A PCR-RFLP for KIT associated with tobiano spotting pattern in horses.

The researchers have identified a DNA polymorphism that strongly associates with the Tobiano spotting pattern in horses’ coats. By comparing DNA sequences from differently coated horses, they could create a test that identifies this genetic characteristic more effectively than other existing methods.

Research Methodology and Findings

• The researchers identified a polymorphism (a variation in the DNA sequence) in intron 13 of a gene called KIT. This was achieved by comparing DNA sequences from horses with solid coat colors, and horses homozygous (having two identical alleles of a particular gene) for the tobiano spotting gene (To).
• Two alleles (variants of a gene) were established – KM0 and KM1. KM0 is associated with a solid coat color, and the KM1 allele corresponds with the tobiano pattern. This latter allele creates an additional MspI restriction site – a location that a specific enzyme, MspI, can recognize and cut DNA, resulting in different length fragments.
• A Polymerase Chain Reaction – restriction fragment length polymorphism (PCR-RFLP) study was conducted using DNA from the horses’ hair follicles. The traditional PCR-RFLP process involves amplifying a DNA sample through a PCR reaction, then using restriction enzymes to cut the amplified DNA at specific sites, producing fragments of varying length depending on the DNA sequence. By comparing the lengths of these fragments, the presence or absence of specific sequences (in this case, the KM1 allele) can be assessed.
• All 129 horses with the tobiano pattern possessed the KM1 allele. Notably, though, three out of 104 solid-color horses also exhibited the KM1 allele. These results suggest that while the KM1 allele is strongly associated with the Tobiano gene, the association is not 100% guaranteed.

Significance and Implications

• This research has significant implications for the genetic study of coat patterns in horses. It provides a new, more accurate method of identifying the tobiano gene than existing biochemical testing methods, which use albumin (Alb) and vitamin D binding protein (Gc) haplotypes for identification.
• Despite the strong association between the Tobiano gene and the KM1 allele, there exist instances where a solid color horse can possess the KM1 allele. This could suggest the presence of other genetic or environmental factors that suppress the expression of the Tobiano pattern even with the presence of the KM1 allele.
• The findings can be used to understand the genetic basis of coat color patterns better and could be applied in breeding programs aimed at producing specific coat patterns in horses.