title: Differential roles of CCN family proteins during osteoblast differentiation: Involvement of Smad and MAPK signaling pathways.
abstract: CCN family proteins play diverse roles in many aspects of cellular processes such as proliferation, differentiation, adhesion, migration, angiogenesis and survival. In the bone tissue of vertebrate species, the expression of most CCN family members has been observed in osteoblasts. However, their spatial and temporal distributions, as well as their functions, are still only partially understood. In this study, we evaluated the localization of CCN family members in skeletal tissue in vivo and comparatively analyzed the gene expression patterns and functions of the members in murine osteoblasts in primary culture. Immunofluorescent analyses revealed that the CCN family members were differentially produced in osteoblasts and osteocytes. The presence of all Ccn transcripts was confirmed in those osteoblasts. Among the members, CCN1, CCN2, CCN4 and CCN5 were found in osteocytes. CCN4 and CCN5 were distributed in osteocytes located inside of bone matrix as well. Next, we investigated the expression pattern of Ccn family members during osteoblast differentiation. Along with differentiation, most of the members followed proper gene expression patterns; whereas, Ccn4 and Ccn5 showed quite similar patterns. Furthermore, we evaluated the effects of CCN family members on the osteoblastic activities by using recombinant CCN proteins and RNA interference method. Five members of this family displayed positive effects on osteoblast proliferation or differentiation. Of note, CCN3 drastically inhibited the osteoblast activities. Each Ccn specific siRNA could modulate osteoblast activities in a manner expected by the observed effect of respective recombinant CCN protein. In addition, we found that extracellular signal-regulated kinase1/2 and p38 mitogen-activated protein kinase pathways were critically involved in the CCN family member-mediated modification of osteoblast activities. Collectively, all Ccn family members were found to be differentially expressed along with differentiation and therefore could participate in progression of the osteoblast lineage.
authors.affiliation: Department of Biochemistry and Molecular Dentistry, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama, Japan.
authors.forename: Harumi
authors.initials: H
authors.lastname: Kawaki
authors.forename: Satoshi
authors.initials: S
authors.lastname: Kubota
authors.forename: Akiko
authors.initials: A
authors.lastname: Suzuki
authors.forename: Makoto
authors.initials: M
authors.lastname: Suzuki
authors.forename: Kumiko
authors.initials: K
authors.lastname: Kohsaka
authors.forename: Kenji
authors.initials: K
authors.lastname: Hoshi
authors.forename: Toshiya
authors.initials: T
authors.lastname: Fujii
authors.forename: Noureddine
authors.initials: N
authors.lastname: Lazar
authors.forename: Toshihiro
authors.initials: T
authors.lastname: Ohgawara
authors.forename: Takeyasu
authors.initials: T
authors.lastname: Maeda
authors.forename: Bernard
authors.initials: B
authors.lastname: Perbal
authors.forename: Teruko
authors.initials: T
authors.lastname: Takano-Yamamoto
authors.forename: Masaharu
authors.initials: M
authors.lastname: Takigawa
mesh_terms: D000818:Animals; D001483:Base Sequence; D015153:Blotting, Western; D002454:Cell Differentiation; D002478:Cells, Cultured; D017931:DNA Primers; D047908:Intracellular Signaling Peptides and Proteins / Q000502:physiology*; D020935:MAP Kinase Signaling System; D051379:Mice; D010006:Osteoblasts / Q000166:cytology* / Q000378:metabolism; D034741:RNA, Small Interfering; D060888:Real-Time Polymerase Chain Reaction; D051785:Smad Proteins / Q000502:physiology*
chemical_list: D017931:DNA Primers; D047908:Intracellular Signaling Peptides and Proteins; D034741:RNA, Small Interfering; D051785:Smad Proteins