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ABSTRACT: PHF2 is a JmjC family histone demethylase that removes the methyl group from H3K9me2 and works as a coactivator for several metabolism-related transcription factors. In this study, we examined the in vivo role of PHF2 in mice. We generated Phf2 floxed mice, systemic Phf2 null mice by crossing Phf2 floxed mice with CMV-Cre transgenic mice, and tamoxifen-inducible Phf2 knockout mice by crossing Phf2 floxed mice with Cre-ERT2 transgenic mice. Systemic Phf2 null mice had partial neonatal death and growth retardation and exhibited less adipose tissue and reduced adipocyte numbers compared with control littermates. Tamoxifen-induced conditional knockout of PHF2 resulted in impaired adipogenesis in stromal vascular cells from the adipose tissue of tamoxifen-inducible Phf2 knockout mice as well as of Phf2 knocked-down 3T3-L1 cells. PHF2 interacts with CEBPA and demethylates H3K9me2 in the promoters of CEBPA-regulated adipogenic genes. These findings suggest that PHF2 histone demethylase potentiates adipogenesis through interaction with CEBPA in vivo. Taken together, PHF2 may be a novel therapeutic target in the treatment of obesity and the metabolic syndrome.
Diabetes 12/2012; · 8.29 Impact Factor
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ABSTRACT: To elucidate target molecules of white matter development responding to hypothyroidism, global gene expression profiling of cerebral white matter from male rat offspring was performed after maternal exposure to anti-thyroid agents, 6-propyl-2-thiouracil and methimazole, on postnatal day 20. Genes involved in central nervous system development commonly up- or down-regulated among groups treated with anti-thyroid agents. Immunohistochemical distributions of vimentin, Ret proto-oncogene (Ret), deleted in colorectal cancer protein (DCC), and Claudin11 (Cld11) were examined based on the gene expression profile. Immunoreactive cells for vimentin and Ret in the cingulum, and the immunoreactive intensity of Cld11 and DCC in whole white matter were increased by treatment with anti-thyroid agents. Immunoreactive cells for vimentin and Ret were immature astrocytes and oligodendrocytes, respectively. Thus, immunoreactive cells for vimentin and Ret may be quantitatively measurable targets of developmental hypothyroidism in white matter.
Reproductive Toxicology 04/2012; 34(1):93-100. · 3.23 Impact Factor
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Katsuhide Igarashi,
Satoshi Kitajima,
Ken-ichi Aisaki,
Kentaro Tanemura,
Yuhji Taquahashi,
Noriko Moriyama,
Eriko Ikeno,
Nae Matsuda,
Yumiko Saga,
Bruce Blumberg,
Jun Kanno
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ABSTRACT: The human steroid and xenobiotic receptor (SXR), (also known as pregnane X receptor PXR, and NR1I2) is a low affinity sensor that responds to a variety of endobiotic, nutritional and xenobiotic ligands. SXR activates transcription of Cytochrome P450, family 3, subfamily A (CYP3A) and other important metabolic enzymes to up-regulate catabolic pathways mediating xenobiotic elimination. One key feature that demarcates SXR from other nuclear receptors is that the human and rodent orthologues exhibit different ligand preference for a subset of toxicologically important chemicals. This difference leads to a profound problem for rodent studies to predict toxicity in humans. The objective of this study is to generate a new humanized mouse line, which responds systemically to human-specific ligands in order to better predict systemic toxicity in humans. For this purpose, the ligand binding domain (LBD) of the human SXR was homologously knocked-in to the murine gene replacing the endogenous LBD. The LBD-humanized chimeric gene was expressed in all ten organs examined, including liver, small intestine, stomach, kidney and lung in a pattern similar to the endogenous gene expressed in the wild-type (WT) mouse. Quantitative reverse transcription-polymerase chain reaction (RT-PCR) analysis showed that the human-selective ligand, rifampicin induced Cyp3a11 and Carboxylesterase 6 (Ces6) mRNA expression in liver and intestine, whereas the murine-selective ligand, pregnenolone-16-carbonitrile did not. This new humanized mouse line should provide a useful tool for assessing whole body toxicity, whether acute, chronic or developmental, induced by human selective ligands themselves and subsequently generated metabolites that can trigger further toxic responses mediated secondarily by other receptors distributed body-wide.
