Identifying the regulators of gene expression during mosquito reproduction

Mosquito-borne diseases have reached catastrophic proportions. The yellow fever mosquito, Aedes aegypti, is the major vector of devastating Arboviral diseases such as that is yellow fever, dengue, chikungunya, and, most recently, Zika. Anautogenous female mosquitoes require nutritional amino acids in vertebrate blood for vitellogenesis, the process of yolk formation during maturation of their eggs - one of the most important events in the mosquito reproductive cycle. It is during blood feeding that the female mosquitoes ingest and transmit the disease pathogens.

            The fat body, which is a multifunctional metabolic organ analogous to the vertebrate liver and adipose tissue, is central in vitellogenesis producing yolk protein precursors. To understand the gene regulation in this tissue during vitellogenesis, we conducted transcriptomic microarray analyses that revealed a previously unrecognized complexity of gene expression and regulation. Further tests have revealed that our gene clusters are differentially expressed and regulated by activating and repressive actions of amino acids, ecdysone receptor, nuclear hormone receptor HR3 and the juvenile hormone receptor Methoprene-tolerant. To further dissect the regulatory complexity underlying the regulatory mechanisms governing the Aedes aegypti reproduction, we have used multiple bioinformatics tools and techniques. We searched the non-coding regulatory regions of the differentially regulated, co-expressed genes, for identification of cis-regulatory elements. 105 putative transcription factor binding sites (TFBSs), have been identified, most of which are cluster specific. We also looked for the primary features associated with real TFBSs, such as, positional and orientation bias and evolutionary conservation. More than thirty Transcription factors (TFs) related to these TFBSs have also been identified using the JASPAR database. Cluster-specific regulatory networks have been built with these TFs. Ongoing study involving RNAi of selected TFs have confirmed their involvement in the regulation of the co-expressed gene sets during the various time points in the vitellogenic period. We are in the process of deciphering their relation to the major regulators with regards to the regulation of gene expression during mosquito reproduction. This study should provide a better understanding of the complex gene regulatory networks through which the two principal insect hormones, 20-hydroxyecdysone and juvenile hormone, regulate the expression of genes involved in reproduction of female Aedes aegypti.