Osteoblast-specific factor 2: cloning of a putative bone adhesion protein with homology with the insect protein fasciclin I.
A cDNA library prepared from the mouse osteoblastic cell line MC3T3-E1 was screened for the presence of specifically expressed genes by employing a combined subtraction hybridization/differential screening approach. A cDNA was identified and sequenced which encodes a protein designated osteoblast-specific factor 2 (OSF-2) comprising 811 amino acids. OSF-2 has a typical signal sequence, followed by a cysteine-rich domain, a fourfold repeated domain and a C-terminal domain. The protein lacks a typical transmembrane region. The fourfold repeated domain of OSF-2 shows homology with the insect protein fasciclin I. RNA analyses revealed that OSF-2 is expressed in bone and to a lesser extent in lung, but not in other tissues. Mouse OSF-2 cDNA was subsequently used as a probe to clone the human counterpart. Mouse and human OSF-2 show a high amino acid sequence conservation except for the signal sequence and two regions in the C-terminal domain in which 'in-frame' insertions or deletions are observed, implying alternative splicing events. On the basis of the amino acid sequence homology with fasciclin I, we suggest that OSF-2 functions as a homophilic adhesion molecule in bone formation.
Takeshita
S
S
Hoechst Japan Limited, Pharma Research Laboratories, Saitama.
Kikuno
R
R
Tezuka
K
K
Amann
E
E
D016475:3T3 Cells; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D001842:Bone and Bones / Q000378:metabolism*; D015815:Cell Adhesion Molecules / Q000235:genetics*; D015816:Cell Adhesion Molecules, Neuronal / Q000235:genetics*; D002460:Cell Line; D003001:Cloning, Molecular; D004247:DNA; D005786:Gene Expression Regulation; D006801:Humans; D007313:Insecta; D051379:Mice; D008969:Molecular Sequence Data; D012333:RNA, Messenger / Q000378:metabolism; D017386:Sequence Homology, Amino Acid
D015815:Cell Adhesion Molecules; D015816:Cell Adhesion Molecules, Neuronal; C512835:POSTN protein, human; C082838:Postn protein, mouse; D012333:RNA, Messenger; C051641:fasciclin I; D004247:DNA