Molecular cloning, sequencing, and mapping of EGR2, a human early growth response gene encoding a protein with "zinc-binding finger" structure

Transcription factor EGR2 alleviates autoimmune uveitis via activation of GDF15 to modulate the retinal microglial phenotype

Uveitis is a vision-threatening disease primarily driven by a dysregulated immune response, with retinal microglia playing a pivotal role in its progression. Although the transcription factor EGR2 is known to be closely associated with uveitis, including Vogt-Koyanagi-Harada disease and Behcet's disease, and is essential for maintaining the dynamic homeostasis of autoimmunity, its exact role in uveitis remains unclear. In this study, diminished EGR2 expression was observed in both retinal microglia from experimental autoimmune uveitis (EAU) mice and inflammation-induced human microglia cell line (HMC3). We constructed a mice model with conditional knockout of EGR2 in microglia and found that EGR2 deficiency resulted in increased intraocular inflammation. Meanwhile, EGR2 overexpression downregulated the expression of inflammatory cytokines as well as cell migration and proliferation in HMC3 cells. Next, RNA sequencing and ChIP-PCR results indicated that EGR2 directly bound to its downstream target growth differentiation factor 15 (GDF15) and further regulated GDF15 transcription. Furthermore, intravitreal injection of GDF15 recombinant protein was shown to ameliorate EAU progression in vivo. Meanwhile, knockdown of GDF15 reversed the phenotype of EGR2 overexpression-induced microglial inflammation in vitro. In summary, this study highlighted the protective role of the transcription factor EGR2 in AU by modulating the microglial phenotype. GFD15 was identified as a downstream target of EGR2, providing a unique target for uveitis treatment.

MicroRNA-150 (miR-150) and Diabetic Retinopathy: Is miR-150 Only a Biomarker or Does It Contribute to Disease Progression?

Diabetic retinopathy (DR) is a chronic disease associated with diabetes mellitus and is a leading cause of visual impairment among the working population in the US. Clinically, DR has been diagnosed and treated as a vascular complication, but it adversely impacts both neural retina and retinal vasculature. Degeneration of retinal neurons and microvasculature manifests in the diabetic retina and early stages of DR. Retinal photoreceptors undergo apoptosis shortly after the onset of diabetes, which contributes to the retinal dysfunction and microvascular complications leading to vision impairment. Chronic inflammation is a hallmark of diabetes and a contributor to cell apoptosis, and retinal photoreceptors are a major source of intraocular inflammation that contributes to vascular abnormalities in diabetes. As the levels of microRNAs (miRs) are changed in the plasma and vitreous of diabetic patients, miRs have been suggested as biomarkers to determine the progression of diabetic ocular diseases, including DR. However, few miRs have been thoroughly investigated as contributors to the pathogenesis of DR. Among these miRs, miR-150 is downregulated in diabetic patients and is an endogenous suppressor of inflammation, apoptosis, and pathological angiogenesis. In this review, how miR-150 and its downstream targets contribute to diabetes-associated retinal degeneration and pathological angiogenesis in DR are discussed. Currently, there is no effective treatment to stop or reverse diabetes-caused neural and vascular degeneration in the retina. Understanding the molecular mechanism of the pathogenesis of DR may shed light for the future development of more effective treatments for DR and other diabetes-associated ocular diseases.

Identification of MicroRNAs With In Vivo Efficacy in Multiple Myeloma-related Xenograft Models

BACKGROUND/AIM

Multiple myeloma is a B-cell neoplasm, which can spread within the marrow of the bones forming many small tumors. In advanced disease, multiple myeloma can spread to the blood as plasma cell leukemia. In some cases, a localized tumor known as plasmacytoma is found within a single bone. Despite the approval of several agents such as melphalan, corticosteroids, proteasome inhibitors, thalidomide-based immuno-modulatory agents, histone deacetylase inhibitors, a nuclear export inhibitor and monoclonal antibodies daratuzumab and elatuzumab, the disease presently remains uncurable.

MATERIALS AND METHODS

In order to define new targets and treatment modalities we searched the literature for microRNAs, which increase or inhibit in vivo efficacy in multiple-myeloma-related xenograft models.

RESULTS AND CONCLUSION

We identified six up-regulated and twelve down-regulated miRs, which deserve further preclinical validation.

Molecular organization of the rat glia-derived nexin/protease nexin-1 promoter

The first three exons and the promoter of rat glia-derived nexin, also called protease nexin-1 (GDN/PN-1), have been identified through analysis of rat genomic clones. A 1.6 kilobase (kb) fragment containing 105 base pairs of the first exon and 5'-flanking sequences was sequenced. The 5'-flanking sequence and the first exon were found to be GC-rich, indicating that the 5' region of the rat GDN/PN-1 gene resides within a CpG island. A TATA box-like sequence, but no CAAT box, was found. The rat GDN/PN-1 promoter contains five SP1 consensus sites, four consensus sites for the MyoD1 transcription factor, and one binding site for the transcription factors NGFI-A, NGFI-C, Krox-20, and Wilms tumor factor. The presence of these consensus sequences is consistent with the known expression pattern of GDN/PN-1. Primer extension and RNase protection assays identified one transcriptional start site. The 1.6 kb promoter fragment cloned in a reporter plasmid was found to induce firefly luciferase expression in a cell-specific manner. A positive regulatory element is localized in the region -1545 to -389. In vitro CpG methylation blocked transcription from the GDN/PN-1 promoter in rat hepatoma cells but not in C6 rat glioma cells.

Role of early growth response 1 in arteriogenesis: Impact on vascular cell proliferation and leukocyte recruitment in vivo

Based on previous findings that early growth response 1 (Egr-1) participates in leukocyte recruitment and cell proliferation in vitro, this study was designed to investigate its mode of action during arteriogenesis in vivo. In a model of peripheral arteriogenesis, Egr-1 was significantly upregulated in growing collaterals of wild-type (WT) mice, both on mRNA and protein level. Egr-1−/− mice demonstrated delayed arteriogenesis after femoral artery ligation. They further showed increased levels of monocytes and granulocytes in the circulation, but reduced levels in adductor muscles under baseline conditions. After femoral artery ligation, elevated numbers of macrophages were detected in the perivascular zone of collaterals in Egr-1−/− mice and mRNA of leukocyte recruitment mediators was upregulated. Other Egr family members (Egr-2 to -4) were significantly upregulated only in Egr-1−/− mice, suggesting a mechanism of counterbalancing Egr-1 deficiency. Moreover, splicing factor-1, downregulated in WT mice after femoral artery ligation in the process of increased vascular cell proliferation, was upregulated in Egr-1−/− mice. αSM-actin on the other hand, significantly downregulated in WT mice, showed no differential expression in Egr-1−/− mice. While cell cycle regulator cyclin E and cdc20 were upregulated in Egr-1−/− mice, cyclin D1 expression decreased below the detection limit in collaterals, and the proliferation marker ki67 was not differentially expressed. In conclusion, compensation for deficiency in Egr-1 function in leukocyte recruitment can presumably be mediated by other transcription factors; however, Egr-1 is indispensable for effective vascular cell cycle progression in arteriogenesis.

