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Olig2-induced neural stem cell differentiation involves downregulation of Wnt signaling and induction of Dickkopf-1 expression.

Ahn SM, Byun K, Kim D, Lee K, Yoo JS, Kim SU, Jho EH, Simpson RJ, Lee B - PLoS ONE (2008)

Bottom Line: Furthermore, we found that Olig2-induced differentiation induces the expression of Dickkopf-1(Dkk1), a potent antagonist of Wnt signaling.Dkk1 treatment blocked Wnt signaling in HB1.F3 in a dosage-dependent manner, and induced differentiation into astrocytes, oligodendrocytes, and neurons.In our proposed model, Dkk1 may play an important role in downregulating self-renewal and proliferation pathway of stem cells at the late stage of differentiation, and its failure may lead to carcinogenesis.

View Article: PubMed Central - PubMed

Affiliation: Center for Genomics and Proteomics, Lee Gil Ya Cancer and Diabetes Institute, Gachon University of Medicine and Science, Incheon, Korea.

ABSTRACT
Understanding stem cell-differentiation at the molecular level is important for clinical applications of stem cells and for finding new therapeutic approaches in the context of cancer stem cells. To investigate genome-wide changes involved in differentiation, we have used immortalized neural stem cell (NSC) line (HB1.F3) and Olig2-induced NSC differentiation model (F3.Olig2). Using microarray analysis, we revealed that Olig2-induced NSC differentiation involves downregulation of Wnt pathway, which was further confirmed by TOPflash/FOPflash reporter assay, RT-PCR analysis, immunoblots, and immunocytochemistry. Furthermore, we found that Olig2-induced differentiation induces the expression of Dickkopf-1(Dkk1), a potent antagonist of Wnt signaling. Dkk1 treatment blocked Wnt signaling in HB1.F3 in a dosage-dependent manner, and induced differentiation into astrocytes, oligodendrocytes, and neurons. Our results support cancer stem cell hypothesis which implies that signaling pathway for self-renewal and proliferation of stem cells is maintained till the late stage of differentiation. In our proposed model, Dkk1 may play an important role in downregulating self-renewal and proliferation pathway of stem cells at the late stage of differentiation, and its failure may lead to carcinogenesis.

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Levels of β-catenin and phospho-β-catenin (p-β-catenin), and their subcellular localization.In HB1.F3, β-catenin is mainly localized in nucleus (A), and p-β-catenin is not detected (B, C). In F3.Olig2, β-catenin is mainly localized in cytoplasm (A), and p-β-catenin is detected and mainly localized in nucleus (B, C). The level of GSK3β, which phosphorylates β-catenin on Ser-33/Ser-37/Thr-41, is increased in F3.Olig2 (C). Bar = 50 µm
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pone-0003917-g004: Levels of β-catenin and phospho-β-catenin (p-β-catenin), and their subcellular localization.In HB1.F3, β-catenin is mainly localized in nucleus (A), and p-β-catenin is not detected (B, C). In F3.Olig2, β-catenin is mainly localized in cytoplasm (A), and p-β-catenin is detected and mainly localized in nucleus (B, C). The level of GSK3β, which phosphorylates β-catenin on Ser-33/Ser-37/Thr-41, is increased in F3.Olig2 (C). Bar = 50 µm

Mentions: Wnt signaling is transduced to β-catenin in cytoplasm, which enters the nucleus and activate transcription of Wnt pathway target genes with TCF [29]. On the other hand, phosphorylation of β-catenin leads to ubiquitination and degradation of β-catenin [30], [31]. In HB1.F3, β-catenin is mainly localized in nucleus and p- β-catenin (pS33/pS37/pT41) is not detected (Fig. 4A, B). In F3.Olig2, β-catenin is mainly localized in cytoplasm, and p- β-catenin pS33/pS37/pT41) is exclusively observed in nucleus (Fig. 4A, B). In immunoblot analysis (Fig. 4C), the expression of β-catenin is increased in F3.Olig2 and p- β-catenin (pS33/pS37/pT41) was detected only in F3.Olig2. The level of GSK3β, which phosphorylates β-catenin on S33/S37/T41 [32], is also increased in F3.Olig2.


