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Biomedical subjects

Y Saga

Publications and source records attributed to Y Saga.

At least 37 records · Page 2Linked to original sources
PubMed2000

Mesp2 initiates somite segmentation through the Notch signalling pathway.

The Notch-signalling pathway is important in establishing metameric pattern during somitogenesis. In mice, the lack of either of two molecules involved in the Notch-signalling pathway, Mesp2 or presenilin-1 (Ps1), results in contrasting phenotypes: caudalized versus rostralized vertebra. Here we adopt a genetic approach to analyse the molecular mechanism underlying the establishment of rostro-caudal polarity in somites. By focusing on the fact that expression of a Notch ligand, Dll1, is important for prefiguring somite identity, we found that Mesp2 initiates establishment of rostro-caudal polarity by controlling two Notch-signalling pathways. Initially, Mesp2 activates a Ps1-independent Notch-signalling cascade to suppress Dll1 expression and specify the rostral half of the somite. Ps1-mediated Notch-signalling is required to induce Dll1 expression in the caudal half of the somite. Therefore, Mesp2- and Ps1-dependent activation of Notch-signalling pathways might differentially regulate Dll1 expression, resulting in the establishment of the rostro-caudal polarity of somites.

Animals↗
PubMed2000

A novel strategy for the tumor angiogenesis-targeted gene therapy: generation of angiostatin from endogenous plasminogen by protease gene transfer.

When NIH 3T3 fibroblasts were transduced with a retroviral vector containing a cDNA for porcine pancreatic elastase 1 and cultured in the presence of affinity-purified human plasminogen, the exogenously added plasminogen was digested to generate the kringle 1-3 segment known as angiostatin, a potent angiogenesis inhibitor. This was evidenced by immunoblot analysis of the plasminogen digests using a monoclonal antibody specifically reacting with the kringle 1-3 segment, and by efficient inhibition of proliferation of human umbilical vein endothelial cells by the plasminogen digests isolated from the culture medium of 3T3 fibroblasts. However, when Lewis lung carcinoma cells were transduced with the same vector and injected subcutaneously into mice in their back or via the tail vein, their growth at the injection sites or in the lungs was markedly suppressed compared with the growth of similarly treated nontransduced Lewis lung carcinoma cells. Nevertheless, the transduced cells were able to grow as avidly as the control cells in vitro. Assuming that the elastase 1 secreted from the transduced cells is likely to be exempt from rapid inhibition by its physiological inhibitor, alpha1-protease inhibitor, as shown in the inflammatory tissues, the elastase 1 secreted from the tumor cells may effectively digest the plasminogen that is abundantly present in the extravascular spaces and generate the kringle 1-3 segment in the vicinity of implanted tumor cell clusters. Although the selection of more profitable virus vectors and cells to be transduced awaits further studies, such a protease gene transfer strategy may provide us with a new approach to anti-angiogenesis gene therapy for malignant tumors and their metastasis in vivo.

3T3 Cells↗
PubMed2000

Roles of p53 and MDM2 in tumor proliferation and determination of the prognosis of transitional cell carcinoma of the renal pelvis and ureter.

BACKGROUND: The significance of p53 overexpression for the prognosis of transitional cell carcinoma (TCC) of the renal pelvis and ureter remains controversial. Simultaneous evaluation of p53 and MDM2 may enable better prediction of tumor proliferation and patient prognosis than that obtained with evaluation of p53 alone. METHODS: Immunohistochemical detection of p53 protein, MDM2 protein and Ki-67 antigen as proliferation markers was performed for tissue samples obtained from 74 patients with TCC of the renal pelvis and ureter. The correlations of p53/MDM2 overexpression with conventional pathological features, Ki-67 labelling index (LI) and patient survival were studied. RESULTS: Overexpression of p53 was related to progression of each of the pathological features examined (grade, stage, type of infiltration, vascular invasion and lymphatic invasion) and Ki-67 LI was significantly higher with high p53 expression than with low p53 expression. However, overexpression of MDM2 was related to neither disease progression nor Ki-67 LI. Survival analyses were performed for 66 patients. Univariate analysis showed p53 to be a useful prognostic indicator, but in a multivariate analysis only type of infiltration and Ki-67 LI were independent survival markers, while p53 was not. Overexpression of MDM2 was unrelated to patient survival, and the combination of p53 and MDM2 for survival indication was found not to be useful. CONCLUSIONS: Overexpression of p53 is related to disease progression, increased tumor proliferation and patient survival for TCC of the renal pelvis and ureter, but the independent prognostic value of p53 did not reach statistical significance. Combined analysis of MDM2 with p53 cannot be recommended for examination of the malignant potential of TCC of the renal pelvis and ureter.

