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Tatsuji Haneji - One of the best experts on this subject based on the ideXlab platform.
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protein phosphatase 2a cα regulates Osteoblast Differentiation and the expressions of bone sialoprotein and osteocalcin via osterix transcription factor
Journal of Cellular Physiology, 2013Co-Authors: Hirohiko Okamura, Kaya Yoshida, Di Yang, Tatsuji HanejiAbstract:Serine/threonine protein phosphatase 2A (PP2A) participates in regulating many important physiological processes such as cell cycle, growth, apoptosis, and signal transduction. Osterix is a zinc-finger-containing transcription factor that is essential for Osteoblast Differentiation and regulation of many bone-related genes. We have recently reported that decrease in α-isoform of PP2A catalytic subunit (PP2A Cα) accelerates Osteoblast Differentiation through the expression of bone-related genes. In this study, we further examined the role of PP2A Cα in Osteoblast Differentiation by establishing the stable cell lines that overexpress PP2A Cα. Overexpression of PP2A Cα reduced alkaline phosphatase (ALP) activity. Osteoblast Differentiation and mineralization were also decreased in PP2A Cα-overexpressing cells, with reduction of bone-related genes including osterix, bone sialoprotein (Bsp), and osteocalcin (OCN). Luciferase assay showed that the transcriptional activity of the Osterix promoter region was decreased in PP2A Cα-overexpressing cells. Introduction of ectopic Osterix rescued the expression of Bsp and OCN in PP2A Cα-overexpressing cells. These results indicate that PP2A Cα and its activity play a negative role in Osteoblast Differentiation and Osterix is a key factor responsible for regulating the expressions of Bsp and OCN during PP2A Cα-mediated Osteoblast Differentiation. J. Cell. Physiol. © 2012 Wiley Periodicals, Inc.
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protein phosphatase 2a cα regulates Osteoblast Differentiation and the expressions of bone sialoprotein and osteocalcin via osterix transcription factor
Journal of Cellular Physiology, 2013Co-Authors: Hirohiko Okamura, Kaya Yoshida, Di Yang, Tatsuji HanejiAbstract:Serine/threonine protein phosphatase 2A (PP2A) participates in regulating many important physiological processes such as cell cycle, growth, apoptosis, and signal transduction. Osterix is a zinc-finger-containing transcription factor that is essential for Osteoblast Differentiation and regulation of many bone-related genes. We have recently reported that decrease in α-isoform of PP2A catalytic subunit (PP2A Cα) accelerates Osteoblast Differentiation through the expression of bone-related genes. In this study, we further examined the role of PP2A Cα in Osteoblast Differentiation by establishing the stable cell lines that overexpress PP2A Cα. Overexpression of PP2A Cα reduced alkaline phosphatase (ALP) activity. Osteoblast Differentiation and mineralization were also decreased in PP2A Cα-overexpressing cells, with reduction of bone-related genes including osterix, bone sialoprotein (Bsp), and osteocalcin (OCN). Luciferase assay showed that the transcriptional activity of the Osterix promoter region was decreased in PP2A Cα-overexpressing cells. Introduction of ectopic Osterix rescued the expression of Bsp and OCN in PP2A Cα-overexpressing cells. These results indicate that PP2A Cα and its activity play a negative role in Osteoblast Differentiation and Osterix is a key factor responsible for regulating the expressions of Bsp and OCN during PP2A Cα-mediated Osteoblast Differentiation.
