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Sex in malaria parasites – from basic biology to targets for transmission blocking interventions.

Periodic Reporting for period 2 - SEXinMALARIA (Sex in malaria parasites – from basic biology to targets for transmission blocking interventions.)

Reporting period: 2020-03-01 to 2021-08-31

Sexual development in malaria parasites is critical for disease 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.
We have so far completed the initial, genome scale knock-out screen proposed in Aim 1, which identified 471 fertility genes at the chosen stringency of the analysis. This part of the project has been completed entirely by the ERC funded team in our new laboratories at Umeå University, demonstrating that despite setbacks caused by the pandemic, we are now fully operational in our new environment. Validation of candidate genes as described in Aim 4 is ongoing. A sub-screen for gametocyte formation has identified candidate genes for sex ratio determination and male and female gametocyte differentiation (Aim 2). The sex-ratio regulators have been validated (Aim 4) and are now studied in depth to discover new biological mechanisms. Additional sub-screens described in Aim 2 are in progress: one screen for male egress and male motility have already yielded interesting insights into specific biological processes required for male fertility during malaria transmission. Candidate genes for new gamete interaction mechanisms that may provide transmission-blocking vaccine targets have been selected for further study.
The project has begun to identify many new genes and biological pathways that are critical to malaria transmission by mosquitoes.