Molecular screening of XY SRY-negative sex reversal cases in horses revealed anomalies in amelogenin testing.

This research article discusses the study of male-to-female sex reversal in horses, a developmental disorder causing female horses to possess male genetics. The study focused on screening and testing methods, revealing inconsistencies in previous testing using the sex marker gene amelogenin.

Research Overview

• The study’s focus is on male-to-female sex reversal in horses, which is a developmental disorder. This disorder causes horses that appear female (phenotypic females) to have a male genetic constitution. This is the second-most prevalent genetic sex anomaly in horses, following X chromosome monosomy.
• The research is important because all male-to-female sex reversal cases studied so far have been found to be infertile. Hence, accurate screening tests are essential, especially in labs carrying out DNA genotyping in horses.

Findings and Methodology

• A large-scale testing was conducted in the researchers’ laboratory, which involved testing over 209,000 horses for parentage using a panel of microsatellite markers and the sex marker gene amelogenin. Microsatellite markers are units of repetitive DNA used to measure the level of genetic variation.
• Cases of suspected XY sex reversal are reported as females with a male profile in amelogenin testing. After the initial test, 49 such cases were detected, and these were further tested using the sex-determining region Y (SRY) gene. This additional testing confirmed the XY SRY-negative genotype of the suspected sex reversal cases.
• However, there were some inconsistencies in the initial amelogenin test results. Due to this, the researchers analyzed a molecular panel of X- and Y-linked markers for these samples. This process identified several false-positives and validated 33 cases of XY SRY-negative from the original sample of 49.

Conclusion and Implications

• The study concluded that the amelogenin testing method for identifying XY sex reversal in horses could produce false-positive results, leading to inaccurate diagnostics. From the original 49 suspected cases, 16 were identified as false positives due to anomalies in the amelogenin testing.
• The research implies that the current testing procedures for male-to-female sex reversal in horses may need refinement or supplementation with additional testing methods to improve accuracy and reduce the rate of false positives.