MicroRNA-20a promotes proliferation and invasion by directly targeting early growth response 2 in non-small cell lung carcinoma

MicroRNA-20a (miR-20a) serves a notable role in tumor development and progression; it functions differently in different types of malignant tumor, and its role and mechanism in non-small cell lung carcinoma (NSCLC) remains unclear. In the present study, the effects of miR-20a on the proliferation and invasion of NSCLC cells and the underlying mechanisms behind this were investigated. Reverse transcription-quantitative polymerase chain reaction revealed that the expression level of miR-20a was higher in human NSCLC than in normal tissues. Following this, the effect of miR-20a on the proliferation, apoptosis, migration and invasion of NSCLCA-549 cells was further evaluated. In vitro analysis, including a Cell Counting Kit-8, colony formation and Transwell migration assay, indicated that miR-20a-knockdown inhibited the proliferation, invasion and migration, while promoting the cell apoptosis of the A-549 cells. Early growth response 2 (EGR2) protein and mRNA levels were downregulated or upregulated following the overexpression or knockdown of miR-20a, respectively. Dual-luciferase reporter gene assays implied that EGR2 is a direct target gene of miR-20a. The results of the present study indicated that miR-20a may function as an oncomiR in the development of NSCLC by promoting cell viability and motility. The inhibition of miR-20a could even become a novel therapeutic method for the treatment of NSCLC.

Role for Egr1 in the Transcriptional Program Associated with Neuronal Differentiation of PC12 Cells

PC12 cells are a well-established model to study how differences in signal transduction duration can elicit distinct cell behaviors. Epidermal growth factor (EGF) activates transient ERK signaling in PC12 cells that lasts 30–60 min, which in turn promotes proliferation; nerve growth factor (NGF) activates more sustained ERK signaling that lasts 4–6 h, which in turns induces neuronal differentiation. Data presented here extend a previous study by Mullenbrock et al. (2011) that demonstrated that sustained ERK signaling in response to NGF induces preferential expression of a 69-member gene set compared to transient ERK signaling in response to EGF and that the transcription factors AP-1 and CREB play a major role in the preferential expression of several genes within the set. Here, we examined whether the Egr family of transcription factors also contributes to the preferential expression of the gene set in response to NGF. Our data demonstrate that NGF causes transient induction of all Egr family member transcripts, but a corresponding induction of protein was detected for only Egr1 and 2. Chromatin immunoprecipitation experiments provided clearest evidence that, after induction, Egr1 binds 12 of the 69 genes that are preferentially expressed during sustained ERK signaling. In addition, Egr1 expression and binding upstream of its target genes were both sustained in response to NGF versus EGF within the same timeframe that its targets are preferentially expressed. These data thus provide evidence that Egr1 contributes to the transcriptional program activated by sustained ERK signaling in response to NGF, specifically by contributing to the preferential expression of its target genes identified here.

MicroRNA-17-5p promotes gastric cancer proliferation, migration and invasion by directly targeting early growth response 2

MicroRNA-17-5p (miR-17-5p) has previously been reported to play an important role in tumor development and progression. However, it functions differently regarding different kinds of malignant tumor, and its role and mechanism in gastric cancer (GC) still lacks investigation. In this study, we detected the relationship between miR-17-5p and the development of GC by qRT-PCR, and it turned out that the level of miR-17-5p was significantly higher in GC patients than that in normal controls, and the aberrant expression of miR-17-5p was correlated with lymph node metastasis. After that, we examined the effect of miR-17-5p taking on the proliferation, apoptosis, migration and invasion of GC cells and the underlying mechanism. Experiments indicated that knockdown of miR-17-5p inhibited the proliferation, invasion and migration, while promoting apoptosis of SGC7901 cells. Early Growth Response 2 (EGR2) protein or mRNA levels were downregulated or upregulated after overexpression or knockdown of miR-17-5p, respectively. By using dual luciferase assay and Western blot, we identified EGR2 as a functional target of miR-17-5p. As far as we know, this could be the first study to demonstrate that miR-17-5p is associated with tumor stage of GC and that it could possibly become a new therapeutic method for the treatment of GC.

Deletion of miR-150 Exacerbates Retinal Vascular Overgrowth in High-Fat-Diet Induced Diabetic Mice

Diabetic retinopathy (DR) is the leading cause of blindness among American adults above 40 years old. The vascular complication in DR is a major cause of visual impairment, making finding therapeutic targets to block pathological angiogenesis a primary goal for developing DR treatments. MicroRNAs (miRs) have been proposed as diagnostic biomarkers and potential therapeutic targets for various ocular diseases including DR. In diabetic animals, the expression levels of several miRs, including miR-150, are altered. The expression of miR-150 is significantly suppressed in pathological neovascularization in mice with hyperoxia-induced retinopathy. The purpose of this study was to investigate the functional role of miR-150 in the development of retinal microvasculature complications in high-fat-diet (HFD) induced type 2 diabetic mice. Wild type (WT) and miR-150 null mutant (miR-150-/-) male mice were given a HFD (59% fat calories) or normal chow diet. Chronic HFD caused a decrease of serum miR-150 in WT mice. Mice on HFD for 7 months (both WT and miR-150-/-) had significant decreases in retinal light responses measured by electroretinograms (ERGs). The retinal neovascularization in miR-150-/--HFD mice was significantly higher compared to their age matched WT-HFD mice, which indicates that miR-150 null mutation exacerbates chronic HFD-induced neovascularization in the retina. Overexpression of miR-150 in cultured endothelial cells caused a significant reduction of vascular endothelial growth factor receptor 2 (VEGFR2) protein levels. Hence, deletion of miR-150 significantly increased the retinal pathological angiogenesis in HFD induced type 2 diabetic mice, which was in part through VEGFR2.

Early growth response-1 in the pathogenesis of cardiovascular disease

This article reviews the regulatory roles of the immediate-early gene product and prototypic zinc finger transcription factor, early growth response-1 in models of cardiovascular pathobiology, focusing on insights using microRNA, DNAzymes, small hairpin RNA, small interfering RNA, oligonucleotide decoy strategies and mice deficient in early growth response-1.

