A Dominant Negative Cadherin Inhibits Osteoblast Differentiation

Authors

  • Su-Li Cheng,

    1. Division of Bone and Mineral Diseases, Department of Medicine, Washington University School of Medicine, Barnes-Jewish Hospital, St. Louis, Missouri, U.S.A.
    2. These authors contributed equally to the work reported and both should be considered as first authors
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  • Chan Soo Shin,

    1. Division of Bone and Mineral Diseases, Department of Medicine, Washington University School of Medicine, Barnes-Jewish Hospital, St. Louis, Missouri, U.S.A.
    2. These authors contributed equally to the work reported and both should be considered as first authors
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  • Dwight A. Towler,

    1. Department of Pharmacology and Molecular Biology, Washington University School of Medicine, Barnes-Jewish Hospital, St. Louis, Missouri, U.S.A.
    2. Present address: Department of Bone Biology and Osteoporosis, Merck & Co., West Point, Pennsylvania, U.S.A.
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  • Roberto Civitelli

    Corresponding author
    1. Division of Bone and Mineral Diseases, Department of Medicine, Washington University School of Medicine, Barnes-Jewish Hospital, St. Louis, Missouri, U.S.A.
    • Address reprint requests to: Roberto Civitelli, M.D., Division of Bone and Mineral Diseases, Washington University School of Medicine, Barnes-Jewish Hospital, North Campus, 216 South Kingshighway Boulevard, St. Louis, MO 63110, U.S.A.
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  • Presented in part in abstract form at the 2nd Joint Meeting of the International Bone and Mineral Society and the American Society for Bone and Mineral Research, San Francisco, California, U.S.A., December 1998, Abstract 1021

Abstract

We have previously indicated that human osteoblasts express a repertoire of cadherins and that perturbation of cadherin-mediated cell-cell interaction reduces bone morphogenetic protein 2 (BMP-2) stimulation of alkaline phosphatase activity. To test whether inhibition of cadherin function interferes with osteoblast function, we expressed a truncated N-cadherin mutant (NCadδC) with dominant negative action in MC3T3-E1 osteoblastic cells. In stably transfected clones, calcium-dependent cell-cell adhesion was decreased by 50%. Analysis of matrix protein expression during a 4-week culture period revealed that bone sialoprotein, osteocalcin, and type I collagen were substantially inhibited with time in culture, whereas osteopontin transiently increased. Basal alkaline phosphatase activity declined in cells expressing NCadΔC, relative to control cells, after 3 weeks in culture, and their cell proliferation rate was reduced moderately (17%). Finally,45Ca uptake, an index of matrix mineralization, was decreased by 35% in NCadΔC-expressing cells compared with control cultures after 4 weeks in medium containing ascorbic acid and β-glycerophosphate. Similarly, BMP-2 stimulation of alkaline phosphatase activity and bone sialoprotein and osteopontin expression also were curtailed in NCadΔC cells. Therefore, expression of dominant negative cadherin results in decreased cell-cell adhesion associated with altered bone matrix protein expression and decreased matrix mineralization. Cadherin-mediated cell-cell adhesion is involved in regulating the function of bone-forming cells.

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