Cerdán M G, Young J I, Zino E, Falzone T L, Otero V, Torres H N, Rubinstein M
Instituto de Investigaciones en Ingeniería Genética y Biología Molecular (CONICET-UBA), Buenos Aires, Argentina.
Mol Reprod Dev. 1998 Mar;49(3):236-45. doi: 10.1002/(SICI)1098-2795(199803)49:3<236::AID-MRD3>3.0.CO;2-P.
The spatial, temporal, and hormonal pattern of expression of the beta-casein gene is highly regulated and confined to the epithelial cells of the lactating mammary gland. Previous studies have shown that 1.7 kb of the bovine beta-casein promoter were able to drive cell-specific and hormone-dependent expression to a mouse mammary cell line but failed to induce accurate expression to the mammary gland of transgenic mice. We investigated here the ability of 3.8 kb of the bovine beta-casein gene promoter to drive the expression of the human growth hormone (hGH) gene in transgenic mice. A Northern blot analysis using total RNA obtained from different tissues of lactating and nonlactating females revealed the presence of hGH mRNA only in the mammary gland of lactating females. hGH mRNA was not detectable in the mammary gland of virgin females or males. A developmental analysis showed that hGH mRNA only peaked on parturition, resembling more closely the bovine beta-casein temporal expression pattern rather than the murine. In situ hibridization studies performed on mammary gland sections showed that the cellular pattern of hGH expression was homogeneous in all lobules from heterozygous and homozygous transgenic mice. Silver grain counts on the tissue sections highly correlated with the hGH contents in the milk determined by radioimmunoassay (r = 0.996). Thus 3.8 kb of the bovine beta-casein promoter direct a high-level expression of a reporter gene to the lactating mammary gland of transgenic mice in a tissue-specific and developmentally regulated manner.
β-酪蛋白基因表达的空间、时间和激素模式受到高度调控，且仅限于泌乳期乳腺的上皮细胞。先前的研究表明，牛β-酪蛋白启动子的1.7 kb能够驱动细胞特异性和激素依赖性表达至小鼠乳腺细胞系，但未能在转基因小鼠的乳腺中诱导精确表达。我们在此研究了牛β-酪蛋白基因启动子的3.8 kb驱动人类生长激素（hGH）基因在转基因小鼠中表达的能力。使用从泌乳和非泌乳雌性不同组织获得的总RNA进行的Northern印迹分析显示，仅在泌乳雌性的乳腺中存在hGH mRNA。在未生育雌性或雄性的乳腺中未检测到hGH mRNA。发育分析表明，hGH mRNA仅在分娩时达到峰值，更类似于牛β-酪蛋白的时间表达模式而非小鼠的。对乳腺切片进行的原位杂交研究表明，杂合和纯合转基因小鼠所有小叶中hGH表达的细胞模式是均匀的。组织切片上的银颗粒计数与放射免疫测定法测定的牛奶中hGH含量高度相关（r = 0.996）。因此，牛β-酪蛋白启动子的3.8 kb以组织特异性和发育调控的方式指导报告基因在转基因小鼠泌乳期乳腺中的高水平表达。
