| Samenvatting: | <p><em>Aedes aegypti</em> is one of the most important mosquito vectors of human disease, transmitting dengue, Chikungunya and yellow fever viruses. New control methods are much needed for this species and an ability to skew sex ratios toward males would be very useful for a number of strategies. In this study, male-specific chromosomal regions were searched for in <em>Ae. aegypti</em> using novel approaches such as microdissection of chromosomes. The sex determination pathway of <em>Ae. aegypti</em> was also explored, using Drosophila melanogaster as a model, to find candidate genes that could be used to induce male biased sex ratios. The <em>transformer-2 (tra-2)</em> gene is necessary for sexual differentiation of females in <em>D. melanogaster</em>, but its role remains unknown in mosquitoes. A homolog of tra-2 was identified in <em>Ae. aegypti</em>. Rapid Amplification of cDNA ends (RACE) experiments were conducted to characterize this gene in <em>Ae. aegypti</em>. The <em>Ae. aegypti tra-2</em> gene, as for D. melanogaster, was highly variable in transcription due to alternative splicing and alternative polyadenylation, with 9 different variants identified. RNA interference (RNAi) was then used to determine if knockdown of all variants of <em>Ae. aegypti tra-2</em> can be achieved and if it would cause gender switching in individuals, initially by means of direct injection of double stranded RNA, and then progressing to germline transformation. A construct designed to produce <em>tra-2</em> dsRNA was injected into <em>Ae. aegypti</em> embryos and integrated into the <em>Ae. aegypti</em> genome. The transgenic population showed up to 100% male bias in single pair crosses. The male bias effect could still be seen in the heterozygous population. The results suggest that knockdown of <em>tra-2</em> could provide a useful tool for sex ratio distortion as part of the development of novel control methods for <em>Ae. aegypti</em>.</p>
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