Two different transcription factors discriminate the -315C>T polymorphism of the Fc epsilon RI alpha gene: binding of Sp1 to -315C and of a high mobility group-related molecule to -315T

Fc Receptor Variants and Disease: A Crucial Factor to Consider in the Antibody Therapeutics in Clinic

The fragment crystallizable (Fc) domain of antibodies is responsible for their protective function and long-lasting serum half-life via Fc-mediated effector function, transcytosis, and recycling through its interaction with Fc receptors (FcRs) expressed on various immune leukocytes, epithelial, and endothelial cells. Therefore, the Fc-FcRs interaction is a control point of both endogenous and therapeutic antibody function. There are a number of reported genetic variants of FcRs, which include polymorphisms in (i) extracellular domain of FcRs, which change their affinities to Fc domain of antibodies; (ii) both cytoplasmic and intracellular domain, which alters the extent of signal transduction; and (iii) the promoter region of the FcRs gene, which affects the expression level of FcRs, thus being associated with the pathogenesis of disease indications. In this review, we firstly describe the correlation between the genetic variants of FcRs and immunological disorders by individual differences in the extent of FcRs-mediated regulations. Secondly, we discuss the influence of the genetic variants of FcRs on the susceptibility to infectious diseases or cancer in the perspective of FcRs-induced effector functions. Overall, we concluded that the genetic variants of FcRs are one of the key elements in the design of antibody therapeutics due to their variety of clinical outcomes among individuals.

Elements of Immunoglobulin E Network Associate with Aortic valve Area in Patients with Acquired Aortic Stenosis

Allergic mechanisms are likely involved in atherosclerosis and its clinical presentations, such as coronary artery disease (CAD). It has been previously reported that CAD severity associates with serum levels of immunoglobulin E (IgE), the molecule that, along with its high-affinity receptor (FcԑRI), plays a central role in allergic reactions. Considering multiple pathophysiological similarities between atherosclerosis and acquired aortic (valve) stenosis (AS), we speculated that allergic pathways could also contribute to the AS mechanisms and grading. To validate this hypothesis, we first checked whether total serum IgE levels associate with echocardiographic markers of AS severity. Having found a positive correlation between serum IgE and aortic valve area (AVA), we further speculated that also total IgE-determining genetic polymorphisms in FCER1A, a locus encoding an allergen-biding FcԑRI subunit, are related to acquired AS severity. Indeed, the major allele of rs2251746 polymorphism, known to associate with higher IgE levels, turned out to correlate with larger AVA, a marker of less severe AS. Our findings surprisingly suggest a protective role of IgE pathways against AS progression. IgE-mediated protective mechanisms in AS require further investigations.

Interaction between functional polymorphisms in FCER1A and TLR2 and the severity of atopic dermatitis

Dendritic cell toll-like receptors (TLRs) and the high-affinity immunoglobulin E (IgE) receptor (FcεRI) may biologically interact with regard to atopic dermatitis (AD) development and, especially, severity. Our aim here was to test if such interaction can be detected on the genetic level. The combined effect of the TLR2 gene (TLR2) rs4696480 and the FcεRI α-chain gene (FCER1A) rs2252226 and rs2251746 polymorphisms on the AD severity as measured by SCORAD was assessed. The FCER1A rs2252226 and TLR2 rs4696480 polymorphisms interacted with regard to SCORAD. Higher SCORAD was observed in patients being the TLR2 rs4696480 major homozygotes and carrying at the same time the FCER1A rs2252226 minor allele, compared to those characterized by (any other of) the remaining combined rs2252226 and rs4696480 genotypes. The observation of the epistatic effect of TLR2 and FCER1A genetic variants on SCORAD is in line with the involvement of the interaction TLRs-FcεRI in the pathophysiology of AD.

The effect of PU.1 knockdown on gene expression and function of mast cells

PU.1 is a hematopoietic cell-specific transcription factor. In the current study, we investigated the role of PU.1 in the gene expression and the function of mouse mast cells (MCs) in vitro and in vivo. When PU.1 siRNA was introduced into bone marrow-derived MCs (BMMCs), IgE-mediated activation was reduced, and the Syk and FcεRIβ mRNA levels were significantly decreased. As the regulatory mechanism of the Syk gene is largely unknown, we performed promoter analysis and found that PU.1 transactivated the Syk promoter through direct binding to a cis-element in the 5′-untranslated region. The involvement of PU.1 in the Syk promoter was also observed in mouse dendritic cells and human MCs, suggesting that the relationship between PU.1 and Syk is common in mammals and in hematopoietic lineages. When antigen was administrated intravenously after the transfusion of siRNA-transfected BMMCs in the mouse footpad, the footpad thickening was significantly suppressed by PU.1 knockdown. Finally, administration of the immunomodulator pomalidomide suppressed passive systemic anaphylaxis of mice. Taken together, these results indicate that PU.1 knockdown might be an efficacious strategy for the prevention of MC-mediated allergic diseases.

The hematopoietic cell-specific transcription factor PU.1 is critical for expression of CD11c

PU.1 is a hematopoietic cell-specific transcription factor belonging to the Ets family, which plays an important role in the development of dendritic cells (DCs). CD11c (encoded by Itgax) is well established as a characteristic marker of hematopoietic lineages including DCs. In the present study, we analyzed the role of PU.1 (encoded by Spi-1) in the expression of CD11c. When small interfering RNA (siRNA) for Spi-1 was introduced into bone marrow-derived DCs (BMDCs), the mRNA level and cell surface expression of CD11c were dramatically reduced. Using reporter assays, the TTCC sequence at -56/-53 was identified to be critical for PU.1-mediated activation of the promoter. An EMSA showed that PU.1 directly bound to this region. ChIP assays demonstrated that a significant amount of PU.1 bound to this region on chromosomal DNA in BMDCs, which was decreased in LPS-stimulated BMDCs in accordance with the reduced levels of mRNAs of Itgax and Spi-1, and the histone acetylation degree. Enforced expression of exogenous PU.1 induced the expression of the CD11c protein on the cell surface of mast cells, whereas control transfectants rarely expressed CD11c. Quantitative RT-PCR also showed that the expression of a transcription factor Irf4, which is a partner molecule of PU.1, was reduced in PU.1-knocked down BMDCs. IRF4 transactivated the Itgax gene in a synergistic manner with PU.1. Taken together, these results indicate that PU.1 functions as a positive regulator of CD11c gene expression by directly binding to the Itgax promoter and through transactivation of the Irf4 gene.

