Detection of de novo insertion of the medaka fish transposable element Tol2

Tol2 is a terminal-inverted-repeat transposable clement of the medaka fish Oryzias latipes. It is a member of the hAT (hobo/Activator/Tam3) transposab le element family that is distributed in a wide range of organisms. We here document direct evidence for de novo insertion of this element. A Tol2 clo ne marked with the bacterial tetracycline-resistance gene was microinjected into fertilized eggs together with a target plasmid, and the plasmid was r ecovered from embryos. The screening of plasmid molecules after transformat ion into Escherichia coli demonstrated transposition of tet into the plasmi d and, by inference, precise insertion of Tol2 in medaka fish cells. De nov o excision of Tol2 has previously been demonstrated. The present study prov ides direct evidence that the Tol2 element has the entire activity necessar y for cut-and-paste transposition. Some elements of the mariner/Tcl family, another widespread group, have already been applied to development of gene tagging systems in vertebrates. The Tol2 element of the hAT family, hating different features from mariner/Tcl family elements, also has potential as an alternative gene tagging tool in vertebrates.