Transformation of frog embryos with a rabbit beta-globin gene.

Abstract

To study the fate and possible expression of foreign DNA during embryogenesis of the frog X. laevis, a rabbit .beta.-globin gene was injected 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. 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. The 6-wk-old tadpoles and 6-mo.-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 MW 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.