Bridging Genomics and Proteomics to Unravel Variability and Complexity of Milk Proteins

There is increasing substantial evidence that milk contains many health-promoting compounds, impacting physical functions or reducing disease risk. Numerous substantiated or potential bioactive protein components have been found and many others still remain to be identified either as intact protein or as derived peptides, encrypted in the sequence of milk proteins. This is probably one of the greatest challenges facing the milk science in the very next years to provide the food industry and consumers with the basis for health-promoting properties before their inclusion as ingredients into functional foods.
Milk proteins are found in the lipid phase (associated with the fat globule membrane) and mostly in the aqueous phase either at the soluble state (whey proteins, of which very few are synthesized in the mammary epithelial cells while the large majority have a serum origin) or at the colloïdal state (caseins). Regarding the casein fraction, several tens of genetic variants have been characterized so far in cow, ewe and goat milks. The past twenty years have seen remarkable progress in the understanding of milk protein genes structure and function. Developments in molecular biology, genomics and proteomics have particularly highlighted how such genetic polymorphisms are deeply responsible for the extreme complexity and the large variability (qualitative and quantitative) of the milk protein fraction, across but also within species. Relying on recent and meaningful examples taken in different species, the purpose of the present lecture will be to show how genetic polymorphisms may modulate the protein fraction of milk by affecting different cellular processes, mainly at the post transcriptional level.