Close association between sequence polymorphism in the KIT gene and the roan coat color in horses.

This research explores a strong association between sequence variation in the KIT gene and the roan coat color in horses. However, the study could not identify the exact mutations responsible for this trait and stressed the need for additional analysis.

Understanding the Research Problem

• The study seeks to understand the genetic factors contributing to the color of a horse’s coat, specifically the roan pattern. The roan color is a mixture of white and colored hairs, and its expression is controlled by a dominant allele that is lethal if it occurs in pairs (homozygous condition).
• The researchers focused on the KIT gene, which is involved in pigmentation, and its possible involvement in the expression of the roan coat color.

Methods of the Study

• The researchers expanded the linkage group II (LGII) with KIT and PDGFRA genes, using RFLP and linkage analysis. Linkage groups are clusters of genes that tend to be inherited together.
• Sequence analysis of RT-PCR products led to the determination of almost the complete KIT-encoding sequence in horses.
• In total, three different alleles of the horse KIT gene were compared, displaying five sequence polymorphisms along with several mRNA splice variants. However, none of these were found to be directly linked with the expression of the roan coat color (Rn).

Key Findings

• A certain TaqI RFLP in the KIT gene, indicating a synonymous substitution in exon 19, was found in strong linkage disequilibrium with the roan coat color. Linkage disequilibrium refers to a non-random association of alleles at different loci, indicating that these variations are often inherited together.
• A specific insertion of a partial LINE1-element (a type of transposable element) occurring between exons 1 and 2 and causing a frameshift, was detected in about 30% of the KIT transcripts from the Belgian roan horse under study. However, this insertion was not observed to be associated with the roan coat phenotype upon further testing with other horses.

Conclusions and Implications

• Despite not identifying direct mutations corresponding with the roan coat color, the research reinforced the hypothesis that the KIT gene plays a significant role in control over this trait.
• The researchers highlighted the need for continued analysis and investigation to finally decipher the precise genetic mutations giving rise to the roan coat color in horses.