The E2F6 Transcription Factor is Associated with the Mammalian SUZ12-Containing Polycomb Complex.

The Polycomb group protein (PcG) SUZ12 forms Polycomb repressive complexes together with histone methyltransferase EZH2. Although the complexes have been demonstrated to be involved in epigenetic maintenance of gene expression in a transcriptional repressive state, it is unclear how they are recruited to the target genes. Here we report that SUZ12 directly interacts with site-specific transcriptional repressor E2F6 and forms a complex together with EZH2. SUZ12 interacts with E2F6 selectively among the E2F family proteins and E2F6- containing SUZ12-EZH2 complex was biochemically purified from HEK293 cells stably expressing Flag-tagged SUZ12. Chromatin immunoprecipitation assays revealed the target genes of the E2F6-SUZ12-EZH2 complex. Contrary to expectation, the promoter regions of these genes are not or only weakly tri-methylated at histone H3-K27, and their expression is down-regulated by depletion of EZH2. Given that the transactivation function of SUZ12-EZH2 has been previously reported, the inhibitory effect on E2F6-mediated transcriptional repression by physical interaction can be considered a candidate mechanism of gene activation by these PcGs.

Genome-wide association study revealed novel loci which aggravate asymptomatic hyperuricaemia into gout.

OBJECTIVE: The first ever genome-wide association study (GWAS) of clinically defined gout cases and asymptomatic hyperuricaemia (AHUA) controls was performed to identify novel gout loci that aggravate AHUA into gout. METHODS: We carried out a GWAS of 945 clinically defined gout cases and 1003 AHUA controls followed by 2 replication studies. In total, 2860 gout cases and 3149 AHUA controls (all Japanese men) were analysed. We also compared the ORs for each locus in the present GWAS (gout vs AHUA) with those in the previous GWAS (gout vs normouricaemia). RESULTS: This new approach enabled us to identify two novel gout loci (rs7927466 of CNTN5 and rs9952962 of MIR302F) and one suggestive locus (rs12980365 of ZNF724) at the genome-wide significance level (p<5.0×10-8). The present study also identified the loci of ABCG2, ALDH2 and SLC2A9. One of them, rs671 of ALDH2, was identified as a gout locus by GWAS for the first time. Comparing ORs for each locus in the present versus the previous GWAS revealed three 'gout vs AHUA GWAS'-specific loci (CNTN5, MIR302F and ZNF724) to be clearly associated with mechanisms of gout development which distinctly differ from the known gout risk loci that basically elevate serum uric acid level. CONCLUSIONS: This meta-analysis is the first to reveal the loci associated with crystal-induced inflammation, the last step in gout development that aggravates AHUA into gout. Our findings should help to elucidate the molecular mechanisms of gout development and assist the prevention of gout attacks in high-risk AHUA individuals.

GWAS of clinically defined gout and subtypes identifies multiple susceptibility loci that include urate transporter genes.

OBJECTIVE: A genome-wide association study (GWAS) of gout and its subtypes was performed to identify novel gout loci, including those that are subtype-specific. METHODS: Putative causal association signals from a GWAS of 945 clinically defined gout cases and 1213 controls from Japanese males were replicated with 1396 cases and 1268 controls using a custom chip of 1961 single nucleotide polymorphisms (SNPs). We also first conducted GWASs of gout subtypes. Replication with Caucasian and New Zealand Polynesian samples was done to further validate the loci identified in this study. RESULTS: In addition to the five loci we reported previously, further susceptibility loci were identified at a genome-wide significance level (p<5.0×10-8): urate transporter genes (SLC22A12 and SLC17A1) and HIST1H2BF-HIST1H4E for all gout cases, and NIPAL1 and FAM35A for the renal underexcretion gout subtype. While NIPAL1 encodes a magnesium transporter, functional analysis did not detect urate transport via NIPAL1, suggesting an indirect association with urate handling. Localisation analysis in the human kidney revealed expression of NIPAL1 and FAM35A mainly in the distal tubules, which suggests the involvement of the distal nephron in urate handling in humans. Clinically ascertained male patients with gout and controls of Caucasian and Polynesian ancestries were also genotyped, and FAM35A was associated with gout in all cases. A meta-analysis of the three populations revealed FAM35A to be associated with gout at a genome-wide level of significance (p meta =3.58×10-8). CONCLUSIONS: Our findings including novel gout risk loci provide further understanding of the molecular pathogenesis of gout and lead to a novel concept for the therapeutic target of gout/hyperuricaemia.

