Molecular cloning, sequencing, and tissue and developmental expression of mouse cartilage oligomeric matrix protein (COMP)

Mouse cartilage oligomeric matrix protein cDNA was cloned and sequenced by a reverse transcription-polymerase chain reaction. The open reading frame e ncoded a product of 755 amino acids that shares a high degree of identity t o and possesses all the characteristic molecular features of both rat and h uman cartilage oligomeric matrix protein. This suggests that cartilage olig omeric matrix protein is highly conserved during evolution. The clone was 8 3, 84, and 95% identical to human, bovine, and rat cartilage oligomeric mat rix protein cDNA, respectively. In tissues from the adult mouse, cartilage oligomeric matrix protein was expressed not only in cartilage and tendon bu t in trachea, bone, skeletal muscle, eye, heart, and placenta as well, and no expression was found in other tissues. Immunohistology revealed that car tilage oligomeric matrix was deposited as early as 10 days post coitus in p redifferentiated mouse embryo mesenchyme. It was detected in all cartilagin ous tissues and in the skeletal muscles of the embryo at day 13. As develop ment progressed, accumulation of cartilage oligomeric matrix protein was ma rked in the growth plate. At 19 days post coitus, it was prominently deposi ted in the hypertrophic zone of the growth plate, perichondrium, and perios teum and in the superficial layer of the articular cartilage surface but wa s absent in the more central areas of the epiphyseal cartilage. The restric ted tissue distribution and expression of cartilage oligomeric matrix prote in in developing as well as adult mouse tissues suggest the regulation of t his protein at the transcriptional level. The findings reported herein are the first detailed characterization of the distribution of cartilage oligom eric matrix protein during early skeletal development of the mouse.