Proline-rich transcript of the brain (prtb) is a serum-responsive gene in osteoblasts and upregulated during adhesion.
To characterize the temporal expression of genes that play a functional role during the process of osteoblast adhesion, we used differential display (DD-PCR) on mRNA isolated from attached vs. suspended osteoblasts. A 200-bp fragment displaying upregulated expression after 30 and 60 min adhesion was isolated, sequenced, and showed 97% homology to prtb, previously showed to be expressed in mouse brain. Northern analysis confirmed a two-fold increase in prtb message during adhesion to tissue culture polystyrene, both in the presence or absence of surface-adsorbed serum proteins. Serum stimulation alone was also able to induce prtb expression, although to a lesser extent, in suspension cells. Strong prtb expression was also detected in both brain and bone of adult rats. Furthermore, prtb expression analysis during MC3T3-E1 cell differentiation revealed high expression levels independent of proliferation (day 0-7), matrix maturation (day 7-14), and mineralization (day 14-31). Time course analysis of prtb expression during adhesion of sensitized osteoblasts to serum-protein coated surfaces showed robust mRNA expression at 5 min post-plating and a peak at 10 min. The two known serum-inducible immediate early genes c-fos and c-jun showed similar expression kinetics, with c-jun mRNA levels peaking at 15 min and c-fos at 20 min. Based on these data, we hypothesize that prtb may function as an immediate early, serum-responsive, and adhesion-inducible gene with possible involvement in processes such as cell cycle control, adhesion, and proliferation.
Sommerfeldt
Dirk W
DW
Department of Orthopaedics, State University of New York at Stony Brook, Stony Brook, New York 11794-2580, USA.
Zhi
Jizu
J
Rubin
Clinton T
CT
Hadjiargyrou
Michael
M
D016475:3T3 Cells; D000818:Animals; D001483:Base Sequence; D001769:Blood; D015152:Blotting, Northern; D001921:Brain / Q000378:metabolism*; D002448:Cell Adhesion / Q000235:genetics*; D017931:DNA Primers; D016762:Genes, fos; D016758:Genes, jun; D051379:Mice; D010006:Osteoblasts / Q000166:cytology*; D010455:Peptides / Q000235:genetics* / Q000378:metabolism; D011392:Proline / Q000378:metabolism*; D055232:Proline-Rich Protein Domains; D012333:RNA, Messenger / Q000235:genetics*; D015854:Up-Regulation
D017931:DNA Primers; D010455:Peptides; D012333:RNA, Messenger; D011392:Proline