Genetic effects of ABCG2 polymorphism on milk production traits in the Chinese Holstein cattle

The ATP-binding cassette G2 (ABCG2), a drug transporter gene, mainly has a xenotoxin protective function. Xenotoxins are transferred from the mother to the suckling infant via milk that is difficult to reconcile with a protective role. ABCG2 is located within a linkage region with Quantitative Trait Locus (QTL) for milk production and milk content resulting from it represents a functional candidate gene for association with milk production traits in dairy cattle. In the present study, we investigated the polymorphism of ABCG2 gene, using pooled DNA sequencing, as a result, a single nucleotide polymorphism, transversion at position g.45599 A > C, was found and then genotyped with Matrix-assisted laser desorption/ionisation time of flight mass spectrometry technique in 752 Chinese Holstein cows. Significant differences were revealed between ABCG2 genotypes in the protein yield and protein concentration. CC cows at the g.45599 A > C locus showed the highest protein yield and protein concentration, with more than 2.65 kg and 0.04%, respectively, compared with AA cows; heterozygous AC cows indicated intermediate position. The allele substitution results demonstrated that g.45599 A > C-A allele decreased protein yield (1.27 kg) and protein percentage (0.019%), which suggested that g.45599 A > C-C allele increased protein yield and protein percentage. The results suggested that identified polymorphism could be a potential genetic marker to improve the production performance of Chinese Holstein.