Twisted gastrulation, a bone morphogenetic protein agonist/antagonist, is not required for post-natal skeletal function

Elisabetta Gazzerro, Valerie Deregowski, Lisa Stadmeyer, Nickolas W. Gale, Aris N. Economides, Ernesto Canalis

Research output: Contribution to journalArticlepeer-review

Abstract

Twisted gastrulation (Tsg) is a secreted glycoprotein that binds bone morphogenetic proteins (BMP)-2 and -4 and can display both BMP agonist and antagonist functions. Tsg promotes BMP-mediated endochondral ossification, but its activity in adult bone is not known. We created tsg null mice and examined the consequences of the tsg deletion on the skeleton in vivo and on osteoblast function in vitro. Analysis of the skeletal phenotype of 4-week-old tsg null mice revealed a 40% decrease in trabecular bone volume, but osteoblast and osteoclast number, and bone formation and resorption were not affected. The phenotype was transient, and at 7 weeks of age tsg null mice were not different from control wild-type mice. The decreased trabecular bone is congruent with a defect in endochondral bone formation. In osteoblasts isolated from tsg null mice, tsg gene inactivation decreased the BMP-2 stimulatory effects on osteocalcin expression and alkaline phosphatase activity, indicating that in the bone microenvironment endogenous Tsg enhances BMP activity. Accordingly, tsg null cells displayed impaired BMP signaling. These results were confirmed by Tsg down-regulation in primary osteoblasts from wild-type mice using RNA interference. In conclusion, endogenous Tsg is required for normal BMP activity in osteoblastic cells in vitro, but it plays a minor role in the regulation of adult bone homeostasis in vivo.

Original languageEnglish
Pages (from-to)1252-1260
Number of pages9
JournalBone
Volume39
Issue number6
DOIs
Publication statusPublished - Dec 2006

Keywords

  • Bone morphogenetic proteins
  • Differentiation
  • Marrow stroma
  • Osteoblast
  • Signaling

ASJC Scopus subject areas

  • Physiology
  • Hematology

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