Mobility of the piggyBac transposable element in non-host embryos and its use as a germ line vector

The piggyBac element is a Class II DNA transposing element. It was first identified as a mutagenic agent of Autographa californica and Galleria melonella nuclear polyhedrosis virus passaged in the TN-368 Trichoplusia ni insect cell line. The element is 2476 bp long with 13 bp inverted terminal repeats and 19 bp internal repeats asymmetrically distributed with respect to the ends. The transposon has a single ORF, producing a 2.1 kB transcript encoding a 68 kD transposase protein essential for mobilization. A characteristic feature of piggyBac transposition is that it preferentially inserts at a TTAA-tetranucleotide sequence, duplicating it on insertion and precisely regenerates the original TTAA sequence on excision.; Plasmid-based excision and interplasmid transposition assays demonstrate that mobility is not restricted to the T. ni host. Transposase dependent excision events as well as interplasmid transposition events were recovered from embryos of the Lepidopteran T. ni and Plodia interpunctella, as well as the Dipterans Aedes aegypti , Ae. albopictus, Ae. triseriatus and Drosophila melanogaster. piggyBac's capacity to mobilize was not restricted to insects. Interplasmid transposition events were recovered in the vertebrate COS-7 cell line and in embryos of the zebrafish, Danio rerio, demonstrating that the element can transpose across phyla. The piggyBac element was used to vector a wildtype copy of the D. melanogaster cinnabar gene into the germ line of the khw strain of Ae. aegypti. Transformed mosquitoes were recovered at a frequency of 13.0%, with multiple insertions in each transformant. Southern Analysis and inverse gene amplificatons confirmed that transformants obtained in lines I, II and III contained piggyBac insertions at TTAA tetranucleotides, characteristic of piggyBac insertion events.; This element seems to be exceptionally mobile and may be used in the field of insect transgenesis. The piggyBac transposable element stands out as being a remarkably versatile and useful germ line vector.