nanos-Driven expression of piggyBac transposase induces mobilization of a synthetic autonomous transposon in the malaria vector mosquito, Anopheles stephensi

- A unique transgenic construct allows identification of transposon mobilization events by fluorescent marker detection.
- Endogenously expressed piggyBac transposase mediates rare remobilization of a transgenic construct in An. stephensi.
- Nearly 4 kilobases of the An. stephensi nanos promoter are not sufficient to drive tissue-specific expression of a gene product.

Transposons are a class of selfish DNA elements that can mobilize within a genome. If mobilization is accompanied by an increase in copy number (replicative transposition), the transposon may sweep through a population until it is fixed in all of its interbreeding members. This introgression has been proposed as the basis for drive systems to move genes with desirable phenotypes into target species. One such application would be to use them to move a gene conferring resistance to malaria parasites throughout a population of vector mosquitos. We assessed the feasibility of using the piggyBac transposon as a gene-drive mechanism to distribute anti-malarial transgenes in populations of the malaria vector, Anopheles stephensi. We designed synthetic gene constructs that express the piggyBac transposase in the female germline using the control DNA of the An. stephensi nanos orthologous gene linked to marker genes to monitor inheritance. Two remobilization events were observed with a frequency of one every 23 generations, a rate far below what would be useful to drive anti-pathogen transgenes into wild mosquito populations. We discuss the possibility of optimizing this system and the impetus to do so.

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