Haploinsufficiency of SOX9 results in defective cartilage primordia and premature skeletal mineralization

Department of Molecular Genetics and Graduate Program in Genes and Development, M. D. Anderson Cancer Center, University of Texas, Houston, TX 77030, USA.
Proceedings of the National Academy of Sciences (Impact Factor: 9.67). 07/2001; 98(12):6698-703. DOI: 10.1073/pnas.111092198
Source: PubMed


In humans, SOX9 heterozygous mutations cause the severe skeletal dysmorphology syndrome campomelic dysplasia. Except for clinical descriptions, little is known about the pathogenesis of this disease. We have generated heterozygous Sox9 mutant mice that phenocopy most of the skeletal abnormalities of this syndrome. The Sox9(+/-) mice died perinatally with cleft palate, as well as hypoplasia and bending of many skeletal structures derived from cartilage precursors. In embryonic day (E)14.5 heterozygous embryos, bending of radius, ulna, and tibia cartilages was already prominent. In E12.5 heterozygotes, all skeletal elements visualized by using Alcian blue were smaller. In addition, the overall levels of Col2a1 RNA at E10.5 and E12.5 were lower than in wild-type embryos. We propose that the skeletal abnormalities observed at later embryonic stages were caused by delayed or defective precartilaginous condensations. Furthermore, in E18.5 embryos and in newborn heterozygotes, premature mineralization occurred in many bones, including vertebrae and some craniofacial bones. Because Sox9 is not expressed in the mineralized portion of the growth plate, this premature mineralization is very likely the consequence of allele insufficiency existing in cells of the growth plate that express Sox9. Because the hypertrophic zone of the heterozygous Sox9 mutants was larger than that of wild-type mice, we propose that Sox9 also has a role in regulating the transition to hypertrophic chondrocytes in the growth plate. Despite the severe hypoplasia of cartilages, the overall organization and cellular composition of the growth plate were otherwise normal. Our results suggest the hypothesis that two critical steps of the chondrocyte differentiation pathway are sensitive to Sox9 dosage. First, an early step presumably at the stage of mesenchymal condensation of cartilage primordia, and second, a later step preceding the transition of chondrocytes into hypertrophic chondrocytes.