Adult↗
PubMed2000

Recurrent ovarian clear cell carcinoma: complete remission after radiation in combination with hyperthermia; a case study and in vitro study.

Since clear cell carcinoma of the ovary does not respond to conventional platinum-based chemotherapy, the prognosis of recurrent tumors is especially poor. In a 51-year old female who underwent surgery for clear cell carcinoma of the ovary, a solitary metastatic carcinoma developed in the pelvic cavity seven months after the initial surgery. The patient underwent a whole pelvic irradiation at a total dose of 65 Gy combined with hyperthermia. Complete remission was achieved 46 months after treatment. A study using gynecologic carcinoma cell lines showed that the mean 50% growth inhibitory dose of radiation was 1.2 +/- 0.4 Gy in several clear cell carcinoma cell lines. The value did not significantly differ from those for serous carcinoma cell lines (2.3 +/- 1.2 Gy) and uterine cervical carcinoma cell lines (1.6 +/- 0.4 Gy). Currently, no anticancer agents are effective for clear cell carcinoma. Radiotherapy combined with hyperthermia may be effective for localized tumors.

Adenocarcinoma, Clear Cell↗
PubMed2000

Role of the Y1 receptor in the regulation of neuropeptide Y-mediated feeding: comparison of wild-type, Y1 receptor-deficient, and Y5 receptor-deficient mice.

Neuropeptide Y (NPY) increases food intake through the action of hypothalamic NPY receptors. At least six subtypes of NPY, peptide YY (PYY), and pancreatic polypeptide (PP) receptors have been identified in mice. Although the involvement of Y1 and Y5 receptors in feeding regulation has been suggested, the relative importance of each of these NPY receptors and the participation of a novel feeding receptor are still unclear. To address this issue, we generated a Y1 receptor-deficient (Y1-/-) and a Y5 receptor-deficient (Y5-/-) mouse line in which we directly compared the orexigenic effects of NPY and its analogs after intracerebroventricular (icv) administration. The icv NPY-induced food intake was remarkably reduced in Y1-/- mice, but was not significantly altered by inactivation of the Y5 receptor. The Y1 receptor therefore plays a dominant role in NPY-induced feeding. Stimulation of feeding by moderately selective Y5 agonists [PYY-(3-36), human PP, and bovine PP] was reduced in Y5-/- mice, although food intake did not decrease to vehicle control levels. These results indicate that the Y5 receptor functions as one of the feeding receptors. In addition, the finding that Y5-preferring agonists still induce food intake in Y5-/- mice suggests a role for another NPY receptor(s), including the possibility of novel NPY receptors. Surprisingly, despite the limited efficacy of PYY-(3-36) and PPs at the Y1 receptor, food consumption induced by these agonists was significantly diminished in Y1-/- mice compared with that in wild-type controls. These observations suggest that the feeding stimulation induced by NPY and its analogs may be directly or indirectly modulated by the action of the Y1 receptor. We conclude that multiple NPY receptors, possibly including the novel feeding receptor, are involved in the feeding response evoked by NPY and its analogs. Among them, the Y1 receptor plays a key role in NPY-induced feeding in mice.

Animals↗
PubMed2000

MesP1 and MesP2 are essential for the development of cardiac mesoderm.

