A proteomic approach to investigate the qualitative and quantitative polymorphism of β-lactoglobulin in ovine milk: Inference on gene copy-number variations

G. Picariello, A. Di Luccia, P. Ferranti, I. Alloggio, F. Addeo, E. Pieragostini

Department of Animal Production, University of Bari, Bari, Italy.
Department of Food Science, University of Naples “Federico II”, Naples, Italy.
Department of Science Agriculture, Food, & Environment (SAFE), University of Foggia, Foggia, Italy.
Institute of Food Science and Technology, National Research Council of Italy (CNR), Avellino, Italy.

DOI: 10.4236/abc.2012.23025                

Abstract

The rationale of this work is based on recent evidences suggesting that: 1) both qualitative and quantitative β-lactoglobulin (β-LG) polymorphism may be found in bovine milk; 2) quantitative polymorphisms are often the result of expression gradients in multiple copies of a gene; 3) the β-LG gene is duplicated in the dog and bovine genome; 4) mammary genes are highly conserved across Mammalia. Thus, an investigation was conducted on ovine β-LG polymorphism checking phenotypic evidence for copy-number variants of β-LG in sheep. To the purpose, 206 milk samples were collected, during a small-scale survey within sheep farms breeding Southern Italian breeds. PAGIF screening of the samples revealed that approximately 50% individuals exhibited β-LG polymorphism and 4 different quantitative patterns, which were characterized in detail by a proteomic approach relying on combined chromatographic and mass spectrometric techniques. The expected figures based on the expression gradient models were compared with well-established α-globin gene arrangements in sheep. The different phenotypes suggest the presence of both duplicate and triplicate BLG haplotypes. The occurrence of a triplicate haplotype was supported by population data. The current study supports the helpfulness of up-to-date proteomics for inferring copy number polymorphisms through the characterization of the phenotypic expression.

Keywords

Quantitative Polymorphism; β-Lactoglobulin; HPLC-ESI MS; MALDI-TOF Mass Mapping; Gene Duplication; Gene Arrangements; Copy-Number Variations (CNVs)

Conflicts of Interest

The authors declare no conflicts of interest.

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