Remobilization of Sleeping Beauty transposons in the germline of Xenopus tropicalis

Transgenic frogs that express the SB10 transposase were bred with SB transposon-harboring animals to yield double-transgenic 'hopper' frogs. Remobilization events were observed in the progeny of the hopper frogs and were verified by Southern blot analysis and cloning of the novel integrations sites. Unlike the co-injection method used to generate founder lines, transgenic remobilization resulted in canonical transposition of the SB transposons. The remobilized SB transposons frequently integrated near the site of the donor locus; approximately 80% re-integrated with 3 Mb of the donor locus, a phenomenon known as 'local hopping'.In this study, we demonstrate that SB transposons integrated into the X. tropicalis genome are effective substrates for excision and re-integration, and that the remobilized transposons are transmitted through the germline. This is an important step in the development of large-scale transposon-mediated gene- and enhancer-trap strategies in this highly tractable developmental model system.Amphibian model systems have provided a wealth of information on the molecular mechanisms controlling early vertebrate development. Frogs of the Xenopus genus are particularly well suited for embryological study as these animals adapt well to captivity and the females can be induced to lay large numbers of eggs throughout the year. The most commonly used amphibian model is the South African clawed frog, X. laevis. Genetic manipulation of this species is not practical due to the long generation time (> 1 year) and the pseudo-tetraploid nature of the genome. Another species of the Xenopus genus, X. tropicalis, shares the embryological advantages of its South African cousin and is better suited for genetic studies as it is a true diploid and has a relatively short generation time (approximately 6 months). The potential of applying modern genetics to this classical embryological model system has resulted in the rapid development of genomic tools for X. tropicalis