Guanabenz Downregulates Inflammatory Responses via eIF2α Dependent and Independent Signaling

Integrated stress responses (ISR) may lead to cell death and tissue degeneration via eukaryotic translation initiation factor 2 α (eIF2α)-mediated signaling. Alleviating ISR by modulating eIF2α phosphorylation can reduce the symptoms associated with various diseases. Guanabenz is known to elevate the phosphorylation level of eIF2α and reduce pro-inflammatory responses. However, the mechanism of its action is not well understood. In this study, we investigated the signaling pathway through which guanabenz induces anti-inflammatory effects in immune cells, in particular macrophages. Genome-wide mRNA profiling followed by principal component analysis predicted that colony stimulating factor 2 (Csf2, or GM-CSF as granulocyte macrophage colony stimulating factor) is involved in the responses to guanabenz. A partial silencing of Csf2 or eIF2α by RNA interference revealed that Interleukin-6 (IL6), Csf2, and Cyclooxygenase-2 (Cox2) are downregulated by guanabenz-driven phosphorylation of eIF2α. Although expression of IL1β and Tumor Necrosis Factor-α (TNFα) was suppressed by guanabenz, their downregulation was not directly mediated by eIF2α signaling. Collectively, the result herein indicates that anti-inflammatory effects by guanabenz are mediated by not only eIF2α-dependent but also eIF2α-independent signaling.

Resequencing of early growth response 2 (EGR2) gene revealed a recurrent patient-specific mutation in schizophrenia

Abnormal myelination is considered as part of the pathophysiology of schizophrenia. We resequenced the genomic DNA of the EGR2, which has a specific function in the myelination of peripheral nervous system, in 543 schizophrenic patients and 554 non-psychotic controls. We identified six known SNPs, which were not associated with schizophrenia. Nevertheless, we discovered 24 rare mutations, some of them were patient-specific, including a recurrent mutation (p.P173_Y174insP), which might be associated with the pathogenesis of schizophrenia.

MicroRNA‑20a promotes the proliferation and cell cycle of human osteosarcoma cells by suppressing early growth response 2 expression

MicroRNAs (miRNAs) are crucial in cancer development. However, the underlying mechanisms of miRNAs in osteosarcoma (OS) remain largely uncharacterized. The present study investigated the role of miR‑20a in OS cell proliferation. It was determined that miR‑20a expression is markedly upregulated in OS tissues and cells compared with the matched adjacent normal tissues and h‑FOB human osteoblast cell lines. Ectopic expression of miR‑20a promoted the proliferation and anchorage‑independent growth of OS cells, whereas inhibition of miR‑20a reduced this effect. Bioinformatics analysis further revealed early growth response 2 (EGR2), as a potential target of miR‑20a. Data from luciferase reporter assays showed that miR‑20a directly binds to the 3'‑untranslated region (3'‑UTR) of EGR2 mRNA and represses expression at the transcriptional and translational levels. In functional assays, miR‑20a promoted OS cell proliferation and the cell cycle, which could be suppressed by an inhibitor of miR‑20a. In conclusion, the data provide compelling evidence that miR‑20a functions as an onco‑miRNA, which is important in promoting cell proliferation in OS, and its oncogenic effect is mediated primarily through direct suppression of EGR2 expression.

Triggering receptor expressed on myeloid cells 1 (TREM-1)-mediated Bcl-2 induction prolongs macrophage survival

Triggering receptor expressed on myeloid cells 1 (TREM-1) is a superimmunoglobulin receptor expressed on myeloid cells that plays an important role in the amplification of inflammation. Recent studies suggest a role for TREM-1 in tumor-associated macrophages with relationship to tumor growth and progression. Whether the effects of TREM-1 on inflammation and tumor growth are mediated by an alteration in cell survival signaling is not known. In these studies, we show that TREM-1 knock-out macrophages exhibit an increase in apoptosis of cells in response to lipopolysaccharide (LPS) suggesting a role for TREM-1 in macrophage survival. Specific ligation of TREM-1 with monoclonal TREM-1 (mTREM-1) or overexpression of TREM-1 with adeno-TREM-1 induced B-cell lymphoma-2 (Bcl-2) with depletion of the key executioner caspase-3 prevents the cleavage of poly(ADP-ribose) polymerase. TREM-1 knock-out cells showed lack of induction of Bcl2 with an increase in caspase-3 activation in response to lipopolysaccharide. In addition overexpression of TREM-1 with adeno-TREM-1 led to an increase in mitofusins (MFN1 and MFN2) and knockdown of TREM-1 decreased the expression of mitofusins suggesting that TREM-1 contributes to the maintenance of mitochondrial integrity favoring cell survival. Investigations into potential mechanisms by which TREM-1 alters cell survival showed that TREM-1-induced Bcl-2 in an Egr2-dependent manner. Furthermore, our data shows that expression of Egr2 in response to specific ligation of TREM-1 is ERK mediated. These data for the first time provide novel mechanistic insights into the role of TREM-1 as an anti-apoptotic protein that prolongs macrophage survival.

Lack of association of EGR2 variants with bipolar disorder in Japanese population

The early growth response gene 2 (EGR2) has been recently reported to be associated with bipolar disorder in the Korean population. However replication studies in independent cohorts of same and different ethnicities are essential for establishing the credibility of a genotype-phenotype association. With this notion, in the present study we have performed a replication study of the reported association of SNPs in EGR2 in a case-control study comprising of 867 unrelated Japanese bipolar disorder patients and 895 age-, sex- and ethnicity-matched controls. Results showed no significant differences in allele and genotype frequencies of EGR2 SNPs between bipolar disorder patients and controls and also in a sex-stratified genetic analysis. The haplotype and meta-analyses also showed no significant association with bipolar disorder. In conclusion, this is the first replication study of the previously reported association of EGR2 with bipolar disorder in a larger sample set and the results showed that the EGR2 gene is unlikely to contribute to the susceptibility of bipolar disorder in a Japanese cohort.

Involvement of miR-20a in promoting gastric cancer progression by targeting early growth response 2 (EGR2)

Gastric cancer (GC) is one of the most common cancers, with high incidences in East Asia. microRNAs (miRNAs) play essential roles in the carcinogenesis of GC. miR-20a was elevated in GC, while the potential function of miR-20a was poorly understood. miR-20a expression was examined in GC tissues and cell lines. The effects of miR-20a on the growth, migration, invasion, and chemoresistance of GC cells were examined. Luciferase reporter assay and Western blot were used to screen the target of miR-20a. miR-20a was increased in GC tissues and cell lines. miR-20a promoted the growth, migration and invasion of GC cells, enhanced the chemoresistance of GC cells to cisplatin and docetaxel. Luciferase activity and Western blot confirmed that miR-20a negatively regulated EGR2 expression. Overexpression of EGR2 significantly attenuated the oncogenic effect of miR-20a. miR-20a was involved in the carcinogenesis of GC through modulation of the EGR2 signaling pathway.

