H3K36 Methylation Reprograms Gene Expression to Drive Early Gametocyte Development in Plasmodium Falciparum

Abstract

Background: The Plasmodium sexual gametocyte stages are the only transmissible form of the malaria parasite and are thus responsible for the continued transmission of the disease. Gametocytes undergo extensive functional and morphological changes from commitment to maturity, directed by an equally extensive control program. Several interconnected mechanisms governing sexual commitment have been described. However, the processes that drive the subsequent differentiation and development of the gametocyte remain largely unexplored. Using chromatin immunoprecipitation followed by high-throughput sequencing we describe an association between H3K36 di- and tri-methylation (H3K36me2&3) and the global changes in the transcriptional program driving gametocyte development post-commitment. Results: Here, we show that in stage II gametocytes, H3K36me2&3 are associated with an active repression of genes involved in asexual proliferation and sexual commitment, linking H3K36me2&3 to the transition from early gametocyte differentiation to intermediate development. Specifically, we establish a link between H3K36me2&3 and the repression of genes that are upregulated during commitment once terminal differentiation renders their protein products obsolete in developing gametocytes, thereby securing an appropriate transcriptional environment for intermediate gametocyte development. Lastly, we associate the enhanced potency of JIB-04 in gametocytes with the inhibition of H3K36me2&3 demethylation and a disruption of normal transcriptional programs.Conclusions: Taken together, our results provide the first description of an association between global gene expression reprogramming and histone post-translational modifications during P. falciparum sexual development. In addition to fulfilling the same role in virulence gene regulation as in asexual parasites, the stage II gametocyte-specific abundance of H3K36me2/3 manifests as a largely interdependent enrichment of the two modifications targeted towards genes whose functions become obsolete in post-commitment gametocytes. This contrasts with the broad repression associated with wide-spread H3K36me2 occupancy in asexual parasites, highlighting H3K36me2/3 enrichment as a marker of directed transcriptional repression specific to early gametocytes. The importance of such histone methylation during gametocyte development is underscored by the transcriptional disruption associated with histone demethylase inhibition in P. falciparum gametocytes. By demonstrating the participation of H3K36me2&3 in gametocyte development, we provide a more thorough understanding of the link between epigenetic mechanisms and gene expression in the transmissible stages of the malaria parasite.