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Y Wakamatsu

Publications and source records attributed to Y Wakamatsu.

At least 19 recordsLinked to original sources
PubMed2000

The conditional medaka mutation eyeless uncouples patterning and morphogenesis of the eye.

In early vertebrate eye development, the retinal anlage is specified in the anterior neuroectoderm. During neurulation, the optic vesicles evaginate from the lateral wall of the prosencephalon. Here we describe the temperature-sensitive mutation eyeless in the Japanese medakafish. Marker gene analysis indicates that, whereas, specification of two retinal primordia and proximodistal patterning takes place in the mutant embryo, optic vesicle evagination does not occur and subsequent differentiation of the retinal primordia is not observed. The mutation eyeless thus uncouples patterning and morphogenesis at early steps of retinal development. Temperature-shift experiments indicate a requirement for eyeless activity prior to optic vesicle evagination. Cell transplantation shows that eyeless acts cell autonomously.

Animals↗
PubMed1999

Mannosylerythritol lipid is a potent inducer of apoptosis and differentiation of mouse melanoma cells in culture.

Malignant melanomas are tumors that are well known to respond poorly to treatment with chemotherapeutic reagents. We report here that mannosylerythritol lipid (MEL), an extracellular glycolipid from yeast, markedly inhibited the growth of mouse melanoma B16 cells in a dose-dependent manner. Exposure of B16 cells to MEL at 10 microM and higher concentrations caused the condensation of chromatin, DNA fragmentation, and sub-G1 arrest, all of which are hallmarks of cells that are undergoing apoptosis. Analysis of the cell cycle also suggested that both the MEL-mediated inhibition of growth and apoptosis were closely associated with growth arrest in the G1 phase. Moreover, MEL exposure stimulated the expression of differentiation markers of melanoma cells, such as tyrosinase activity and the enhanced production of melanin, which is an indication that MEL triggered both apoptotic and cell differentiation programs. Forced expression of Bcl-2 protein in stably transformed B16 cells had a dual effect: it interfered with MEL-induced apoptosis but increased both tyrosinase activity and the production of melanin as compared with these phenomena in vector-transfected MEL-treated control B16 cells. These results provide the first evidence that growth arrest, apoptosis, and the differentiation of mouse malignant melanoma cells can be induced by a microbial extracellular glycolipid.

Animals↗
PubMed1999

NUMB localizes in the basal cortex of mitotic avian neuroepithelial cells and modulates neuronal differentiation by binding to NOTCH-1.

The importance of lateral inhibition mediated by NOTCH signaling is well demonstrated to control neurogenesis both in invertebrates and vertebrates. We have identified the chicken homolog of Drosophila numb, which suppresses NOTCH signaling. We show that chicken NUMB (c-NUMB) protein is localized to the basal cortex of mitotic neuroepithelial cells, suggesting that c-NUMB regulates neurogenesis by the modification of NOTCH signaling through asymmetrical cell division. Consistent with this suggestion, we show (1) that c-NUMB interferes with the nuclear translocation of activated c-NOTCH-1 through direct binding to the PEST sequence in the cytoplasmic domain of c-NOTCH-1 and (2) that c-NUMB interferes with c-NOTCH-1-mediated inhibition of neuronal differentiation.

Amino Acid Sequence↗
PubMed1999

Transplantation of blastula nuclei to non-enucleated eggs in the medaka, Oryzias latipes.

Studies of nuclear transplantation were conducted to establish methods for the production of clones of fish, using a small laboratory fish, medaka, Oryzias latipes. As the first step of the study, single-blastula nuclei of an inbred strain with the wild-type body color were transplanted into non-enucleated unfertilized eggs of an outbred orange red strain. Of 845 operated eggs, 45 hatched into fry exhibiting the wild-type body color, one of the donor markers. Twenty-seven of these nuclear transplants grew to the adult stage and clearly exhibited external secondary sexual characteristics. Fourteen were females and 13 were males. The allozyme analysis of phosphoglucomutase, measurements of relative DNA content by microfluorometry and chromosome counts consistently indicated that the nuclear transplants were triploids that originated from both the diploid donor nuclei and the haploid recipient pronuclei. In the crossing experiments between the nuclear transplants and the orange-red strain, most of the male nuclear transplants were sterile, whereas one male produced a viable offspring with wild-type body color. All of the female nuclear transplants were sterile. Macroscopic observations of their gonads showed that the testes appeared normal and the ovaries appeared degenerated. These features of the reproductive potential and the morphology of gonads also indicated that the nuclear transplants were triploids. These results demonstrated that a basic technique for nuclear transplantation in medaka was established.

