Deciphering the molecular mechanism of erythropoiesis inhibition induced by malaria parasites – ERYMAP

Severe anemia is a common complication of malaria that is associated with increased mortality and morbidity. Malarial anemia is thought to be caused by hemolysis and splenic clearance of red blood cells (RBC), however a dysfunction of the process of erythropoiesis is also observed in patients and is likely to contribute to their anemia. Deciphering the molecular mechanisms by which malaria parasites can interfere with normal erythropoiesis is therefore crucial to identify novel predictive biomarkers and to develop efficient therapeutic strategies. Recent data from Team 1, obtained by ex vivo culture of human primary erythroblasts, indicate that erythropoiesis is impacted by two mechanisms: i) infection of mature erythroblasts by malaria sexual parasites (gametocytes) and ii) production of extracellular vesicles derived from Plasmodium-infected red blood cells (iEVs), which can affect erythroblasts at all stages of their maturation. A pilot proteomic analysis indicated that incubation of erythroblasts with iEVs triggers a decrease of key molecular players in the regulation of normal erythropoiesis, including the major erythroid-specific transcription factor GATA1 and the mechanosensitive channel PIEZO1. The exact contribution of these factors to erythropoiesis defects together with the identity of the parasite-induced factors affecting erythropoiesis remain to be determined.
The ultimate goal of ‘ERYMAP’ is to understand how malaria parasites impair erythropoiesis. The first objective is to better characterize the impact of the parasites on erythroblast development and signaling. We will perform comprehensive proteomic and single-cell transcriptomic analyses of infected-erythroblasts and of iEV-treated erythroblasts at different timepoints spanning erythroid differentiation to identify host cell pathways and genes involved in suppression of erythropoiesis. We will further decipher the most promising signals using genetic complementation and phenotypic analysis. The second objective is to identify parasite factor(s) that alter erythropoiesis. Proteomic analysis of iEVs combined with in silico analysis lead to the identification of 5 parasite protein candidates. We will investigate their role in erythropoiesis dysfunction, using tagged-transgenic KO parasites combined with immunoprecipitation techniques. The third objective is to validate in vivo the identified pathways and parasite factors by analyzing bone marrow (BM) and blood samples from malaria infected patients. For this, we will perform single cell RNAseq, combined with cytometry and imaging approaches on BM samples. We will also analyze the presence and the function of identified parasite effectors in iEVs collected from BM and plasma samples.
Overall, ERYMAP will help in defining the processes by which Plasmodium falciparum interferes with erythropoiesis and will open new avenues for the identification of biomarkers to predict severe anemia in malaria patients. ERYMAP will benefit from the strong complementary expertise of four teams working in the fields of erythropoiesis, malaria, transcriptomics and electrophysiology of Plasmodium-infected red cells. Team 1 already successfully collaborated with each of the 3 other partners and will coordinate ERYMAP, leading to a promising scientific synergy.