CLONING OF 5'-REGULATORY ELEMENT OF BOVINE BETA-LACTOGLOBULIN GENE AND ITS UTILIZATION IN GENERATION OF MAMMARY BIOREACTORS

To obtain a regulatory element for generating mammary bioreactors, a D NA fragment derived from bovine beta-lactoglobulin (BLG) gene was clon ed, which consisted of a 650-bp 5' flanking sequence, exon I, intron I and exon II. A 661-bp region of the cloned fragment, consisting Of th e 650-bp 5' flanking sequence and a non-coding sequence of 11 bp downs tream of the transcription initiation site, was used as a regulatory e lement to combine with human growth hormone (hGH) gene to generate a b ovine BLG/hGH fusion construct, which was then introduced into culture d primary mammary epithelial cells of goat for transient expression of hGH gene. It was demonstrated that the hGH gene was able to express f ollowing hormone induction and the expressed product was able to be se creted into the medium. The bovine BLG/hGH fusion construct was also u sed to generate transgenic mice by microinjection. Subsequently, five transgenic mice were generated. The hGH in milk by one transgenic fema le mouse was 420 mu g/mL, while the content of hGH in serum was 0.051 mu g/mL only. This indicated that the cloned regulatory element in thi s experiment could make the expression of target gene occur almost spe cifically in mammary gland and the expressed product could be secreted with milk.