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M Seto

Publications and source records attributed to M Seto.

At least 73 records · Page 4Linked to original sources
PubMed1999

Identification of heterologous translocation partner genes fused to the BCL6 gene in diffuse large B-cell lymphomas: 5'-RACE and LA - PCR analyses of biopsy samples.

In order to elucidate the molecular mechanism(s) for BCL6 translocation, we identified translocational partner genes by subjecting clinical biopsy samples from patients with non-Hodgkin's lymphoma to 5'-rapid amplification of cDNA ends (5'-RACE). Sequence analysis of the 5'-RACE product revealed that the BCL6 gene was fused to the J segment of the immunoglobulin heavy chain (IgH) gene in about half of the cases, but in the other half, it was fused to heterologous partners, including the MHC class II transactivator (CIITA), pim-1, eukaryotic initiation factor 4AII (eif4AII), transferrin receptor (TFRR) and ikaros genes. Since analyses using genomic long and accurate (LA) - PCR revealed that the breakpoints in the partner gene were confined to the first intron or the second exon in all cases, the promoter and the first exon of the BCL6 gene were replaced by the promoter and the first or both the first and second exon of the partner gene. The breakpoint flanking sequences had no recombination signal sequences (RSSs) or chi sequences and were homologous with the switch region only when the BCL6 gene was fused to the IgH gene, suggesting that BCL6 translocation cannot be explained solely by mistakes of V(D)J, or chi-mediated or class-switch recombination, but rather another mechanism may also be required to explain the molecular mechanism for the promiscuous BCL6 translocation.

5' Untranslated Regions↗
PubMed1999

Mammalian Trithorax and polycomb-group homologues are antagonistic regulators of homeotic development.

Control of cell identity during development is specified in large part by the unique expression patterns of multiple homeobox-containing (Hox) genes in specific segments of an embryo. Trithorax and Polycomb-group (Trx-G and Pc-G) proteins in Drosophila maintain Hox expression or repression, respectively. Mixed lineage leukemia (MLL) is frequently involved in chromosomal translocations associated with acute leukemia and is the one established mammalian homologue of Trx. Bmi-1 was first identified as a collaborator in c-myc-induced murine lymphomagenesis and is homologous to the Drosophila Pc-G member Posterior sex combs. Here, we note the axial-skeletal transformations and altered Hox expression patterns of Mll-deficient and Bmi-1-deficient mice were normalized when both Mll and Bmi-1 were deleted, demonstrating their antagonistic role in determining segmental identity. Embryonic fibroblasts from Mll-deficient compared with Bmi-1-deficient mice demonstrate reciprocal regulation of Hox genes as well as an integrated Hoxc8-lacZ reporter construct. Reexpression of MLL was able to overcome repression, rescuing expression of Hoxc8-lacZ in Mll-deficient cells. Consistent with this, MLL and BMI-I display discrete subnuclear colocalization. Although Drosophila Pc-G and Trx-G members have been shown to maintain a previously established transcriptional pattern, we demonstrate that MLL can also dynamically regulate a target Hox gene.

Animals↗
PubMed1999

Human aiolos, an ikaros-related zinc finger DNA binding protein: cDNA cloning, tissue expression pattern, and chromosomal mapping.

The Ikaros gene (symbol ZNFN1A1) encodes the hematopoietic zinc finger DNA binding protein, which is now recognized as a central regulator of lymphoid differentiation and has been implicated in leukemogenesis. Recently, an Ikaros-related zinc finger protein, called Aiolos (ZNFN1A3), has been identified and characterized, thus establishing the presence of a gene family whose members may be hematopoietic transcription factors. Among Aiolos-mutant mice, development of B-cell lymphoma was frequently seen. As an initial approach to examining the possible involvement of Aiolos in the pathogenesis of human lymphoid proliferative disease, we isolated cDNA clones for human Aiolos from a B-cell cDNA library. The human Aiolos protein predicted from the cDNA sequence consists of 509 amino acid residues and shares 86% sequence identity with its mouse counterpart. As in the case with mouse Aiolos, no isoform for human Aiolos has been found. Northern blot analysis of various human tissues revealed that the Aiolos transcripts are expressed most strongly in peripheral blood leukocytes, the spleen, and the thymus, supporting the notion that Aiolos plays an important role in lymphoid lineages. Fluorescence in situ hybridization using a BAC clone established that the Aiolos gene is mapped to human chromosome band 17q11.2.

Amino Acid Sequence↗
PubMed1999

A novel gene, MALT1 at 18q21, is involved in t(11;18) (q21;q21) found in low-grade B-cell lymphoma of mucosa-associated lymphoid tissue.

