PubMed Health⌕ Search

Biomedical subjects

Y Kadokawa

Publications and source records attributed to Y Kadokawa.

12 recordsLinked to original sources
PubMed1999

Mutation in ankyrin repeats of the mouse Notch2 gene induces early embryonic lethality.

Notch family genes encode transmembrane proteins involved in cell-fate determination. Using gene targeting procedures, we disrupted the mouse Notch2 gene by replacing all but one of the ankyrin repeat sequences in the cytoplasmic domain with the E. coli (beta)-galactosidase gene. The mutant Notch2 gene encodes a 380 kDa Notch2-(beta)-gal fusion protein with (beta)-galactosidase activity. Notch2 homozygous mutant mice die prior to embryonic day 11.5, whereas heterozygotes show no apparent abnormalities and are fully viable. Analysis of Notch2 expression patterns, revealed by X-gal staining, demonstrated that the Notch2 gene is expressed in a wide variety of tissues including neuroepithelia, somites, optic vesicles, otic vesicles, and branchial arches, but not heart. Histological studies, including in situ nick end labeling procedures, showed earlier onset and higher incidence of apoptosis in homozygous mutant mice than in heterozygotes or wild type mice. Dying cells were particularly evident in neural tissues, where they were seen as early as embryonic day 9.5 in Notch2-deficient mice. Cells from Notch2 mutant mice attach and grow normally in culture, demonstrating that Notch2 deficiency does not interfere with cell proliferation and that expression of the Notch2-(beta)-gal fusion protein is not toxic per se. In contrast to Notch1-deficient mice, Notch2 mutant mice did not show disorganized somitogenesis, nor did they fail to properly regulate the expression of neurogenic genes such as Hes-5 or Mash1. In situ hybridization studies show no indication of altered Notch1 expression patterns in Notch2 mutant mice. The results indicate that Notch2 plays an essential role in postimplantation development in mice, probably in some aspect of cell specification and/or differentiation, and that the ankyrin repeats are indispensable for its function.

Animals↗
PubMed1999

Notch2 expression negatively correlates with glial differentiation in the postnatal mouse brain.

Notch family molecules are thought to be negative regulators of neuronal differentiation in early brain development. After expression in the embryonic period, Notch2 continues to be expressed postnatally in the specific regions in the rodent brain. Here, we examined Notch2 expression in the postnatal mouse brain using lacZ knockin animals at the Notch2 locus. Notch2 expression was observed in the developing cerebellum and hippocampus, characteristic regions where neurogenesis persists after birth. Double staining of sections revealed that Notch2 was expressed by Bergmann glia in the cerebellum, radial glia in the hippocampus, and some astrocytes in both regions. Notch2 expression by glial cells was clearly confirmed in dissociated cell cultures. Interestingly, neocortical glia, many of which did not express Notch2 in vivo, did express Notch2 in a dissociated culture condition. The triple staining of dissociated cell cultures revealed that stronger Notch2 expression correlated with the immature type of glial gene expressions: stronger vimentin and weaker glial fibrillary acidic protein expressions. In addition, Notch2 expression correlated with the incorporation of bromodeoxyuridine both in vivo and in vitro. Thus, these findings demonstrate that Notch2 is expressed not only by neuronal cells in the embryonic brain, but also by glial cells in the postnatal brain, and that its expression negatively correlates with glial differentiation, proposing its novel function as a negative regulator of glial differentiation in mammalian brain development.

Aging↗
PubMed1996

Essential and non-redundant roles of p48 (ISGF3 gamma) and IRF-1 in both type I and type II interferon responses, as revealed by gene targeting studies.

BACKGROUND: Interferons (IFNs) are a class of cytokines which confer cellular resistance against viral infections. Type I (IFN-alpha and -beta) and type II (IFN-gamma) IFNs utilize distinct receptors, the stimulation of which results in the induction of downstream target genes. These target genes usually contain within their promoter region an IFN responsive element, termed ISRE (IFN stimulated response element) which binds a heterotrimeric transcription factor, ISGF3 (IFN-stimulated gene factor 3) consisting of p48 (ISGF3 gamma), Stat1 (Signal transducers and activators of transcription-1; alpha or beta), and Stat2. The ISRE sequence overlaps with that of IRF-E which binds another IFN-inducible factor, IRF-1 (IFN regulatory factor-1). RESULTS: We generated mice lacking p48 by gene targeting. We show that p48 plays an essential role in both type I and type II IFN responses; activation of IFN-inducible genes and establishment of the antiviral state by IFN-alpha or -gamma are both severely impaired, and ISRE-binding activities induced by both IFNs are absent in the p48-negative embryonic fibroblasts (EFs). Furthermore, we generated mice deficient for both p48 and IRF-1 and found that at least one IFN-inducible gene is dependent on both factors. CONCLUSIONS: p48 and IRF-1 do not perform redundant functions in the cell, but rather complement one another in both type I and II IFN responses.

Animals↗
PubMed1996

Regulation of IFN-alpha/beta genes: evidence for a dual function of the transcription factor complex ISGF3 in the production and action of IFN-alpha/beta.

