TBX3 and ASIP genotypes reveal discrepancies in officially recorded coat colors of Hucul horses.

The research article reveals discrepancies in coat colors of Hucul horses recorded in the Polish Horse Breeders Association database compared to colors predicted by genotyping TBX3 and ASIP polymorphisms. It was found that a significant portion of the recorded coat colors disagreed with the genotype predicted phenotypes.

Methods and Findings

• The research team genotyped the previously identified polymorphisms within two significant coat color genes, TBX3 (T-box 3) and ASIP (Agouti Signaling Protein) in 462 Hucul horses.
• They compared these genotypes with the observed pigmentation types as recorded in the Polish Horse Breeders Association database.
• They found that the genotype predictions for coloration and the officially recorded coat colors disagreed for 157 horses, representing around 34% of the individuals studied.

Common Errors

• The most common mistake was the misclassification of horses with the nd1/nd1 and nd1/nd2 genotypes. This misclassification may be due to the occurrence of ‘intermediate’ dilution phenotypes in such individuals.

Dilution Effect and D Allele

• The research team confirmed that the occurrence of the dominant dun dilution allele (D) was more frequent (0.30 frequency) than previously suggested by available studbooks.
• They discovered that the D allele(s) could be ‘hidden’ in various phenotypic groups, including dark bay and black horses, suggesting that the dun dilution effect itself might not be as strong in Hucul horses as it is in other horse breeds.
• The team hypothesized this might be due to an additional genetic modifier suppressing the phenotypic effect of the D allele.

Implications of Findings

• The discovery of these discrepancies underscores the need for a more accurate method of determining coat colors in Hucul horses, particularly given the variation in color shades and segregation of multiple dun dilution variants.
• The genotyping of coat color genes could provide a more precise way to predict and classify coat colors than observational methods.
• These findings could also shed light on the genetic mechanisms underlying coat color variation in other horse breeds.