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Transcriptional Regulation of Frizzled-1 in Human Osteoblasts by Sp1

Shibing Yu1, Laura M Yerges-Armstrong2,3, Yanxia Chu1

  • 1Department of Medicine, School of Medicine, University of Pittsburgh, Pennsylvania, United States of America.

Plos One
|October 4, 2016
PubMed

Insights

Sp1 transcription factor regulates Frizzled 1 (FZD1) gene expression in osteoblasts. This Sp1-mediated FZD1 activation is crucial for bone formation and mineralization, offering therapeutic potential for skeletal disorders.

Area of Science:

  • Molecular Biology
  • Cell Biology
  • Biochemistry

Background:

  • The wingless (Wnt) pathway significantly impacts bone metabolism and is a key therapeutic target for skeletal disorders.
  • Frizzled (FZD) receptors mediate Wnt signaling, but their transcriptional regulation remains largely unelucidated.
  • Understanding FZD gene regulation is critical for developing novel skeletal disorder therapies.

Purpose of the Study:

  • To investigate the role of Sp1 transcription factor in regulating Frizzled 1 (FZD1) gene expression in osteoblasts.
  • To determine the impact of Sp1-mediated FZD1 regulation on osteoblast differentiation and mineralization.

Main Methods:

  • FZD1 promoter assays were performed in Saos2 cells with and without Sp1 overexpression.
  • Chromatin immunoprecipitation (ChIP) and electrophoretic mobility shift assays (EMSA) identified Sp1 binding sites on the FZD1 promoter.
  • Mithramycin A (MMA) was used to inhibit Sp1 activity; Sp1 was also downregulated in hFOB cells.
  • FZD1 knockdown was performed to assess its role in Sp1-stimulated osteoblast differentiation.

Main Results:

  • Sp1 significantly up-regulates FZD1 promoter activity in osteoblast-like cells.
  • A functional Sp1 binding site was identified in the FZD1 promoter region (-44 to -40).
  • Sp1-dependent FZD1 activation was inhibited by MMA; Sp1 downregulation reduced FZD1 expression and alkaline phosphatase activity.
  • Sp1 overexpression enhanced FZD1 expression and Saos2 cell mineralization; FZD1 knockdown partially blocked Sp1's pro-differentiation effects.

Conclusions:

  • Sp1 plays a significant role in human osteoblast differentiation and mineralization.
  • Sp1-dependent transactivation of FZD1 is a key mechanism mediating Sp1's effects on bone cells.
  • Targeting the Sp1-FZD1 axis presents a potential therapeutic strategy for skeletal disorders.

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