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Wnt Signaling Pathway (wnt + signaling_pathway)
Kinds of Wnt Signaling Pathway Selected AbstractsExpression and downregulation of WNT signaling pathway genes in rhesus monkey oocytes and embryosMOLECULAR REPRODUCTION & DEVELOPMENT, Issue 6 2006Ping Zheng Abstract Mammalian WNT genes encode secreted glycoproteins that are conserved homologues of the Drosophila Wingless gene, which plays a crucial role in Drosophila development. Recently, WNT pathway signaling has been implicated in ovarian development, oogenesis, and early development. We sought to evaluate whether these genes may contribute to the formation of healthy human oocytes or embryos, and whether the expression of these genes could provide informative markers of human oocyte and embryo quality. To do this, we employed the primate embryo gene expression resource (PREGER; www.preger.org) to examine expression of mRNAs encoding 38 components of the WNT signaling pathway in rhesus monkey oocytes and embryos as a nonhuman primate model. We observed considerable conservation between rhesus monkey and mouse of expression of WNT, FZD, and effector gene mRNAs, and a generalized downregulation of genes encoding key components of the WNT signaling pathway during preimplantation development. Our results support a role for WNT signaling during oocyte growth or maturation, but not during preimplantation development. Additionally, we observed differences between in vitro cultured and in vivo developing blastocysts, indicating possible effects of culture on WNT signaling during the peri-implantation period. Mol. Reprod. Dev. © 2006 Wiley-Liss, Inc. [source] Target Gene Activation of the Wnt Signaling Pathway in Nuclear ,-Catenin Accumulating Cells of Adamantinomatous CraniopharyngiomasBRAIN PATHOLOGY, Issue 3 2009Annett Hölsken Abstract Activating ,-catenin (CTNNB1) mutations can be identified in the majority of adamantinomatous craniopharyngiomas (adaCP), suggesting an aberrant Wnt signaling pathway in this histopathologically peculiar tumor entity. However, there is no proven evidence that nuclear translocation of ,-catenin is associated with CTNNB1 mutations and target gene activation. We performed a laser-microdissection-based study comparing ,-catenin accumulating vs. non-accumulating tumor cells. Mutational analysis and gene expression profiling using real-time polymerase chain reaction were conducted in adamantinomatous and papillary tumor specimens. Target gene activation, that is, over-expression of Axin2 could be detected in adaCP, especially in tumor cells with nuclear ,-catenin accumulation. In addition, increased expression of BMP4 was identified in the accumulating cell population, which supports the hypothesis of an oral ectodermal origin. Interestingly, accumulating and non-accumulating tumor cell populations carried CTNNB1 mutations within exon 3. We extended the analysis, therefore, towards genetic regions encoding for membrane linkage and active/passive nuclear transport mechanisms (exon 4 and exon 8,13), but could not detect any alteration. This is the first report demonstrating an association between nuclear ,-catenin accumulation and target gene activation in adaCP. The results confirm the Wnt signaling pathway as molecular basis of the distinct and challenging clinical and morphological phenotype of adaCP. [source] Carboxypeptidase Z (CPZ) Links Thyroid Hormone and Wnt Signaling Pathways in Growth Plate Chondrocytes,JOURNAL OF BONE AND MINERAL RESEARCH, Issue 2 2009Lai Wang Abstract Carboxypeptidase Z (CPZ) removes carboxyl-terminal basic amino acid residues, particularly arginine residues, from proteins. CPZ contains a cysteine-rich domain (CRD) similar to the CRD found in the frizzled family of Wnt receptors. We have previously shown that thyroid hormone regulates terminal differentiation of growth plate chondrocytes through activation of Wnt-4 expression and Wnt/,-catenin signaling. The Wnt-4 protein contains a C-terminal arginine residue and binds to CPZ through the CRD. The objective of this study was to determine whether CPZ modulates Wnt/,-catenin signaling and terminal differentiation of growth plate chondrocytes. Our results show that CPZ and Wnt-4 mRNA are co-expressed throughout growth plate cartilage. In primary pellet cultures of rat growth plate chondrocytes, thyroid hormone increases both Wnt-4 and CPZ expression, as well as CPZ enzymatic activity. Knockdown of either Wnt-4 or CPZ mRNA levels using an RNA interference technique or blocking CPZ enzymatic activity with the carboxypeptidase