Characterization of an Equine α-S2-Casein Variant Due to a 1.3 kb Deletion Spanning Two Coding Exons.
Authors: Brinkmann Julia, Koudelka Tomas, Keppler Julia K, Tholey Andreas, Schwarz Karin, Thaller Georg, Tetens Jens
Journal: PloS one
Summary
# Editorial Summary: Equine α-S2-Casein Genetic Variation and Mare's Milk Allergenicity Rising commercial interest in mare's milk across Europe, driven by documented health benefits and reduced allergenicity compared to bovine milk, has prompted investigation into the genetic basis of equine milk protein composition. Brinkmann and colleagues characterised two distinct variants of equine α-S2-casein resulting from a 1.3 kb in-frame deletion spanning two coding exons—one of which represents an equid-specific duplication—by sequencing DNA and cDNA from mare's milk samples of known genotypes and confirming protein expression through mass spectrometry and gel electrophoresis. Both casein variants were confirmed to be functionally expressed at the protein level, with phylogenetic analysis suggesting the deletion arose before horses, asses and zebras diverged evolutionarily. Understanding these naturally occurring genetic variants in equine milk proteins has implications for producers selecting breeding stock intended for milk production, and may help explain individual variation in the allergenic potential of mare's milk—potentially opening avenues for selective breeding towards hypoallergenic milk for human consumers with dairy sensitivities. This work establishes a foundation for investigating how genetic diversity in milk proteins influences digestibility and immunological responses in both human consumers and in young foals receiving mare's milk supplementation.
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Practical Takeaways
- •Mare's milk protein variants may differ from cow's milk in ways that affect allergenicity; understanding these genetic differences could help optimize equine milk products for human consumption
- •Genetic testing could potentially identify mares producing milk with different casein profiles for targeted marketing of hypoallergenic mare's milk products
- •This work establishes a foundation for further research into how equine milk protein genetic variants might relate to digestibility and health benefits in consumers
Key Findings
- •A 1.3 kb in-frame deletion spanning two coding exons in equine α-S2-casein was identified and characterized at DNA and protein levels
- •Both protein variants arising from this deletion are actually expressed in mare's milk as confirmed by LC-MS analysis
- •The deletion likely occurred before the evolutionary divergence of horses, asses, and zebras, indicating ancient origin