Bril: a novel bone-specific modulator of mineralization.
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.
Moffatt
Pierre
P
Shriners Hospital for Children, Montreal, Quebec, Canada.
Gaumond
Marie-Helene
MH
Salois
Patrick
P
Sellin
Karine
K
Bessette
Marie-Claude
MC
Godin
Eric
E
de Oliveira
Paulo Tambasco
PT
Atkins
Gerald J
GJ
Nanci
Antonio
A
Thomas
Gethin
G
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
D015415:Biomarkers; C575746:IFITM5 protein, human; C532488:IFITM5 protein, mouse; C532489:Ifitm5 protein, rat; D008565:Membrane Proteins; D011506:Proteins