Involvement of PU.1 in NFATc1 promoter function in osteoclast development

BACKGROUND

The transcription factors NFATc1 and PU.1 play important roles in osteoclast development. NFATc1 and PU.1 transactivate osteoclast-specific gene expression and a deficiency in NFATc1 or PU.1 genes causes osteopetrosis due to an insufficient development of osteoclasts. However, the existence of cross-regulation between NFATc1 and PU.1 is largely unknown. In the present study, the role of PU.1 in NFATc1 expression was investigated.

METHODS

Osteoclasts were generated from mouse bone marrow cells. PU.1 knockdown was performed with siRNA introduction. The mRNA levels in siRNA-introduced cells were determined by quantitative RT-PCR. The involvement of PU.1 in the NFATc1 promoter was analyzed by using a chromatin immunoprecipitation (ChIP) assay and a reporter assay. Retrovirus vector was used for enforced expression of PU.1.

RESULTS

Introduction of PU.1 siRNA into bone marrow-derived osteoclasts resulted in a decrease in NFATc1 mRNA level. A ChIP assay showed that PU.1 bound to the NFATc1 promoter in osteoclasts. NFATc1 promoter activity was reduced in PU.1 knockdown cells as assessed by a reporter assay. PU.1 siRNA introduction also downregulated the expression of osteoclast-specific genes and tartrate resistant acid phosphatase (TRAP) activity. Enforced expression of PU.1 using a retrovirus vector increased NFATc1 expression and TRAP activity. When NFATc1 expression was knocked down by using siRNA, the induction of osteoclast-specific genes and TRAP-positive cells was suppressed without affecting the expression level of PU.1.

CONCLUSIONS

These results indicate that PU.1 is involved in osteoclast development by transactivating NFATc1 expression via direct binding to the NFATc1 promoter.

An Exploratory Pilot Study of Genetic Marker for IgE-Mediated Allergic Diseases with Expressions of FcεR1α and Cε

The high affinity immunoglobulin E (IgE) receptor-FcεR1 is mainly expressed on the surface of effector cells. Cross-linking of IgE Abs bound to FcεR1 by multi-valent antigens can induce the activation of these cells and the secretion of inflammatory mediators. Since FcεR1 plays a central role in the induction and maintenance of allergic responses, this study aimed to investigate the association of FcεR1 with the allergic phenotype of Cε expression and cytokine and histamine release from peripheral leukocytes. Peripheral leukocytes from 67 allergic and 50 non-allergic subjects were used for genotyping analysis. Peripheral mononuclear cells (PBMCs) were used for Cε expression and ELISpot analysis, while polymorphonuclear cells (PMNs) were used for histamine release. The association between genotype polymorphism of the FcεR1α promoter region (rs2427827 and rs2251746) and allergic features of Cε expression and histamine were analyzed, and their effects on leukocytes function were compared with wild type. The genotype polymorphisms of FcεR1α promoter region with CT and TT in rs2427827 and TC in rs2251746 were significantly higher in allergic patients than in non-allergic controls. Patients with single nucleotide polymorphism (SNP) of FcεR1α promoter region had high levels of total IgE, mite-specific Der p 2 (Group 2 allergen of Dermatophagoides pteronyssinus)-specific IgE and IgE secretion B cells. The mRNA expression of FcεR1α was significantly increased after Der p2 stimulation in PBMCs with SNPs of the FcεR1α promoter region. Despite the increased Cε mRNA expression in PBMCs and histamine release from PMNs and the up-regulated mRNA expression of interleukin (IL)-6 and IL-8 secretions after Der p2 stimulation, there was no statistically significant difference between SNPs of the FcεR1α promoter region and the wild type. SNPs of FcεR1α promoter region were associated with IgE expression, IgE producing B cells, and increased Der p2-induced FcεR1α mRNA expression. These SNPs may be used as a disease marker for IgE-mediated allergic inflammation caused by Dermatophagoides pteronyssinus.

Genetic determinants in the development of sensitization to environmental allergens in early childhood

Sensitization to environmental allergens remains one of the strongest risk factors for asthma, and there is likely a genetic basis. We sought to identify genetic determinants for the development of allergic sensitization to environmental allergens, particularly cockroach allergen, in early childhood. A total of 631 children with the information about genotypic data on 895 single nucleotide polymorphisms (SNPs) in 179 candidate genes were selected from an existing dataset (Boston Birth Cohort). Genetic analysis was performed for allergic sensitizations among all subjects and sub-population, Black/African, respectively. Eight SNPs in seven genes showed significant association with allergic sensitization with P < 0.05, including two top SNPs, rs7851969 in JAK2 (P = 0.003) and rs11739089 in CNOT6 (P = 0.008). When analyses were specifically performed for cockroach sensitization, 16 SNPs in 13 genes showed P < 0.05, including five genes with SNPs at P < 0.01 (JAK1, JAK3, IL5RA, FCER1A, and ADAM33). Particularly, haplotype analyses demonstrated that multiple-haplotypes in FCER1A were significantly associated with cockroach sensitization with the strongest association for a 2-marker haplotype (rs6665683T-rs12136904T, P = 0.001). Furthermore, SNP rs6665683 was marginally associated with the levels of cockroach allergen specific IgE. When a similar analysis was performed for house dust mite, four SNPs in three genes (JAK2, MAML1, and NOD1) had P < 0.01. Of these, JAK2 appeared to be an only gene showing association across the sensitizations we analyzed. Some of findings were further validated when analysis was limited to black population. Our study identified several loci that may confer the susceptibility to allergic sensitization, and suggested that sensitization to allergens may depend on their unique loci.

