” variant?

As you may have heard, the genetic code for any mammal is pretty big and complicated. Not only do you have several gigabytes worth of base pairs (combinations of A, C, T, and G) but they code for many things from functional body parts, to eye color, brain function, speed, size and so on. They also code for things like disease, disorders, predisposition to disease/disorder, resistance and susceptibility. To add to this madness we also have genetic mutations and epigenetic or methylation changes over time. This makes finding a “gene” for something much more complex than many may think, so, for the purposes of this blog, we’ll keep it on a very simplified level:

Understanding Correlative Genetics in Horses

A "correlative" refers to a genetic marker or piece of code associated with a specific condition or trait, but not directly causing it.

Example #1: Larger Horses and Roaring (Recurrent Laryngeal Nerve Damage)

Larger horses statistically have a higher incidence of roaring (laryngeal paralysis) according to several research studies. This increased risk is correlated with a specific variant in the LCORL gene, which is also associated with greater height/size. While this variant is linked to a 12-fold increase in roaring risk, it does not directly cause the condition—it is a genetic correlation.

Example #2: SCID and Arabian Horses (Severe Combined Immunodeficiency)

Horses carrying the genetic variant for Severe Combined Immunodeficiency (SCID) are predominantly Arabian horses. This variant is correlated with the breed, or “being Arabian” but actually causes the deadly immune system disorder—SCID. This genetic link helps identify carriers within certain horse breeds.

Example #3: Non-Gene Example—Yellow Buses and Flat Tires

Just like yellow buses are associated with flat tires after running over nails, a physical trait (yellow bus color) is correlated with an outcome (flat tire). The color does not cause the flat tires, but the association illustrates a correlation.

OK, so what happens now ?

More research! We need to keep digging into the genetic code of the horse to see if all of these Roan alleles (or “markers”) will lead us to the actual cause(s) of the roan change in horse coat color.

Breeds with Observed Roan Coat Color

Roan can be found in various horse breeds, including:

• Quarter Horses
• Appaloosas
• Belgian Draft Horses
• Gypsies
• Noriker Horses
• Tennessee Walking Horses
• Percherons
• Warmbloods
• Welsh Cobs

History of Roan in Horses

Documentation of roan coat color in horses has existed for centuries, though precise dating is difficult. Breeding experience, pedigree analysis and modern genetic understanding has clarified the inheritance patterns and the genes involved more recently, but there is still some work to be done.

Famous Roan Quarter Horses

• All Spice
• Hashtags
• Call Me Mitch
• Third Edge
• Metallic Cat
• Royal Blue Boon
• Leo Hancock Roan
• Red Man
• Many more notable ranch horses and rodeo performers!

Scientific Understanding of Roan to Date

The roan pattern in horses is thought to be caused by a dominant allele of the RN gene likely located on or near the gene KIT, which codes for a protein involved in melanocyte migration and distribution. Because the gene is thought to be dominant, only one copy of RN needs to be present to cause roaning. Therefore, both homozygous (RN/RN) and heterozygous (RN/n) horses will display the roan pattern, while homozygous recessive or negative (n/n) horses will not.

What we know

The size of the gene and the changes happening to create the roan coat color along with the current studies in tested horses, lead us to believe that a horse can only have a maximum of 2 copies of Roan at any one time. For example, a horse can be RN1/n, RN1/RN1, or RN2/n, RN2/RN2, and even RN1/RN2, but never RN1/RN1 + RN2 and so forth.

What we think we know (but still need to see if future evidence proves it)

Given the size and location of the genes involved, we believe that Roan and Tobiano can also only occur in sums of two. For example, we believe that a horse can be TO/RN1, TO/RN2, or TO/TO, but not TO/TO +RN1 or RN2.

Why we are not really sure

Prior lore in the horse community surrounding genetic inheritance of coat color variants in the KIT gene included the belief that any one horse could only have a total of 2 copies of such a gene at any one time (and this included Tobiano). For example, it was thought that a horse could have W20/W20 or TO/W20, but never TO/TO + W20…thanks to recombination events in the mammalian genome, this turned out to be a false assumption. A horse CAN, in fact, have more than 2 variants/mutations in the KIT gene, and we’ve seen as many as 6! (McFadden et al 2024)

Roan in Other Animals

Roan patterns are also observed in other animals, though the genetic mechanisms and underlying causes may differ.

Cattle:

Roan is a recognized coat color in several cattle breeds, often resulting from a heterozygous state where red and white hairs mix.

Dogs:

While not precisely the same as horse roan, ticking or roaning can be seen in some dog breeds, such as Australian Cattle Dogs. These patterns involve mixtures of pigmented and white hairs.

Coming soon: Roan #3…stay tuned!