title: Identification and characterization of the novel Col10a1 regulatory mechanism during chondrocyte hypertrophic differentiation.
abstract: The majority of human skeleton develops through the endochondral pathway, in which cartilage-forming chondrocytes proliferate and enlarge into hypertrophic chondrocytes that eventually undergo apoptosis and are replaced by bone. Although at a terminal differentiation stage, hypertrophic chondrocytes have been implicated as the principal engine of bone growth. Abnormal chondrocyte hypertrophy has been seen in many skeletal dysplasia and osteoarthritis. Meanwhile, as a specific marker of hypertrophic chondrocytes, the type X collagen gene (COL10A1) is also critical for endochondral bone formation, as mutation and altered COL10A1 expression are often accompanied by abnormal chondrocyte hypertrophy in many skeletal diseases. However, how the type X collagen gene is regulated during chondrocyte hypertrophy has not been fully elucidated. We have recently demonstrated that Runx2 interaction with a 150-bp mouse Col10a1 cis-enhancer is required but not sufficient for its hypertrophic chondrocyte-specific reporter expression in transgenic mice, suggesting requirement of additional Col10a1 regulators. In this study, we report in silico sequence analysis of this 150-bp enhancer and identification of its multiple binding factors, including AP1, MEF2, NFAT, Runx1 and TBX5. Using this enhancer as bait, we performed yeast one-hybrid assay and identified multiple candidate Col10a1-interacting genes, including cyclooxygenase 1 (Cox-1) and Cox-2. We have also performed mass spectrometry analysis and detected EF1-alpha, Fus, GdF7 and Runx3 as components of the specific complex formed by the cis-enhancer and nuclear extracts from hypertrophic MCT (mouse chondrocytes immortalized with large T antigen) cells that express Col10a1 abundantly. Notably, some of the candidate genes are differentially expressed in hypertrophic MCT cells and have been associated with chondrocyte hypertrophy and Runx2, an indispensible Col10a1 regulator. Intriguingly, we detected high-level Cox-2 expression in hypertrophic MCT cells. Electrophoretic mobility shift assay and chromatin immunoprecipitation assays confirmed the interaction between Cox-2 and Col10a1 cis-enhancer, supporting its role as a candidate Col10a1 regulator. Together, our data support a Cox-2-containing, Runx2-centered Col10a1 regulatory mechanism, during chondrocyte hypertrophic differentiation.
authors.affiliation: Department of Hematology and Hematological Laboratory Science, School of Medical Science and Laboratory Medicine, Jiangsu University, Zhenjiang, China.
authors.forename: J
authors.initials: J
authors.lastname: Gu
authors.affiliation: 1] Department of Hematology and Hematological Laboratory Science, School of Medical Science and Laboratory Medicine, Jiangsu University, Zhenjiang, China [2] Department of Anatomy and Cell Biology, Rush University Medical Center, Chicago, IL, USA.
authors.forename: Y
authors.initials: Y
authors.lastname: Lu
authors.affiliation: Department of Pathophysiology, Anhui Medical University, Hefei, China.
authors.forename: F
authors.initials: F
authors.lastname: Li
authors.affiliation: Department of Hematology and Hematological Laboratory Science, School of Medical Science and Laboratory Medicine, Jiangsu University, Zhenjiang, China.
authors.forename: L
authors.initials: L
authors.lastname: Qiao
authors.affiliation: Department of Hematology and Hematological Laboratory Science, School of Medical Science and Laboratory Medicine, Jiangsu University, Zhenjiang, China.
authors.forename: Q
authors.initials: Q
authors.lastname: Wang
authors.affiliation: Department of Hematology and Hematological Laboratory Science, School of Medical Science and Laboratory Medicine, Jiangsu University, Zhenjiang, China.
authors.forename: N
authors.initials: N
authors.lastname: Li
authors.affiliation: Department of Pathology and Department of Biochemistry, Rush University Medical Center, Chicago, IL, USA.
authors.forename: J A
authors.initials: JA
authors.lastname: Borgia
authors.affiliation: Department of Internal Medicine and Biochemistry, Rush University Medical Center, Chicago, IL, USA.
authors.forename: Y
authors.initials: Y
authors.lastname: Deng
authors.affiliation: Department of Orthopaedic Surgery, Xiangya Hospital, Central South University, Changsha, China.
authors.forename: G
authors.initials: G
authors.lastname: Lei
authors.affiliation: 1] Department of Hematology and Hematological Laboratory Science, School of Medical Science and Laboratory Medicine, Jiangsu University, Zhenjiang, China [2] Department of Anatomy and Cell Biology, Rush University Medical Center, Chicago, IL, USA.
authors.forename: Q
authors.initials: Q
authors.lastname: Zheng
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D002454:Cell Differentiation / Q000235:genetics; D019902:Chondrocytes / Q000378:metabolism* / Q000473:pathology*; D024121:Collagen Type X / Q000737:chemistry / Q000235:genetics*; D019295:Computational Biology; D051546:Cyclooxygenase 2 / Q000378:metabolism; D004742:Enhancer Elements, Genetic / Q000235:genetics; D005786:Gene Expression Regulation; D056726:Genetic Association Studies; D006801:Humans; D006984:Hypertrophy; D013058:Mass Spectrometry; D051379:Mice; D008822:Mice, Transgenic; D008969:Molecular Sequence Data; D011485:Protein Binding; D014157:Transcription Factors / Q000378:metabolism; D020798:Two-Hybrid System Techniques
chemical_list: C570620:Col10a1 protein, mouse; D024121:Collagen Type X; D014157:Transcription Factors; C077623:Ptgs2 protein, mouse; D051546:Cyclooxygenase 2