The Journal of Toxicological Sciences 01/2012; 37(2):373-80. · 1.52 Impact Factor
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Ryoji Fujiki,
Waka Hashiba,
Hiroki Sekine,
Atsushi Yokoyama,
Toshihiro Chikanishi,
Saya Ito,
Yuuki Imai,
Jaehoon Kim,
Housheng Hansen He, Katsuhide Igarashi,
Jun Kanno,
Fumiaki Ohtake,
Hirochika Kitagawa,
Robert G Roeder,
Myles Brown,
Shigeaki Kato
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ABSTRACT: Chromatin reorganization is governed by multiple post-translational modifications of chromosomal proteins and DNA. These histone modifications are reversible, dynamic events that can regulate DNA-driven cellular processes. However, the molecular mechanisms that coordinate histone modification patterns remain largely unknown. In metazoans, reversible protein modification by O-linked N-acetylglucosamine (GlcNAc) is catalysed by two enzymes, O-GlcNAc transferase (OGT) and O-GlcNAcase (OGA). However, the significance of GlcNAcylation in chromatin reorganization remains elusive. Here we report that histone H2B is GlcNAcylated at residue S112 by OGT in vitro and in living cells. Histone GlcNAcylation fluctuated in response to extracellular glucose through the hexosamine biosynthesis pathway (HBP). H2B S112 GlcNAcylation promotes K120 monoubiquitination, in which the GlcNAc moiety can serve as an anchor for a histone H2B ubiquitin ligase. H2B S112 GlcNAc was localized to euchromatic areas on fly polytene chromosomes. In a genome-wide analysis, H2B S112 GlcNAcylation sites were observed widely distributed over chromosomes including transcribed gene loci, with some sites co-localizing with H2B K120 monoubiquitination. These findings suggest that H2B S112 GlcNAcylation is a histone modification that facilitates H2BK120 monoubiquitination, presumably for transcriptional activation.
Nature 11/2011; 480(7378):557-60. · 36.28 Impact Factor
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ABSTRACT: It has recently been demonstrated that genistein (GEN), a phytoestrogen in soy products, is an epigenetic modulator in various types of cells; but its effect on endometrium has not yet been determined. We investigated the effects of GEN on mouse uterine cells, in vivo and in vitro. Oral administration of GEN for 1 week induced mild proliferation of the endometrium in ovariectomized (OVX) mice, which was accompanied by the induction of steroidogenic factor 1 (SF-1) gene expression. GEN administration induced demethylation of multiple CpG sites in the SF-1 promoter; these sites are extensively methylated and thus silenced in normal endometrium. The GEN-mediated promoter demethylation occurred predominantly on the luminal side, as opposed to myometrium side, indicating that the epigenetic change was mainly shown in regenerated cells. Primary cultures of endometrial stromal cell colonies were screened for GEN-mediated alterations of DNA methylation by a high-resolution melting (HRM) method. One out of 20 colony-forming cell clones showed GEN-induced demethylation of SF-1. This clone exhibited a high proliferation capacity with continuous colony formation activity through multiple serial clonings. We propose that only a portion of endometrial cells are capable of receiving epigenetic modulation by GEN.
