Smad7 Inhibits Chondrocyte Differentiation at Multiple Steps during Endochondral Bone Formation and Down-regulates p38 MAPK Pathways

Iwai, Tomohiro; Murai, Junko; Yoshikawa, Hideki; Tsumaki, Noriyuki

doi:10.1074/jbc.m801175200

Cited by 68 publications

(70 citation statements)

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“…Consistent with our findings showing the critical roles of BMP2/Cdc42/p38 signaling in mesenchymal condensation, a previous study in osteoblastic cells demonstrated that p38 was activated in response to BMP2 treatment and that inhibition of p38 activity suppressed BMP2-induced Smad1 phosphorylation as well as its translocation to the nucleus (Noth et al 2003). Similarly, another previous study indicated that overexpression of Sma7 in mesenchymal progenitors (Prx1Cre) led to disturbed mesenchymal condensation associated with decreased Sox9 expression and poor cartilage formation by down-regulating the BMP-activated p38 pathway (Iwai et al 2008). TGF-b signals through Smad2/3 to interact with Sox9 and induces Sox9 transactivity; alternatively, TGF-b recruits the transcriptional coactivators CBP/p300 to increase Sox9 transactivity (Furumatsu et al 2005;Kozhemyakina et al 2015).…”

Section: Discussionmentioning

confidence: 99%

Signaling Cascades Governing Cdc42-Mediated Chondrogenic Differentiation and Mensenchymal Condensation

Wang

et al. 2016

Genetics

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Endochondral ossification consists of successive steps of chondrocyte differentiation, including mesenchymal condensation, differentiation of chondrocytes, and hypertrophy followed by mineralization and ossification. Loss-of-function studies have revealed that abnormal growth plate cartilage of the Cdc42 mutant contributes to the defects in endochondral bone formation. Here, we have investigated the roles of Cdc42 in osteogenesis and signaling cascades governing Cdc42-mediated chondrogenic differentiation. Though deletion of Cdc42 in limb mesenchymal progenitors led to severe defects in endochondral ossification, either ablation of Cdc42 in limb preosteoblasts or knockdown of Cdc42 in vitro had no obvious effects on bone formation and osteoblast differentiation. However, in Cdc42 mutant limb buds, loss of Cdc42 in mesenchymal progenitors led to marked inactivation of p38 and Smad1/5, and in micromass cultures, Cdc42 lay on the upstream of p38 to activate Smad1/5 in bone morphogenetic protein-2-induced mesenchymal condensation. Finally, Cdc42 also lay on the upstream of protein kinase B to transactivate Sox9 and subsequently induced the expression of chondrocyte differential marker in transforming growth factor-b1-induced chondrogenesis. Taken together, by using biochemical and genetic approaches, we have demonstrated that Cdc42 is involved not in osteogenesis but in chondrogenesis in which the BMP2/Cdc42/Pak/p38/Smad signaling module promotes mesenchymal condensation and the TGF-b/Cdc42/Pak/Akt/Sox9 signaling module facilitates chondrogenic differentiation. KEYWORDS Cdc42; condensation; osteoblast; chondrocyte S EVERAL successive steps, including mesenchymal condensation of undifferentiated cells, chondrocyte differentiation, proliferation of chondrocytes, and differentiation into hypertrophic chondrocytes followed by mineralization and ossification, exist in the process of endochondral ossification (Long and Ornitz 2013). Mesenchymal condensation is a prerequisite for chondrogenesis and is facilitated by cell adhesion molecules. Upregulation of cell adhesion proteins such as N-cadherin is a hallmark of condensing cells, whereas loss of cell adhesion molecules is able to abolish condensation (Delise and Tuan 2002;Bobick et al. 2009). The molecular mechanisms governing condensation are not fully understood, though several genes have been implicated in this process such as bone morphogenic proteins (BMPs) and SRY (sex determining region Y)-box 9 (Sox9) (Fromental-Ramain et al. 1996;Wada et al. 1998;Lu et al. 2008). Conditional inactivationof Sox9 in limb mesenchymal progenitors leads to the absence of condensations, while simultaneous deletion of Bmp2 and Bmp4 in limb mesenchymes leads to the loss of zeugopod elements and to defective joint articulations (Reversade et al. 2005). During endochondral ossification, condensed cells undergo the differentiation into chondrocytes that secrete an abundance of cartilage matrices including types II, IX, and XI collagen. Sox9 is also the earliest known transcription...

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Section: Discussionmentioning

confidence: 99%

Signaling Cascades Governing Cdc42-Mediated Chondrogenic Differentiation and Mensenchymal Condensation

Wang

et al. 2016

Genetics

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“…Generation of 11Prom-Cre; Sox9 flox/flox conditional knockout mice We intercrossed 11Prom-Cre mice (Iwai et al, 2008) with Sox9 flox/flox mice (Akiyama et al, 2002) to examine Sox9 function in chondrocytes at a later stage of differentiation. 11Prom-Cre; Sox9 flox/+ mice were recovered with the expected Mendelian frequency (see Fig.…”

Section: Resultsmentioning

confidence: 99%

“…We recently generated two types of transgenic mice in which Cre is expressed at different steps during chondrocyte differentiation (Iwai et al, 2008). In 11Enh-Cre transgenic mice, Cre recombinase activities are controlled by the Col11a2 promoter and enhancer and begin during the round chondrocyte stage.…”

