Nephroblastoma overexpressed (Nov) inhibits osteoblastogenesis and causes osteopenia.
Nephroblastoma overexpressed (Nov), a member of the Cyr 61, connective tissue growth factor, Nov (CCN) family of proteins, is expressed by osteoblasts, but its function in cells of the osteoblastic lineage is not known. We investigated the effects of Nov overexpression by transducing murine ST-2 stromal and MC3T3 osteoblastic cells with a retroviral vector where Nov is under the control of the cytomegalovirus promoter. We also examined the skeletal phenotype of transgenic mice expressing Nov under the control of the human osteocalcin promoter. Overexpression of Nov in ST-2 cells inhibited the appearance of mineralized nodules and decreased alkaline phosphatase activity and osteocalcin mRNA levels. Nov overexpression inhibited the effect of bone morphogenetic protein (BMP)-2 on the phosphorylation of Smad 1/5/8; on the transactivation of 12xSBE-Oc-pGL3, a BMP/Smad signaling reporter construct, and of Wnt 3 on cytoplasmic beta-catenin levels; and on the transactivation of the Wnt/beta-catenin signaling reporter construct 16xTCF-Luc. Nov overexpression did not activate Notch or transforming growth factor beta signaling. Glutathione S-transferase pulldown assays demonstrated direct Nov-BMP interactions. Nov transgenic mice exhibited osteopenia. In conclusion, Nov binds BMP-2 and antagonizes BMP-2 and Wnt activity, and its overexpression inhibits osteoblastogenesis and causes osteopenia.
Rydziel
Sheila
S
Department of Research, Saint Francis Hospital and Medical Center, Hartford, Connecticut 06105, USA.
Stadmeyer
Lisa
L
Zanotti
Stefano
S
Durant
Deena
D
Smerdel-Ramoya
Anna
A
Canalis
Ernesto
E
D000469:Alkaline Phosphatase / Q000096:biosynthesis / Q000235:genetics; D000818:Animals; D001851:Bone Diseases, Metabolic / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D055396:Bone Morphogenetic Protein 2; D019485:Bone Morphogenetic Proteins / Q000235:genetics / Q000378:metabolism*; D002460:Cell Line; D055513:Connective Tissue Growth Factor; D005260:Female; D015870:Gene Expression; D006801:Humans; D017874:Immediate-Early Proteins / Q000096:biosynthesis* / Q000235:genetics; D036341:Intercellular Signaling Peptides and Proteins / Q000096:biosynthesis* / Q000235:genetics; D051379:Mice; D008822:Mice, Transgenic; D055514:Nephroblastoma Overexpressed Protein; D015675:Osteocalcin / Q000235:genetics; D010012:Osteogenesis / Q000235:genetics; D011401:Promoter Regions, Genetic; D011485:Protein Binding / Q000235:genetics; D015398:Signal Transduction / Q000235:genetics; D051785:Smad Proteins / Q000235:genetics / Q000378:metabolism; D016212:Transforming Growth Factor beta / Q000235:genetics / Q000378:metabolism*; D051153:Wnt Proteins / Q000235:genetics / Q000378:metabolism
C525718:BMP2 protein, human; C525719:Bmp2 protein, mouse; D055396:Bone Morphogenetic Protein 2; D019485:Bone Morphogenetic Proteins; C526317:CCN2 protein, human; C526318:CCN2 protein, mouse; C526319:CCN3 protein, human; C526320:Ccn3 protein, mouse; D017874:Immediate-Early Proteins; D036341:Intercellular Signaling Peptides and Proteins; D055514:Nephroblastoma Overexpressed Protein; D051785:Smad Proteins; D016212:Transforming Growth Factor beta; D051153:Wnt Proteins; D015675:Osteocalcin; D055513:Connective Tissue Growth Factor; D000469:Alkaline Phosphatase