Isolation and characterization of a novel plasma membrane protein, osteoblast induction factor (obif), associated with osteoblast differentiation

Abstract

BackgroundWhile several cell types are known to contribute to bone formation, the major player is a common bone matrix-secreting cell type, the osteoblast. Chondrocytes, which plays critical roles at several stages of endochondral ossification, and osteoblasts are derived from common precursors, and both intrinsic cues and signals from extrinsic cues play critical roles in the lineage decision of these cell types. Several studies have shown that cell fate commitment within the osteoblast lineage requires sequential, stage-specific signaling to promote osteoblastic differentiation programs. In osteoblastic differentiation, the functional mechanisms of transcriptional regulators have been well elucidated, however the exact roles of extrinsic molecules in osteoblastic differentiation are less clear.ResultsWe identify a novel gene, obif (osteoblast induction factor), encoding a transmembrane protein that is predominantly expressed in osteoblasts. During mouse development, obif is initially observed in the limb bud in a complementary pattern to Sox9 expression. Later in development, obif is highly expressed in osteoblasts at the stage of endochondral ossification. In cell line models, obif is up-regulated during osteoblastic differentiation. Exogenous obif expression stimulates osteoblastic differentiation and obif knockdown inhibits osteoblastic differentiation in preosteblastic MC3T3-E1 cells. In addition, the extracellular domain of obif protein exhibits functions similar to the full-length obif protein in induction of MC3T3-E1 differentiation.ConclusionsOur results suggest that obif plays a role in osteoblastic differentiation by acting as a ligand.

Parathyroid Hormone-responsive Smad3-related Factor, Tmem119, Promotes Osteoblast Differentiation and Interacts with the Bone Morphogenetic Protein-Runx2 Pathway

“…Consistent with our data, Tmem119 stimulated differentiation in osteoblasts (42). Moreover, overexpression and knockdown enhanced and suppressed mineralization in MC3T3-E1 cells, respectively (42).…”

OBIF, an osteoblast induction factor, plays an essential role in bone formation in association with osteoblastogenesis

“…To determine a possible role of Obif in bone formation, we generated Obif ‐deficient mouse by targeted gene disruption. Mouse Obif mRNA contains a single long open reading frame (ORF) encoding 280 amino acids, including a putative signal sequence (amino acid residues 1–18) and a single transmembrane domain (amino acid residues 92–112), suggesting that OBIF is a type IA transmembrane protein (Kanamoto et al. 2009).…”

“…2007). In addition, Obif promoters contain a number of putative RUNX2‐binding sites in multiple species (Kanamoto et al. 2009).…”

“…In our previous report, we identified a gene encoding a single transmembrane protein, Obif , which is predominantly expressed in osteoblasts during mouse development. We performed functional analyses on this gene in vitro (Kanamoto et al. 2009).…”

Loss of transcription factor early growth response gene 1 results in impaired endochondral bone repair

“…RNA was treated with DNAse I (Qiagen) and cDNA was synthesized utilizing the High Capacity cDNA Reverse Transcription kit (Applied Biosystems, Carlsbad, CA) as instructed by the manufacturer. We used the following primers: type 1 procollagen (COL1A1), F: 5′-ACGTCCTGGTGAAGTTGGTC-3′ and R: 5′-CAGGGAAGCCTCTTTCTCCT-3′ [29]; tissue non-specific alkaline phosphatase (TNAP), F: 5′-AAGGCTTCTTCTTGCTGGTG-3′ and R: 5′-GCCTTACCCTCATGATGTCC-3′ [30]; osteocalcin (OC), F: 5′-CGGGAGCAGTGTGAGCTTA-3′ and R: 5′-AGGCGGTCTTCAAGCCATACT-3′ [31]; tartrate-resistant acid phosphatase (TRAP), F: 5′-CCAATGCCAAAGAGATCGCC-3′ and R: 5′-TCTGTGCAGAGACGTTGCCAAG-3′ [32]; cathepsin K (CTSK), F: 5′-AAAGCAGTACAACGGCAAGG-3′ and R: 5′-GAGCTCACATCTTGGGGAAG-3′ [33]; and glyceraldehyde 3-phosphate dehydrogenase (GAPDH), F: 5′-TGCGACTTCAACAGCAACTC-3′ and R: 5′-ATGTAGGCCATGAGGTCCAC-3′ [34]. Amplifications were carried out in a total volume of 50 μl for 25–35 cycles with denaturation at 94°C for 45 seconds, annealing at 56°C for 45 seconds, and amplification at 72°C for 1 minute.…”