Animals↗
PubMed1999

Expression of murine early embryonic antigens, SSEA-1 and antigenic determinant of EMA-1, in embryos and ovarian follicles of a teleost medaka (Oryzias latipes).

Stage-specific embryonic antigen-1 (SSEA-1) and the antigenic determinant of monoclonal antibody EMA-1 are expressed in a stage-specific manner in mouse early embryos. To study whether these antigens generally exist in fish, expression of the antigens was examined in embryos, ovarian follicles, and adult tissues of a teleost medaka (Oryzias latipes), using immunohistochemical techniques. In 1-cell-stage embryos, these carbohydrate antigens were found in numerous cytoplasmic granules in the blastodisc and the cortical cytoplasm. These granules gradually decreased in number as the embryos developed. In 4-cell-stage embryos, the antigens appeared on the cleavage planes and were located on the cleavage planes within the blastoderm in the following cleavage stages. In blastula-stage embryos, the expression was ubiquitously found on the cell surface of blastomeres. At the mid-gastrula stage, the antigens were restricted to the enveloping layer, yolk syncytial layer, and cortical cytoplasm, but were rarely found in deep cells that contribute to formation of the embryonic body. In later-stage embryos and adult fish, the antigens were located in various tissues. In ovarian follicles, the antigens were found in granules of oocytes and granulosa cells. These observations were basically consistent with those in mice; however, expression in 1-cell-stage embryos and ovarian follicles has not been observed in mice. This unexpected finding suggests that the antigens are produced in granulosa cells and transferred to 1-cell-stage embryos via oocytes, and that the antigens involved in the early developmental process are maternally prepared in teleosts.

Animals↗
PubMed1999

Oculocutaneous albinism in the i6 mutant of the medaka fish is associated with a deletion in the tyrosinase gene.

Three mutant alleles (i1, i4, and i5) of the tyrosinase gene in the i locus of the medaka fish Oryzias latipes have hitherto been described, all being associated with transposable element insertion. We have recently identified another allele causing a complete albino phenotype in homozygous carriers and named it i6. Sequence comparison between the tyrosinase gene for the i6 allele (Tyr-i6) and the wild-type gene previously obtained (Tyr-i+) revealed three deletions of 8, 44, and 245 bp. The first two deletions reside in an intron and are differences in the number of tandem tetranucleotide repeats that are polymorphic even among wild-type genes, and, thus, not likely to be responsible for the i6 albino phenotype. The largest deletion spans over the last 180 bp of the second intron and the first 65 bp of the third exon. Because of this deletion, the Tyr-i6 gene lacks the branch point sequence and the acceptor site for the second intron, both being considered to be necessary for normal RNA splicing. Therefore, the 245-bp deletion is likely to be responsible for the albino phenotype. With a mutant gene of this type, unlike ones bearing transposable element insertions, the possibility of reversion mutations to the wild-type would be negligible. Therefore, fish having the i6/i6 genotype should serve as superior recipients for the tyrosinase gene in rescue experiments.

Albinism, Oculocutaneous↗
PubMed1999

[Stereometry of temporal peripapillary atrophy in early-stage open-angle glaucoma].

PURPOSE: To study the significance of temporal peripapillary atrophy in the pathogenesis of open-angle glaucoma in its early stage. CASES AND METHOD: Sterometry of temporal peripapillary atrophy was performed in 46 eyes of 46 patients with early-stage open-angle glaucoma and in 38 eyes of 38 healthy persons using a Heidelberg Retina Tomograph. RESULTS: The area of peripapillary atrophy averaged 0.78 +/- 0.46 mm2 in glaucoma eyes and 0.55 +/- 0.33 mm2 in controls. The difference was significant (p < 0.002). Its volume averaged 0.04 +/- 0.04 mm3 in glaucoma eyes and 0.02 +/- 0.02 mm3 in controls. The difference was significant (p < 0.001). Both the area and volume of disc cupping were significantly greater in glaucoma eyes than in controls (p < 0.001). The volume of rim of the disc was significantly smaller in eyes with symmetrical cupping than asymmetrical one (p < 0.001). Both the area and volume of peripapillary atrophy were significantly greater in eyes with asymmetrical cupping than symmetrical one (p < 0.001 each). CONCLUSION: The presence, shape and size of temporal peripapillary atrophy are closely associated with the pathogenesis of open-angle glaucoma in its early stage.

