PubMed Health⌕ Search

Biomedical subjects

T Taga

Publications and source records attributed to T Taga.

At least 19 recordsLinked to original sources
PubMed2004

Negative regulatory effect of an oligodendrocytic bHLH factor OLIG2 on the astrocytic differentiation pathway.

In the developing vertebrate nervous system, multipotent neural stem cells produce both neurons and glia. OLIG2 is a basic helix-loop-helix transcription factor that plays critical roles in oligodendrocyte and motor neuron development; however, its role in astrocytic development remains elusive. In this study, we analyzed an effect of OLIG2 on cytokine-induced astrocytic differentiation from mouse telencephalic neuroepithelial cells. We show that the presence of OLIG2 protein leads to inhibition of the promoter activation of astrocyte-specific glial fibrillary acidic protein gene. We found that OLIG2 abolishes complex formation between a transcriptional coactivator p300 and a transcription factor, signal transducer and activator of transcription 3 (STAT3), which is activated by astrocytic differentiation-inducing cytokines, such as leukemia inhibitory factor (LIF). The enforced expression of OLIG2 in neuroepithelial cells inhibits the LIF-induced astrocytic differentiation. We also show that the OLIG2 protein in the nuclei of neural precursor cells disappears in accordance with astrocytic differentiation during culture with LIF. Together, these results reveal a novel molecular function of OLIG2 on the astrocyte development. Cell Death and Differentiation (2004) 11, 196-202. doi:10.1038/sj.cdd.4401332 Published online 24 October 2003

Animals↗
PubMed2001

Endomucin is expressed in embryonic dorsal aorta and is able to inhibit cell adhesion.

Recent studies have suggested the existence of progenitors common to hematopoietic and endothelial cells, called hemangioblasts, in, for instance, embryonic dorsal aorta. To identify a membrane-bound or secretory molecule regulating early hematopoiesis, we screened a cDNA library from dorsal aortas of embryonic day (E) 10.5 mice by a signal sequence trap method and obtained a clone encoding a sialoprotein, endomucin-1. Immunohistochemistry revealed that the endomucin-1 transcript was specifically expressed in the endothelial cells of dorsal aorta of E10.5 mouse embryo. Overexpression of endomucin-1 strongly inhibited adhesion and aggregation of cells, including cultured endothelial cells from E10.5 dorsal aorta. These data suggest that endomucin-1 may play a role in detachment of hematopoietic cells from endothelium during early hematopoiesis.

Amino Acid Sequence↗
PubMed2001

Stereospecific 1,3-migration of an Fe(CO)3 group on acyclic conjugated polyenes: application to remote and iterative asymmetric induction.

The stereochemical outcome of the 1,3- and 1,5-migration of an Fe(CO)3 group on (acyclic polyene)Fe(CO)3 complexes and their application to stereoselective construction of remote and contiguous stereogenic centers are described. Treatment of the [(eta(4)-4-7)triene]Fe(CO)3 complexes 1a-d bearing an electron-withdrawing group on the terminal position of an uncomplexed olefin with a base such as KN(SiMe3)2 (KHMDS) and LiCH2CN induced the 1,3-migration reaction of the Fe(CO)3 group, giving the [(eta4-2-5)triene]Fe(CO)3 complexes 2a-d in moderate to good yields, depending on the electron-withdrawing groups. From an experiment using the chiral (trienenitril)Fe(CO)3 complex 5, it is revealed that the 1,3-migration proceeds with inversion of configuration. Similarly, the 1,5-migration reaction of the[(eta4-6-9)tetraenone]Fe(CO)3 complexes 9 occurred with a catalytic amount of KHMDS, giving the [(eta4-2-5)tetraenone]Fe(CO)3 complexes 10 with retention of configuration. Furthermore, we have succeeded in the first regio- and stereoselective nucleophilic substitution of the (3,5-diene-1,2-diol) Fe(CO)3 complexes (15 --> 24a-h) with various nucleophiles via the ortho esters 21. By using iterative manipulation of the above two reactions, remote stereocontrol of the terminal substituents on acyclic polyene (9 --> 12) and construction of contiguous stereogenic centers (19, 28) have been achieved.

