Middle meatus microbiome in patients with eosinophilic chronic rhinosinusitis in a Japanese population.

BACKGROUND: Chronic rhinosinusitis (CRS) is a common chronic inflammatory disease and is subdivided into eosinophilic and noneosinophilic forms. There are few reports investigating the nasal microbiome and its pathological functions in patients with CRS. OBJECTIVE: We sought to analyze factors contributing to variations of the nasal microbiome in CRS, and on the basis of these factors, to elucidate whether the bacterial metabolites were related to the pathogenesis. METHODS: Nasal swabs were collected, and the V3 to V4 variable region of the 16S ribosomal RNA gene was amplified and sequenced. Factors contributing to variations of the nasal microbiome in patients with CRS were compared. The most influential factor was whether CRS was eosinophilic, and we compared α- and ß-diversity, bacterial species, and predictive bacterial functions between the 2 patient groups. In addition, the metabolites of the key bacteria were extracted, and we evaluated the predicted bacterial functions in airway epithelial cells. RESULTS: In total, 110 patients with CRS and 33 control subjects were enrolled. On the basis of the factors of variation, it was found that patients with eosinophilic CRS (n = 65) had different microbiomes with weighted UniFrac ß-diversity and lower α-diversity compared with those with noneosinophilic CRS (n = 45). A higher abundance of Fusobacterium nucleatum and an increased LPS pathway were observed in patients with noneosinophilic CRS compared with those with eosinophilic CRS. In airway epithelial cells, LPS derived from F nucleatum suppressed the expression levels of ALOX15 induced by TH2 cytokines. CONCLUSIONS: The differences in the nasal microbiome may play a key role in the pathophysiology of CRS.

A novel de-novo RB1 mutation identified in a patient with bilateral retinoblastoma.

Retinoblastoma manifests as ocular malignancy due to mutations in the RB1 gene. A 17-month-old girl with bilateral retinoblastoma having no family history was admitted to our hospital. The right eye was enucleated but the other was preserved with systemic chemotherapy and topical treatment. The patient has been tumor-free for over 7 years since diagnosis. All exons of RB1 were sequenced and a novel 1-base pair deletion (NM_000321.2:c.2409del, p.Asn803Lysfs*7) was detected.

Cancer predisposition genes in Japanese children with rhabdomyosarcoma.

Rhabdomyosarcoma (RMS) is one of the most common soft tissue sarcomas in children. Germline mutations in cancer-predisposition genes have been detected in approximately 10% of pediatric cancers. However, the genetic background of RMS is still unclear, especially in Asian children. DNA was extracted from the peripheral blood of children with RMS and cancer-associated genes analyzed using targeted re-sequencing. Twenty patients participated in this study. There were three deaths due to RMS. One patient developed a second neoplasm. Nine patients had long-term co-morbidities. Six pathogenic variants were found in five patients: one nonsense variant of DICER1, one exon deletion of TP53, and three missense variants of BUB1B, LIG4, and MEN1. Two of the five patients had a family history of cancer. Two patients with missense variants of LIG4 had long-term co-morbidities of drug-induced cardiomyopathy. The missense variants of LIG4, essential for DNA double-strand break repair, were detected in two unrelated patients. While this is the first report of the germline genetic analysis of Japanese children with RMS with detailed clinical information, the frequency of the variant was almost equivalent to that of previous reports from western countries. Unbiased exon sequencing may be useful to clarify the pathogenesis of RMS in children and in predicting the clinical course of these patients.

Cancer-Predisposition Genetic Analysis in Children with Brain Tumors Treated at a Single Institution in Japan.

Brain tumors affect one-third of all children with cancer. Approximately 10% of children with cancer carry variants in cancer-predisposition genes. However, germline analyses in large cohorts of Asian children have not been reported. Thirty-eight Japanese patients with pediatric brain tumors were included in this study (19 boys, 19 girls). DNA was extracted from the patients' peripheral blood, and cancer-associated genes were analyzed using targeted resequencing. Rare variants with allele frequencies <0.1% in the general population and variants suspected to be pathogenic were extracted and analyzed. Pathogenic variants were found in 7 patients (18%): 2 nonsense variants of CHEK2 and FANCI; 2 frameshift deletions in SMARCB1 and PTCH1; and 3 missense variants of TSC1, WRN, and MLH1. The median age at diagnosis was 9.1 years, and three of the 7 patients had a family history of cancer. One patient diagnosed with basal cell nevus syndrome, also called Gorlin syndrome, developed a second neoplasm, and another with an SMARCB1 variant and an atypical teratoid/rhabdoid tumor developed a thyroid adenomatous nodule. This is the first cancer-related germline analysis with detailed clinical information reported in Japanese children with brain tumors. The prevalence was almost equivalent to that in white children.

