Genetic analysis of the equine orthologues for human CYP2D6: unraveling the complexity of the CYP2D family in horses.
Authors: Scantamburlo Giada, Nofziger Charity, Paulmichl Markus, Vanoni Simone
Journal: Frontiers in veterinary science
Summary
# Editorial Summary: CYP2D Family Genetics in Horses The cytochrome P450 enzyme CYP2D6 metabolises approximately 25–30% of drugs used in human medicine, yet the equine equivalent remains poorly characterised despite horses receiving numerous pharmaceutical treatments where individual drug clearance rates vary considerably between individuals. Scantamburlo and colleagues sequenced genomic DNA and hepatic mRNA from equine samples to map the structure, expression patterns and genetic variation of the CYP2D family in horses, with particular focus on CYP2D50—the primary equine orthologue. The research revealed a previously unreported genomic architecture for CYP2D50, including a hybrid gene structure analogous to that observed in human CYP2D6, alongside evidence that six distinct CYP2D family members are expressed in equine liver tissue; critically, multiple novel polymorphisms were identified in both CYP2D50 and CYP2D82, with six variants in each gene predicted to alter amino acid sequences and potentially affect enzyme function. These findings establish the foundation for understanding inter-individual variation in drug metabolism among horses, offering farriers, veterinarians and coaches a rational basis for anticipating variable drug withdrawal times and treatment responses—particularly important for performance horses where precise pharmacokinetic predictions directly impact competition eligibility and therapeutic efficacy.
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Practical Takeaways
- •Individual horses may metabolize drugs differently due to CYP2D genetic polymorphisms, which could explain variable drug withdrawal times observed in clinical practice.
- •Pharmacogenetic testing of CYP2D50 and CYP2D82 variants may eventually enable personalized drug dosing protocols in equine medicine.
- •This foundational research supports future development of equine-specific guidelines for drug selection and dosing based on genetic profiles.
Key Findings
- •CYP2D50 exhibits a novel genomic structure with hybrid formation similar to human CYP2D6, differing from previous EquCab3.0 assembly predictions.
- •Six different members of the equine CYP2D family are expressed in horse liver tissue.
- •Multiple polymorphisms identified in CYP2D50 and CYP2D82, including six novel nonsynonymous amino acid changes in each gene that may affect drug metabolism.