Two Novel Variants in MITF and PAX3 Associated With Splashed White Phenotypes in Horses.

The research identifies two novel genetic variants in the MITF and PAX3 genes associated with the splashed white coat pattern in horses, a specific pattern of depigmentation that appears as if the horse was splashed with white paint.

Genetic Elements of Depigmentation in Horses

• The researchers studied depigmentation in horses, which is a common trait associated with over 40 alleles in multiple genes.
• Splashed white phenotype, a unique pattern of depigmentation, was known to be associated with variants in the PAX3 and MITF genes.
• The PAX3 and MITF genes control melanocyte migration and pigmentation, which are essential for color variations in horses.

New Mutations, Associated Scoring, and Results

• The study identified two new mutations that lead to depigmentation in Pura Raza Española breed horses.
• A stop-gain mutation in PAX3 and a missense mutation in a binding domain of MITF showed a strong association with increased depigmentation in horses.
• The researchers quantified depigmentation with a new scoring system.
• The PAX3 and MITF mutations had average white scores of 25.50 and 24.45, respectively, compared to the average white coat spotting score of 1.89 in the control set.

Implications and Conventions

• The functional impact of the mutations is predicted to range from moderate to extreme.
• The results propose the naming of the MITF mutant allele as Splashed White 9 and the PAX3 mutant allele as Splashed White 10, following established naming conventions.

Overall, this study contributes to the understanding of genetic variations leading to coat color variations in horses, which has implications for breeding strategies and for the enhancement of the aesthetics and diversity of horse populations.