cDNA cloning and gene expression of chicken osteopontin. Expression of osteopontin mRNA in chondrocytes is enhanced by trypsin treatment of cells

Abstract

A cDNA clone, pCP15, specific for the chicken 66-kDa major bone phosphoprotein (osteopontin), was isolated from a subtracted library enriched in DNAs coding for mRNAs expressed in chicken differentiating chondrocytes. Northern blot analysis of RNAs extracted from several chick embryo tissues and organs, confirm and extend the observation that osteopontin mRNA expression is not restricted to tissues involved in phosphate metabolism. Osteopontin mRNA was detected in sternal resting chondrocytes at higher levels than in hypertrophic chondrocytes; therefore osteopontin gene transcription occurs in chondrocytes at many stages of differentiation. The steady state level of osteopontin mRNA was enhanced by trypsin treatment of cultured cells. An increased level of osteopontin mRNA in quail chondrocytes constitutively expressing v-myc oncogene is also shown.