Journal Article↗
PubMed2001

Astrocyte differentiation of fetal neuroepithelial cells involving cardiotrophin-1-induced activation of STAT3.

Cardiotrophin-1 (CT-1) belongs to the interleukin (IL-)6 family of cytokines that share membrane glycoprotein 130 (gp130) as a receptor component critical for signal transduction. We here observed that CT-1 was expressed in mouse fetal neuroepithelial cells, and was capable of inducing astrocyte differentiation from these cells in a synergistic manner with bone morphogenetic protein (BMP)-2, whose expression was also found in the fetal brain. CT-1-induced astrocyte differentiation was solely gp130-dependent. CT-1-stimulation led to promoter activation of the gene for an astrocyte marker, glial fibrillary acidic protein (GFAP), which was clearly inhibited by expression of a dominant negative form of a gp130-downstream transcription factor, signal transducer and activator of transcription 3(STAT3), or by introduction of a mutation in a single STAT3-binding site in the promoter, suggesting a critical role of STAT3 in the CT-1-induced GFAP transcription. These results suggest that astrocyte differentiation in the developing brain involves CT-1-signaling which cooperates with BMP2.

Animals↗
PubMed2001

BMP2-mediated alteration in the developmental pathway of fetal mouse brain cells from neurogenesis to astrocytogenesis.

We show that when telencephalic neural progenitors are briefly exposed to bone morphogenetic protein 2 (BMP2) in culture, their developmental fate is changed from neuronal cells to astrocytic cells. BMP2 significantly reduced the number of cells expressing microtubule-associated protein 2, a neuronal marker, and cells expressing nestin, a marker for undifferentiated neural precursors, but BMP2 increased the number of cells expressing S100-beta, an astrocytic marker. In telencephalic neuroepithelial cells, BMP2 up-regulated the expression of negative helix-loop-helix (HLH) factors Id1, Id3, and Hes-5 (where Hes is homologue of hairy and Enhancer of Split) that inhibited the transcriptional activity of neurogenic HLH transcription factors Mash1 and neurogenin. Ectopic expression of either Id1 or Id3 (where Id is inhibitor of differentiation) inhibited neurogenesis of neuroepithelial cells, suggesting an important role for these HLH proteins in the BMP2-mediated changes in the neurogenic fate of these cells. Because gliogenesis in the brain and spinal cord, derived from implanted neural stem cells or induced by injury, is responsible for much of the failure of neuronal regeneration, this work may lead to a therapeutic strategy to minimize this problem.

Animals↗
PubMed2001

Directly linked soluble IL-6 receptor-IL-6 fusion protein induces astrocyte differentiation from neuroepithelial cells via activation of STAT3.

Signals of interleukin 6 (IL-6) are transduced by binding of IL-6 to its cell surface receptor (IL-6R) and subsequent association of the resultant IL-6/IL-6R complex with gp130, the signal transducing receptor component utilized in common by all the IL-6 family of cytokines. A soluble form of IL-6R (sIL-6R), which lacks transmembrane and cytoplasmic regions, retains the ability to bind IL-6 and signal through gp130. We show here that a fusion protein of sIL-6R and IL-6 without a polypeptide linker, termed FP6, induces differentiation of astrocytes from fetal mouse neuroepithelial cells as potently as a representative IL-6 family cytokine, leukaemia inhibitory factor (LIF). FP6 has a potential to activate a transcription factor, signal transducer and activator of transcription 3 (STAT3), and mitogen-activated protein kinases, ERK1 and ERK2, in these cells as does LIF. FP6 activates a promoter of the gene for an astrocytic marker, glial fibrillary acidic protein (GFAP), in neuroepithelial cells. This activation is virtually abolished by ectopic expression of a dominant-negative form of STAT3, or by introducing a point mutation into the STAT3 response element located in the GFAP promoter. These results suggest that FP6 induces astrocyte differentiation from neuroepithelial cells through STAT3 activation and that FP6 could be of use as a substitute for natural IL-6 family cytokines.

Animals↗
PubMed2001

Signaling crosstalk underlying synergistic induction of astrocyte differentiation by BMPs and IL-6 family of cytokines.

