ABSTRACT: Background: It has been reported that the phosphatidylinositol 3-kinase (PI3K)-AKT signaling pathway regulates erythropoietin (EPO)-induced survival, proliferation, and maturation of early erythroid progenitors. Erythroid cell proliferation and survival has also been related to activation of the JAK-STAT pathway. The goal of this study was to observe the function of EPO activation of JAK-STAT and PI3K/AKT pathways in the development of erythroid progenitors from hematopoietic CD34+ progenitor cells, as well as to distinguish early EPO target genes in human erythroid progenitors during ontogeny. Methods: Hematopoietic CD34+ progenitor cells, isolated from fetal and adult hematopoietic tissues, were differentiated into erythroid progenitor cells. We have used microarray analysis to examine JAK-STAT and PI3K/AKT related genes, as well as broad gene expression modulation in these human erythroid progenitor cells. Results: In microarray studies, a total of 1755 genes were expressed in fetal liver, 3844 in cord blood, 1770 in adult bone marrow, and 1325 genes in peripheral blood-derived erythroid progenitor cells. The erythroid progenitor cells shared 1011 common genes. Using the Ingenuity Pathways Analysis software, we evaluated the network pathways of genes linked to hematological system development, cellular growth and proliferation. The KITLG, EPO, GATA1, PIM1 and STAT3 genes represent the major connection points in the hematological system development linked genes. Some JAK-STAT signaling pathway-linked genes were steadily upregulated throughout ontogeny (PIM1, SOCS, MYC, PTPN11), while others were downregulated (PTPN6, PIAS, SPRED2). In addition, some JAK-STAT pathway related genes have specific expression just at certain stages of ontogeny (STATs, GRB2, CREBB). Beside continuously upregulated (AKT1, PPP2CA, CHUK, NFKB1) and downregulated (FOXO1, PDPK1, PIK3CG) genes in the PI3K-AKT signaling pathway, we also observed intermittently regulated gene expression (NFKBIA, YWHAH). Conclusions: This broad overview of gene expression in erythropoiesis revealed transcription factors with a prevalence at certain stages of ontogenesis. Finally, our results show that EPO-mediated proliferation and survival of erythroid progenitors occurs mainly through modulation of JAK-STAT pathway associated STATs, GRB2 and PIK3 genes, as well as AKT pathway- coupled NFKBIA and YWHAH genes. Adult peripheral blood mononuclear cells were isolated from buffy coats of 3 healthy donors using Lymphocyte Separation Medium (BioWhittaker, Walkersville, MD). We washed mononuclear cells twice with Dulbecco's phosphate-buffered saline (PBS, Invitrogen Corporation, Carlsbad, CA), and CD34+ cells were purified by positive immunomagnetic selection using the MACS cell isolation system (Miltenyi Biotec, Auburn, CA). Fresh bone marrow CD34+ cells were collected (AllCells LLC, Berkeley, CA). Cord blood CD34+ cells (AllCells LLC) and fetal liver CD34+ cells (Cambrex Bio Science, Inc., Walkersville, MD) were collected and frozen. For analysis, CD34+ cells were resuspended in medium, which contained 30% FBS, 2 mmol/L glutamine, 100 U/ml penicillin, 100 µg/ml streptomycin, 1% deionized BSA, 10 mmol/L beta-mercaptoethanol, 1 mmol/L dexamethasone, 33 µg/ml holo-transferrin, 10 ng/ml SCF, 1 ng/ml IL-3 and 1 ng/ml GM-CSF (Sigma, St. Louis, MO), and 1 U/ml human recombinant EPO (Amgen Inc, Thousand Oaks, CA) Erythroid progenitor cells differentiated from hematopoietic CD34+ progenitor cells of fetal liver, cord blood, bone marrow and peripheral blood origin Biological replicates: 2 fetal liver, 3 cord blood, 3 bone marrow, 3 peripheral blood origin
