Characterization of equine CSN1S2 variants considering genetics, transcriptomics, and proteomics

Area of Science:

• Animal Genetics
• Dairy Science
• Molecular Biology

Background:

• Growing interest in horse milk composition and its impact on human health.
• Previous studies noted variability in equine milk components but lacked genetic insights.
• Limited knowledge exists regarding the equine α-S2 casein gene (CSN1S2) structure and expression.

Purpose of the Study:

• To investigate the genetic basis of variation in equine milk composition.
• To characterize the structure and polymorphism of the horse CSN1S2 gene.
• To explore the association between CSN1S2 genetic variants and milk protein content.

Main Methods:

• Direct sequencing of the equine CSN1S2 coding sequence.
• Bioinformatic analysis to identify sequence variations and their genomic location.
• Genotyping of polymorphic forms across different horse breeds.
• Quantification of CSN1S2 gene expression at the transcript and protein levels.

Main Results:

• Discovery of a 51-bp insertion-deletion (in/del) polymorphism in the CSN1S2 gene, caused by a 1.3-kb genomic deletion.
• Identification of two polymorphic forms (A and B) with uneven breed distribution, with variant B prevalent in cold-blooded horses.
• Association of the CSN1S2 polymorphism with CSN1S2 expression levels, particularly impacting milk protein content (BB genotype showed highest expression).

Conclusions:

• The study elucidates the structure of the equine CSN1S2 gene and identifies a significant polymorphism.
• The identified CSN1S2 variants are linked to variations in milk protein content, with implications for horse milk quality.
• This research provides a foundation for future studies on horse milk casein functionality, including allergenicity and physiochemical properties.