title: Obif, a Transmembrane Protein, Is Required for Bone Mineralization and Spermatogenesis in Mice.
abstract: BACKGROUND
  Various kinds of transmembrane and secreted proteins play pivotal roles in development through cell-cell communication. We previously reported that Obif (Osteoblast induction factor, Tmem119), encoding a single transmembrane protein, is expressed in differentiating osteoblasts, and that Obif-/- mice exhibit significantly reduced bone volume in the femur. In the current study, we characterized the Obif protein and further investigated the biological phenotypes of a variety of tissues in Obif-/- mice.
  
  
  RESULTS
  First, we found that O-glycosylation of the Obif protein occurs at serine residue 36 in the Obif extracellular domain. Next, we observed that Obif-/- mice exhibit bone dysplasia in association with significantly increased osteoid volume per osteoid surface (OV/OS) and osteoid maturation time (Omt), and significantly decreased mineral apposition rate (MAR) and bone formation rate per bone surface (BFR/BS). In addition, we observed that Obif-/- mice show a significant decrease in testis weight as well as in sperm number. By histological analysis, we found that Obif is expressed in spermatocytes and spermatids in the developing testis and that spermatogenesis is halted at the round spermatid stage in the Obif-/- testis that lacks sperm. However, the number of litters fathered by male mice was slightly reduced in Obif-/- mice compared with wild-type mice, although this was not statistically significant.
  
  
  CONCLUSIONS
  Our results, taken together with previous observations, indicate that Obif is a type Ia transmembrane protein whose N-terminal region is O-glycosylated. In addition, we found that Obif is required for normal bone mineralization and late testicular differentiation in vivo. These findings suggest that Obif plays essential roles in the development of multiple tissues.
authors.affiliation: Laboratory for Molecular and Developmental Biology, Institute for Protein Research, Osaka University, 3-2 Yamadaoka, Suita, Osaka, Japan; Department of Developmental Biology, Osaka Bioscience Institute, 6-2-4 Furuedai, Suita, Osaka, Japan.
authors.forename: Koji
authors.initials: K
authors.lastname: Mizuhashi
authors.affiliation: Laboratory for Molecular and Developmental Biology, Institute for Protein Research, Osaka University, 3-2 Yamadaoka, Suita, Osaka, Japan; Department of Developmental Biology, Osaka Bioscience Institute, 6-2-4 Furuedai, Suita, Osaka, Japan; Japan Science and Technology Agency, Core Research for Evolutional Science and Technology, 3-2 Yamadaoka, Suita, Osaka, Japan.
authors.forename: Taro
authors.initials: T
authors.lastname: Chaya
authors.affiliation: Department of Developmental Biology, Osaka Bioscience Institute, 6-2-4 Furuedai, Suita, Osaka, Japan; Department of Orthopedic Surgery, Osaka University Graduate School of Medicine, 2-2 Yamadaoka, Suita, Osaka, Japan.
authors.forename: Takashi
authors.initials: T
authors.lastname: Kanamoto
authors.affiliation: Laboratory for Molecular and Developmental Biology, Institute for Protein Research, Osaka University, 3-2 Yamadaoka, Suita, Osaka, Japan; Department of Developmental Biology, Osaka Bioscience Institute, 6-2-4 Furuedai, Suita, Osaka, Japan; Japan Science and Technology Agency, Core Research for Evolutional Science and Technology, 3-2 Yamadaoka, Suita, Osaka, Japan.
authors.forename: Yoshihiro
authors.initials: Y
authors.lastname: Omori
authors.affiliation: Laboratory for Molecular and Developmental Biology, Institute for Protein Research, Osaka University, 3-2 Yamadaoka, Suita, Osaka, Japan; Department of Developmental Biology, Osaka Bioscience Institute, 6-2-4 Furuedai, Suita, Osaka, Japan; Japan Science and Technology Agency, Core Research for Evolutional Science and Technology, 3-2 Yamadaoka, Suita, Osaka, Japan.
authors.forename: Takahisa
authors.initials: T
authors.lastname: Furukawa
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002113:Calcification, Physiologic / Q000235:genetics*; D002478:Cells, Cultured; D005260:Female; D057809:HEK293 Cells; D006801:Humans; D008297:Male; D008565:Membrane Proteins / Q000235:genetics / Q000502:physiology*; D051379:Mice; D018345:Mice, Knockout; D008969:Molecular Sequence Data; D017386:Sequence Homology, Amino Acid; D013090:Spermatocytes / Q000502:physiology; D013091:Spermatogenesis / Q000235:genetics*; D013737:Testis / Q000254:growth & development / Q000378:metabolism
chemical_list: D008565:Membrane Proteins; C547179:Obif protein, mouse