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reduction of protein phosphatase 2a cα enhances bone formation and Osteoblast Differentiation through the expression of bone specific transcription factor osterix
Bone, 2011Co-Authors: Hirohiko Okamura, Kazuhiko Ochiai, Kaya Yoshida, Tatsuji HanejiAbstract:Abstract The serine/threonine protein phosphatase 2A (PP2A) participates in regulating many important physiological processes such as control of cell cycle, growth, and division. On the other hand, Osterix is a zinc-finger-containing transcription factor that is essential for the Differentiation of Osteoblasts and regulation of many bone-related genes. Here we examined the effect of okadaic acid (OA), a specific inhibitor of PP2A, on bone formation in vivo and the molecular mechanism regulated by PP2A Cα in Osteoblast Differentiation. Administration of 1 nM OA to the calvarial region in mice increased bone mineral density, as shown by μ CT , while histomorphological analysis showed an increase in mineral apposition and bone thickness in the same region. In addition, treatment with 1 nM OA stimulated Osteoblast Differentiation and the expression of Osterix, bone sialoprotein (Bsp), and osteocalcin (OCN) in mouse Osteoblastic MC3T3-E1 cells. Moreover, the expression and phosphatase activity of PP2A Cα was decreased in the initial step of Osteoblast Differentiation, which was in parallel with an increase in Osterix expression. To further clarify the role of PP2A Cα in Osteoblast Differentiation, we constructed PP2A knock-down cells by infecting MC3T3-E1 cells with a lentivirus expressing shRNA specific for the PP2A Cα. Accordingly, the silencing of PP2A Cα in MC3T3-E1 cells dramatically increased Osteoblast Differentiation and mineralization, which were accompanied with expressions of Osterix, Bsp, and OCN. Our data indicate that PP2A Cα plays an important role in the regulation of bone formation and Osteoblast Differentiation through the bone-related genes.
Hirohiko Okamura - One of the best experts on this subject based on the ideXlab platform.
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protein phosphatase 2a cα regulates Osteoblast Differentiation and the expressions of bone sialoprotein and osteocalcin via osterix transcription factor
Journal of Cellular Physiology, 2013Co-Authors: Hirohiko Okamura, Kaya Yoshida, Di Yang, Tatsuji HanejiAbstract:Serine/threonine protein phosphatase 2A (PP2A) participates in regulating many important physiological processes such as cell cycle, growth, apoptosis, and signal transduction. Osterix is a zinc-finger-containing transcription factor that is essential for Osteoblast Differentiation and regulation of many bone-related genes. We have recently reported that decrease in α-isoform of PP2A catalytic subunit (PP2A Cα) accelerates Osteoblast Differentiation through the expression of bone-related genes. In this study, we further examined the role of PP2A Cα in Osteoblast Differentiation by establishing the stable cell lines that overexpress PP2A Cα. Overexpression of PP2A Cα reduced alkaline phosphatase (ALP) activity. Osteoblast Differentiation and mineralization were also decreased in PP2A Cα-overexpressing cells, with reduction of bone-related genes including osterix, bone sialoprotein (Bsp), and osteocalcin (OCN). Luciferase assay showed that the transcriptional activity of the Osterix promoter region was decreased in PP2A Cα-overexpressing cells. Introduction of ectopic Osterix rescued the expression of Bsp and OCN in PP2A Cα-overexpressing cells. These results indicate that PP2A Cα and its activity play a negative role in Osteoblast Differentiation and Osterix is a key factor responsible for regulating the expressions of Bsp and OCN during PP2A Cα-mediated Osteoblast Differentiation. J. Cell. Physiol. © 2012 Wiley Periodicals, Inc.
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protein phosphatase 2a cα regulates Osteoblast Differentiation and the expressions of bone sialoprotein and osteocalcin via osterix transcription factor
Journal of Cellular Physiology, 2013Co-Authors: Hirohiko Okamura, Kaya Yoshida, Di Yang, Tatsuji HanejiAbstract:Serine/threonine protein phosphatase 2A (PP2A) participates in regulating many important physiological processes such as cell cycle, growth, apoptosis, and signal transduction. Osterix is a zinc-finger-containing transcription factor that is essential for Osteoblast Differentiation and regulation of many bone-related genes. We have recently reported that decrease in α-isoform of PP2A catalytic subunit (PP2A Cα) accelerates Osteoblast Differentiation through the expression of bone-related genes. In this study, we further examined the role of PP2A Cα in Osteoblast Differentiation by establishing the stable cell lines that overexpress PP2A Cα. Overexpression of PP2A Cα reduced alkaline phosphatase (ALP) activity. Osteoblast Differentiation and mineralization were also decreased in PP2A Cα-overexpressing cells, with reduction of bone-related genes including osterix, bone sialoprotein (Bsp), and osteocalcin (OCN). Luciferase assay showed that the transcriptional activity of the Osterix promoter region was decreased in PP2A Cα-overexpressing cells. Introduction of ectopic Osterix rescued the expression of Bsp and OCN in PP2A Cα-overexpressing cells. These results indicate that PP2A Cα and its activity play a negative role in Osteoblast Differentiation and Osterix is a key factor responsible for regulating the expressions of Bsp and OCN during PP2A Cα-mediated Osteoblast Differentiation.