Dual effect of AMD3100, a CXCR4 antagonist, on bleomycin-induced lung inflammation.

The chemokine receptor CXCR4, which binds the chemokine stromal cell-derived factor 1, has been reported to be involved in the chemotaxis of inflammatory cells. In addition, AMD3100, an antagonist of CXCR4, has been reported to be an attractive drug candidate for therapeutic intervention in several disorders in which CXCR4 is critically involved. However, little is known about the therapeutic value of AMD3100 in the treatment of pulmonary fibrosis. In this study, we examined the effects of AMD3100 on a murine bleomycin-induced pulmonary fibrosis model. Concurrent administration of AMD3100 and bleomycin apparently attenuated bleomycin-induced pulmonary inflammation. In this process, an inhibition of neutrophil recruitment at early stage followed by the decrease of other inflammatory cell recruitment in the lung were observed. In addition, it also inhibited the expression of cytokines, including MCP-1, MIP-2, MIP-1alpha, and TGF-beta. In contrast, when AMD3100 was administered following bleomycin treatment, the bleomycin-induced lung inflammation progressed and resulted in severe pulmonary fibrosis. In this process, an increase of inflammatory cell recruitment, an up-regulation of lung MCP-1 and TGF-beta, and a remarkable activation of p44/42 MAPK in neutrophils were observed. U0126, an inhibitor of p44/42 MAPK, significantly abolished these effects. Thus, AMD3100 has dual effect on bleomycin-induced pulmonary fibrosis. Difference of inflammatory cell recruitment and activation might be associated with the dual effect of AMD3100 on bleomycin-induced pulmonary fibrosis.

Increased expression of TRAIL receptor 3 on eosinophils in Churg-Strauss syndrome.

OBJECTIVE: Prolonged survival of eosinophils plays an important role in the pathogenesis of Churg-Strauss syndrome (CSS); however, its detailed molecular mechanism is still unclear. TRAIL and its receptors are expressed on a variety of cells, including eosinophils. In this study, we examined the expression of TRAIL receptors on eosinophils from patients with CSS. METHODS: TRAIL receptor expression was assessed on eosinophils from healthy volunteers, patients with CSS, patients with asthma, and patients with hypereosinophilia due to parasitic infection. TRAIL-induced apoptosis of eosinophils was compared between the patients with CSS and patients with asthma. RNA interference was used to assess the effects of suppression of TRAIL receptor 3. RESULTS: Expression of TRAIL receptor 3, a decoy receptor that acts as an antiapoptotic receptor, on eosinophils from patients with CSS was significantly higher than that in the other subjects. Moreover, in CSS, serum TRAIL receptor 3 levels showed a significant positive correlation with peripheral eosinophil counts, tissue-infiltrating eosinophils stained positive for this receptor, and peripheral T cells expressed TRAIL on their surface. Compared with asthma patients, eosinophils from CSS patients showed a significantly lower percentage of recombinant TRAIL, less autologous T cell-induced apoptosis, and decreased level of active caspase 3. Suppression of TRAIL receptor 3 through RNA interference significantly increased the recombinant TRAIL-induced apoptosis of eosinophils from CSS patients. CONCLUSION: Increased expression of TRAIL receptor 3 on eosinophils from patients with CSS was observed. These alterations in TRAIL receptor 3 expression might be involved in the molecular pathogenesis of CSS eosinophilia.

Discoidin domain receptor 1 contributes to eosinophil survival in an NF-kappaB-dependent manner in Churg-Strauss syndrome.