Fine-mapping of IgE-associated loci 1q23, 5q31, and 12q13 using 1000 Genomes Project data

BACKGROUND

Genome-wide association studies (GWAS) repeatedly identified 1q23 (FCER1A), 5q31 (RAD50-IL13 and IL4), and 12q13 (STAT6) as major susceptibility loci influencing the regulation of total serum IgE levels. As GWAS may be insufficient to capture causal variants, we performed fine-mapping and re-genotyping of the three loci using 1000 Genomes Project datasets.

METHODS

Linkage disequilibrium tagging polymorphisms and polymorphisms of putative functional relevance were genotyped by chip technology (24 polymorphisms) or MALDI-TOF-MS (40 polymorphisms) in at least 1303 German children (651 asthmatics). The effect of polymorphisms on total serum IgE, IgE percentiles, and atopic diseases was assessed, and a risk score model was applied for gene-by-gene interaction analyses. Functional effects of putative causal variants from these three loci were studied in silico.

RESULTS

Associations from GWAS were confirmed and extended. For 1q23 and 5q31, the majority of associations were found with mild to moderately elevated IgE levels, while in the 12q13 locus, single-nucleotide polymorphisms (SNPs) were associated with strongly elevated IgE levels. Gene-by-gene interaction analyses suggested that the presence of mutations in all three loci increases the risk for elevated IgE up to fourfold.

CONCLUSION

This fine-mapping study confirmed previous associations and identified novel associations of SNPs in 1q23, 5q31, and 12q13 with different levels of serum IgE and their concomitant contribution to IgE regulation.

Human FcR polymorphism and disease

Fc receptors play a central role in maintaining the homeostatic balance in the immune system. Our knowledge of the structure and function of these receptors and their naturally occurring polymorphisms, including single nucleotide polymorphisms and/or copy number variations, continues to expand. Through studies of their impact on human biology and clinical phenotype, the contributions of these variants to the pathogenesis, progression, and/or treatment outcome of many diseases that involve immunoglobulin have become evident. They affect susceptibility to bacterial and viral pathogens, constitute as risk factors for IgG or IgE mediated inflammatory diseases, and impact the development of many autoimmune conditions. In this chapter, we will provide an overview of these genetic variations in classical FcγRs, FcRLs, and other Fc receptors, as well as challenges in achieving an accurate and comprehensive understanding of the FcR polymorphisms and genomic architecture.

Critical Roles for PU.1, GATA1, and GATA2 in the expression of human FcεRI on mast cells: PU.1 and GATA1 transactivate FCER1A, and GATA2 transactivates FCER1A and MS4A2

The high-affinity IgE receptor, FcεRI, which is composed of α-, β-, and γ-chains, plays an important role in IgE-mediated allergic responses. In the current study, involvement of the transcription factors, PU.1, GATA1, and GATA2, in the expression of FcεRI on human mast cells was investigated. Transfection of small interfering RNAs (siRNAs) against PU.1, GATA1, and GATA2 into the human mast cell line, LAD2, caused significant downregulation of cell surface expression of FcεRI. Quantification of the mRNA levels revealed that PU.1, GATA1, and GATA2 siRNAs suppressed the α transcript, whereas the amount of β mRNA was reduced in only GATA2 siRNA transfectants. In contrast, γ mRNA levels were not affected by any of the knockdowns. Chromatin immunoprecipitation assay showed that significant amounts of PU.1, GATA1, and GATA2 bind to the promoter region of FCER1A (encoding FcεRIα) and that GATA2 binds to the promoter of MS4A2 (encoding FcεRIβ). Luciferase assay and EMSA showed that GATA2 transactivates the MS4A2 promoter via direct binding. These knockdowns of transcription factors also suppressed the IgE-mediated degranulation activity of LAD2. Similarly, all three knockdowns suppressed FcεRI expression in primary mast cells, especially PU.1 siRNA and GATA2 siRNA, which target FcεRIα and FcεRIβ, respectively. From these results, we conclude that PU.1 and GATA1 are involved in FcεRIα transcription through recruitment to its promoter, whereas GATA2 positively regulates FcεRIβ transcription. Suppression of these transcription factors leads to downregulation of FcεRI expression and IgE-mediated degranulation activity. Our findings will contribute to the development of new therapeutic approaches for FcεRI-mediated allergic diseases.

Links between allergy and cardiovascular or hemostatic system

In addition to a well-known immunologic background of atherosclerosis and influences of inflammation on arterial and venous thrombosis, there is growing evidence for the presence of links between allergy and vascular or thrombotic disorders. In this interpretative review, five pretty well-documented areas of such overlap are described and discussed, including: (1) links between atherosclerosis and immunoglobulin E or atopy, (2) mutual effects of blood lipids and allergy, (3) influence of atopy and related disorders on venous thromboembolism, (4) the role of platelets in allergic diseases, and (5) the functions of protein C system in atopic disorders.

