The Zinc Finger Transcription Factor Egr-1 Activates Macrophage Differentiation in M1 Myeloblastic Leukemia Cells

Mice with double knockout of Egr-1 and RCAN1 exhibit reduced inflammation during Pseudomonas aeruginosa lung infection

Pseudomonas aeruginosa represents one of the major opportunistic pathogens, which causes nosocomial infections in immunocompromised individuals. The molecular mechanisms controlling the host immune response to P. aeruginosa infections are not completely understood. In our previous study, early growth response 1 (Egr-1) and regulator of calcineurin 1 (RCAN1) were found to positively and negatively regulate the inflammatory responses, respectively, during P. aeruginosa pulmonary infection, and both of them had an impact on activating NF-κB pathway. Herein, we examined the inflammatory responses of Egr-1/RCAN1 double knockout mice using a mouse model of P. aeruginosa acute pneumonia. As a result, the Egr-1/RCAN1 double knockout mice showed reduced production of proinflammatory cytokines (IL-1β, IL-6, TNF and MIP-2), diminished inflammatory cell infiltration and decreased mortality, which were similar to those of Egr-1-deficienct mice but different from those of RCAN1-deficient mice. In vitro studies demonstrated that Egr-1 mRNA transcription preceded RCAN1 isoform 4 (RCAN1.4) mRNA transcription in macrophages, and the macrophages with Egr-1 deficiency exhibited decreased RCAN1.4 mRNA levels upon P. aeruginosa LPS stimulation. Moreover, Egr-1/RCAN1 double-deficient macrophages had reduced NF-κB activation compared to RCAN1-deficient macrophages. Taken together, Egr-1 predominates over RCAN1 in regulating inflammation during P. aeruginosa acute lung infection, which influences RCAN1.4 gene expression.

Inflammation in Focus: The Beginning and the End

The inflammation is an important biological response induced by various harmful stimuli, like viruses, bacterial infections, toxins, toxic compounds, tissue injury. During inflammation inflammatory cytokines and reactive oxygen species are produced. Inflammatory cytokines act on various receptors present on the plasma membrane of target cells. To initiate signaling cascade, and activate transcription factors, receptors should be internalized and enter the early endosomes, where the members of the signaling cascade can meet. The further cytoplasmic fate of the receptor plays crucial role in the progression and the course of inflammation. Usually acute inflammation removes injurious stimuli and helps to regain the normal healthy status of the organism. In contrast to this the uncontrolled chronic inflammation—stimulating other than immune cells, inducing transdifferentiation—can provide base of various serious diseases. This paper draws the attention of the long-lasting consequence of chronic inflammation, pointing out that one of the most important step in medication is to identify in time the factors initiating and maintaining inflammation.

The -172 A-to-G variation in ADAM17 gene promoter region affects EGR1/ADAM17 pathway and confers susceptibility to septic mortality with sepsis-3.0 criteria

BACKGROUND

A disintegrin and metalloproteinase 17 (ADAM17) is a proteolytic cleaving protein with a crucial function in the inflammatory responses, especially sepsis. But the clear role of ADAM17 in sepsis and the underlying mechanism remained unknown. In this study, we aim to determine the clinical association of ADAM17 -172A > G (rs12692386) promoter polymorphism with sepsis and to further explore the effect and mechanism of the early growth response 1 (EGR1)/ADAM17 pathway in inflammatory process during sepsis.

METHODS

A total of 477 sepsis patients and 750 controls were enrolled in this study to determine the association of ADAM17 -172A > G polymorphism with sepsis. The transcription factor binding to the promoter region of ADAM17 gene was predicted by bioinformatics analysis and verified by Chromatin Immunoprecipitation (ChIP) and luciferase assays. Quantitative real-time PCR and Western blot were performed to detect EGR1 and ADAM17 expression. Cytokine production was detected by enzyme-linked immunosorbent assay. The effect of EGR1/ADAM17 pathway on sepsis-induced inflammatory responses was evaluated in EGR1-silenced cells and endotoxemia mouse model.

RESULTS

The frequencies of non-survivors among the sepsis patients with the -172AG/GG genotypes and G allele were distinctly higher than those among patients with the AA genotype (53.9% vs. 39.7%, OR = 1.779, 95% CI = 1.119-2.829, P = 0.0142) and A allele (30.9% vs. 22.2%, OR = 1.570, 95% CI = 1.095-2.251, P = 0.0136). The Kaplan-Meier survival analysis indicated that the 28-day survival in septic patients with -172AG/GG genotypes of this functional ADAM17 promoter polymorphism was much worse than in the AA genotype carriers (log-rank = 5.358, P = 0.021). The results of in vitro lipopolysaccharide-stimulated and luciferase assays indicated that the -172 A-to-G variation could functionally upregulate promoter activity and transcription of ADAM17 gene via enhancing the binding affinity of its promoter region with the EGR1. The ChIP assay identified the direct interaction. Further studies demonstrated that inhibition of EGR1 significantly decreased ADAM17 expression and the pro-inflammatory cytokine secretion in vitro, and improved the survival and inflammatory response of sepsis mouse model.

CONCLUSIONS

These results provided evidence that the ADAM17 -172A > G polymorphism functionally promoted ADAM17 expression and enhanced sepsis-induced inflammatory responses via the EGR1/ADAM17 pathway, which ultimately conferred susceptibility to sepsis mortality and poor prognosis.

Oral Administration of Lactococcus lactis Producing Interferon Type II, Enhances the Immune Response Against Bacterial Pathogens in Rainbow Trout

Lactic acid bacteria are a powerful vehicle for releasing of cytokines and immunostimulant peptides at the gastrointestinal level after oral administration. However, its therapeutic application against pathogens that affect rainbow trout and Atlantic salmon has been little explored. Type II interferon in Atlantic salmon activates the antiviral response, protecting against viral infection, but its role against bacterial infection has not been tested in vivo. In this work, through the design of a recombinant lactic acid bacterium capable of producing Interferon gamma from Atlantic salmon, we explore its role against bacterial infection and the ability to stimulate systemic immune response after oral administration of the recombinant probiotic. Recombinant interferon was active in vitro, mainly stimulating IL-6 expression in SHK-1 cells. In vivo, oral administration of the recombinant probiotic produced an increase in IL-6, IFNγ and IL-12 in the spleen and kidney, in addition to stimulating the activity of lysozyme in serum. The challenge trials indicated that the administration of the IFNγ-producing probiotic doubled the survival in fish infected with F. psychrophilum. In conclusion, our results showed that the oral administration of lactic acid bacteria producing IFNγ managed to stimulate the immune response at a systemic level, conferring protection against pathogens, showing a biotechnological potential for its application in aquaculture.

Cellular and molecular events of inflammation induced transdifferentiation (EMT) and regeneration (MET) in mesenteric mesothelial cells

In this review we summarize the cellular and molecular events of inflammation induced epithelial-to-mesenchymal (EMT) and mesothelial-to-macrophage transition (MET) during regeneration. Since the receptor transmits the environmental stimulus, downregulating or upregulating the process on an epigenetic level, the intracellular localization of receptors (signaling organelles: early endosomes or lysosomal degradation: late endosomes) plays a crucial role in the signaling events regulating inflammation and regeneration. Therefore, we focused on the internalization of the receptors as well as the intracellular compartmentalization of signaling molecules during EMT and MET. The review draws the reader's attention to the plasticity of mesothelial cells and supports the idea that during inflammation an ambient macrophage population might derive from mesothelial cells.

