Long-range activation of Sox9 in Odd Sex (Ods) mice

Qin, Yangjun; Kong, Lingkun; Poirier, Christophe; Truong, Cavatina K.; Overbeek, Paul A.; Bishop, Colin E.

doi:10.1093/hmg/ddh141

Cited by 95 publications

(78 citation statements)

References 27 publications

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“…Based on our findings, it would be of interest to determine whether SOX9 is a direct target of HIF-2␣ in human articular chondrocytes. However, analysis of recruited factors on the human SOX9 promoter is difficult because of the particular complexity of this promoter (29)(30)(31)(32), with important regulatory elements dispersed over a large region upstream of SOX9 (32). Furthermore, unlike the murine promoter, no HREs have been reported in the human SOX9 promoter (33).…”

Section: Discussionmentioning

confidence: 99%

Hypoxia‐inducible factor 2α is essential for hypoxic induction of the human articular chondrocyte phenotype

Lafont¹,

Talma²,

Murphy³

2007

Arthritis & Rheumatism

134

155

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Objective. To uncover the mechanism by which hypoxia enhances cartilage matrix synthesis by human articular chondrocytes.Methods. The hypoxic response was investigated by exposing normal (nonarthritic) human articular chondrocyte cultures to 20% oxygen and 1% oxygen. Induction of the differentiated phenotype was confirmed at the gene and protein levels. In its first reported application in human articular chondrocytes, the RNA interference method was used to directly investigate the role of specific transcription factors in this process. Small interfering RNA directed against hypoxiainducible factor 1␣ (HIF-1␣), HIF-2␣, and SOX9 were delivered by lipid-based transfection of primary and passaged human articular chondrocytes. The effect of each knockdown on hypoxic induction of the chondrocyte phenotype was assessed.Results. Hypoxia enhanced matrix synthesis and SOX9 expression of human articular chondrocytes at both the gene and protein levels. Although HIF-1␣ knockdown had no effect, depletion of HIF-2␣ abolished this hypoxic induction. Thus, we provide the first evidence that HIF-2␣, but not HIF-1␣, is essential for hypoxic induction of the human articular chondrocyte phenotype. In addition, depletion of SOX9 prevented hypoxic induction of matrix genes, indicating that the latter are not direct HIF targets but are up-regulated by hypoxia via SOX9.Conclusion. Based on our data, we propose a novel mechanism whereby hypoxia promotes cartilage matrix synthesis specifically through HIF-2␣-mediated SOX9 induction of key cartilage genes. These findings have potential application for the development of cartilage repair therapies.Being avascular, cartilage has a low oxygen concentration (1,2). Chondrocytes, the unique resident cells, are therefore adapted to these hypoxic conditions, e.g., by having lower levels of oxidative phosphorylation (3) and enhanced anaerobic glycolysis (4). Furthermore, recent studies suggest that hypoxia triggers essential positive signals for the chondrocyte phenotype beyond such survival responses. Indeed, we previously reported that reduced oxygen tension increases levels of the cartilage matrix genes COL2A1 and aggrecan and the cartilage transcription factor SOX9 in cultured articular chondrocytes (5,6). Domm and colleagues also showed a positive effect of hypoxia on Col␣1(II) levels in bovine chondrocytes (7). Hypoxia has been shown to promote chondrogenic differentiation of mesenchymal stem cells, and it was recently shown that the mouse Sox9 promoter is activated by hypoxia in mouse mesenchymal cells (8).In various cell types, hypoxic effects have been shown to be mediated by hypoxia-inducible factor (HIF) transcription factors. These proteins belong to the Per-ARNT-Sim (PAS) subfamily of basic helix-loop-helix (bHLH) transcription factors and consist of an ␣ subunit and a ␤ subunit (9). Under conditions of normoxia, HIF-1␣ is hydroxylated on specific proline residues, ubiquitinated through interaction with the von HippelLindau tumor suppressor protein, pVHL, and subsequently degraded b...