Adult↗
PubMed1998

Avian neural crest-derived neurogenic precursors undergo apoptosis on the lateral migration pathway.

Neural crest cells of vertebrate embryos disperse on distinct pathways and produce different derivatives in specific embryonic locations. In the trunk of avian embryos, crest-derived cells that initially migrate on the lateral pathway, between epidermal ectoderm and somite, produce melanocytes but no neuronal derivatives. Although we found that melanocyte precursors are specified before they disperse on the lateral pathway, we also observed that a few crest-derived neuronal cells are briefly present on the same pathway. Here, we show that neuronal cells are removed by an episode of apoptosis. These observations suggest that localized environmental factor(s) affect the distribution of fate-restricted crest derivatives and function as a 'proof-reading mechanism' to remove 'ectopic' crest-derived cells.

Animals↗
PubMed1998

Usefulness of the medaka beta-actin promoter investigated using a mutant GFP reporter gene in transgenic medaka (Oryzias latipes).

The activity of the medaka beta-actin promoter as a ubiquitous expression vector in transgenic medaka was examined using complementary DNA of the green fluorescent protein (GFP). Plasmid pOBA-GFP contained both the medaka beta-actin promoter and cDNA of the wild-type GFP, while pOBA-hGFP contained the medaka beta-actin promoter and cDNA of the mutant GFP in which serine was substituted for threonine at position 65 and codon usage was humanized to promote translation in vertebrate cells. The ApaI-SmaI fragment of both plasmids was microinjected into the nuclei of oocytes or the cytoplasm of embryos at the one-cell stage. The gene expression was detected, using a fluorescent stereomicroscope, from early stages of development to 1 week after hatching. The expression of the wild-type GFP was detected in early embryos, in the yolk sac and in small portions of the muscle and epidermis. This expression pattern was similar to that of the Escherichia coli beta-galactosidase reporter gene (lacZ), driven by the medaka beta-actin promoter, which was examined in our previous studies. The mutant GFP was expressed in early embryos and in many tissues such as the epidermis, blood vessels, muscle, notochord, fin ray, gut, eyes, and yolk sac, and the fluorescence was much stronger than that of the wild-type GFP. Thus, the usefulness of the medaka beta-actin promoter as a ubiquitous expression vector was confirmed using the mutant GFP as a reporter gene.

Actins↗
PubMed1997

An embryological study of ventralization of dorsal structures in the tail of medaka (Oryzias latipes) Da mutants.

In adult Da (double anal fin) mutants of medaka (Oryzias latipes), structures such as the dorsal fin and the dorsal half of the caudal fin are ventralized in adult fish. However, there have been few embryological studies of the development of mutant phenotypes except those of the caudal fin. In this study, development of mutant phenotypes of the tail where they typically develop was examined morphologically at various stages of embryogenesis. The arrangement of melanocytes along the dorsal midline, the shape of the dorsal fin fold, and the shape of the dorsal myotome exhibited a ventral pattern in the tail at various embryonic stages in Da mutants.

Animals↗
PubMed1997

Regulation of the neural crest cell fate by N-myc: promotion of ventral migration and neuronal differentiation.

During neural crest development in avian embryos, transcription factor N-myc is initially expressed in the entire cell population. The expression is then turned off in the period following colonization in ganglion and nerve cord areas except for the cells undergoing neuronal differentiation. This was also recapitulated in the culture of Japanese quail neural crest, and the cells expressing N-myc eventually coincided with those expressing neurofilaments. These findings suggested that N-myc is involved in regulation of neuronal differentiation in the neural crest cell population. In fact, transient overexpression of N-myc in the neural crest culture by transfection resulted in a remarkable promotion of neuronal differentiation. An experimental procedure was developed to examine the effect of exogenous N-myc expression in the neural crest cells in embryos. Neural crest cell clusters still attached to the neural tube were excised from Japanese quail embryos, transfected and grafted into chicken host embryos. Using this chimera technique, we were able to analyze the consequence of transient high N-myc during the early phase of neural crest migration. Two effects were demonstrated in the embryos: first, high N-myc expression provoked massive ventral migration of the neural crest population and, second, those cells that migrated to the ganglion-forming areas underwent neuronal differentiation with the cell type determined by the nature of the ganglion. Thus, N-myc is involved in regulation of the neural crest fate in two different aspects: ventral migration and neuronal differentiation.

