title: Bril: a novel bone-specific modulator of mineralization.
abstract: In the course of attempting to define the bone "secretome" using a signal-trap screening approach, we identified a gene encoding a small membrane protein novel to osteoblasts. Although previously identified in silico as ifitm5, no localization or functional studies had been undertaken on this gene. We characterized the expression patterns and localization of this gene in vitro and in vivo and assessed its role in matrix mineralization in vitro. The bone specificity and shown role in mineralization led us to rename the gene bone restricted ifitm-like protein (Bril). Bril encodes a 14.8-kDa 134 amino acid protein with two transmembrane domains. Northern blot analysis showed bone-specific expression with no expression in other embryonic or adult tissues. In situ hybridization and immunohistochemistry in mouse embryos showed expression localized on the developing bone. Screening of cell lines showed Bril expression to be highest in osteoblasts, associated with the onset of matrix maturation/mineralization, suggesting a role in bone formation. Functional evidence of a role in mineralization was shown by adenovirus-mediated Bril overexpression and lentivirus-mediated Bril shRNA knockdown in vitro. Elevated Bril resulted in dose-dependent increases in mineralization in UMR106 and rat primary osteoblasts. Conversely, knockdown of Bril in MC3T3 osteoblasts resulted in reduced mineralization. Thus, we identified Bril as a novel osteoblast protein and showed a role in mineralization, possibly identifying a new regulatory pathway in bone formation.
authors.affiliation: Shriners Hospital for Children, Montreal, Quebec, Canada.
authors.forename: Pierre
authors.initials: P
authors.lastname: Moffatt
authors.forename: Marie-Helene
authors.initials: MH
authors.lastname: Gaumond
authors.forename: Patrick
authors.initials: P
authors.lastname: Salois
authors.forename: Karine
authors.initials: K
authors.lastname: Sellin
authors.forename: Marie-Claude
authors.initials: MC
authors.lastname: Bessette
authors.forename: Eric
authors.initials: E
authors.lastname: Godin
authors.forename: Paulo Tambasco
authors.initials: PT
authors.lastname: de Oliveira
authors.forename: Gerald J
authors.initials: GJ
authors.lastname: Atkins
authors.forename: Antonio
authors.initials: A
authors.lastname: Nanci
authors.forename: Gethin
authors.initials: G
authors.lastname: Thomas
mesh_terms: D000256:Adenoviridae; D000595:Amino Acid Sequence; D000818:Animals; D015415:Biomarkers / Q000378:metabolism; D015153:Blotting, Western; D001842:Bone and Bones / Q000378:metabolism*; D002113:Calcification, Physiologic; D002460:Cell Line; D003001:Cloning, Molecular; D004622:Embryo, Mammalian / Q000166:cytology / Q000378:metabolism; D005455:Fluorescent Antibody Technique; D020869:Gene Expression Profiling; D006801:Humans; D017403:In Situ Hybridization; D016086:Lentivirus; D008565:Membrane Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D008969:Molecular Sequence Data; D009928:Organ Specificity; D010006:Osteoblasts / Q000166:cytology / Q000378:metabolism; D011506:Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D051381:Rats; D016415:Sequence Alignment
chemical_list: D015415:Biomarkers; C575746:IFITM5 protein, human; C532488:IFITM5 protein, mouse; C532489:Ifitm5 protein, rat; D008565:Membrane Proteins; D011506:Proteins