Ewing Sarcoma Eswa Protein Regulates Chondrogenesis of Meckel's Cartilage through Modulation of Sox9 in Zebrafish

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Issue Date
2015-01-24Author
Merkes, Chris M.
Turkalo, Timothy K.
Wilder, Nicole
Park, Hyewon
Wenger, Luke William
Lewin, Seth J.
Azuma, Mizuki
Publisher
Public Library of Science
Type
Article
Article Version
Scholarly/refereed, publisher version
Rights
© 2015 Merkes et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited
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Ewing sarcoma is the second most common skeletal (bone and cartilage) cancer in adolescents, and it is characterized by the expression of the aberrant chimeric fusion gene EWS/FLI1. Wild-type EWS has been proposed to play a role in mitosis, splicing and transcription. We have previously shown that EWS/FLI1 interacts with EWS, and it inhibits EWS activity in a dominant manner. Ewing sarcoma is a cancer that specifically develops in skeletal tissues, and although the above data suggests the significance of EWS, its role in chondrogenesis/skeletogenesis is not understood. To elucidate the function of EWS in skeletal development, we generated and analyzed a maternal zygotic (MZ) ewsa/ewsa line because the ewsa/wt and ewsa/ewsa zebrafish appeared to be normal and fertile. Compared with wt/wt, the Meckel’s cartilage of MZ ewsa/ewsa mutants had a higher number of craniofacial prehypertrophic chondrocytes that failed to mature into hypertrophic chondrocytes at 4 days post-fertilization (dpf). Ewsa interacted with Sox9, which is the master transcription factor for chondrogenesis. Sox9 target genes were either upregulated (ctgfa, ctgfb, col2a1a, and col2a1b) or downregulated (sox5, nog1, nog2, and bmp4) in MZ ewsa/ewsa embryos compared with the wt/wt zebrafish embryos. Among these Sox9 target genes, the chromatin immunoprecipitation (ChIP) experiment demonstrated that Ewsa directly binds to ctgfa and ctgfb loci. Consistently, immunohistochemistry showed that the Ctgf protein is upregulated in the Meckel’s cartilage of MZ ewsa/ewsa mutants. Together, we propose that Ewsa promotes the differentiation from prehypertrophic chondrocytes to hypertrophic chondrocytes of Meckel’s cartilage through inhibiting Sox9 binding site of the ctgf gene promoter. Because Ewing sarcoma specifically develops in skeletal tissue that is originating from chondrocytes, this new role of EWS may provide a potential molecular basis of its pathogenesis.
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Citation
Merkes C, Turkalo TK, Wilder N, Park H, Wenger LW, et al. (2015) Ewing Sarcoma Ewsa Protein Regulates Chondrogenesis of Meckel’s Cartilage through Modulation of Sox9 in Zebrafish. PLoS ONE 10(1): e0116627.
http://dx.doi.org/10.1371/journal.pone.0116627
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Except where otherwise noted, this item's license is described as: © 2015 Merkes et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited