title: Communication-dependent mineralization of osteoblasts via gap junctions.
abstract: Connexin43 (Cx43) is a major gap junction (GJ) protein in bone and plays a critical role in osteoblast differentiation. Several studies show that osteoblast differentiation is delayed by Cx43 ablation. However, the precise mechanism underlying the role of Cx43 in osteoblast differentiation is not fully understood. Firstly, we analyzed the phenotype of a conditional knockout mouse, which was generated by mating of an osterix promoter-driven Cre expressing mouse with a Cx43-floxed mouse. As expected, delayed ossification was observed. Secondly, we demonstrated that the cell communication via gap junctions played an important role in osteoblast differentiation using a tamoxifen-inducible knockout system in vitro. Genetic ablation of Cx43 resulted in both the disruption of cell-communications and the attenuation of osteoblast mineralization induced by BMP-2, but not by ascorbic acid. Moreover, restoring full-length Cx43 (382aa) expression rescued the impairment of osteoblast cell-communication and osteoblast mineralization; however, the expression of the Cx43 N-terminal mutant (382aaG2V) did not rescue either of them. Comparing the gene expression profiles, the genes directly regulated by BMP-2 were attenuated by Cx43 gene ablation. These results suggested that the cell-communication mediated by gap junctions was indispensable for normal differentiation of osteoblast induced by BMP-2.
authors.affiliation: Section of Cellular Physiological Chemistry, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, Japan; Section of Maxillofacial Surgery, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, Japan; Global Center of Excellence (GCOE) Program, International Research Center for Molecular Science in Tooth and Bone Diseases, Tokyo Medical and Dental University, Japan.
authors.forename: Yukihiko
authors.initials: Y
authors.lastname: Hashida
authors.affiliation: Section of Cellular Physiological Chemistry, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, Japan. Electronic address: nakacell@tmd.ac.jp.
authors.forename: Ken-ichi
authors.initials: K
authors.lastname: Nakahama
authors.affiliation: Section of Cellular Physiological Chemistry, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, Japan; Section of Oral Implantology and Regenerative Dental Medicine, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, Japan.
authors.forename: Kaori
authors.initials: K
authors.lastname: Shimizu
authors.affiliation: Section of Cellular Physiological Chemistry, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, Japan.
authors.forename: Masako
authors.initials: M
authors.lastname: Akiyama
authors.affiliation: Section of Maxillofacial Surgery, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, Japan.
authors.forename: Kiyoshi
authors.initials: K
authors.lastname: Harada
authors.affiliation: Section of Cellular Physiological Chemistry, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, Japan; Global Center of Excellence (GCOE) Program, International Research Center for Molecular Science in Tooth and Bone Diseases, Tokyo Medical and Dental University, Japan.
authors.forename: Ikuo
authors.initials: I
authors.lastname: Morita
mesh_terms: D000818:Animals; D015153:Blotting, Western; D055396:Bone Morphogenetic Protein 2 / Q000378:metabolism; D002450:Cell Communication / Q000502:physiology*; D002454:Cell Differentiation / Q000502:physiology; D018031:Connexin 43 / Q000378:metabolism*; D017629:Gap Junctions / Q000378:metabolism*; D005786:Gene Expression Regulation; D051379:Mice; D018345:Mice, Knockout; D020411:Oligonucleotide Array Sequence Analysis; D010006:Osteoblasts / Q000166:cytology / Q000378:metabolism*; D010012:Osteogenesis / Q000502:physiology*; D060888:Real-Time Polymerase Chain Reaction; D014162:Transfection
chemical_list: C525719:Bmp2 protein, mouse; D055396:Bone Morphogenetic Protein 2; D018031:Connexin 43; C543076:GJA1 protein, mouse
keywords: BMP-2; Bone; Cell-communication; Connexin43; Osteoblast