Mast cell FcεRI-induced early growth response 2 regulates CC chemokine ligand 1-dependent CD4+ T cell migration

Mast cells are well positioned in host tissue for detecting environmental signals, including allergens, leading to activation of the high-affinity IgE receptor FcεRI, and initiating a signaling cascade that perpetuates the production of biologically potent mediators, including chemokines. We have identified a novel target of mast cell FcεRI activity in the transcription factor early growth response 2 (Egr2) and sought to characterize its function therein. Egr2 was transiently activated following FcεRI-mediated signaling, targeted the promoter of the chemokine CCL1, and was critical for allergen-induced mast cell CCL1 production. Egr2-deficient mast cells were incapable of directing CD4(+) T cell migration via the CCL1-CCR8 axis. In a model of allergic asthma, reconstitution of mast cell-deficient mice with Egr2-deficient mast cells demonstrated that mast cell Egr2 was essential for migration of CD4(+) T cells to the inflamed lung. These findings position Egr2 as a critical regulator of mast cell-directed CD4(+) T cell migration.

Involvement of early growth response-2 (Egr-2) in lipopolysaccharide-induced neuroinflammation

Early growth response-2 (Egr-2) protein is a transcription factor, which belongs to Egr family which involve in modulating the peripheral immune response, by means of the induction of differentiation of lymphocyte precursors, activation of T and B cells. Egr-2 plays essential roles in peripheral nerve myelination, adipogenesis, tissue repair and fibrosis, immune tolerance; however, its regulation and role in central nervous system (CNS) remain poorly understood. In contrast to Egr-1, which has been extensively investigated, the regulation and function of Egr-2 remains less well characterized. To elaborate whether Egr-2 was involved in CNS injury, we performed a neuroinflammatory model by lipopolysaccharide (LPS) lateral ventral injection in adult rats. Egr-2 expression was strongly induced in active glia cells (astrocytes and microglias) in inflamed brain cortex. In vitro studies indicated that the upregulation of Egr-2 may be involved in the subsequent glia cellular activation following LPS exposure; and knock down of Egr-2 in primary mixed glial cultures (MGC) by siRNA showed that Egr-2 promoted the synthesis of TNF-α. Collectively, these results suggested Egr-2 may be important in host defense in CNS immune response, which might provide a potential target to the treatment of neuroinflammation.

Ablation of Egr2-positive cells in male mouse anterior pituitary leads to atypical isolated GH deficiency

In this study, we have investigated the expression and function of the transcription factor early growth response factor 2 (Egr2)/Krox20 in the developing anterior pituitary. Egr2 is initially expressed in all differentiating hormonal cells types, but its expression is mostly restricted to the somatotroph lineage after birth. Egr2 knockout results in anterior pituitary hypoplasia. However, the analysis of a conditional mutant demonstrates that this phenotype does not originate from a lack of Egr2 expression in the pituitary. Using an Egr2 allele driving a Cre-activable toxin gene, we performed a genetic ablation of Egr2-positive cells in the pituitary. During the postnatal period, this ablation leads to specific and progressive depletion of the somatotroph population, creating a novel model of early-onset isolated GH deficiency (GHD). Mutant animals were subjected to a complete metabolic analysis, revealing atypical and expected features. Consistent with an adult-onset isolated GHD model, mutant animals are hypoglycemic and display increased insulin sensitivity and glucose clearance. This latter phenotype is in contrast to the glucose intolerance observed in another early-onset GHD model. Surprisingly, increased insulin sensitivity is not accompanied by a modified balance between fat and lean tissues, but by reduced metabolic adaptability between glucose and lipid oxidation conditions. This suggests that the relationship between these metabolic features and insulin sensitivity should be reconsidered. In conclusion, our mutant may be a valuable genetic model with which to study the effects of long-term GH deficiency, in conditions of normal pancreatic function and unaffected balance between fat and glucose metabolism.

IRES-dependent translation of egr2 is induced under inflammatory conditions

Adjusting translation is crucial for cells to rapidly adapt to changing conditions. While pro-proliferative signaling via the PI3K-mTOR-pathway is known to induce cap-dependent translation, stress conditions, such as nutrient deprivation or hypoxia often activate alternative modes of translation, e.g., via internal ribosome entry sites (IRESs). As the effects of inflammatory conditions on translation are only poorly characterized, we aimed at identifying translationally deregulated targets in inflammatory settings. For this purpose, we cocultured breast tumor cells with conditioned medium of activated monocyte-derived macrophages (CM). Polysome profiling and microarray analysis identified early growth response-2 (egr2) to be regulated at the level of translation. Using bicistronic reporter assays, we found that egr2 contains an IRES within its 5' UTR, which facilitated enhanced translation upon CM treatment. We further provide evidence that the activity of egr2-IRES was induced by IL-1β and p38-MAPK signaling. In addition, we identified several potential IRES trans-acting factors (ITAFs) such as polypyrimidine tract binding protein (PTB) and hnRNP-A1 that directly bind to the egr2-5'UTR. In summary, our data provide evidence that egr2 expression is translationally regulated via an IRES element, which is responsive to an inflammatory environment.

Charcot-Marie-Tooth neuropathy due to a novel EGR2 gene mutation with mild phenotype--usefulness of human mapping chip linkage analysis in a Czech family

Charcot-Marie-Tooth neuropathies (CMT) are a group of clinically and genetically heterogeneous disorders of the peripheral nervous system. Selection of candidate disease genes for mutation analysis is sometimes difficult since more than 40 genes and loci are known to be associated with CMT neuropathies. Hence a Czech family Cz-CMT with demyelinating type of autosomal dominant CMT disease was investigated by genome-wide linkage analysis by means of single-nucleotide polymorphism (SNP) arrays. Among 35 regions with linkage, five carried known CMT genes. In the final result a novel early growth response 2 - missense mutation c.1235 A>G, p.Glu412Gly was found. Surprisingly, the more severely affected proband carried an additional heterozygous myelin protein zero variant p.Asp246Asn detected previously, which may modify the phenotype. However, this MPZ variant is benign in heterozygous state alone, because it is also carried by the patient's healthy father.

Regulation of connexin expression by transcription factors and epigenetic mechanisms

Gap junctions are specialized cell-cell junctions that directly link the cytoplasm of neighboring cells. They mediate the direct transfer of metabolites and ions from one cell to another. Discoveries of human genetic disorders due to mutations in gap junction protein (connexin [Cx]) genes and experimental data on connexin knockout mice provide direct evidence that gap junctional intercellular communication is essential for tissue functions and organ development, and that its dysfunction causes diseases. Connexin-related signaling also involves extracellular signaling (hemichannels) and non-channel intracellular signaling. Thus far, 21 human genes and 20 mouse genes for connexins have been identified. Each connexin shows tissue- or cell-type-specific expression, and most organs and many cell types express more than one connexin. Connexin expression can be regulated at many of the steps in the pathway from DNA to RNA to protein. In recent years, it has become clear that epigenetic processes are also essentially involved in connexin gene expression. In this review, we summarize recent knowledge on regulation of connexin expression by transcription factors and epigenetic mechanisms including histone modifications, DNA methylation, and microRNA. This article is part of a Special Issue entitled: The communicating junctions, roles and dysfunctions.

