Gene expression profiling of early eosinophil development shows increased transcript levels of proinflammatory cytokines, chemokines, transcription factors, and a novel gene, EGO (eosinophil granule ontogeny). EGO is nested within an intron of the inositol triphosphate receptor type 1 (ITPR1) gene and is conserved at the nucleotide level; however, the largest open reading frame (ORF) is 86 amino acids. Sucrose density gradients show that EGO is not associated with ribosomes and therefore is a noncoding RNA (ncRNA). EGO transcript levels rapidly increase following interleukin-5 (IL-5) stimulation of CD34 ؉ hematopoietic progenitors. EGO RNA also is highly expressed in human bone marrow and in mature eosinophils. RNA silencing of EGO results in decreased major basic protein (MBP ) and eosinophil derived neurotoxin (EDN ) mRNA expression in developing IntroductionEosinophils are tissue-dwelling hematopoietic cells that likely play a role in parasitic immunity and allergic disease, such as asthma. 1 Activated eosinophils secrete toxic basic proteins such as major basic protein (MBP) and are postulated to cause bronchial hyperreactivity, damage of the bronchial mucosa, and remodeling of the airways. 1 Mice lacking eosinophils fail to show hallmarks of asthma such as airway hyperresponsiveness, tissue remodeling, and mucous metaplasia. 2,3 A more complete understanding of eosinophil development could lead to drugs targeting eosinophil progenitors prior to migration to the asthmatic lung.Eosinophils develop in the bone marrow from hematopoietic stem cells and migrate mainly to the gut or to sites of inflammation. Eosinophils, neutrophils, and monocytes have a common progenitor in the myeloid pathway of development. The combinatorial interactions of several transcription factors, including GATA-1, PU.1, and the CCAAT enhancer binding proteins, c/EBP␣ and ⑀, are important to eosinophil development. [4][5][6][7] High levels of PU.1 specify myeloid differentiation by antagonizing GATA-1 in the earliest stages of stem cell commitment. 8 In particular, a highaffinity GATA-1 binding site within the GATA-1 promoter appears to be critical for eosinophil development; deletion of this binding site in mice specifically abolishes the entire eosinophil lineage. 9 During later stages of eosinophil development, an intermediate level of GATA-1 in synergy with PU.1 directs the formation of the eosinophil lineage by activating dual binding sites in the MBP promoter. [10][11][12] GATA-1 also activates the eotaxin receptor CC chemokine receptor-3 (CCR3) promoter and the interleukin-5 (IL-5) receptor ␣ (IL-5R␣) gene. 13 The CCAAT enhancer binding protein, c/EBP␣, is important in early myeloid development, whereas c/EBP⑀ plays a later role. 14 Mouse knockouts of c/EBP⑀ affect both neutrophil and eosinophil development at the myelocyte to metamyelocyte stage. 14 Other genes involved in eosinophil development include the helix-loop-helix transcription factors, Id 1 and 2, and FOG (friend of GATA). FOG inhibits eosinophil development by intera...

The purpose of this study was to develop a cell-based screening assay for identification of small molecules for the treatment of asthma. Eosinophils are leukocytes that contribute to the pathology of asthma. Lidocaine inhibits interleukin-5 (IL-5)-mediated survival and activation of human eosinophils, and it is able to replace inhaled glucocorticoids for the treatment of asthma; however, lidocaine has many side effects, including anesthesia. Therefore, a collection of commercial and novel, synthesized lidocaine analogues were investigated for inhibitory activity of the IL-5-stimulated proliferation of TF-1 cells, a CD34 1 , cytokine-dependent, erythroleukemic cell line model for eosinophil growth. Among 74 investigated compounds, 10 were more potent inhibitors of cell proliferation than lidocaine (average IC 50 5 223 mM), with IC 50 values ranging within 1-119 mM. This cell-based assay is an effective method for screening chemical compounds and has revealed promising lead compounds for the treatment of asthma. Drug Dev Res 72: 353-360, 2011.

BACKGROUND c3orf75 is a conserved open reading frame within the human genome and has recently been identified as the Elongator subunit, ELP6 [1]. The Elongator enzyme complex has diverse roles, including translational control, neuronal development, cell migration and tumorigenicity [2]. OBJECTIVE To identify genes expressed early in human eosinophil development. METHODS Eosinophilopoiesis was investigated by gene profiling of IL-5 stimulated CD34+ cells; ELP6 mRNA is upregulated. A monoclonal antibody was raised to the recombinant protein predicted by the open reading frame. RESULTS ELP6 transcripts are upregulated in a human tissue culture model of eosinophil development during gene profiling experiments. Transcripts are expressed in most tissue types, as shown by reverse-transcriptase PCR. Western blot experiments show that human ELP6 is a 30 kDa protein expressed in the bone marrow, as well as in many other tissues. Flow cytometry experiments of human bone marrow mononuclear cells show that ELP6 is expressed intracellularly, in developing and mature human neutrophils, eosinophils and monocytes. CONCLUSIONS ELP6 is expressed intracellularly in developing and mature granulocytes and monocytes but not in lymphocytes and erythrocytes.