Different FCER1A polymorphisms influence IgE levels in asthmatics and non-asthmatics

BACKGROUND

Recently, three genome-wide association studies (GWAS) demonstrated FCER1A, the gene encoding a ligand-binding subunit of the high-affinity IgE receptor, to be a major susceptibility locus for serum IgE levels. The top association signal differed between the two studies from the general population and the one based on an asthma case-control design. In this study, we investigated whether different FCER1A polymorphisms are associated with total serum IgE in the general population and asthmatics specifically.

METHODS

Nineteen polymorphisms were studied in FCER1A based on a detailed literature search and a tagging approach. Polymorphisms were genotyped by the Illumina HumanHap300Chip (6 polymorphisms) or MALDI-TOF MS (13 polymorphisms) in at least 1303 children (651 asthmatics) derived from the German International Study of Asthma and Allergies in Childhood II and Multicentre Asthma Genetics in Childhood Study.

RESULTS

Similar to two population-based GWAS, the peak association with total serum IgE was observed for SNPs rs2511211, rs2427837, and rs2251746 (mean r(2) > 0.8), with the lowest p-value of 4.37 × 10(-6). The same 3 polymorphisms showed the strongest association in non-asthmatics (lowest p = 0.0003). While these polymorphisms were also associated with total serum IgE in asthmatics (lowest p = 0.003), additional polymorphisms (rs3845625, rs7522607, and rs2427829) demonstrated associations with total serum IgE in asthmatics only (lowest p = 0.01).

CONCLUSIONS

These data suggest that FCER1A polymorphisms not only drive IgE levels in the general population but that specific polymorphisms may also influence IgE in association with asthma, suggesting that disease-specific mechanisms in IgE regulation exist.

Current concepts of IgE regulation and impact of genetic determinants

Immunoglobulin E (IgE) mediated immune responses seem to be directed against parasites and neoplasms, but are best known for their involvement in allergies. The IgE network is tightly controlled at different levels as outlined in this review. Genetic determinants were suspected to influence IgE regulation and IgE levels considerably for many years. Linkage and candidate gene studies suggested a number of loci and genes to correlate with total serum IgE levels, and recently genome-wide association studies (GWAS) provided the power to identify genetic determinants for total serum IgE levels: 1q23 (FCER1A), 5q31 (RAD50, IL13, IL4), 12q13 (STAT6), 6p21.3 (HLA-DRB1) and 16p12 (IL4R, IL21R). In this review, we analyse the potential role of these GWAS hits in the IgE network and suggest mechanisms of how genes and genetic variants in these loci may influence IgE regulation.

Anti-microbial peptide (AMP): nucleotide variation, gene expression, and host resistance in the white pine blister rust (WPBR) pathosystem

Pinus monticola antimicrobial peptide (PmAMP1) inhibits growth of Cronartium ribicola and other fungal pathogens. C. ribicola causes white pine blister rust and has resulted in a dramatic reduction of native white pines across North America. Quantitative disease resistance (QDR) is a highly desirable trait screened in breeding programs for durable resistance against C. ribicola. Along with phenotyping on a collection of germplasms, we analyzed PmAMP1 transcript and protein expression and re-sequenced the full-length gene including its promoter region. A mixed linear model was used to identify the association of single nucleotide polymorphisms (SNPs) with accumulated protein and stem QDR levels. Among 16 PmAMP1 SNPs identified in the present study, we found an association of protein levels with 6 SNPs (P < 0.05), including 2 in the 5'-untranslated region (UTR), 3 in the open reading frame (ORF) region with 2 nonsynonymous SNPs, and 1 SNP in the 3'-UTR. Another set of six SNPs was associated with stem QDR levels (P < 0.05), with one localized in the promoter region and the other five in the ORF region with four nonsynonymous changes, suggesting that multiple isoforms may have antifungal activity to differing degrees. Of three common PmAMP1 haplotypes, the trees with haplotype 2 showed high QDR levels with moderate protein abundance while those trees with haplotype 3 exhibited low QDR levels in the susceptible range and the lowest level of protein accumulation. Thus, an association of gene variations with protein abundance and resistance-related traits may facilitate elucidation of physiological contribution of PmAMP1 to host resistance.

Involvement of PU.1 in mast cell/basophil-specific function of the human IL1RL1/ST2 promoter

BACKGROUND

The human IL1RL1/ST2 gene encodes IL33 receptor. Recently, IL33 has been recognized as a key molecule for the development of Th2 response. Although mast cells and basophils are major targets of IL33 and play important roles in IL33-mediated Th2-type immune responses, the expression mechanism of ST2 in mast cells and basophils is largely unknown. In the present study, we analyzed regulation mechanism of the human ST2 promoter in the human mast cell line LAD2 and basophilic cell line KU812.

METHODS

Promoter activity was determined by reporter assay with plasmids carrying the wild-type ST2 promoter obtained from human genomic DNA and its mutant. The transcription factor binding to the identified cis-element was identified by an electrophoretic mobility shift assay (EMSA). The effect of candidate transcription factor on ST2 expression was confirmed by analyzing ST2 mRNA level in siRNA-introduced cells.

RESULTS

Reporter assay demonstrated that a cis-element of typical Ets-family binding sequence was critical for promoter activity in LAD2 and KU812. An Ets-family transcription factor PU.1 bound to this element in an EMSA. When PU.1 expression was suppressed by siRNA, ST2 mRNA level was significantly reduced in KU812.

CONCLUSIONS

These observations indicated that PU.1 positively regulates the ST2 promoter as a transcription factor that directly transactivates the ST2 promoter via Ets-family-related cis-element in mast cells and basophils.

