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Akihiko Shimono - One of the best experts on this subject based on the ideXlab platform.
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sfrp1 and SFRP2 are not involved in wnt β catenin signal silencing during lens induction but are required for maintenance of wnt β catenin signaling in lens epithelial cells
Developmental Biology, 2013Co-Authors: Yuki Sugiyama, Frank J. Lovicu, Elizabeth J. Shelley, Li Wen, R.j. W. Stump, Akihiko Shimono, John W. McavoyAbstract:During eye lens development, regulation of Wnt/β-catenin signaling is critical for two major processes: initially it must be silent in the lens placode for lens development to proceed, but subsequently it is required for maintenance of the lens epithelium. It is not known how these different phases of Wnt/β-catenin activity/inactivity are regulated. Secreted frizzled related protein-2 (SFRP2), a putative Wnt-Fz antagonist, is expressed in lens placode and in lens epithelial cells and has been put forward as a candidate for regional Wnt/β-catenin pathway regulation. Here we show its closely-related isoform, Sfrp1, has a complimentary pattern of expression in the lens, being absent from the placode and epithelium but expressed in the fibers. As mice with single knockouts of Sfrp1 or SFRP2 had no defects in lens formation, we examined lenses of Sfrp1 and SFRP2 double knockout (DKO) mice and showed that they formed lens placode and subsequent lens structures. Consistent with this we did not observe ectopic TCF/Lef activity in lens placode of DKOs. This indicates that Sfrp1 and SFRP2 individually, or together, do not constitute the putative negative regulator that blocks Wnt/β-catenin signaling during lens induction. In contrast, Sfrp1 and SFRP2 appear to have a positive regulatory function because Wnt/β-catenin signaling in lens epithelial cells was reduced in Sfrp1 and SFRP2 DKO mice. Lenses that formed in DKO mice were smaller than controls and exhibited a deficient epithelium. Thus Sfrps play a role in lens development, at least in part, by regulating aspects of Wnt/β-catenin signaling in lens epithelial cells.
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Sfrp1 and SFRP2 are not involved in Wnt/β-catenin signal silencing during lens induction but are required for maintenance of Wnt/β-catenin signaling in lens epithelial cells.
Developmental biology, 2013Co-Authors: Yuki Sugiyama, Frank J. Lovicu, Elizabeth J. Shelley, Li Wen, R.j. W. Stump, Akihiko Shimono, John W. McavoyAbstract:During eye lens development, regulation of Wnt/β-catenin signaling is critical for two major processes: initially it must be silent in the lens placode for lens development to proceed, but subsequently it is required for maintenance of the lens epithelium. It is not known how these different phases of Wnt/β-catenin activity/inactivity are regulated. Secreted frizzled related protein-2 (SFRP2), a putative Wnt-Fz antagonist, is expressed in lens placode and in lens epithelial cells and has been put forward as a candidate for regional Wnt/β-catenin pathway regulation. Here we show its closely-related isoform, Sfrp1, has a complimentary pattern of expression in the lens, being absent from the placode and epithelium but expressed in the fibers. As mice with single knockouts of Sfrp1 or SFRP2 had no defects in lens formation, we examined lenses of Sfrp1 and SFRP2 double knockout (DKO) mice and showed that they formed lens placode and subsequent lens structures. Consistent with this we did not observe ectopic TCF/Lef activity in lens placode of DKOs. This indicates that Sfrp1 and SFRP2 individually, or together, do not constitute the putative negative regulator that blocks Wnt/β-catenin signaling during lens induction. In contrast, Sfrp1 and SFRP2 appear to have a positive regulatory function because Wnt/β-catenin signaling in lens epithelial cells was reduced in Sfrp1 and SFRP2 DKO mice. Lenses that formed in DKO mice were smaller than controls and exhibited a deficient epithelium. Thus Sfrps play a role in lens development, at least in part, by regulating aspects of Wnt/β-catenin signaling in lens epithelial cells.