Involvement of Activation of Mast Cells via IgE Signaling and Epithelial Cell-Derived Cytokines in the Pathogenesis of Pollen Food Allergy Syndrome in a Murine Model.

Murine models to elucidate the pathogenesis of pollen food allergy syndrome (PFAS), characterized by oral hypersensitivity symptoms induced by specific foods in patients previously sensitized with a pollen, are lacking. The study aimed to examine PFAS pathogenesis in a novel murine model. Birch pollen-immunized mice were orally administered apple extract, and oral symptoms were evaluated based on oral rubbing frequency following the challenge. The birch pollen-immunized mice orally challenged with apple extract exhibited PFAS-like symptoms, including oral rubbing and positive reaction of swelling by the prick test. The apple extract administered with a protease inhibitor reduced the oral rubbing frequency, which was also significantly reduced in the immunized Fcer1a -/- and mast cell-deficient mice compared with the immunized control mice. The oral rubbing frequency, serum IgE levels, and Th2-cytokine production by the cervical lymph node cells were significantly reduced in the immunized Il-33 -/- and thymic stromal lymphopoietin receptor-deficient (Crlf2 -/-) mice as compared with the immunized wild-type mice. IL-33 and thymic stromal lymphopoietin involve the pathogenesis of PFAS. The apple-extract stimulation did not lead to increased Th2-cytokine production in the oral mucosa or number of group 2 innate lymphoid cells or eosinophils. PFAS involves an early-phase response by mast cell degranulation via IgE signaling after the cross-reactivity of Bet v 1-specific IgE and the food allergen, and exacerbation of allergic symptom via proteases in food; PFAS does not involve a late phase with local Th2/eosinophilic inflammation in the oral mucosa. This novel murine model might be used for elucidating the pathogenesis and assessing new therapeutic strategies for PFAS.

Analysis of patient factors associated with hospital visits for allergic rhinitis in Japanese adult patients: A cross-sectional study.

OBJECTIVE: Allergic rhinitis (AR) is one of the most common diseases in Japan. However, several AR patients do not seek optimal treatments at clinics/hospitals. This may affect the patient's quality of life and labor productivity. In this study, we assessed the characteristics of the outpatients' AR and factors associated with their hospital visit, using the dataset obtained from a nation-wide survey in Japan. METHODS: In this cross-sectional study, we used data from the nation-wide 2013 and 2016 Comprehensive Survey of Living Conditions (CSLC) in Japan. We analyzed the data of AR outpatients through logistic regression, using the outcome as the dependent variable, and age groups, sex, household size, educational status, smoking history, alcohol use, household expenditure, psychological distress, quality of sleep, asthma and atopic dermatitis outpatients as explanatory variables. RESULTS: Among the data of 317,984 outpatients aged between 20 and 79 years in 2016 CSLC survey, the proportion of AR outpatients was significantly less among current smokers (odds ratio (OR); 0.47, 95% confidence interval (CI); 0.43-0.51, P < 0.001) and those with large household sizes (OR; 0.80, 95% CI; 0.72-0.89, P < 0.001). Conversely, the proportion of AR outpatients was significantly more among subjects with a past smoking habit (OR; 1.19, 95% CI; 1.08-1.31, P < 0.001), insufficient sleep (OR; 2.93, 95% CI; 2.52-3.42, P < 0.001), psychological distress (OR; 1.71, 95% CI; 1.62-1.80, P < 0.001), high household expenditures (OR; 1.68, 95% CI; 1.56-1.80, P < 0.001), and asthma and atopic dermatitis outpatients (OR; 8.97, 95% CI; 8.13-9.89 P < 0.001 for asthma and OR; 7.61, 95% CI; 6.76-8.58 P < 0.001 for atopic dermatitis). We observed the same trend using the dataset of 2013 CLSC survey. CONCLUSION: This study revealed that smoking habit, psychological distress, insufficient sleep, high household expenditures and outpatients with other allergic diseases are the factors associated with AR outpatient visit.

ORMDL3/GSDMB genotype as a risk factor for early-onset adult asthma is linked to total serum IgE levels but not to allergic sensitization.