The early growth response gene Egr2 (Alias Krox20) is a novel transcriptional target of transforming growth factor-β that is up-regulated in systemic sclerosis and mediates profibrotic responses

Although the early growth response-2 (Egr-2, alias Krox20) protein shows structural and functional similarities to Egr-1, these two related early-immediate transcription factors are nonredundant. Egr-2 plays essential roles in peripheral nerve myelination, adipogenesis, and immune tolerance; however, its regulation and role in tissue repair and fibrosis remain poorly understood. We show herein that transforming growth factor (TGF)-β induced a Smad3-dependent sustained stimulation of Egr2 gene expression in normal fibroblasts. Overexpression of Egr-2 was sufficient to stimulate collagen gene expression and myofibroblast differentiation, whereas these profibrotic TGF-β responses were attenuated in Egr-2-depleted fibroblasts. Genomewide transcriptional profiling revealed that multiple genes associated with tissue remodeling and wound healing were up-regulated by Egr-2, but the Egr-2-regulated gene expression profile overlapped only partially with the Egr-1-regulated gene profile. Levels of Egr-2 were elevated in lesional tissue from mice with bleomycin-induced scleroderma. Moreover, elevated Egr-2 was noted in biopsy specimens of skin and lung from patients with systemic sclerosis. These results provide the first evidence that Egr-2 is a functionally distinct transcription factor that is both necessary and sufficient for TGF-β-induced profibrotic responses and is aberrantly expressed in lesional tissue in systemic sclerosis and in a murine model of scleroderma. Together, these findings suggest that Egr-2 plays an important nonredundant role in the pathogenesis of fibrosis. Targeting Egr-2 might represent a novel therapeutic strategy to control fibrosis.

Transcriptional modulation induced by ionizing radiation: p53 remains a central player

The cellular response to DNA damage is vital for maintaining genomic stability and preventing undue cell death or cancer formation. The DNA damage response (DDR), most robustly mobilized by double-strand breaks (DSBs), rapidly activates an extensive signaling network that affects numerous cellular systems, leading to cell survival or programmed cell death. A major component of the DDR is the widespread modulation of gene expression. We analyzed together six datasets that probed transcriptional responses to ionizing radiation (IR) - our novel experimental data and 5 published datasets - to elucidate the scope of this response and identify its gene targets. According to the mRNA expression profiles we recorded from 5 cancerous and non-cancerous human cell lines after exposure to 5 Gy of IR, most of the responses were cell line-specific. Computational analysis identified significant enrichment for p53 target genes and cell cycle-related pathways among groups of up-regulated and down-regulated genes, respectively. Computational promoter analysis of the six datasets disclosed that a statistically significant number of the induced genes contained p53 binding site signatures. p53-mediated regulation had previously been documented for subsets of these gene groups, making our lists a source of novel potential p53 targets. Real-time qPCR and chromatin immunoprecipitation (ChIP) assays validated the IR-induced p53-dependent induction and p53 binding to the respective promoters of 11 selected genes. Our results demonstrate the power of a combined computational and experimental approach to identify new transcriptional targets in the DNA damage response network.

Early growth response transcription factors and the modulation of immune response: implications towards autoimmunity

Early Growth Response (EGR) zinc finger transcription factors are induced under diverse mitogenic signals on different cell types such as lymphocytes. Their genetic expression does not require de novo protein synthesis, which suggests its role as immediate response mediators between cell surface receptor signaling and gene expression regulation. EGR factors are involved in modulating the immune response, by means of the induction of differentiation of lymphocyte precursors, activation of T and B cells, as well as their involvement in central and peripheral tolerance. The maturation state, particularly for B cells, and signaling through the T or B cell receptors seems to be quite relevant for the induction of the expression of these transcription factors. EGR-1 functions as a positive regulatory factor for B and T cells mediated by transcriptional regulation of key cytokines and costimulatory molecules, and its interaction with NFAT. On the opposite, EGR-2 and 3 act as negative regulators involved in anergy induction and apoptosis. EGR-2 and 3 deficiency has been related to the development of lupus like disease in murine models. The deficiency of these transcription factors has been associated to deficient Cbl-b expression, a resistant to anergy phenotype, and expansion of effector and activated T cells.

The HECT-type E3 ubiquitin ligase AIP2 inhibits activation-induced T-cell death by catalyzing EGR2 ubiquitination

E3 ubiquitin ligases, which target specific molecules for proteolytic destruction, have emerged as key regulators of immune functions. Several E3 ubiquitin ligases, including c-Cbl, Cbl-b, GRAIL, Itch, and Nedd4, have been shown to negatively regulate T-cell activation. Here, we report that the HECT-type E3 ligase AIP2 positively regulates T-cell activation. Ectopic expression of AIP2 in mouse primary T cells enhances their proliferation and interleukin-2 production by suppressing the apoptosis of T cells. AIP2 interacts with and promotes ubiquitin-mediated degradation of EGR2, a zinc finger transcription factor that has been found to regulate Fas ligand (FasL) expression during activation-induced T-cell death. Suppression of AIP2 expression by small RNA interference upregulates EGR2, inhibits EGR2 ubiquitination and FasL expression, and enhances the apoptosis of T cells. Therefore, AIP2 regulates activation-induced T-cell death by suppressing EGR2-mediated FasL expression via the ubiquitin pathway.

The transcription factors Egr1 and Egr2 have opposing influences on adipocyte differentiation

The zinc finger-containing transcription factors Egr1 (Krox24) and Egr2 (Krox20) have been implicated in the proliferation and differentiation of many cell types. Egr2 has earlier been shown to play a positive role in adipocyte differentiation, but the function of Egr1 in this context is unknown. We compared the roles of Egr1 and Egr2 in the differentiation of murine 3T3-L1 adipocytes. Egr1 protein was rapidly induced after addition of differentiation cocktail, whereas Egr2 protein initially remained low before increasing on days 1 and 2, concomitant with the disappearance of Egr1. In marked contrast to the effects of Egr2, differentiation was inhibited by ectopic expression of Egr1 and potentiated by knockdown of Egr1. The pro-adipogenic effects of Egr1 knockdown were particularly notable when isobutylmethylxanthine (IBMX) was omitted from the differentiation medium. However, knockdown of Egr1 did not affect CCAAT/enhancer binding protein (C/EBP)beta protein expression or phosphorylation of CREB Ser133. Further, Egr1 did not directly affect the activity of promoters for the master adipogenic transcription factors, C/EBPalpha or peroxisome proliferator-activated receptor-gamma2, as assessed in luciferase reporter assays. These data indicate that Egr1 and Egr2 exert opposing influences on adipocyte differentiation and that the careful regulation of both is required for maintaining appropriate levels of adipogenesis. Further, the pro-differentiation effects of IBMX involve suppression of the inhibitory influence of Egr1.