inhibitor GEMSA reduces the thyroid hormone effect on both alkaline phosphatase activity and Col10a1 mRNA expression. Adenoviral overexpression of CPZ activates Wnt/,-catenin signaling and promotes the terminal differentiation of growth plate cells. Overexpression of CPZ in growth plate chondrocytes also removes the C-terminal arginine residue from a synthetic peptide consisting of the carboxyl-terminal 16 amino acids of the Wnt-4 protein. Removal of the C-terminal arginine residue of Wnt-4 by site-directed mutagenesis enhances the positive effect of Wnt-4 on terminal differentiation. These data indicate that thyroid hormone may regulate terminal differentiation of growth plate chondrocytes in part by modulating Wnt signaling pathways through the induction of CPZ and subsequent CPZ-enhanced activation of Wnt-4. [source] Expression analysis of chick Wnt and frizzled genes and selected inhibitors in early chick patterningDEVELOPMENTAL DYNAMICS, Issue 3 2004Susan C. Chapman Abstract Wnt signaling is an important component in patterning the early embryo and specifically the neural plate. Studies in Xenopus, mouse, and zebrafish have shown that signaling by members of the Wnt family of secreted signaling factors, their Frizzled receptors and several inhibitors (sFRP1, sFRP2, sFRP3/Frzb1, Crescent/Frzb2, Dkk1, and Cerberus) are involved. However, very little is known about the expression of genes in the Wnt signaling pathway during early anterior neural patterning in chick. We have performed an expression analysis at neural plate stages of several Wnts, Frizzled genes, and Wnt signaling pathway inhibitors using in situ hybridization. The gene expression patterns of these markers are extremely dynamic. We have identified two candidate molecules for anterior patterning of the neural plate, Wnt1 and Wnt8b, which are expressed in the rostral ectoderm at these stages. Further functional studies on the roles of these markers are underway. Developmental Dynamics 229:668,676, 2004. © 2004 Wiley-Liss, Inc. [source] The canonical Wnt signaling pathway plays an important role in lymphopoiesis and hematopoiesisEUROPEAN JOURNAL OF IMMUNOLOGY, Issue 7 2008Frank Abstract The evolutionarily conserved canonical Wnt-,-catenin-T cell factor (TCF)/lymphocyte enhancer binding factor (LEF) signaling pathway regulates key checkpoints in the development of various tissues. Therefore, it is not surprising that a large body of gain-of-function and loss-of-function studies implicate Wnt-,-catenin signaling in lymphopoiesis and hematopoiesis. In contrast, recent papers have reported that Mx-Cre-mediated conditional deletion of ,-catenin and/or its homolog ,-catenin (plakoglobin) did not impair hematopoiesis or lymphopoiesis. However, these studies also report that TCF reporter activity remains active in ,-catenin- and ,-catenin-deficient hematopoietic stem cells and all cells derived from these precursors, indicating that the canonical Wnt signaling pathway was not abrogated. Therefore, these studies in fact show that the canonical Wnt signaling pathway is important in hematopoiesis and lymphopoiesis, even though the molecular basis for the induction of the reporter activity is currently unknown. In this perspective, we provide a broad background to the field with a discussion of the available data and create a framework within which the available and future studies may be evaluated. [source] WIF1, an inhibitor of the Wnt pathway, is rearranged in salivary gland tumors,GENES, CHROMOSOMES AND CANCER, Issue 3 2007Lurdes Queimado Chromosome rearrangements involving 12q13-15 are frequent among several tumors, including pleomorphic adenomas. The common molecular target for these aberrations is the HMGA2 gene, but various fusion partners of HMGA2 have been reported in tumors. Here we report the identification of the WNT inhibitory factor 1 (WIF1) gene as a novel HMGA2 fusion partner in a salivary gland pleomorphic adenoma. In normal salivary gland tissue WIF1 is expressed at a high level and HMGA2 is not expressed. However, in the pleomorphic adenoma expressing the HMGA2/WIF1 fusion transcript, we observed re-expression of HMGA2 wild-type transcripts and very low levels of WIF1 expression. These data suggest a possible synergistic effect between upregulation of HMGA2 and downregulation of WIF1. We screened 13 additional benign and malignant salivary gland tumors and detected WIF1 rearrangement in one out of two carcinomas ex-pleomorphic adenoma analyzed. In this malignant tumor, the rearrangement of one WIF1 allele coexists with loss of the other allele, a