•  
     
     
    Type Size
     

    Suppression of bone formation by osteoclastic expression of semaphorin 4D.

    The authors found that osteoclasts express semaphorin 4D (Sema4D), previously shown to be an axon guidance molecule, which potently inhibits bone formation. The binding of Sema4D to its receptor Plexin-B1 on osteoblasts resulted in the activation of the small GTPase RhoA, which inhibits bone formation by suppressing insulin-like growth factor-1 (IGF-1) signaling and by modulating osteoblast motility. Sema4d−/− mice, Plxnb1−/− mice and mice expressing a dominant-negative RhoA specifically in osteoblasts showed an osteosclerotic phenotype due to augmented bone formation.  In addition, Sema4D-specific antibody treatment markedly prevented bone loss in a model of postmenopausal osteoporosis.

    http://www.nature.com/nm/journal/vaop/ncurrent/full/nm.2489.html