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Original Article
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Volume 346:1513-1521 May 16, 2002 Number 20
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High Bone Density Due to a Mutation in LDL-Receptor–Related Protein 5
Lynn M. Boyden, Ph.D., Junhao Mao, Ph.D., Joseph Belsky, M.D., Lyle Mitzner, M.D., Anita Farhi, R.N., Mary A. Mitnick, Ph.D., Dianqing Wu, Ph.D., Karl Insogna, M.D., and Richard P. Lifton, M.D., Ph.D.

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ABSTRACT

Background Osteoporosis is a major public health problem of largely unknown cause. Loss-of-function mutations in the gene for low-density lipoprotein receptor–related protein 5 (LRP5), which acts in the Wnt signaling pathway, have been shown to cause osteoporosis–pseudoglioma.

Methods We performed genetic and biochemical analyses of a kindred with an autosomal dominant syndrome characterized by high bone density, a wide and deep mandible, and torus palatinus.

Results Genetic analysis revealed linkage of the syndrome to chromosome 11q12–13 (odds of linkage, >1 million to 1), an interval that contains LRP5. Affected members of the kindred had a mutation in this gene, with valine substituted for glycine at codon 171 (LRP5V171). This mutation segregated with the trait in the family and was absent in control subjects. The normal glycine lies in a so-called propeller motif that is highly conserved from fruit flies to humans. Markers of bone resorption were normal in the affected subjects, whereas markers of bone formation such as osteocalcin were markedly elevated. Levels of fibronectin, a known target of signaling by Wnt, a developmental protein, were also elevated. In vitro studies showed that the normal inhibition of Wnt signaling by another protein, Dickkopf-1 (Dkk-1), was defective in the presence of LRP5V171 and that this resulted in increased signaling due to unopposed Wnt activity.

Conclusions The LRP5V171 mutation causes high bone density, with a thickened mandible and torus palatinus, by impairing the action of a normal antagonist of the Wnt pathway and thus increasing Wnt signaling. These findings demonstrate the role of altered LRP5 function in high bone mass and point to Dkk as a potential target for the prevention or treatment of osteoporosis.


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From the Departments of Genetics (L.M.B., A.F., R.P.L.) and Medicine (J.B., L.M., M.A.M., K.I., R.P.L.), Yale University School of Medicine, New Haven; and the Department of Genetics and Developmental Biology (J.M., D.W.), University of Connecticut Health Center, Farmington — both in Connecticut.

Address reprint requests to Dr. Lifton at the Yale University School of Medicine, Boyer Center for Molecular Medicine, 295 Congress Ave., New Haven, CT 06510, or at richard.lifton{at}yale.edu.

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Related Letters:

High Bone Density Due to a Mutation in LDL-Receptor–Related Protein 5
Little R. D., Recker R. R., Johnson M. L., Hofbauer L. C., Maisch B., Schaefer J. R., Boyden L., Insogna K., Lifton R. P.
Extract | Full Text | PDF  
N Engl J Med 2002; 347:943-944, Sep 19, 2002. Correspondence

High-Bone-Mass Disease and LRP5
Whyte M. P., Reinus W. H., Mumm S., Boyden L. M., Insogna K., Lifton R. P.
Extract | Full Text | PDF  
N Engl J Med 2004; 350:2096-2099, May 13, 2004. Correspondence

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