classic signature of a tumor suppressor gene. WIF1 is an antagonist of the Wnt signaling pathway, which plays a critical role in human cancer. In transgenic mouse models, Wnt activation leads to a high frequency of benign and malignant salivary gland tumors. To our knowledge, this is the first report suggesting that WIF1 is a recurrent target in human salivary gland oncogenesis and that downregulation of WIF1 plays a role in the development and/or progression of pleomorphic adenomas. © 2006 Wiley-Liss, Inc. [source] Mutations of the Wnt antagonist AXIN2 (Conductin) result in TCF-dependent transcription in medulloblastomasINTERNATIONAL JOURNAL OF CANCER, Issue 2 2007Arend Koch Abstract Medulloblastomas (MBs) represent the most common malignant brain tumors in children. Most MBs develop sporadically in the cerebellum, but their incidence is highly elevated in patients with familial adenomatous polyposis coli. These patients carry germline mutations in the APC tumor suppressor gene. APC is part of a multiprotein complex involved in the Wnt signaling pathway that controls the stability of ,-catenin, the central effector in this cascade. Previous genetic studies in MBs have identified mutations in genes coding for ,-catenin and its partners, APC and AXIN1, which cause activation of Wnt signaling. The pathway is negatively controlled by the tumor suppressor AXIN2 (Conductin), a scaffold protein of this signaling complex. To investigate whether alterations in AXIN2 may also be involved in the pathogenesis of sporadic MBs, we performed a mutational screening of the AXIN2 gene in 116 MB biopsy samples and 11 MB cell lines using single-strand conformation polymorphism and sequencing analysis. One MB displayed a somatic, tumor-specific 2 bp insertion in exon 5, leading to carboxy-terminal truncation of the AXIN2 protein. This tumor biopsy showed nuclear accumulation of ,-catenin protein, indicating an activation of Wnt signaling. In 2 further MB biopsies, mutations were identified in exon 5 (Glu408Lys) and exon 8 (Ser738Phe) of the AXIN2 gene, which are due to predicted germline mutations and rare polymorphisms. mRNA expression analysis in 22 MBs revealed reduced expression of AXIN2 mRNA compared to 8 fetal cerebellar tissues. Promoter hypermethylation could be ruled out as a major cause for transcriptional silencing by bisulfite sequencing. To study the functional role of AXIN2 in MBs, wild-type AXIN2 was overexpressed in MB cell lines in which the Wnt signaling pathway was activated by Wnt-3a. In this assay, AXIN2 inhibited Wnt signaling demonstrated in luciferase reporter assays. In contrast, overexpression of mutated AXIN2 with a deleted C-terminal DIX-domain resulted in an activation of the Wnt signaling pathway. These findings indicate that mutations of AXIN2 can lead to an oncogenic activation of the Wnt pathway in MBs. © 2007 Wiley-Liss, Inc. [source] Wnt signaling in hematopoiesis: Crucial factors for self-renewal, proliferation, and cell fate decisionsJOURNAL OF CELLULAR BIOCHEMISTRY, Issue 5 2010Frank J.T. Staal Abstract A large number of studies from many different laboratories have implicated the Wnt signaling pathway in regulation of hematopoiesis. However, different inducible gain- and loss-of-function approaches yielded controversial and some times contradictory results. In this prospect we will review the current ideas on Wnt signaling in hematopoiesis and early lymphopoiesis. Reviewing this large body of knowledge let us to hypothesize that different levels of activation of the pathway, dosages of Wnt signaling required and the interference by other signals in the context of Wnt activation collectively explain these controversies. Besides differences in dosage, differences in biological function of Wnt proteins in various blood cell types also is a major factor to take into account. Our own work has shown that while in the thymus Wnt signaling provides cytokine-like, proliferative stimuli to developing thymocytes, canonical Wnt signaling in HSC regulates cell fate decisions, in particular self-renewal versus differentiation. J. Cell. Biochem. 