GATA2 is a critical transactivator for the human IL1RL1/ST2 promoter in mast cells/basophils: opposing roles for GATA2 and GATA1 in human IL1RL1/ST2 gene expression

The IL1RL1/ST2 gene encodes a receptor for IL-33. Signaling from IL1RL1/ST2 induced by IL-33 binding was recently identified as a modulator of the Th2 response. The target cells for IL-33 are restricted in some hematopoietic lineages, including mast cells, basophils, eosinophils, Th2 cells, natural killer cells, and dendritic cells. To clarify the molecular mechanisms of cell type-specific IL1RL1/ST2 expression in mast cells and basophils, transcriptional regulation of the human IL1RL1/ST2 promoter was investigated using the mast cell line LAD2 and the basophilic cell line KU812. Reporter assays suggested that two GATA motifs just upstream of the transcription start site in the ST2 promoter are critical for transcriptional activity. These two GATA motifs possess the capacity to bind GATA1 and GATA2 in EMSA. ChIP assay showed that GATA2, but not GATA1, bound to the ST2 promoter in LAD2 cells and that histone H3 at the ST2 promoter was acetylated in LAD2 cells, whereas binding of GATA1 and GATA2 to the ST2 promoter was detected in KU812 cells. Knockdown of GATA2 mRNA by siRNA reduced ST2 mRNA levels in KU812 and LAD2 cells and ST2 protein levels in LAD2 cells; in contrast, GATA1 siRNA transfection up-regulated ST2 mRNA levels in KU812 cells. The ST2 promoter was transactivated by GATA2 and repressed by GATA1 in coexpression analysis. When these siRNAs were introduced into human peripheral blood basophils, GATA2 siRNA reduced ST2 mRNA, whereas GATA1 siRNA up-regulated ST2 mRNA. These results indicate that GATA2 and GATA1 positively and negatively control human ST2 gene transcription, respectively.

Association of polymorphisms in the promoter region of FCER1A gene with atopic dermatitis, chronic uticaria, asthma, and serum immunoglobulin E levels in a Han Chinese population

The high-affinity receptor for immunoglobulin E (IgE) plays a central role in allergy diseases. Previous studies have reported the association of variants in the proximal promoter of FCER1A with IgE levels as well as allergy disorders. Another promoter gene polymorphism that is located upstream of exon 1 has not been investigated. We investigated the association of variants in the promoter located upstream of FCER1A exon 1 with serum IgE levels and allergy diseases in a Han Chinese population. A total of 97 patients with atopic dermatitis (AD), 123 patients with chronic urticaria (CU), 286 children with asthma, and control groups were screened for polymorphisms in the promoter region located upstream of FCER1A exon 1 by the polymerase chain reaction-ligation detection reaction method. Total serum IgE levels were tested in groups. The rare allele A of the rs2427837 A/G polymorphism was significantly different in the AD group compared with the controls. No association with the polymorphism was observed in the CU group. In asthmatic patients, IgE levels were higher in the mutation genotypes GA of rs2427837 and TC of rs2251746 compared with normal genotype individuals. The minor allele of rs2427837 and rs2251746 in FCER1A is a genetic risk factor of high IgE levels.

Role of PU.1 in MHC class II expression through transcriptional regulation of class II transactivator pI in dendritic cells

BACKGROUND

PU.1 is a hematopoietic cell-specific transcription factor belonging to the Ets family. We hypothesized that PU.1 is involved in MHC class II expression in dendritic cells (DCs).

OBJECTIVE

The role of PU.1 in MHC class II expression in DCs was analyzed.

METHODS

Transcriptional regulation of the DC-specific pI promoter of the class II transactivator (CIITA) gene and subsequent MHC class II expression was investigated by using PU.1 small interfering RNA (siRNA) and reporter, chromatin immunoprecipitation, and electrophoretic mobility shift assays.

RESULTS

PU.1 siRNA introduction suppressed MHC class II expression, allogeneic and syngeneic T-cell activation activities of bone marrow-derived DCs (BMDCs) with reduction of CIITA mRNA driven by the DC-specific promoter pI, and MHC class II mRNA. The chromatin immunoprecipitation assay showed constitutive binding of PU.1 to the pI region in BMDCs, whereas acetylation of histone H3 on pI was suppressed by LPS stimulation in parallel with shutdown of CIITA transcription. PU.1 transactivated the pI promoter through cis-elements at -47/-44 and -30/-27 in a reporter assay and to which PU.1 directly bound in an electrophoretic mobility shift assay. Acetylation of histones H3 and H4 on pI was reduced in PU.1 siRNA-introduced BMDCs. Knockdown of interferon regulatory factor 4 or 8, which is a heterodimer partner of PU.1, by siRNA did not affect pI-driven CIITA transcription or MHC class II expression.

CONCLUSION

PU.1 basally transactivates the CIITA pI promoter in DCs by functioning as a monomeric transcription factor and by affecting histone modification, resulting in the subsequent expression and function of MHC class II.

An association of TLR2–16934A >T polymorphism and severity/phenotype of atopic dermatitis

BACKGROUND

Toll-like receptor 2 gene (TLR2) –16934A>T polymorphism has been shown to be associated with severity of atopic dermatitis (AD) as measured using severity scoring of atopic dermatitis (SCORAD) index. Moreover, TLR2–16934A>T polymorphism has been associated with atopy and allergic disorders in farmers’ children.

OBJECTIVE

The aim of this study was to evaluate an association between TLR2–16934A>T polymorphism and AD phenotype, including disease severity and concomitant atopic diseases, or potential serum markers of AD severity and also to find a molecular background of the clinical associations.

METHODS

Genotyping for TLR2–16934A>T polymorphism was performed in 130 consecutive adult ambulatory patients with AD. Total serum (TS) IgE levels, serum tryptase, plasma interleukin-6 and C-reactive protein were measured. In addition, luciferase assay and electrophoretic-mobility shift assay were conducted to assess the effect of –16934A>T polymorphism on transcriptional activity.

