Updated Phenotypical and Genetic Assumptions for Roan Horses

Phenotype Definition

The roan phenotype is defined as a solid-colored coat interspersed with white hairs across the body, hips, chest, and upper legs, with few or no white hairs on the head and lower legs. This description aligns with ARHA’s current standards and remains validated by recent genomic studies.

Inheritance and Expression

• Roan is inherited as a dominant trait located in the KIT gene region. • It is epistatic to base coat color loci (ASIP and MC1R), meaning it modifies but does not replace bay, red, or black coats. • Cream, pearl, champagne, dun and gray may obscure roan expression but do not alter its genetic presence. Homozygous roan horses are viable; multiple RN1/RN1, RN2/RN2, RN1/RN2, RN1/RN3, RN2/RN3, RN3/RN3 individuals have been documented with no evidence of lethality.

Genetic Variants (Haplotypes)

• RN1: An older haplotype identified across many breeds including Quarter Horses, Paint Horses, Mustangs, Gypsy Vanners, Welsh Ponies, Mangalarga Marchadors, Percherons, Belgian Drafts, Missouri Fox Trotters, and Curly Horses. In the Quarter Horse, it traces back to the Burnett roan mare (1901) and the stallion Red Man (1935). • RN2: A more recent haplotype primarily found in North American breeds (Quarter Horses, Paint Horses, Mustangs, Curly Horses). It traces back to the Burns roan mare (1901) and Orals Kitten (1935), and has been widely propagated by sires such as Peptoboonsmal and Metallic Cat. • RN3: Newly discovered in Quarter Horses, Paint Horses, and Mustangs. It is strongly linked to the “Kitch Roan mare” (1901) and modern sires such as Zippos Mr Good Bar. • Collectively, RN1, RN2, and RN3 account for ~90–95% of roan phenotypes in Quarter Horses and Paint Horses, and 70–80% of roan phenotypes across multiple breeds.

Health & Viability

• No adverse health effects have been associated with any roan haplotypes. • Unlike earlier speculation, roan is not lethal in the homozygous state, supported by the presence of homozygous RN1 and RN2 horses.

Research Status

• Current haplotypes (RN1, RN2, RN3) are strongly associated markers, though no causative mutation has yet been identified. • Additional, rare haplotypes are expected, similar to the multiple independent origins observed in Dominant White. • Genomic testing now identifies ~90% of roan horses, a major improvement over earlier estimates of ~70%.

References

• Everts, R.E., Caron, R., Foster, G., McLoone, K., Martin, K., Brooks, S.A., & Lafayette, C. (2025). Identification of Two Genetic Haplotypes Associated with the Roan Coat Color in the American Quarter Horse and Other Equine Breeds. Animals, 15(12), 1705. https://doi.org/10.3390/ani15121705 • Everts, R.E., Caron, R., Foster, G., McLoone, K., Simiele, L., Martin, K., Brooks, S.A., & Lafayette, C. (2025). Identification of a Novel Haplotype Associated with Roan Coat Color in American Quarter Horses. Animals, 15(16), 2386. https://doi.org/10.3390/ani15162386

Implications for ARHA Registration/Membership:

• ARHA’s visual description of the roan phenotype is accurate. • The association should update genetic assumptions to reflect that: • Roan is dominant, non-lethal, and reliably testable. • At least three KIT-region haplotypes (RN1*, RN2, RN3) are validated and traceable in Quarter Horse and Paint pedigrees. • *RN1 Found in a variety of breeds including QH, Paint, Norikers, Gypsy Vanners, Mustangs, Tennessee Walkers and more! • Genetic testing now offers breeders a scientifically supported way to confirm roan status, especially valuable where phenotype may be obscured by dilution or gray.

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