The transcription factors, MesP1 and MesP2, sharing an almost identical bHLH motif, have an overlapping expression pattern during gastrulation and somitogenesis. Inactivation of the Mesp1 gene results in abnormal heart morphogenesis due to defective migration of heart precursor cells, but somitogenesis is not disrupted because of normal expression of the Mesp2 gene. To understand the cooperative functions of MesP1 and MesP2, either a deletion or sequential gene targeting strategy was employed to inactivate both genes. The double-knockout (dKO) embryos died around 9.5 days postcoitum (dpc) without developing any posterior structures such as heart, somites or gut. The major defect in this double-knockout embryo was the apparent lack of any mesodermal layer between the endoderm and ectoderm. The abnormal accumulation of cells in the primitive streak indicates a defect in the migratory activity of mesodermal cells. Molecular markers employed to characterize the phenotype revealed a lack of the cranio-cardiac and paraxial mesoderm. However, the axial mesoderm, as indicated by brachyury (T) expression, was initially generated but anterior extension was halted after 8.5 dpc. Interestingly, a headfold-like structure developed with right anterior-posterior polarity; however, the embryos lacked any posterior neural properties. The persistent and widely distributed expression of Cerberus-like-1(Cer1), Lim1 and Otx2 in the anterior endoderm might be responsible for the maintenance of anterior neural marker expression. We also performed a chimera analysis to further study the functions of MesP1 and MesP2 in the development of mesodermal derivatives. In the chimeric embryos, dKO cells were scarcely observed in the anterior-cephalic and heart mesoderm, but they did contribute to the formation of the somites, notochord and gut. These results strongly indicate that the defect in the cranial-cardiac mesoderm is cell-autonomous, whereas the defect in the paraxial mesoderm is a non-cell-autonomous secondary consequence.

Animals↗
PubMed2000

Zebrafish Mesp family genes, mesp-a and mesp-b are segmentally expressed in the presomitic mesoderm, and Mesp-b confers the anterior identity to the developing somites.

Segmentation of a vertebrate embryo begins with the subdivision of the paraxial mesoderm into somites through a not-well-understood process. Recent studies provided evidence that the Notch-Delta and the FGFR (fibroblast growth factor receptor) signalling pathways are required for segmentation. In addition, the Mesp family of bHLH transcription factors have been implicated in establishing a segmental prepattern in the presomitic mesoderm. In this study, we have characterized zebrafish mesp-a and mesp-b genes that are closely related to Mesp family genes in other vertebrates. During gastrulation, only mesp-a is expressed in the paraxial mesoderm at the blastoderm margin. During the segmentation period, both genes are segmentally expressed in one to three stripes in the anterior parts of somite primordia. In fused somites (fss) embryos, in which all early somite boundary formation is blocked, initial mesp-a expression at the gastrula stage remains intact, but the expression of mesp-a and mesp-b is not detected during the segmentation period. This suggests that these genes are downstream targets of fss at the segmentation stage. Comparison with her1 expression (Müller, M., von Weizsäcker, E. and Campos-Ortega, J. A. (1996) Development 122, 2071-2078) suggests that, like her1, mesp genes are not expressed in primordia of the first several somites. Furthermore, we found that zebrafish her1 expression oscillates in the presomitic mesoderm. The her1 stripe, which first appears in the tailbud region, moves in a caudal to rostral direction, and it finally overlaps the most rostral mesp stripe. Thus, in the trunk region, both her1 and mesp transcripts are detected in every somite primordium posterior to the forming somites. Ectopic expression of Mesp-b in embryos causes a loss of the posterior identity within the somite primordium, leading to a segmentation defect. These embryos show a reduction in expression of the posterior genes, myoD and notch5, with uniform expression of the anterior genes, FGFR1, papc and notch6. These observations suggest that zebrafish mesp genes are involved in anteroposterior specification within the presumptive somites, by regulating the essential signalling pathways mediated by Notch-Delta and FGFR.

Amino Acid Sequence↗
PubMed1999

Impaired extrapyramidal function caused by the targeted disruption of retinoid X receptor RXRgamma1 isoform.

BACKGROUND: Retinoid X receptors RXRalpha, beta and gamma exert multiple functions in the genetic regulation of mammalian signalling systems by forming heterodimeric complexes with several nuclear ligand receptors. In contrast to the widespread expression of RXRalpha and RXRbeta, the expression of RXRgamma is restricted to particular tissues in which RXRgamma1 is the major isoform expressed in the mouse corpus striatum. RESULTS: To investigate the function of this particular isoform RXRgamma1, we generated RXRgamma1 gene-knockout mice by homologous recombination in ES cells. Both heterozygous and homozygous mice showed severe runting after birth, which often resulted in the early death of mice of the 129/C57BL-6 genetic background. Independent of genetic background, however, the expression of choline acetyltransferase (ChAT) in the cholinergic interneurones in the striatum (caudal putamen) was markedly reduced in the RXRgamma1 gene-null mice. Furthermore, the mutant exhibited an altered response to the administration of dopamine receptor antagonists, haloperidol and chlorpromazine, which normally induce catalepsy in mice. CONCLUSIONS: These results strongly suggest that RXRgamma1 plays an important role in either the development or activation of cholinergic neurones in nigrostriatal extrapyramidal pathways.