109: 844,849, 2010. © 2010 Wiley-Liss, Inc. [source] ,-Catenin signaling in biological control and cancerJOURNAL OF CELLULAR BIOCHEMISTRY, Issue 4 2007Nancy Gavert Abstract A coordinated integration of cell,cell adhesion and the control of gene expression is essential for the development of multicellular, differentiated organisms. ,-Catenin fulfils important regulatory functions in both cell,cell adhesion by linking cadherin adhesion receptors to the cytoskeleton, and also as a key element in the Wnt signaling pathway where it acts as cotranscriptional activator of target genes in the cell nucleus. Wnt signaling is involved in numerous aspects of embryonic development and in the control of tissue self-renewal in a variety of adult tissues. Hyperactivation of Wnt signaling, mostly by affecting ,-catenin functions, is a hallmark of colon cancer and of many other human cancers. In this prospect, we discuss studies pointing to the molecular mechanisms that govern the integration between cell,cell adhesion and gene expression, as reflected in the switches between these two functions of ,-catenin in colon cancer cells. J. Cell. Biochem. 102: 820,828, 2007. © 2007 Wiley-Liss, Inc. [source] Calcium/calmodulin-dependent protein kinase type IV is a target gene of the Wnt/,-catenin signaling pathway,JOURNAL OF CELLULAR PHYSIOLOGY, Issue 3 2009Macarena S. Arrázola Calcium/calmodulin-dependent protein kinase IV (CaMKIV) plays a key role in the regulation of calcium-dependent gene expression. The expression of CaMKIV and the activation of CREB regulated genes are involved in memory and neuronal survival. We report here that: (a) a bioinformatic analysis of 15,476 promoters of the human genome predicted several Wnt target genes, being CaMKIV a very interesting candidate; (b) CaMKIV promoter contains TCF/LEF transcription motifs similar to those present in Wnt target genes; (c) biochemical studies indicate that lithium and the canonical ligand Wnt-3a induce CaMKIV mRNA and protein expression levels in rat hippocampal neurons as well as CaMKIV promoter activity; (d) treatment of hippocampal neurons with Wnt-3a increases the binding of ,-catenin to the CaMKIV promoter: (e) In vivo activation of the Wnt signaling improve spatial memory impairment and restores the expression of CaMKIV in a mice double transgenic model for Alzheimer's disease which shows decreased levels of the kinase. We conclude that CaMKIV is regulated by the Wnt signaling pathway and that its expression could play a role in the neuroprotective function of the Wnt signaling against the Alzheimer's amyloid peptide. J. Cell. Physiol. 221: 658,667, 2009. © 2009 Wiley-Liss, Inc. [source] Frizzled-1 is involved in the neuroprotective effect of Wnt3a against A, oligomersJOURNAL OF CELLULAR PHYSIOLOGY, Issue 1 2008Marcelo A. Chacón The activation of the canonical Wnt signaling pathway protects hippocampal neurons against the toxicity of Alzheimer's amyloid-,-peptide (A,), however, the role played by the Wnt receptors Frizzleds, has not been studied. We report here that Frizzled-1 mediates the activation of the canonical Wnt/,-catenin pathway by Wnt3a in PC12 cells. In addition, the protective effect of Wnt3a against the toxicity of A, oligomers was modulated by Frizzled-1 expression levels in both PC12 cells and hippocampal neurons. Over-expression of Frizzled-1 significantly increased cell survival induced by Wnt3a and diminished caspase-3 activation, while knocking-down Frizzled-1 expression by antisense oligonucleotides decreased the Wnt3a protection. Over-expression of wild-type ,-catenin, but not a transcriptionally inactive mutated version, prevented the toxicity of A, suggesting that the transcription of Wnt target genes may be involved in these events. This was confirmed by co-transfecting both Frizzled-1 and the inactive form of ,-catenin, which does not elicited protection levels similar to those showed with endogenous ,-catenin. Our results indicate that Wnt3a protects from A,-oligomers toxicity by activating the canonical Wnt signaling pathway through the Frizzled-1 receptor, suggesting a therapeutic potential for this signaling pathway in the treatment of Alzheimer's disease. J. Cell. Physiol. 217: 215,227, 2008. © 2008 Wiley-Liss, Inc. [source] Presenilin 1 mediates retinoic acid-induced differentiation of SH-SY5Y cells through facilitation of Wnt signalingJOURNAL OF NEUROSCIENCE RESEARCH, Issue 2 2003Kengo Uemura Abstract Presenilin 1 interacts with ,-catenin, an essential component of the Wnt signaling pathway. To elucidate the role of presenilin 1-,-catenin interaction in neuronal differentiation, we established SH-SY5Y cells stably expressing wild-type presenilin 1, P117L mutant presenilin 1, which is linked to the early-onset familial form of Alzheimer's disease, and D385A mutant presenilin 1, which has no aspartyl proteinase activity. We demonstrate that SH-SY5Y cells stably expressing D385A mutant presenilin 1 failed to differentiate in response to retinoic acid treatment. Retinoic acid caused an increase in nuclear ,-catenin levels