WNT SIGNALING AND BONE BIOLOGY

Summary

Principal Investigator: Dianqing Wu
Abstract: The goal of this proposal is to investigate the relationship between Dkk/LRP interaction and bone formation. Both human and mouse genetic evidence shows that loss of function LRP5 alleles cause osteoporosis, while putative gain of function alleles are associated with high bone mass (HBM). We showed that differentiating osteoblasts produce an autocrine canonical Wnt, which can stimulate osteoblast proliferation and differentiation and be blocked by pretreatment of Dkk. In addition, we found that HBM G171V mutation may increase Wnt signaling by preventing the inhibition of LRP5 by paracrine Dkk. Together with our finding that Dkk2 may be involved in terminal osteoblast differentiation, we hypothesize that moderate reduction in Dkk-mediated antagonism to LRP5-mediated signaling may increase bone mass, while severe reduction may cause a loss of bone formation. In this application, we will test this hypothesis by examining the effects of reduction in Dkk-mediated antagonism on bone formation in mice. Specifically, we will: 1) Determine if attenuation of Dkk-mediated antagonism by reducing Dkk1 or Dkk2 expression leads to an increase in bone formation in mice. Mouse models that express Dkk at varying levels will be created using a number of transgenic approaches and examined for the relationship between Dkk expression level and bone mass. 2) Determine if direct disruption of Dkk-LRP5 interaction increases bone mass. Transgenic mice expressing LRP5 mutants that contain mutations in the Dkk-binding surface will be created and examined for bone phenotypes. 3) Identify small molecule compounds that disrupt the LRP-Dkk interaction and Mesd- LRP interaction and determine their effects on osteogenesis. We have used a highly innovated approach that combines structural biology, in silico screen, and biological assays to successfully identify two small molecule compounds that may bind to the Dkk binding surface of LRP5. These compounds disrupt the binding of Dkkl to LRP5 and inhibit Dkk-mediated antagonism. Importantly, they increase osteogenesis in culture models. In this proposal, we will identify more efficient compounds and also carry out tests using in vivo models.
Funding Period: 2005-04-01 - 2010-03-31
more information: NIH RePORT

Top Publications

  1. pmc LRP6 mutation in a family with early coronary disease and metabolic risk factors
    Arya Mani
    Department of Internal Medicine, Howard Hughes Medical Institute and Yale University School of Medicine, New Haven, CT 06510, USA
    Science 315:1278-82. 2007
  2. pmc Regulation of phosphatidylinositol kinases and metabolism by Wnt3a and Dvl
    Yuanbo Qin
    State Key Laboratory of Molecular Biology and Center of Cell Signaling, Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200031, China
    J Biol Chem 284:22544-8. 2009
  3. pmc GSK3: a multifaceted kinase in Wnt signaling
    Dianqing Wu
    Vascular Biology and Therapeutics Program and Department of Pharmacology, Yale University School of Medicine, New Haven, CT 065202, USA
    Trends Biochem Sci 35:161-8. 2010
  4. pmc Important roles of PI3Kgamma in osteoclastogenesis and bone homeostasis
    Heeseog Kang
    Vascular Biology and Therapeutics Program and Department of Pharmacology, Yale University School of Medicine, New Haven, CT 06520, USA
    Proc Natl Acad Sci U S A 107:12901-6. 2010
  5. pmc The canonical Wnt signaling antagonist DKK2 is an essential effector of PITX2 function during normal eye development
    Philip J Gage
    Department of Ophthalmology and Visual Sciences, University of Michigan Medical School, Ann Arbor, MI 48105, USA
    Dev Biol 317:310-24. 2008
  6. pmc Characterization of the Kremen-binding site on Dkk1 and elucidation of the role of Kremen in Dkk-mediated Wnt antagonism
    Ke Wang
    State Key Laboratory of Virology, College of Life Sciences, Wuhan University, Wuhan 430072, China
    J Biol Chem 283:23371-5. 2008
  7. pmc Structural insight into the mechanisms of Wnt signaling antagonism by Dkk
    Lijun Chen
    Department of Structural Biology, St Jude Children s Research Hospital, Memphis, Tennessee 38105, USA
    J Biol Chem 283:23364-70. 2008
  8. pmc Wnt3a-mediated formation of phosphatidylinositol 4,5-bisphosphate regulates LRP6 phosphorylation
    Weijun Pan
    Department of Pharmacology, Yale University School of Medicine, New Haven, CT 06510, USA
    Science 321:1350-3. 2008
  9. pmc Sites of regulated phosphorylation that control K-Cl cotransporter activity
    Jesse Rinehart
    Department of Genetics, Howard Hughes Medical Institute, Yale University School of Medicine, New Haven, CT 06510, USA
    Cell 138:525-36. 2009

