Global transcriptomic comparisons between fetal liver and bone marrow definitive erythropoiesis

Erythropoiesis occurs first in the yolk sac as a transit “primitive” form, then is gradually re-placed by the “definitive” form in the fetal liver (FL) during fetal development and in the bone marrow (BM) postnatal. While it is well known that differences exist between primitive and de-finitive erythropoiesis, the similarities and differences between FL and BM definitive erythropoi-esis have not been studied. Here we performed comprehensive comparisons of erythroid progen-itors and precursors at all maturational stages sorted from E16.5 FL and adult BM. Transcriptome comparison revealed that genes with increased expression in FL BFU-E were en-riched in cell division. Interestingly, the expression levels of glucocorticoid receptor Nr3c1, Myc and Myc downstream target Ccna2, were significantly higher in FL BFU-E, indicating the role of Nr3c1-Myc-Ccna2 axis in the enhanced proliferation/cell division of FL BFU-E cells. At the CFU-E stage, the expression of genes associated with hemoglobin biosynthesis were much higher in FL CFU-E, indicating more hemoglobin production. During terminal erythropoiesis, overall temporal patterns in gene expression were conserved between FL and BM. While biological pro-cesses related to translation, TCA and hypoxia response were upregulated in FL erythroblasts, that related to antiviral signal pathway were upregulated in BM erythroblasts. Our findings un-covered previously unrecognized differences between FL and BM definitive erythropoiesis and provide novel insights into erythropoiesis.