Biochemical and Biophysical Research Communications 07/2011; 412(2):366-72. · 2.48 Impact Factor
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Atsushi Baba,
Fumiaki Ohtake,
Yosuke Okuno,
Kenichi Yokota,
Maiko Okada,
Yuuki Imai,
Min Ni,
Clifford A Meyer, Katsuhide Igarashi,
Jun Kanno,
Myles Brown,
Shigeaki Kato
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ABSTRACT: Reversible histone methylation and demethylation are highly regulated processes that are crucial for chromatin reorganization and regulation of gene transcription in response to extracellular conditions. However, the mechanisms that regulate histone-modifying enzymes are largely unknown. Here, we characterized a protein kinase A (PKA)-dependent histone lysine demethylase complex, PHF2-ARID5B. PHF2, a jmjC demethylase, is enzymatically inactive by itself, but becomes an active H3K9Me2 demethylase through PKA-mediated phosphorylation. We found that phosphorylated PHF2 then associates with ARID5B, a DNA-binding protein, and induce demethylation of methylated ARID5B. This modification leads to targeting of the PHF2-ARID5B complex to its target promoters, where it removes the repressive H3K9Me2 mark. These findings suggest that the PHF2-ARID5B complex is a signal-sensing modulator of histone methylation and gene transcription, in which phosphorylation of PHF2 enables subsequent formation of a competent and specific histone demethylase complex.
Nature Cell Biology 06/2011; 13(6):668-75. · 19.49 Impact Factor
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ABSTRACT: The balance between androgens and estrogens is very important in the development of the prostate, and even small changes in estrogen levels, including those of estrogen-mimicking chemicals, can lead to serious changes. Bisphenol A (BPA), an endocrine-disrupting chemical, is a well-known, ubiquitous, estrogenic chemical. To investigate the effects of fetal exposure to low-dose BPA on the development of the prostate, we examined alterations of the in situ sex steroid hormonal environment in the mouse urogenital sinus (UGS). In the BPA-treated UGS, estradiol (E(2)) levels and CYP19A1 (cytochrome P450 aromatase) activity were significantly increased compared with those of the untreated and diethylstilbestrol (DES)-treated UGS. The mRNAs of steroidogenic enzymes, Cyp19a1 and Cyp11a1, and the sex-determining gene, Nr5a1, were up-regulated specifically in the BPA-treated group. The up-regulation of mRNAs was observed in the mesenchymal component of the UGS as well as in the cerebellum, heart, kidney, and ovary but not in the testis. The number of aromatase-expressing mesenchymal cells in the BPA-treated UGS was approximately twice that in the untreated and DES-treated UGS. The up-regulation of Esrrg mRNA was observed in organs for which mRNAs of steroidogenic enzymes were also up-regulated. We demonstrate here that fetal exposure to low-dose BPA has the unique action of increasing in situ E(2) levels and CYP19A1 (aromatase) activity in the mouse UGS. Our data suggest that BPA might interact with in situ steroidogenesis by altering tissue components, such as the accumulation of aromatase-expressing mesenchymal cells, in particular organs.
Biology of Reproduction 12/2010; 84(4):734-42. · 4.01 Impact Factor
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Daigo Ikegami,
Minoru Narita,
Satoshi Imai,
Kazuhiko Miyashita,
Rie Tamura,
Michiko Narita,
Shigemi Takagi,
Akiko Yokomizo,
Hideyuki Takeshima,
Takayuki Ando, Katsuhide Igarashi,
Jun Kanno,
Naoko Kuzumaki,
Toshikazu Ushijima,
Tsutomu Suzuki
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ABSTRACT: The intermittent administration of methamphetamine produces behavioral sensitization to methamphetamine. In the limbic forebrain, mainly including the nucleus accumbens, of mice that had been intermittently treated with methamphetamine, we found a significant increase in mRNA of a chemokine, CCR2. This increase was accompanied by a significant increase in histone H3 lysine 4 (H3K4) trimethylation at its promoter. Interestingly, the maintenance of sensitization to methamphetamine-induced hyperlocomotion was significantly decreased in CCR2 knockout mice. These findings suggest that increased CCR2 associated with epigenetic modification after the intermittent administration of methamphetamine may be associated with the maintenance of sensitization to methamphetamine-induced hyperlocomotion.