Animals↗
PubMed1999

Myelination and behaviour of tenascin-C null transgenic mice.

The extracellular matrix glycoprotein tenascin-C is widely expressed during development and repair, making it surprising that few abnormalities have been found in transgenic mice lacking this molecule. We have therefore re-examined the transgenic mice described by Saga et al. [Saga, Y., Yagi, T., Ikawa, Y., Sakakura, T. & Aizawa, S. (1992) Genes Dev., 6 1821-1831] in which tenascin-C was knocked-out by homologous recombination, focusing on two aspects of the nervous system likely to reveal any abnormalities that might follow the loss of tenascin-C. First, we have determined the pattern of myelin and distribution of oligodendrocyte precursor cells in those areas, such as the optic nerve and retina where local concentrations of tenascin-C have been proposed to act as barriers to oligodendrocyte precursor migration and so prevent inappropriate myelination. Secondly, we have examined the behaviour of the mice in a number of well-characterized tests, e.g. beam-walking, passive avoidance and the Morris water maze. We find no abnormalities of myelination or oligodendrocyte precursor distribution in adult mice, showing that local concentrations of tenascin-C are not the sole mechanism responsible for the pattern of myelination in these regions of CNS. However, we do find a number of behavioural abnormalities in these mice and show that hyperlocomotion and deficits in coordination during beam walking can be ascribed to tenascin-C deficiency. The effects on coordination are, however, not seen on a 129 genetic background. Taken together, these results significantly extend the phenotype associated with tenascin-C deficiency but argue against a role in myelination.

Animals↗
PubMed1999

Enhanced expression of thymidylate synthase may be of prognostic importance in advanced cervical cancer.

The enhanced expression of thymidylate synthase (TS) has been associated with a poor prognosis in patients with several types of epithelial tumors. To determine the association between TS expression and the prognosis of patients with advanced cervical cancer after radiation therapy, we immunohistochemically assayed TS levels in paraffin-embedded tissue sections from 66 patients with stage IIIb cervical cancer using a polyclonal antibody to recombinant human TS. In the 30 patients with high TS expression, the cumulative 5- and 8-year survival rates were 36.8% (95% CI: 17. 4-56.2) and 31.6% (95% CI: 12.4-50.7), respectively. In contrast, the 36 patients with low TS expression showed a significantly (p < 0. 001) better prognosis, with cumulative 5- and 8-year survival rates of 87.2% (95% CI: 75.5-99.0) and 69.2% (95% CI: 50.7-87.7), respectively. These results suggest that TS expression may be useful in determining the prognosis of patients with advanced cervical cancer.

Adult↗
PubMed1999

MesP1 is expressed in the heart precursor cells and required for the formation of a single heart tube.

The Mesp1 gene encodes the basic HLH protein MesP1 which is expressed in the mesodermal cell lineage during early gastrulation. Disruption of the Mesp1 gene leads to aberrant heart morphogenesis, resulting in cardia bifida. In order to study the defects in Mesp1-expressing cells during gastrulation and in the specification of mesodermal cell lineages, we introduced a (beta)-galactosidase gene (lacZ) under the control of the Mesp1 promoter by homologous recombination. The early expression pattern revealed by (beta)-gal staining in heterozygous embryos was almost identical to that observed by whole mount in situ hybridization. However, the (beta)-gal activity was retained longer than the mRNA signal, which enabled us to follow cell migration during gastrulation. In heterozygous embryos, the Mesp1-expressing cells migrated out from the primitive streak and were incorporated into the head mesenchyme and heart field. In contrast, Mesp1-expressing cells in the homozygous deficient embryos stayed in the primitive streak for a longer period of time before departure. The expression of FLK-1, an early marker of endothelial cell precursors including heart precursors, also accumulated abnormally in the posterior region in Mesp1-deficient embryos. In addition, using the Cre-loxP site-specific recombination system, we could determine the lineage of the Mesp1-expressing cells. The first mesodermal cells that ingressed through the primitive streak were incorporated as the mesodermal component of the amnion, and the next mesodermal population mainly contributed to the myocardium of the heart tube but not to the endocardium. These results strongly suggest that MesP1 is expressed in the heart tube precursor cells and is required for mesodermal cells to depart from the primitive streak and to generate a single heart tube.

