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Naoki Takeda

Publications and source records attributed to Naoki Takeda.

28 records · Page 2Linked to original sources
PubMed2003

Increase of TCR V beta accessibility within E beta regulatory region influences its recombination frequency but not allelic exclusion.

Seventy percent of the murine TCRbeta locus (475 kb) was deleted to generate a large deleted TCRbeta (beta(LD)) allele to investigate a possible linkage between germline transcription, recombination frequency, and allelic exclusion of the TCR Vbeta genes. In these beta(LD/LD) mice, the TCRbeta gene locus contained only four Vbeta genes at the 5' side of the locus, and consequently, the Vbeta10 gene was located in the original Dbeta1-Jbeta1cluster within the Ebeta regulatory region. We showed that the frequency of recombination and expression of the Vbeta genes are strongly biased to Vbeta10 in these mutant mice even though the proximity of the other three 5'Vbeta genes was also greatly shortened toward the Dbeta-Jbeta cluster and the Ebeta enhancer. Accordingly, the germline transcription of the Vbeta10 gene in beta(LD/LD) mice was exceptionally enhanced in immature double negative thymocytes compared with that in wild-type mice. During double negative-to-double positive transition of thymocytes, the level of Vbeta10 germline transcription was prominently increased in beta(LD/LD) recombination activating gene 2-deficient mice receiving anti-CD3epsilon Ab in vivo. Interestingly, however, despite the increased accessibility of the Vbeta10 gene in terms of transcription, allelic exclusion of this Vbeta gene was strictly maintained in beta(LD/LD) mice. These results provide strong evidence that increase of Vbeta accessibility influences frequency but not allelic exclusion of the TCR Vbeta rearrangement if the Vbeta gene is located in the Ebeta regulatory region.

Alleles↗
PubMed2003

Bcl11b is required for differentiation and survival of alphabeta T lymphocytes.

The gene Bcl11b, which encodes zinc finger proteins, and its paralog, Bcl11a, are associated with immune-system malignancies. We have generated Bcl11b-deficient mice that show a block at the CD4-CD8- double-negative stage of thymocyte development without any impairment in cells of B- or gammadelta T cell lineages. The Bcl11b-/- thymocytes showed unsuccessful recombination of V(beta) to D(beta) and lacked the pre-T cell receptor (TCR) complex on the cell surface, owing to the absence of Tcrb mRNA expression. In addition, we saw profound apoptosis in the thymus of neonatal Bcl11b-/- mice. These results suggest that Bcl11b is a key regulator of both differentiation and survival during thymocyte development.

Animals↗
PubMed2003

Expression of Tom34 splicing isoforms in mouse testis and knockout of Tom34 in mice.

The 34-kDa translocase of the outer mitochondrial membrane (Tom34) is a putative mammalian-specific factor involved in protein import into mitochondria. We analyzed the genomic sequence of the mouse Tom34 gene and found it has two alternative initial exons. Using reverse transcription and the polymerase chain reaction (RT-PCR), we found that these two mRNAs differs only in the 5'-proximal sequences corresponding to the two initial exons (exon 1a and 1b). Tom34 mRNA with exon 1a (Tom34a) is expressed ubiquitously, while that with exon 1b (Tom34b) is expressed only in mature testicular germ cells. To explore the in vivo function of Tom34 proteins, we generated Tom34-deficient mice by targeted disruption. The Tom34(-/-) mice were viable and grew normally and had a normal Mendelian inheritance pattern. Male as well as female Tom34(-/-) mice were fertile. In vitro-preprotein import into isolated mitochondria showed no apparent difference between Tom34(-/-) and wild-type mice. These results indicate that Tom34 is dispensable for mouse growth and development under optimal conditions.

Alternative Splicing↗
PubMed2002

G9a histone methyltransferase plays a dominant role in euchromatic histone H3 lysine 9 methylation and is essential for early embryogenesis.