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Section: Discussionmentioning

confidence: 99%

Hypoxia‐inducible factor 2α is essential for hypoxic induction of the human articular chondrocyte phenotype

Lafont¹,

Talma²,

Murphy³

2007

Arthritis & Rheumatism

134

155

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“…In some cases, such as with Sox9 and Sonic hedgehog, distal regulatory elements were shown to act over genomic distances as great as 1Mb, even extending into neighboring genes (Bishop et al, 2000;Gottgens et al, 2000;Loots et al, 2000;Lettice et al, 2002;Qin et al, 2004;Zheng et al, 2004;Sagai et al, 2005). Knowing this, it is clear that criteria are needed to help select functional sequences from the massive amount of non-functional DNA.…”

Section: Discussionmentioning

confidence: 99%

Distal regulatory elements are required for Fshr expression, in vivo

Hermann

Hornbaker

Maran

et al. 2007

Molecular and Cellular Endocrinology

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The gonadotropin follicle-stimulating hormone (FSH) is required for initiation and maintenance of normal gametogenesis and acts through a specific, cell-surface receptor (Fshr) present only on Sertoli and granulosa cells in the gonads. Despite extensive examination of the transcriptional mechanisms regulating Fshr, the sequences directing its expression to these cells remain unidentified. To establish the minimal region necessary for Fshr expression, we generated transgenic mice carrying a yeast artificial chromosome (YAC) that contained 413 kilobases (kb) of the rat Fshr locus (YAC60). Transgene expression, as determined by RT-PCR, was absent from immature testis and Sertoli cells, limited to germ cells of the adult testis, and never observed in the ovary. While the data is limited to only one transgenic line, it suggests that the 413kb region does not specify the normal spatiotemporal expression pattern of Fshr. Comparative genomics was used to identify potential distal regulatory elements, revealing seven regions of high evolutionary conservation (≥80% identity over 100bp or more), six of which were absent from the transgene. Functional examination of the evolutionary conserved regions (ECRs) by transient transfection revealed that all of the ECRs had modest transcriptional activity in Sertoli or myoid cells with two, ECR4 and ECR5, showing differential effects in expressing and non-expressing cells. These data reveal that distal regulatory regions (outside the 413kb in YAC60) are required for appropriate temporal and spatial Fshr expression and implicate the identified ECRs in transcriptional regulation of Fshr.

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“…However, pinpointing the relevant regulatory sequences in the vicinity of Fshr presented a significant challenge given its size, the potential for regulatory elements to act at very large distance (i.e. as far 1 Mb), the lack of a defined, transcriptionally-competent locus for Fshr, and the knowledge that at least some important elements reside outside the region defined by the 413kb transgene (Bishop et al, 2000;Lettice et al, 2002;Qin et al, 2004;Sagai et al, 2005;Hermann et al, 2006). To facilitate the search, comparative genomics and DNase I hypersensitivity (DHS) mapping were employed to identify evolutionarily conserved and DNase I hypersensitive sequences, both hallmarks of transcriptional regulatory regions.…”

Section: B Identification Of Distal Fshr Regulatory Elementsmentioning

confidence: 99%

Transcriptional regulation of the FSH receptor: New perspectives

Hermann

Heckert

2007

Molecular and Cellular Endocrinology

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The cell-surface receptor for the gonadotropin follicle-stimulating hormone (FSH) is expressed exclusively on Sertoli cells of the testis and granulosa cells of the ovary. FSH signal transduction through its receptor (Fshr) is critical for the timing and maintenance of normal gametogenesis in the mammalian gonad. In the 13 years since the gene encoding Fshr was first cloned, the mechanisms controlling its transcription have been extensively examined, but a clear understanding of what drives its unique cell-specificity remains elusive. Current knowledge of basal Fshr transcription highlights the role of an E-box in the proximal promoter which is bound by the basic helix-loop-helix transcription factors upstream stimulatory factor 1 (Usf1) and Usf2. Recent studies utilizing knockout mice and chromatin immunoprecipitation validated the importance of Usf to Fshr transcription and demonstrated a sexually dimorphic requirement for the Usf proteins to maintain normal Fshr expression. Studies have also shown that the promoter region itself is insufficient for appropriate Fshr expression in transgenic mice, indicating Fshr transcription depends on regulatory elements that lie outside of the promoter. Identification of such elements has been propelled by recent availability of genome sequence data, which facilitated studies using comparative genomics, DNase I hypersensitivity mapping, and transgenic analysis with large fragments of DNA. This review will focus on the current understanding of transcriptional regulatory processes that control expression of rat Fshr, including recent advances from our laboratory.

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Long-range activation of Sox9 in Odd Sex (Ods) mice

Cited by 95 publications

References 27 publications

Hypoxia‐inducible factor 2α is essential for hypoxic induction of the human articular chondrocyte phenotype

Hypoxia‐inducible factor 2α is essential for hypoxic induction of the human articular chondrocyte phenotype

Distal regulatory elements are required for Fshr expression, in vivo

Transcriptional regulation of the FSH receptor: New perspectives

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