Animals↗
PubMed1998

Identification and characterization of LMO4, an LMO gene with a novel pattern of expression during embryogenesis.

LMO4 is a novel member of the LIM-only (LMO) subfamily of LIM domain-containing transcription factors. LMO1, LMO2, and LMO4 have distinct expression patterns in adult tissue, and we demonstrate that nuclear retention of LMO proteins is enhanced by the nuclear LIM interactor (NLI). In situ hybridization to early mouse embryos of 8-14.5 days revealed a complex pattern of LMO4 expression spatially overlapping with NLI and LHX genes. LMO4 expression in somite is repressed in mice mutant for the segment polarity gene Mesp2 and expanded in Splotch mutants. During jaw and limb outgrowth, LMO4 and LMO2 expression define mesenchyme that is uncommitted to regional fates. Although both LMO2 and LMO4 are activated in thymic blast cells, only LMO4 is expressed in mature T cells. Mesenchymal and thymic blast cell expression patterns of LMO4 and LMO2 are consistent with the suggestion that LMO genes inhibit differentiation.

Adaptor Proteins, Signal Transducing↗
PubMed1998

Suppression of hematopoietic activity in tenascin-C-deficient mice.

Tenascin-C (TN-C), a member of the extracellular matrix (ECM) glycoprotein family, is expressed on the surface of stromal cells in the hematopoietic system or lymphoid organs. Recently, TN-C-deficient mutant mice produced by TN-C gene targeting through homologous recombination were shown to develop normally, although TNs have been reported to play important roles in organogenesis and carcinogenesis. In the present study, we found that colony-forming capacity of bone marrow (BM) cells was considerably lower in TN-C-deficient mice (a decrease of approximately 35% from control), although their mononuclear cell count and BM architecture showed no significant difference from those of normal mice. Furthermore, in long-term BM culture in vitro, hematopoietic cell production (a decrease of approximately 40% in Dexter's condition and of approximately 65% in Whitlock-Witte's condition from control), colony-forming capacity of the produced cells (a decrease of approximately 60% from control), and longevity of the cultures were markedly lower in the TN-C-deficient mice than in control mice, whereas hematopoiesis in the TN-C-deficient mutant mice was sustained. The addition of TN-C glycoprotein to long-term BM cultures of TN-C-deficient mice clearly induced the recovery of hematopoietic cell production and colony-forming capacity of hematopoietic progenitor cells. Thus, these results provide direct evidence that an ECM glycoprotein component, TN-C, plays a relevant role in hematopoiesis through interactions between stromal cells and hematopoietic progenitor cells.

Animals↗
PubMed1998

Loss of heterozygosity on chromosome 6q27 and p53 mutations in epithelial ovarian cancer.

Loss of heterozygosity (LOH) in chromosome region 6q27 and p53 mutations were studied to attempt to clarify the genetic etiology of ovarian cancer, with particular reference to clear cell adenocarcinoma (CCC), which has a poor prognosis. 6q27 LOH in 70 epithelial ovarian cancer patients was examined using four restriction fragment length polymorphism markers located at 6q27; p53 mutations in tumor DNA were detected using polymerase chain reaction single-strand conformation polymorphism and sequencing. 6q27 LOH was confirmed in 26 of 48 informative cases (54.2%). No differences in the incidence of 6q27 LOH were seen by histologic type; 6q27 LOH was observed in 45% (5/11) of CCCs. p53 mutations were detected in 19 of the 48 tumors (39.6%), but in only one (9%) CCC. These results suggest that a putative tumor suppressor gene involved in the onset of epithelial ovarian cancer is located at 6q27. This gene is one of the keys to clarifying the genetic etiology of epithelial ovarian cancer and particularly CCC, given the low incidence of p53 mutations in this tumor type.