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SFRP1 and SFRP2 Dose-Dependently Regulate Midbrain Dopamine Neuron Development In Vivo and in Embryonic Stem Cells†‡§
Stem cells (Dayton Ohio), 2012Co-Authors: Julianna Kele, Emma R. Andersson, J. Carlos Villaescusa, Lukas Cajanek, Clare L. Parish, Sonia Bonilla, Enrique M. Toledo, Vitezslav Bryja, Jeffrey S. Rubin, Akihiko ShimonoAbstract:Secreted Frizzled related proteins (sFRPs) are a family of proteins that modulate Wnt signaling, which in turn regulates multiple aspects of ventral midbrain (VM) and dopamine (DA) neuron development. However, it is not known which Wnt signaling branch and what aspects of midbrain DA neuron development are regulated by sFRPs. Here, we show that sFRP1 and SFRP2 activate the Wnt/planar-cell-polarity/Rac1 pathway in DA cells. In the developing VM, sFRP1 and SFRP2 are expressed at low levels, and sFRP1-/- or SFRP2-/- mice had no detectable phenotype. However, compound sFRP1-/-;SFRP2-/- mutants revealed a Wnt/PCP phenotype similar to that previously described for Wnt5a-/- mice. This included an anteroposterior shortening of the VM, a lateral expansion of the Shh domain and DA lineage markers (Lmx1a and Th), as well as an accumulation of Nurr1+ precursors in the VM. In vitro experiments showed that, while very high concentrations of SFRP1 had a negative effect on cell survival, low/medium concentrations of sFRP1 or SFRP2 promoted the DA differentiation of progenitors derived from primary VM cultures or mouse embryonic stem cells (ESCs), mimicking the effects of Wnt5a. We thus conclude that the main function of sFRP1 and SFRP2 is to enhance Wnt/PCP signaling in DA cells and to regulate Wnt/PCP-dependent functions in midbrain development. Moreover, we suggest that low-medium concentrations of sFRPs may be used to enhance the DA differentiation of ESCs and improve their therapeutic application.
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Sfrp Controls Apicobasal Polarity and Oriented Cell Division in Developing Gut Epithelium
PLoS genetics, 2009Co-Authors: Makoto Matsuyama, Shinichi Aizawa, Akihiko ShimonoAbstract:Epithelial tubular morphogenesis leading to alteration of organ shape has important physiological consequences. However, little is known regarding the mechanisms that govern epithelial tube morphogenesis. Here, we show that inactivation of Sfrp1 and SFRP2 leads to reduction in fore-stomach length in mouse embryos, which is enhanced in the presence of the Sfrp5 mutation. In the mono-cell layer of fore-stomach epithelium, cell division is normally oriented along the cephalocaudal axis; in contrast, orientation diverges in the Sfrps-deficient fore-stomach. Cell growth and apoptosis are not affected in the Sfrps-deficient fore-stomach epithelium. Similarly, cell division orientation in fore-stomach epithelium diverges as a result of inactivation of either Stbm/Vangl2, an Fz/PCP component, or Wnt5a. These observations indicate that the oriented cell division, which is controlled by the Fz/PCP pathway, is one of essential components in fore-stomach morphogenesis. Additionally, the small intestine epithelium of Sfrps compound mutants fails to maintain proper apicobasal polarity; the defect was also observed in Wnt5a-inactivated small intestine. In relation to these findings, Sfrp1 physically interacts with Wnt5a and inhibits Wnt5a signaling. We propose that Sfrp regulation of Wnt5a signaling controls oriented cell division and apicobasal polarity in the epithelium of developing gut.
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Sfrp1 and SFRP2 are required for normal male sexual development in mice.
Developmental biology, 2008Co-Authors: Nick Warr, Wataru Satoh, Pam Siggers, Debora Bogani, Rachel Brixey, Laura M. Pastorelli, Laura L. Yates, Charlotte H. Dean, Sara Wells, Akihiko ShimonoAbstract:Abstract Secreted frizzled-related proteins (Sfrps) are antagonists of WNT signalling implicated in a variety of biological processes. However, there are no reports of a direct role for Sfrps in embryonic organogenesis in mammals. Using in vivo loss-of-function studies we report here for the first time a redundant role for Sfrp1 and SFRP2 in embryonic sexual development of the mouse. At 16.5 dpc, male embryos lacking both genes exhibit multiple defects in gonad morphology, reproductive tract maturation and gonad positioning. Abnormal positioning of the testis appears to be due to failed gubernaculum development and an unusually close association between the cranial end of the reproductive tract and the kidney. The testes of double homozygotes are smaller than controls, contain fewer cords from the earliest stages, but still express Insl3, which encodes the hormone required for gubernacular masculinisation. Lgr8, which encodes the Insl3 receptor, is also expressed in the mutant gubernaculum, suggesting that Sfrp1/SFRP2 signalling is not required for expression of the ligand or receptor that controls transabdominal testicular descent. Similarities between the abnormalities of embryonic sexual development in Sfrp1−/− SFRP2−/− embryos with those exhibited by the Looptail and Wnt5a mutants suggest that disrupted non-canonical Wnt signalling may cause these defects.