Defective Sec61α1 underlies a novel cause of autosomal dominant severe congenital neutropenia

Background

The molecular cause of severe congenital neutropenia (SCN) is unknown in 30% to 50% of patients. SEC61A1 encodes the α-subunit of the Sec61 complex, which governs endoplasmic reticulum protein transport and passive calcium leakage. Recently, mutations in SEC61A1 were reported to be pathogenic in common variable immunodeficiency and glomerulocystic kidney disease.

Objective

Our aim was to expand the spectrum of SEC61A1-mediated disease to include autosomal dominant SCN.

Methods

Whole exome sequencing findings were validated, and reported mutations were compared by Western blotting, Ca2⁺ flux assays, differentiation of transduced HL-60 cells, in vitro differentiation of primary CD34 cells, quantitative PCR for unfolded protein response (UPR) genes, and single-cell RNA sequencing on whole bone marrow.

Results

We identified a novel de novo missense mutation in SEC61A1 (c.A275G;p.Q92R) in a patient with SCN who was born to nonconsanguineous Belgian parents. The mutation results in diminished protein expression, disturbed protein translocation, and an increase in calcium leakage from the endoplasmic reticulum. In vitro differentiation of CD34⁺ cells recapitulated the patient’s clinical arrest in granulopoiesis. The impact of Q92R-Sec61α1 on neutrophil maturation was validated by using HL-60 cells, in which transduction reduced differentiation into CD11b⁺CD16⁺ cells. A potential mechanism for this defect is the uncontrolled initiation of the unfolded protein stress response, with single-cell analysis of primary bone marrow revealing perturbed UPR in myeloid precursors and in vitro differentiation of primary CD34⁺ cells revealing upregulation of CCAAT/enhancer-binding protein homologous protein and immunoglobulin heavy chain binding protein UPR-response genes.

Conclusion

Specific mutations in SEC61A1 cause SCN through dysregulation of the UPR.

CDK6 Inhibition: A Novel Approach in AML Management

Acute myeloid leukemia (AML) is a complex disease with an aggressive clinical course and high mortality rate. The standard of care for patients has only changed minimally over the past 40 years. However, potentially useful agents have moved from bench to bedside with the potential to revolutionize therapeutic strategies. As such, cell-cycle inhibitors have been discussed as alternative treatment options for AML. In this review, we focus on cyclin-dependent kinase 6 (CDK6) emerging as a key molecule with distinct functions in different subsets of AML. CDK6 exerts its effects in a kinase-dependent and -independent manner which is of clinical significance as current inhibitors only target the enzymatic activity.

Oral crocetin administration suppressed refractive shift and axial elongation in a murine model of lens-induced myopia

Increased global incidence of myopia necessitates establishment of therapeutic approaches against its progression. To explore agents which may control myopia, we screened 207 types of natural compounds and chemical reagents based on an activity of a myopia suppressive factor, early growth response protein 1 (Egr-1) in vitro. Among the candidates, crocetin showed the highest and dose-dependent activation of Egr-1. For in vivo analysis, experimental myopia was induced in 3-week-old C57BL/6 J mice with −30 diopter (D) lenses for 3 weeks. Animals were fed with normal or mixed chow containing 0.003% (n = 19) and 0.03% (n = 7) of crocetin during myopia induction. Refraction and axial length were measured at 3-week-old and the 6-week-old with an infrared photorefractor and a SD-OCT system. Compared to controls (n = 14), crocetin administration showed a significant smaller change of refractive errors (−13.62 ± 8.14 vs +0.82 ± 5.81 D for 0.003%, p < 0.01, −2.00 ± 4.52 D for 0.03%, p < 0.01) and axial elongation (0.27 ± 0.03 vs 0.22 ± 0.04 mm for 0.003%, p < 0.01, 0.23 ± 0.05 mm for 0.03%, p < 0.05). These results suggest that a dietary factor crocetin may have a preventive effect against myopia progression.

Inflammation-Induced Epithelial-to-Mesenchymal Transition and GM-CSF Treatment Stimulate Mesenteric Mesothelial Cells to Transdifferentiate into Macrophages

In our previous work, we showed that during inflammation-induced epithelial-to-mesenchymal transition (EMT), mesenteric mesothelial cells express ED1 (pan-macrophage marker), indicating that they are transformed into macrophage-like cells. In this paper, we provide additional evidences about this transition by following the phagocytic activity and the TNFα production of mesenteric mesothelial cells during inflammation. Upon injection of India ink particles or fluorescent-labeled bioparticles (pHrodo) into the peritoneal cavity of rats pretreated with Freund's adjuvant, we found that mesothelial cells efficiently engulfed these particles. A similar increase of internalization could be observed by mesothelial cells in GM-CSF pretreated primary mesenteric culture. Since macrophages are the major producers of tumor necrosis factor, TNFα, we investigated expression level of TNFα during inflammation-induced EMT and found that TNFα was indeed expressed in these cells, reaching the highest level at the 5th day of inflammation. Since TNFα is one of the target genes of early growth response (EGR1) transcription factor, playing important role in monocyte-macrophage differentiation, expression of EGR1 in mesothelial cells was also investigated by Western blot and immunocytochemistry. While mesothelial cells did not express EGR1, a marked increase was observed in mesothelial cells by the time of inflammation. Parallel to this, nuclear translocation of EGR1 was shown by immunocytochemistry at the day 5 of inflammation. Caveolin-1 level was high and ERK1/2 became phosphorylated as the inflammation proceeded showing a slight decrease when the regeneration started. Our present data support the idea that under special stimuli, mesenteric mesothelial cells are able to transdifferentiate into macrophages, and this transition is regulated by the caveolin-1/ERK1/2/EGR1 signaling pathway.

MYBL1 rearrangements and MYB amplification in breast adenoid cystic carcinomas lacking the MYB-NFIB fusion gene

Breast adenoid cystic carcinoma (AdCC), a rare type of triple-negative breast cancer, has been shown to be driven by MYB pathway activation, most often underpinned by the MYB-NFIB fusion gene. Alternative genetic mechanisms, such as MYBL1 rearrangements, have been reported in MYB-NFIB-negative salivary gland AdCCs. Here we report on the molecular characterization by massively parallel sequencing of four breast AdCCs lacking the MYB-NFIB fusion gene. In two cases, we identified MYBL1 rearrangements (MYBL1-ACTN1 and MYBL1-NFIB), which were associated with MYBL1 overexpression. A third AdCC harboured a high-level MYB amplification, which resulted in MYB overexpression at the mRNA and protein levels. RNA-sequencing and whole-genome sequencing revealed no definite alternative driver in the fourth AdCC studied, despite high levels of MYB expression and the activation of pathways similar to those activated in MYB-NFIB-positive AdCCs. In this case, a deletion encompassing the last intron and part of exon 15 of MYB, including the binding site of ERG-1, a transcription factor that may downregulate MYB, and the exon 15 splice site, was detected. In conclusion, we demonstrate that MYBL1 rearrangements and MYB amplification probably constitute alternative genetic drivers of breast AdCCs, functioning through MYBL1 or MYB overexpression. These observations emphasize that breast AdCCs probably constitute a convergent phenotype, whereby activation of MYB and MYBL1 and their downstream targets can be driven by the MYB-NFIB fusion gene, MYBL1 rearrangements, MYB amplification, or other yet to be identified mechanisms. Copyright © 2017 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Loss of Egr1, a human del5q gene, accelerates BCR-ABL driven chronic myelogenous leukemia

