Project description:In the malaria parasite Plasmodium falciparum, the switch that occurs from asexual multiplication to sexual differentiation is essential for transmission to mosquitos. One of the key drivers of commitment to sexual development is the transcription factor AP2-G. Although it has been hypothesised that AP2-G orchestrates this crucial cell fate decision by driving expression of gametocyte genes, the molecular mechanisms by which this occurs remain unknown. We show conclusively that AP2-G is a transcriptional activator of gametocyte genes and identify the earliest target genes expressed during commitment. Remarkably, we also find that in committed cells AP2-G is associated with the promoters of genes important for red blood cell invasion and activates them through its interactions with another transcription factor. We thus demonstrate for the first time an intriguing transcriptional link between the apparently opposing processes of red blood cell invasion and gametocytogenesis. This suggests that committed schizonts may have a distinct invasion preference or pathway that is transcriptionally regulated by AP2-G.
Project description:In the malaria parasite Plasmodium falciparum, the switch from asexual multiplication to sexual differentiation into gametocytes is essential for transmission to mosquitos. One of the key determinants of sexual commitment is the transcription factor PfAP2-G, which has been proposed to orchestrate this crucial cell fate decision by driving expression of gametocyte genes. We show conclusively that PfAP2-G is a transcriptional activator of gametocyte genes and identify the earliest known markers expressed during commitment. Remarkably, we also find that in sexually committed cells, PfAP2-G is associated with the promoters of genes important for red blood cell invasion and activates them through its interactions with a second transcription factor. We thus demonstrate an intriguing transcriptional link between the apparently opposing processes of red blood cell invasion and gametocytogenesis that is coordinated by the master regulator PfAP2-G. This finding has important implications for the development of new anti-malarial drugs that block the invasion of red blood cells by sexually committed cells, thereby preventing parasite transmission.
Project description:Malaria transmission requires the conversion of some asexual parasites into sexual forms termed gametocytes. The initial stages of sexual development, including sexually-committed schizonts and sexual rings, remain poorly characterized, in part because only a subset of parasites undergo sexual development and they are morphologically identical to their asexual counterparts. Here we present a system based on conditional expression of PfAP2-G, the master regulator of sexual conversion, for controlled sexual induction. Induction resulted in ~90% sexual conversion, which enables the characterization of early sexual stages without further purification. Transcriptomic analysis identified the alterations that follow pfap2-g activation, including identification of genes that are down-regulated. We also show that the inducible system enables the characterization of committed stages at the phenotypic level. Altogether, the inducible lines will facilitate the study of the initial stages of sexual development, which is important for the development of new strategies to stop malaria transmission.
Project description:Obligate intracellular parasites must efficiently invade host cells in order to mature and be transmitted. For the malaria parasite Plasmodium falciparum, invasion of host red blood cells (RBCs) is essential. Here we describe a parasite-specific transcription factor belonging to the Apicomplexan Apetala 2 (ApiAP2) family that is responsible for regulating the expression of a subset of merozoite genes involved in RBC invasion (PfAP2-I). Our genome-wide analysis by ChIP-seq shows that PfAP2-I interacts with a specific DNA motif in the promoters of these genes. msp5 transcription levels decrease when the PfAP2-I DNA-binding motif is mutated in PfAP2-I-GFP parasites, showing that PfAP2-I must bind the DNA motif in order for msp5 to be transcribed.
Project description:Obligate intracellular parasites must efficiently invade host cells in order to mature and be transmitted. For the malaria parasite Plasmodium falciparum, invasion of host red blood cells (RBCs) is essential. Here we describe a parasite-specific transcription factor belonging to the Apicomplexan Apetala 2 (ApiAP2) family that is responsible for regulating the expression of a subset of merozoite genes involved in RBC invasion (PfAP2-I). Our genome-wide analysis by ChIP-seq shows that PfAP2-I interacts with a specific DNA motif in the promoters of these genes. msp5 transcription levels decrease when the PfAP2-I DNA-binding motif is mutated in PfAP2-I-GFP parasites, showing that PfAP2-I must bind the DNA motif in order for msp5 to be transcribed.
Project description:In the malaria parasite Plasmodium falciparum, the switch from asexual multiplication to sexual differentiation into gametocytes is essential for transmission to mosquitos. One of the key determinants of sexual commitment is the transcription factor PfAP2-G, which has been proposed to orchestrate this crucial cell fate decision by driving expression of gametocyte genes. Here we identify for the first time the direct targets of PfAP2-G and demonstrate that it dynamically binds hundreds of sites across the genome. We also identify major differences in PfAP2-G occupancy between gametocytes derived via next-cycle and same-cycle conversion, suggesting significant biological differences between these two pathways. By using a combination of ChIP-seq, transcriptomics, and CRISPR-Cas9, we are able to show definitively that PfAP2-G is a transcriptional activator of early gametocyte genes. Our data implicate PfAP2-G not just as a transcriptional activator of gametocyte genes, but also as a regulator of genes important for red blood cell invasion. Excitingly, we also demonstrate that PfAP2-G interacts with a second transcription factor to regulate transcription. These results shed new light on a critical part of the malaria parasite lifecycle by clarifying the role of PfAP2-G during gametocytogenesis.
