Molecular Genetics and Genomics of the Meiotic Drive System in Aedes aegypti

Population replacement strategies for mosquito-borne disease transmission control require spreading anti-pathogen effector genes into vector populations. Effective large-scale population replacement strategies will require development of reliable mechanisms for the biological introgression of the effector gene. Meiotic drive is the process that causes one gamete type to be under or over represented following gamete formation during meiosis and has potential as a tool to drive novel genes into feral populations. However, the genetic basis for its effects has not been investigated. Therefore, we need to understand the molecular mechanisms for meiotic drive.

My first aim was to investigate the meiotic drive system of Ae. aegypti-specific cDNA expression profiles. cDNA libraries were prepared from testes from an aegypti meiotic drive carrying strain (T37) and a strain sensitive to the driver (RED), and I then used suppression subtraction hybridization techniques to enrich for meiotic drive carrying testes-specific transcripts. Primary libraries showed tissue-, stage- specific gene expression such as reproduction and larval development while the subT37 transcripts were associated with signal transduction, development, reproduction, metabolic process and cell cycle functions. Further, as observed with meiotic drive systems in Drosophila and mouse, a number of these genes were associated with signaling cascades that involve the Ras superfamily of regulatory small GTPases.

The second aim describes genetic mapping of the meiotic drive gene. About 5% of the backcross population showed a normal sex ratio (P<0.05). Four markers showed inheritable codominant in the family. The meiotic drive gene is mapped on chromosome 1, flanking SSCP marker (LF159) and microsatellite marker (446GAA). The D locus maps 6.5cM and the 4 markers span 16.5 cM. The order of the markers and the genetic distance are in agreement with the well known composite map. The third aim in this dissertation describes mapping transcripts statistically significant for T37 expression, based on whole transcriptome microarray analysis, to pathways by gene function and subsequent construction of gene networks. Apoptosis and immune response pathways were highly ranked in this study. Because the meiotic drive gene is located on chromosome 1, genes located on known genome scaffolds for chromosomes 2 and 3 were excluded from detailed analysis. According to the pathway analysis, chromosome 1 enriched genes were selected and validated by qRT-PCR.