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M Takeichi

Publications and source records attributed to M Takeichi.

At least 55 records · Page 3Linked to original sources
PubMed1998

Cytoskeletal reorganization by soluble Wnt-3a protein signalling.

BACKGROUND: Wnt-3a is an intercellular signalling molecule that is involved in a variety of morphogenetic events. However, the molecular mechanisms underlying Wnt-3a signalling are poorly understood. We have sought to establish in vitro systems to assay the activity of this protein and investigate its biological roles. RESULTS: We prepared mouse L cells transfected with Wnt-3a cDNA, and found that their beta-catenin protein level was up-regulated. When conditioned medium (CM) was collected from cultures of the transfectants and added to nontransfected L cells, the beta-catenin level of the latter was also increased. Approximately 50% of the Wnt-3a proteins synthesized by the transfectants were secreted into the CM in a soluble form. These secreted Wnt-3a proteins formed an activity gradient in the environment surrounding the transfectants. Then, we studied whether Wnt-3a had any effect on cellular behaviour in vitro. When the CM containing Wnt-3a (W3a-CM) was added to cultures of C57MG mammary epithelial cells, their morphology was altered to exhibit closer intercellular contacts. Immunostaining for various adhesion and cytoskeletal proteins showed that the actin-microfilamental system was re-organized by the W3a-CM treatment. It induced a directional alignment of actin stress fibres and other actin-associated proteins. Moreover, villin, localized only at the perinuclear regions in untreated C57MG cells, was re-distributed to the leading edges of the cells, co-localizing with F-actin, in the presence of Wnt-3a. CONCLUSION: Our findings suggest that Wnt-3a protein, in the soluble form, can act to re-organize cytoskeletal structures.

Actins↗
PubMed1998

Neural crest emigration from the neural tube depends on regulated cadherin expression.

During the emergence of neural crest cells from the neural tube, the expression of cadherins dynamically changes. In the chicken embryo, the early neural tube expresses two cadherins, N-cadherin and cadherin-6B (cad6B), in the dorsal-most region where neural crest cells are generated. The expression of these two cadherins is, however, downregulated in the neural crest cells migrating from the neural tube; they instead begin expressing cadherin-7 (cad7). As an attempt to investigate the role of these changes in cadherin expression, we overexpressed various cadherin constructs, including N-cadherin, cad7, and a dominant negative N-cadherin (cN390 ), in neural crest-generating cells. This was achieved by injecting adenoviral expression vectors encoding these molecules into the lumen of the closing neural tube of chicken embryos at stage 14. In neural tubes injected with the viruses, efficient infection was observed at the neural crest-forming area, resulting in the ectopic cadherin expression also in migrating neural crest cells. Notably, the distribution of neural crest cells with the ectopic cadherins changed depending on which constructs were expressed. Many crest cells failed to escape from the neural tube when N-cadherin or cad7 was overexpressed. Moreover, none of the cells with these ectopic cadherins migrated along the dorsolateral (melanocyte) pathway. When these samples were stained for Mitf, an early melanocyte marker, positive cells were found accumulated within the neural tube, suggesting that the failure of their migration was not due to differentiation defects. In contrast to these phenomena, cells expressing non-functional cadherins exhibited a normal migration pattern. Thus, the overexpression of a neuroepithelial cadherin (N-cadherin) and a crest cadherin (cad7) resulted in the same blocking effect on neural crest segregation from neuroepithelial cells, especially for melanocyte precursors. These findings suggest that the regulation of cadherin expression or its activity at the neural crest-forming area plays a critical role in neural crest emigration from the neural tube.

Adenoviridae↗
PubMed1998

Regional specification of muscle progenitors in Drosophila: the role of the msh homeobox gene.