There is substantial evidence that early growth response-1 (Egr1) gene, a zinc-finger transcription factor, behaves as a tumor suppressor in leukemia. This includes reports from this laboratory that constitutive Egr1 overrides leukemia conferred by deregulated c-Myc or E2F-1 in the M1 myeloid leukemic cell line by promoting differentiation. To investigate the effect of Egr1 on the initiation and progression of Chronic Myelogenous Leukemia (CML), lethally irradiated syngeneic wild type mice were reconstituted with bone marrow (BM) from either wild type or Egr1 null mice transduced with a 210-kD BCR-ABL-expressing MSCV-retrovirus (bone marrow transplantation {BMT}). Loss of Egr1 was observed to accelerate the development of BCR-ABL driven leukemia in recipient mice, resulting in the development of a more aggressive disease, a significantly shortened median survival time, and increased BCR-ABL expressing leukemic stem/progenitor cells (GFP+Lin-cKit+Sca+). Egr1 deficient progenitors expressing BCR-ABL exhibited decreased apoptosis, and increased cell viability and proliferation relative to WT counterparts. Secondary BMT of BCR-ABL BM revealed that loss of Egr1 resulted in enrichment of LSCs, consistent with shorter survival time and more aggressive disease of these mice compared to WT counterparts. Furthermore, serial re-plating colony assays indicated that loss of Egr1 increased self-renewal ability of BCR-ABL expressing BM. These novel findings on the tumor suppressor role of Egr1 in CML provide the impetus to study the effect of altering Egr1 expression in AML, where the overall five year survival rate remains low. The effect of loss of Egr1 in CML could reflect its established functions in normal hematopoiesis, maintaining quiescence of HSCs and driving terminal differentiation to the monocyte/macrophage lineage. Gain of function studies should validate these conclusions and provide further rationale for increased Egr1 as a therapeutic target in AML.

Interleukin-6 Signaling Pathway and Its Role in Kidney Disease: An Update

Interleukin-6 (IL-6) is a pleiotropic cytokine that not only regulates the immune and inflammatory response but also affects hematopoiesis, metabolism, and organ development. IL-6 can simultaneously elicit distinct or even contradictory physiopathological processes, which is likely discriminated by the cascades of signaling pathway, termed classic and trans-signaling. Besides playing several important physiological roles, dysregulated IL-6 has been demonstrated to underlie a number of autoimmune and inflammatory diseases, metabolic abnormalities, and malignancies. This review provides an overview of basic concept of IL-6 signaling pathway as well as the interplay between IL-6 and renal-resident cells, including podocytes, mesangial cells, endothelial cells, and tubular epithelial cells. Additionally, we summarize the roles of IL-6 in several renal diseases, such as IgA nephropathy, lupus nephritis, diabetic nephropathy, acute kidney injury, and chronic kidney disease.

Goldfish (Carassius auratus L.) as a model system to study the growth factors, receptors and transcription factors that govern myelopoiesis in fish

The process of myeloid cell development (myelopoiesis) in fish has mainly been studied in three cyprinid species: zebrafish (Danio rerio), ginbuna carp (Carassius auratus langsdorfii) and goldfish (C. auratus, L.). Our studies on goldfish myelopoiesis have utilized in vitro generated primary kidney macrophage (PKM) cultures and isolated primary kidney neutrophils (PKNs) cultured overnight to study the process of macrophage (monopoiesis) and neutrophil (granulopoiesis) development and the key growth factors, receptors, and transcription factors that govern this process in vitro. The PKM culture system is unique in that all three subpopulations of macrophage development, namely progenitor cells, monocytes, and mature macrophages, are simultaneously present in culture unlike mammalian systems, allowing for the elucidation of the complex mixture of cytokines that regulate progressive and selective macrophage development from progenitor cells to fully functional mature macrophages in vitro. Furthermore, we have been able to extend our investigations to include the development of erythrocytes (erythropoiesis) and thrombocytes (thrombopoiesis) through studies focusing on the progenitor cell population isolated from the goldfish kidney. Herein, we review the in vitro goldfish model systems focusing on the characteristics of cell sub-populations, growth factors and their receptors, and transcription factors that regulate goldfish myelopoiesis.

Multifaceted roles of STIM proteins

Stromal interaction molecules (STIM1 and STIM2) are critical components of store-operated calcium entry. Sensing depletion of endoplasmic reticulum (ER) Ca(2+) stores, STIM couples with plasma membrane Orai channels, resulting in the influx of Ca(2+) across the PM into the cytosol. Although best recognized for their primary role as ER Ca(2+) sensors, increasing evidence suggests that STIM proteins have a broader variety of sensory capabilities than first envisaged, reacting to cell stressors such as oxidative stress, temperature, and hypoxia. Further, the array of partners for STIM proteins is now understood to range far beyond the Orai channel family. Here we discuss the implications of STIM's expanding role, both as a stress sensor and a general modulator of multiple physiological processes in the cell.

Proteomic analysis of rosiglitazone and guggulsterone treated 3T3-L1 preadipocytes

Adipogenesis is the differentiation of preadipocytes to adipocytes which is marked by the accumulation of lipid droplets. Adipogenic differentiation of 3T3-L1 cells is achieved by exposing the cells to Insulin, Dexamethasone and IBMX for 5-7 days. Thiazolidinedione drugs, like rosiglitazone are potent insulin sensitizing agents and have been shown to enhance lipid droplet formation in 3T3-L1 cells, a model cell line for preadipocyte differentiation. Guggulsterone is a natural drug extracted from the gum resin of tree Commiphora mukul. Guggulsterone has been shown to inhibit adipogenesis and induce apoptosis in 3T3-L1 cells. In this study we treated the 3T3-L1 preadipocytes with rosiglitazone and guggulsterone and assessed the protein expression profile using 2D gel electrophoresis-based proteomics to find out differential target proteins of these drugs. The proteins that were identified upon rosiglitazone treatment generally regulate cell proliferation and/or exhibit anti-inflammatory effect which strengthens its differentiation-inducing property. Guggulsterone treatment resulted in the identification of the apoptosis-inducing proteins to be up regulated which rightly is in agreement with the apoptosis-inducing property of guggulsterone in 3T3-L1 cells. Some of the proteins identified in our proteomic screen such as Galectin1, AnnexinA2 & TCTP were further confirmed by Real Time qPCR. Thus, the present study provides a better outlook of proteins being differentially regulated/expressed upon treatment with rosiglitazone and guggulsterone. The detailed study of the differentially expressed proteins identified in this proteomic screen may further provide the better molecular insight into the mode of action of these anti-diabetic drugs rosiglitazone and guggulsterone.