in SH-SY5Y cells, which was followed by an increase in cyclin D1 protein levels. Abnormal cellular accumulation of ,-catenin was observed in D385A mutant transfected cells, whereas nuclear ,-catenin and cellular cyclin D1 levels failed to increase. Conversely, SH-SY5Y cells expressing the P117L mutant differentiated normally and showed increased nuclear ,-catenin and cellular cyclin D1 levels. These findings suggest that neuronal differentiation of SH-SY5Y cells involves the Wnt signaling pathway and that presenilin 1 plays a crucial role in Wnt signal transduction by regulating the nuclear translocation of ,-catenin. © 2003 Wiley-Liss, Inc. [source] Pulsating fluid flow modulates gene expression of proteins involved in Wnt signaling pathways in osteocytesJOURNAL OF ORTHOPAEDIC RESEARCH, Issue 10 2009Ana Santos Abstract Strain-derived flow of interstitial fluid activates signal transduction pathways in osteocytes that regulate bone mechanical adaptation. Wnts are involved in this process, but whether mechanical loading modulates Wnt signaling in osteocytes is unclear. We assessed whether mechanical stimulation by pulsating fluid flow (PFF) leads to functional Wnt production, and whether nitric oxide (NO) is important for activation of the canonical Wnt signaling pathway in MLO-Y4 osteocytes. MC3T3-E1 osteoblasts were studied as a positive control for the MLO-Y4 osteocyte response to mechanical loading. MLO-Y4 osteocytes and MC3T3-E1 osteoblasts were submitted to 1-h PFF (0.7,±,0.3 Pa, 5 Hz), and postincubated (PI) without PFF for 0.5,3 h. Gene expression of proteins related to the Wnt canonical and noncanonical pathways were studied using real-time polymerase chain reaction (PCR). In MLO-Y4 osteocytes, PFF upregulated gene expression of Wnt3a, c-jun, connexin 43, and CD44 at 1,3-h PI. In MC3T3-E1 osteoblasts, PFF downregulated gene expression of Wnt5a and c-jun at 0.5,3-h PI. In MLO-Y4 osteocytes, gene expression of PFF-induced Wnt target genes was suppressed by the Wnt antagonist sFRP4, suggesting that loading activates the Wnt canonical pathway through functional Wnt production. The NO inhibitor L-NAME suppressed the effect of PFF on gene expression of Wnt target genes, suggesting that NO might play a role in PFF-induced Wnt production. The response to PFF differed in MC3T3-E1 osteoblasts. Because Wnt signaling is important for bone mass regulation, osteocytes might orchestrate loading-induced bone remodeling through, among others, Wnts. © 2009 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 27:1280,1287, 2009 [source] Anti-tumor mechanisms of valproate: A novel role for an old drugMEDICINAL RESEARCH REVIEWS, Issue 5 2002Roman A. Blaheta Abstract Valproic acid (VPA, 2-propylpentanoic acid) is an established drug in the long-term therapy of epilepsy. During the past years, it has become evident that VPA is also associated with anti-cancer activity. VPA not only suppresses tumor growth and metastasis, but also induces tumor differentiation in vitro and in vivo. Several modes of action might be relevant for the biological activity of VPA: (1) VPA increases the DNA binding of activating protein-1 (AP-1) transcription factor, and the expression of genes regulated by the extracellular-regulated kinase (ERK)-AP-1 pathway; (2) VPA downregulates protein kinase C (PKC) activity; (3) VPA inhibits glycogen synthase kinase-3, (GSK-3,), a negative regulator of the Wnt signaling pathway; (4) VPA activates the peroxisome proliferator-activated receptors PPAR, and ,; (5) VPA blocks HDAC (histone deacetylase), causing hyperacetylation. The findings elucidate an important role of VPA for cancer therapy. VPA might also be useful as low toxicity agent given over long time periods for chemoprevention and/or for control of residual minimal disease. © 2002 Wiley Periodicals, Inc. Med Res Rev, 22, No. 5, 492,511, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/med.10017 [source] Non-cystic solid-pseudopapillary tumor of the pancreas showing nuclear accumulation and activating gene mutation of ,-cateninPATHOLOGY INTERNATIONAL, Issue 11 2006Isao Nishimori Solid-pseudopapillary tumor (SPT) is an unusual pancreatic neoplasm that is characterized by a mixture of solid and cystic components and a fibrous capsule. Recently, the tumorigenesis of SPT has been reported to be associated with gene mutations of ,-catenin, which is a molecule participating in the Wnt signaling pathway. Reported herein is the case of a 53-year-old woman with SPT. The tumor, approximately 3 cm in diameter in the pancreas body, had a clear margin and central