Covalent modification of histone tails is crucial for transcriptional regulation, mitotic chromosomal condensation, and heterochromatin formation. Histone H3 lysine 9 (H3-K9) methylation catalyzed by the Suv39h family proteins is essential for establishing the architecture of pericentric heterochromatin. We recently identified a mammalian histone methyltransferase (HMTase), G9a, which has strong HMTase activity towards H3-K9 in vitro. To investigate the in vivo functions of G9a, we generated G9a-deficient mice and embryonic stem (ES) cells. We found that H3-K9 methylation was drastically decreased in G9a-deficient embryos, which displayed severe growth retardation and early lethality. G9a-deficient ES cells also exhibited reduced H3-K9 methylation compared to wild-type cells, indicating that G9a is a dominant H3-K9 HMTase in vivo. Importantly, the loss of G9a abolished methylated H3-K9 mostly in euchromatic regions. Finally, G9a exerted a transcriptionally suppressive function that depended on its HMTase activity. Our results indicate that euchromatic H3-K9 methylation regulated by G9a is essential for early embryogenesis and is involved in the transcriptional repression of developmental genes.

Acetylation↗
PubMed2002

Otx2 is required to respond to signals from anterior neural ridge for forebrain specification.

Previous analysis employing chimeric and transgenic rescue experiments has suggested that Otx2 is required in the neuroectoderm for development of the forebrain region. In order to elucidate the precise role of Otx2 in forebrain development, we attempted to generate an allelic series of Otx2 mutations by Flp- and Cre-mediated recombination for the production of conditional knock-out mice. Unexpectedly, the neo-cassette insertion created a hypomorphic Otx2 allele; consequently, the phenotype of compound mutant embryos carrying both a hypomorphic and a null allele (Otx2(frt-neo/-)) was analyzed. Otx2(frt-neo/-) mutant mice died at birth, displaying rostral head malformations. Molecular marker analysis demonstrated that Otx2(frt-neo/-) mutant embryos appeared to undergo anterior-posterior axis generation and induction of anterior neuroectoderm normally; however, these mutants subsequently failed to correctly specify the forebrain region. As the rostral margin of the neural plate, termed the anterior neural ridge (ANR), plays crucial roles with respect to neural plate specification, we examined expression of molecular markers for the ANR and the neural plate; moreover, neural plate explant studies were performed. Analyses revealed that telencephalic gene expression did not occur in mutant embryos due to defects of the neural plate; however, the mutant ANR bore normal induction activity on gene expression. These results further suggest that Otx2 dosage may be crucial in the neural plate with respect to response to inductive signals primarily from the ANR for forebrain specification.

Alleles↗
PubMed2002

Targeted disruption of the Tab1 gene causes embryonic lethality and defects in cardiovascular and lung morphogenesis.

The transforming growth factor-beta (TGF-beta) superfamily consists of a group of secreted signaling molecules that perform important roles in the regulation of cell growth and differentiation. TGF-beta activated kinase-1 binding protein-1 (TAB1) was identified as a molecule that activates TGF-beta activated kinase-1 (TAK1). Recent studies have revealed that the TAB1-TAK1 interaction plays an important role in signal transduction in vitro, but little is known about the role of these molecules in vivo. To investigate the role of TAB1 during development, we cloned the murine Tab1 gene and disrupted it by homologous recombination. Homozygous Tab1 mutant mice died, exhibiting a bloated appearance with extensive edema and hemorrhage at the late stages of gestation. By histological examinations, it was revealed that mutant embryos exhibited cardiovascular and lung dysmorphogenesis. Tab1 mutant embryonic fibroblast cells displayed drastically reduced TAK1 kinase activities and decreased sensitivity to TGF-beta stimulation. These results indicate a possibility that TAB1 plays an important role in mammalian embryogenesis and is required for TAK1 activation in TGF-beta signaling.

Adaptor Proteins, Signal Transducing↗
PubMed2002

Multivariate analysis of histopathologic prognostic factors for invasive cervical cancer treated with radical hysterectomy and systematic retroperitoneal lymphadenectomy.

