Genomic analysis of the major bovine milk protein genes

TLDR

The major bovine milk proteins include four caseins (αs1, αs2, β, κ) and two whey proteins (α‑lactalbumin and β‑lactoglobulin). Using bovine‑hamster hybrid somatic cells, the authors mapped the milk protein genes to three bovine chromosomes. The genes were mapped to three chromosomes, with the four caseins tightly linked on chromosome 6 (q31‑33) in the order CASAS1‑CASB‑CASAS2‑CASK, while LALBA and LGB mapped to syntenic groups U3 and U16, respectively, and polymorphisms were detected across six loci in three cattle breeds.

Abstract

The genomic arrangement of the major bovine milk protein genes has been determined using a combination of physical mapping techniques. The major milk proteins consist of the four caseins, α s1 (CASAS1), α s2 (CASAS2), β (CASB), and ϰ (CASK), as well as the two major whey proteins, α-lactalbumin (LALBA) and β-lactoglobulin (LGB). A panel of bovine X hamster hybrid somatic cells analyzed for the presence or absence of bovine specific restriction fragments revealed the genes coding for the major milk proteins to reside on three chromosomes. The four caseins were assigned to syntenic group U15 and localized to bovine chromosome 6 at q31 - 33 by In situ hybridization. LALBA segregated with syntenic group U3, while LGB segregated with U16. Pulsed-field gel electrophoresis confirmed genetic mapping results indicating tight linkage of the casein genes. The four genes reside on less than 200 kb of DNA in the order CASAS1-CASB-CASAS2-CASK. Multiple restriction fragment length polymorphisms were also found at the six loci in three breeds of cattle.