The t(11;18) (q21;q21) translocation is a characteristic chromosomal aberration in low-grade B-cell lymphoma of mucosa-associated lymphoid tissue (MALT) type. We previously identified a YAC clone y789F3, which includes the breakpoint at 18q21 in a MALT lymphoma patient. BAC and PAC contigs were constructed on the YAC, and BAC 193f9 was found to encompass the breakpoint region. In the present study, we further narrowed down the breakpoint region at 18q21 in five MALT lymphoma patients by means of FISH and Southern blot analyses using the plasmid contig constructed from BAC 193f9. The breakpoints at 18q21 in three of the five MALT lymphoma patients were found to be clustered approximately within the 20 kb region. By using exon amplification and cDNA library screening, we identified a novel cDNA spanning the breakpoint region that exhibited aberrant mRNA signals in four of the five MALT lymphoma patients. The nucleotide sequence predicted an 813 amino acid protein that shows significant sequence similarity to the CD22beta and laminin 5 alpha3b subunit. We refer to the gene encoding this transcript as MALT1 (Mucosa-Associated Lymphoid Tissue lymphoma translocation gene 1). The alteration of MALT1 by translocation strongly suggests that this gene plays an important role in the pathogenesis of MALT lymphoma.

Amino Acid Sequence↗
PubMed1999

The kinase inhibitor fasudil (HA-1077) reduces intimal hyperplasia through inhibiting migration and enhancing cell loss of vascular smooth muscle cells.

Smooth muscle cell (SMC) migration plays an important role in restenosis after angioplasty. Myosin phosphorylation is necessary for cell migration. Fasudil is an inhibitor of protein kinases, including myosin light chain kinase and Rho associated kinase, thereby inhibiting myosin phosphorylation, and it has been clinically used to prevent vasospasm following subarachnoid hemorrage. Based on these findings, we examined the anti-migrative action of fasudil. In SMC (SM-3), fasudil (1-100 microM) inhibited SMC migration in a dose-dependent manner (p < 0.001). Fasudil suppressed actin stress fiber formation dose dependently. In rabbit carotid artery, fasudil (10 mg/kg/day) markedly reduced intimal hyperplasia 14 days following balloon injury. Cell kinetic study showed that fasudil did not affect proliferation but enhanced cell loss in the media after injury. We concluded that fasudil reduced neointimal formation after balloon injury through both inhibiting migration and enhancing cell loss of medial SMC.

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗
PubMed1999

Corin, a mosaic transmembrane serine protease encoded by a novel cDNA from human heart.

A novel cDNA has been identified from human heart that encodes an unusual mosaic serine protease, designated corin. Corin has a predicted structure of a type II transmembrane protein and contains two frizzled-like cysteine-rich motifs, seven low density lipoprotein receptor repeats, a macrophage scavenger receptor-like domain, and a trypsin-like protease domain in the extracellular region. Northern analysis showed that corin mRNA was highly expressed in the human heart. In mice, corin mRNA was detected by in situ hybridization in the cardiac myocytes of the embryonic heart as early as embryonic day (E) 9.5. By E11.5-13.5, corin mRNA was most abundant in the primary atrial septum and the trabecular ventricular compartment. Expression in the heart was maintained through the adult. In addition, mouse corin mRNA was also detected in the prehypertrophic chrondrocytes in developing bones. By fluorescent in situ hybridization analysis, the human corin gene was mapped to 4p12-13 where a congenital heart disease locus, total anomalous pulmonary venous return, had been previously localized. The unique domain structure and specific embryonic expression pattern suggest that corin may have a function in cell differentiation during development. The chromosomal localization of the human corin gene makes it an attractive candidate gene for total anomalous pulmonary venous return.

Amino Acid Sequence↗
PubMed1999

Cyclin D1/PRAD1/BCL-1 alternative transcript [B] protein product in B-lymphoid malignancies with t(11;14)(q13;q32) translocation.

The cyclin-D1/PRAD1 oncogene, a key regulator of the G1-phase progression of the cell cycle, has been identified as the long-sought BCL-1 oncogene in B-cell malignancies with t(11;14)(q13;q32) translocation. A novel alternative spliced cyclin-D1 transcript, called transcript[b], has been identified. The level of the variant transcript[b] was lower than that of the originally reported cyclin-D1 transcript, called transcript[a], in several human non-lymphoid cancer cell lines but the endogenous cellular expression of transcript[b] products has not yet been determined. Northern-blot analysis and reverse-transcription-polymerase-chain-reaction (RT-PCR) analysis revealed that transcript[b] mRNA is well expressed in B-lymphoid cell lines with t(11;14)(q13;q32) translocation and at much lower or undetectable levels in other cells. Western-blot analysis using a human cyclin-D1-specific monoclonal antibody, which can recognize and distinguish the products of transcripts [a] and [b], strongly suggested that the transcript [b] protein is indeed expressed in these B-cell lines. The present study provides identification of the endogenous cellular expression of the cyclin-D1-transcript[b] protein and strongly suggests that this alternative form of cyclin D1 may play a significant role in the molecular pathogenesis of B-lymphoid malignancies with t(11;14)(q13;q32) translocation.