BACKGROUND: The aim of this study was to identify the independent histopathologic prognostic factors for patients with cervical carcinoma treated with radical hysterectomy including paraaortic lymphadenectomy. METHODS: A total of 187 patients with stage IB to IIB cervical carcinomas treated with radical hysterectomy and systematic retroperitoneal lymphadenectomy were retrospectively analyzed. The median follow-up period was 83 months. Cox regression analysis was used to select independent prognostic factors. RESULTS: Using multivariate Cox regression analysis, lymph node (LN) status (negative vs. metastasis to pelvic nodes except for common iliac nodes vs. common iliac/paraaortic node metastasis), histopathologic parametrial invasion, lymph-vascular space invasion (LVSI), and histology of pure adenocarcinoma were found to be independently related to patients' poor survival. For patients who had a tumor histologically confined to the uterus and have neither parametrial invasion nor lymph node metastasis, LVSI was the most important prognostic factor, and histologic type, depth of cervical stromal invasion, and tumor size were not related to survival. The survival of patients with a tumor extending to parametrium or pelvic lymph node(s) was adversely affected by histology of pure adenocarcinoma. When the tumor extended to common iliac or paraaortic nodes, patients' survival became quite poor irrespective of LVSI or histologic type of pure adenocarcinoma. Patients' prognosis could be stratified into low risk (patients with a tumor confined to the uterus not associated with LVSI: n = 80), intermediate risk (patients with a tumor confined to the uterus associated with positive LVSI, and patients with squamous/adenosquamous carcinoma associated with pelvic lymph node metastasis or parametrial invasion: n = 86), and high risk (patients with pure adenocarcinoma associated with pelvic lymph node metastasis or parametrial invasion, and patients with common iliac/paraaortic node metastasis: n = 21) with an estimated 5-year survival rate of 100 +/- 0 (mean +/- SE)%, 85.5 +/- 3.9%, and 25.1 +/- 9.7%, respectively. CONCLUSIONS: LN status, parametrial invasion, LVSI, and histology of pure adenocarcinoma are important histopathologic prognostic factors of cervical carcinoma treated with radical hysterectomy and systematic retroperitoneal lymphadenectomy. Prognosis for patients with cervical carcinoma may be stratified by combined analysis of these histopathologic prognostic factors. Postoperative therapy needs to be individualized according to these prognostic factors and validated for its efficacy using randomized clinical trials.

Adenocarcinoma↗
PubMed2002

A testicular germ cell-associated serine-threonine kinase, MAK, is dispensable for sperm formation.

A member of the mitogen-activated protein kinase superfamily, MAK, has been proposed to have an important role in spermatogenesis, since Mak gene expression is highly restricted to testicular germ cells. To assess the biological function of MAK, we have established MAK-deficient (Mak(-/-)) mice. Mak(-/-) mice developed normally, and no gross abnormalities were observed. Spermatogenesis of the Mak(-/-) mice was also intact, and most of the mice were fertile. However, Mak(-/-) male-derived litter sizes and their sperm motility in vitro were mildly reduced. These data show that function of MAK is not essential for spermatogenesis and male fertility.

Animals↗
PubMed2002

Genetic modifiers of otocephalic phenotypes in Otx2 heterozygous mutant mice.

Mice heterozygous for the Otx2 mutation display a craniofacial malformation, known as otocephaly or agnathia-holoprosencephaly complex. The severity of the phenotype is dependent on the genetic background of a C57BL/6 (B6) strain; most of the offspring of Otx2 knock-out chimeras, which are equivalent to the F(1) of CBA and B6 strains, backcrossed with B6 females display reduction or loss of mandible, whereas those backcrossed with CBA females do not show noticeable phenotype at birth. The availability of phenotypically disparate strains renders identification of Otx2 modifier loci possible. In this study, a backcross of chimera with B6 was generated and genome-wide scans were conducted with polymorphic markers for non-mendelian distribution of alleles in Otx2 heterozygous mutant mice displaying abnormalities in the lower jaw. We identified one significant locus, Otmf18, between D18Mit68 and D18Mit120 on chromosomes 18, linked to the mandibular phenotype (LOD score 3.33). A similar replication experiment using a second backcross (N3) mouse demonstrated the presence of another significant locus, Otmf2 between D2Mit164 and D2Mit282 on chromosome 2, linked to the mandibular phenotype (LOD score 3.93). These two modifiers account for the distribution of the craniofacial malformations by the genetic effect between B6 and CBA strains. Moreover, Otmf2 contain a candidate gene for several diseases in mice and humans. These genetic studies involving an otocephalic mouse model appear to provide new insights into mechanistic pathways of craniofacial development. Furthermore, these experiments offer a powerful approach with respect to identification and characterization of candidate genes that may contribute to human agnathia-holoprosencephaly complex diseases.

Animals↗