calcification but had neither a cystic component nor fibrous capsule. Several lines of pathological findings in the surgically resected specimen indicated SPT: (i) pseudopapillary proliferation of eosinophilic polygonal cells with oval nuclei; (ii) positive expression of several marker molecules indicating differentiation into acinar and endocrine cells; and (iii) zymogen granule-like structures in the cytoplasm on electron microscopy. Further, the tumor cells had intense nuclear accumulation of ,-catenin and an activating mutation, 34Gly(GGA) to Arg(AGA), in exon 3 of the ,-catenin gene, as previously reported in most SPT. These findings suggest that association of the ,-catenin phenotype with development of the rare phenotype of SPT, a non-cystic and unencapsulated tumor, is unlikely. [source] Involvement of the Wnt signaling pathway in experimental and human osteoarthritis: Prominent role of Wnt-induced signaling protein 1ARTHRITIS & RHEUMATISM, Issue 2 2009Arjen B. Blom Objective Wnt signaling pathway proteins are involved in embryonic development of cartilage and bone, and, interestingly, developmental processes appear to be recapitulated in osteoarthritic (OA) cartilage. The present study was undertaken to characterize the expression pattern of Wnt and Fz genes during experimental OA and to determine the function of selected genes in experimental and human OA. Methods Longitudinal expression analysis was performed in 2 models of OA. Levels of messenger RNA for genes from the Wnt/,-catenin pathway were determined in synovium and cartilage, and the results were validated using immunohistochemistry. Effects of selected genes were assessed in vitro using recombinant protein, and in vivo by adenoviral overexpression. Results Wnt-induced signaling protein 1 (WISP-1) expression was strongly increased in the synovium and cartilage of mice with experimental OA. Wnt-16 and Wnt-2B were also markedly up-regulated during the course of disease. Interestingly, increased WISP-1 expression was also found in human OA cartilage and synovium. Stimulation of macrophages and chondrocytes with recombinant WISP-1 resulted in interleukin-1,independent induction of several matrix metalloproteinases (MMPs) and aggrecanase. Adenoviral overexpression of WISP-1 in murine knee joints induced MMP and aggrecanase expression and resulted in cartilage damage. Conclusion This study included a comprehensive characterization of Wnt and Frizzled gene expression in experimental and human OA articular joint tissue. The data demonstrate, for the first time, that WISP-1 expression is a feature of experimental and human OA and that WISP-1 regulates chondrocyte and macrophage MMP and aggrecanase expression and is capable of inducing articular cartilage damage in models of OA. [source] Increasingly complex: New players enter the Wnt signaling networkBIOESSAYS, Issue 10 2002Petra Pandur Wnt proteins can activate different intracellular signaling cascades in various organisms by interacting with receptors of the Frizzled family. The first identified Wnt signaling pathway, the Wnt/,-catenin pathway, has been studied in much detail and is highly conserved among species. As to non-canonical Wnt pathways, the current situation is more nebulous partly because the intracellular mediators of this pathway are not yet fully understood and, in some cases, even identified. However, there are increasing data that prove the existence of non-canonical Wnt signaling and demonstrate its involvement in different developmental processes. In vertebrates, Wnt-11 and Wnt-5A can activate the Wnt/JNK pathway, which resembles the planar cell polarity pathway in Drosophila. The Wnt/Ca2+ -pathway has only been described in Xenopus and zebrafish so far and it is unclear whether it also exists in other organisms. Two recent papers provide us with new insight into non-canonical Wnt signaling by (1) presenting a new intracellular mediator of non-canonical signaling in Xenopus1 and (2) implicating the existence of an additional non-canonical Wnt signaling pathway in flies.2 BioEssays 24:881,884, 2002. © 2002 Wiley Periodicals, Inc. [source] Target Gene Activation of the Wnt Signaling Pathway in Nuclear ,-Catenin Accumulating Cells of Adamantinomatous CraniopharyngiomasBRAIN PATHOLOGY, Issue 3 2009Annett Hölsken Abstract Activating ,-catenin (CTNNB1) mutations can be identified in the majority of adamantinomatous craniopharyngiomas (adaCP), suggesting an aberrant Wnt signaling pathway in this histopathologically peculiar tumor entity. However, there is no proven evidence that nuclear translocation