Genetically-modified milk

Casein is the major protein component of milk and is an important contributor to its nutritional value and processing properties. Bovine milk contains four casein proteins that aggregate into large colloidal micelles to give milk its particular functional characteristics. In an Advanced Online Publication in Nature Biotechnology Brophy and colleagues at the Ruakura Research Centre in New Zealand describe the use of transgenic and nuclear-transfer technologies to create cloned cows with altered casein production (Nature Biotechnology, 27 January 2003, doi;10.1038/nbt783). Brophy et al. engineered female bovine fetal fibroblasts to express transgenes encoding for bovine β- and κ-casein (CSN2 and CSN3 genes). The modified cell lines were used to created eleven cloned calves. Milk from the cloned animals was enriched for transgene-derived caseins, demonstrating the potential of this technology to make better milk.