BACKGROUND: An orosomucoid-like 3 (ORMDL3)/gasdermin B (GSDMB) gene locus on chromosome 17q is consistently associated with childhood-onset asthma, which is highly atopic. As some evidence suggests the relationship between asthma and allergic sensitization reflects asthma patient susceptibility to augmented IgE responses driven by common environmental allergens rather than an increased asthma risk after allergen exposure, we aimed to determine any relationships between this locus region and childhood-onset adult asthma with regard to serum total IgE levels or allergic sensitization. METHODS: We conducted a case-control association study using three independent Japanese populations (3869 total adults) and analyzed the ORs for association of rs7216389, an expression quantitative trait locus for ORMDL3/GSDMB, with adult asthma according to onset age. Additionally, associations between the rs7216389 genotype and total serum IgE levels or allergic sensitization was examined. RESULTS: Rs7216389 was associated with both childhood-onset adult asthma (OR for asthmatic patients afflicted at the age of 10 years or younger = 1.61, p = 0.00021) and asthmatic patients with higher levels of total serum IgE (OR for asthmatic patients with IgE ≥1000IU/mL = 1.55, p = 0.0033). In both healthy controls and in the combined healthy and asthmatic individuals, rs7216389 was correlated with increased total serum IgE levels (p < 0.0005), but not allergic sensitization (p > 0.1). CONCLUSIONS: ORMDL3/GSDMB is an important susceptibility gene for childhood-onset adult asthma in Japanese populations and this association is linked to elevated total serum IgE levels but not to allergic sensitization.

Neoantigen prediction in human breast cancer using RNA sequencing data.

Neoantigens have attracted attention as biomarkers or therapeutic targets. However, accurate prediction of neoantigens is still challenging, especially in terms of its accuracy and cost. Variant detection using RNA sequencing (RNA-seq) data has been reported to be a low-accuracy but cost-effective tool, but the feasibility of RNA-seq data for neoantigen prediction has not been fully examined. In the present study, we used whole-exome sequencing (WES) and RNA-seq data of tumor and matched normal samples from six breast cancer patients to evaluate the utility of RNA-seq data instead of WES data in variant calling to detect neoantigen candidates. Somatic variants were called in three protocols using: (i) tumor and normal WES data (DNA method, Dm); (ii) tumor and normal RNA-seq data (RNA method, Rm); and (iii) combination of tumor RNA-seq and normal WES data (Combination method, Cm). We found that the Rm had both high false-positive and high false-negative rates because this method depended greatly on the expression status of normal transcripts. When we compared the results of Dm with those of Cm, only 14% of the neoantigen candidates detected in Dm were identified in Cm, but the majority of the missed candidates lacked coverage or variant allele reads in the tumor RNA. In contrast, about 70% of the neoepitope candidates with higher expression and rich mutant transcripts could be detected in Cm. Our results showed that Cm could be an efficient and a cost-effective approach to predict highly expressed neoantigens in tumor samples.

High-Yield Production of the Major Birch Pollen Allergen Bet v 1 With Allergen Immunogenicity in Nicotiana benthamiana.

Type I allergy is an immunological disorder triggered by allergens and causes significant health problems. The major allergen of birch pollen is Bet v 1, which belongs to the pathogen-related protein 10 (PR-10) family. Here, we established a rapid and robust method for the production of Bet v 1 in Nicotiana benthamiana leaves, with binding activity to allergic patients' IgE. The Bet v 1 allergen was expressed in N. benthamiana using a strong agroinfiltration-based transient protein expression system, which consists of a deconstructed geminiviral vector system with a double terminator. Five days post-infiltration, the allergen concentration in N. benthamiana leaves was 1.2 mg/g of fresh mass, being this the maximum yield of Bet v 1 in plants reported up to now. A part of plant-derived Bet v 1 was glycosylated. Bet v 1 purified from N. benthamiana or Brevibacillus brevis was used to carry out enzyme-linked immunoassays; both recombinant allergens were found to have comparable binding properties to the IgE of allergic patients. These results suggest that our plant expression system allows rapid and robust production of the allergen, which keeps the immunogenicity.

Ovarian metastases from ileum cancer in a patient with germline EPCAM gene deletion successfully treated with surgical resection and CAPOX chemotherapy: a case report.