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reduction of protein phosphatase 2a cα enhances bone formation and Osteoblast Differentiation through the expression of bone specific transcription factor osterix
Bone, 2011Co-Authors: Hirohiko Okamura, Kazuhiko Ochiai, Kaya Yoshida, Tatsuji HanejiAbstract:Abstract The serine/threonine protein phosphatase 2A (PP2A) participates in regulating many important physiological processes such as control of cell cycle, growth, and division. On the other hand, Osterix is a zinc-finger-containing transcription factor that is essential for the Differentiation of Osteoblasts and regulation of many bone-related genes. Here we examined the effect of okadaic acid (OA), a specific inhibitor of PP2A, on bone formation in vivo and the molecular mechanism regulated by PP2A Cα in Osteoblast Differentiation. Administration of 1 nM OA to the calvarial region in mice increased bone mineral density, as shown by μ CT , while histomorphological analysis showed an increase in mineral apposition and bone thickness in the same region. In addition, treatment with 1 nM OA stimulated Osteoblast Differentiation and the expression of Osterix, bone sialoprotein (Bsp), and osteocalcin (OCN) in mouse Osteoblastic MC3T3-E1 cells. Moreover, the expression and phosphatase activity of PP2A Cα was decreased in the initial step of Osteoblast Differentiation, which was in parallel with an increase in Osterix expression. To further clarify the role of PP2A Cα in Osteoblast Differentiation, we constructed PP2A knock-down cells by infecting MC3T3-E1 cells with a lentivirus expressing shRNA specific for the PP2A Cα. Accordingly, the silencing of PP2A Cα in MC3T3-E1 cells dramatically increased Osteoblast Differentiation and mineralization, which were accompanied with expressions of Osterix, Bsp, and OCN. Our data indicate that PP2A Cα plays an important role in the regulation of bone formation and Osteoblast Differentiation through the bone-related genes.
Toshihisa Komori - One of the best experts on this subject based on the ideXlab platform.
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regulation of Osteoblast Differentiation by transcription factors
Journal of Cellular Biochemistry, 2006Co-Authors: Toshihisa KomoriAbstract:Runx2, osterix, and β-catenin are essential for Osteoblast Differentiation. Runx2 directs multipotent mesenchymal cells to an Osteoblastic lineage, and inhibits them from differentiating into the adipocytic and chondrocytic lineages. After differentiating to preOsteoblasts, β-catenin, osterix, and Runx2 direct them to immature Osteoblasts, which produce bone matrix proteins, blocking their potential to differentiate into the chondrocytic lineage. Runx2 inhibits Osteoblast maturation and the transition into osteocytes, keeping Osteoblasts in an immature stage. Other transcription factors including Msx1, Msx2, Dlx5, Dlx6, Twist, AP1(Fos/Jun), Knox-20, Sp3, and ATF4 are also involved in Osteoblast Differentiation. To gain an understanding of bone development, it is important to position these transcription factors to the right places in the processes of Osteoblast Differentiation. J. Cell. Biochem. 99: 1233–1239, 2006. © 2006 Wiley-Liss, Inc.