Alternative Splicing↗
PubMed1999

Lewy body-type degeneration in cardiac plexus in Parkinson's and incidental Lewy body diseases.

Heart tissues of patients with PD or incidental Lewy body (LB) disease (ILBD) were examined by light and electron microscopy. LBs and alpha-synuclein-positive neurites were identified in the hearts from 9 of 11 patients with PD and from 7 of 7 patients with ILBD. LBs were present in both tyrosine hydroxylase-positive and -negative nerve processes, which are nerves of extrinsic sympathetic and intrinsic origin, respectively. These findings provide histologic evidence that the postganglionic sympathetic and intrinsic neurons in the heart are involved in the PD disease process.

Aged↗
PubMed1999

Establishment of an inducible expression system of chimeric MLL-LTG9 protein and inhibition of Hox a7, Hox b7 and Hox c9 expression by MLL-LTG9 in 32Dcl3 cells.

The MLL (HRX/ALL-1 gene is frequently disrupted in infantile leukemias and therapy-related leukemias and fused to various translocation partner genes. We previously showed that chimeric MLL proteins localize in the nuclei in a fashion similar to that of MLL protein even if the partner gene encodes a cytoplasmic protein and indicated the importance of the N-terminal portion of MLL common to various MLL translocations. This time we established an inducible expression system for chimeric MLL-LTG9 and truncated N-terminal MLL proteins (MLL-Zf(-)) in 32Dcl3 cells. By utilizing this system, we were able to show inhibition of Hox a7, Hox b7 and Hox c9 genes' expression by induced MLL-LTG9 and MLL-Zf(-). Up-regulation of Hox a7, Hox b7 and Hox c9 was observed when 32Dcl3 cells were cultured with granulocyte colony stimulating factor (G-CSF) in place of interleukin 3 and induction of MLL-LTG9 and MLL-Zf(-) was shown to suppress this upregulation. At the same time, expression of two mammalian Polycomb group genes, M33 and mel-18, which both reportedly affect Hox genes' expression, was not inhibited by MLL-LTG9 and MLL-Zf(-) induction. These results indicate that MLL has an important effect on the expression of at least some Hox genes in hematopoietic cells and suggest that inhibition of the proper expression of Hox genes by chimeric MLL proteins may dysregulate hematopoietic cell differentiation and proliferation, which then can lead to leukemogenesis.

Cell Differentiation↗
PubMed1999

Association of cyclin D1 expression with factors correlated with tumor progression in human hepatocellular carcinoma.

The amplification and/or rearrangement of the cyclin D1 gene, a positive regulatory element of the G1 to S phase of the cell cycle, has been reported in various human tumors, suggesting an oncogenic role of this gene. In this study, we investigated the expression of cyclin D1 in the formalin-fixed and paraffin-embedded human hepatocellular carcinoma (HCC) tissues of 25 patients, using monoclonal antibody 5D4 raised against cyclin D1. Two distinct patterns of staining were observed in HCC cells, nuclear and cytoplasmic. The nuclear staining pattern of cyclin D1 was detected in the tissues of only 2 of the 25 HCC patients (8%) examined and no particular clinicopathological characteristics were found in these patients. In contrast, the cytoplasmic staining pattern, without nuclear staining, was detected in 8 of the 25 patients with HCC (32%). A significant correlation was found between the expression of cytoplasmic cyclin D1 and patients with tumor thrombus in the portal vein (Vp), as well as those with intrahepatic metastasis (IM). These results indicate that the cytoplasmic cyclin D1 expression appears to be related to the prognosis of HCC. The Ag nucleolar organizer regions (NORs) counts in cyclin D1-positive and -negative patients were not significantly different, suggesting that immunostaining for cyclin D1 has the potential to be a unique prognostic marker in human HCC. Simultaneous immunohistochemical study with p53 antibody in the same series of HCC revealed that 88% of the patients positive for cyclin D1 also expressed p53 and that in 91% of the patients negative for p53, cyclin D1 was not expressed. These results suggest that cyclin D1 is expressed later than the alteration of p53 in the progression of human HCC.

Adult↗
PubMed1999

Chromosomal imbalances in adult T-cell leukemia revealed by comparative genomic hybridization: gains at 14q32 and 2p16-22 in cell lines.

