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Skeletal Phenotype Analysis of a Conditional Stat3 Deletion Mouse Model
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The protein tyrosine phosphatase Rptpzeta is expressed in differentiated osteoblasts and affects bone formation in

T Schinke1, M Gebauer, A F Schilling

  • 1Department of Trauma, Hand, and Reconstructive Surgery, University Medical Center Hamburg Eppendorf, Hamburg 20246, Germany.

Bone
|January 8, 2008
PubMed

Insights

Protein tyrosine phosphatase zeta (Rptpzeta) is crucial for bone remodeling. Mice lacking Rptpzeta show reduced bone volume and impaired osteoblast function, indicating its role in bone formation.

Area of Science:

  • Molecular Biology
  • Cell Biology
  • Bone Biology

Background:

  • Protein tyrosine phosphatases (PTPs) regulate cellular processes by counteracting tyrosine kinases.
  • Rptpzeta, a PTP, has been implicated in bone remodeling, with its expression affected by pleiotrophin.
  • The specific role of Rptpzeta in bone formation remains largely uncharacterized.

Purpose of the Study:

  • To investigate the role of Rptpzeta in bone remodeling.
  • To determine the expression pattern of Rptpzeta in osteoblasts.
  • To analyze the skeletal phenotype of Rptpzeta-deficient mice.

Main Methods:

  • Genome-wide expression analysis to identify Ptprz1 induction in osteoblasts.
  • RT-PCR and Western Blotting to confirm Rptpzeta isoform expression.
  • Histomorphometry and histology of Rptpzeta-deficient mouse models.
  • Ex vivo analysis of Rptpzeta-deficient osteoblasts.

Main Results:

  • Ptprz1 (Rptpzeta gene) is strongly induced during osteoblast differentiation.
  • Differentiated osteoblasts specifically express the short transmembrane isoform of Rptpzeta.
  • Rptpzeta-deficient mice exhibit decreased trabecular bone volume and reduced bone formation rate.
  • Rptpzeta-deficient osteoblasts show reduced expression of osteoblast markers and impaired osteocyte-like extension formation.

Conclusions:

  • Rptpzeta plays a significant physiological role in bone remodeling.
  • Rptpzeta is essential for regulating bone formation in vivo.
  • This study identifies Rptpzeta as the first PTP to directly regulate bone formation.

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