Down-regulation of Thanatos-associated protein 11 by BCR-ABL promotes CML cell proliferation through c-Myc expression

Bcr-Abl activates various signaling pathways in chronic myelogenous leukemia (CML) cells. The proliferation of Bcr-Abl transformed cells is promoted by c-Myc through the activation of Akt, JAK2 and NF-κB. However, the mechanism by which c-Myc regulates CML cell proliferation is unclear. In our study, we investigated the role of Thanatos-associated protein 11 (THAP11), which inhibits c-Myc transcription, in CML cell lines and in hematopoietic progenitor cells derived from CML patients. The induction of THAP11 expression by Abl kinase inhibitors in CML cell lines and in CML-derived hematopoietic progenitor cells resulted in the suppression of c-Myc. In addition, over-expression of THAP11 inhibited CML cell proliferation. In colony forming cells derived from CML-aldehyde dehydrogenase (ALDH)(hi) /CD34(+) cells, treatment with Abl kinase inhibitors and siRNA depletion of Bcr-Abl induced THAP11 expression and reduced c-Myc expression, resulting in inhibited colony formation. Moreover, overexpression of THAP11 significantly decreased the colony numbers, and also inhibited the expression of c-myc target genes such as Cyclin D1, ODC and induced the expression of p21(Cip1) . The depletion of THAP11 inhibited JAK2 or STAT5 inactivation-mediated c-Myc reduction in ALDH(hi) /CD34(+) CML cells. Thus, the induced THAP11 might be one of transcriptional regulators of c-Myc expression in CML cell. Therefore, the induction of THAP11 has a potential possibility as a target for the inhibition of CML cell proliferation.

PML is a key component for the differentiation of myeloid progenitor cells to macrophages

IFN regulatory factor-8 (IRF-8, previously known as ICSBP) is a key transcription factor driving the differentiation of granulocyte\monocyte progenitor (GMP) cells toward monocyte\macrophage lineage. The promyelocytic leukemia (PML) gene is an immediate target gene regulated by IRF-8 in response to IFN-γ activation. PML is a multifunctional protein that has many isoforms serving as the scaffold components for nuclear bodies (NBs) engaged in numerous proteins interactions. The role of PML in the retinoic acid pathway that drives GMPs to granulopoiesis is documented in the literature. Here, we show that PML is also involved in monopoiesis by mediating some of the IRF-8 activities during the differentiation of murine-derived bone marrow macrophages (BMMs). PML silencing resulted in altered expression level of key transcription factors essential for monopoiesis that was accompanied by silencing of typical myeloid-specific genes. Interestingly, this altered expression resembled that of the GMPs and that of BMMs derived from IRF-8(-/-) mice altogether supporting the role of PML in monopoiesis. Further, PML silencing led to reduced colony-forming capacity of bone marrow cells highlighting the dual function of PML in myelopoiesis. Last, PML overexpression only partially rescued the phenotype of IRF-8(-/-) BMMs. Together, our data show that PML is an important factor for monopoiesis and not solely for granulopoiesis. This suggests that PML-NBs respond to an incoming signal that affects the fate of GMP driving cell differentiation to granulocytes or monocytes.

Batf promotes growth arrest and terminal differentiation of mouse myeloid leukemia cells

Batf is a basic leucine zipper transcription factor belonging to the activator protein-1 superfamily. Batf expression is regulated following stimulation of both lymphoid and myeloid cells. When treated with leukemia inhibitory factor, mouse M1 myeloid leukemia cells commit to a macrophage differentiation program that is dependent on Stat3 and involves the induction of Batf gene transcription via the binding of Stat3 to the Batf promoter. RNA interference was employed to block Batf induction in this system and the cells failed to growth arrest or to terminally differentiate. Restoring Batf expression not only reversed the differentiation-defective phenotype but also caused the cells to display signs of spontaneous differentiation in the absence of stimulation. Efforts to define genetic targets of the Batf transcription factor in M1 cells led to the identification of c-myb, a proto-oncogene known to promote blood cell proliferation and to inhibit the differentiation of M1 cells. These results provide strong evidence that Batf mediates the differentiation-inducing effects of Stat3 signaling in M1 cells and suggest that Batf may play a similar role in other blood cell lineages where alterations to the Jak-Stat pathway are hallmarks of disrupted development and disease.

Eukaryotic signaling pathways targeted by Salmonella effector protein AvrA in intestinal infection in vivo

Background

The Salmonella AvrA gene is present in 80% of Salmonella enterica serovar strains. AvrA protein mimics the activities of some eukaryotic proteins and uses these activities to the pathogen's advantage by debilitating the target cells, such as intestinal epithelial cells. Therefore, it is important to understand how AvrA works in targeting eukaryotic signaling pathways in intestinal infection in vivo. In this study, we hypothesized that AvrA interacts with multiple stress pathways in eukaryotic cells to manipulate the host defense system. A whole genome approach combined with bioinformatics assays was used to investigate the in vivo genetic responses of the mouse colon to Salmonella with or without AvrA protein expression in the early stage (8 hours) and late stage (4 days). Specifically, we examined the gene expression profiles in mouse colon as it responded to pathogenic Salmonella stain SL1344 (with AvrA expression) or SB1117 (without AvrA expression).

Results

We identified the eukaryotic targets of AvrA and the cell signaling pathways regulated by AvrA in vivo. We found that pathways, such as mTOR, NF-kappaB, platelet-derived growth factors, vascular endothelial growth factor, oxidative phosphorylation, and mitogen-activated protein kinase signaling are specifically regulated by AvrA in vivo and are associated with inflammation, anti-apoptosis, and proliferation. At the early stage of Salmonella infection, AvrA mainly targeted pathways related to nuclear receptor signaling and oxidative phosphorylation. At the late stage of Salmonella infection, AvrA is associated with interferon-gamma responses.

Conclusion

Both early and late phases of the host response exhibit remarkable specificity for the AvrA+ Salmonella. Our studies provide new insights into the eukaryotic molecular cascade that combats Salmonella-associated intestinal infection in vivo.

Krox20/EGR2 deficiency accelerates cell growth and differentiation in the monocytic lineage and decreases bone mass

Krox20/EGR2, one of the 4 early growth response genes, is a highly conserved transcription factor implicated in hindbrain development, peripheral nerve myelination, tumor suppression, and monocyte/macrophage cell fate determination. Here, we established a novel role for Krox20 in postnatal skeletal metabolism. Microcomputed tomographic analysis of 4- and 8-week-old mice revealed a low bone mass phenotype (LBM) in both the distal femur and the vertebra of Krox20(+/-) mice. This was attributable to accelerated bone resorption as demonstrated in vivo by increased osteoclast number and serum C-terminal telopeptides, a marker for collagen degradation. Krox20 haploinsufficiency did not reduce bone formation in vivo, nor did it compromise osteoblast differentiation in vitro. In contrast, growth and differentiation were significantly stimulated in preosteoclast cultures derived from Krox20(+/-) splenocytes, suggesting that the LBM is attributable to Krox20 haploinsufficiency in the monocytic lineage. Furthermore, Krox20 silencing in preosteoclasts increased cFms expression and response to macrophage colony-stimulating factor, leading to a cell-autonomous stimulation of cell-cycle progression. Our data indicate that the antimitogenic role of Krox20 in preosteoclasts is the predominant mechanism underlying the LBM phenotype of Krox20-deficient mice. Stimulation of Krox20 expression in preosteoclasts may present a viable therapeutic strategy for high-turnover osteoporosis.