Addiction Biology 07/2010; 15(3):358-61. · 4.83 Impact Factor
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Daigo Ikegami,
Minoru Narita,
Satoshi Imai,
Kazuhiko Miyashita,
Rie Tamura,
Michiko Narita,
Shigemi Takagi,
Akiko Yokomizo,
Hideyuki Takeshima,
Takayuki Ando, Katsuhide Igarashi,
Jun Kanno,
Naoko Kuzumaki,
Toshikazu Ushijima,
Tsutomu Suzuki
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ABSTRACT: The intermittent administration of methamphetamine produces behavioral sensitization to methamphetamine. In the limbic forebrain, mainly including the nucleus accumbens, of mice that had been intermittently treated with methamphetamine, we found a significant increase in mRNA of a chemokine, CCR2. This increase was accompanied by a significant increase in histone H3 lysine 4 (H3K4) trimethylation at its promoter. Interestingly, the maintenance of sensitization to methamphetamine-induced hyperlocomotion was significantly decreased in CCR2 knockout mice. These findings suggest that increased CCR2 associated with epigenetic modification after the intermittent administration of methamphetamine may be associated with the maintenance of sensitization to methamphetamine-induced hyperlocomotion.
Addiction Biology 06/2010; 15(3):358 - 361. · 4.83 Impact Factor
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Naoko Kuzumaki,
Daigo Ikegami,
Rie Tamura,
Nana Hareyama,
Satoshi Imai,
Michiko Narita,
Kazuhiro Torigoe,
Keiichi Niikura,
Hideyuki Takeshima,
Takayuki Ando, Katsuhide Igarashi,
Jun Kanno,
Toshikazu Ushijima,
Tsutomu Suzuki,
Minoru Narita
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ABSTRACT: Environmental enrichment is an experimental paradigm that increases brain-derived neurotrophic factor (BDNF) gene expression accompanied by neurogenesis in the hippocampus of rodents. In the present study, we investigated whether an enriched environment could cause epigenetic modification at the BDNF gene in the hippocampus of mice. Exposure to an enriched environment for 3-4 weeks caused a dramatic increase in the mRNA expression of BDNF, but not platelet-derived growth factor A (PDGF-A), PDGF-B, vascular endothelial growth factor (VEGF), nerve growth factor (NGF), epidermal growth factor (EGF), or glial fibrillary acidic protein (GFAP), in the hippocampus of mice. Under these conditions, exposure to an enriched environment induced a significant increase in histone H3 lysine 4 (H3K4) trimethylation at the BDNF P3 and P6 promoters, in contrast to significant decreases in histone H3 lysine 9 (H3K9) trimethylation at the BDNF P4 promoter and histone H3 lysine 27 (H3K27) trimethylation at the BDNF P3 and P4 promoters without any changes in the expression of their associated histone methylases and demethylases in the hippocampus. The expression levels of several microRNAs in the hippocampus were not changed by an enriched environment. These results suggest that an enriched environment increases BDNF mRNA expression via sustained epigenetic modification in the mouse hippocampus.
Hippocampus 03/2010; 21(2):127-32. · 5.18 Impact Factor
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Naoko Kuzumaki,
Daigo Ikegami,
Rie Tamura,
Takuya Sasaki,
Keiichi Niikura,
Michiko Narita,
Kazuhiko Miyashita,
Satoshi Imai,
Hideyuki Takeshima,
Takayuki Ando, Katsuhide Igarashi,
Jun Kanno,
Toshikazu Ushijima,
Tsutomu Suzuki,
Minoru Narita
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ABSTRACT: Recent research has suggested that epigenetic mechanisms, which exert lasting control over gene expression without altering the genetic code, could mediate stable changes in brain function. A growing body of evidence supports the idea that epigenetic changes play a role in the etiology of aging and its associated brain dysfunction. The present study was undertaken to evaluate the age-related changes in the expression of doublecortin, which is a marker for neuronal precursors, along with epigenetic modification in the hippocampus of aged mice. In the present study, the doublecortin-positive cells were almost completely absent from the dentate gyrus of the hippocampus of 28-month-old mice. Furthermore, the expression level of doublecortin mRNA was significantly decreased in the hippocampus of aged mice. Under these conditions, a significant decrease in H3K4 trimethylation and a significant increase in H3K27 trimethylation at doublecortin promoters were observed with aging without any changes in the expression of their associated histone methylases and demethylases in the hippocampus. These findings suggest that aging produces a dramatic decrease in the expression of doublecortin along with epigenetic modifications in the hippocampus.