Adenocarcinoma, Clear Cell↗
PubMed1998

Genetic rescue of segmentation defect in MesP2-deficient mice by MesP1 gene replacement.

Gene knock-out and knock-in strategies are employed to investigate the function of MesP1. MesP1 belongs to the same family of bHLH transcription factors as MesP2. The early expression pattern observed in the early mesoderm at the onset of gastrulation is restricted to Mesp1, while the later expression pattern in the anterior presomitic mesoderm during somitogenesis is almost the same for Mesp1 as for Mesp2. Homozygous Mesp1 null mice exhibited growth retardation after 7.5 dpc and died before 10.5 dpc with many developmental defects. The function of MesP1 during somitogenesis was not clearly revealed because of their early death and the possible compensation by MesP2. In order to examine the functions of MesP1 during somitogenesis, we replaced the Mesp2 gene with Mesp1 cDNA, using a gene knock-in strategy. The introduced Mesp1 cDNA could rescue the defects caused by Mesp2 deficiency in a dosage-dependent manner. Mice which lacked Mesp2 expression but had four copies of the Mesp1 gene survived into the adulthood and were fertile. The skeletal defects and the reduction in expression of Notch1, Notch2 and FGFR-1 previously observed in Mesp2 null mice were almost completely rescued by the introduced MesP1. Thus, it is concluded that the functions of MesP1 during somitogenesis, like MesP2, are also mediated via notch-delta and FGF signaling systems.

Abnormalities, Multiple↗
PubMed1998

The peripheral nerve and the neuromuscular junction are affected in the tenascin-C-deficient mouse.

A thorough examination of the structure and plasticity of the neuromuscular system was performed in tenascin-C mutant mice deficient in tenascin-C. The study of the peripheral nerve revealed a number of abnormal features. In the motor nerve, numerous unmyelinated and myelinated fibers with degraded myelin were present. Schwann cell processes often enclosed degenerative terminals. Transgene (beta-galactosidase) expression analyzed at the ultrastructural level was found to be unequally distributed in the mutant's neuromuscular tissues. At the NMJ, preterminal disorganization was prevalent. Some axon terminals exhibited abnormal overgrowth. A surprising lack of beta-galactosidase expression at some cellular sites known to possess tenascin-C in wild type mice correlated best with marked changes in the cytoarchitecture of the peripheral nerve and NMJ. In some other -but not all- cellular sites which normally express the molecule, immunofluorescence analysis suggested the presence of significant but low levels of tenascin-C-like immunoreactivity together with beta-galactosidase expression. Messenger RNA detection by RT-PCR confirmed the presence of low amounts of tenascin-C mRNA in skeletal muscle suggesting that the mice deficient in tenascin-C are not complete knock-outs of this gene, but low-expression mutants. Following in vivo injections of botulinum type-A toxin, we observed a greatly reduced sprouting response of the motor nerves in tenascin-C mutant mice. We also observed that N-CAM and beta-catenin were overexpressed in the mutant. Our results suggest that tenascin-C is involved both in stabilization and in plasticity of the NMJ.

Animals↗
PubMed1997

Tertiary hypothyroidism and hyperglycemia in mice with targeted disruption of the thyrotropin-releasing hormone gene.

Thyrotropin-releasing hormone (TRH) is a brain hypothalamic hormone that regulates thyrotropin (TSH) secretion from the anterior pituitary and is ubiquitously distributed throughout the brain and other tissues including pancreas. To facilitate studies into the role of endogenous TRH, we have used homologous recombination to generate mice that lack TRH. These TRH-/- mice are viable, fertile, and exhibit normal development. However, they showed obvious hypothyroidism with characteristic elevation of serum TSH level and diminished TSH biological activity. Their anterior pituitaries exhibited an apparent decrease in TSH immunopositive cells that was not due to hypothyroidism. Furthermore, this decrease could be reversed by TRH, but not thyroid hormone replacement, suggesting a direct involvement of TRH in the regulation of thyrotrophs. The TRH-/- mice also exhibited hyperglycemia, which was accompanied by impaired insulin secretion in response to glucose. These findings indicate that TRH-/- mice provide a model of exploiting tertiary hypothyroidism, and that TRH gene abnormalities cause disturbance of insulin secretion resulting in marked hyperglycemia.

Animals↗