BACKGROUND: Efficient production of interferons (IFNs) in virally infected cells is an essential aspect of the host defence. The transcription factor complex ISGF3 (IFN-stimulated gene factor 3) was originally identified as a critical mediator of the IFN signal; it is formed upon IFN receptor (IFNR) stimulation and binds to ISREs (IFN-stimulated response elements) to activate IFN-inducible genes. It has recently been shown that the DNA binding component of ISGF3, p48 (ISGF3gamma) also binds to virus-inducible elements in the IFN-alpha/beta genes, suggesting a potential new role of p48 in IFN production. RESULTS: Primary cells from mice with a targeted disruption of the p48 gene show severe defects in virus-induced IFN-alpha/beta gene expression. A similar defect was also observed in cells lacking type I IFNR or Stat1, further demonstrating the role of IFN signalling in the induction of these IFN genes. ISGF3 in fact binds to the virus-inducible elements within the IFN-alpha/beta promoters. We also provide evidence showing that these elements are additionally controlled by an unidentified factor(s) which presumably triggers the primary phase of IFN gene induction. CONCLUSIONS: Our results demonstrate that the IFN signal transducing complex ISGF3 plays a crucial role in IFN production and suggest that ISGF3 may participate directly in the activation of IFN-alpha/beta promoters. This dual function of ISGF3 may insure the efficient operation of this cytokine system in the host defence.

Animals↗
PubMed1995

A murine Thy-1.2 reporter vector containing a SV40 origin for rapid cloning and analysis of eukaryotic promoters.

A new vector, pATO, was constructed for rapid cloning and analysis of eukaryotic promoters. When a recombinant pATO, carrying a promoter sequence in its multiple cloning site, was introduced into COS cells, Thy-1.2 protein was produced on the cell surface, and was easily identified by an fluorescein-conjugated anti-Thy-1.2 antibody. The intensity of the fluorescence reflected the strength of the inserted promoter. Since pATO could replicate efficiently in COS cells, the recombinant plasmids recovered from a single COS cell were sufficient to transform Escherichia coli cells. This plasmid is applicable for the rapid and labor saving cloning of promoter elements.

Animals↗
PubMed1995

Effects of an upstream DNA curvature on the strength of HSV thymidine kinase promoter.

The effect of an upstream DNA curvature on the strength of the herpes simplex virus thymidine kinase (TK) promoter was investigated by employing luciferase assay. A set of double-stranded oligonucleotides, each with an unique DNA configuration, were synthesized and substituted into an upstream region of the promoter. It was revealed from the assay that both plane and space curves exerted a negative influence upon the strength of the promoter.

Base Sequence↗
PubMed1990

Cell lineage analyses of epithelia and blood vessels in chimeric mouse embryos by use of an embryonic stem cell line expressing the beta-galactosidase gene.

We have established an embryonic stem (ES) cell line, MS1-EL4, which has the potential to make various tissues in chimeric embryos and, at the same time, expresses the beta-galactosidase gene which was introduced as a good cell marker. To examine cell behavior and lineage during embryogenesis, we injected MS1-EL4 cells into host blastocysts and recovered chimeric embryos at various developmental stages. We examined the distribution of the MS1-EL4 cell derivatives by staining whole embryos with X-gal and by making serial paraffin sections. So far we have obtained the following results: (1) the MS1-EL4 cell line is useful for studying cell lineages because of its ubiquitous expression at least until the mid-gestation stage; (2) cells of the primitive ectoderm and its derivative epithelial tissues continue to intermingle with each other until the late primitive streak stage. Then, at early somite stages, cells of various epithelia stop intermingling and give rise to small coherent clones; (3) blood vessels of the yolk sac are formed by local aggregation of the ancestor cells and those of the embryo proper by proliferation and sprouting from fewer angiogenic cells.

Animals↗
PubMed1987

Cell lineage analysis of the primitive and visceral endoderm of mouse embryos cultured in vitro.

Cell lineages of the primitive endoderm and the visceral endoderm of mouse embryos were examined by culturing whole embryos in vitro. The primitive endoderm and visceral endoderm cells could be labelled by incubation of embryos in a medium containing horse radish peroxidase (HRP). HRP localization was chased throughout the culture period. The results show that the visceral endoderm derives from the primitive endoderm, and the visceral endoderm forms only the extra-embryonic endoderm (yolk sac endoderm) of the conceptus. The definitive endoderm which is probably derived from the head process, newly appears on the ventral surface of the embryo.

Animals↗
PubMed1986

Studies on the mechanism of blastula formation in starfish embryos denuded of fertilization membrane.

A starfish egg, denuded of the fertilization membrane and placed on a glass surface, becomes a cell monolayer after several cleavages. This sheet of cells folds and forms a hollow sphere resembling a normal blastula at the 2(9)-2(10)-cell stage ('closing movement'). A marked morphological change was observed in each cell, preceding the closing movement. The surface of each blastomere differentiated into two parts: one was smooth, whereas the other was rough with microvilli. The smooth surface was more adhesive and flexible than the rough surface, suggesting that the closing movement may be driven by a local increase in cell adhesiveness.

Animals↗