Genomic architecture of bovine kappa-casein and beta-lactoglobulin

Abstract

The objective of this study was to characterize the genetic architecture underlying the absolute concentrations of 2 important milk proteins, kappa-casein (kappa-CN) and beta-lactoglobulin (beta-LG), in a backcross population of (Holstein x Jersey) x Holstein cattle. A genomewide association analysis was performed using a selective DNA pooling strategy and the Illumina BovineHD BeadChip assay [777,000 (777K) SNP markers; Illumina Inc., San Diego, CA]. After correction for multiple testing, 25 single nucleotide polymorphisms were found to be associated with kappa-CN and 36 single nucleotide polymorphisms were associated with beta-LG. A pathway association analysis revealed 15 Gene Ontology (GO) terms associated with the is kappa-CN trait and 28 GO terms associated with beta-LG. In addition, several GO terms were associated with both milk proteins. Further analysis revealed that kappa-CN and beta-LC production is regulated by both kinase and phosphatase activity, including mechanisms regulating the extracellular matrix. These results are in concordance with the complex multihormonal process controlling the expression of milk proteins and interactions between mammary epithelial cells and extracellular matrix components. Although kappa-CN and beta-LG milk proteins are expressed by single genes, the results from this study showed that many loci are involved in the regulation of the concentration of these 2 proteins.