Krox20 controls the transcription of its various targets in the developing hindbrain according to multiple modes

The zinc finger transcription factor Krox20 plays an essential role in the vertebrate hindbrain segmentation process. It positively or negatively controls a large variety of other regulatory genes, coordinating delimitation of segmental territories, specification of their identity, and maintenance of their integrity. We have investigated the molecular mechanisms of Krox20 transcriptional control by performing a detailed structure-function analysis of the protein in the developing chick hindbrain. This revealed an unsuspected diversity in the modes of action of a transcription factor in a single tissue, since regulation of each of the five tested target genes requires different parts of the protein and/or presumably different co-factors. The multiplicity of Krox20 functions might rely on this diversity. Investigation of known Krox20 co-factors was initiated in relation to this analysis. Nab was shown to act as a negative feedback modulator of the different Krox20 activating functions in the hindbrain. HCF-1 was found to bind to a Krox20 N-terminal region, which was shown to rely on multiple elements, including acidic domains, to convey Nab activation and Krox20 autoregulation.

Heroin self-administration: II. CNS gene expression following withdrawal and cue-induced drug-seeking behavior

In the accompanying paper, we described incubation of heroin-seeking behavior in rats following 14 days of abstinence. To gain an understanding of genomic changes that accompany this behavioral observation, we measured the expression of genes previously reported to respond to drugs of abuse. Specifically, after 1 or 14 days of abstinence, mRNA expression was measured for 11 genes in the medial prefrontal cortex (mPFC) and nucleus accumbens (NAc) immediately following a single 90 min extinction session. Additionally, the role of contingency was examined in control rats that received yoked, response-independent heroin administration. Gene expression was quantified by real-time quantitative PCR. Expression of five genes (Arc, EGR1, EGR2, Fos, and Homer1b/c) was changed in the mPFC. EGR1 and EGR2 expression was increased following the 90 min extinction session in a contingency-specific manner and this increase persisted through the 14 days of abstinence. Fos expression was also increased after 1 and 14 days of abstinence, but at 14 days this increase was response-independent (i.e., it occurred in both the rats with a history of heroin self-administration and in the yoked controls). Arc expression increased following the extinction session only in rats with a history of heroin self-administration and only when tested following 1, but not 14, days of abstinence. Homer 1 b/c decreased after 14 days of enforced abstinence in rats that received non-contingent heroin. Expression of only a single gene (EGR2) was increased in the NAc. These data demonstrate that behavioral incubation is coincident with altered levels of specific transcripts and that this response is contingently-specific. Moreover, EGR1 and EGR2 are specifically upregulated in self-administering rats following extinction and this finding persists through 14 days of abstinence, suggesting that these genes are particularly associated with the incubation phenomenon. These latter observations of persistent changes in gene expression following abstinence may reflect molecular correlates of relapse liability.

Charcot-Marie-Tooth disease: a clinico-genetic confrontation

Charcot-Marie-Tooth disease (CMT) is the most common neuromuscular disorder. It represents a group of clinically and genetically heterogeneous inherited neuropathies. Here, we review the results of molecular genetic investigations and the clinical and neurophysiological features of the different CMT subtypes. The products of genes associated with CMT phenotypes are important for the neuronal structure maintenance, axonal transport, nerve signal transduction and functions related to the cellular integrity. Identifying the molecular basis of CMT and studying the relevant genes and their functions is important to understand the pathophysiological mechanisms of these neurodegenerative disorders, and the processes involved in the normal development and function of the peripheral nervous system. The results of molecular genetic investigations have impact on the appropriate diagnosis, genetic counselling and possible new therapeutic options for CMT patients.

Mechanisms of disease: inherited demyelinating neuropathies--from basic to clinical research

The hereditary motor and sensory neuropathies (also known as Charcot-Marie-Tooth disease or CMT) are characterized by a length-dependent loss of axonal integrity in the PNS, which leads to progressive muscle weakness and sensory deficits. The 'demyelinating' neuropathies (CMT disease types 1 and 4) are genetically heterogeneous, but their common feature is that the primary defect perturbs myelination. As we discuss in this Review, several new genes associated with CMT1 and CMT4 have recently been identified. The emerging view is that a range of different subcellular defects in Schwann cells can cause axonal loss, which represents the final common pathway of all CMT disease and is independent of demyelination. We propose that Schwann cells provide a first line of axonal neuroprotection. A better understanding of axon-glia interactions should open the way to therapeutic interventions for demyelinating neuropathies. Transgenic animal models have become essential for dissecting CMT disease mechanisms and exploring novel therapies.

Early growth response 1 mediates the systemic and hepatic inflammatory response initiated by hemorrhagic shock

Hemorrhagic shock (HS) is a major cause of morbidity and mortality in trauma patients. The early growth response 1 (Egr-1) transcription factor is induced by a variety of cellular stresses, including hypoxia, and may function as a master switch to trigger the expression of numerous key inflammatory mediators. We hypothesized that HS would induce hepatic expression of Egr-1 and that Egr-1 upregulates the inflammatory response after HS. The Egr-1 mice and wild-type (WT) controls (n>or=5 for all groups) were subjected to HS alone or HS followed by resuscitation (HS/R). Other mice were subjected to a sham procedure which included general anesthesia and vessel cannulation but no shock (sham). After the HS, HS/R, or sham procedures, mice were euthanized for determination of serum concentrations of interleukin (IL) 6, IL-10, and alanine aminotransferase. Northern blot analysis was performed to evaluate Egr-1 messenger RNA (mRNA) expression. Liver whole cell lysates were evaluated for Egr-1 protein expression by Western blot analysis. Hepatic expression of IL-6, granulocyte colony-stimulating factor, and intracellular adhesion molecule 1 mRNA was determined by semiquantitative reverse transcriptase-polymerase chain reaction. The Egr-1 DNA binding was assessed using the electrophoretic mobility shift assay. Hemorrhagic shock results in a rapid and transient hepatic expression of Egr-1 mRNA in WT mice by 1 h, whereas protein and DNA binding activity was evident by 2.5 h. The Egr-1 mRNA expression diminished after 4 h of resuscitation, whereas Egr-1 protein expression and DNA binding activity persisted through resuscitation. The Egr-1 mice exhibited decreased levels of hepatic inflammatory mediators compared with WT controls with a decrease in hepatic mRNA levels of IL-6 by 42%, granulocyte colony-stimulating factor by 39%, and intracellular adhesion molecule 1 by 43%. Similarly, Egr-1 mice demonstrated a decreased systemic inflammatory response and hepatic injury after HS/R compared with their WT counterparts. Early growth response 1 is rapidly upregulated in the liver during and after resuscitation from HS. Our results showing a blunted inflammatory response in Egr-1 mice provides evidence that Egr-1 functions as a proximal signal transduction mechanism responding to shock by amplifying the systemic inflammatory response.

