Histone methylation during Plasmodium falciparum sexual differentiation

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Sequencing of the genome of the human malaria parasite Plasmodium falciparum in the year 2002 fueled the hope for the discovery of novel drug and vaccine targets. In the following years, transcriptomics and proteomics helped to assign these genes to the distinct parasite stages and allowed a first glimpse on the tightly regulated transcriptional programme required for life-cycle progression. Since then increasing evidence points to a strong contribution of epigenetics to gene regulation in Plasmodium with particular emphasis on histone post-translational modifications regulating the erythrocytic replication phase. It is not yet well understood, though, which role histone modifications play, when the parasites need to prepare for transmission from the human to the mosquito. Responsible for parasite transmission are the gametocytes, which sexually differentiate in human red blood cells and, once being taken up by a blood-feeding Anopheles mosquito, enter gametogenesis to initiate sexual reproduction. During gametocyte development and following gametogenesis, different repertoires of genes are switched on and off in a well-coordinated sequence, pointing to a strict regulation of gene expression. We recently demonstrated a crucial role of histone modifications during transcriptional control in the developing gametocytes. While histone deacetylation silences genes related to the asexual blood and mosquito-specific stages, histone acetylation activates genes important for gametogenesis. Additionally, chemical inhibition of lysine-specific histone methyltransferases points to a pivotal role of plasmodial SET-domain proteins during gametocyte induction and gametogenesis. The exact functions of the SET proteins for gametocyte development, however, are not yet known. It is thus the overarching goal of this proposal to investigate the mechanisms of transcriptional regulation by histone methylation during P. falciparum sexual differentiation. To follow this goal, we will functionally characterize the gametocyte-specific histone methyltransferases SET2 and SET10 via gene-knockout followed by comparative transcriptomics (aim 1). Further, interactors of SET2 and SET10 will be unveiled by biotin proximity labelling identification, while chromosome regions affected by SET2 and SET10 will be identified by chromatin immunoprecipitation (aim 2). Additionally, the involvement of the yet under-investigated S-adenosylmethionine synthetase SAMS, a key regulator of methylation reactions, during the transcriptional control in gametocytes will be analysed, using gene-knockdown followed by biochemical and RNA sequencing approaches (aim 3). Data gained by this study will provide novel insights into histone methylations during sexual differentiation of the malaria parasite and will promote the evaluation of epigenetic regulators and effectors as antimalarial targets.