Downregulation of stathmin expression is mediated directly by Egr1 and associated with p53 activity in lung cancer cell line A549

Stathmin is overexpressed in a variety of assessed human malignancies and is correlated with tumor progression and poor prognosis. Downregulation of its expression will contribute to optimize therapeutic outcomes in the treatment of various malignancies. However, the mechanisms of stathmin gene overexpression are not completely elucidated at present. Early growth response 1 (Egr1) is a transcription factor that triggers transcription of downstream genes mediating cell growth and angiogenesis upon various stimulations. Following the previous computational identification of a site that was thought to be an Egr1 consensus binding sequence at -85 to -94 region in stathmin gene promoter, we analyzed the role of Egr1 in the regulation of stathmin gene expression in lung cancer cell line A549. The results showed that Egr1 transcription factor bound to the sequence 5'-GCGGGGGCG-3' within human stathmin gene promoter; and in reporter gene assays and overexpression experiments, both stathmin gene promoter activity and stathmin gene expression level were downregulated following endogenous or exogenous expression of Egr1. Using wild type Egr1 and knockout Egr1 cell lines, we demonstrated that p53 negatively regulates stathmin expression through Egr1 pathway. In summary, Egr1 is a novel regulator of stathmin expression and p53 mediates the transcriptional repression of stathmin by Egr1 in human lung cancer cells.

The transcriptional network that controls growth arrest and differentiation in a human myeloid leukemia cell line

Using deep sequencing (deepCAGE), the FANTOM4 study measured the genome-wide dynamics of transcription-start-site usage in the human monocytic cell line THP-1 throughout a time course of growth arrest and differentiation. Modeling the expression dynamics in terms of predicted cis-regulatory sites, we identified the key transcription regulators, their time-dependent activities and target genes. Systematic siRNA knockdown of 52 transcription factors confirmed the roles of individual factors in the regulatory network. Our results indicate that cellular states are constrained by complex networks involving both positive and negative regulatory interactions among substantial numbers of transcription factors and that no single transcription factor is both necessary and sufficient to drive the differentiation process.

Early growth response genes regulate B cell development, proliferation, and immune response

Egr-1 (early growth response gene-1) is an immediate early gene encoding a zinc finger motif-containing transcription factor. Upon cross-linking of BCR, mature B cells undergo proliferation with an increase in Egr-1 message. Immature B lymphoma cells that express Egr-1 message and protein constitutively are growth inhibited when Egr-1 is down-regulated by negative signals from BCR or by antisense oligonucleotides. To test the hypothesis that Egr-1 is important for B cell development, we examined B cells from primary and secondary lymphoid organs in Egr-1(-/-) mice. Marginal zone B cell development was arrested in these mice, whereas the B cells in all other compartments were increased. To test the hypothesis that Egr-1 function may be partially compensated by other Egr family members, we developed transgenic mice expressing a dominant negative form of Egr-1, which lacks the trans activation domain but retains the DNA-binding domain, in a B cell-specific manner. There was a decrease in B lymphopoiesis in the bone marrow accompanied by a reduction in splenic immature and mature B cells as well as marginal zone B cells in the transgenic mice. Moreover, transgenic mice respond poorly to BCR cross-linking in vitro and T-independent and T-dependent Ags in vivo.

Transcriptional regulation of human survivin by early growth response (Egr)-1 transcription factor

Survivin, a member of the inhibitor of apoptosis protein family, is involved in both, inhibition of apoptosis and regulation of cell division. Because of the tumor-specific expression of survivin, the reduction of its expression is an important therapeutic option in the treatment of malignant diseases. Thus, we analyzed the transcriptional regulation of survivin in order to establish survivin as a target gene for new therapeutic approaches. Here, we describe a novel regulatory region within the survivin promoter. After treatment with phorbol 12-myristate-13-acetate, the early growth response (Egr)-1 transcription factor binds to the sequence 5'GAGGGGGCG 3' within the human survivin promoter in vitro and in entire cells. In reporter-gene assays and overexpression experiments, survivin is downregulated following exogenous expression of wildtype Egr-1. Using p53 wildtype and mutated cell lines, we show that Egr-1 negatively regulates survivin expression and sensitizes cell lines to TRAIL-induced apoptosis.

Transcriptional diversity during monocyte to macrophage differentiation

Monocytes recruited into tissues from peripheral blood differentiate into macrophages, which are critical in the pathogenesis of many diseases. There is limited data concerning the global changes in the expression of genes during monocyte to macrophage differentiation, and how the patterns of change identify the mechanism contributing to macrophage differentiation or function. Employing microarray technology, we examined the transcriptional profile of in vitro adherence-induced differentiation of primary human monocytes into macrophages. We found the significant up regulation of genes contributing to the functions of macrophages, including those regulating to immunity and defense; lipid, fatty acid and steroid metabolism; cell adhesion, carbohydrate metabolism; amino acid metabolism and endocytosis. In contrast, the vast majority of transcription factors affected were down regulated during monocyte to macrophage differentiation, suggesting that transcriptional repression may be important for the transition from monocytes to macrophages. However, a limited number of transcription factors were up regulated, among these was C/EBPalpha, which may contribute to differentiation by regulating down stream genes, which are a characteristic of differentiated macrophages. These observations suggest that examination of the transcriptional profile in monocytes and macrophages in patients may identify relevant therapeutic targets in diseases mediated by macrophages.

Egr-1 abrogates the E2F-1 block in terminal myeloid differentiation and suppresses leukemia

Deregulated growth and blocks in differentiation collaborate in the multistage process of leukemogenesis. Previously, we have shown that ectopic expression of the zinc finger transcription factor Egr-1 in M1 myeloblastic leukemia cells promotes terminal differentiation with interleukin-6 (IL-6). In addition, we have shown that deregulated expression of the oncogene E2F-1 blocks the myeloid terminal differentiation program, resulting in proliferation of immature cells in the presence of IL-6. Here it is shown that the positive regulator of differentiation Egr-1 abrogates the E2F-1-driven block in myeloid terminal differentiation. The M1E2F-1/Egr-1 cells underwent G(0)/G(1) arrest and functional macrophage maturation following treatment with IL-6. Furthermore, Egr-1 diminished the aggressiveness of M1E2F-1 leukemias and abrogated the leukemic potential of IL-6-treated M1E2F-1 cells. Previously, we reported that Egr-1 abrogated the block in terminal myeloid differentiation imparted by deregulated c-myc, which blocks differentiation at a later stage than E2F-1, resulting in cells that have the characteristics of functionally mature macrophages that did not undergo G(0)/G(1) arrest. Taken together, this work extends and highlights the tumor suppressor role of Egr-1, with Egr-1 behaving as a tumor suppressor against two oncogenes, each blocking myeloid differentiation by a different mechanism. These findings suggest that Egr-1 and/or Egr-1 target genes may be useful tools to treat or suppress oncogene-driven hematological malignancies.

