Project description:Commitment to and completion of sexual development are essential for malaria parasites to be transmitted through mosquitoes. The molecular mechanism(s) responsible for these processes however, remain largely unknown. We have identified two transcription factors (both belonging to the AP2 family) essential for gametocytogenesis. AP2-G mutants are characterised by a complete inability to produce gametocytes. In AP2-G2 mutants the gametocytaemia is very significantly reduced but not completely abolished. We have performed the microarray experiments in order to cokmpare the transcriptomes of these mutantnts to the WT parasites and between each other. As P.berghei parasites are characterised by asynchronous development in the rodent host, the different stage composition of the sample would impact the analysis. Therefore parasites were harvested and matured in in vitro to the schizont stage
Project description:During the malaria infection, Plasmodium parasites invade the host’s red blood cells where they can differentiate into two different life forms. The majority will replicate asexually and infect new erythrocytes. A small percentage, however, will transform into gametocytes – a specialized sexual stage able to survive and develop when taken up by Anopheles mosquito. As the gametocytes ensure the parasite’s transmission to a new host, their generation is an attractive target for new antimalarial interventions. The molecular mechanisms controlling gametocytogenesis, however, remain largely unknown due to the technical challenges: the early gametocytes are morphologically indistinguishable from asexual parasites and present in very low numbers during the infection. Recently, AP2-G - a transcription factor from an apicomplexa-specific apiAP2 family – was described as indispensable for gametocyte commitment in both human malaria parasite Plasmodium falciparum and rodent malaria model Plasmodium berghei. Therefore, we have decided to test whether the overexpression of this factor alone could increase gametocyte production and enable the investigation of uncharacterised, earliest stages of gametocyte development. To this end, we have engineered PBGAMi - a Plasmodium berghei line, in which all parasites were ap2-g deficient by default but able to overexpress it when induced with rapamycin. While the control parasites (PBGAMi R-), as expected, differentiated into asexual forms (schizonts) only, almost all rapamycin-treated parasites (PBGAMi R+) transformed into gametocytes. We used the generated line to perform RNA-seq analysis of the R- and R+ populations at different time points of their development and identify the changes arising between them, mapping the sequence of events leading to the formation of gametocytes.
Project description:The family of apicomplexa-specific proteins with DNA binding AP2 domains (ApiAP2s) includes sequence-specific transcription factors that are key regulators of development in malaria parasites. However, functions for the majority of ApiAP2 genes remain unknown. Here, a systematic knockout screen in Plasmodium berghei identifies ten ApiAP2 genes essential for mosquito transmission, of which four are critical for the formation of infectious ookinetes and three for sporogony. We describe unexpected non-essential functions for AP2-O and AP2-SP proteins in blood stages and identify AP2-G2 as a universal repressor active in both, asexual and sexual stages. Comparative transcriptomics across mutants and developmental stages reveals clusters of co-regulated genes with shared cis elements in their promoters, whose expression can be controlled positively or negatively by different ApiAP2 gene deletions. We propose that stage-specific interactions between ApiAP2 proteins on partly overlapping sets of target genes generate the complex transcriptional network that controls the Plasmodium life cycle.
Project description:During the malaria infection, Plasmodium parasites invade the host’s red blood cells where they can differentiate into two different life forms. The majority will replicate asexually and infect new erythrocytes. A small percentage, however, will transform into gametocytes – a specialized sexual stage able to survive and develop when taken up by Anopheles mosquito. As the gametocytes ensure the parasite’s transmission to a new host, their generation is an attractive target for new antimalarial interventions. The molecular mechanisms controlling gametocytogenesis, however, remain largely unknown due to the technical challenges: the early gametocytes are morphologically indistinguishable from asexual parasites and present in very low numbers during the infection. Recently, AP2-G - a transcription factor from an apicomplexa-specific apiAP2 family – was described as indispensable for gametocyte commitment in both human malaria parasite Plasmodium falciparum and rodent malaria model Plasmodium berghei. Therefore, we have decided to test whether the overexpression of this factor alone could increase gametocyte production and enable the investigation of uncharacterised, earliest stages of gametocyte development. To this end, we have engineered PBGAMi - a Plasmodium berghei line, in which all parasites were ap2-g deficient by default but able to overexpress it when induced with rapamycin. While the control parasites (PBGAMi R-), as expected, differentiated into asexual forms (schizonts) only, almost all rapamycin-treated parasites (PBGAMi R+) transformed into gametocytes. We used the generated line to perform RNA-seq analysis of the R- and R+ populations at different time points of their development and identify the changes arising between them, mapping the sequence of events leading to the formation of gametocytes. At the same time we have generated purified transcriptomes of male and female gametocytes for the reference
Project description:Commitment to and completion of sexual development are essential for malaria parasites to be transmitted through mosquitoes. The molecular mechanism(s) responsible for these processes however, remain largely unknown. We have identified two transcription factors (both belonging to the AP2 family) essential for gametocytogenesis. AP2-G mutants are characterised by a complete inability to produce gametocytes. In AP2-G2 mutants the gametocytaemia is very significantly reduced but not completely abolished. We have performed the microarray experiments in order to cokmpare the transcriptomes of these mutantnts to the WT parasites and between each other. As P.berghei parasites are characterised by asynchronous development in the rodent host, the different stage composition of the sample would impact the analysis. Therefore parasites were harvested and matured in in vitro to the schizont stage Pairwaise comparison between the mutants and parental line was performed. 3 biological replicates of each condition were used.
Project description:Sporozoite-specific genes were induced in parasites that express AP2-O whose AP2 domain was swapped with that of AP2-Sp. DNA construct encoding AP2 domain of AP2-Sp was introduced into P. bergei schizonts. It was integrated into the locus of the endogenious AP2-O gene, resulting in swap of the AP2-domain (AP2-O::Sp parasites). Gene expression was analyzed in ookinetes cultured for 20h.
Project description:Gametocytes are nonreplicative sexual forms that mediate malaria transmission to a mosquito vector. They are generated from asexual blood stage parasites, which proliferate in the circulation. However, it remains largely unknown as to how this transition is genetically regulated. Here, we report that an Apetala2 (AP2) family transcription factor, AP2-G2, regulates the transition as a transcriptional repressor. Disruption of AP2-G2 in the rodent malaria parasites, Plasmodium berghei, did not prevent commitment to the sexual stage but halted their development before manifesting sex-specific morphologies. ChIP-seq analysis revealed that AP2-G2 targets approximately 1,500 genes and recognizes a five-base motif on their promoters. Most of these target genes are required for asexual proliferation in the blood by the parasites, thereby suggesting that AP2-G2 blocks the program for asexual replication of parasites in the blood. DNA microarray analysis showed that the identified targets constituted approximately 70% of the upregulated genes in AP2-G2-depleted parasites, and a promoter assay using a centromere plasmid demonstrated that the binding motif functions as a cis-acting negative regulatory element. These results suggest that global transcriptional repression, which occurs during the initial phase of gametocytogenesis, is an essential step to promote conversion to the sexual stage.