The Use of Genomic Screening for the Detection of Chromosomal Abnormalities in the Domestic Horse: Five New Cases of 65,XXY Syndrome in the Pura Raza Español Breed.

This research article describes a genomic screening process for detecting chromosomal abnormalities in domestic horses, with particular focus on the Pura Raza Español breed. Using this method, they identified five new cases of 65,XXY syndrome, akin to Klinefelter syndrome in humans, among 27,330 foals screened, making this the largest number of horses exhibiting such syndrome reported to date.

Genomic Screening Process

• The study focuses on a genomic screening protocol developed for Pura Raza Español horses with the aim of detecting chromosomal abnormalities that could lead to reproductive failure.
• The process begins with an initial assessment based on Short Tandem Repeat (STR) parentage testing. STR is a molecular biology technique used to compare specific loci on DNA for genetic analysis.
• Horses showing positive results or anomalies in STR testing are further analyzed using Single-Nucleotide Polymorphism (SNP) based copy number aberration (CNA) tests. SNP testing identifies variations in single DNA building blocks, while CNA tests check for regions of the genome that have been deleted or duplicated.

Findings of the Study

• Using this combined approach of STR screening followed by SNP/CNA testing, the researchers were able to identify five new cases of 65,XXY syndrome among 27,330 foals over two reproductive seasons.
• These cases were initially flagged due to abnormal results in STR testing. Further genotyping done using STR sex-linked dedicated panel and a medium-density SNP array confirmed the diagnosis.
• Four out of these five cases underwent further in-depth analysis using a technique called fluorescent in-situ hybridization, which confirmed the previous results.

Implications of the Study

• The study revealed one of the five horses exhibiting abnormal gonad development, though the remaining four appeared to have normal reproductive morphology.
• This substantial discovery emphasizes the relevance and efficacy of this genomic screening method in detecting chromosomal irregularities, which significantly influence the reproductive health of bred horses.
• The successful detection of horses with Klinefelter’s syndrome, the 65,XXY chromosomal disorder, demonstrates the advancement in animal genetics and presents an opportunity for further explorations in this domain.