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regulation of Osteoblast Differentiation mediated by bone morphogenetic proteins hedgehogs and cbfa1
Endocrine Reviews, 2000Co-Authors: Akira Yamaguchi, Toshihisa Komori, Tatsuo SudaAbstract:Osteoblasts arise from common progenitors with chondrocytes, muscle and adipocytes, and various hormones and local factors regulate their Differentiation. We review here regulation of Osteoblast Differentiation mediated by the local factors such as bone morphogenetic proteins (BMPs) and hedgehogs and the transcription factor, core-binding factor α-1 (Cbfa1). BMPs are the most potent regulators of Osteoblast Differentiation among the local factors. Sonic and Indian hedgehogs are involved in Osteoblast Differentiation by interacting with BMPs. Cbfa1, a member of the runt domain gene family, plays a major role in the processes of a determination of Osteoblast cell lineage and maturation of Osteoblasts. Cbfa1 is an essential transcription factor for Osteoblast Differentiation and bone formation, because Cbfa1-deficient mice completely lacked bone formation due to maturation arrest of Osteoblasts. Although the regulatory mechanism of Cbfa1 expression has not been fully clarified, BMPs are an important local fa...
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Regulation of Osteoblast Differentiation mediated by bone morphogenetic proteins, hedgehogs, and Cbfa1
Endocrine Reviews, 2000Co-Authors: Akira Yamaguchi, Toshihisa Komori, Tatsuo SudaAbstract:Osteoblasts arise from common progenitors with chondrocytes, muscle and adipocytes, and various hormones and local factors regulate their Differentiation. We review here regulation of Osteoblast Differentiation mediated by the local factors such as bone morphogenetic proteins (BMPs) and hedgehogs and the transcription factor, core-binding factor α-1 (Cbfa1). BMPs are the most potent regulators of Osteoblast Differentiation among the local factors. Sonic and Indian hedgehogs are involved in Osteoblast Differentiation by interacting with BMPs. Cbfa1, a member of the runt domain gene family, plays a major role in the processes of a determination of Osteoblast cell lineage and maturation of Osteoblasts. Cbfa1 is an essential transcription factor for Osteoblast Differentiation and bone formation, because Cbfa1-deficient mice completely lacked bone formation due to maturation arrest of Osteoblasts. Although the regulatory mechanism of Cbfa1 expression has not been fully clarified, BMPs are an important local factor that up-regulates Cbfa1 expression. Thus, the intimate interaction between local factors such as BMPs and hedgehogs and the transcription factor, Cbfa1, is important to Osteoblast Differentiation and bone formation.
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cbfa1 isoforms exert functional differences in Osteoblast Differentiation
Journal of Biological Chemistry, 1999Co-Authors: Hideyuki Harada, Toshihisa Komori, Akira Yamaguchi, Shuzo Tagashira, Masanori Fujiwara, Shinji Ogawa, Takashi Katsumata, Masashi NakatsukaAbstract:Abstract Cbfa1 is an essential transcription factor for Osteoblast Differentiation and bone formation. We investigated functional differences among three isoforms of Cbfa1: Type I (originally reported as Pebp2αA by Ogawa et al. (Ogawa, E., Maruyama, M., Kagoshima, H., Inuzuka, M., Lu, J., Satake, M., Shigesada, K., and Ito, Y. (1993) Proc. Natl. Acad. Sci. U. S. A. 90, 6859–6863), Type II (originally reported astil-1 by Stewart et al. (Stewart, M., Terry, A., Hu, M., O’Hara, M., Blyth, K., Baxter, E., Cameron, E., Onions, D. E., and Neil, J. C. (1997) Proc. Natl. Acad. Sci. U. S. A. 94, 8646–8651), and Type III (originally reported asOsf2/Cbfa1 by Ducy et al. (Ducy, P., Zhang, R., Geoffroy, V., Ridall, A. L., and Karsenty, G. (1997)Cell 89, 747–754). A reverse transcriptase-polymerase chain reaction analysis demonstrated that these isoforms were expressed in adult mouse bones. The transient transfection of Type I or Type IICbfa1 in a mouse fibroblastic cell line, C3H10T1/2, induced the expression of alkaline phosphatase (ALP) activity. This induction was synergistically enhanced by the co-introduction ofXenopus BMP-4 cDNA. In contrast, the transient transfection of Type III cDNA induced no ALP activity. In C3H10T1/2 cells stably transfected with each isoform ofCbfa1, the gene expression of ALP was also strongly induced in cells transfected with Type I and Type IICbfa1 but not in cells with Type III Cbfa1. Osteocalcin, osteopontin,and type I collagen gene expressions were induced or up-regulated in all of the cells stably transfected with each isoform of Cbfa1, and Type II transfected cells exhibited the highest expression level ofosteocalcin gene. A luciferase reporter gene assay using a 6XOSE2-SV40 promoter (6 tandem binding elements for Cbfa1 ligated in front of the SV40 promoter sequence), a mouse osteocalcinpromoter, and a mouse osteopontin promoter revealed the differences in the transcriptional induction of target genes by eachCbfa1 isoform with or without its β-subunit. These results suggest that all three of the Cbfa1 isoforms used in the present study are involved in the stimulatory action of Osteoblast Differentiation, but they exert different functions in the process of Osteoblast Differentiation.