Synapse 03/2010; 64(8):611-6. · 2.94 Impact Factor
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ABSTRACT: Nanos is one of the evolutionarily conserved proteins implicated in germ cell development. We have previously shown that NANOS2 plays an important role in both the maintenance and sexual development of germ cells. However, the molecular mechanisms underlying these events have remained elusive. In our present study, we found that NANOS2 localizes to the P-bodies, known centers of RNA degradation that are abundantly accumulated in male gonocytes. We further identified by immunoprecipitation that the components of the CCR4-NOT deadenylation complex are NANOS2-interacting proteins and found that NANOS2 promotes the localization of CNOT proteins to P-bodies in vivo. We also elucidated that the NANOS2/CCR4-NOT complex has deadenylase activity in vitro, and that some of the RNAs implicated in meiosis interact with NANOS2 and are accumulated in its absence. Our current data thus indicate that the expression of these RNA molecules is normally suppressed via a NANOS2-mediated mechanism. We propose from our current findings that NANOS2-interacting RNAs may be recruited to P-bodies and degraded by the enzymes contained therein through NANOS2-mediated deadenylation.
Proceedings of the National Academy of Sciences 02/2010; 107(8):3594-9. · 9.68 Impact Factor
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Yukie Saegusa,
Gye-Hyeong Woo,
Hitoshi Fujimoto,
Kaoru Inoue,
Miwa Takahashi,
Masao Hirose, Katsuhide Igarashi,
Jun Kanno,
Kunitoshi Mitsumori,
Akiyoshi Nishikawa,
Makoto Shibutani
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ABSTRACT: To determine whether developmental hypothyroidism causes permanent disruption of neuronal development, we first performed a global gene expression profiling study targeting hippocampal CA1 neurons in male rats at the end of maternal exposure to anti-thyroid agents on weaning (postnatal day 20). As a result, genes associated with nervous system development, zinc ion binding, apoptosis and cell adhesion were commonly up- or down-regulated. Genes related to calcium ion binding were up-regulated and those for myelination were often down-regulated. We, then, examined immunohistochemical cellular distribution of Ephrin type A receptor 5 (EphA5) and Tachykinin receptor (Tacr)-3, those selected based on the gene expression profiles, in the hippocampal formation at the adult stage (11-week-old) as well as at the end of exposure. At weaning, both EphA5- and Tacr3-immunoreactive cells with strong intensities appeared in the pyramidal cell layer or stratum oriens of the hippocampal CA1 region. Although the magnitude of the change was decreased at the adult stage, Tacr3 in the CA1 region showed a sustained increase in expressing cells until the adult stage after developmental hypothyroidism. On the other hand, EphA5-expressing cells did not show sustained increase at the adult stage. The results suggest that developmental hypothyroidism caused sustained neuronal expression of Tacr3 in the hippocampal CA1 region, probably reflecting a neuroprotective mechanism for mismigration.