The somatic musculature in the abdominal hemisegments of Drosophila consists of 30 uniquely identifiable muscle fibers. Previous studies have suggested that the muscle diversity originates in a special class of myoblasts, called muscle founders, that are formed by the division of muscle progenitors. However, the mechanisms that locate and specify the muscle progenitors/founders are largely unknown. In this study, we first used a novel marker, rP298-LacZ, to chart the development of muscle progenitors/founders during the formation of distinct groups of mature muscles. We then determined the function of the muscle segment homeobox (msh) gene in myogenesis. msh encodes a homeobox-containing protein, vertebrate homologues of which are known as Msxs. We show that msh is expressed in the dorsal and lateral domains of muscle progenitors and is required for the specification of the progenitor cells. Ectopic expression of msh in the entire mesoderm inhibits the proper development of the normally msh-negative muscle progenitors in the dorsolateral domain. These results suggest that msh plays a role in regional specification of muscle progenitors/founders.

Animals↗
PubMed1997

Precocious mammary gland development in P-cadherin-deficient mice.

To investigate the functions of P-cadherin in vivo, we have mutated the gene encoding this cell adhesion receptor in mice. In contrast to E- and N-cadherin- deficient mice, mice homozygous for the P-cadherin mutation are viable. Although P-cadherin is expressed at high levels in the placenta, P-cadherin-null females are fertile. P-cadherin expression is localized to the myoepithelial cells surrounding the lumenal epithelial cells of the mammary gland. The role of the myoepithelium as a contractile tissue necessary for milk secretion is clear, but its function in the nonpregnant animal is unknown. The ability of the P-cadherin mutant female to nurse and maintain her litter indicates that the contractile function of the myoepithelium is not dependent on the cell adhesion molecule P-cadherin. The virgin P-cadherin-null females display precocious differentiation of the mammary gland. The alveolar-like buds in virgins resemble the glands of an early pregnant animal morphologically and biochemically (i.e., milk protein synthesis). The P-cadherin mutant mice develop hyperplasia and dysplasia of the mammary epithelium with age. In addition, abnormal lymphocyte infiltration was observed in the mammary glands of the mutant animals. These results indicate that P-cadherin-mediated adhesion and/or signals derived from cell-cell interactions are important determinants in negative growth control in the mammary gland. Furthermore, the loss of P-cadherin from the myoepithelium has uncovered a novel function for this tissue in maintaining the undifferentiated state of the underlying secretory epithelium.

Animals↗
PubMed1997

Accumulation of Armadillo induced by Wingless, Dishevelled, and dominant-negative Zeste-White 3 leads to elevated DE-cadherin in Drosophila clone 8 wing disc cells.

Drosophila genetic studies suggest that in the Wingless (Wg) signaling pathway, the segment polarity gene products, Dishevelled (Dsh), Zeste-white 3 (ZW-3), and Armadillo (Arm), work sequentially; wg and dsh negatively regulate zw-3, which in turn down-regulates arm. To biochemically analyze interactions between the Wg pathway and Drosophila E-cadherin (DE-cadherin) which bind to Arm, we overexpressed Dsh, ZW-3, and Arm, in the Drosophila wing disc cell line, clone 8, which responds to Wg signal. Dsh overexpression led to accumulation of Arm primarily in the cytosol and elevation of DE-cadherin at cell junctions. Overexpression of wild-type and dominant-negative forms of ZW-3 decreased and increased Arm levels, respectively, indicating that modulation in zw-3 activity negatively regulates Arm levels. Overexpression of an Arm mutant with an amino-terminal deletion elevated DE-cadherin levels, suggesting that Dsh-induced DE-cadherin elevation is caused by the Arm accumulation induced by Dsh. Moreover, the Dsh-, dominant-negative ZW-3-, and truncated Arm-induced accumulation of DE-cadherin protein was accompanied by a marked increase in the steady-state levels of DE-cadherin mRNA, suggesting that transcription of DE-cadherin is activated by Wg signaling. In addition, overexpression of DE-cadherin elevated Arm levels by stabilizing Arm at cell-cell junctions.

Adaptor Proteins, Signal Transducing↗
PubMed1997

A potential role of R-cadherin in striated muscle formation.