RESULTS

There was an inverse association of TLR2–16934TT genotype and/or –16934T allele with SCORAD, but not with TS IgE, tryptase or inflammatory markers. Interestingly, –16934AA genotype and/or –16934A allele were overrepresented in AD patients with concomitant asthma or a family history of atopy. In a subgroup analysis, TLR2–16934A>T polymorphism was associated with SCORAD, asthma, allergic conjunctivitis or family history of atopy in AD patients with TS IgE ≥106 IU/mL but not in those having TS IgE <106 IU/mL. Functional analyses showed that TLR2–16934T allele is associated with higher luciferase activity in human monocytic THP-1 cells and preferential binding of the THP-1-derived nuclear protein.

CONCLUSION

TLR2–16934A>T polymorphism could be a genetic predictor of AD severity, the coexistence of asthma or atopic conjunctivitis as well as a family history of atopic diseases, especially in subjects having higher TS IgE. TLR2–16934A>T polymorphism affects transcriptional activity, which may at least in part account for the clinical associations observed for the –16934A>T polymorphism.

FCεRI gene promoter polymorphisms and total IgE levels in susceptibility to atopic dermatitis in Korea

IgE-dependent activation of mast cells and basophils through the high-affinity IgE receptor (FcεRI) is involved in the pathogenesis of allergen-induced immune responsiveness in atopic diseases like atopic dermatitis (AD). We sought to determine FcεRI gene polymorphisms are associated with AD in Korean patients, and analyzed the relevance of FcεRI gene polymorphisms and serum IgE levels. We conducted a case-control association analysis (175 patients and 56 controls) of Korean subjects. Genotyping was performed using the TaqMan fluorogenic 5' nuclease assay, and serum levels of IgE were measured using a fluorescence enzyme immunoassay. We found that there were no significant relationships between FcεRI and AD, although there were trends towards an association between the 66T>C (rs2251746) polymorphism and total serum IgE levels in the Korean AD patients. In conclusion, while the 66T>C (rs2251746) of the FcεRIα polymorphism may be linked to AD and higher serum IgE levels, polymorphisms in the FcεRIβ gene did not confer susceptibility to AD in our patient sample.

SNPs in the FCER1A gene region show no association with allergic rhinitis in a Han Chinese population

Background

Immunoglobulin E (IgE) is a central player in the allergic response, and raised total IgE levels are considered as an indicator of atopy or potential development of atopy. A recent genome-wide scan in a German population-based cohort of adults identified the gene encoding the alpha chain of the high affinity receptor for IgE (FCER1A) as a susceptibility locus influencing total serum IgE levels. The aim of this study was to investigate whether the polymorphisms in the FCER1A gene are associated with allergic rhinitis (AR) in a Han Chinese population.

Methodology/Principal Findings

A population of 378 patients with AR and 288 healthy controls was studied. Precise phenotyping of patients was accomplished by means of a questionnaire and clinical examination. Blood was drawn for DNA extraction and total serum immunoglobulin E (IgE) measurement. A total of 16 single nucleotide polymorphisms (SNPs) in FCER1A were selected and individually genotyped. None of the SNPs in the FCER1A showed an association with AR. Similarly, the lack of association was also evident in subgroup analysis for the presence of different allergen sensitivities. None of the selected SNPs in FCER1A was associated with total IgE level.

Conclusions

Although FCER1A presents itself as a good candidate for contributing to total serum IgE, this study failed to find an association between SNPs in the FCER1A gene region and IgE level or AR susceptibility.

Critical role of transcription factor PU.1 in the expression of CD80 and CD86 on dendritic cells

In this study, we investigated the role of a transcription factor, PU.1, in the regulation of CD80 and CD86 expression in dendritic cells (DCs). A chromatin immunoprecipitation assay revealed that PU.1 is constitutively bound to the CD80 and CD86 promoters in bone marrow-derived DCs. In addition, co-expression of PU.1 resulted in the transactivation of the CD80 and CD86 promoters in a reporter assay. The binding of PU.1 to cis-enhancing regions was confirmed by electromobility gel-shift assay. As expected, inhibition of PU.1 expression by short interfering RNA (siRNA) in bone marrow-derived DCs resulted in marked down-regulation of CD80 and CD86 expression. Moreover, overexpression of PU.1 in murine bone marrow-derived lineage-negative cells induced the expression of CD80 and CD86 in the absence of monocyte/DC-related growth factors and/or cytokines. Based on these results, we conclude that PU.1 is a critical factor for the expression of CD80 and CD86. We also found that subcutaneous injection of PU.1 siRNA or topical application of a cream-emulsified PU.1 siRNA efficiently inhibited murine contact hypersensitivity. Our results suggest that PU.1 is a potential target for the treatment of immune-related diseases.

Establishment of a simple detection system for blood group ABO-specific transferase activity in DNA-transfected cells

A/B-transferase is a glycosyltransferase that transfers a sugar substrate onto H-antigen resulting in the synthesis of glycoproteins and glycolipids termed A/B-antigens. The ABO blood group (ABO) gene encoding A/B-transferase possesses numerous polymorphisms affecting the specificity and/or activity of the enzyme. The relationship between genotype and phenotype is very complicated, except for those of some critical polymorphisms. In order to establish a system for evaluating the effect of each polymorphism on the transferase function, an A- or B-transferase cDNA expressing vector was introduced into HeLa cells, a cell line that do not possess endogenous A/B-transferase activity. We successfully detected substrate-specific transferase activity in the cells and in the culture medium. Furthermore, in three different assays, each corresponding A- or B-antigen was detected in the transfectants with high sensitivity. Accordingly, the present study demonstrates a possibility that A/B-transferase variants may be characterized by using this method.