Journal of Veterinary Medical Science 11/2009; 72(2):187-95. · 0.85 Impact Factor
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ABSTRACT: Aryl hydrocarbon receptor (AhR), a ligand-activated transcription factor, is known to mediate a wide variety of pharmacological and toxicological effects caused by polycyclic aromatic hydrocarbons. Recent studies have revealed that AhR is involved in the normal development and homeostasis of many organs. Here, we demonstrate that AhR knockout (AhR KO) mice are hypersensitive to lipopolysaccharide (LPS)-induced septic shock, mainly due to the dysfunction of their macrophages. In response to LPS, bone marrow-derived macrophages (BMDM) of AhR KO mice secreted an enhanced amount of interleukin-1beta (IL-1beta). Since the enhanced IL-1beta secretion was suppressed by supplementing Plasminogen activator inhibitor-2 (Pai-2) expression through transduction with Pai-2-expressing adenoviruses, reduced Pai-2 expression could be a cause of the increased IL-1beta secretion by AhR KO mouse BMDM. Analysis of gene expression revealed that AhR directly regulates the expression of Pai-2 through a mechanism involving NF-kappaB but not AhR nuclear translocator (Arnt), in an LPS-dependent manner. Together with the result that administration of the AhR ligand 3-methylcholanthrene partially protected mice with wild-type AhR from endotoxin-induced death, these results raise the possibility that an appropriate AhR ligand may be useful for treating patients with inflammatory disorders.
Molecular and cellular biology 10/2009; 29(24):6391-400. · 6.06 Impact Factor
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ABSTRACT: To identify differentially regulated molecules related to early and late stages of tumor promotion in a rat two-stage thyroid carcinogenesis model by an antithyroid agent, sulfadimethoxine, microarray-based microdissected lesion-specific gene expression profiling was carried out. Proliferative lesions for profiling were divided into two categories: (i) focal follicular cell hyperplasias (FFCH) and adenomas (Ad) as early lesions; and (ii) carcinomas (Ca) as more advanced. In both cases, gene expression was compared with that in surrounding non-tumor follicular cells. Characteristically, upregulation of cell cycle-related genes in FFCH + Ad, downregulation of genes related to tumor suppression and transcription inhibitors of inhibitor of DNA binding (Id) family proteins in Ca, and upregulation of genes related to cell proliferation and tumor progression in common in FFCH + Ad and Ca, were detected. The immunohistochemical distributions of molecules included in the altered expression profiles were further examined. In parallel with microarray data, increased localization of ceruloplasmin, cyclin B1, and cell division cycle 2 homolog A, and decreased localization of poliovirus receptor-related 3 and Id3 were observed in all types of lesion. Although inconsistent with the microarray data, thyroglobulin immunoreactivity appeared to reduce in Ca. The results thus suggest cell cycling facilitation by induction of M-phase-promoting factor consisting of cyclin B1 and cell division cycle 2 homolog A and generation of oxidative responses as evidenced by ceruloplasmin accumulation from an early stage, as well as suppression of cell adhesion involving poliovirus receptor-related 3 and inhibition of cellular differentiation regulated by Id3. Decrease of thyroglobulin in Ca may reflect dedifferentiation with progression.
Cancer Science 03/2009; 100(4):617-25. · 3.33 Impact Factor
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ABSTRACT: To elucidate the common characteristics of murine radiation-induced myelogenous leukemias, global gene-chip expression profiles were compared with age-matched steady-state bone marrow tissue profiles and spontaneous myelogenous leukemia profiles.
Six each of C3H/He mice-derived radiation-induced and spontaneously developed myelogenous leukemias were analyzed. Bone marrow cells from five each of 2- and 21-month-old mice were used to subtract nonleukemic information in the analysis. mRNAs from individual mice were analyzed separately using 45,101 gene chips followed by computational biological analysis.