We here show that bone morphogenetic protein (BMP) 7 acted in synergy with the distinct type of cytokines, leukemia inhibitory factor (LIF) and interleukin (IL) 6 that are in the IL-6 family, to induce astrocyte differentiation from neuroepithelial cells as assessed by expression of glial fibrillary acidic protein (GFAP). In this synergistic action, transcription factors, Smads and STAT3 (for signal transducer and activator of transcription 3) activated by respective group of cytokines, as well as a transcriptional coactivator p300 were essential. Taken together with our previous finding that the synergistic astrocyte induction by BMP2 and LIF is attributed to the complex formation of Smads and STAT3 bridged by p300, it is conceivable that this complex formation is a mechanism utilized in common by two different types of cytokines belonging to the BMP and IL-6 families in order to synergistically induce astrocyte differentiation.

Animals↗
PubMed2001

A new expression cloning strategy for isolation of substrate-specific kinases by using phosphorylation site-specific antibody.

Signal transduction from cell surface receptors to the nucleus is regulated in most part by protein phosphorylation. For the purpose of identification of kinases which play an important role at a particular phosphorylation step in a series of signal transduction pathways, we have developed a new expression-screening method using a phosphorylation site specific antibody and a vector encoding substrate polypeptide. We have applied this method for screening kinases which phosphorylate STAT3 at serine(727). In this screening, antibody (PS727 antibody) specifically recognizing STAT3 in which serine(727) is phosphorylated was first prepared. Escherichia coli, bacteria expressing a serine(727)-containing fragment of STAT3 which was fused to glutathione-S-transferase (GST) (GST-STAT3-WT) were infected by lambda phage cDNA expression libraries. Phosphorylation of GST-STAT3-WT was effectively performed in E. coli as expected, and clones positive for PS727 antibody immunoreactivity were selected. Isolated 53 clones encode four serine/threonine kinases; extracellular signal regulated kinase 1 (ERK1/p44-MAPK), dual specificity Yak1 related kinase (DYRK), dual specificity Yak1 related kinase 2 (DYRK2) and homeodomain interacting protein kinase 2 (HIPK2). These kinases have a potential to phosphorylate serine(727) in STAT3 protein also in mammalian cells. The present method is considered to be applicable in general to isolate kinases.

Amino Acid Sequence↗
PubMed2001

Fate alteration of neuroepithelial cells from neurogenesis to astrocytogenesis by bone morphogenetic proteins.

Bone morphogenetic proteins (BMPs), a class of cytokines belonging to the transforming growth factor-beta superfamily, have been shown to play a wide variety of roles during development including those in the central nervous system. We here report that BMP2, BMP4 and BMP7 have an equivalent potential to inhibit neurogenesis and concomitantly induce astrocytogenesis of mouse fetal neuroepithelial cells. We further show that these BMPs activate a promoter of the gene for negative helix-loop-helix (HLH) factor, Id1, which is known to inhibit the function of such neurogenic transcription factors as Mash1 and neurogenin. These results suggest that BMP2, BMP4 and BMP7 alternate the fate of neuroepithelial cells from neuronal type to astrocytic one via a common mechanism involving negative HLH factor.

Activin Receptors, Type I↗
PubMed2001

Ligand recognition by the vitamin D receptor.

Three-dimensional structure of the ligand binding domain (LBD) of the vitamin D receptor (VDR) docked with the natural ligand 1 alpha,25-dihydroxyvitamin D(3) [1,25-(OH)(2)D(3)] has been mostly solved by the X-ray crystallographic analysis of the deletion mutant (VDR-LBD Delta 165-215). The important focus, from now on, is how the VDR recognizes and interacts with potent synthetic ligands. We now report the docking models of the VDR with three functionally and structurally interesting ligands, 22-oxa-1,25-(OH)(2)D(3) (OCT), 20-epi-1,25-(OH)(2)D(3) and 20-epi-22-oxa-24,26,27-trihomo-1,25-(OH)(2)D(3). In parallel with the computational docking studies, we prepared twelve one-point mutants of amino acid residues lining the ligand binding pocket of the VDR and examined their transactivation potency induced by 1,25-(OH)(2)D(3) and these synthetic ligands. The results indicate that L233, R274, W286, H397 and Y401 are essential for holding the all ligands tested, S278 and Q400 are not important at all, and the importance of S237, V234, S275, C288 and H305 is variable depending on the side-chain structure of the ligands. Based on these studies, we suggested key structural factors to bestow the selective action on OCT and the augmented activities on 20-epi-ligands. Furthermore, the docking models coincided well with our proposed active space-region theory of vitamin D based on the conformational analyses of ligands.

