University of Wyoming, Department of Molecular Biology, Laramie 82071, USA.
J Anim Sci. 2012 Feb;90(2):481-8. doi: 10.2527/jas.2011-4034. Epub 2011 Oct 7.
Regulations for the disposal of genetically engineered animals are strict due to concern for their inappropriate introduction into the food chain, and of the possible public health and environmental impacts of these organisms. Nontransgenic animals that give birth to transgenic offspring are treated as if they are transgenic due to concern of fetal cells crossing the placental barrier and residing in the mother (fetal-maternal microchimerism). Determining whether or not fetal-fetal or fetal-maternal transfer of DNA or cells occurs during caprine gestation is critical to effectively protect the public without culling animals that pose no risk. Additionally, fetal-maternal transfer, should it exist in the goat, could contraindicate the rebreeding of nontransgenic dams due to the possible transfer of fetal cells from 1 pregnancy to the fetus of subsequent pregnancies. Fetal-maternal transfer in Capra hircus has not been reported in the literature, although it has been reported in another ruminant, Bos taurus. We examined blood from nontransgenic dams that carried transgenic offspring using a PCR method sensitive enough to detect the presence of a spider silk transgene to a 1:100,000 dilution. At this sensitivity, we did not detect the occurrence of fetal-maternal transfer in 5 nontransgenic dams. Likewise, fetal-fetal transfer was not observed from a transgenic to a nontransgenic twin in utero. To test tissue-specific expression of the silk transgene, proteins purified from standard necropsy tissue from a lactating transgenic dam were examined by Western blot analysis. Silk protein expression was only observed in mammary tissue consistent with the tissue specificity of the β-casein promoter used in the transgenic construct. We report evidence collected from a limited caprine breeding pool against transfer of transgenes in utero from fetus to dam and fetus to fetus. In addition, we show evidence that the β-casein promoter in our expression construct is not expressed ectopically as previously suggested. These results suggest that transgene transfer in utero does not occur, but further study is warranted with a larger sample group to confirm these results.
由于担心基因工程动物被不适当地引入食物链，以及这些生物体可能对公共卫生和环境造成的影响，对其进行处置的规定非常严格。由于担心胎儿细胞穿过胎盘屏障并存在于母体中（胎儿-母体微嵌合体），因此产下转基因后代的非转基因动物会被视为转基因动物。确定山羊妊娠期间是否发生胎儿-胎儿或胎儿-母体的 DNA 或细胞转移对于在不淘汰不存在风险的动物的情况下有效保护公众至关重要。此外，如果山羊存在胎儿-母体转移，由于可能将来自一次妊娠的胎儿细胞转移到随后妊娠的胎儿中，那么可能会禁止非转基因母羊再次繁殖。尽管在另一种反刍动物牛中已有报道，但在绵羊中尚未有胎儿-母体转移的报道。我们使用一种 PCR 方法检查了携带转基因后代的非转基因母羊的血液，该方法足够灵敏，可以检测到蜘蛛丝转基因的存在，灵敏度为 1:100,000 稀释。在这种灵敏度下，我们未在 5 只非转基因母羊中检测到胎儿-母体转移的发生。同样，在子宫内也未观察到从转基因到非转基因双胞胎的胎儿-胎儿转移。为了测试丝蛋白转基因的组织特异性表达，我们通过 Western blot 分析检查了来自哺乳期转基因母羊标准尸检组织中纯化的蛋白质。仅在乳腺组织中观察到丝蛋白表达，与转基因构建体中使用的β-酪蛋白启动子的组织特异性一致。我们报告了从有限的山羊繁殖群体中收集的证据，证明在子宫内从胎儿到母体和从胎儿到胎儿的转基因转移。此外，我们还证明了我们的表达构建体中的β-酪蛋白启动子不会像以前所建议的那样异位表达。这些结果表明，在子宫内不会发生转基因转移，但需要进一步研究更大的样本组来确认这些结果。