Early growth response transcriptional regulators are dispensable for macrophage differentiation

Early growth response (Egr) proteins comprise a family of transcriptional regulators (Egr1-4) that modulate gene expression involved in the growth and differentiation of many cell types. In particular, Egr1 is widely believed to have an essential role in regulating monocyte/macrophage differentiation. However, Egr1-deficient mice have normal numbers of functional macrophages, an observation that has led to the hypothesis that other Egr proteins may compensate for Egr1 function in vivo. We examined whether other Egr transcription factors have a functionally redundant role in monocyte/macrophage differentiation. Egr1 and Egr3 expression was found to be induced in myeloid cells when they were differentiated into macrophages by treatment with M-CSF, whereas Egr2 was minimally induced and Egr4 was not detected. In either Egr1/Egr3 or Egr1/Egr2 double homozygous mutant mice, macrophage differentiation and function remained unimpaired. Additionally, the expression of molecules that broadly inhibit Egr function failed to block commitment to the monocytic lineage or inhibit the maturation of monocyte precursors. Finally, several hemopoietic growth factors were found to induce Egr gene expression, indicating that Egr gene expression is not cell lineage specific. Taken together, these results demonstrate that Egr transcription factors are neither essential for nor specific to monocyte/macrophage differentiation.

Early growth response transcription factor EGR-1 regulates Galphaq gene in megakaryocytic cells

BACKGROUND

Galphaq (Gene GNAQ) plays a major role in platelet signal transduction but little is known regarding its transcriptional regulation.

OBJECTIVES

We studied Galphaq promoter activity using luciferase reporter gene assays in human erythroleukemia (HEL) cells treated with phorbol 12-myristate 13-acetate (PMA) for 24 h to induce megakaryocytic transformation.

METHODS AND RESULTS

PMA-treated HEL cells showed enhanced Galphaq expression. Reporter (luciferase) gene studies on 5' upstream construct (up to -116 bp from ATG) revealed a negative regulatory site at -238/-202 and two positive sites at -203/-138 and -1116/-731. The positive regulatory region -203/-138 contained overlapping Sp1/AP-2/EGR-1 consensus sites. Gel shift studies on Galphaq oligonucleotides 1 (-203/-175) and 2 (-174/-152) using HEL cell extracts demonstrated protein binding that was due to early growth response factor EGR-1 at two sites. Mutations in either EGR-1 site markedly decreased the gene activity, indicating functional relevance. Mutation of consensus E-Box motif (-185/-180) had no effect. Reduction in the expression of endogenous EGR-1 with antisense oligonucleotide to EGR-1 inhibited PMA-induced Galphaq transcription. Correspondingly, Egr-1 deficient mouse platelets also showed approximately 50% reduction in the Galphaq expression relative to wild-type platelets.

CONCLUSIONS

These studies suggest that Galphaq gene is regulated during PMA-induced megakaryocytic differentiation by EGR-1, an early growth response transcription factor that regulates a wide array of genes and plays a major role in diverse activities, including cell proliferation, differentiation and apoptosis, and in vascular response to injury and atherosclerosis.

Recent insights into the signals that control alphabeta/gammadelta-lineage fate

During thymopoiesis, two major types of mature T cells are generated that can be distinguished by the clonotypic subunits contained within their T-cell receptor (TCR) complexes: alphabeta T cells and gammadelta T cells. Although there is no consensus as to the exact developmental stage where alphabeta and gammadelta T-cell lineages diverge, gammadelta T cells and precursors to the alphabeta T-cell lineage (bearing the pre-TCR) are thought to be derived from a common CD4- CD8- double-negative precursor. The role of the TCR in alphabeta/gammadelta lineage commitment has been controversial, in particular whether different TCR isotypes intrinsically favor adoption of the corresponding lineage. Recent evidence supports a signal strength model of lineage commitment, whereby stronger signals promote gammadelta development and weaker signals promote adoption of the alphabeta fate, irrespective of the TCR isotype from which the signals originate. Moreover, differences in the amplitude of activation of the extracellular signal-regulated kinase- mitogen-activated protein kinase-early growth response pathway appear to play a critical role. These findings will be placed in context of previous analyses in an effort to more precisely define the signals that control T-lineage fate during thymocyte development.

Predictive toxicogenomics approaches reveal underlying molecular mechanisms of nongenotoxic carcinogenicity

Toxicogenomics technology defines toxicity gene expression signatures for early predictions and hypotheses generation for mechanistic studies, which are important approaches for evaluating toxicity of drug candidate compounds. A large gene expression database built using cDNA microarrays and liver samples treated with over one hundred paradigm compounds was mined to determine gene expression signatures for nongenotoxic carcinogens (NGTCs). Data were obtained from male rats treated for 24 h. Training/testing sets of 24 NGTCs and 28 noncarcinogens were used to select genes. A semiexhaustive, nonredundant gene selection algorithm yielded six genes (nuclear transport factor 2, NUTF2; progesterone receptor membrane component 1, Pgrmc1; liver uridine diphosphate glucuronyltransferase, phenobarbital-inducible form, UDPGTr2; metallothionein 1A, MT1A; suppressor of lin-12 homolog, Sel1h; and methionine adenosyltransferase 1, alpha, Mat1a), which identified NGTCs with 88.5% prediction accuracy estimated by cross-validation. This six genes signature set also predicted NGTCs with 84% accuracy when samples were hybridized to commercially available CodeLink oligo-based microarrays. To unveil molecular mechanisms of nongenotoxic carcinogenesis, 125 differentially expressed genes (P<0.01) were selected by Student's t-test. These genes appear biologically relevant, of 71 well-annotated genes from these 125 genes, 62 were overrepresented in five biochemical pathway networks (most linked to cancer), and all of these networks were linked by one gene, c-myc. Gene expression profiling at early time points accurately predicts NGTC potential of compounds, and the same data can be mined effectively for other toxicity signatures. Predictive genes confirm prior work and suggest pathways critical for early stages of carcinogenesis.

Quantitative production of macrophages or neutrophils ex vivo using conditional Hoxb8

Differentiation mechanisms and inflammatory functions of neutrophils and macrophages are usually studied by genetic and biochemical approaches that require costly breeding and time-consuming purification to obtain phagocytes for functional analysis. Because Hox oncoproteins enforce self-renewal of factor-dependent myeloid progenitors, we queried whether estrogen-regulated Hoxb8 (ER-Hoxb8) could immortalize macrophage or neutrophil progenitors that would execute normal differentiation and normal innate immune function upon ER-Hoxb8 inactivation. Here we describe methods to derive unlimited quantities of mouse macrophages or neutrophils by immortalizing their respective progenitors with ER-Hoxb8 using different cytokines to target expansion of different committed progenitors. ER-Hoxb8 neutrophils and macrophages are functionally superior to those produced by many other ex vivo differentiation models, have strong inflammatory responses and can be derived easily from embryonic day 13 (e13) fetal liver of mice exhibiting embryonic-lethal phenotypes. Using knockout or small interfering RNA (siRNA) technologies, this ER-Hoxb8 phagocyte maturation system represents a rapid analytical tool for studying macrophage and neutrophil biology.