Amino Acids↗
PubMed2001

DNA methylation is a critical cell-intrinsic determinant of astrocyte differentiation in the fetal brain.

Astrocyte differentiation, which occurs late in brain development, is largely dependent on the activation of a transcription factor, STAT3. We show that astrocytes, as judged by glial fibrillary acidic protein (GFAP) expression, never emerge from neuroepithelial cells on embryonic day (E) 11.5 even when STAT3 is activated, in contrast to E14.5 neuroepithelial cells. A CpG dinucleotide within a STAT3 binding element in the GFAP promoter is highly methylated in E11.5 neuroepithelial cells, but is demethylated in cells responsive to the STAT3 activation signal to express GFAP. This CpG methylation leads to inaccessibility of STAT3 to the binding element. We suggest that methylation of a cell type-specific gene promoter is a pivotal event in regulating lineage specification in the developing brain.

Animals↗
PubMed2001

Interaction between DNA-cationic liposome complexes and erythrocytes is an important factor in systemic gene transfer via the intravenous route in mice: the role of the neutral helper lipid.

Recent studies have indicated that there are many barriers to successful systemic gene delivery via cationic lipid vectors using the intravenous route. The purpose of this study was to investigate the effect of binding and interaction between erythrocytes, a major constituent of blood cells, and the complexes, in relation to the role of the helper lipid, on the in vivo gene delivery to the lung following intravenous injection. We used three types of cationic lipid vectors, DNA-DOTMA/Chol liposome complexes, DNA-DOTMA liposome complexes, and DNA-DOTMA/DOPE liposome complexes. Although the three types of vectors bind to murine blood cells in vivo and in vitro, DOTMA/Chol and DOTMA complexes with a higher in vivo transfection activity do not induce fusion between erythrocytes, whereas DOTMA/DOPE complexes, a less efficient vector in vivo, induce fusion between the erythrocytes after a short incubation period. Pre-incubation of DOTMA/DOPE complexes with erythrocytes significantly reduced the transfection efficiency while DOTMA/Chol- and DOTMA complexes were more resistant to such treatment. The differences in the physicochemical and structural properties of these complexes could explain the differences in interaction with erythrocytes and subsequent gene expression. Lipids in DOTMA/Chol and DOTMA complexes have a stable lamellar structure. However, lipids in DOTMA/DOPE complexes have a highly curved structure with high fluidity. These results indicate that the interaction with erythrocytes depends on the properties of the cationic lipid vectors and this is an important factor for intravenous gene delivery using cationic lipid vectors.

Animals↗
PubMed2001

Inhibition of BMP2-induced, TAK1 kinase-mediated neurite outgrowth by Smad6 and Smad7.

BACKGROUND: BMP2 is known to play a wide variety of roles, including some in the development of the nervous system. This cytokine has been reported to induce neurite outgrowth in rat pheochromocytoma PC12 cells via the activation of a p38 MAP kinase, although its regulatory mechanism remains largely to be elucidated. RESULTS: BMP2-induced neurite outgrowth in PC12 cells was inhibited by the introduction of a kinase-negative form of a MAP kinase kinase kinase, TAK1, an upstream regulatory kinase for p38 kinase. Following BMP2 stimulation, the expression of Smad6 and Smad7, inhibitory Smad species that are known to inhibit the BMP2-restricted Smad species, Smad1, Smad5 and Smad8, was up-regulated. Unexpectedly, over-expression of either Smad6 or Smad7 in PC12 cells repressed the BMP2-induced neurite outgrowth and severely impeded the p38 kinase pathway. Both of these inhibitory Smads were found to interact physically with TAK1-binding protein, a molecule required for TAK1 activation. CONCLUSIONS: This study demonstrates that BMP2-induced neurite outgrowth in PC12 cells involves activation of the TAK1-p38 kinase pathway which is inhibited by Smad6 and Smad7.