Clemens W.g.m. Löwik - One of the best experts on this subject based on the ideXlab platform.
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expression of vascular endothelial growth factors and their receptors during Osteoblast Differentiation
Endocrinology, 2000Co-Authors: Martine Deckers, Chris Van Der Bent, Takeyoshi Yamashita, Socrates E. Papapoulos, Marcel Karperien, Clemens W.g.m. LöwikAbstract:Endochondral bone formation is regulated by systemically and locally acting growth factors. A role for vascular endothelial growth factor (VEGF) in this process has recently been proposed, because inactivation of VEGF inhibits endochondral bone formation via inhibition of angiogenesis. Despite the known effect of VEGF as specific endothelial growth factor, its effects on Osteoblast Differentiation have not been studied. We, therefore, examined the expression of VEGF-A, -B, -C, and -D and their receptors in a model of Osteoblast Differentiation using the mouse preOsteoblast-like cell line KS483. Early in Differentiation, KS483 cells express low levels VEGF-A, -B, and -D messenger RNA, whereas during mineralization, KS483 cells express high levels. In addition, expression of the VEGF receptors, VEGFR1, VEGFR2, and VEGF165R/neuropilin, coincided with expression of their ligands, being maximally expressed during mineralization. VEGF-A production during Osteoblast Differentiation was stimulated by insulin-like...
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expression of vascular endothelial growth factors and their receptors during Osteoblast Differentiation
Endocrinology, 2000Co-Authors: Martine Deckers, Chris Van Der Bent, Takeyoshi Yamashita, Socrates E. Papapoulos, Marcel Karperien, Clemens W.g.m. LöwikAbstract:Endochondral bone formation is regulated by systemically and locally acting growth factors. A role for vascular endothelial growth factor (VEGF) in this process has recently been proposed, because inactivation of VEGF inhibits endochondral bone formation via inhibition of angiogenesis. Despite the known effect of VEGF as specific endothelial growth factor, its effects on Osteoblast Differentiation have not been studied. We, therefore, examined the expression of VEGF-A, -B, -C, and -D and their receptors in a model of Osteoblast Differentiation using the mouse preOsteoblast-like cell line KS483. Early in Differentiation, KS483 cells express low levels VEGF-A, -B, and -D messenger RNA, whereas during mineralization, KS483 cells express high levels. In addition, expression of the VEGF receptors, VEGFR1, VEGFR2, and VEGF165R/neuropilin, coincided with expression of their ligands, being maximally expressed during mineralization. VEGF-A production during Osteoblast Differentiation was stimulated by insulin-like...
