Project description:The regulatory system of erythropoiesis through erythropoietin (EPO) and its receptor (EPOR) is essential for vertebrates' life. In humans, EPO affects the erythroid progenitors and stimulates proliferation and differentiation. The EPO-EPOR axis is mainly mediated by the JAK2-STAT5 pathway. After terminal maturation, erythrocytes lost EPOR expression; however, erythrocytes of amphibian Xenopus tropicalis maintain EPOR expression even after their terminal maturation. Because erythrocytes of vertebrates except for adult mammals are nucleated, we hypothesized that EPO can alter its transcriptional state. To explore the effects of EPO on Xenopus mature erythrocytes, we performed RNA-Seq analysis on EPO-stimulated Xenopus peripheral blood cells. The EPO-stimulated group showed increased expression of direct target genes of STAT such as cish, socs3, and socs1 indicating a functional signal transduction system. Furthermore, we observed several EPO-responsive genes that were not reported in mammalian erythroid progenitors. These findings suggest the functional difference between enucleated erythrocytes in adult mammals and nucleated erythrocytes in fetal mammals and non-mammalian vertebrates.
Project description:Hypoxia is associated with increased erythropoietin (EPO) release to drive erythropoiesis. However, a prolonged sojourn at high altitude results in an increase in EPO levels followed by a decrease, although erythropoiesis remains elevated at a stable level. The role of hypoxia and related EPO adjustments are not fully understood and contributed to the formulation of the theory of neocytolysis. In this study, we aimed to exclusively evaluate the role of oxygen on erythropoiesis comparing in vitro erythroid differentiation performed at atmospheric oxygen, with a lower oxygen concentration (3% O2) and with cultures of erythroid precursors isolated from peripheral blood after a 19-day sojourn at high altitude (3450 m). Results highlight an accelerated erythroid maturation at low oxygen and more concave morphology of reticulocytes. No differences in deformability were observed in the formed reticulocytes in the tested conditions. Moreover, hematopoietic stem and progenitor cells isolated from blood affected by hypoxia at high altitude did not result in a different erythroid development, suggesting no retention of high altitude signature but rather an immediate adaptation to oxygen concentration. This adaptation was observed during in vitro erythropoiesis at 3% oxygen, displaying a significantly increased glycolytic metabolic profile. These hypoxia-induced effects on in vitro erythropoiesis fail to provide an intrinsic explanation to the concept of neocytolysis.
Project description:Transcriptional profiling of human mesenchymal stem cells comparing normoxic MSCs cells with hypoxic MSCs cells. Hypoxia may inhibit senescence of MSCs during expansion. Goal was to determine the effects of hypoxia on global MSCs gene expression.
Project description:Gene methylation profiling of immortalized human mesenchymal stem cells comparing HPV E6/E7-transfected MSCs cells with human telomerase reverse transcriptase (hTERT)- and HPV E6/E7-transfected MSCs. hTERT may increase gene methylation in MSCs. Goal was to determine the effects of different transfected genes on global gene methylation in MSCs.
Project description:Kynureninase is a member of a large family of catalytically diverse but structurally homologous pyridoxal 5'-phosphate (PLP) dependent enzymes known as the aspartate aminotransferase superfamily or alpha-family. The Homo sapiens and other eukaryotic constitutive kynureninases preferentially catalyze the hydrolytic cleavage of 3-hydroxy-l-kynurenine to produce 3-hydroxyanthranilate and l-alanine, while l-kynurenine is the substrate of many prokaryotic inducible kynureninases. The human enzyme was cloned with an N-terminal hexahistidine tag, expressed, and purified from a bacterial expression system using Ni metal ion affinity chromatography. Kinetic characterization of the recombinant enzyme reveals classic Michaelis-Menten behavior, with a Km of 28.3 +/- 1.9 microM and a specific activity of 1.75 micromol min-1 mg-1 for 3-hydroxy-dl-kynurenine. Crystals of recombinant kynureninase that diffracted to 2.0 A were obtained, and the atomic structure of the PLP-bound holoenzyme was determined by molecular replacement using the Pseudomonas fluorescens kynureninase structure (PDB entry 1qz9) as the phasing model. A structural superposition with the P. fluorescens kynureninase revealed that these two structures resemble the "open" and "closed" conformations of aspartate aminotransferase. The comparison illustrates the dynamic nature of these proteins' small domains and reveals a role for Arg-434 similar to its role in other AAT alpha-family members. Docking of 3-hydroxy-l-kynurenine into the human kynureninase active site suggests that Asn-333 and His-102 are involved in substrate binding and molecular discrimination between inducible and constitutive kynureninase substrates.
Project description:Erythropoiesis is a tightly regulated process. Development of red blood cells occurs through differentiation of hematopoietic stem cells into more committed progenitors and finally into erythrocytes. Binding of erythropoietin to its receptor (EpoR) is strictly required for erythropoiesis as it promotes survival and late maturation of erythroid progenitors. In vivo and in vitro studies have highlighted the requirement of EpoR signaling through Jak2 tyrosine-kinase and Stat5a/b as a central pathway. Here, we demonstrate that phospholipase C gamma 1 (Plcγ1) is activated downstream of EpoR/Jak2 independently of Stat5. Plcγ1-deficient proerythroblasts and erythroid progenitors exhibited strong impairment in differentiation and colony-forming potential. In vivo, suppression of Plcγ1 in immunophenotypically defined hematopoietic stem cells (Lin-Sca1+KIT+CD48-CD150+) severely reduced erythroid development. To identify Plcγ1 effector molecules involved in regulation of erythroid differentiation we assessed for changes on the level of transcription and DNA methylation after inactivation of Plcγ1. The single common downstream effector was H2AFY2, which encodes for the histone variant macroH2A2 (mH2A2). Suppression of macroH2A2 expression recapitulated the effects of Plcγ1 knockdown on erythroid maturation. Taken together, our findings identify Plcγ1 and its downstream target macroH2A2, as a ânon-canonicalâ signaling pathway essential for erythroid differentiation. MCIP-seq was used to interrogate methylation changes during Epo-induced differentiation of murine I/11 erythroblastic cell line upon knock-down of Plcy1 as compared to a mock control. Two different shRNA constructs that target Plcg1 were investigated at two different time points.
Project description:Transcriptional profiling of human mesenchymal stem cells comparing normoxic MSCs cells with hypoxic MSCs cells. Hypoxia may inhibit senescence of MSCs during expansion. Goal was to determine the effects of hypoxia on global MSCs gene expression. Two-condition experiment, Normoxic MSCs vs. Hypoxic MSCs.