We have examined the murine embryonic expression pattern of the cell adhesion molecule R-cadherin in muscle, kidney, thymus, and lung. In developing muscle, R-cadherin was first seen at 10.5-11.5 days postcoitum in the somitic myotome. Consistently, we found R-cadherin expressed at the highest levels in the myotome, early skeletal muscle, and smooth muscle (both vascular and visceral), while very low levels of R-cadherin were detected in the heart. The expression pattern and subcellular localization of R-cadherin in developing skeletal muscle indicate a possible role in myoblast cell-cell interactions during both primary and secondary myogenesis. In the developing kidney, R-cadherin was first detected at 10.5 days postcoitum in the mesonephric epithelial tubule cells. In the metanephric kidney, it was specifically expressed in the pretubular aggregates, comma- and S-shaped bodies, proximal tubules, and collecting ducts. Thus, in the kidney, R-cadherin was associated with the mesenchymal-epithelial transition. R-cadherin was also found in other developing epithelia, for example in the thymic epithelial cells. In the lung, R-cadherin was expressed at the highest levels in the smooth muscle surrounding the lung epithelial tubules. To test whether R-cadherin can direct formation of tissues, we constitutively expressed R-cadherin in E-cadherin-/- ES cells and examined histogenesis in teratomas derived from these cells. R-cadherin exclusively rescued formation of striated muscle and epithelia in the teratomas. R-cadherin's ability to form epithelia in vivo was substantiated by its ability to rescue formation of cystic embryoid bodies in vitro. By comparing our data with the previously reported embryonic expression patterns and histogenetic activities of E- and N-cadherin, we suggest that R-cadherin plays an important role in the formation of striated muscle and possibly also of epithelia.

Animals↗
PubMed1997

M-spondin, a novel ECM protein highly homologous to vertebrate F-spondin, is localized at the muscle attachment sites in the Drosophila embryo.

The muscle attachment site (MAS) in Drosophila provides a unique and excellent model system to study the mechanism of cell-matrix adhesion in developing organisms. Here, we report on the isolation and characterization of a novel extracellular matrix (ECM) molecule localized at the MAS, encoded by the M-spondin (mspo) gene. M-spondin protein contains a thrombospondin type I repeat (TSR) previously found in a variety of ECM molecules. Furthermore, it shares two conserved domains with F-spondin, a vertebrate ECM molecule with TSRs. The presence of TSR(s) and the two homologous domains thus defines a novel gene family of ECM molecules. The mspo mRNA was expressed by a large subset of muscles in the embryonic body wall. Secreted M-spondin protein diffused and eventually became immobilized at the MAS in late embryos. When expressed in S2 cells, the protein was secreted and became concentrated in the matrix on the surface of the culture dish. Genetic analysis revealed that both deletion mutants and misexpression mutants suffered no obvious developmental defects. We propose that M-spondin, although its function is redundant, is a component of the ECM and mediates mechanical linkage between the muscles and apodemes.

Amino Acid Sequence↗
PubMed1997

Suppression of invasive ability of highly metastatic rat prostate cancer by introduction of human chromosome 8.

BACKGROUND: Introduction of human chromosome 8 to a highly metastatic subline (AT6.2) from the Dunning R-3327 rat prostate cancer resulted in suppression of metastatic ability of the resultant microcell hybrids (AT6.2-8 clones) [12]. The present study has been performed to clarify which step of metastasis was suppressed in the microcell hybrids. METHODS: Northern blot analysis of E-cadherin and alpha-catenin, in vitro invasion assay, and intra-venous metastasis assay by injection of tumor cells into the lateral tail vein of nude mice were performed. RESULTS: No detectable expressions of either E-cadherin or alpha-catenin were found in either AT6.2 parental or AT6.2-8 microcell hybrid clones. In the invasion assay, invasiveness of AT6.2-8 hybrid clones was less than that of the AT6.2 parental clone. In the intravenous metastasis assay, no significant differences in the number of lung metastases were observed among these cell lines. CONCLUSIONS: Introduction of human chromosome 8 to AT6.2 cells shows suppression of invasiveness and no suppression of cell dissociation or process after entry into blood circulation. This suggests that human chromosome 8 contains suppressor gene(s) for the invasive ability of prostate cancer.

