nanos gene control DNA mediates developmentally regulated transposition in the yellow fever mosquito Aedes aegypti

Abstract

Transposable elements (TEs) are proposed as a basis for developing drive systems to spread pathogen resistance genes through vector mosquito populations. The use of transcriptional and translational control DNA elements from genes expressed specifically in the insect germ line to mediate transposition offers possibilities for mitigating some of the concerns about transgene behavior in the target vector species and eliminating effects on nontarget organisms. Here, we describe the successful use of the promoter and untranslated regions from the nanos (nos) orthologous gene of the yellow fever mosquito, Aedes aegypti, to control sex-and tissuespecific expression of exogenously derived mariner MosI transposase-encoding DNA. Transgenic mosquitoes expressed transposase mRNA in abundance near or equal to the endogenous nos transcript and exclusively in the female germ cells. In addition, MosI mRNA was deposited in developing oocytes and localized and maintained at the posterior pole during early embryonic development. Importantly, four of five transgenic lines examined were capable of mobilizing a second MosI transgene into the mosquito genome, indicating that functional transposase was being produced. Thus, the nos control sequences show promise as part of a TE-based gene drive system. dengue ͉ gene drive ͉ transposon

Comparative genomics allows the discovery of cis -regulatory elements in mosquitoes

“…Experimental validation of the functionality of each discovered motif and regulatory module is necessary and will provide support for the development of mosquito synthetic promoters that deliver desired and predetermined expression patterns in transgenic mosquitoes. Promoters that direct expression of transgenes specifically to the germ cells would be useful for the development of gene-drive mechanisms for spreading a desired (pathogen-resistance) trait in a mosquito population (47). Gene-specific knockdown or robust expression of exogenous odorant receptors or odorant binding proteins in the antenna of anthropophilic mosquitoes could redirect their preferences toward other animals (48).…”

Gene Expression Studies in Mosquitoes

“…The reasons for this include disruptions of the element structure upon integration , but for those that inserted intact it is not known and likely is specific to the element. Engineered elements based on Mos1 and containing a source of transposase (autonomous) were able to catalyze the chromosomal insertion of other elements carrying Mos1 ITRs, indicating the transcription and translation of functional transposase, but no movement of inserted elements were observed (Adelman et al, 2007). While most nonautonomous transposable elements are stable in the absence of the homologous transposase, it is possible that endogenous sources of transposase may destabilize them.…”

“…While the expression profiles of the nanos and oskar (osk) genes are conserved generally, there are some differences noted in temporal and spatial distribution (Adelman et al, 2007;Goltsev et al, 2004;Juhn and James, 2006). Specifically, while mosquito oskar mRNAs were found to localize to the posterior end in early-stage embryos, An.…”

“…The nos orthologous gene of Ae. aegypti was able to control sex-and tissue-specific expression of exogenously derived MosI transposase-encoding DNA (Adelman et at., 2007). Transgenic mosquitoes expressed transposase mRNA in abundance and exclusively in the female germ cells.…”

Transgenesis, Paratransgenesis and Transmission Blocking Vaccines to Prevent Insect-Borne Diseases

“…aegypti germ line, possibly reflecting a resistance mechanism, since the same elements can remobilize in Drosophila germ line tissues (O'Brochta et al 2003). In addition, a mechanism to drive transposase expression and restrict gene drive system activity to germ-line tissues has been created using the regulatory sequence of nanos, a gene involved in early embryonic development (Adelman et al 2007). …”