BACKGROUND: Despite recent findings that epithelial cell adhesion molecule (EPCAM) deletions can cause Lynch syndrome (LS), its clinical characteristics are still unknown. We present the first case of ileum cancer in a patient with germline EPCAM gene deletion, which was discovered during ovarian tumor surgery. CASE PRESENTATION: A 59-year-old woman presented with a history of colon cancer occurring at 38 and 55 years old. Five of her siblings had a history of colon cancer, and an elder sister had confirmed LS. As imaging examination revealed an ovarian tumor, and we performed hysterectomy and bilateral salpingo-oophorectomy. Careful observation during surgery revealed a cherry-sized tumor in the ileum, prompting partial ileal resection. Pathological examination showed the ovarian tumor to be a metastasis of ileum cancer. Genetic testing with blood-relative information using multiplex ligation-dependent probe amplification showed EPCAM exons 8 and 9 deletions, confirming LS. The patient received adjuvant chemotherapy with CAPOX (capecitabine and oxaliplatin) and has remained disease-free for 24 months. CONCLUSIONS: We were fortunate to identify ileum cancer that would have been difficult to find preoperatively through careful observation during ovarian tumor surgery and successfully treated the patient by using surgical resection and CAPOX chemotherapy. When treating patients with hereditary cancer syndromes including LS, we should keep all associated cancers in mind.

Genetic and peripheral markers of the oxytocin system and parental care jointly support the cross-generational transmission of bonding across three generations.

BACKGROUND: Human and animal research indicates that oxytocin (OT) plays a key role in the cross-generational transmission of parental bonding, and human studies suggest that allelic variations on the oxytocin receptor gene (OXTR) and circulating OT levels interact with patterns of parental care to shape children's social-affiliative competencies. Yet, no study to date has tested the joint contribution of OT and parental care across three generations. METHODS: The study included 345 participants comprising 115 family lines of grandmothers, mothers, and their infants. Salivary OT and allelic variations on the OXTR (rs53576 and rs2254298) and CD38 (rs3796863) single nucleotide polymorphisms (SNPs), which have been previously associated with parental bonding, were assessed in all participants. Parental care was measured from grandmothers to mothers and from mothers to their infants. RESULTS: Mothers receiving parenting characterized by high overprotection from grandmothers showed more rejection toward their infants only when carrying the G allele on the OXTRrs53576 (AG/GG). These mothers of highly overprotective grandmothers also had lower oxytocin levels. Infants who were OXTRrs2254298 A carriers (AA/AG) and whose mothers reported more rejection toward their infants had higher oxytocin levels. Grandmothers receiving higher overprotection from great-grandmothers showed poorer parenting style compared to grandmothers experiencing lower parental overprotection only when carrying the OXTRrs2254298 GG genotype. CONCLUSIONS: Our findings are the first to demonstrate how genetic and peripheral markers on the oxytocin system interact with experienced parenting to shape bonding across three generations. Results have important implications for specifying the biological and behavioral determinants associated with the continuity of adaptive versus maladaptive patterns of attachment across generations.

Periostin as a novel biomarker for postoperative recurrence of chronic rhinosinitis with nasal polyps.

We previously reported that chronic rhinosinusitis with nasal polyps (CRSwNP) was subdivided into four chronic rhinosinusitis (CRS) subtypes using the JESREC scoring system. We sought to identify the gene expression profile and biomarkers related with CRSwNP by RNA-sequence. RNA-sequencing was performed to identify differentially expressed genes between nasal polyps (NPs) and inferior turbinate mucosa from 6 patients with CRSwNP, and subsequently, quantitative real-time PCR was performed to verify the results. ELISA was performed to identify possible biomarkers for postoperative recurrence. In the RNA-sequencing results, periostin (POSTN) expression was the highest in NP. We focused on POSTN and investigated the protein level of POSTN by immunohistochemistry and ELISA. POSTN was diffusely expressed in moderate and severe eosinophilic CRS using immunohistochemistry, and its staining pattern was associated with the severity of the phenotype of the CRSwNP (P < 0.05). There was a significant difference between the POSTN high/low groups for postoperative recurrence when the cutoff point was set at 115.5 ng/ml (P = 0.0072). Our data suggests that the protein expression level of POSTN was associated with the severity of CRSwNP, and serum POSTN can be a novel biomarker for postoperative recurrence of CRSwNP.

DNA Methylation of Proximal PLAT Promoter in Chronic Rhinosinusitis With Nasal Polyps.