John W. Mcavoy - One of the best experts on this subject based on the ideXlab platform.
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sfrp1 and SFRP2 are not involved in wnt β catenin signal silencing during lens induction but are required for maintenance of wnt β catenin signaling in lens epithelial cells
Developmental Biology, 2013Co-Authors: Yuki Sugiyama, Frank J. Lovicu, Elizabeth J. Shelley, Li Wen, R.j. W. Stump, Akihiko Shimono, John W. McavoyAbstract:During eye lens development, regulation of Wnt/β-catenin signaling is critical for two major processes: initially it must be silent in the lens placode for lens development to proceed, but subsequently it is required for maintenance of the lens epithelium. It is not known how these different phases of Wnt/β-catenin activity/inactivity are regulated. Secreted frizzled related protein-2 (SFRP2), a putative Wnt-Fz antagonist, is expressed in lens placode and in lens epithelial cells and has been put forward as a candidate for regional Wnt/β-catenin pathway regulation. Here we show its closely-related isoform, Sfrp1, has a complimentary pattern of expression in the lens, being absent from the placode and epithelium but expressed in the fibers. As mice with single knockouts of Sfrp1 or SFRP2 had no defects in lens formation, we examined lenses of Sfrp1 and SFRP2 double knockout (DKO) mice and showed that they formed lens placode and subsequent lens structures. Consistent with this we did not observe ectopic TCF/Lef activity in lens placode of DKOs. This indicates that Sfrp1 and SFRP2 individually, or together, do not constitute the putative negative regulator that blocks Wnt/β-catenin signaling during lens induction. In contrast, Sfrp1 and SFRP2 appear to have a positive regulatory function because Wnt/β-catenin signaling in lens epithelial cells was reduced in Sfrp1 and SFRP2 DKO mice. Lenses that formed in DKO mice were smaller than controls and exhibited a deficient epithelium. Thus Sfrps play a role in lens development, at least in part, by regulating aspects of Wnt/β-catenin signaling in lens epithelial cells.
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Sfrp1 and SFRP2 are not involved in Wnt/β-catenin signal silencing during lens induction but are required for maintenance of Wnt/β-catenin signaling in lens epithelial cells.
Developmental biology, 2013Co-Authors: Yuki Sugiyama, Frank J. Lovicu, Elizabeth J. Shelley, Li Wen, R.j. W. Stump, Akihiko Shimono, John W. McavoyAbstract:During eye lens development, regulation of Wnt/β-catenin signaling is critical for two major processes: initially it must be silent in the lens placode for lens development to proceed, but subsequently it is required for maintenance of the lens epithelium. It is not known how these different phases of Wnt/β-catenin activity/inactivity are regulated. Secreted frizzled related protein-2 (SFRP2), a putative Wnt-Fz antagonist, is expressed in lens placode and in lens epithelial cells and has been put forward as a candidate for regional Wnt/β-catenin pathway regulation. Here we show its closely-related isoform, Sfrp1, has a complimentary pattern of expression in the lens, being absent from the placode and epithelium but expressed in the fibers. As mice with single knockouts of Sfrp1 or SFRP2 had no defects in lens formation, we examined lenses of Sfrp1 and SFRP2 double knockout (DKO) mice and showed that they formed lens placode and subsequent lens structures. Consistent with this we did not observe ectopic TCF/Lef activity in lens placode of DKOs. This indicates that Sfrp1 and SFRP2 individually, or together, do not constitute the putative negative regulator that blocks Wnt/β-catenin signaling during lens induction. In contrast, Sfrp1 and SFRP2 appear to have a positive regulatory function because Wnt/β-catenin signaling in lens epithelial cells was reduced in Sfrp1 and SFRP2 DKO mice. Lenses that formed in DKO mice were smaller than controls and exhibited a deficient epithelium. Thus Sfrps play a role in lens development, at least in part, by regulating aspects of Wnt/β-catenin signaling in lens epithelial cells.
