Sexual development in malaria parasites is critical for parasite transmission between infected individuals, and is therefore a major target for the malaria elimination agenda. However, there are currently no effective drugs or vaccines that block parasite transmission to mosquitoes, and we currently do not understand the molecular mechanisms involved. This is primarily because Plasmodium genetics has been slow, with the majority of the genome unexplored. I here propose to conduct the first genome-scale screen for male and/or female fertility genes by leveraging a game-changing genetic system we have developed and recently validated through the first genome-scale in vivo gene KO screen in any parasite. Using simultaneous phenotyping of barcoded mutants, we will conduct the first genome-scale screen for male and/or female fertility genes. My team will systematically map specific biological roles for hundreds of parasite genes, ranging from sex determination to zygote differentiation. We will also overcome the next hurdle in Plasmodium genetics by developing a method for massive parallel phenotyping, using the power of single cell transcriptomics to validate the screen and reveal molecular mechanisms at previously intractable points in the Plasmodium life cycle. This approach has clear translational implications, as it will identify both drug and vaccine candidates.Sexual development in malaria parasites is critical for parasite transmission between infected individuals, and is therefore a major target for the malaria elimination agenda. However, there are currently no effective drugs or vaccines in use that block parasite transmission to mosquitoes, and we have a poor understanding of the molecular mechanisms involved. This is primarily because Plasmodium genetics has been slow, with the majority of the genome unexplored.
In this project we have devised a method to mutagenise parasite genes systematically and at genome scale in either the male or the female sexual precursor stage, to ask which parasite genes are needed for each sex to infect the mosquito. Through this approach we managed to identify 471 sex specific gene functions and evaluate their importance for male and female fertility separately.
We validate the data by looking in depth at a small number of selected gene functions and verify the robustness of the screen data. We also created a public database to integreat the screen data with phenotype and gene expression data from earlier genome scale experiments. We have stratified male fertility genes further to distinguish those acting before gametocyte egress from the erythrocyte and those that act after microgametes have become motile. The latter group contains potential new gamete fusion factors that may serve as transmission blocking vaccine candidates. Overall, the screens reveal deep insights into the metabolic reorganisation of a malaria parasite, identifies new regulatory and structural elements of the cell cycle and provide an improved understanding of the evolution of sexual processes in eukaryotes.
