THE MAMMARY-GLAND AS A BIOREACTOR

The mammary gland has the capacity to synthesize and secrete large amo unts of protein. With the help of molecular biology and embryology it is possible to introduce hybrid genes consisting of mammary specific g enetic control elements and protein coding sequences into the genome o f farm animals. These transgenic animals can produce qualitatively and quantitatively altered milk. The mammary gland could thus be an ideal bioreactor for the production of proteins which otherwise cannot be s upplied in sufficient quantities, such as blood clotting factors for t he treatment of hemophiliacs. The isolation of mammary specific regula tory elements provided the basis for the genetic alteration of the mam mary gland. These elements (promoters and enhancers) have the capacity to target the expression of genes solely to the mammary gland. In the future it will be possible to genetically tailor transgenic animals a nd thereby produce customized milk. Of importance to agriculture will be the introduction of transgenic cows which will synthesize milk with a higher protein content. This will enable us to obtain the same amou nt of milk products from less cows. By that token transgenic technolog y can be considered a contribution to animal welfare and a cleaner env ironment.