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Sox2 induction by FGF and FGFR2 activating mutations inhibits Wnt signaling and osteoblast differentiation.

Mansukhani A, Ambrosetti D, Holmes G, Cornivelli L, Basilico C - J. Cell Biol. (2005)

Bottom Line: Wnt signals promote osteoblast function and regulate bone mass.Sox2 associates with beta-catenin in osteoblasts and can inhibit the activity of a Wnt responsive reporter plasmid through its COOH-terminal domain.Our results indicate that FGF signaling could control many aspects of osteoblast differentiation through induction of Sox2 and regulation of the Wnt-beta-catenin pathway.

View Article: PubMed Central - PubMed

Affiliation: Department of Microbiology, New York University School of Medicine, New York, NY 10016, USA. mansua01@med.nyu.edu

ABSTRACT
Activating mutations in fibroblast growth factor receptor 2 (FGFR2) cause several craniosynostosis syndromes by affecting the proliferation and differentiation of osteoblasts, which form the calvarial bones. Osteoblasts respond to FGF with increased proliferation and inhibition of differentiation. We analyzed the gene expression profiles of osteoblasts expressing FGFR2 activating mutations (C342Y or S252W) and found a striking down-regulation of the expression of many Wnt target genes and a concomitant induction of the transcription factor Sox2. Most of these changes could be reproduced by treatment of osteoblasts with exogenous FGF. Wnt signals promote osteoblast function and regulate bone mass. Sox2 is expressed in calvarial osteoblasts in vivo and we show that constitutive expression of Sox2 inhibits osteoblast differentiation and causes down-regulation of the expression of numerous Wnt target genes. Sox2 associates with beta-catenin in osteoblasts and can inhibit the activity of a Wnt responsive reporter plasmid through its COOH-terminal domain. Our results indicate that FGF signaling could control many aspects of osteoblast differentiation through induction of Sox2 and regulation of the Wnt-beta-catenin pathway.

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Gene expression changes in OB1, Crouzon (CR), and Apert (AP) cells. (A) Level of expression of selected genes normalized to OB1 in growing and differentiating (diff) conditions. The average percentage of cells positive for ALP in each set is indicated at the top. Green, down-regulation in AP and CR; gold, up-regulation in AP and CR; red underlined, Wnt target genes. Microarray analysis was performed as detailed in Materials and methods. 0.00 represents <0.01. (B) Semi-quantitative RT-PCR analysis on OB1, CR, and AP cells. The amount of PCR product obtained is visualized by ethidium bromide stain.
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fig1: Gene expression changes in OB1, Crouzon (CR), and Apert (AP) cells. (A) Level of expression of selected genes normalized to OB1 in growing and differentiating (diff) conditions. The average percentage of cells positive for ALP in each set is indicated at the top. Green, down-regulation in AP and CR; gold, up-regulation in AP and CR; red underlined, Wnt target genes. Microarray analysis was performed as detailed in Materials and methods. 0.00 represents <0.01. (B) Semi-quantitative RT-PCR analysis on OB1, CR, and AP cells. The amount of PCR product obtained is visualized by ethidium bromide stain.

Mentions: Of the ∼7,800 genes that were expressed in at least one sample, 80% showed no significant change between the OB1, AP, and CR samples. Greater than 2.5-fold changes were found in 282 down-regulated and 205 up-regulated genes in the AP and CR cells compared with OB1. For most of these genes the changes were greater in AP than in the CR cells, probably because of a higher degree of FGF signaling in the AP cells (Mansukhani et al., 2000). Several interesting changes were noted, some of which are shown in Fig. 1.


Sox2 induction by FGF and FGFR2 activating mutations inhibits Wnt signaling and osteoblast differentiation.

Mansukhani A, Ambrosetti D, Holmes G, Cornivelli L, Basilico C - J. Cell Biol. (2005)

Gene expression changes in OB1, Crouzon (CR), and Apert (AP) cells. (A) Level of expression of selected genes normalized to OB1 in growing and differentiating (diff) conditions. The average percentage of cells positive for ALP in each set is indicated at the top. Green, down-regulation in AP and CR; gold, up-regulation in AP and CR; red underlined, Wnt target genes. Microarray analysis was performed as detailed in Materials and methods. 0.00 represents <0.01. (B) Semi-quantitative RT-PCR analysis on OB1, CR, and AP cells. The amount of PCR product obtained is visualized by ethidium bromide stain.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2171836&req=5

fig1: Gene expression changes in OB1, Crouzon (CR), and Apert (AP) cells. (A) Level of expression of selected genes normalized to OB1 in growing and differentiating (diff) conditions. The average percentage of cells positive for ALP in each set is indicated at the top. Green, down-regulation in AP and CR; gold, up-regulation in AP and CR; red underlined, Wnt target genes. Microarray analysis was performed as detailed in Materials and methods. 0.00 represents <0.01. (B) Semi-quantitative RT-PCR analysis on OB1, CR, and AP cells. The amount of PCR product obtained is visualized by ethidium bromide stain.
Mentions: Of the ∼7,800 genes that were expressed in at least one sample, 80% showed no significant change between the OB1, AP, and CR samples. Greater than 2.5-fold changes were found in 282 down-regulated and 205 up-regulated genes in the AP and CR cells compared with OB1. For most of these genes the changes were greater in AP than in the CR cells, probably because of a higher degree of FGF signaling in the AP cells (Mansukhani et al., 2000). Several interesting changes were noted, some of which are shown in Fig. 1.

Bottom Line: Wnt signals promote osteoblast function and regulate bone mass.Sox2 associates with beta-catenin in osteoblasts and can inhibit the activity of a Wnt responsive reporter plasmid through its COOH-terminal domain.Our results indicate that FGF signaling could control many aspects of osteoblast differentiation through induction of Sox2 and regulation of the Wnt-beta-catenin pathway.

View Article: PubMed Central - PubMed

Affiliation: Department of Microbiology, New York University School of Medicine, New York, NY 10016, USA. mansua01@med.nyu.edu

ABSTRACT
Activating mutations in fibroblast growth factor receptor 2 (FGFR2) cause several craniosynostosis syndromes by affecting the proliferation and differentiation of osteoblasts, which form the calvarial bones. Osteoblasts respond to FGF with increased proliferation and inhibition of differentiation. We analyzed the gene expression profiles of osteoblasts expressing FGFR2 activating mutations (C342Y or S252W) and found a striking down-regulation of the expression of many Wnt target genes and a concomitant induction of the transcription factor Sox2. Most of these changes could be reproduced by treatment of osteoblasts with exogenous FGF. Wnt signals promote osteoblast function and regulate bone mass. Sox2 is expressed in calvarial osteoblasts in vivo and we show that constitutive expression of Sox2 inhibits osteoblast differentiation and causes down-regulation of the expression of numerous Wnt target genes. Sox2 associates with beta-catenin in osteoblasts and can inhibit the activity of a Wnt responsive reporter plasmid through its COOH-terminal domain. Our results indicate that FGF signaling could control many aspects of osteoblast differentiation through induction of Sox2 and regulation of the Wnt-beta-catenin pathway.

Show MeSH
Related in: MedlinePlus