Two Novel Variants in MITF and PAX3 Associated With Splashed White Phenotypes 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
# Splashed White Coat Patterns: Two Newly Identified Genetic Variants in Equine Depigmentation Researchers have identified two previously undocumented mutations responsible for the distinctive splashed white coat phenotype in horses, expanding our understanding of the genetic basis for depigmentation disorders in the species. The study examined DNA variants in PAX3 and MITF—genes encoding transcription factors critical to melanocyte migration and pigmentation—in a cohort of Pura Raza Española horses, identifying a stop-gain mutation in PAX3 and a missense mutation in MITF's binding domain, each showing exceptionally strong statistical associations with increased white spotting (P values of 1.144E-11 and 4.441E-16 respectively). Horses carrying either mutation exhibited white coat scores averaging 25.50 and 24.45 compared to just 1.89 in unaffected controls, demonstrating marked phenotypic expression. Computational analysis predicted both mutations to have moderate-to-extreme functional consequences for protein structure and function. These findings have practical implications for breeders selecting for or against splashed white phenotypes, and they contribute to the growing catalogue of equine coat colour genetics—now encompassing over 40 distinct alleles—which may help veterinary professionals better counsel clients on inheritance patterns and assist in identification of carrier animals within breeding programmes.
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Practical Takeaways
- •Genetic testing for PAX3 and MITF mutations can now help identify horses carrying splashed white phenotype alleles, enabling informed breeding decisions in Pura Raza Española and potentially other breeds
- •Breeders should be aware that these two novel mutations are strongly associated with splashed white patterning and depigmentation if they wish to avoid or select for this trait
- •The identification of these variants expands understanding of depigmentation genetics in horses and may have implications for coat color predictability in breeding programs
Key Findings
- •Two novel mutations identified: a stop-gain mutation in PAX3 (c.927C>T) and a missense mutation in MITF (c.993A>T), each strongly associated with splashed white phenotype in Pura Raza Española horses (P = 1.144E-11 and P = 4.441E-16 respectively)
- •PAX3 and MITF mutations showed average white coat scores of 25.50 and 24.45 respectively, compared to 1.89 in control horses, representing a 13-fold increase in depigmentation
- •Both mutations predicted to have moderate to extreme functional impact on their respective transcription factors controlling melanocyte migration and pigmentation
- •New variants designated as Splashed White 9 (MITF) and Splashed White 10 (PAX3), bringing total known white spotting alleles to over 40