Transient Transgenesis in Xenopus laevis Facilitated by AAV-ITRs

A common approach to the study of gene function in Xenopus embryos is to ectopically express the gene of interest, or a mutant of that gene, by injecting either RNA or DNA, encoding the gene into early-stage embryos. Both of these approaches have disadvantages (1 ). RNA injection results in little temporal or spatial control, as the RNA begins to be translated immediately following injection. In addition, RNA is unstable; therefore, transgene expression is relatively transient. In principle, DNA injections could ameliorate these problems. DNA does not begin to be translated until embryonic stage 8, at the mid-blastula transition, when zygotic genes begin to be expressed. Promoters can be utilized, which should enable more spatial and temporal control of gene expression, and DNA is more stable than RNA, prolonging the time frame in which transgenes can be expressed. However, for reasons that are not clear, expression of DNA plasmids following direct injection into embryos is extremely mosaic, and tissue specificity of promoters is often lost.