of ,-catenin is associated with CTNNB1 mutations and target gene activation. We performed a laser-microdissection-based study comparing ,-catenin accumulating vs. non-accumulating tumor cells. Mutational analysis and gene expression profiling using real-time polymerase chain reaction were conducted in adamantinomatous and papillary tumor specimens. Target gene activation, that is, over-expression of Axin2 could be detected in adaCP, especially in tumor cells with nuclear ,-catenin accumulation. In addition, increased expression of BMP4 was identified in the accumulating cell population, which supports the hypothesis of an oral ectodermal origin. Interestingly, accumulating and non-accumulating tumor cell populations carried CTNNB1 mutations within exon 3. We extended the analysis, therefore, towards genetic regions encoding for membrane linkage and active/passive nuclear transport mechanisms (exon 4 and exon 8,13), but could not detect any alteration. This is the first report demonstrating an association between nuclear ,-catenin accumulation and target gene activation in adaCP. The results confirm the Wnt signaling pathway as molecular basis of the distinct and challenging clinical and morphological phenotype of adaCP. [source] Wnt signaling stabilizes the DIXDC1 protein through decreased ubiquitin-dependent degradationCANCER SCIENCE, Issue 3 2010Lei Wang (Cancer Sci 2010; 101: 700,706) Wnt signaling plays key roles in development, cell growth, differentiation, polarity formation, neural development, and carcinogenesis. DIX Domain Containing 1 (DIXDC1), a novel component of the Wnt pathway, was recently cloned. DIXDC1 is the human homolog of Ccd1, a positive regulator of the Wnt signaling pathway during zebrafish neural patterning. Little has been known about DIXDC1 gene expression regulation. In the present study, we showed that the DIXDC1 protein was induced upon Wnt-3a stimulation, whereas the DIXDC1 mRNA level was not significantly increased after Wnt-3a treatment. Positive DIXDC1 staining was detected in colon cancer cells and was colocalized with ,-catenin staining. However, the DIXDC1 mRNA expression decreased in human colon cancer cells compared to the matched normal colon epithelial cells. Our further investigation showed that the DIXDC1 protein was degraded through the proteasome pathway, and the activation of canonical Wnt signaling decreased the ubiquitin-dependent degradation of both the ectopic and endogenous DIXDC1 protein. In order to explore the possible mechanism of the ubiquitination of DIXDC1, we found that the phosphorylation of DIXDC1 was inhibited by Wnt-3a. Collectively, these results indicate that canonical Wnt/,-catenin pathway activation might upregulate DIXDC1 through a post-translational mechanism by inhibiting the ubiquitin-mediated degradation of the DIXDC1 protein. [source] Tumor formation by genetic mutations in the components of the Wnt signaling pathwayCANCER SCIENCE, Issue 3 2003Akira Kikuchi The genetics of development and cancer have converged in the identification of intra- and extra-cellular signaling pathways that are aberrantly regulated in cancer, and are also central to embryonic patterning. The Wnt signaling pathway has provided an outstanding example of this. The genes for ,-catenin, ARC, and Axin in the Wnt signaling pathway are often mutated in human cancers. In all such cases, the common denominator is the activation of gene transcription by ,-catenin. The resulting gene expression profile should provide a significant clue to the developmental mechanisms of cancers carrying defects in the Wnt signaling pathway. In this review, the functions of ,-catenin, APC and Axin, and the alterations of the three genes in human cancers are described. (Cancer Sci 2003; 94: 225,229) [source] Carboxypeptidase Z (CPZ) Links Thyroid Hormone and Wnt Signaling Pathways in Growth Plate Chondrocytes,JOURNAL OF BONE AND MINERAL RESEARCH, Issue 2 2009Lai Wang Abstract Carboxypeptidase Z (CPZ) removes carboxyl-terminal basic amino acid residues, particularly arginine residues, from proteins. CPZ contains a cysteine-rich domain (CRD) similar to the CRD found in the frizzled family of Wnt receptors. We have previously shown that thyroid hormone regulates terminal differentiation of growth plate chondrocytes through activation of Wnt-4 expression and Wnt/,-catenin signaling. The Wnt-4 protein contains a C-terminal arginine residue and binds to CPZ through the CRD. The objective of this study was to determine whether CPZ modulates Wnt/,-catenin signaling and terminal differentiation of growth plate