Shamay A, Pursel V G, Wall R J, Hennighausen L
Laboratory of Biochemistry and Metabolism, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of health, Bethesda, Maryland 20892.
Mol Endocrinol. 1992 Feb;6(2):191-7. doi: 10.1210/mend.6.2.1569963.
Five month-old transgenic female pigs from three lines carrying the mouse whey acidic protein (WAP) gene and nontransgenic female littermates were implanted with slow-release estrogen and progesterone pellets. Histological analysis of biopsies taken at the time of implantation and 4 weeks later revealed that mammary alveolar development had occurred upon hormonal stimulation in vivo. beta-Casein and beta-lactoglobulin mRNA was found in all induced animals, and WAP mRNA was detected in two of the three transgenic pigs. Differential hormonal regulation between the transgenes in the three lines and also between endogenous milk protein genes was observed in induced mammary tissue cultured in vitro. In the presence of insulin, hydrocortisone, and PRL, beta-casein and WAP mRNA levels increased in all transgenic pigs. In contrast, beta-lactoglobulin mRNA had reached or exceeded lactational levels in response to the in vivo induction, and no further increase was observed in vitro. This suggests that the regulation of the beta-lactoglobulin gene is distinct from that of beta-casein and WAP. Differences were also observed during pregnancy; whereas beta-lactoglobulin gene expression was induced in early pregnancy, a time when PRL levels are low, WAP mRNA levels increased sharply around parturition. Finally, the observation that hormonal regulation of WAP transgenes greatly differed between the three lines suggests that chromatin surrounding the integration site can modify the response of transcription elements.
对来自三个携带小鼠乳清酸性蛋白（WAP）基因品系的5月龄转基因雌性猪及其非转基因雌性同窝仔猪植入缓释雌激素和孕酮丸剂。在植入时及4周后采集活检组织进行组织学分析，结果显示在体内激素刺激下乳腺腺泡已发育。在所有诱导动物中均发现了β-酪蛋白和β-乳球蛋白mRNA，在三只转基因猪中的两只检测到了WAP mRNA。在体外培养的诱导乳腺组织中，观察到三个品系的转基因之间以及内源性乳蛋白基因之间存在不同的激素调节。在胰岛素、氢化可的松和催乳素存在的情况下，所有转基因猪的β-酪蛋白和WAP mRNA水平均升高。相比之下，β-乳球蛋白mRNA在体内诱导后已达到或超过泌乳水平，在体外未观察到进一步升高。这表明β-乳球蛋白基因的调节与β-酪蛋白和WAP不同。在妊娠期间也观察到了差异；β-乳球蛋白基因表达在妊娠早期被诱导，此时催乳素水平较低，而WAP mRNA水平在分娩前后急剧升高。最后，三个品系之间WAP转基因的激素调节存在很大差异这一观察结果表明，整合位点周围的染色质可以改变转录元件的反应。
