Investigation of polymorphisms and association of the ABCG2 gene with milk production traits in sheep

The ATP-binding casette sub-family G member 2 (ABCG2) gene was chosen as a candidate gene influencing milk production traits in sheep based on its function and chromosomal localization. A number of fragments were sequenced, including the 3′UTR region, 16 exons, and regions within introns 4, 5 and 6, in samples collected from 11 Awassi and 2 Gyimesi Racka sheep. A single 35-base insertion/deletion, and a total of 13 single nucleotide polymorphisms (SNPs) were identified. SNP mutations found in exons (n=3) were synonymous. Two SNPs (g.703T>C, c.863+40G>A) and the insertion/deletion (c.683-80_46del) were chosen for further investigation, and an association study between these three polymorphisms and milk production traits was performed in both breeds (Awassi n=310, Gyimesi Racka n=75). The analysis revealed significant effect of two of the studied SNPs in Gyimesi Racka. Mutation g.703T>C showed significant effect on protein percentage (p<0.05) while the c.683-80_46del had a significant effect on somatic cell score (p<0.01). However, further studies are needed to evaluate these possible associations more effectively.