De novo synthesis of early growth response factor-1 is required for the full responsiveness of mast cells to produce TNF and IL-13 by IgE and antigen stimulation

Early growth-response factor 1 (Egr-1) is a zinc-finger transcription factor that plays a regulatory role in the expression of many genes important for inflammation. Whether Egr-1 is involved in IgE-dependent mast-cell activation was investigated. We demonstrated that IgE and antigen (TNP) stimulation induced a rapid expression of Egr-1 mRNA in mouse bone marrow-derived mast cells (BMMCs). As early as 15 to 20 minutes after IgE + TNP stimulation, Egr-1 protein was detectable in the nucleus of BMMCs by immunofluorescence or electrophoretic mobility shift assay. To examine a role for Egr-1 in IgE-dependent cytokine production by mast cells, Egr-1-deficient (Egr-1-/-) BMMCs were developed from the bone marrow cells of Egr-1 knockout mice. Egr-1-/- BMMCs express similar levels of surface c-kit and IgE receptor as compared with those on Egr-1+/+ BMMCs. Importantly, IgE + TNP-induced TNF and IL-13 expression was significantly reduced at both mRNA and protein levels in Egr-1-/- BMMCs as compared with those in Egr-1+/+ BMMCs. Thus, our results suggest that de novo synthesis of Egr-1 represents a novel mechanism in FcepsilonRI signaling and is required for the full responsiveness of IgE-dependent TNF and IL-13 production by mast cells.

The interferon-inducible gene, Ifi204, is transcriptionally activated in response to M-CSF, and its expression favors macrophage differentiation in myeloid progenitor cells

The interferon-inducible (Ifi)204 gene was isolated as a macrophage-colony stimulating factor (M-CSF)-responsive gene using a gene trap approach in the myeloid interleukin-3 (IL-3)-dependent FD-Fms cell line, which differentiates in macrophages in response to M-CSF. Here, we show that Ifi204 was transcriptionally activated in response to M-CSF, and FD-Fms cells decreased their growth and committed toward a macrophage morphology; this induction was abrogated when the differentiation signal of the M-CSF receptor was blocked; the Ifi204 gene was also induced during macrophage differentiation controlled by leukemia inhibitory factor; and the Ifi204 gene is expressed in different mature monocyte/macrophage cells. Finally, we showed that enforced expression of Ifi204 strongly decreased IL-3- and M-CSF-dependent proliferation and conversely, favored macrophage differentiation of FD-Fms cells in response to M-CSF. Altogether, these results demonstrate that the Ifi204 gene is activated during macrophage development and suggest that the Ifi204 protein may act as a regulator of the balance between proliferation and differentiation. Moreover, this study suggests that other members of the Ifi family might act as regulators of hematopoiesis under the control of hemopoietic cytokines.

Correlation between differentiation plasticity and mRNA expression profiling of CD34+-derived CD14− and CD14+ human normal myeloid precursors

In spite of their apparently restricted differentiation potentiality, hematopoietic precursors are plastic cells able to trans-differentiate from a maturation lineage to another. To better characterize this differentiation plasticity, we purified CD14- and CD14+ myeloid precursors generated by 'in vitro' culture of human CD34+ hematopoietic progenitors. Morphological analysis of the investigated cell populations indicated that, as expected, they consisted of granulocyte and monocyte precursors, respectively. Treatment with differentiation inducers revealed that CD14- cells were bipotent granulo-monocyte precursors, while CD14+ cells appeared univocally committed to a terminal macrophage maturation. Flow cytometry analysis demonstrated that the conversion of granulocyte precursors to the mono-macrophage maturation lineage occurs through a differentiation transition in which the granulocyte-related myeloperoxidase enzyme and the monocyte-specific CD14 antigen are co-expressed. Expression profiling evidenced that the observed trans-differentiation process was accompanied by a remarkable upregulation of the monocyte-related MafB transcription factor.

Animal models of acute myelogenous leukaemia - development, application and future perspectives

From the early inception of the transplant models through to contemporary genetic and xenograft models, evolution of murine leukaemic model systems have been critical to our general comprehension and treatment of cancer, and, more specifically, disease states such as acute myelogenous leukaemia (AML). However, even with modern advances in therapeutics and molecular diagnostics, the majority of AML patients die from their disease. Thus, in the absence of definitive in vitro models which precisely recapitulate the in vivo setting of human AMLs and failure of significant numbers of new drugs late in clinical trials, it is essential that murine AML models are developed to exploit more specific, targeted therapeutics. While various model systems are described and discussed in the literature from initial transplant models such as BNML and spontaneous murine leukaemia virus models, to the more definitive genetic and clinically significant NOD/SCID xenograft models, there exists no single compendium which directly assesses, reviews or compares the relevance of these models. Thus, the function of this article is to provide clinicians and experimentalists a chronological, comprehensive appraisal of all AML model systems, critical discussion on the elucidation of their roles in our understanding of AML and consideration to their efficacy in the development of AML chemotherapeutics.

Egr-1 abrogates the block imparted by c-Myc on terminal M1 myeloid differentiation

Both deregulated growth and blocks in differentiation cooperate in the multistage process of leukemogenesis. Thus, understanding functional interactions between genes that regulate normal blood cell development, including cell growth and differentiation, and how their altered expression contributes to leukemia, is important for rational drug design. Previously, we have shown that the zinc finger transcription factor Egr-1 plays a role in monocytic differentiation. Ectopic expression of Egr-1 in M1 myeloblastic leukemia cells was observed to activate the macrophage differentiation program in the absence of the differentiation inducer interleukin 6 (IL-6) and to promote terminal differentiation in its presence. In addition, we have shown that deregulated expression of the proto-oncogene c-myc blocks the myeloid terminal differentiation program. Here we show that restoring expression of Egr-1 in M1 cells that express deregulated c-Myc abrogates the c-Myc block in terminal differentiation, resulting in cells that undergo functional macrophage maturation. However, there is an absence of both growth arrest and cell adhesion. In addition, Egr-1 expression diminished M1myc leukemogenicity in vivo. These findings indicate that Egr-1 can act as a tumor suppressor gene and suggest that Egr-1 or Egr-1 targets may provide important tools for differentiation therapy in certain leukemic phenotypes.

Tissue inhibitor of matrix metalloproteinase-1 overexpression in M1 myeloblasts impairs IL-6-induced differentiation

The balance between matrix metalloproteinase (MMP) and tissue inhibitor of matrix metalloproteinase (TIMP) is important for extracellular matrix interactions of hematopoietic cells. MMP-independent growth modulating activity for TIMP-1 on B lymphocytes and erythroid progenitors has also been described, but a role for TIMP-1 in myelomonocytic differentiation has not been previously reported. In this study, we demonstrate that TIMP-1 overexpression impairs differentiation of the myeloblastic M1 cell line following interleukin (IL)-6 stimulation. We generated retroviral vectors coexpressing human TIMP-1 and the green fluorescent protein (GFP) and stably transduced murine M1 myeloid cells. TIMP-1 expressing cells showed a large reduction in IL-6-induced macrophage differentiation in vitro that was reversible with a specific monoclonal antibody. The differentiation delay in M1/TIMP-1 cells was also specifically reversible by pharmacologic phosphatidylinositol-3 kinase (PI3-K) inhibition. Additionally, overexpression of a TIMP-1/GFP fusion protein also impaired M1 differentiation and this protein was localized to the cell surface, consistent with an autocrine receptor-mediated mechanism. Surprisingly, TIMP-1 transduced cells had a selective advantage for growth in IL-6, indicating that functional effects on growth and differentiation of M1 cells were primarily through an autocrine mechanism. Intrinsic TIMP-1 expression in myeloid leukemia cells might thus impact upon survival or differentiation.