Animals↗
PubMed1997

Cadherin-6 expression transiently delineates specific rhombomeres, other neural tube subdivisions, and neural crest subpopulations in mouse embryos.

Mammalian cadherin-6 (K-cadherin, cad6) was originally identified by means of the polymerase chain reaction, but its biological functions have not yet been determined. We analyzed the expression pattern of the mouse homologue of this cadherin during development and found that it was transiently expressed in restricted rhombomeres and in other subdivisions of the neural plate and tube. In the midbrain and anterior hindbrain of E8.0-8.5 embryos, cad6 was expressed only in neural crest-generating regions. In contrast, in the posterior hindbrain and contiguous spinal cord of these embryos, cad6 occurred throughout the neural plate, forming a sharp anterior limit at the future rhombomere 4 and 5 boundary. Subsequently, this neural plate expression became confined to rhombomere 6, although most of the neural crest-generating areas remained positive throughout the body. Neural crest cells expressing cad6 migrated out of the neural tube, and subsequently accumulated mainly along peripheral nerves. We then studied the effect of Hoxa-1 mutation on the expression of cad6, as their expressions spatiotemporally overlapped with each other in the early posterior hindbrain. In E8.0-8.5 Hoxa-1 mutants, cad6 expression was suppressed in the region of rhombomeres 4 to 6, although that in the other regions was not essentially affected. At later stages, however, cad6-positive crest cells appeared and migrated out of rhombomeres 4 to 6, indicating that the suppression of cad6 expression was transient and restricted to early stages. Importantly, this effect of the Hoxa-1 mutation concurred with the timing of the expression of this gene. We also studied Hoxa-3 mutants, but found no effect of this mutation on the cad6 expression pattern. These findings suggest that cad6 may contribute to the formation of the segmental structure of the early brain through its ability to confer specific adhesiveness on cells and that Hoxa-1 may be required for early cad6 expression in the posterior hindbrain.

Amino Acid Sequence↗
PubMed1997

Developmental defects in mouse embryos lacking N-cadherin.

To investigate the functions of N-cadherin in vivo, we have mutated the gene encoding this adhesion protein in mice. Although N-cadherin is expressed at the time of gastrulation and neurulation, both neurulation and somitogenesis initiate apparently normally in homozygous mutant embryos. However, the resulting structures are often malformed. The somites of the mutant embryos are small, irregularly shaped, and less cohesive compared with those of their wild-type littermates, and the epithelial organization of the somites is partially disrupted. Undulation of the neural tube is also observed in the mutant embryos. Homozygous mutant embryos die by Day 10 of gestation. The mesodermal and endodermal cell layers of the yolk sac are separated in the mutants. The most dramatic cell adhesion defect is observed in the primitive heart; although myocardial tissue forms initially, the myocytes subsequently dissociate and the heart tube fails to develop normally. In vitro studies of cardiac myocytes derived from N-cadherin mutant embryos show that the cells can loosely aggregate and beat synchronously, demonstrating that electrical coupling can occur between N-cadherin-deficient cardiac myocytes. These results show that N-cadherin plays a critical role in early heart development as well as in other morphogenetic processes.

Animals↗
PubMed1997

Cloning and expression analysis of cadherin-10 in the CNS of the chicken embryo.

A full-length cDNA of a novel cadherin of chicken (cad10) was cloned. The deduced amino acid sequence of the putative cytoplasmic domain of this molecule is highly homologous to a previously published cytoplasmic fragment of human cadherin-10, a type II cadherin. An in situ hybridization analysis in chicken embryos shows that cad10 expression starts at about 4 days' incubation (E4) and persists at least until the hatching stage. In the central nervous system (CNS), cad10 expression is spatially restricted at all stages of development. At early stages, expression reflects the neuromeric organization of the brain. For example, in the alar plate of the diencephalon, cad10 expression is restricted to the dorsal thalamic neuromere. A number of cad10-expressing brain nuclei are formed in this neuromeric domain during later development. Specific cad10-expressing gray matter structures are also found in all other major divisions of the brain. Many of these structures are known to be functionally connected to each other. The cad10 expression pattern is distinct from that of other cadherins. These results support the idea that cadherins provide a molecular code for the regionalization of the embryonic CNS at the different stages of development.