Microenvironmental Regulation of Membrane Type 1 Matrix Metalloproteinase Activity in Ovarian Carcinoma Cells via Collagen-induced EGR1 Expression

Late stage ovarian cancer is characterized by disseminated intraperitoneal metastasis as secondary lesions anchor in the type I and III collagen-rich submesothelial matrix. Ovarian carcinoma cells preferentially adhere to interstitial collagen, and collagen-induced integrin clustering up-regulates the expression of the transmembrane collagenase membrane type 1 matrix metalloproteinase (MT1-MMP). Collagenolytic activity is important in intraperitoneal metastasis, potentiating invasion through the mesothelial cell layer and colonization of the submesothelial collagen-rich matrix. The objective of this study was to elucidate a potential mechanistic link between collagen adhesion and MT1-MMP expression. Our results indicate that culturing cells on three-dimensional collagen gels, but not thin layer collagen or synthetic three-dimensional hydrogels, results in rapid induction of the transcription factor EGR1. Integrin signaling through a SRC kinase-dependent pathway is necessary for EGR1 induction. Silencing of EGR1 expression using small interfering RNA abrogated collagen-induced MT1-MMP expression and inhibited cellular invasion of three-dimensional collagen gels. These data support a model for intraperitoneal metastasis wherein collagen adhesion and clustering of collagen binding integrins activates integrin-mediated signaling via SRC kinases to induce expression of EGR1, resulting in transcriptional activation of the MT1-MMP promoter and subsequent MT1-MMP-catalyzed collagen invasion. This model highlights the role of unique interactions between ovarian carcinoma cells and interstitial collagens in the ovarian tumor microenvironment in inducing gene expression changes that potentiate intraperitoneal metastatic progression.

The Inherited Neuropathies

Neuropathy is one of the most common referrals to neurologic clinics. Patients often undergo extensive testing for acquired etiologies; inherited causes are common. Increasingly, genetic causes are becoming known and commercial testing available. The rate of recent discovery has been rapid and relates to the extent of single gene disorders of nerve, the ease of peripheral nervous system functional examination, and readily accessible pathologic tissue. Foremost in the rate of recent discoveries is the work and tools of the human genome project. the rapidity of the ongoing discovery requires clinicians to be familiar with molecular biologic discoveries and consider wisely which testing should be performed.

A two-step, PU.1-dependent mechanism for developmentally regulated chromatin remodeling and transcription of the c-fms gene

Hematopoietic stem cells and multipotent progenitors exhibit low-level transcription and partial chromatin reorganization of myeloid cell-specific genes including the c-fms (csf1R) locus. Expression of the c-fms gene is dependent on the Ets family transcription factor PU.1 and is upregulated during myeloid differentiation, enabling committed macrophage precursors to respond to colony-stimulating factor 1. To analyze molecular mechanisms underlying the transcriptional priming and developmental upregulation of the c-fms gene, we have utilized myeloid progenitors lacking the transcription factor PU.1. PU.1 can bind to sites in both the c-fms promoter and the c-fms intronic regulatory element (FIRE enhancer). Unlike wild-type progenitors, the PU.1(-/-) cells are unable to express c-fms or initiate macrophage differentiation. When PU.1 was reexpressed in mutant progenitors, the chromatin structure of the c-fms promoter was rapidly reorganized. In contrast, assembly of transcription factors at FIRE, acquisition of active histone marks, and high levels of c-fms transcription occurred with significantly slower kinetics. We demonstrate that the reason for this differential activation was that PU.1 was required to promote induction and binding of a secondary transcription factor, Egr-2, which is important for FIRE enhancer activity. These data suggest that the c-fms promoter is maintained in a primed state by PU.1 in progenitor cells and that at FIRE PU.1 functions with another transcription factor to direct full activation of the c-fms locus in differentiated myeloid cells. The two-step mechanism of developmental gene activation that we describe here may be utilized to regulate gene activity in a variety of developmental pathways.

Gene expression in fibroadenomas of the rat mammary gland in contrast to spontaneous adenocarcinomas and normal mammary gland

Fibroadenomas are considered a benign lesion in rodent carcinogenicity studies. However, the entity adenocarcinoma arising in fibroadenoma does exist and in humans there is evidence of certain forms of fibroadenomas to confer greater risk of subsequent breast cancer. In this study, we aim to elucidate the molecular features of both spontaneous fibroadenomas and adenocarcinomas. The gene expression of the two tumour types is examined and compared to mammary gland in the same developmental state and examined for similarities which might indicate common molecular pathways. In the present study no similarities were discovered. We conclude that in the tumours examined here, no progression to adenocarcinoma is likely. Further studies are needed, examining a greater number of tumours and including cases of adenocarcinoma arising in fibroadenoma.

Genetic effects of anorganic bovine bone (Bio-Oss®) on osteoblast-like MG63 cells

Bio-Oss (Geistlich, Wolhusen, Switzerland) is composed by anorganic bovine bone and is widely used in several bone regeneration procedures in oral surgery. How this biomaterial alters osteoblast gene expression to promote bone formation is poorly understood. We therefore attempted to address this question by using microarray techniques to identify genes that are differentially regulated in osteoblasts exposed to Bio-Oss. By using DNA microarrays containing 20,000 genes, we identified in osteoblast-like cells line (MG-63) cultured with Bio-Oss several genes which expression was significantly up- and down-regulated. The differentially expressed genes cover a broad range of functional activities: (a) signaling transduction, (b) transcription, (c) cell cycle regulation, (d) vesicular transport, (e) apoptosis, and (f) immunity. These results could explain the reported bioaffinity of Bio-Oss to host animals, its biological affinity to osteogenic cells and its capability to stimulate osteoblastic differentiation. The data reported are, to our knowledge, the first genetic portrait of Bio-Oss effects. They can be relevant to our improved understanding of the molecular mechanism underlying bone regenerative procedures and as a model for comparing other materials with similar clinical effects.

Regulation of connexin expression

Gap junctions contain cell-cell communicating channels that consist of multimeric proteins called connexins and mediate the exchange of low-molecular-weight metabolites and ions between contacting cells. Gap junctional communication has long been hypothesized to play a crucial role in the maintenance of homeostasis, morphogenesis, cell differentiation, and growth control in multicellular organisms. The recent discovery that human genetic disorders are associated with mutations in connexin genes and experimental data on connexin knockout mice have provided direct evidence that gap junctional communication is essential for tissue functions and organ development. Thus far, 21 human genes and 20 mouse genes for connexins have been identified. Each connexin shows tissue- or cell-type-specific expression, and most organs and many cell types express more than one connexin. Cell coupling via gap junctions is dependent on the specific pattern of connexin gene expression. This pattern of gene expression is altered during development and in several pathological conditions resulting in changes of cell coupling. Connexin expression can be regulated at many of the steps in the pathway from DNA to RNA to protein. However, transcriptional control is one of the most important points. In this review, we summarize recent knowledge on transcriptional regulation of connexin genes by describing the structure of connexin genes and transcriptional factors that regulate connexin expression.