CD8 T cell responses to lymphocytic choriomeningitis virus in early growth response gene 1-deficient mice

Previous in vitro work has implicated a role for transcriptional factor early growth response gene 1 (EGR1) in regulating immune responses. However, the in vivo role of EGR1 in orchestrating T cell responses has not been studied. To investigate the importance of EGR1 in T cell immunity, we compared Ag-specific CD8 T cell responses between wild type (+/+) and EGR1-deficient (EGR1-/-) mice following an acute infection with lymphocytic choriomeningitis virus (LCMV). These studies revealed that the expansion of LCMV-specific CD8 T cells was substantially reduced in EGR1-/- mice, as compared with +/+ mice. The reduced numbers of LCMV-specific CD8 T cells in EGR1-/- mice were not due to an intrinsic T cell defect per se because purified EGR1-deficient T cells exhibited normal proliferative response to anti-CD3 stimulation in vitro, and underwent normal activation and expansion in response to LCMV upon adoptive transfer into T cell-deficient mice. Furthermore, adoptive transfer of CD8 T cells bearing a transgenic TCR into EGR1-/- mice showed that EGR1 deficiency in non-CD8 T cells impaired CD8 T cell expansion in vivo following an LCMV infection. Further investigations on accessory cells showed that bone marrow-derived dendritic cells from EGR1-/- mice did not exhibit detectable impairment to prime Ag-specific CD8 T cell responses in vivo. However, in LCMV-infected mice, EGR1 deficiency selectively impaired the maturation of CD8alpha(+ve) plasmacytoid dendritic cells. Taken together, our findings suggest that EGR1 might promote expansion of CD8 T cells during an acute viral infection by modulating the cues in the lymphoid microenvironment.

Altered expression of immune modulator and structural genes in neonatal unilateral ureteral obstruction

BACKGROUND

Congenital obstructive nephropathy is a condition characterized by hydronephrosis, tubular dilatation, apoptosis, and atrophy, as well as interstitial cellular infiltration and progressive interstitial fibrosis. The renal consequences of chronic unilateral ureteral obstruction (UUO) in the neonatal rat are similar to those of clinical congenital obstructive nephropathy.

METHODS

To define alterations in renal gene expression induced by chronic neonatal UUO, Sprague-Dawley rats were subjected to UUO or sham operation within the first 2 days of life, and kidneys were harvested after 12 days.

RESULTS

Microarray analysis revealed that the mRNA expression of multiple immune modulators, including krox24, interferon-gamma regulating factor-1 (IRF-1), monocyte chemoattractant protein-1 (MCP-1), interleukin-1beta (IL-1beta), CCAAT/enhancer binding protein (C/EBP), p21, c-fos, c-jun, and pJunB, was significantly increased in obstructed compared to sham-operated kidneys (all P < 0.05). Western blot analysis revealed significant changes in immune modulator protein abundance in the obstructed versus sham-operated kidney for krox24 (P = 0.0004), IRF-1 (P = 0.005), MCP-1 (P = 0.01), and JunD (P = 0.0008). Alternatively, the abundance of all of the immune modulator proteins was similar in sham-operated and obstructed kidneys in rats subjected to acute (4 days) neonatal UUO. Microarray analysis studies also reveal that structural genes that comprise the cytoskeleton and cell matrix are significantly up-regulated by chronic neonatal UUO, including calponin, desmin, dynamin, and lumican (all P < 0.05).

CONCLUSION

Multiple genes are aberrantly expressed in the kidney of rats subjected to chronic neonatal UUO. Elucidation of these genes involved in neonatal UUO may lead to new insight about congenital obstructive nephropathy.

Reduced tumorigenicity of murine leukemia cells expressing protein-tyrosine phosphatase, PTPepsilon C

Recently, we reported that a cytosolic isoform of protein-tyrosine phosphatase epsilon (PTP epsilon C), when overexpressed, inhibits terminal differentiation and apoptosis of murine M1 myeloblastic leukemia cells induced by interleukin-6. To determine whether these observed effects in vitro correspond to a tumorigenicity of PTP epsilon C-expresser (M1- epsilon C) cells in vivo, parent M1 and M1- epsilon C cells were intravenously inoculated into scid or nude mice, and survival of mice receiving these cell lines was monitored. Unexpectedly, both scid and nude mice inoculated with M1- epsilon C cells showed significantly prolonged survival time than those receiving parent M1 cells. While parent M1 cells inoculated by intravenous injection formed metastatic tumors in the spleen, expression of PTP epsilon C suppressed tumor development in the spleen. The results suggest a suppressive role of PTP epsilon C in tumorigenesis.

Bacterial lipopolysaccharide-induced expression of the IkappaB protein MAIL in B-lymphocytes and macrophages

Molecule possessing ankyrin-repeats induced by lipopolysaccharide (MAIL), a recently cloned nuclear IkappaB protein induced by lipopolysaccharide (LPS) stimulation in lymphoid organs, is involved in the regulation of inflammatory responses. The present in situ hybridization and immunohistochemical analyses revealed the distinct expression of the MAIL mRNA and protein in B-lymphocytes of the white pulp of the spleen and cortical lymphoid follicles of lymph nodes in LPS-injected mice. MAIL signals were also localized in F4/80-positive macrophages in these organs. LPS clearly induced MAIL expression in cultured B-lymphocytes and monocytes/macrophages, but only faintly so in T-lymphocytes, fibroblasts, and endothelial cells. MAIL was also induced by inflammatory cytokines such as interleukin-1 and -6, and tumor necrosis factor in cultured cells. Northern blot, Western blot, and in situ hybridization analyses showed that the major expression product of the Mail gene was a long splicing variant (MAIL-L) rather than a short one, both in lymphoid organs and cultured cells. These results collectively indicate that LPS induces MAIL-L predominantly in B-lymphocytes and macrophages.

Transcriptional regulation of myelopoiesis

A common myeloid progenitor gives rise to both granulocytes and monocytes. The early stages of granulopoiesis are mediated by the C/EBPalpha, PU.1, RAR, CBF, and c-Myb transcription factors, and the later stages require C/EBPepsilon, PU.1, and CDP. Monocyte development requires PU.1 and interferon consensus sequence binding protein and can be induced by Maf-B, c-Jun, or Egr-1. Cytokine receptor signals modulate transcription factor activities but do not determine cell fates. Several mechanisms orchestrate the myeloid developmental program, including cooperative gene regulation, protein:protein interactions, regulation of factor levels, and induction of cell cycle arrest.