Background Nasal polyps (NP) are characterized by pseudocysts derived from stromal tissue edema and cause persistent infections in patients with chronic rhinosinusitis (CRS). A low level of tissue-type plasminogen activator (gene name PLAT) is considered a cause of stromal tissue edema because of insufficient plasmin activation in NP; however, the mechanism regulating PLAT gene expression levels is still unclear. The epigenetic mechanism regulating the PLAT gene expression has been studied in other tissues. Objective We aimed to investigate the methylation levels in the proximal PLAT promoter and their effects on gene expression in NP tissue. Methods We investigated the methylation levels at 3 CpG sites in the proximal PLAT promoter regions (-618, -121, and -105 with respect to the transcription initiation site) by bisulfite pyrosequencing and their effects on the gene expression by quantitative real-time polymerase chain reaction (qPCR) in 20 paired samples of NP and inferior turbinate tissue (IT) from patients with CRS. Results The DNA methylation levels at all CpG sites were higher ( P < .01), and the PLAT expression was lower ( P < .001) in NP compared with IT. The methylation changes at the -618 site showed a negative correlation with the gene expression changes between NP and IT ( r = -.65, P < .01). Conclusions Hypermethylation of PLAT promoter may downregulate the gene expression in NP, leading to excessive fibrin deposition by aberrant coagulation cascade. DNA methylation of proximal PLAT promoter may contribute to NP growth and have a potential as a new therapeutic target.

Expression and Functional Analysis of CST1 in Intractable Nasal Polyps.

In this study, we found Cystatin SN (CST1), a type 2 cystatin subfamily member, to be highly expressed in nasal polyps from patients with intractable chronic rhinosinusitis (CRS) with nasal polyps, using a whole-transcript analysis with next-generation sequencing. Eosinophilic CRS (ECRS) involves nasal polyps that are refractory and recur immediately after endoscopic sinus surgery. We hypothesized that CST1 may contribute to the pathogenesis of ECRS. We examined the expression of CST1 in nasal polyps from patients with ECRS by assessing mRNA expression levels using real-time PCR and immunohistochemistry. CST1 showed significantly greater expression in the epithelial cells of nasal polyps from patients with ECRS than in those from patients who did not have ECRS (non-ECRS). In particular, CST1 showed very strong expression in patients with severe ECRS. The expression of CST1 may be correlated with the recurrent and refractory nature of ECRS. We examined the function of CST1 using nasal epithelial cells and nasal fibroblasts. Stimulation by a combination of IL-4 plus double-stranded RNA plus CST1 significantly elevated mRNA expression levels and protein levels of TSLP in nasal epithelial cells. Stimulation by TSLP or IL-33 significantly elevated mRNA expression levels of CST1 in nasal epithelial cells. Stimulation of CST1 significantly elevated mRNA expression levels of CCL11 and POSTN in nasal fibroblasts. CST1 could amplify eosinophilic infiltration and T-helper cell type 2 inflammation by interacting with epithelial-derived cytokines and fibroblasts on nasal polyps. CST1 may be involved in the pathogenesis of ECRS, and may contribute to the severity and recurrence of CRS with nasal polyps after endoscopic sinus surgery.

Development of an assay system for large scale analysis of HLA class II-binding peptides.

Genes encoding the human leukocyte antigens (HLA) are associated with diverse immunological disorders, including autoimmune diseases and infections. Recently, significant progresses have been made in the HLA typing technologies through the use of next generation sequencers. The reliable platforms for the SNP-based imputation of HLA genotypes have also been established. These technical advancements should enable further identification of HLA associations with diseases. One of the remaining questions is the mechanism through which HLA confer disease susceptibility. As a first step toward comprehensive understanding of functional variations among HLA allele products, we established a protocol to analyze the HLA-binding peptides through quantification of cell-surface HLA expression in an engineered cell line. In this article, we summarize the overview of the cell-surface HLA expression assay, which we plan to use for screening and collection of HLA-peptide interaction profiles for large sets of HLA alleles and peptides.

The significant expression of TRPV3 in nasal polyps of eosinophilic chronic rhinosinusitis.

BACKGROUND: The number of patients with eosinophilic chronic rhinosinusitis (ECRS) has been increasing in recent years in Japan. In ECRS, nasal polyps recur immediately after endoscopic sinus surgery. The molecular biological mechanism underlying the refractoriness of ECRS is unclear. METHODS: Whole-transcriptome analysis with next-generation sequencing (RNA-seq) was conducted to investigate the molecular biological mechanism of ECRS. Real-time PCR, immunohistochemical staining, and immunofluorescence staining were performed to validate the results of RNA-seq. RESULTS: RNA-seq analysis revealed that in the nasal polyps of ECRS, the levels of 3 transcripts were elevated significantly and those of 7 transcripts were diminished significantly. Among the genes encoding these transcripts, TRPV3 (transient receptor potential cation channel, subfamily V, member 3) was identified as the only gene that is highly expressed in ECRS nasal polyps but this gene's expression was not previously detected using DNA microarray analysis in peripheral blood eosinophils. TRPV3 is newly identified here as a gene transcribed in ECRS. Our analysis also revealed that TRPV3 was highly expressed in the infiltrating eosinophils and mucosal epithelium of the nasal polyps of ECRS, and further that the more severe the refractoriness was after surgery, the higher the TRPV3 expression was in nasal polyps. CONCLUSIONS: TRPV3 might play a role in the refractoriness of ECRS. Additional studies are required to evaluate the function of TRPV3 in ECRS.

