Validation of high-resolution melting analysis as a diagnostic tool for endothelin receptor B mutation in American Paint horses and allele frequency estimation.

The research deals with the development and validation of a genetic testing method which can be used to detect a life-threatening genetic disorder in American Paint horses. The disorder, known as Overo lethal white foal syndrome (OLWFS), is present in heterozygosity and particularly high-frequency among Overo horses.

Research Objective

• The primary aim of this research was two-fold: to develop and then validate a high-resolution melting (HRM) genotyping assay for the detection of a lethal dinucleotide mutation in the endothelin receptor type B (EDNRB) gene, responsible for OLWFS; and to estimate the prevalence of this gene mutation in the American Paint Horse population in Brazil, especially among Overo horses.

Methodology

• The researchers used HRM genotyping assay for detecting the dinucleotide mutation in the EDNRB gene, which is known to result in OLWFS. The validation of the assay was evaluated based on its sensitivity, specificity, and both positive and negative predictive values.
• They also undertook a population-based survey to estimate the frequency of the OLWFS causative gene mutation in American Paint Horses.

Findings

• The HRM genotyping assay displayed high sensitivity and specificity. This suggests that the test was very accurate in detecting true cases (high sensitivity) and ruling out the ones without the disorder (high specificity).
• The positive and negative predictive values of the test were also high, meaning the possibility of obtaining a true positive or a true negative result was highly reliable.
• The allele frequency of the gene mutation among the American Paint Horse in Brazil was found to be 21.6%. This indicates that about 21.6% of the tested horses carried the mutant allele.
• However, when the research focused specifically on Overo horses, the percentage carrying the gene mutation skyrocketed to 89.5%. This shows the high susceptibility of Overo horses to the disorder.

Implications

• The research found that the HRM genotyping assay is a reliable, precise, and quick method for detecting OLWFS in horses. This diagnostic tool can help equine practitioners or breeders detect the disorder early, thus preventing the birth and suffering of affected animals.
• It also revealed that the mutation is common in the American Paint Horse population in Brazil, particularly among Overo horses. This will help in planning genetic counseling and breeding programs to manage the disorder effectively.