Two Variants of KIT Causing White Patterning in Stock-Type Horses.

The study investigates the genetic causes behind the distinctive white spotting patterns seen on certain breeds of horses. The researchers found two variants of a gene that were associated with this particular trait.

Objective of the Study

• The main objective of this research was to study the genetic basis of white spotting patterns in horses. They focused on two major causative genes, KIT and MITF, which have been previously implicated in these patterns.

Research Methodology

• The study involved two families of horses with distinctive white spotting patterns. The first family included a Quarter Horse stallion and four offspring, while the second family included a dam and six half-sibling American Paint Horse/Quarter Horses.
• The researchers performed an approach known as candidate-gene sequencing on these two families to study mutations in the KIT and MITF genes.

Findings

• Analysis of the two families led to the discovery of two variants significantly associated with the white spotting patterns noticed in each family. In the first family, the researchers found an indel (insertion or deletion of bases in the genome of an organism) that leads to a frameshift mutation (a genetic mutation caused by indels).
• This variant in the first family is termed ‘W31’. It changes the protein sequence that results in an early stop codon. A stop codon is a nucleotide triplet within mRNA that signals a termination of translation. This mutation truncates the normal amino acid sequence from 972 to just 115 amino acids.
• In the second family, the researchers found a non-synonymous single-nucleotide polymorphism (SNP), which means a difference in a single DNA building block, or nucleotide. This variant is known as ‘W32’.
• While the W31 variant seems to directly alter the horse’s phenotype, the impact of the W32 variant is less clear. It may subtly affect the receptor function or it could be linked to a change that is outside the coding region, possibly involving the regulation of the gene.

Validation

• After identifying the specific variants, the researchers validated their findings by studying an unrelated population of horses and discovered the same mutation. They also used multiple bioinformatics software to assess the functional impact of these mutations on the protein structure and function.

Significance

• Overall, this study enhances our understanding of the genetic factors influencing coat color and patterns in horses and could contribute to our knowledge of genetics in general. This could potentially be useful for horse breeding programs, trait selection, and even genetic disease management.