Generation of a bile salt export pump deficiency model using patient-specific induced pluripotent stem cell-derived hepatocyte-like cells.

Bile salt export pump (BSEP) plays an important role in hepatic secretion of bile acids and its deficiency results in severe cholestasis and liver failure. Mutation of the ABCB11 gene encoding BSEP induces BSEP deficiency and progressive familial intrahepatic cholestasis type 2 (PFIC2). Because liver transplantation remains standard treatment for PFIC2, the development of a novel therapeutic option is desired. However, a well reproducible model, which is essential for the new drug development for PFIC2, has not been established. Therefore, we attempted to establish a PFIC2 model by using iPSC technology. Human iPSCs were generated from patients with BSEP-deficiency (BD-iPSC), and were differentiated into hepatocyte-like cells (HLCs). In the BD-iPSC derived HLCs (BD-HLCs), BSEP was not expressed on the cell surface and the biliary excretion capacity was significantly impaired. We also identified a novel mutation in the 5'-untranslated region of the ABCB11 gene that led to aberrant RNA splicing in BD-HLCs. Furthermore, to evaluate the drug efficacy, BD-HLCs were treated with 4-phenylbutyrate (4PBA). The membrane BSEP expression level and the biliary excretion capacity in BD-HLCs were rescued by 4PBA treatment. In summary, we succeeded in establishing a PFIC2 model, which may be useful for its pathophysiological analysis and drug development.

Genotyping NUDT15 can predict the dose reduction of 6-MP for children with acute lymphoblastic leukemia especially at a preschool age.

The pharmacokinetics among children has been altered dynamically. The difference between children and adults is caused by immaturity in things such as metabolic enzymes and transport proteins. The periods when these alterations happen vary from a few days to some years after birth. We hypothesized that the effect of gene polymorphisms associated with the dose of medicine could be influenced by age. In this study, we analyzed 51 patients with childhood acute lymphoblastic leukemia (ALL) retrospectively. We examined the associations between the polymorphism in NUDT15 and clinical data, especially the dose of 6-mercaptopurine (6-MP). Ten of the patients were heterozygous for the variant allele in NUDT15. In patients under 7 years old with NUDT15 variant allele, the average administered dose of 6-MP was lower than that for the patients homozygous for the wild-type allele (P=0.04). Genotyping of NUDT15 could be a beneficial to estimate the tolerated dose of 6-MP for patients with childhood ALL, especially at a preschool age in Japan. Furthermore, the analysis with stratification by age might be useful in pharmacogenomics among children.

Tie2 Signaling Enhances Mast Cell Progenitor Adhesion to Vascular Cell Adhesion Molecule-1 (VCAM-1) through α4ß1 Integrin.

Mast cell (MC) activation contributes considerably to immune responses, such as host protection and allergy. Cell surface immunoreceptors expressed on MCs play an important role in MC activation. Although various immunoreceptors on MCs have been identified, the regulatory mechanism of MC activation is not fully understood. To understand the regulatory mechanisms of MC activation, we used gene expression analyses of human and mouse MCs to identify a novel immunoreceptor expressed on MCs. We found that Tek, which encodes Tie2, was preferentially expressed in the MCs of both humans and mice. However, Tie2 was not detected on the cell surface of the mouse MCs of the peritoneal cavity, ear skin, or colon lamina propria. In contrast, it was expressed on mouse bone marrow-derived MCs and bone marrow MC progenitors (BM-MCps). Stimulation of Tie2 by its ligand angiopoietin-1 induced tyrosine phosphorylation of Tie2 in MEDMC-BRC6, a mouse embryonic stem cell-derived mast cell line, and enhanced MEDMC-BRC6 and mouse BM-MCp adhesion to vascular cell adhesion molecule-1 (VCAM-1) through α4ß1 integrin. These results suggest that Tie2 signaling induces α4ß1 integrin activation on BM-MCps for adhesion to VCAM-1.