Churg-Strauss syndrome (CSS) is a systemic disease that shows marked eosinophilia along with eosinophil infiltration in the tissue. Prolonged eosinophil survival plays an important role in the pathogenesis of CSS; however, its detailed molecular mechanism remains unclear. Discoidin domain receptor 1 (DDR1) is a receptor tyrosine kinase, and its ligand is collagen. DDR1 was expressed in human leukocytes and fibroblasts, and it plays an important role in leukocyte cytokine production and fibroblast survival in an NF-kappaB-dependent manner. In this study, we examined in vitro and in vivo eosinophil DDR1 expression and its function in CSS patients. The expression level of DDR1 was significantly higher in the eosinophils of CSS patients, and the predominant isoform was DDR1b. Immunohistochemical findings revealed that the tissue-infiltrating eosinophils expressed endogenous DDR1. In CSS patients, DDR1 activation inhibited Fas agonistic antibody-induced apoptosis and up-regulated Fas agonistic antibody-induced cytokine production of eosinophils in an NF-kappaB-dependent manner. Suppression of DDR1 expression in the eosinophils by using RNA interference and addition of the DDR1-blocking protein abolished these effects. We propose that DDR1 contributes to the eosinophil survival in the tissue microenvironment of CSS and that it might be involved in the development of CSS.

Discoidin domain receptor 1 contributes to the survival of lung fibroblast in idiopathic pulmonary fibrosis.

Idiopathic pulmonary fibrosis (IPF), characterized by fibroblast proliferation and accumulation of extracellular matrix, including collagen, is a chronic progressive disorder that results in lung remodeling and fibrosis. However, the cellular mechanisms that may make fibroblasts resistant to apoptosis have not been completely elucidated. Discoidin domain receptor 1 (DDR1), a receptor tyrosine kinase whose ligand is collagen, is expressed in vivo and contributes in vitro to leukocyte differentiation and nuclear factor (NF)-kappaB activation, which may play an important role in fibroblast survival. In this study, we examined in vivo and in vitro DDR1 expression and its role in cell survival using fibroblasts obtained from IPF and non-IPF patients. Immunohistochemically, fibroblasts present in fibroblastic foci expressed endogenous DDR1. The DDR1 expression level was significantly higher in fibroblasts from IPF patients, and the predominant isoform was DDR1b. In IPF patients, DDR1 activation in fibroblasts inhibited Fas ligand-induced apoptosis and resulted in NF-kappaB nuclear translocation. Suppression of DDR1 expression in fibroblasts by siRNA abolished these effects, and an NF-kappaB inhibitor abrogated the anti-apoptotic effect of DDR1 activation. We propose that DDR1 contributes to fibroblast survival in the tissue microenvironment of IPF and that DDR1 up-regulation may occur in other fibroproliferative lung diseases as well.

Suppression of discoidin domain receptor 1 by RNA interference attenuates lung inflammation.

Discoidin domain receptor 1 (DDR1) is a receptor tyrosine kinase whose ligand is collagen. Recently, we have reported the association of DDR1 in the cytokine production of human leukocytes in in vitro and in vivo expression in idiopathic pulmonary fibrosis. However, its role in in vivo inflammation has not been fully elucidated. Small interference RNA (siRNA) can induce specific suppression of in vitro and in vivo gene expression. In this study, using a bleomycin-induced pulmonary fibrosis mouse model, we administered siRNA against DDR1 transnasally and evaluated histological changes, cytokine expression, and signaling molecule activation in the lungs. Histologically, siRNA against DDR1 successfully reduced in vivo DDR1 expression and attenuated bleomycin-induced infiltration of inflammatory cells. Furthermore, it significantly reduced inflammatory cell counts and concentrations of cytokines such as MCP-1, MIP-1alpha, and MIP-2 in bronchoalveolar lavage fluid. Subsequently, bleomycin-induced up-regulation of TGF-beta in bronchoalveolar lavage fluid was significantly inhibited, and collagen deposition in the lungs was reduced. Furthermore, siRNA against DDR1 significantly inhibited bleomycin-induced P38 MAPK activation in the lungs. Considered together, we propose that DDR1 contributes to the development of bleomycin-induced pulmonary inflammation and fibrosis.

Desert hedgehog-patched 2 expression in peripheral nerves during Wallerian degeneration and regeneration.

