Authors: McFadden Aiden, Vierra Micaela, Robilliard Holly, Martin Katie, Brooks Samantha A, Everts Robin E, Lafayette Christa
Journal: Animals : an open access journal from MDPI
Summary
# Editorial Summary Coat colour genetics in horses is considerably more complex than the traditional two-allele model commonly assumed by breeders and breed societies, as demonstrated by McFadden and colleagues' 2024 analysis of 161 horses carrying compound KIT genotypes. Using phased next-generation sequencing data, the researchers identified 15 haplotypes containing two or more of the 35 known KIT variants associated with depigmentation and white spotting, then systematically photographed and scored depigmentation in horses with three or more KIT variants across 12 unique compound genotypes. Significantly, seven of these multi-variant haplotypes produced substantially greater white markings compared to single-variant carriers, suggesting an additive or synergistic effect of multiple depigmentation alleles that isn't currently captured in breed registration standards. For equine professionals involved in breeding decisions, veterinary genetics counselling, and breed administration, this research underscores the need to move beyond simplistic coat colour prediction models—multi-variant KIT combinations are relatively common and produce phenotypes that may not align with traditional breed criteria or inherited health considerations. Further characterisation of how specific compound genotypes manifest phenotypically will be essential for informed breeding practices and accurate communication with horse owners about expected appearance and potential welfare implications.
Read the full abstract on PubMed
Practical Takeaways
- •Breeders and breed registries should understand that the common belief that horses have only two KIT variants is incorrect, which may affect coat color prediction and breed registration decisions
- •White marking expression is more complex than traditional two-allele models suggest; horses with multiple KIT variants show significantly different depigmentation patterns that could influence breed selection
- •Genetic testing should account for compound KIT genotypes when advising clients on coat color inheritance and breed eligibility expectations
Key Findings
- •Horses can possess more than two KIT variants, with 15 haplotypes identified containing two or more KIT variants associated with depigmentation
- •7 of 12 multi-variant haplotypes resulted in significantly greater depigmentation compared to single-variant haplotypes (ANOVA, p<0.05)
- •35 KIT alleles are known to be associated with or cause depigmentation and white spotting in domestic horses
- •Compound genotypes with three or more KIT variants show variable phenotypic expression of white coat patterns