Genetic variability of the high-affinity IgE receptor alpha-subunit (FcepsilonRIalpha)

Our knowledge on the variability of FCER1A gene encoding for alpha-subunit of the high-affinity immunoglobulin E receptor (FcepsilonRI) that plays a central role in the pathogenesis of allergy and related disorders, has been recently much extended. Last findings from FCER1A mutational screening and genetic association studies, followed by functional analyses of the polymorphisms, are briefly summarized in this mini-review. The association between FCER1A gene variants and total serum IgE levels seems especially interesting and, supported by functional analyses of polymorphisms, may provide a rationale for pharmacogenetic studies on anti-IgE therapy that indirectly suppresses FcepsilonRI expression.

Congenital toxoplasmosis: candidate host immune genes relevant for vertical transmission and pathogenesis

Toxoplasma gondii infects a variety of vertebrate hosts, including humans. Transplacental passage of the parasite leads to congenital toxoplasmosis. A primary infection during the first weeks of gestation causes vertical transmission at low rate, although it causes major damage to the embryo. Transmission frequency increases to near 80% by the end of pregnancy, but the proportion of ill newborns is low. For transmission and pathogenesis, the parasite genetics is certainly important. Several host innate and adaptative immune response genes are induced during infection in adults, which control the rapidly replicating tachyzoite. The T helper 1 (Th1) response is protective, although it has to be modulated to avoid inflammatory damage. Paradoxical observations on this response pattern in congenital toxoplasmosis have been reported, as it may be protective or deleterious, inducing sterile abortion or favoring parasite transplacental passage. Regarding pregnancy, an early Th1 microenvironment is important for control of infectious diseases and successful implantation, although it has to be regulated to support trophoblast survival. Polymorphism of genes involved in these parallel phenomena, such as Toll-like receptors (TLRs), adhesins, cytokines, chemokines or their receptors, immunoglobulins or Fc receptors (FcRs), might be important in susceptibility for T. gondii vertical transmission, abortion or fetal pathology. In this study some examples are presented and discussed.

Functional and clinical consequences of Fc receptor polymorphic and copy number variants

Receptors for immunoglobulins (Fc receptors) play a central role during an immune response, as they mediate the specific recognition of antigens of almost infinite diversity by leucocytes, thereby linking the humoral and cellular components of immunity. Indeed, engagement of Fc receptors by immunoglobulins initiates a range of immunoregulatory processes that might also play a role in disease pathogenesis. In the circulation, five main types of immunoglobulins (Ig) exist - namely IgG, IgA, IgE, IgM and IgD and receptors with the ability to recognize and bind to IgG (Fc gamma receptor family), IgE (Fc epsilon RI and CD23), IgA (CD89; Fc alpha/microR) and IgM (Fc alpha/microR) have been identified and characterized. However, it is astonishing that nearly all the known human Fc receptors display extensive genetic variation with clear implications for their function, thus representing a substantial genetic risk factor for the pathogenesis of a range of chronic inflammatory disorders.

FcepsilonRIalpha gene -18483A>C polymorphism affects transcriptional activity through YY1 binding

Three frequent genetic polymorphisms in the human high-affinity IgE receptor alpha-subunit (FcepsilonRIalpha) were shown to be associated with allergic disorders and/or total serum IgE levels in allergic patients. Two of these were previously demonstrated to affect FcepsilonRIalpha expression while the third -18483A>C (rs2494262) has not yet been subjected to functional studies. We hypothesized that the -18483A>C variant affects transcriptional activity of the FcepsilonRIalpha distal promoter in monocytes in which FcepsilonRIalpha transcription is driven through that regulatory region. Indeed, we confirmed preferential binding of the YY1 transcription factor to the -18483C allele, resulting in lower transcriptional activity when compared with the -18483A allele.

Involvement of PU.1 in the transcriptional regulation of TNF-alpha

PU.1 is a myeloid- and lymphoid-specific transcription factor that serves many important roles in the development and specific gene regulation of hematopoietic lineages. Mast cells (MC) and dendritic cells (DC) express PU.1 at low and high levels, respectively. Previously, we found that enforced expression of PU.1 in MC resulted in acquisition of DC-like characteristics, including repression of several IgE-mediated responses due to reduced expression of IgE-signaling related molecules. In contrast, PU.1 overexpression in MC up-regulated TNF-alpha production in response to IgE- and LPS-stimulation suggesting that PU.1 positively regulates TNF-alpha expression. However, the role of PU.1 in the expression of TNF-alpha is largely unknown. In the present study, the effects of PU.1 on the TNF-alpha promoter in mouse bone marrow-derived (BM) MC and DC were studied. Real-time PCR, ELISA, and chromatin immunoprecipitation assays indicated that the kinetics and magnitude of TNF-alpha expression levels following LPS- or IgE-stimulation are related to the amount of PU.1 binding to the promoter. In brief, higher and delayed up-regulation of TNF-alpha promoter function was observed in DC, whereas there were lower and rapid responses in MC. When PU.1-overexpressing retrovirus vector was introduced into MC, the amount of PU.1 recruited to the TNF-alpha promoter markedly increased. The knockdown of PU.1 in BMDC by siRNA resulted in a reduction of TNF-alpha protein produced from LPS-stimulated BMDC. These observations indicate that PU.1 transactivates the TNF-alpha promoter and that the amount of PU.1 binding on the promoter is associated with promoter activity.