First, principal component analysis (PCA) was performed to discriminate the gene expression profiles of individual mice with radiation-induced myelogenous leukemia from those of bone marrow cells from 2- or 21-month-old mice. Discriminant union genes for individual leukemias were then selected, which finally yielded 242 genes, among which six are radiation-related genes including Hus-1, Edf1a2, andVegf-c; 16 are apoptosis/cell-death-related genes, 13 are cell-cycle/cell-growth-related genes, and 50 are suppressor/promoter genes. PCA of these 242 genes consistently enabled the discrimination of the radiation-induced leukemias from the spontaneous leukemias. Second, the other components of the same PCA provided four different eigenvector clusters in an unsupervised manner representing four histopathological findings, with which the differential diagnosis in molecular taxonomy was significant as determined by analysis of variance of the global gene expression profiles.
Discriminant union genes in radiation-induced myelogenous leukemias against spontaneous myelogenous leukemias and age-matched nonleukemic bone marrow profilings generated by unsupervised computational analysis essentially represent probabilistic biomarkers for radiation-induced myelogenous leukemias, which may contribute to developing a model for risk of secondary carcinogenesis in patients treated by whole-body irradiation.
Experimental hematology 01/2009; 37(2):195-205. · 3.11 Impact Factor
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ABSTRACT: To demonstrate induction of delayed central nervous toxicity by disturbing neuronal activities in the developing brain, we administered a single intraperitoneal dose of domoic acid (DA; 1 mg/kg), a potent glutamate receptor agonist, to pregnant female mice at the gestational day of 11.5, 14.5 or 17.5. The dams had recovered from acute symptoms within 24 hr, followed by normal delivery, feeding and weaning. All male offspring mice after weaning were apparently normal in response to handlers during cage maintenance, body weight measurement and to mate mice in group housing conditions. At the age of 11 weeks, our neurobehavior testing battery revealed severe impairment of learning and memory with serious deviances of anxiety-related behaviors. The developed brain of prenatally exposed mice showed myelination failure and the overgrowth of neuronal processes of the limbic cortex neurons. This study indicates that the temporal disturbance of neurotransmission of the developing brain induces irreversible structural and functional damage to offspring which becomes monitorable in their adulthood by a proper battery of neurobehavioral tests.
The Journal of Toxicological Sciences 01/2009; 34 Suppl 2:SP279-86. · 1.52 Impact Factor
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ABSTRACT: A global gene expression profiling specific to the early process of tumor promotion by fenbendazole (FB) or phenobarbital (PB) in a rat two-stage hepatocarcinogenesis model revealed 33 genes to show altered expression in common with both chemicals. The immunohistochemical distribution of transferrin receptor (Tfrc), nuclear receptor subfamily 0, group B, member 2 (Nr0b2) and minichromosome maintenance deficient 6 (MCM6), included in the altered expression profile, were therefore examined in FB- and PB-induced proliferative lesions at both early and late stages of tumor promotion. In addition, immunoexpression of transforming growth factor beta receptor (TGFbetaR) I, TGFbetaRII, phosphatase and tensin homolog deleted on chromosome 10 (PTEN) and phosphorylated phosphatase and tensin homolog deleted on chromosome 10 (pPTEN) was also examined. In the early stage, most hepatocellular foci positive for glutathione S-transferase placental form (GST-P) showed co-expression of TGFbetaRI and lack of PTEN and pPTEN, some GST-P-positive foci co-expressing Tfrc and Nr0b2. In the late stage, selective expression of TGFbetaRI, but not TGFbetaRII, was also observed in many adenomas and carcinomas consistently expressing GST-P. Nr0b2 was variably expressed in the proliferative lesions, irrespective of the carcinogenic stage. Like the GST-P-positive foci, adenomas and carcinomas consistently lacked PTEN and pPTEN. Expression of Tfrc and MCM6 was increased in parallel with the carcinogenic stage. In conclusion, loss of PTEN and dysregulation of transforming growth factor beta signaling can be considered to be involved in rat hepatocarcinogenesis from early stages. Selective expression of Tfrc in proliferative lesions suggests an involvement of changes in iron homeostasis during the process of tumor promotion/progression driven by FB or PB.
