title: Fibulin-1 is required for bone formation and Bmp-2-mediated induction of Osterix.
abstract: The extracellular matrix protein Fibulin-1 (Fbln1) has been shown to be involved in numerous processes including cardiovascular and lung development. Here we have examined the role of Fbln1 in bone formation. Alizarin red staining of skulls from Fbln1-deficient mice showed reduced mineralization of both membranous and endochondral bones. MicroCT (μCT) analysis of the calvarial bones (i.e., frontal, parietal and interparietal bones collectively) indicated that bone volume in Fbln1 nulls at neonatal stage P0 were reduced by 22% (p=0.015). Similarly, Fbln1 null frontal bones showed a 16% (p=0.035) decrease in bone volume, with a reduction in the interfrontal bone, and a discontinuity in the leading edge of the frontal bone. To determine whether Fbln1 played a role in osteoblast differentiation during bone formation, qPCR was used to measure the effects of Fbln1 deficiency on the expression of Osterix (Osx), a transcription factor essential for osteoblast differentiation. This analysis demonstrated that Osx mRNA was significantly reduced in Fbln1-deficient calvarial bones at developmental stages E16.5 (p=0.049) and E17.5 (p=0.022). Furthermore, the ability of Bmp-2 to induce Osx expression was significantly diminished in Fbln1-deficient mouse embryo fibroblasts. Together, these findings indicate that Fbln1 is a new positive modulator of the formation of membranous bone and endochondral bone in the skull, acting as a positive regulator of Bmp signaling.
authors.affiliation: Department of Regenerative Medicine and Cell Biology, Medical University of South Carolina, Charleston, SC 29425, USA; Department of Oral Health Sciences, Medical University of South Carolina, Charleston, SC 29425, USA. Electronic address: cooleyma@musc.edu.
authors.forename: Marion A
authors.initials: MA
authors.lastname: Cooley
authors.affiliation: Department of Regenerative Medicine and Cell Biology, Medical University of South Carolina, Charleston, SC 29425, USA.
authors.forename: Keerthi
authors.initials: K
authors.lastname: Harikrishnan
authors.affiliation: Department of Regenerative Medicine and Cell Biology, Medical University of South Carolina, Charleston, SC 29425, USA.
authors.forename: James A
authors.initials: JA
authors.lastname: Oppel
authors.affiliation: Department of Regenerative Medicine and Cell Biology, Medical University of South Carolina, Charleston, SC 29425, USA.
authors.forename: Sloan F
authors.initials: SF
authors.lastname: Miler
authors.affiliation: Department of Regenerative Medicine and Cell Biology, Medical University of South Carolina, Charleston, SC 29425, USA.
authors.forename: Jeremy L
authors.initials: JL
authors.lastname: Barth
authors.affiliation: Department of Oral Health Sciences, Medical University of South Carolina, Charleston, SC 29425, USA.
authors.forename: Courtney J
authors.initials: CJ
authors.lastname: Haycraft
authors.affiliation: Charles P. Darby Children's Research Institute, Medical University of South Carolina, Charleston, SC 29425, USA.
authors.forename: Sakamuri V
authors.initials: SV
authors.lastname: Reddy
authors.affiliation: Department of Regenerative Medicine and Cell Biology, Medical University of South Carolina, Charleston, SC 29425, USA.
authors.forename: W
authors.initials: W
authors.lastname: Scott Argraves
mesh_terms: D000818:Animals; D055396:Bone Morphogenetic Protein 2 / Q000378:metabolism*; D002135:Calcium-Binding Proteins / Q000378:metabolism*; D002454:Cell Differentiation; D007150:Immunohistochemistry; D020287:In Situ Nick-End Labeling; D051379:Mice; D018345:Mice, Knockout; D010006:Osteoblasts / Q000166:cytology / Q000378:metabolism*; D010012:Osteogenesis / Q000502:physiology*; D060888:Real-Time Polymerase Chain Reaction; D000076182:Sp7 Transcription Factor; D014157:Transcription Factors / Q000378:metabolism*; D059467:Transcriptome
chemical_list: C525719:Bmp2 protein, mouse; D055396:Bone Morphogenetic Protein 2; D002135:Calcium-Binding Proteins; D000076182:Sp7 Transcription Factor; C479466:Sp7 protein, mouse; D014157:Transcription Factors; C060820:fibulin
keywords: Bmp-2; Extracellular matrix protein; Fibulin-1; Osteoblast differentiation; Osterix