Pampee P Young - One of the best experts on this subject based on the ideXlab platform.
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the wnt modulator SFRP2 enhances mesenchymal stem cell engraftment granulation tissue formation and myocardial repair
Proceedings of the National Academy of Sciences of the United States of America, 2008Co-Authors: Maria P Alfaro, Matthew Pagni, Alicia Vince, James Atkinso, Jeffrey N Rottma, Etha Lee, Michael Hill, Jeffrey M Davidso, Justi M M Cates, Pampee P YoungAbstract:Cell-based therapies, using multipotent mesenchymal stem cells (MSCs) for organ regeneration, are being pursued for cardiac disease, orthopedic injuries and biomaterial fabrication. The molecular pathways that regulate MSC-mediated regeneration or enhance their therapeutic efficacy are, however, poorly understood. We compared MSCs isolated from MRL/MpJ mice, known to demonstrate enhanced regenerative capacity, to those from C57BL/6 (WT) mice. Compared with WT-MSCs, MRL-MSCs demonstrated increased proliferation, in vivo engraftment, experimental granulation tissue reconstitution, and tissue vascularity in a murine model of repair stimulation. The MRL-MSCs also reduced infarct size and improved function in a murine myocardial infarct model compared with WT-MSCs. Genomic and functional analysis indicated a downregulation of the canonical Wnt pathway in MRL-MSCs characterized by significant up-regulation of specific secreted frizzled-related proteins (sFRPs). Specific knockdown of SFRP2 by shRNA in MRL-MSCs decreased their proliferation and their engraftment in and the vascular density of MRL-MSC-generated experimental granulation tissue. These results led us to generate WT-MSCs overexpressing SFRP2 (SFRP2-MSCs) by retroviral transduction. SFRP2-MSCs maintained their ability for multilineage differentiation in vitro and, when implanted in vivo, recapitulated the MRL phenotype. Peri-infarct intramyocardial injection of SFRP2-MSCs resulted in enhanced engraftment, vascular density, reduced infarct size, and increased cardiac function after myocardial injury in mice. These findings implicate SFRP2 as a key molecule for the biogenesis of a superior regenerative phenotype in MSCs.
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The Wnt Inhibitor SFRP2 Enhances Mesenchymal Stem Cell Engraftment, Granulation Tissue Formation and Myocardial Repair
Blood, 2008Co-Authors: Maria P Alfaro, Matthew Pagni, Alicia Vincent, Michael F. Hill, Ethan Lee, Pampee P YoungAbstract:Cell-based therapies using bone marrow-derived mesenchymal stem cells (MSCs) for organ regeneration are being pursued for cardiac disease, orthopedic injuries and biomaterial fabrication. The molecular pathways that regulate MSC-mediated regeneration or enhance their therapeutic efficacy are, however, poorly understood. In an attempt to elucidate a way to strengthen the regenerative potential of MSCs, preliminary studies in our lab were performed comparing MSCs isolated from wildtype and regenerative mouse strains. The MRL/MpJ mouse has been described as a “super healer” mouse that is able to repair soft tissue with minimal scaring. MSCs were isolated from the MRL/MpJ mouse (MRL-MSCs) and from C57/Bl6 mice (WT-MSCs) and their differing qualities assessed. Compared to WT-MSCs, MRL-MSCs demonstrated increased proliferation in vitro . We utilized a Poly-vinyl alcohol (PVA) sponge model of repair stimulation to assess their capacity to generate wound repair tissue. We observed that the MRL-MSCs demonstrated increased in vivo engraftment, experimental granulation tissue reconstitution, and tissue vascularity. The MRL-MSCs also reduced infarct size and improved cardiac function as compared to WT-MSCs in a murine acute myocardial infarct model. Genomic and functional analyses indicated a downregulation of the canonical Wnt pathway in MRL-MSCs characterized specifically by upregulation of secreted frizzled related proteins (sFRPs). In vitro proliferation studies confirmed that recombinant SFRP2 mediated enhanced proliferation of both mouse and human MSCs. Based on these observations, we hypothesized that SFRP2 served an important role in MSC-mediated repair and regeneration. We generated WT-MSCs overexpressing SFRP2 (SFRP2-MSCs) by retroviral transduction to test this hypothesis. SFRP2-MSCs maintained their ability for multilineage differentiation in vitro and proliferated faster than the vector only control MSCs (GFP-MSCs). When implanted in vivo in the PVA sponge model, the SFRP2-MSCs recapitulated the MRL phenotype by mediating greater, more vascularized granulation tissue. Moreover, periinfarct intramyocardial injection of SFRP2-MSCs resulted in reduced infarct size, favorable remodeling and better preserved left ventricular function following acute myocardial infarct in mice. These findings implicate SFRP2 as a key molecule for the biogenesis of a superior regenerative phenotype of MSCs.