Scientific Experts

  • Dianqing Wu
  • Philip Gage
  • Weijun Pan
  • Yuanbo Qin
  • Lijun Chen
  • Ke Wang
  • He Wang
  • Heeseog Kang
  • Jesse Rinehart
  • Lin Li
  • Richard P Lifton
  • Xiaofeng Li
  • Arya Mani
  • AGNES VIGNERY
  • Marja Hurley
  • Woochul Chang
  • Mary Risinger
  • Erol E Gulcicek
  • Jessica E Tanis
  • Clinton H Joiner
  • Kathryn L Stone
  • Christopher M Colangelo
  • Caleb A Hodson
  • Junhui Zhang
  • Patrick G Gallagher
  • Yelena D Maksimova
  • Biff Forbush
  • Jie J Zheng
  • Jufang Shan
  • Cynthia Khoo
  • Xiaowu Zhang
  • Laura Swan
  • Laura Volpicelli-Daley
  • Sun Cheol Choi
  • Sergei Y Sokol
  • Charles S Abrams
  • Yazhou Zhang
  • Louise Lucast
  • Youming Shao
  • Jianguo Wu
  • Jin Huang
  • Jie Zheng
  • Khary S Carew
  • Carol Nelson-Williams
  • Mohammad Ali Mani
  • Jayaram Radhakrishnan
  • Alaleh Mani
  • Hossein Najmabadi
  • Shrikant Mane

Detail Information

Publications9

  1. pmc LRP6 mutation in a family with early coronary disease and metabolic risk factors
    Arya Mani
    Department of Internal Medicine, Howard Hughes Medical Institute and Yale University School of Medicine, New Haven, CT 06510, USA
    Science 315:1278-82. 2007
    ..These results link a single gene defect in Wnt signaling to CAD and multiple cardiovascular risk factors...
  2. pmc Regulation of phosphatidylinositol kinases and metabolism by Wnt3a and Dvl
    Yuanbo Qin
    State Key Laboratory of Molecular Biology and Center of Cell Signaling, Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200031, China
    J Biol Chem 284:22544-8. 2009
    ..Therefore, this study provides new insights into the mechanism by which Wnt3a regulates the production of PtdIns(4,5)P(2)...
  3. pmc GSK3: a multifaceted kinase in Wnt signaling
    Dianqing Wu
    Vascular Biology and Therapeutics Program and Department of Pharmacology, Yale University School of Medicine, New Haven, CT 065202, USA
    Trends Biochem Sci 35:161-8. 2010
    ..In this review, we will summarize these recent results and offer explanations, hypotheses, and models to reconcile some of these observations...
  4. pmc Important roles of PI3Kgamma in osteoclastogenesis and bone homeostasis
    Heeseog Kang
    Vascular Biology and Therapeutics Program and Department of Pharmacology, Yale University School of Medicine, New Haven, CT 06520, USA
    Proc Natl Acad Sci U S A 107:12901-6. 2010
    ..Our study also suggests that inhibition of PI3Kgamma, which is being considered as a potential therapeutic strategy for treating chronic inflammatory disorders, may result in an increase in bone mass...
  5. pmc The canonical Wnt signaling antagonist DKK2 is an essential effector of PITX2 function during normal eye development
    Philip J Gage
    Department of Ophthalmology and Visual Sciences, University of Michigan Medical School, Ann Arbor, MI 48105, USA
    Dev Biol 317:310-24. 2008
    ..We further propose a model placing PITX2 as an essential integration node between retinoic acid and canonical Wnt signaling during eye development...
  6. pmc Characterization of the Kremen-binding site on Dkk1 and elucidation of the role of Kremen in Dkk-mediated Wnt antagonism
    Ke Wang
    State Key Laboratory of Virology, College of Life Sciences, Wuhan University, Wuhan 430072, China
    J Biol Chem 283:23371-5. 2008
    ..These results suggest that Kremen may not be essential for Dkk1-mediated Wnt antagonism and that Kremen may only play a role when cells express a high level of LRP5/6...
  7. pmc Structural insight into the mechanisms of Wnt signaling antagonism by Dkk
    Lijun Chen
    Department of Structural Biology, St Jude Children s Research Hospital, Memphis, Tennessee 38105, USA
    J Biol Chem 283:23364-70. 2008
    ..Such differential binding affinity is likely to play an essential role in Dkk function in the canonical Wnt pathway...
  8. pmc Wnt3a-mediated formation of phosphatidylinositol 4,5-bisphosphate regulates LRP6 phosphorylation
    Weijun Pan
    Department of Pharmacology, Yale University School of Medicine, New Haven, CT 06510, USA
    Science 321:1350-3. 2008
    ..In turn, PtdIns (4,5)P2 regulated phosphorylation of LRP6 at Thr1479 and Ser1490. Therefore, our study reveals a signaling mechanism for Wnt to regulate LRP6 phosphorylation...
  9. pmc Sites of regulated phosphorylation that control K-Cl cotransporter activity
    Jesse Rinehart
    Department of Genetics, Howard Hughes Medical Institute, Yale University School of Medicine, New Haven, CT 06510, USA
    Cell 138:525-36. 2009
    ..These findings provide insight into regulation of [Cl(-)](i) and have implications for control of cell volume and neuronal function...