Hedgehog proteins are important in the development of the nervous system. As Desert hedgehog (Dhh) is involved in the development of peripheral nerves and is expressed in adult nerves, it may play a role in the maintenance of adult nerves and degeneration and regeneration after injury. We firstly investigated the Dhh-receptors, which are expressed in mouse adult nerves. The Dhh receptor patched(ptc)2 was detected in adult sciatic nerves using RT-PCR, however, ptc1 was undetectable under the same experimental condition. Using RT-PCR in purified cultures of mouse Schwann cells and fibroblasts, we found ptc2 mRNA in Schwann cells, and at much lower levels, in fibroblasts. By immunohistochemistry, Ptc2 protein was seen on unmyelinated nerve fibers. Then we induced crush injury to the sciatic nerves of wild-type (WT) and dhh-null mice and the distal stumps of injured nerves were analyzed morphologically at different time points and expression of dhh and related receptors was also measured by RT-PCR in WT mice. In dhh-null mice, degeneration of myelinated fibers was more severe than in WT mice. Furthermore, in regenerated nerves of dhh-null mice, minifascicular formation was even more extensive than in dhh-null intact nerves. Both dhh and ptc2 mRNA levels were down-regulated during the degenerative phase postinjury in WT mice, while levels rose again during the phase of nerve regeneration. These results suggest that the Dhh-Ptc2 signaling pathway may be involved in the maintenance of adult nerves and may be one of the factors that directly or indirectly determines the response of peripheral nerves to injury.

Involvement of discoidin domain receptor 1 in the deterioration of pulmonary sarcoidosis.

The prognosis of sarcoidosis with pulmonary infiltrates differs in each case, and several cytokines are reported to contribute to its deterioration. However, the detailed mechanism has not been fully elucidated. Discoidin domain receptor 1 (DDR1) is a receptor tyrosine kinase activated by collagen and associated with cytokine production from inflammatory cells. We previously reported the functional expression of DDR1 on CD14-positive bronchoalveolar lavage fluid (BALF) cells in vivo. In this study, we hypothesized that DDR1 might be associated with the deterioration of pulmonary sarcoidosis (PS), and investigated 33 patients with sarcoidosis with pulmonary infiltrates, prospectively. We found that patients with deteriorated PS showed significantly higher DDR1 expression in CD14-positive BALF cells predominant with DDR1b isoforms. Activation of DDR1 induced monocyte chemoattractant protein-1 (MCP-1) and matrix metalloproteinase-9 (MMP-9) production in a p38 mitogen-activated protein kinase-dependent manner from CD14-positive BALF cells of patients with deteriorated sarcoidosis. DDR1 activation also induced NF-kappaB nuclear translocation in CD14-positive BALF cells of patients with deteriorated PS. The inhibitor of NF-kappaB inhibited the production of MCP-1 and MMP-9. We propose that DDR1 is associated with the deterioration of pulmonary sarcoidosis.

Activation of discoidin domain receptor 1 on CD14-positive bronchoalveolar lavage fluid cells induces chemokine production in idiopathic pulmonary fibrosis.

Discoidin domain receptor 1 (DDR1) is a receptor tyrosine kinase activated by collagen. We previously reported the functional expression of DDR1 on human monocyte-derived macrophages in vitro; however, information regarding its role in diseases is limited. Idiopathic pulmonary fibrosis (IPF) is a chronic lung disease, and the lesions contain an abundance of collagen. In this study, we examined DDR1 expression on bronchoalveolar lavage fluid (BALF) cells and investigated its functionality using samples obtained from 28 IPF patients, 13 chronic obstructive pulmonary disease patients, and 14 healthy volunteers. The DDR1 expression level in CD14-positive BALF cells was higher in IPF patients than in chronic obstructive pulmonary disease patients or healthy volunteers. The predominant isoform was DDR1b in the IPF group, while DDR1a was predominant in the other two groups. Using immunohistochemical analysis, we also detected DDR1 expression on infiltrating inflammatory cells in the IPF lesion. In IPF patients, DDR1 activation induced the production of MCP-1, IL-8, MIP-1 alpha, and matrix metalloproteinase-9 (MMP-9) from CD14-positive BALF cells in a p38 MAPK-dependent manner. In contrast, DDR1 activation of CD14-positive BALF cells in the other groups did not induce the production of these chemokines or MMP-9. These chemokines and MMP-9 contribute to the development of IPF and, therefore, we suggest that DDR1 might be associated with the pathogenesis of IPF in the tissue microenvironment.