Edgar Dahl - One of the best experts on this subject based on the ideXlab platform.
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promoter hypermethylation of the tumor suppressor genes itih5 dkk3 and rassf1a as novel biomarkers for blood based breast cancer screening
Breast Cancer Research, 2013Co-Authors: Vera Kloten, Jürgen Veeck, Arndt Hartmann, Ruth Knüchel, Birte Becker, Kirsten Winner, Michael G Schrauder, Peter A Fasching, Tobias Anzeneder, Edgar DahlAbstract:Introduction: For early detection of breast cancer, the development of robust blood-based biomarkers that accurately reflect the host tumor is mandatory. We investigated DNA methylation in circulating free DNA (cfDNA) from blood of breast cancer patients and matched controls to establish a biomarker panel potentially useful for early detection of breast cancer. Methods: We examined promoter methylation of seven putative tumor-suppressor genes (SFRP1, SFRP2, SFRP5, ITIH5, WIF1, DKK3, and RASSF1A) in cfDNA extracted from serum. Clinical performance was first determined in a test set (n = 261 sera). In an independent validation set (n = 343 sera), we validated the most promising genes for further use in early breast cancer detection. Sera from 59 benign breast disease and 58 colon cancer patients were included for additional specificity testing. Results: Based on the test set, we determined ITIH5 and DKK3 promoter methylation as candidate biomarkers with the best sensitivity and specificity. In both the test and validation set combined, ITIH5 and DKK3 methylation achieved 41% sensitivity with a specificity of 93% and 100% in healthy and benign disease controls, respectively. Combination of these genes with RASSF1A methylation increased the sensitivity to 67% with a specificity of 69% and 82% in healthy controls and benign disease controls, respectively. Conclusions: Tumor-specific methylation of the three-gene panel (ITIH5, DKK3, and RASSF1A) might be a valuable biomarker for the early detection of breast cancer.
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Promoter hypermethylation of the SFRP2 gene is a high-frequent alteration and tumor-specific epigenetic marker in human breast cancer
Molecular cancer, 2008Co-Authors: Jürgen Veeck, Erik Noetzel, Nuran Bektas, Edgar Jost, Arndt Hartmann, Ruth Knüchel, Edgar DahlAbstract:Background We have previously reported that expression of the Wnt antagonist genes SFRP1 and SFRP5 is frequently silenced by promoter hypermethylation in breast cancer. SFRP2 is a further Wnt inhibitor whose expression was recently found being downregulated in various malignancies. Here we investigated whether SFRP2 is also implicated in human breast cancer, and if so whether SFRP2 promoter methylation might serve as a potential tumor biomarker.
