The use of molecular and cytogenetic methods as a valuable tool in the detection of chromosomal abnormalities in horses: a case of sex chromosome chimerism in a Spanish purebred colt.

The research is focused on the use of molecular and cytogenetic methods for identifying chromosomal abnormalities in horses, with a special case study on a Spanish purebred colt with sex chromosome chimerism.

Background

• The study begins by pointing out the commonality of chromosomal abnormalities related to sex chromosomes in horses, which often go undetected due to the complicated nature of the horse karyotype and the general lack of interest from breeders and veterinarians.
• The article highlights the Spanish Purebred Breeders Association’s decision to implement a DNA paternity test for every newborn foal about a decade ago, leading to the spotting of cases with abnormal or uncertain results that then undergo cytogenetic analysis to check for chromosomal abnormalities.

Case Study

• The paper focuses on the case of a foal that showed 3 to 4 different alleles at several loci during a Short Tandem Repeat (STR)-based DNA parentage test. To confirm these results, a filiation test was performed which yielded normal results.
• A thorough set of traditional and molecular cytogenetic analysis was carried out to understand their chromosomal components.
• The foal was found to have sex chimerism 64,XX/64,XY with a cellular percentage of 70/30 in blood samples, as evidenced through C-banding and FISH (Fluorescence In Situ Hybridization) techniques.

Conclusion

• The study concludes by emphasizing that a combined diagnostic approach using routine parentage QF-PCR-based STR screening with classical or molecular cytogenetic analysis can be a potent tool.
• This approach allows for early detection of foals likely to have poor or even non-existent reproductive performance because of chromosomal abnormalities, thereby saving breeders’ time, effort, and resources.