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expression of vascular endothelial growth factors and their receptors during Osteoblast Differentiation
Endocrinology, 2000Co-Authors: Martine Deckers, Takeyoshi Yamashita, Socrates E. Papapoulos, Marcel Karperien, Chris Van Der Bent, Clemens W.g.m. LöwikAbstract:Endochondral bone formation is regulated by systemically and locally acting growth factors. A role for vascular endothelial growth factor (VEGF) in this process has recently been proposed, because inactivation of VEGF inhibits endochondral bone formation via inhibition of angiogenesis. Despite the known effect of VEGF as specific endothelial growth factor, its effects on Osteoblast Differentiation have not been studied. We, therefore, examined the expression of VEGF-A, -B, -C, and -D and their receptors in a model of Osteoblast Differentiation using the mouse preOsteoblast-like cell line KS483. Early in Differentiation, KS483 cells express low levels VEGF-A, -B, and -D messenger RNA, whereas during mineralization, KS483 cells express high levels. In addition, expression of the VEGF receptors, VEGFR1, VEGFR2, and VEGF165R/neuropilin, coincided with expression of their ligands, being maximally expressed during mineralization. VEGF-A production during Osteoblast Differentiation was stimulated by insulin-like growth factor I that enhances Osteoblast Differentiation and was inhibited by PTH-related peptide that inhibits Osteoblast Differentiation. Furthermore, continuous treatment of KS483 cells with recombinant human VEGF-A stimulated nodule formation. Although treatment of KS483 cells with soluble FLT1, an agent that blocks binding of VEGF-A and -B to VEGFR1, did not inhibit nodule formation, this observation does not exclude involvement of VEGFR2 in the regulation of Osteoblast Differentiation. As it is known that VEGF-A, -C, and -D can act through activation of VEGFR2, other isoforms might compensate for VEGF-A loss. The expression pattern of VEGFs and their receptors shown here suggests that VEGFs play an important role in the regulation of bone remodeling by attracting endothelial cells and osteoclasts and by stimulating Osteoblast Differentiation.
Akira Yamaguchi - One of the best experts on this subject based on the ideXlab platform.
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ihh gli2 signaling promotes Osteoblast Differentiation by regulating runx2 expression and function
Molecular Biology of the Cell, 2007Co-Authors: Atsuko Shimoyama, Akira Yamaguchi, Masahiro Wada, Fumiyo Ikeda, Kenji Hata, Takuma Matsubara, Akira Nifuji, Masaki Noda, Katsuhiko Amano, Riko NishimuraAbstract:Genetic and cell biological studies have indicated that Indian hedgehog (Ihh) plays an important role in bone development and Osteoblast Differentiation. However, the molecular mechanism by which Ihh regulates Osteoblast Differentiation is complex and remains to be fully elucidated. In this study, we investigated the role of Ihh signaling in Osteoblast Differentiation using mesenchymal cells and primary Osteoblasts. We observed that Ihh stimulated alkaline phosphatase (ALP) activity, osteocalcin expression, and calcification. Overexpression of Gli2- but not Gli3-induced ALP, osteocalcin expression, and calcification of these cells. In contrast, dominant-negative Gli2 markedly inhibited Ihh-dependent Osteoblast Differentiation. Ihh treatment or Gli2 overexpression also up-regulated the expression of Runx2, an essential transcription factor for Osteoblastogenesis, and enhanced the transcriptional activity and osteogenic action of Runx2. Coimmunoprecipitation analysis demonstrated a physical interaction between Gli2 and Runx2. Moreover, Ihh or Gli2 overexpression failed to increase ALP activity in Runx2-deficient mesenchymal cells. Collectively, these results suggest that Ihh regulates Osteoblast Differentiation of mesenchymal cells through up-regulation of the expression and function of Runx2 by Gli2.
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regulation of Osteoblast Differentiation mediated by bone morphogenetic proteins hedgehogs and cbfa1
Endocrine Reviews, 2000Co-Authors: Akira Yamaguchi, Toshihisa Komori, Tatsuo SudaAbstract:Osteoblasts arise from common progenitors with chondrocytes, muscle and adipocytes, and various hormones and local factors regulate their Differentiation. We review here regulation of Osteoblast Differentiation mediated by the local factors such as bone morphogenetic proteins (BMPs) and hedgehogs and the transcription factor, core-binding factor α-1 (Cbfa1). BMPs are the most potent regulators of Osteoblast Differentiation among the local factors. Sonic and Indian hedgehogs are involved in Osteoblast Differentiation by interacting with BMPs. Cbfa1, a member of the runt domain gene family, plays a major role in the processes of a determination of Osteoblast cell lineage and maturation of Osteoblasts. Cbfa1 is an essential transcription factor for Osteoblast Differentiation and bone formation, because Cbfa1-deficient mice completely lacked bone formation due to maturation arrest of Osteoblasts. Although the regulatory mechanism of Cbfa1 expression has not been fully clarified, BMPs are an important local fa...