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epigenetic inactivation of the secreted frizzled related protein 5 sfrp5 gene in human breast cancer is associated with unfavorable prognosis
Carcinogenesis, 2008Co-Authors: Jürgen Veeck, Erik Noetzel, Arndt Hartmann, Ruth Knüchel, Cordelia Geisler, Sevim Alkaya, Edgar DahlAbstract:Disruption of the Wnt pathway is thought to be crucial in the development of human cancer. Pathway inhibitory members of the secreted frizzled-related protein (SFRP) family were found to be downregulated due to epigenetic inactivation in various malignancies. To date, only SFRP1 has been studied in human breast cancer and we questioned whether other SFRP genes may be implicated in the pathogenesis of this disease as well. An initial real-time polymerase chain reaction analysis of SFRP5 expression in normal human tissues (n = 9) revealed weak expression in most tissues, including breast. Malignant mammary cell lines showed further SFRP5 expression loss in five of six cases. Consistently, in matched pairs of primary breast tumor/normal breast tissue, this downregulation (>5-fold) could be confirmed (n = 8/13; 62%). We identified promoter methylation as the predominant mechanism of SFRP5 gene silencing since SFRP5 promoter methylation correlated significantly with loss of SFRP5 expression in cell lines (P = 0.040) and primary tumors (P = 0.003). Moreover, cancerous cell lines re-expressed SFRP5 messenger RNA following treatment with DNA-demethylating drugs. Of 168 primary breast carcinomas, 73% harbored a methylated SFRP5 promoter, whereas 27% were unaffected by epigenetic alteration. Most interestingly, SFRP5 methylation was associated with reduced overall survival (OS) (P = 0.045) and was an independent risk factor affecting OS in a multivariate Cox proportional hazard model (hazard ratio): 4.55; 95% confidence interval: 1.01-20.56; P = 0.049). In conclusion, SFRP5 is a target of epigenetic inactivation in human breast cancer, supporting the hypothesis of its role as tumor suppressor gene. SFRP5 methylation may be a novel DNA-based biomarker potentially useful in clinical breast cancer management.
Jeffrey S. Rubin - One of the best experts on this subject based on the ideXlab platform.
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secreted frizzled related protein potentiation versus inhibition of wnt3a β catenin signaling
Cellular Signalling, 2014Co-Authors: Charles P Xavier, Maria Melikova, Yoshiro Chuman, Aykut Uren, Bolormaa Baljinnyam, Jeffrey S. RubinAbstract:Wnt signaling regulates a variety of cellular processes during embryonic development and in the adult. Many of these activities are mediated by the Frizzled family of seven-pass transmembrane receptors, which bind Wnts via a conserved cysteine-rich domain (CRD). Secreted Frizzled-related proteins (sFRPs) contain an amino-terminal, Frizzled-like CRD and a carboxyl-terminal, heparin-binding netrin-like domain. Previous studies identified sFRPs as soluble Wnt antagonists that bind directly to Wnts and prevent their interaction with Frizzleds. However, subsequent observations suggested that sFRPs and Frizzleds form homodimers and heterodimers via their respective CRDs, and that sFRPs can stimulate signal transduction. Here, we present evidence that sFRP1 either inhibits or enhances signaling in the Wnt3a/β-catenin pathway, depending on its concentration and the cellular context. Nanomolar concentrations of sFRP1 increased Wnt3a signaling, while higher concentrations blocked it in HEK293 cells expressing a SuperTopFlash reporter. sFRP1 primarily augmented Wnt3a/β-catenin signaling in C57MG cells, but it behaved as an antagonist in L929 fibroblasts. sFRP1 enhanced reporter activity in L cells that were engineered to stably express Frizzled 5, though not Frizzled 2. This implied that the Frizzled expression pattern could determine the response to sFRP1. Similar results were obtained with SFRP2 in HEK293, C57MG and L cell reporter assays. CRDsFRP1 mimicked the potentiating effect of sFRP1 in multiple settings, contradicting initial expectations that this domain would inhibit Wnt signaling. Moreover, CRDsFRP1 showed little avidity for Wnt3a compared to sFRP1, implying that the mechanism for potentiation by CRDsFRP1 probably does not require an interaction with Wnt protein. Together, these findings demonstrate that sFRPs can either promote or suppress Wnt/β-catenin signaling, depending on cellular context, concentration and most likely the expression pattern of Fzd receptors.