Roles of PU.1 in monocyte- and mast cell-specific gene regulation: PU.1 transactivates CIITA pIV in cooperation with IFN-gamma

Over-expression of PU.1, a myeloid- and lymphoid-specific transcription factor belonging to the Ets family, induces monocyte-specific gene expression in mast cells. However, the effects of PU.1 on each target gene and the involvement of cytokine signaling in PU.1-mediated gene expression are largely unknown. In the present study, PU.1 was over-expressed in two different types of bone marrow-derived cultured mast cells (BMMCs): BMMCs cultured with IL-3 plus stem cell factor (SCF) and BMMCs cultured with pokeweed mitogen-stimulated spleen-conditioned medium (PWM-SCM). PU.1 over-expression induced expression of MHC class II, CD11b, CD11c and F4/80 on PWM-SCM-cultured BMMCs, whereas IL-3/SCF-cultured BMMCs expressed CD11b and F4/80, but not MHC class II or CD11c. When IFN-gamma was added to the IL-3/SCF-based medium, PU.1 transfectant acquired MHC class II expression, which was abolished by antibody neutralization or in Ifngr(-/-) BMMCs, through the induction of expression of the MHC class II transactivator, CIITA. Real-time PCR detected CIITA mRNA driven by the fourth promoter, pIV, and chromatin immunoprecipitation indicated direct binding of PU.1 to pIV in PU.1-over-expressing BMMCs. PU.1-over-expressing cells showed a marked increase in IL-6 production in response to LPS stimulation in both IL-3/SCF and PWM-SCM cultures. These results suggest that PU.1 overproduction alone is sufficient for both expression of CD11b and F4/80 and for amplification of LPS-induced IL-6 production. However, IFN-gamma stimulation is essential for PU.1-mediated transactivation of CIITA pIV. Reduced expression of mast cell-related molecules and transcription factors GATA-1/2 and up-regulation of C/EBPalpha in PU.1 transfectants indicate that enforced PU.1 suppresses mast cell-specific gene expression through these transcription factors.

Functional analysis of a polymorphism in the promoter region of the IL-12/23p40 gene

BACKGROUND

Human IL-12B gene on chromosome 5q31 encodes the common p40 subunit of IL-12 and IL-23. IL-12 is known to play critical roles in the generation of T-helper type 1 (TH(1)) cells, whereas IL-23 is involved in maintenance and/or population expansion of TH(17) cells. Although several reports suggested an association between a polymorphism (-6415CTCTAA/GC) in IL-12B and asthma, the molecular mechanism how this polymorphism is involved in allergic inflammation is still unclear.

METHODS

The transcription activity was analysed by reporter assay. A transcription factor binding to -6415 polymorphic site was identified by electrophoretic mobility shift assay (EMSA) and chromatin immunoprecipitation (ChIP) assay. The amount of cytokines produced from peripheral monocytes were determined by ELISA.

RESULTS

Reporter assay showed that the transcription activity of the GC allele was higher than that of the CTCTAA allele. A transcription factor Sp1 bound to the region including the GC allele with a higher affinity than that of the CTCTAA allele in EMSA. In vivo binding of Sp1 to IL-12B gene carrying -6415GC was confirmed by ChIP assay. Overexpression of Sp1 up-regulated transcription activity of promoter carrying GC allele sequence, whereas the CTCTAA promoter was not affected by Sp1. We examined the correlation between -6415CTCTA/GC polymorphism and production of cytokine IL-12/23p40, IL-12p70, and IL-23 on peripheral blood monocytes, and monocytes with the GC/GC allele exhibited significantly higher expression of IL-12p70 protein than those with the CTCTAA/CTCTAA allele (P=0.009).

CONCLUSIONS

The -6415 polymorphism is involved in cytokine production potential by affecting Sp1-mediated transcription activity.

Single-stranded conformation polymorphism (SSCP)-driven indirect sequencing in detection of short deletion

To seek for novel rare and/or sporadic mutations within genomic neighborhood of common -344 C>T (rs2427827) FCER1A proximal promoter polymorphism, which by its prevalence could have masked the presence of less frequent genetic variants in our previous single-stranded conformational polymorphism (SSCP) mutational search study, SSCP screening was repeated using primers fixing -344 C>T variant. The genomic region surrounding -344 C>T polymorphism was confirmed to be fairly conservative and only a single sporadic mutation (present in 1 out of 196 chromosomes), a 6-bp deletion -262 to 257 del CTAGAC, was found. From the methodological point of view, we demonstrated a successful detection of a short-length polymorphism using SSCP screening in a population, in which the same genomic region contained frequent single-nucleotide polymorphic variant. In conjunction with subsequent cloning of aberrantly migrating PCR products and SSCP-driven indirect sequencing of the clones, this method offers a superior (to direct sequencing of PCR products) detection of rare mutations. The cost-effective method applied by us enables a reliable characterization of infrequent (thus present only in heterozygotic form) short-length variance of the sequence which are difficult to interpret by direct sequencing.

Fusion of OTT to BSAC results in aberrant up-regulation of transcriptional activity

OTT/RBM15-BSAC/MAL/MKL1/MRTF-A was identified as a fusion transcript generated by t(1;22)(p13;q13) in acute megakaryoblastic leukemia. Previous studies have shown that BSAC (basic, SAP, and coiled-coil domain) activates the promoters containing CArG boxes via interaction with serum response factor, and OTT (one twenty-two) negatively regulates the development of megakaryocytes and myeloid cells. However, the mechanism by which OTT-BSAC promotes leukemia is largely unknown. Here we show that OTT-BSAC, but not BSAC or OTT strongly activates several promoters containing a transcription factor Yin Yang 1-binding sequence. In addition, although BSAC predominantly localizes in the cytoplasm and its nuclear translocation is considered to be regulated by the Rho-actin signaling pathway, OTT-BSAC exclusively localizes in the nucleus. Moreover, OTT interacts with histone deacetylase 3, but this interaction is abolished in OTT-BSAC. Collectively, these functional and spatial changes of OTT and BSAC caused by the fusion might perturb their functions, culminating in the development of acute megakaryoblastic leukemia.