Animals↗
PubMed1997

Neuronal circuits are subdivided by differential expression of type-II classic cadherins in postnatal mouse brains.

A number of type-II classic cadherin cell-cell adhesion molecules are expressed in the brain. To investigate their roles in brain morphogenesis, we selected three type-II cadherins, cadherin-6 (cad6), -8 (cad8) and -11 (cad11), and mapped their expressions in the forebrain and other restricted regions of postnatal mouse brains. In the cerebral cortex, each cortical area previously defined was delineated by a specific combinatorial expression of these cadherins. The thalamus and other subcortical regions of the forebrain were also subdivided by differential expression of the three cadherins; e.g., the medial geniculate body expressed only cad6; the ventral posterior thalamic nucleus, cad6/cad11; and the anteroventral thalamic nucleus, cad6/cad8. Likewise, in the olivocerebellar system, each subdivision of the inferior olive expressed a unique set of the three cadherins, and the cerebellar cortex had parasagittal stripes of cad8/cad11 expressions. Close analysis of these cadherin expression patterns revealed that they are correlated with neuronal connection patterns. Examples of these correlations include that cad6 delineates the auditory projection system, cad6/cad8/ cad11 are expressed by part of the Papez circuit, and cad6/cad8 are expressed by subdivisions of the olivo-nuclear circuit. Together with the recent finding that the cadherin adhesion system is localized in synaptic junctions, our findings support the notion that cadherin-mediated cell-cell adhesion plays a role in selective interneuronal connections during neural network formation.

Animals↗
PubMed1997

Developmental changes in the subcellular localization of R-cadherin in chick retinal pigment epithelium.

It has been reported that in the chick embryonic retina, N-cadherin first appears at the very early stages and is subsequently substituted by R-cadherin at the middle to late stages of development. To examine the role of R-cadherin in the morphogenesis of chick retinal pigment epithelium (RPE), the distribution of this adhesion molecule was studied by immunofluorescence cytochemistry and immunoelectron microscopy from embryonic day (E) 6 to hatching. R-cadherin immunoreactivity was detected at E6, and was strongest at E12-13. During these stages, R-cadherin was expressed uniformly on the lateral plasma membranes of RPE cells in contact with each other. Thereafter, R-cadherin immunoreactivity was markedly decreased, with intense immunoreactivity restricted to zonulae adherentes in latero-apical regions at E16. R-cadherin immunoreactivity was no longer detectable in the newly hatched chick RPE, even though morphologically well developed zonulae adherentes were present in latero-apical regions. No immunoreactivity was detected on the apical side facing the neural retina or on the basal side facing the basal lamina at any stage of development. These findings indicate that R-cadherin plays an important role as a major cadherin subtype in the morphogenesis of chick embryo RPE, and is involved initially in non-specific cell-cell adhesions, and subsequently in the formation and maintenance of developing zonulae adherentes.

Animals↗
PubMed1997

Axon patterning requires DN-cadherin, a novel neuronal adhesion receptor, in the Drosophila embryonic CNS.

We identified DN-cadherin, a novel Drosophila cadherin that is expressed in axons and in the mesoderm. Although DN-cadherin has diverged from vertebrate classic cadherins in terms of its extracellular structure, it still can form a complex with catenins and induce cell aggregation, as do the vertebrate molecules. Loss-of-function mutations of the gene resulted in either embryonic lethality or uncoordinated locomotion of adults. In the central nervous system of null mutant embryos, subsets of ipsilateral axons displayed a variety of aberrant trajectories including failure of position shifts, defective bundling, and errors in directional migration of growth cones. These results suggest that processes of axon patterning critically depend on DN-cadherin-mediated axon-axon interactions.