Animals↗
PubMed2001

Brain from bone: efficient "meta-differentiation" of marrow stroma-derived mature osteoblasts to neurons with Noggin or a demethylating agent.

Bone marrow stromal cells are able to differentiate into adipogenic, chondrogenic, myogenic, osteogenic, and cardiomyogenic lineages, all of which are limited to a mesoderm-derived origin. In this study, we showed that neurons, which are of an ectoderm-origin, could be generated from marrow-derived stromal cells by specific inducers, fibronectin/ornithine coating, and neurosphere formation. The neurons generated from marrow stroma formed neurites, expressed neuron-specific markers and genes, and started to respond to depolarizing stimuli as functional mature neurons. Among stromal cells, isolated mature osteoblasts which had strong in vivo osteogenic activity could be efficiently converted into functional neurons. This transdifferentiation or meta-differentiation was enhanced by Noggin, an inhibitor of bone morphogenetic proteins, in comparison with 5-azacytidine, a demethylating agent capable of altering the gene expression pattern. Marrow stroma is therefore a potential source of cells for neural cell transplantation.

Animals↗
PubMed2001

Sesquiterpene glucosides from anti-leukotriene B4 release fraction of Taraxacum officinale.

Chemical examination of the MeOH extract of the root of Taraxacum officinale, which exhibited inhibitory activity on the formation of leukotriene B4 from activated human neutrophils, has resulted in the isolation of 14-O-beta-D-glucosyl-11,13-dihydro-taraxinic acid (1) and 14-O-beta-D-glucosyl-taraxinic acid (2). The absolute stereostructure of 1 has been established by X-ray chrystallographic examination.

Anti-HIV Agents↗
PubMed2001

Preferential susceptibility of brain tumors to the antiangiogenic effects of an alpha(v) integrin antagonist.

OBJECTIVE: Brain tumors are highly angiogenic, and their growth and spread depend on the generation of new blood vessels. We examined the effect of the cyclic peptide antagonist pentapeptide EMD 121974, an antiangiogenic agent, on orthotopic and heterotopic brain tumor growth. METHODS: The human brain tumor cell lines DAOY (medulloblastoma) and U87 MG (glioblastoma) were injected into either the forebrain (orthotopic) or the subcutis (heterotopic) of nude mice, and daily systemic treatment with the active peptide was initiated after tumors were established. RESULTS: All control animals with orthotopic brain tumors and that received the inactive peptide EMD 135981 daily died as a result of tumor progression within 4 to 6 weeks; tumors measured 3 to 5 mm in diameter. In contrast, mice with orthotopic tumors that were treated daily with the active peptide survived for more than 16 weeks, and histological examination of the brains after 4, 8, and 12 weeks showed either no tumors or microscopic residual tumors. The growth of these brain tumor cells injected simultaneously or separately into the subcutis of nude mice (heterotopic model) was not affected by the active peptide, suggesting that the brain environment is a critical determinant of brain tumor susceptibility to growth inhibition by this pentapeptide. CONCLUSION: The cyclic pentapeptide EMD 121974 may become a treatment option specific to brain tumors. Because of its antiangiogenic effect, its use may be especially indicated after tumors are removed surgically.

Allantois↗
PubMed2001

Chemotherapy-induced unconjugated hyperbilirubinemia caused by a mutation of the bilirubin uridine-5'-diphosphate-glucuronosyltransferase gene.

Chemotherapy for malignant neoplasms sometimes causes unconjugated hyperbilirubinemia in the absence of liver dysfunction. We analyzed the association of chemotherapy-induced hyperbilirubinemia with mutations of the bilirubin uridine-5'-diphosphate (UDP)-glucuronosyltransferase gene (UGT1A1) from two leukemic patients in whom chemotherapy resulted in a hyperbilirubinemic response. We isolated genomic DNA from peripheral blood samples and amplified UGT1A1 by polymerase chain reaction. The amplified DNA fragments were analyzed by direct sequencing. The genes of the two patients revealed an identical heterozygous missense mutation in exon 1 (211G-->A: G71R). This UGT1A1 mutation may be the basis of chemotherapy-induced unconjugated hyperbilirubinemia.

Adolescent↗