Transcriptome analysis of murine Megakaryocytic-Erythroid Progenitors (MEPs) in a condition of iron deficiency (Tmprss KO)
The mechanism underlying thrombocytosis in patients with iron deficiency anemia remains unknown. We present findings that support the hypothesis that low iron biases the commitment of Megakaryocytic-Erythroid Progenitors (MEP) toward the megakaryocytic (Mk) lineage in mice. In MEP of Transmembrane serine protease 6 knockout (Tmprss6-/-) mice, which exhibit iron deficiency microcytic anemia concomitant with thrombocytosis, we observed a megakaryocytic (Mk) bias, decreased labile iron, and decreased proliferation relative to wild-type (WT) MEP. Bone marrow transplantation assays suggest that the systemic iron deficiency of the Tmprss6-/- recipients contributes to the MEP lineage commitment bias. Genes involved in metabolic, VEGF, and ERK pathways were enriched among those differentially expressed between WT and Tmprss6-/- MEP. Corroborating our findings from the murine model of chronic iron deficiency anemia, primary human MEP also exhibited decreased proliferation and Mk-biased commitment when their iron sensing pathways were disrupted by knockdown of Transferrin Receptor 2. These data are consistent with a model in which low iron in the marrow environment affects MEP metabolism, attenuates ERK signaling, slows proliferation, and biases MEP toward Mk lineage commitment. Keywords: megakaryocytic-erythroid progenitor (MEP), iron deficiency, Tmprss6 Overall design: In this study, we performed high-throughput sequencing of RNA isolated from MEP derived from WT and Tmprss6-/-  (KO) mice. Primary murine MEPs  (Lin-cKit+Sca-FcgRI/II-CD150+CD105-CD41-)  from 3 mice were pooled and sorted as one biological replicate. RNA-seq was performed in biological triplicates.