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SFRP1 and SFRP2 Dose-Dependently Regulate Midbrain Dopamine Neuron Development In Vivo and in Embryonic Stem Cells†‡§
Stem cells (Dayton Ohio), 2012Co-Authors: Julianna Kele, Emma R. Andersson, J. Carlos Villaescusa, Lukas Cajanek, Clare L. Parish, Sonia Bonilla, Enrique M. Toledo, Vitezslav Bryja, Jeffrey S. Rubin, Akihiko ShimonoAbstract:Secreted Frizzled related proteins (sFRPs) are a family of proteins that modulate Wnt signaling, which in turn regulates multiple aspects of ventral midbrain (VM) and dopamine (DA) neuron development. However, it is not known which Wnt signaling branch and what aspects of midbrain DA neuron development are regulated by sFRPs. Here, we show that sFRP1 and SFRP2 activate the Wnt/planar-cell-polarity/Rac1 pathway in DA cells. In the developing VM, sFRP1 and SFRP2 are expressed at low levels, and sFRP1-/- or SFRP2-/- mice had no detectable phenotype. However, compound sFRP1-/-;SFRP2-/- mutants revealed a Wnt/PCP phenotype similar to that previously described for Wnt5a-/- mice. This included an anteroposterior shortening of the VM, a lateral expansion of the Shh domain and DA lineage markers (Lmx1a and Th), as well as an accumulation of Nurr1+ precursors in the VM. In vitro experiments showed that, while very high concentrations of SFRP1 had a negative effect on cell survival, low/medium concentrations of sFRP1 or SFRP2 promoted the DA differentiation of progenitors derived from primary VM cultures or mouse embryonic stem cells (ESCs), mimicking the effects of Wnt5a. We thus conclude that the main function of sFRP1 and SFRP2 is to enhance Wnt/PCP signaling in DA cells and to regulate Wnt/PCP-dependent functions in midbrain development. Moreover, we suggest that low-medium concentrations of sFRPs may be used to enhance the DA differentiation of ESCs and improve their therapeutic application.
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increased expression of the wnt antagonist sfrp 1 in glaucoma elevates intraocular pressure
Journal of Clinical Investigation, 2008Co-Authors: Wanheng Wang, Jeffrey S. Rubin, Loretta Graves Mcnatt, Iokhou Pang, Cameron J Millar, Peggy E Hellberg, Mark H Hellberg, Thomas H Steely, John H Fingert, Val C SheffieldAbstract:Elevated intraocular pressure (IOP) is the principal risk factor for glaucoma and results from excessive impedance of the fluid outflow from the eye. This abnormality likely originates from outflow pathway tissues such as the trabecular meshwork (TM), but the associated molecular etiology is poorly understood. We discovered what we believe to be a novel role for secreted frizzled-related protein-1 (sFRP-1), an antagonist of Wnt signaling, in regulating IOP. sFRP1 was overexpressed in human glaucomatous TM cells. Genes involved in the Wnt signaling pathway were expressed in cultured TM cells and human TM tissues. Addition of recombinant sFRP-1 to ex vivo perfusion-cultured human eyes decreased outflow facility, concomitant with reduced levels of β-catenin, the Wnt signaling mediator, in the TM. Intravitreal injection of an adenoviral vector encoding sFRP1 in mice produced a titer-dependent increase in IOP. Five days after vector injection, IOP increased 2 fold, which was significantly reduced by topical ocular administration of an inhibitor of a downstream suppressor of Wnt signaling. Thus, these data indicate that increased expression of sFRP1 in the TM appears to be responsible for elevated IOP in glaucoma and restoring Wnt signaling in the TM may be a novel disease intervention strategy for treating glaucoma.
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Identification of a peptide binding motif for secreted frizzled-related protein-1
Peptides, 2004Co-Authors: Yoshiro Chuman, Aykut Uren, Jennifer Cahill, Carole Regan, Vladimir Wolf, Brian K. Kay, Jeffrey S. RubinAbstract:Abstract Secreted Frizzled-related proteins (sFRPs) bind Wnts and modulate their activity. To identify putative sFRP-1 binding motifs, we screened an M13 phage displayed combinatorial peptide library. A predominant motif, L/V-VDGRW-L/V, was present in ∼70% of the phage that bound sFRP-1. Use of peptide/alkaline phosphatase chimeras and alanine scanning confirmed that the conserved motif was important for sFRP-1 recognition. The dissociation constant for a peptide/sFRP-1 complex was 3.9 μM. Additional analysis revealed that DGR was the core of the binding motif. Although Wnt proteins lack this sequence, other proteins possessing the DGR motif may function as novel binding partners for sFRP-1.