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Regulation of Osteoblast Differentiation mediated by bone morphogenetic proteins, hedgehogs, and Cbfa1
Endocrine Reviews, 2000Co-Authors: Akira Yamaguchi, Toshihisa Komori, Tatsuo SudaAbstract:Osteoblasts arise from common progenitors with chondrocytes, muscle and adipocytes, and various hormones and local factors regulate their Differentiation. We review here regulation of Osteoblast Differentiation mediated by the local factors such as bone morphogenetic proteins (BMPs) and hedgehogs and the transcription factor, core-binding factor α-1 (Cbfa1). BMPs are the most potent regulators of Osteoblast Differentiation among the local factors. Sonic and Indian hedgehogs are involved in Osteoblast Differentiation by interacting with BMPs. Cbfa1, a member of the runt domain gene family, plays a major role in the processes of a determination of Osteoblast cell lineage and maturation of Osteoblasts. Cbfa1 is an essential transcription factor for Osteoblast Differentiation and bone formation, because Cbfa1-deficient mice completely lacked bone formation due to maturation arrest of Osteoblasts. Although the regulatory mechanism of Cbfa1 expression has not been fully clarified, BMPs are an important local factor that up-regulates Cbfa1 expression. Thus, the intimate interaction between local factors such as BMPs and hedgehogs and the transcription factor, Cbfa1, is important to Osteoblast Differentiation and bone formation.
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cbfa1 isoforms exert functional differences in Osteoblast Differentiation
Journal of Biological Chemistry, 1999Co-Authors: Hideyuki Harada, Toshihisa Komori, Akira Yamaguchi, Shuzo Tagashira, Masanori Fujiwara, Shinji Ogawa, Takashi Katsumata, Masashi NakatsukaAbstract:Abstract Cbfa1 is an essential transcription factor for Osteoblast Differentiation and bone formation. We investigated functional differences among three isoforms of Cbfa1: Type I (originally reported as Pebp2αA by Ogawa et al. (Ogawa, E., Maruyama, M., Kagoshima, H., Inuzuka, M., Lu, J., Satake, M., Shigesada, K., and Ito, Y. (1993) Proc. Natl. Acad. Sci. U. S. A. 90, 6859–6863), Type II (originally reported astil-1 by Stewart et al. (Stewart, M., Terry, A., Hu, M., O’Hara, M., Blyth, K., Baxter, E., Cameron, E., Onions, D. E., and Neil, J. C. (1997) Proc. Natl. Acad. Sci. U. S. A. 94, 8646–8651), and Type III (originally reported asOsf2/Cbfa1 by Ducy et al. (Ducy, P., Zhang, R., Geoffroy, V., Ridall, A. L., and Karsenty, G. (1997)Cell 89, 747–754). A reverse transcriptase-polymerase chain reaction analysis demonstrated that these isoforms were expressed in adult mouse bones. The transient transfection of Type I or Type IICbfa1 in a mouse fibroblastic cell line, C3H10T1/2, induced the expression of alkaline phosphatase (ALP) activity. This induction was synergistically enhanced by the co-introduction ofXenopus BMP-4 cDNA. In contrast, the transient transfection of Type III cDNA induced no ALP activity. In C3H10T1/2 cells stably transfected with each isoform ofCbfa1, the gene expression of ALP was also strongly induced in cells transfected with Type I and Type IICbfa1 but not in cells with Type III Cbfa1. Osteocalcin, osteopontin,and type I collagen gene expressions were induced or up-regulated in all of the cells stably transfected with each isoform of Cbfa1, and Type II transfected cells exhibited the highest expression level ofosteocalcin gene. A luciferase reporter gene assay using a 6XOSE2-SV40 promoter (6 tandem binding elements for Cbfa1 ligated in front of the SV40 promoter sequence), a mouse osteocalcinpromoter, and a mouse osteopontin promoter revealed the differences in the transcriptional induction of target genes by eachCbfa1 isoform with or without its β-subunit. These results suggest that all three of the Cbfa1 isoforms used in the present study are involved in the stimulatory action of Osteoblast Differentiation, but they exert different functions in the process of Osteoblast Differentiation.
