A Forward Genetic Screen Identifies Genes Involved in Gametocyte Development of the Human Malaria Parasite Plasmodium falciparum.

Transmission of the deadly malaria parasite Plasmodium falciparum from human to mosquito is achieved by specialized intraerythrocytic sexual forms called gametocytes. Circulating in the vertebrate host, relatively few intraerythrocytic gametocytes are picked up during a bloodmeal to continue sexual development in the mosquito vector. Human-to-vector transmission thus represents an infection bottleneck in the parasite's life cycle for therapeutic interventions to prevent malaria. Though the crucial regulatory mechanisms leading to gametocyte commitment have recently come to light, networks of genes that control sexual development remain to be elucidated. Here, we report a forward genetic approach to identify genes associated with gametocyte development in P. falciparum. This innovative approach involves the development of a high-throughput phenotypic screening strategy and evaluation of its scalability by using two piggyBac-transposon mutant libraries with 128 and 600 unique mutants, respectively. The results categorized genes that modulate gametocyte progression as hypo- or hyper-producers of gametocytes, and the in-depth analysis of individual clones confirmed phenotypes in sexual commitment rates and putative functions in gametocyte development. These genes are characterized further for their expression patterns, GO pathways, evolutionary conservation in other Plasmodium species and other identifiable features. A new set of genes that have not been previously implicated in gametocytogenesis are presented to demonstrate the potential of forward genetic screens in unravelling parasite sexual biology – an exciting step towards the discovery of new antimalarials for a globally significant pathogen.