Animals↗
PubMed1997

Sequential expression and role of Hu RNA-binding proteins during neurogenesis.

We have identified three avian (chicken) Hu/elav family RNA-binding protein genes. cHuD and cHuC are expressed specifically in neurons of both the central and peripheral nervous systems. Although cHuA is expressed in a wide variety of tissues, including neurogenic precursor cells, it is transiently down-regulated, and is then re-expressed in maturing neurons. Misexpression of cHuD in cultured neural crest cells results in a dramatic increase in the proportion of cells exhibiting neuronal morphology, molecular markers for neurons, and neurotrophin dependence. These data confirm that cHuD protein is involved in regulating neuronal differentiation.

3T3 Cells↗
PubMed1996

Transgenic expression of L-gulono-gamma-lactone oxidase in medaka (Oryzias latipes), a teleost fish that lacks this enzyme necessary for L-ascorbic acid biosynthesis.

Transfer of the gene for L-gulono-gamma-lactone oxidase, the missing enzyme in L-ascorbic acid biosynthesis in scurvy-prone animals, into medaka (Oryzias latipes) was successfully done. The expression plasmid pSVL-GLO, carrying rat liver L-gulono-gamma-lactone oxidase cDNA, was microinjected into the cytoplasm of fertilized eggs during the one-cell stage. Four male F0 fish having the transgene in their germ cells came to maturity, and F1 progeny derived from one of the F0 fish possessed L-gulono-gamma-lactone oxidase activity, indicating that the transgene was functionally expressed in the fish. Genomic Southern blot analysis demonstrated that the transgene existed in both chromosome-integrated and extrachromosomal forms.

Animals↗
PubMed1996

Regionalized expression of the Dbx family homeobox genes in the embryonic CNS of the mouse.

Here we report the identification of a novel homeobox gene family Dbx in mouse, which consists of Dbx and Dbx2. The two genes share similar structural organization and are encoded by different chromosomes. The predicted Dbx and Dbx2 proteins share 85% identity in their homeodomain amino acid sequences, but otherwise showed no significant similarity. Characterization of the expression of these two genes in the embryos suggested their role in the development of the CNS. In the forebrain, Dbx is expressed in various regions, while Dbx2 showed a more restricted pattern of expression. In the midbrain, the expression domains of Dbx and Dbx2 overlap along the dorso-lateral wall of the ventricle. In the hindbrain and spinal cord, both genes are expressed in the boundary separating the basal and alar plates, which seems to correspond to the sulcus limitans. Expression of the Dbx/Dbx2 genes is restricted to the ventricular region of the embryonic CNS except for that of Dbx in the septum of the telencephalon. Together these observations indicate possible participation of the members of the Dbx family in regionalization of the CNS. While the expression of Dbx was restricted to the CNS, Dbx2 was also expressed in some of the mesenchymal cells, such as limb buds and tooth germs.

Amino Acid Sequence↗
PubMed1995

Initiation of the transgenic lacZ gene expression in medaka (Oryzias latipes) embryos.

In total, 4165 medaka (Oryzias latipes) oocytes were injected with three DNA constructs separately, and results showed that exogenous lacZ expression was transient and stage-dependent. The initiation of the transgene expression was at the mid-blastula stage for embryos derived from oocytes injected with pmiwZ, containing the long terminal repeat (LTR) of the Rous sarcoma virus, and with pCAGGS-lacZ, containing the enhancer and promoter of the immediate early gene of the human cytomegalovirus, respectively, whereas embryos derived from oocytes injected with pMoZtk, containing the LTR of the Moloney murine leukemia virus, started expression at the late-blastula stage. These reveal that the earliest onset of the exogenous lacZ gene should be by the mid-blastula stage. Therefore the mid-blastula transition phenomenon in embryogenesis known in other animal species exists in medaka embryos.

Animals↗
PubMed1994

Establishment of a pluripotent cell line derived from a medaka (Oryzias latipes) blastula embryo.

A pluripotent cell line, OLES1, was established from a blastula embryo of a small freshwater fish, medaka (Oryzias latipes). Cells of this cell line were small and round, and they grew actively and stably in culture as dense clusters. They exhibited a positive alkaline phosphatase activity upon histochemical staining. When the cells were treated with retinoic acid, differentiation into various types of cells, including melanocytes, dopa-positive precursors of melanocytes, and cells with a molecular marker of skeletal muscles, troponin T, was induced in vitro. The present study opens a way to establishing embryonic stem cell lines in fish.

Alkaline Phosphatase↗