Comparative genomic hybridization was used to identify chromosomal imbalances in eight cell lines and 12 blood samples from patients with adult T-cell leukemia/lymphoma (ATL). The chromosomes most often over-represented in the cell lines were 2p (6 cases), 7q (4 cases), and 14q (4 cases), with minimal common regions at 2p16-22, 7q21-36, and 14q32, respectively. Distinct imbalances were detected in only 7 of the clinical samples. Chromosomes 14q32 and 2p16-22 harbor TCL1 and a transcription factor, HTLF (human T-cell leukemia virus enhancer factor), respectively. FISH analysis revealed that TCL1 did not juxtapose to TCRA, and we detected no expression of TCL1 in any of the ATL cell lines despite the 14q32 amplifications. Moreover, expression of HTLF was not elevated in the ATL cell lines bearing multiplication of 2p. These results suggest that chromosomal regions 2p16-22 and 14q32 harbor genes other than HTLF and TCL1 that are involved in cellular immortalization or in the pathogenesis of ATL.

Chromosome Aberrations↗
PubMed1999

Rho-kinase-mediated pathway induces enhanced myosin light chain phosphorylations in a swine model of coronary artery spasm.

OBJECTIVE: We recently demonstrated in our swine model of coronary artery spasm that enhanced myosin light chain (MLC) phosphorylations (both MLC mono- and diphosphorylations) play a central role in the pathogenesis of the spasm. However, the molecular mechanism for and the phosphorylation sites for the enhanced MLC phosphorylations were unknown. In the present study, we addressed these points using hydroxyfasudil, a novel inhibitor of protein kinases, which we found preferentially inhibits Rho-kinase. METHODS: The specificity of the inhibitory effects of hydroxyfasudil on Rho-kinase, MLCK, MRCK beta and PKC were examined by kinase assay in vitro. The left porcine coronary artery was chronically treated with interleukin-1 beta (IL-1 beta, 2.5 micrograms). Two weeks after the operation, coronary artery vasomotion was examined both in vivo and in vitro. MLC phosphorylations were examined by Western blot analysis and the sites for the phosphorylations by anti-phosphorylated MLC antibodies that identified the monophosphorylation site as Ser19 and diphophorylation sites as Ser19/Thr18 of MLC. RESULTS: Inhibitory effects of hydroxyfasudil was at least 100 times more potent for Rho-kinase as compared with other protein kinases tested. Intracoronary serotonin (10 micrograms/kg) caused coronary hyperconstriction at the IL-1 beta-treated site in vivo, which was dose-dependently inhibited by hydroxyfasudil (p < 0.01). The coronary segment taken from the spastic site also showed hypercontractions to serotonin in vitro, which were again dose-dependently inhibited by hydroxyfasudil (p < 0.01). Western blot analysis showed that MLC monophosphorylation was significantly greater in the spastic segment than in the control segment, while MLC diphosphorylation was noted only at the spastic segment (p < 0.01). The sites for the mono- and diphosphorylated MLC were identified as the monophosphorylated site Ser19 and diphosphorylated sites Ser19/Thr18 of MLC, respectively. Both types of MLC phosphorylations at the spastic segment were markedly inhibited by hydroxyfasudil (p < 0.01). CONCLUSION: These results indicate that hydroxyfasudil-sensitive Rho-kinase-mediated pathway appears to mediate the enhanced MLC phosphorylations (on Ser19 and Ser19/Thr18 residues) and plays a central role in the pathogenesis of coronary artery spasm.

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗
PubMed1999

Chromosome abnormalities and MLL rearrangements in acute myeloid leukemia of infants.

Of 29 infants with acute myeloid leukemia (AML), 14 (48%) had various 11q23 translocations. MLL rearrangements were examined in 21 of the 29 patients, and 11 (52%) showed the rearrangements. 11q23 translocations and/or MLL rearrangements were found in 17 (58%) of the 29 patients. While all but one of the 17 patients with 11q23/MLL rearrangements had M4 or M5 type of the FAB classification, the 12 patients without such rearrangements had various FAB types, including M2, M4, M4EO, M6 and M7. Of the 12 patients with other chromosome abnormalities or normal karyotypes, two had inv(16) ort(16;16), one had t(1;22)(p13;q13), and two had a novel translocation, t(7;12)(q32;p13). The breakpoint on 12p of the t(7;12) was assigned to intron 1 or the region just upstream of exon 1 of the TEL/ETV6 gene by fluorescence in situ hybridization. The event-free survival at 5 years for the 17 patients with 11q23/MLL rearrangements was 42.2%, and that for the 12 patients without such rearrangements was 31.3% (P = 0.5544). 11q231MLL rearrangements have been frequently reported and a poor prognosis in infant acute lymphoblastic leukemia implied. Our study showed that while 11q23/MLL rearrangements were also common in infant AML, AML infants with such rearrangements had a clinical outcome similar to that of AML infants without such rearrangements.

Acute Disease↗