Sex determination in mosquitoes

What determines whether a mosquito develops as a male or a female is largely unknown. This question is not just an academic curiosity. Only female mosquitoes feed on vertebrate blood and hence are capable of transmitting disease. And the variety of diseases transmitted by mosquitoes is staggering. This proposal focuses on the Anopheles mosquitoes that transmit malaria but mosquitoes also transmit a number or incurable viruses as well as a number of severe parasitic diseases of humans and animals. We will use a variety or approaches to disclose the processes that trigger the sex development of Anopheles mosquitoes. We have already identified one gene, doublesex, which switches on a different chain of events in males and females. Based on studies in other insects, and our own preliminary data, we believe that this gene is a key regulator of sexual differentiation. In this proposal we will use doublesex as an anchor to identify steps upstream and downstream of the sex differentiation pathway and thereby begin to build a picture of the sex determination process in mosquitoes. We believe that this pathway will prove to be a rich source of targets for novel mosquito intervention strategies.

This project will identify steps in the pathway of sexual differentiation in Anopheles mosquitoes. There is an extraordinary amount of variation in the sex determination pathways of invertebrates which largely prevents us from extrapolating from the elaborate studies which have already been conducted in model organisms such as Drosophila. We are specifically interested in elucidating the details of this pathway in Anopheles because of the opportunities that perturbing this pathway have for mosquito control. In general a primary signal, which in the case of Anopheles mosquitoes is on the Y chromosome, leads to the differential expression of a key gene, which in turn regulates the splicing of a number of subordinate regulatory genes which finally translate the molecular signal to differences in the phenotype of male and female mosquitoes. We have identified the terminal regulatory gene, doublesex (dsx), which is differentially spliced in males and females, but as yet we do not know how this gene is regulated or what the targets of this transcription factor are. This proposal will address these deficiencies in our understanding of sexual differentiation in mosquitoes. We will identify the splicing factors that determine the sex-specific splicing of the dsx mRNA and use chromosome hybridisation, supported by bioinformatics and functional validation, to identify genes regulated by dsx. We will also use a 'pull-down' approach to identify any additional co-factors that may be acting in parallel with the DSX protein.