Olig2-induced neural stem cell differentiation involves downregulation of Wnt signaling and induction of Dickkopf-1 expression.

Ahn SM, Byun K, Kim D, Lee K, Yoo JS, Kim SU, Jho EH, Simpson RJ, Lee B - PLoS ONE (2008)

Levels of β-catenin and phospho-β-catenin (p-β-catenin), and their subcellular localization.In HB1.F3, β-catenin is mainly localized in nucleus (A), and p-β-catenin is not detected (B, C). In F3.Olig2, β-catenin is mainly localized in cytoplasm (A), and p-β-catenin is detected and mainly localized in nucleus (B, C). The level of GSK3β, which phosphorylates β-catenin on Ser-33/Ser-37/Thr-41, is increased in F3.Olig2 (C). Bar = 50 µm
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2602983&req=5

pone-0003917-g004: Levels of β-catenin and phospho-β-catenin (p-β-catenin), and their subcellular localization.In HB1.F3, β-catenin is mainly localized in nucleus (A), and p-β-catenin is not detected (B, C). In F3.Olig2, β-catenin is mainly localized in cytoplasm (A), and p-β-catenin is detected and mainly localized in nucleus (B, C). The level of GSK3β, which phosphorylates β-catenin on Ser-33/Ser-37/Thr-41, is increased in F3.Olig2 (C). Bar = 50 µm
Mentions: Wnt signaling is transduced to β-catenin in cytoplasm, which enters the nucleus and activate transcription of Wnt pathway target genes with TCF [29]. On the other hand, phosphorylation of β-catenin leads to ubiquitination and degradation of β-catenin [30], [31]. In HB1.F3, β-catenin is mainly localized in nucleus and p- β-catenin (pS33/pS37/pT41) is not detected (Fig. 4A, B). In F3.Olig2, β-catenin is mainly localized in cytoplasm, and p- β-catenin pS33/pS37/pT41) is exclusively observed in nucleus (Fig. 4A, B). In immunoblot analysis (Fig. 4C), the expression of β-catenin is increased in F3.Olig2 and p- β-catenin (pS33/pS37/pT41) was detected only in F3.Olig2. The level of GSK3β, which phosphorylates β-catenin on S33/S37/T41 [32], is also increased in F3.Olig2.

Bottom Line: Furthermore, we found that Olig2-induced differentiation induces the expression of Dickkopf-1(Dkk1), a potent antagonist of Wnt signaling.Dkk1 treatment blocked Wnt signaling in HB1.F3 in a dosage-dependent manner, and induced differentiation into astrocytes, oligodendrocytes, and neurons.In our proposed model, Dkk1 may play an important role in downregulating self-renewal and proliferation pathway of stem cells at the late stage of differentiation, and its failure may lead to carcinogenesis.

View Article: PubMed Central - PubMed

Affiliation: Center for Genomics and Proteomics, Lee Gil Ya Cancer and Diabetes Institute, Gachon University of Medicine and Science, Incheon, Korea.

ABSTRACT
Understanding stem cell-differentiation at the molecular level is important for clinical applications of stem cells and for finding new therapeutic approaches in the context of cancer stem cells. To investigate genome-wide changes involved in differentiation, we have used immortalized neural stem cell (NSC) line (HB1.F3) and Olig2-induced NSC differentiation model (F3.Olig2). Using microarray analysis, we revealed that Olig2-induced NSC differentiation involves downregulation of Wnt pathway, which was further confirmed by TOPflash/FOPflash reporter assay, RT-PCR analysis, immunoblots, and immunocytochemistry. Furthermore, we found that Olig2-induced differentiation induces the expression of Dickkopf-1(Dkk1), a potent antagonist of Wnt signaling. Dkk1 treatment blocked Wnt signaling in HB1.F3 in a dosage-dependent manner, and induced differentiation into astrocytes, oligodendrocytes, and neurons. Our results support cancer stem cell hypothesis which implies that signaling pathway for self-renewal and proliferation of stem cells is maintained till the late stage of differentiation. In our proposed model, Dkk1 may play an important role in downregulating self-renewal and proliferation pathway of stem cells at the late stage of differentiation, and its failure may lead to carcinogenesis.

Show MeSH
Related in: MedlinePlus