ABSTRACT
Diamond-Blackfan anemia (DBA) is an inherited disorder characterized by defects in erythropoiesis, congenital abnormalities, and predisposition to cancer. Approximately 25% of DBA patients have a mutation in RPS19, which encodes a component of the 40S ribosomal subunit. Upregulation of p53 contributes to the pathogenesis of DBA, but the link between ribosomal protein mutations and erythropoietic defects is not well understood. We found that RPS19 deficiency in hematopoietic progenitor cells leads to decreased GATA1 expression in the erythroid progenitor population and p53-dependent upregulation of tumor necrosis factor-α (TNF-α) in nonerythroid cells. The decrease in GATA1 expression was mediated, at least in part, by activation of p38 MAPK in erythroid cells and rescued by inhibition of TNF-α or p53. The anemia phenotype in rps19-deficient zebrafish was reversed by treatment with the TNF-α inhibitor etanercept. Our data reveal that RPS19 deficiency leads to inflammation, p53-dependent increase in TNF-α, activation of p38 MAPK, and decreased GATA1 expression, suggesting a novel mechanism for the erythroid defects observed in DBA.
Subject(s)
GATA1 Transcription Factor/metabolism , Hematopoietic Stem Cells/metabolism , Inflammation/metabolism , Ribosomal Proteins/metabolism , Tumor Necrosis Factor-alpha/metabolism , p38 Mitogen-Activated Protein Kinases/metabolism , Animals , Blotting, Western , Cells, Cultured , Embryo, Nonmammalian/embryology , Embryo, Nonmammalian/metabolism , Enzyme Activation , Erythroid Cells/metabolism , Erythropoiesis/drug effects , Erythropoiesis/genetics , Etanercept , GATA1 Transcription Factor/genetics , Gene Expression , Humans , Immunoglobulin G/pharmacology , Inflammation/genetics , RNA Interference , Receptors, Tumor Necrosis Factor , Reverse Transcriptase Polymerase Chain Reaction , Ribosomal Proteins/genetics , Tumor Necrosis Factor-alpha/genetics , Tumor Suppressor Protein p53/genetics , Tumor Suppressor Protein p53/metabolism , Zebrafish/embryology , Zebrafish/genetics , Zebrafish/metabolism , p38 Mitogen-Activated Protein Kinases/geneticsABSTRACT
Cyclic AMP-response element-binding protein (CREB) is a transcription factor implicated in growth factor-dependent cell proliferation and survival, glucose homeostasis, spermatogenesis, circadian rhythms, and synaptic plasticity associated with memory. To study the phenotype of CREB overexpression in vivo, we generated CREB transgenic (TG) mice in which a myeloid specific hMRP8 promoter drives CREB expression. CREB TG mice developed spontaneous skin abscesses more frequently than wild type (WT) mice. To understand the role of CREB in myeloid function and innate immunity, chemokine expression in bone marrow derived macrophages (BMDMs) from CREB TG mice were compared with BMDMs from WT mice. Our results demonstrated decreased Keratinocyte-derived cytokine (KC) in CREB TG BMDMs but not TNFα protein production in response to lipid A (LPA). In addition, mRNA expression of KC and IL-1ß (Interleukin)-1ß was decreased in CREB TG BMDMs; however, there was no difference in the mRNA expression of TNFα, MCP-1, IL-6 and IL-12p40. The mRNA expression of IL-1RA and IL-10 was decreased in response to LPA. Nuclear factor kappa B (NFκB) expression and a subset of its target genes were upregulated in CREB TG mouse BMDMs. Although neutrophil migration was the same in both CREB TG and WT mice, Nicotinamide adenine dinucleotide phosphate (NADPH) oxidase activity was significantly increased in neutrophils from CREB TG mice. Taken together, CREB overexpression in myeloid cells results in increased abscess formation in vivo and aberrant cytokine and chemokine response, and neutrophil function in vitro.
Subject(s)
Abscess/etiology , Chemokines/metabolism , Cyclic AMP Response Element-Binding Protein/physiology , Cytokines/metabolism , Myeloid Cells/pathology , Neutrophils/pathology , Abscess/diagnosis , Animals , Cell Proliferation , Cell Survival , Chemokines/genetics , Cytokines/genetics , Female , Keratinocytes/metabolism , Keratinocytes/pathology , Macrophages/metabolism , Macrophages/pathology , Male , Mice , Mice, Inbred C57BL , Mice, Transgenic , Myeloid Cells/metabolism , Neutrophils/metabolism , Transcriptional ActivationABSTRACT
Gain of chromosome 8 is the most common chromosomal gain in human acute myeloid leukemia (AML). It has been hypothesized that gain of the MYC protooncogene is of central importance in trisomy 8, but the experimental data to support this are limited and controversial. In a mouse model of promyelocytic leukemia in which the MRP8 promoter drives expression of the PML-RARA fusion gene in myeloid cells, a Myc allele is gained in approximately two-thirds of cases as a result of trisomy for mouse chromosome 15. We used this model to test the idea that MYC underlies acquisition of trisomy in AML. We used a retroviral vector to drive expression of wild-type, hypermorphic, or hypomorphic MYC in bone marrow that expressed the PML-RARA transgene. MYC retroviruses cooperated in myeloid leukemogenesis and suppressed gain of chromosome 15. When the PML-RARA transgene was expressed in a Myc haploinsufficient background, we observed selection for increased copies of the wild-type Myc allele concomitant with leukemic transformation. In addition, we found that human myeloid leukemias with trisomy 8 have increased MYC. These data show that gain of MYC can contribute to the pathogenic effect of the most common trisomy of human AML.
