Expression of Recombinant Human BMP-6 in CHO Cell by Fusion of a BMP-6 Mature Peptide to the Signal Peptide and Propeptide of Another Homologue Protein

Bone morphogenetic protein-6 (BMP-6) is a member of transforming growth factors β superfamily with more effective osteogenic activity. In this study, two recombinant plasmids were constructed to produce the recombinant proteins in mammalian expression system. One contained a gene encoding the signal peptide, propeptide, and mature peptide of human BMP-6, namely pcDNA-BMP-6, the other one was the recombinant gene encoding the signal peptide, propeptide of human BMP-2, and the mature peptide of BMP-6, namely pcDNA-BMP2/6. Transient expression in Cos7 cells showed that the pcDNA-BMP2/6 could produce more recombinant protein rhBMP-6 than pcDNA-BMP-6. For stable expression, the Chinese hamster ovary (CHO-dhfr-) cells were co-transfected with pcDNA-BMP2/6 and pSV2-dhfr, and thereafter selected under the G418 as well as treated with methotrexate for targeting gene amplification. The purified rhBMP-6 with heparin affinity chromatography was shown to be able to possess bone induction activity by measuring the activation of alkaline phosphatase in C2C12 cells.