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Available from: Deanne J Whitworth, Sep 03, 2014
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    • "Sox9 expression is also necessary to sustain chondrocyte survival through a PI3K- AKT pathway (Ikegami et al., 2011; Dy et al., 2012) and has been noted to block chondrocyte maturation into hypertrophic cells. Sox9 loss of function leads to premature maturation of immature chondrocytes into hypertrophic cells (Bi et al., 2001; Akiyama et al., 2002). Conversely, overexpression of Sox9 in either immature or hypertrophic chondrocytes of the growth plate slows the process of chondrocyte hypertrophy (Akiyama et al., 2004). "
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    ABSTRACT: Decades of work have identified the signaling pathways that regulate the differentiation of chondrocytes during bone formation, from their initial induction from mesenchymal progenitor cells to their terminal maturation into hypertrophic chondrocytes. Here, we review how multiple signaling molecules, mechanical signals and morphological cell features are integrated to activate a set of key transcription factors that determine and regulate the genetic program that induces chondrogenesis and chondrocyte differentiation. Moreover, we describe recent findings regarding the roles of several signaling pathways in modulating the proliferation and maturation of chondrocytes in the growth plate, which is the 'engine' of bone elongation. © 2015. Published by The Company of Biologists Ltd.
    Development 03/2015; 142(5):817-831. DOI:10.1242/dev.105536 · 6.46 Impact Factor
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    • "Several lines of evidence indicate that the transcription factor SOX9 acts as a master regulatory factor in this multistep pathway of chondrocyte differentiation [1], [2]. Heterozygous mutations in Sox9 cause campomelic dysplasia, a generalized and severe disease of cartilage characterized by hypoplasia of endochondral bone [3], [4]. A related disease called Pierre Robin sequence, which mainly affects the craniofacial skeleton, is associated with mutations in conserved DNA elements on either side of the Sox9 gene [5]. "
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    ABSTRACT: The transcription factor SOX9 plays an essential role in determining the fate of several cell types and is a master factor in regulation of chondrocyte development. Our aim was to determine which genes in the genome of chondrocytes are either directly or indirectly controlled by SOX9. We used RNA-Seq to identify genes whose expression levels were affected by SOX9 and used SOX9 ChIP-Seq to identify those genes that harbor SOX9-interaction sites. For RNA-Seq, the RNA expression profile of primary Sox9flox/flox mouse chondrocytes infected with Ad-CMV-Cre was compared with that of the same cells infected with a control adenovirus. Analysis of RNA-Seq data indicated that, when the levels of Sox9 mRNA were decreased more than 8-fold by infection with Ad-CMV-Cre, 196 genes showed a decrease in expression of at least 4-fold. These included many cartilage extracellular matrix (ECM) genes and a number of genes for ECM modification enzymes (transferases), membrane receptors, transporters, and others. In ChIP-Seq, 75% of the SOX9-interaction sites had a canonical inverted repeat motif within 100 bp of the top of the peak. SOX9-interaction sites were found in 55% of the genes whose expression was decreased more than 8-fold in SOX9-depleted cells and in somewhat fewer of the genes whose expression was reduced more than 4-fold, suggesting that these are direct targets of SOX9. The combination of RNA-Seq and ChIP-Seq has provided a fuller understanding of the SOX9-controlled genetic program of chondrocytes.
    PLoS ONE 09/2014; 9(9):e107577. DOI:10.1371/journal.pone.0107577 · 3.23 Impact Factor
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    • "The ABC transporters are essential for many processes in the cell, driving the transport of various molecules through ATP hydrolysis (Dean et al., 2001). Previously associated with embryo development (Asou et al., 2002), the sex determining region Y box 9 gene (SOX9) causes severe bone defects and perinatal death in heterozygous mutant mice (Bi et al., 2001). The general but important activity of the ABC gene superfamily and the role of SOX9 on prenatal development make these "
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    ABSTRACT: Porcine reproductive and respiratory syndrome (PRRS) is the most economically significant disease impacting pig production in North America, Europe, and Asia, causing reproductive losses such as increased rates stillbirth and mummified piglets. The objective of this study was to explore the genetic basis of host response to the PRRS virus (PRRSV) in a commercial multiplier sow herd before and after a PRRS outbreak, using antibody response and reproductive traits. Reproductive data comprising number born alive (NBA), number alive at 24h (NA24), number stillborn (NSB), number born mummified (NBM), proportion born dead (PBD), number born dead (NBD), number weaned (NW), and number mortalities through weaning (MW) of 5,227 litters from 1,967 purebred Landrace sows, were used along with a pedigree comprising 2,995 pigs. The PRRS outbreak date was estimated from rolling averages of farrowing traits and used to split the data in a pre-PRRS phase and a PRRS phase. All 641 sows in the herd during the outbreak were blood sampled 46 days after the estimated outbreak date, and were tested for anti-PRRSV IgG using ELISA (sample-to-positive [S/P] ratio). Genetic parameters of traits were estimated separately for the pre-PRRS and PRRS phase data sets. Sows were genotyped using the PorcineSNP60 BeadChip, and genome-wide association studies (GWAS) were performed using method Bayes-B. Heritability estimates for reproductive traits ranged from 0.01 (NBM) to 0.12 (NSB), and from 0.01 (MW) to 0.12 (NBD) for the pre-PRRS and PRRS phases, respectively. S/P ratio had heritability (0.45) and strong genetic correlations with most traits, ranging from -0.72 (NBM) to 0.73 (NBA). In the pre-PRRS phase, regions associated with NSB and PBD explained 1.6% and 3% of the genetic variance, respectively. In the PRRS phase, regions associated with NBD, NSB, and S/P ratio explained 0.8%, 11%, and 50.6% of the genetic variance, respectively. For S/P ratio, two regions on SSC7 separated by 100 Mb explained 40% of the genetic variation, including a region encompassing the Major Histocompatibility Complex, which explained 25% of the genetic variance. These results indicate a significant genomic component associated with PRRSV antibody response and NSB in this dataset. Also, the high heritability and genetic correlation estimates for S/P ratio during the PRRS phase suggest that S/P ratio could be used as an indicator of the impact of PRRS on reproductive traits.
    Journal of Animal Science 05/2014; 92(7). DOI:10.2527/jas.2014-7821 · 2.11 Impact Factor
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