Cytogenetic Analysis of Sex Chromosome Abnormalities in Equines

Sex chromosome abnormalities in horses encompass a range of conditions that compromise fertility, development and early gestation. The most prevalent anomalies include X-monosomy (Turner syndrome), 65,XXY (Klinefelter syndrome), SRY-negative XY male-to-female sex reversal and mosaic forms of these karyotypes. Traditional cytogenetic approaches, such as G-banding karyotyping, remain the frontline method for identifying gross numerical and structural aberrations. In parallel, molecular techniques—including fluorescent in situ hybridisation, SNP genotyping arrays, digital droplet PCR and whole-genome sequencing—have enhanced resolution and throughput, enabling detection of submicroscopic copy number variants and elucidation of breakpoint regions. These integrated strategies have clarified mechanisms underlying meiotic nondisjunction, Robertsonian fusions and deletions affecting sex-determining genes. Understanding equine sex chromosome anomalies carries significant implications for breeding programmes, as early pregnancy loss, embryonic lethality and reproductive failure incur substantial economic and welfare impacts. Moreover, the horse serves as a comparative model for human reproductive genetics, particularly in exploring age-related aneuploidy and the functional consequences of X-linked gene dosage. Ongoing advances in genomic screening promise to refine diagnostic pipelines, facilitate population-level surveys and inform management of valuable bloodstock worldwide.

Research from Nature Portfolio

Whole-genome analysis of naturally occurring early pregnancy losses in horses has revealed that aneuploidies account for over 20% of spontaneous miscarriages. By applying high-density genotyping arrays followed by whole-genome sequencing and digital droplet PCR validation, researchers demonstrated that a spectrum of autosomal and sex chromosome trisomies, previously unreported in live-born equines, are embryonically lethal. These findings not only establish the horse as a viable model for studying aneuploidy but also underscore parallels with human miscarriage rates and the influence of maternal age on chromosomal nondisjunction.

Cytogenetic Analysis of Sex Chromosome Abnormalities in Equines publication trend

The graph below shows the total number of articles in cytogenetic analysis of sex chromosome abnormalities in equines across all publications each year (not limited to Nature Index journals).

Technical terms

Aneuploidy: The presence of an abnormal number of chromosomes in a cell, often due to meiotic nondisjunction.

Karyotype: The complete chromosome complement of an organism, visualised by banding techniques to reveal numerical and structural variants.

Fluorescent in situ hybridisation (FISH): A cytogenetic method that uses fluorescent probes to localise specific DNA sequences on chromosomes.

SNP array: A high-throughput platform that genotypes thousands of single nucleotide polymorphisms to detect copy number changes and loss of heterozygosity.

Short tandem repeat (STR): A repetitive DNA motif used in parentage testing and initial screening for chromosomal abnormalities.

References

1. Whole genome analysis reveals aneuploidies in early pregnancy loss in the horse. Scientific Reports (2020).
2. Horse Clinical Cytogenetics: Recurrent Themes and Novel Findings. Animals (2021).
3. Prevalence of Sex-Related Chromosomal Abnormalities in a Large Cohort of Spanish Purebred Horses. Animals (2023).
4. 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. Animals (2024).