chondrocytes. Our results show that CPZ and Wnt-4 mRNA are co-expressed throughout growth plate cartilage. In primary pellet cultures of rat growth plate chondrocytes, thyroid hormone increases both Wnt-4 and CPZ expression, as well as CPZ enzymatic activity. Knockdown of either Wnt-4 or CPZ mRNA levels using an RNA interference technique or blocking CPZ enzymatic activity with the carboxypeptidase inhibitor GEMSA reduces the thyroid hormone effect on both alkaline phosphatase activity and Col10a1 mRNA expression. Adenoviral overexpression of CPZ activates Wnt/,-catenin signaling and promotes the terminal differentiation of growth plate cells. Overexpression of CPZ in growth plate chondrocytes also removes the C-terminal arginine residue from a synthetic peptide consisting of the carboxyl-terminal 16 amino acids of the Wnt-4 protein. Removal of the C-terminal arginine residue of Wnt-4 by site-directed mutagenesis enhances the positive effect of Wnt-4 on terminal differentiation. These data indicate that thyroid hormone may regulate terminal differentiation of growth plate chondrocytes in part by modulating Wnt signaling pathways through the induction of CPZ and subsequent CPZ-enhanced activation of Wnt-4. [source] Pulsating fluid flow modulates gene expression of proteins involved in Wnt signaling pathways in osteocytesJOURNAL OF ORTHOPAEDIC RESEARCH, Issue 10 2009Ana Santos Abstract Strain-derived flow of interstitial fluid activates signal transduction pathways in osteocytes that regulate bone mechanical adaptation. Wnts are involved in this process, but whether mechanical loading modulates Wnt signaling in osteocytes is unclear. We assessed whether mechanical stimulation by pulsating fluid flow (PFF) leads to functional Wnt production, and whether nitric oxide (NO) is important for activation of the canonical Wnt signaling pathway in MLO-Y4 osteocytes. MC3T3-E1 osteoblasts were studied as a positive control for the MLO-Y4 osteocyte response to mechanical loading. MLO-Y4 osteocytes and MC3T3-E1 osteoblasts were submitted to 1-h PFF (0.7,±,0.3 Pa, 5 Hz), and postincubated (PI) without PFF for 0.5,3 h. Gene expression of proteins related to the Wnt canonical and noncanonical pathways were studied using real-time polymerase chain reaction (PCR). In MLO-Y4 osteocytes, PFF upregulated gene expression of Wnt3a, c-jun, connexin 43, and CD44 at 1,3-h PI. In MC3T3-E1 osteoblasts, PFF downregulated gene expression of Wnt5a and c-jun at 0.5,3-h PI. In MLO-Y4 osteocytes, gene expression of PFF-induced Wnt target genes was suppressed by the Wnt antagonist sFRP4, suggesting that loading activates the Wnt canonical pathway through functional Wnt production. The NO inhibitor L-NAME suppressed the effect of PFF on gene expression of Wnt target genes, suggesting that NO might play a role in PFF-induced Wnt production. The response to PFF differed in MC3T3-E1 osteoblasts. Because Wnt signaling is important for bone mass regulation, osteocytes might orchestrate loading-induced bone remodeling through, among others, Wnts. © 2009 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 27:1280,1287, 2009 [source] The molecular basis of oral-facial-digital syndrome, type 1,AMERICAN JOURNAL OF MEDICAL GENETICS, Issue 4 2009Marina Macca Abstract Oral,facial,digital syndrome type 1 (OFDI; OFD1; OMIM 311200) is a rare developmental disorder transmitted as an X-linked dominant condition with embryonic male lethality. OFD1 is characterized by malformation of the oral cavity, face, and digits. Central nervous system (CNS) abnormalities and cystic kidney disease can also be part of this condition. This disorder is due to mutations in the OFD1 gene that encodes a centrosomal protein localized at the basal bodies at the origin of primary cilia. Characterization of in vitro and in vivo models demonstrated that, similarly to what described for other ciliary proteins, Ofd1 inactivation is associated to defective sonic hedgehog (Shh) and canonical Wnt signaling pathways. Functional studies have demonstrated that OFD1 has a crucial role in the biology of primary cilia thus ascribing this pleiotropic disease to the growing number of disorders associated to dysfunction of primary cilia. OFD1 shares phenotypic similarities with this latter group of disorders, such as cystic kidneys, skeletal, and CNS abnormalities. Future studies will address whether all clinical manifestations of these diseases can be entirely explained by cilia dysfunction or may also be due to direct roles of the proteins involved. © 2009 Wiley-Liss, Inc. [source] | |||||||||||||||||||||||||