Section: Sox9mentioning

confidence: 99%

“…To generate Sox9 conditional knockout mice, 11Enh-Cre transgenic mice, 11Prom-Cre transgenic mice (Iwai et al, 2008) and Sox9 flox/flox mice (Akiyama et al, 2002) were prepared and mated. To generate Sox9; Pten double conditional knockout mice, Pten flox/flox mice ) were prepared.…”

Section: Animals and Genotypingmentioning

confidence: 99%

“…To generate Sox9; Pten double conditional knockout mice, Pten flox/flox mice ) were prepared. For genotyping, genomic DNA was isolated from tail tips or embryonic skin and subjected to PCR analysis according to the methods previously described for the Cre transgene (Iwai et al, 2008), Sox9 allele (Akiyama et al, 2002) and Pten allele ).…”

Section: Animals and Genotypingmentioning

confidence: 99%

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Sox9 sustains chondrocyte survival and hypertrophy in part through Pik3ca-Akt pathways

et al. 2011

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SUMMARYDuring endochondral bone formation, Sox9 expression starts in mesenchymal progenitors, continues in the round and flat chondrocyte stages at high levels, and ceases just prior to the hypertrophic chondrocyte stage. Sox9 is important in mesenchymal progenitors for their differentiation into chondrocytes, but its functions post-differentiation have not been determined. To investigate Sox9 function in chondrocytes, we deleted mouse Sox9 at two different steps after chondrocyte differentiation. Sox9 inactivation in round chondrocytes resulted in a loss of Col2a1 expression and in apoptosis. Sox9 inactivation in flat chondrocytes caused immediate terminal maturation without hypertrophy and with excessive apoptosis. Inactivation of Sox9 in the last few cell layers resulted in the absence of Col10a1 expression, suggesting that continued expression of Sox9 just prior to hypertrophy is necessary for chondrocyte hypertrophy. SOX9 knockdown also caused apoptosis of human chondrosarcoma SW1353 cells. These phenotypes were associated with reduced Akt phosphorylation. Forced phosphorylation of Akt by Pten inactivation partially restored Col10a1 expression and cell survival in Sox9 floxdel/floxdel mouse chondrocytes, suggesting that phosphorylated Akt mediates chondrocyte survival and hypertrophy induced by Sox9. When the molecular mechanism of Sox9-induced Akt phosphorylation was examined, we found that expression of the PI3K subunit Pik3ca (p110) was decreased in Sox9 floxdel/floxdel mouse chondrocytes. Sox9 binds to the promoter and enhances the transcriptional activities of Pik3ca. Thus, continued expression of Sox9 in differentiated chondrocytes is essential for subsequent hypertrophy and sustains chondrocyte-specific survival mechanisms by binding to the Pik3ca promoter, inducing Akt phosphorylation.

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The chondrocytic journey in endochondral bone growth and skeletal dysplasia

Tsang

Chan

et al. 2014

Birth Defects Research Pt C

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The endochondral bones of the skeleton develop from a cartilage template and grow via a process involving a cascade of chondrocyte differentiation steps culminating in formation of a growth plate and the replacement of cartilage by bone. This process of endochondral ossification, driven by the generation of chondrocytes and their subsequent proliferation, differentiation, and production of extracellular matrix constitute a journey, deviation from which inevitably disrupts bone growth and development, and is the basis of human skeletal dysplasias with a wide range of phenotypic severity, from perinatal lethality to progressively deforming. This highly coordinated journey of chondrocyte specification and fate determination is controlled by a myriad of intrinsic and extrinsic factors. SOX9 is the master transcription factor that, in concert with varying partners along the way, directs the different phases of the journey from mesenchymal condensation, chondrogenesis, differentiation, proliferation, and maturation. Extracellular signals, including bone morphogenetic proteins, wingless-related MMTV integration site (WNT), fibroblast growth factor, Indian hedgehog, and parathyroid hormone-related peptide, are all indispensable for growth plate chondrocytes to align and organize into the appropriate columnar architecture and controls their maturation and transition to hypertrophy. Chondrocyte hypertrophy, marked by dramatic volume increase in phases, is controlled by transcription factors SOX9, Runt-related transcription factor, and FOXA2. Hypertrophic chondrocytes mediate the cartilage to bone transition and concomitantly face a live-or-die situation, a subject of much debate. We review recent insights into the coordination of the phases of the chondrocyte journey, and highlight the need for a systems level understanding of the regulatory networks that will facilitate the development of therapeutic approaches for skeletal dysplasia.

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Smad7 Inhibits Chondrocyte Differentiation at Multiple Steps during Endochondral Bone Formation and Down-regulates p38 MAPK Pathways

Cited by 68 publications

References 45 publications

Signaling Cascades Governing Cdc42-Mediated Chondrogenic Differentiation and Mensenchymal Condensation

Signaling Cascades Governing Cdc42-Mediated Chondrogenic Differentiation and Mensenchymal Condensation

Sox9 sustains chondrocyte survival and hypertrophy in part through Pik3ca-Akt pathways

The chondrocytic journey in endochondral bone growth and skeletal dysplasia

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