Azoospermia and Y Chromosome-Autosome Translocation in a Friesian Stallion.
Authors: Ruiz Agustin J, Castaneda Caitlin, Raudsepp Terje, Tibary Ahmed
Journal: Journal of equine veterinary science
Summary
# Editorial Summary: Y Chromosome Translocation and Azoospermia in a Friesian Stallion A Friesian stallion presenting with a history of infertility and consistently azoospermic ejaculates underwent comprehensive reproductive evaluation, revealing no gross anatomical defects despite subnormal testicular volume. Alkaline phosphatase analysis confirmed testicular origin of the azoospermia, whilst histopathological examination post-castration demonstrated early spermatogenic arrest at the level of germ cell development. Cytogenetic analysis identified a novel Y chromosome-autosome translocation involving chromosome 13—the first documented case of azoospermia linked to a cytogenetically detectable equine Y chromosome abnormality. This finding suggests that the equine Y chromosome contains gene sequences essential for normal spermatogenesis, with significant implications for breeding selection and genetic screening in affected breeds. Practitioners should consider chromosomal analysis in cases of idiopathic azoospermia and testicular hypoplasia, particularly when conventional diagnostic approaches exclude other aetiologies, to identify carriers and prevent propagation of deleterious Y chromosome variants through breeding populations.
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Practical Takeaways
- •Stallions presenting with infertility and azoospermia should undergo cytogenetic analysis to identify chromosomal abnormalities as a potential underlying cause
- •Y chromosome abnormalities should be considered in the differential diagnosis of spermatogenic failure even when testicular ultrasound and external genitalia appear normal
- •Affected stallions should be identified and removed from breeding programs to prevent transmission of chromosomal abnormalities to offspring
Key Findings
- •A Friesian stallion with azoospermia was found to have a unique translocation between the Y chromosome and chromosome 13
- •Testicular biopsy confirmed early spermatogenic arrest with no other gross anatomical abnormalities except reduced testicular size
- •This is the first documented case of azoospermia with a cytogenetically detected Y chromosome abnormality in equines
- •The finding suggests the horse Y chromosome contains sequences essential for normal spermatogenesis