Project description:Differentiation from asexual blood stages to sexual gametocytes is required for transmission of malaria parasites from the human host to mosquitos, where sexual fertilization occurs to complete the lifecycle. Although preventing gametocyte development would block parasite transmission, the molecular mechanisms underlying sexual commitment and gametocyte maturation are still relatively unknown. Previous studies identified an ApiAP2 protein, AP2-G2, which plays a critical role in gametocyte maturation in rodent malaria parasite Plasmodium berghei by acting as the repressor of asexual stage genes in gametocytes. In this work we characterize the P. falciparum orthologue (PF3D7_1408200) of PbAP2-G2 and report that it plays a critical role in maturation of gametocytes. Disruption of pfap2-g2 did not obstruct commitment to sexual development but the majority of parasites were unable to develop normally beyond stage III gametocytes. In asexual stages PfAP2-G2 binds to the promoters of wide variety of genes expressed in diverse range of parasite’s life cycle stages including gametocytes, mosquito lifecycle stages early ring stage genes and genes encoding for proteins involved in egress and invasion. Surprisingly, we also identify binding of PfAP2-G2 in the gene body of almost 3000 genes. We could also show that PfAP2-G2 interacts with chromatin remodeling proteins and another ApiAP2 protein (PF3D7_1139300) whose motif is also overrepresented in the ChIP-seq data. Overall this work suggests that PfAP2-G2 is a transcriptional regulator that regulates genes possibly by recruiting additional transcription factors and chromatin remodeling machinery and plays a critical role in the development of malaria parasites as they transition from the asexual stage to gametocytes.
Project description:Gametocytogenesis, the process by which malaria parasites produce sexual forms that can infect mosquitoes, is essential for the transmission of malaria. A transcriptional switch of the pfap2-g gene triggers sexual commitment, but how the complex multi-step process is precisely programed remains largely unknown. Here, by systematic functional screening of a panel of ApiAP2 transcription factors, we identify six new apiAP2 members associated with gametocytogenesis in Plasmodium falciparum. Among these, PfAP2-G5 (PF3D7_1139300) was found to be indispensable for gametocytogenesis. This factor suppresses the transcriptional activity of the pfap2-g gene via binding to both the upstream region and exonic gene body, the latter is linked to the maintenance of local heterochromatin structure, thereby preventing initiation of sexual commitment. Removal of this repressive effect through pfap2-g5 knockout disrupts the asexual replication cycle and promotes sexual commitment accompanied by upregulation of pfap2-g expression. However, the gametocytes produced fail to mature fully. Further analyses show that PfAP2-G5 is essential for gametocyte maturation, and causes the down-regulation of pfap2-g and a set of early gametocyte genes activated by PfAP2-G prior to gametocyte development. Collectively, our findings reveal a regulation cascade of gametocyte production in malaria parasites, and provide a new target for transmission blocking interventions.
Project description:Gametocytogenesis, the process by which malaria parasites produce sexual forms that can infect mosquitoes, is essential for the transmission of malaria. A transcriptional switch of the pfap2-g gene triggers sexual commitment, but how the complex multi-step process is precisely programed remains largely unknown. Here, by systematic functional screening of a panel of ApiAP2 transcription factors, we identify six new apiAP2 members associated with gametocytogenesis in Plasmodium falciparum. Among these, PfAP2-G5 (PF3D7_1139300) was found to be indispensable for gametocytogenesis. This factor suppresses the transcriptional activity of the pfap2-g gene via binding to both the upstream region and exonic gene body, the latter is linked to the maintenance of local heterochromatin structure, thereby preventing initiation of sexual commitment. Removal of this repressive effect through pfap2-g5 knockout disrupts the asexual replication cycle and promotes sexual commitment accompanied by upregulation of pfap2-g expression. However, the gametocytes produced fail to mature fully. Further analyses show that PfAP2-G5 is essential for gametocyte maturation, and causes the down-regulation of pfap2-g and a set of early gametocyte genes activated by PfAP2-G prior to gametocyte development. Collectively, our findings reveal a regulation cascade of gametocyte production in malaria parasites, and provide a new target for transmission blocking interventions.