The jump starter transposon system in zebrafish: heat-inducible transposition of a single integrated Tol2 can create genome-wide insertions.

Akihiro Urasaki, Kazuhide Asakawa and Koich Kawakami

National Institute of Genetics, Molecular and Developmental Biology

 We have been developing the gene and enhancer trap methods using the Tol2 transposon, and creating transgenic zebrafish expressing GFP in specific tissues and organs. Currently we are making transposon insertions in the genome by microinjection of both a transposon-donor plasmid and the transposase mRNA into fertilized eggs. Creating a number of zebrafish lines with different transposon insertions would be easier if the jump starter system, which can create new transposon insertions without microinjection, was developed. Here we report an inducible transposition system by using Tol2 in zebrafish. We constructed transgenic fish carrying the transposase cDNA under the control of the zebrafish hsp70 promoter. The transgenic fish was crossed with a fish line carrying a single copy of the Tol2 enhancer trap construct in the genome. The double transgenic adult fish was heat-shocked, and their offspring were screened for new patterns. We found that, in the germ cells of the heat-shocked fish, transposition events occurred at very high frequencies and the germ cells became highly mosaic. F1 embryos from these fish exhibited different patterns and contained transposon insertions at different loci from the original locus. Unlike other transposon systems, in most cases the new integration sites were found on different chromosomes. Our jump starter system should be useful to create new transposon insertions in the zebrafish genome efficiently.