Genomes and Genes
WNT SIGNALING AND BONE BIOLOGY
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
- LRP6 mutation in a family with early coronary disease and metabolic risk factorsArya 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...
- Regulation of phosphatidylinositol kinases and metabolism by Wnt3a and DvlYuanbo 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)...
- GSK3: a multifaceted kinase in Wnt signalingDianqing 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...
- Important roles of PI3Kgamma in osteoclastogenesis and bone homeostasisHeeseog 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...
- The canonical Wnt signaling antagonist DKK2 is an essential effector of PITX2 function during normal eye developmentPhilip 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...
- Characterization of the Kremen-binding site on Dkk1 and elucidation of the role of Kremen in Dkk-mediated Wnt antagonismKe 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...
- Structural insight into the mechanisms of Wnt signaling antagonism by DkkLijun 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...
- Wnt3a-mediated formation of phosphatidylinositol 4,5-bisphosphate regulates LRP6 phosphorylationWeijun 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...
- Sites of regulated phosphorylation that control K-Cl cotransporter activityJesse 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...