Abstract
We describe a novel human gene, named SEL‐OB/SVEP1, expressed by skeletal tissues in vivo and by cultured osteogenic cells. The mRNA expression was analyzed on frozen tissues retrieved by laser‐capture microscope dissection (LCM) and was detected in osteogenic tissues (periosteum and bone) but not in cartilage or skeletal muscle. The SEL‐OB/SVEP1 cDNA of 11,139 bp was in silico translated into a 3574AA protein with expected molecular weight of 370 kDa. The protein is composed of multiple domains including complement control protein (CCP) modules with selectin superfamily signature; sushi and other domains, such as vWA, EGF, PTX, and HYR. Stromal osteogenic cells were analyzed for the protein expression using anti‐SEL‐OB/SVEP1 for immuno‐precipitation and Western blot application confirm the presence of high molecular weight protein. Immuno‐histochemistry and fluorescence‐activated cell sorting (FACS) were applied to detect SEL‐OB/SVEP1 on the surface of stromal cells. ELISA quantified the dependence of protein expression on cell density. Bioinformatic analysis of SEL‐OB/SVEP1 revealed domains compositions recognized in cell surface molecules and suggested its role in cell adhesion. Analysis of mesechymal osteogenic cells' adhesion in presence of anti‐SEL‐OB/SVEP1 antibody demonstrated its interference with initial adhesion stages. In summary, present study describes novel SEL‐OB/SVEP1 protein with a unique composition of functional domains, restricted pattern of expression in skeletal cells and demonstrated involvement in attachment of mesenchymal cells. The unusual composition of functional domains puts SEL‐OB/SVEP1 in the discrete new group of membrane proteins involved in cell adhesion processes. All together makes SEL‐OB/SVEP1 an attractive marker for studying the role of stromal osteogenic cells and their interactions within the bone marrow microenvironment creating a network that regulates the skeletal homeostasis. J. Cell. Physiol. 206: 420–427, 2006. © 2005 Wiley‐Liss, Inc.