Novel EGR2 mutation R359Q is associated with CMT type 1 and progressive scoliosis

Mutations in the early growth response 2 gene (EGR2) cause demyelinating neuropathies differing in severity and age of onset. We tested 46 unrelated Czech patients with dominant or sporadic demyelinating CMT neuropathy for mutations in the EGR2 gene. One novel de-novo mutation (Arg359Gln, R359Q) was identified in heterozygous state in a patient with a typical CMT1 phenotype, progressive moderate thoracolumbar scoliosis and without clinical signs of cranial nerve dysfunction. This patient is presently less affected compared to previously described Dejerine-Sottas neuropathy (DSN) patients carrying another substitution at codon 359 (Arg359Trp, R359W). This report shows that EGR2 mutations are rare in Czech patients with demyelinating type of CMT and suggests that different substitutions at codon 359 of EGR2 can cause significantly different phenotypes.

Charcot-Marie-Tooth disease (hereditary motor sensory neuropathies) and hereditary sensory and autonomic neuropathies

BACKGROUND

Since the description of Charcot-Marie-Tooth disease over a century ago. it has now been recognized that these conditions are not caused by generalized metabolic defects but rather have various discrete genetic origins. These disorders can also have variable phenotypes due to dysfunction of peripheral nerve axons or their myelin due to the genetic defects that affect the formation of specific nerve proteins.

REVIEW SUMMARY

This article summarizes the clinical presentation of various phenotypes of the hereditary motor sensory neuropathies and the hereditary sensory and autonomic neuropathies, genetic mutations, and their relevant protein products. Proper identification of the genetic defects provides the opportunity for better genetic counseling and hopefully therapies in the future.

Mesencephalic Trigeminal Nucleus Development Is Dependent on Krox-20 Expression

Krox-20, a C2H2-type zinc-finger transcription factor, plays an important role in rhombomere development. This study reveals that the Krox-20 null mutation impacts the development of mesencephalic trigeminal (Me5) neurons, a cell group traditionally thought to emerge from the mesencephalon. Based on cell counting studies, we show that Krox-20 null mutants have twice as many Me5 neurons relative to wildtypes at E15, but by birth have half the number of Me5 cells as wildtypes. TUNEL studies reveal a period of increased apoptosis from E17-P0 in mutants. The mutation does not result in differences in Me5 cell size, morphology, gene expression or peripheral projection patterns between genotypes, as demonstrated by retrograde tracing and Brn3a immunohistochemistry. The data suggest that Krox-20 regulates the period and extent of Me5 apoptosis, impacting the final number of Me5 neurons. The loss of Me5 in Krox-20-/- mice may highlight species-specific differences in the origin of these cells.

Regulation of expression of the early growth response gene-1 (EGR-1) in malignant and benign cells of the prostate

BACKGROUND

Expression of the early growth response gene-1 (EGR-1) is elevated in prostate cancer and correlates with tumor progression. This study provides insight into the mechanism(s) that regulate EGR-1 expression and activity in malignant and benign prostate cells.

METHODS

Western blotting and in vitro pulse labeling were used to examine EGR-1 protein levels and half-life in malignant (PC-3) and benign (BPH-1) prostate cell lines. EGR-1 functional ability was assessed by transient transfections with an EGR-1 promoter driven luciferase plasmid and electromobility shift assays (EMSAs) to assess DNA binding of the EGR-1 protein. Protein levels of casein kinase II (CKII) were evaluated by Western blotting.

RESULTS

PC-3 cells maintain high steady-state levels of EGR-1 protein, in part due to a longer half-life of EGR-1 protein. BPH-1 cells responded to mitogenic stimuli with increased EGR-1 protein levels, and enhanced transcriptional activity. In contrast, PC-3 cells showed no response to stimuli. DNA binding of EGR-1 was higher in BPH-1 cells than in PC-3 cells. This appears to be related to the heavily phosphorylated state of EGR-1 in PC-3 cells which is correlated with increased levels of CKII found in these cells.

CONCLUSIONS

PC-3 cells maintain a long lasting, heavily phosphorylated pool of EGR-1, which binds poorly to DNA and responds poorly to mitogenic stimulus. BPH-1 cells, in contrast, maintain a more responsive, less phosphorylated EGR-1 pool. These findings suggest that EGR-1 expression and activity is differentially regulated in PC-3 and BPH-1 cell lines.

GeneChip analyses of global transcriptional responses of murine macrophages to the lethal toxin of Bacillus anthracis

We performed GeneChip analyses on RNA from Bacillus anthracis lethal toxin (LeTx)-treated RAW 264.7 murine macrophages to investigate global effects of anthrax toxin on host cell gene expression. Stringent analysis of data revealed that the expression of several mitogen-activated protein kinase kinase-regulatory genes was affected within 1.5 h post-exposure to LeTx. By 3.0 h, the expression of 103 genes was altered, including those involved in intracellular signaling, energy production, and protein metabolism.

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.

Anti-tumor effect of pEgr-IFNγ gene-radiotherapy in B16 melanoma-bearing mice

AIM: To construct a pEgr-IFNγ plasmid and to investigate its expression properties of interferon-γ (INF-γ ) induced by irradiation and the effect of gene-radiotherapy on the growth of melanoma.

METHODS: A recombined plasmid, pEgr-IFNγ , was constructed and transfected into B16 cell line with lipofectamine. The expression properties of pEgr-IFNγ were investigated by ELISA. Then, a B16 melanoma-bearing model was established in mice, and the plasmid was injected into the tumor tissue. The tumor received 20 Gy X-ray irradiation 36 h after injection, and IFN-γ expression was detected from the tumor tissue. A tumor growth curve at different time points was determined.

RESULTS: The eukaryotic expression vector, pEgr-IFNγ , was successfully constructed and transfected into B16 cells. IFN-γ expression was significantly increased in transfected cells after X-ray irradiation in comparison with 0 Gy group (77.73-94.60 pg/mL, P < 0.05-0.001), and was significantly higher at 4 h and 6 h than that of control group after 2 Gy X-ray irradiation (78.90-90.00 pg/mL, P < 0.01-0.001). When the transfected cells were given 2 Gy irradiation 5 times at an interval of 24 h, IFN-γ expression decreased in a time-dependent manner. From d 3 to d 15 after IFNγ gene-radiotherapy, the tumor growth was significantly slower than that after irradiation or gene therapy alone.

CONCLUSION: The anti-tumor effect of pEgr-IFNγ gene-radiotherapy is better than that of genetherapy or radiotherapy alone for melanoma. These results may establish an important experimental basis for gene-radiotherapy of cancer.