Animals↗
PubMed1997

Phenotypic analysis of null mutants for DE-cadherin and Armadillo in Drosophila ovaries reveals distinct aspects of their functions in cell adhesion and cytoskeletal organization.

BACKGROUND: DE-cadherin is an epithelial cadherin in Drosophila, and forms adherens junctions by associating with Armadillo (beta-catenin). To investigate its role in oogenesis, we generated germ-line clones homozygous for a null mutation in shotgun (shg) encoding this molecule, and examined their phenotypes, comparing with those of armadillo (arm) mutants. RESULTS: In the wild-type ovaries, DE-cadherin was expressed by both the germ-line and somatic derivatives, colocalizing with Armadillo. In the shg mutant ovaries in which the mutation was restricted to the germ line, germ cells were rounded, and generated gaps between themselves, suggesting that their surface adhesiveness was reduced or lost. However, the positioning of germ cells in the egg chamber was normal. Two groups of somatic follicle cells--the border cells and centripetal follicle cells--frequently migrated along incorrect pathways, indicating that DE-cadherin is required for their appropriate migration. Notably, the shg phenotypes were distinct from those of arm null mutants. Intercellular adhesion appeared to be less severely affected by arm than by the shg mutation, and the actin-based cytoskeleton and cell arrangement were disorganized only in the arm mutants. CONCLUSIONS: These findings suggest that DE-cadherin is critical for cell-cell adhesion, and functional to a certain extent without Armadillo, whereas Armadillo is required for cytoskeletal organization and for the control of cell positioning. We therefore propose that the molecular complex of DE-cadherin and Armadillo which is present in normal cells is endowed with multiple functions derived from each molecule.

Actins↗
PubMed1997

N-cadherin is crucial for heart formation in the chick embryo.

The developing heart primordium strongly expresses N-cadherin. In order to investigate the role of this adhesion molecule in heart morphogenesis, chicken embryos were cultured at stages 5-12, and injected with anti-N-cadherin antibodies that can specifically block the activity of this cadherin. In the injected embryos, the epimyocardial layers, which develop bilaterally from the splanchnic mesoderm, did not fuse to form a single cardiac tube. Moreover, each of the unfused layers became fragmented into epithelioid clusters. At the cellular level, large intercellular gaps were observed in the antibody-treated myocardial layers. These disorganized myocardial layers beat to some extent, suggesting that their differentiation was not blocked; however, their contraction was not coordinated. Morphogenesis of other tissues, not only N-cadherin-negative but also N-cadherin-positive tissues, such as the neural tube and notochord, proceeded normally even in the presence of anti-N-cadherin antibodies. These results suggest that N-cadherin is indispensable for heart formation, but not for morphogenesis of the other tissues, at the developmental stages examined. For the latter processes, expression of other cadherin subtypes presumably compensated for the loss of N-cadherin activity.

Animals↗
PubMed1997

Computerized color analysis of "xue yu" (blood stasis) in the sublingual vein using a new technology.

Computer-assisted image analyses were performed on the color of the tongues of 95 medical students to enhance the accuracy and objectivity of tongue inspections for determining blood stasis. Areas from the sublingual vein were selected and subjected to image analysis. A slide scanner was used to digitize the color slides, and the digital information was transmitted to a personal computer for subsequent feature extraction and analysis. A comparison was then made between the computerized data using Red-Green-Blue color components, and inspection with the naked eye based on the diagnostics of traditional Chinese medicine. The results obtained suggest that there are statistically significant correlations between visual analyses and the computerized normalized R value (F value; 3.397, p < 0.05). The examination of sublingual veins with the naked eye showed the validity of computer-assisted image analysis. This analysis may provide a potential solution to the demand for a sophisticated means of quantitative and qualitative observation of physiological parameters regarding blood stasis, including that for the sublingual vein.

Adult↗