An osteogenesis-related transcription factor, core-binding factor A1, is constitutively expressed in the chondrocytic cell line TC6, and its expression is upregulated by bone morphogenetic protein-2

Core-binding factor Al (Cbfa1), also called Pebp2 alpha A/AML3, is a transc ription factor that belongs to the runt-domain gene family. Cbfa1-deficient mice are completely incapable of both endochondral and intramembranous bon e formation, indicating that Cbfa1 is indispensable for osteogenesis, Matur ation of chondrocytes in these mice is also disorganized, suggesting that C bfa1 may also play a role in chondrogenesis. The aim of this study was to e xamine the expression and regulation of Pebp2 alpha A/AML3/Cbfa1 expression in the chondrocyte-like cell line, TC6, Northern blot analysis indicated t hat Cbfa1 mRNA was constitutively expressed as a 6.3 kb message in TC6 cell s and the level of Cbfa1 expression was enhanced by treatment with bone mor phogenetic protein-2 (BMP2) in a time- and dose-dependent manner. This effe ct was blocked by an RNA polymerase inhibitor, 5,6-dichloro-1-beta-D-ribofu ranosylbenzimidazole, but not by a protein synthesis inhibitor, cycloheximi de. Western blot analysis of the cell lysates using polyclonal antibody rai sed against Cbfa1 indicated that BMP2 treatment increased the Cbfa1 protein level in TC6 cells. In TC6 cells, BMP2 treatment enhanced expression of al kaline phosphatase and type I collagen mRNAs but suppressed that of type II collagen mRNA. In addition to TC6 cells, Cbfa1 mRNA was also expressed in primary cultures of chondrocytes and BMP2 treatment enhanced Cbfa1 mRNA exp ression in these cells similarly to its effect on TC6 cells. These data ind icate that the Pebp2 alpha A/AML3/Cbfa1 gene is expressed in a chondrocyte- like cell line, TC6, and its expression is enhanced by treatment with BMP.