5'UTR Variant in KIT Associated With White Spotting in Horses.
Authors: McFadden Aiden, Martin Katie, Foster Gabriel, Vierra Micaela, Lundquist Erica W, Everts Robin E, Martin Erik, Volz Erin, McLoone Kaitlyn, Brooks Samantha A, Lafayette Christa
Journal: Journal of equine veterinary science
Summary
# Editorial Summary: 5'UTR Variant in KIT Associated With White Spotting in Horses A novel variant in the regulatory region (5'UTR) of the KIT gene has been identified as a significant contributor to white spotting in horses, adding to the growing catalogue of KIT mutations known to influence coat pigmentation through effects on melanoblast migration. McFadden and colleagues examined the rs1149701677 variant (g.79,618,649A>C) across 109 horses, discovering that animals carrying at least one alternate allele exhibited substantially increased depigmentation with an average white score of 10.70 compared to 2.23 in homozygous reference animals (P = 1.892e-11). The variant displays high cross-species conservation (score 3.4) and computational predictions indicate moderate functional impact, suggesting it directly disrupts KIT regulation rather than merely marking a linked causal variant, though the authors acknowledge the latter possibility. Phenotypically, affected horses show the characteristic clear-bordered unpigmented regions on the body, face and limbs typical of KIT-related white spotting, designated here as "Holiday White" or W35 following established nomenclature. For breeders, geneticists and veterinarians involved in coat colour prediction and selective breeding programmes, this finding provides an additional genetic marker for identifying and managing white spotting inheritance patterns within horse populations, particularly useful given the visibility and consistency of the phenotype.
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Practical Takeaways
- •Breeders can now test for the W35 allele (rs1149701677) to predict white spotting severity in offspring, enabling informed breeding decisions
- •This genetic marker adds to the >30 known KIT variants associated with white spotting, improving understanding of coat color genetics in horses
- •Identification of regulatory variants in non-coding regions expands knowledge beyond coding mutations and may help explain white spotting in horses where coding variants are absent
Key Findings
- •A novel 5'UTR variant in KIT (rs1149701677: g.79,618,649A>C) is associated with increased white spotting in horses
- •Horses with at least one alternate allele showed average white score of 10.70 versus 2.23 in homozygous reference controls (P = 1.892e-11)
- •The rs1149701677 variant has high cross-species conservation score (3.4) suggesting regulatory importance for KIT gene expression
- •The variant is proposed to be termed 'Holiday White' or W35 and likely alters KIT regulation affecting melanoblast migration