Carcinogenesis 07/2008; 29(11):2218-26. · 5.70 Impact Factor
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Takashi Nakamura,
Yuuki Imai,
Takahiro Matsumoto,
Shingo Sato,
Kazusane Takeuchi, Katsuhide Igarashi,
Yoshifumi Harada,
Yoshiaki Azuma,
Andree Krust,
Yoko Yamamoto,
Hiroshi Nishina,
Shu Takeda,
Hiroshi Takayanagi,
Daniel Metzger,
Jun Kanno,
Kunio Takaoka,
T John Martin,
Pierre Chambon,
Shigeaki Kato
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ABSTRACT: Estrogen prevents osteoporotic bone loss by attenuating bone resorption; however, the molecular basis for this is unknown. Here, we report a critical role for the osteoclastic estrogen receptor alpha (ERalpha) in mediating estrogen-dependent bone maintenance in female mice. We selectively ablated ERalpha in differentiated osteoclasts (ERalpha(DeltaOc/DeltaOc)) and found that ERalpha(DeltaOc/DeltaOc) females, but not males, exhibited trabecular bone loss, similar to the osteoporotic bone phenotype in postmenopausal women. Further, we show that estrogen induced apoptosis and upregulation of Fas ligand (FasL) expression in osteoclasts of the trabecular bones of WT but not ERalpha(DeltaOc/DeltaOc) mice. The expression of ERalpha was also required for the induction of apoptosis by tamoxifen and estrogen in cultured osteoclasts. Our results support a model in which estrogen regulates the life span of mature osteoclasts via the induction of the Fas/FasL system, thereby providing an explanation for the osteoprotective function of estrogen as well as SERMs.
Cell 10/2007; 130(5):811-23. · 32.40 Impact Factor
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ABSTRACT: Effects of aromatase inhibitors (AIs) on the human skeletal system due to systemic estrogen depletion are becoming clinically important due to their increasing use as an adjuvant therapy in postmenopausal women with breast cancer. However, possible effects of AIs on human bone cells have remained largely unknown. We therefore studied effects of AIs including the steroidal AI, exemestane (EXE), and non-steroidal AIs, Aromatase Inhibitor I (AI-I) and aminoglutethimide (AGM), on a human osteoblast. We employed a human osteoblast cell line, hFOB, which maintains relatively physiological status of estrogen and androgen pathways of human osteoblasts, i.e., expression of aromatase, androgen receptor (AR), and estrogen receptor (ER) beta. We also employed osteoblast-like cell lines, Saos-2 and MG-63 which expressed aromatase, AR, and ERalpha/beta in order to further evaluate the mechanisms of effects of AIs on osteoblasts. There was a significant increment in the number of the cells following 72 h treatment with EXE in hFOB and Saos-2 but not in MG-63, in which the level of AR mRNA was lower than that in hFOB and Saos-2. Alkaline phosphatase activity was also increased by EXE treatment in hFOB and Saos-2. Pretreatment with the AR blocker, flutamide, partially inhibited the effect of EXE. AI-I exerted no effects on osteoblast cell proliferation and AGM diminished the number of the cells. hFOB converted androstenedione into E2 and testosterone (TST). Both EXE and AI-I decreased E2 level and increased TST level. In a microarray analysis, gene profile patterns following treatment with EXE demonstrated similar patterns as with DHT but not with E2 treatment. The genes induced by EXE treatment were related to cell proliferation, differentiation which includes genes encoding cytoskeleton proteins. We also examined the expression levels of these genes using quantitative RT-PCR in hFOB and Saos-2 treated with EXE and DHT and with/without flutamide. HOXD11 gene known as bone morphogenesis factor and osteoblast growth-related genes were induced by EXE treatment as well as DHT treatment in both hFOB and Saos-2. These results indicated that the steroidal aromatase inhibitor, EXE, stimulated hFOB cell proliferation via both AR dependent and independent pathways.
Bone 05/2007; 40(4):876-87. · 4.02 Impact Factor
