title: SP7 inhibits osteoblast differentiation at a late stage in mice.
abstract: RUNX2 and SP7 are essential transcription factors for osteoblast differentiation at an early stage. Although RUNX2 inhibits osteoblast differentiation at a late stage, the function of SP7 at the late stage of osteoblast differentiation is not fully elucidated. Thus, we pursued the function of SP7 in osteoblast differentiation. RUNX2 induced Sp7 expression in Runx2(-/-) calvarial cells. Adenoviral transfer of sh-Sp7 into primary osteoblasts reduced the expression of Alpl, Col1a1, and Bglap2 and mineralization, whereas that of Sp7 reduced Bglap2 expression and mineralization at a late stage of osteoblast differentiation. Sp7 transgenic mice under the control of 2.3 kb Col1a1 promoter showed osteopenia and woven-bone like structure in the cortical bone, which was thin and less mineralized, in a dose-dependent manner. Further, the number of processes in the osteoblasts and osteocytes was reduced. Although the osteoblast density was increased, the bone formation was reduced. The frequency of BrdU incorporation was increased in the osteoblastic cells, while the expression of Col1a1, Spp1, Ibsp, and Bglap2 was reduced. Further, the osteopenia in Sp7 or Runx2 transgenic mice was worsened in Sp7/Runx2 double transgenic mice and the expression of Col1a1 and Bglap2 was reduced. The expression of Sp7 and Runx2 was not increased in Runx2 and Sp7 transgenic mice, respectively. The expression of endogenous Sp7 was increased in Sp7 transgenic mice and Sp7-transduced cells; the introduction of Sp7 activated and sh-Sp7 inhibited Sp7 promoter; and ChIP assay showed the binding of endogenous SP7 in the proximal region of Sp7 promoter. These findings suggest that SP7 and RUNX2 inhibit osteoblast differentiation at a late stage in a manner independent of RUNX2 and SP7, respectively, and SP7 positively regulates its own promoter.
authors.affiliation: Department of Cell Biology, Nagasaki University Graduate School of Biomedical Sciences, Nagasaki, Japan.
authors.forename: Carolina A
authors.initials: CA
authors.lastname: Yoshida
authors.forename: Hisato
authors.initials: H
authors.lastname: Komori
authors.forename: Zenjiro
authors.initials: Z
authors.lastname: Maruyama
authors.forename: Toshihiro
authors.initials: T
authors.lastname: Miyazaki
authors.forename: Keishi
authors.initials: K
authors.lastname: Kawasaki
authors.forename: Tatsuya
authors.initials: T
authors.lastname: Furuichi
authors.forename: Ryo
authors.initials: R
authors.lastname: Fukuyama
authors.forename: Masako
authors.initials: M
authors.lastname: Mori
authors.forename: Kei
authors.initials: K
authors.lastname: Yamana
authors.forename: Kouhei
authors.initials: K
authors.lastname: Nakamura
authors.forename: Wenguang
authors.initials: W
authors.lastname: Liu
authors.forename: Satoru
authors.initials: S
authors.lastname: Toyosawa
authors.forename: Takeshi
authors.initials: T
authors.lastname: Moriishi
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Kawaguchi
authors.forename: Kenji
authors.initials: K
authors.lastname: Takada
authors.forename: Toshihisa
authors.initials: T
authors.lastname: Komori
mesh_terms: D000818:Animals; D001842:Bone and Bones / Q000378:metabolism; D002454:Cell Differentiation; D047369:Chromatin Immunoprecipitation; D050659:Core Binding Factor Alpha 1 Subunit / Q000235:genetics / Q000502:physiology; D005786:Gene Expression Regulation; D017930:Genes, Reporter; D051379:Mice; D008822:Mice, Transgenic; D008954:Models, Biological; D010006:Osteoblasts / Q000166:cytology* / Q000378:metabolism; D010011:Osteocytes / Q000166:cytology; D011401:Promoter Regions, Genetic; D060888:Real-Time Polymerase Chain Reaction / Q000379:methods; D000076182:Sp7 Transcription Factor; D014157:Transcription Factors / Q000378:metabolism*; D015854:Up-Regulation
chemical_list: D050659:Core Binding Factor Alpha 1 Subunit; C493716:Runx2 protein, mouse; D000076182:Sp7 Transcription Factor; C479466:Sp7 protein, mouse; D014157:Transcription Factors