Rusconi S, Schaffner W
Proc Natl Acad Sci U S A. 1981 Aug;78(8):5051-5. doi: 10.1073/pnas.78.8.5051.
In order to study the fate and possible expression of foreign DNA during embryogenesis of the frog Xenopus laevis, we have injected a rabbit beta-globin gene into fertilized Xenopus eggs. Frog embryo DNA was extracted at various stages of development, fractionated by agarose gel electrophoresis, transferred to nitrocellulose filters, and hybridized to labeled beta-globin recombinant plasmid DNA. It was found that the injected DNA replicated extrachromosomally, reaching, at gastrula stage, a level equivalent to a 10- to 200-fold amplification of input DNA. At later stages, a majority of the foreign DNA was degraded, but a small fraction was maintained. Six-week-old tadpoles as well as six-month-old frogs contained an average of 3-10 copies of the rabbit globin gene per cell. Most of these persisting globin genes were present as long tandem repeats and comigrated in agarose gel electrophoresis with high molecular weight Xenopus DNA. Analysis of globin gene expression by S1 nuclease mapping showed that the rabbit beta-globin promoter was recognized in the frog embryo and that the transcripts were correctly spliced.
为了研究非洲爪蟾胚胎发育过程中外源DNA的命运及可能的表达情况，我们将兔β-珠蛋白基因注入非洲爪蟾的受精卵中。在不同发育阶段提取蛙胚胎DNA，通过琼脂糖凝胶电泳进行分离，转移至硝酸纤维素滤膜上，然后与标记的β-珠蛋白重组质粒DNA杂交。结果发现，注入的DNA在染色体外复制，在原肠胚阶段达到相当于输入DNA 10至200倍扩增的水平。在随后的阶段，大部分外源DNA被降解，但仍有一小部分得以保留。六周龄的蝌蚪以及六个月龄的蛙每个细胞平均含有3至10个兔珠蛋白基因拷贝。这些持续存在的珠蛋白基因大多以长串联重复形式存在，在琼脂糖凝胶电泳中与高分子量的非洲爪蟾DNA共迁移。通过S1核酸酶图谱分析珠蛋白基因的表达情况表明，兔β-珠蛋白启动子在蛙胚胎中被识别，并且转录本能够正确剪接。
