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

Abstract

Core-binding factor A1 (Cbfa1), also called Pebp2 A/ AML3, is a transcription factor that belongs to the runtdomain gene family. Cbfa1-deficient mice are completely incapable of both endochondral and intramembranous bone formation, indicating that Cbfa1 is indispensable for osteogenesis. Maturation of chondrocytes in these mice is also disorganized, suggesting that Cbfa1 may also play a role in chondrogenesis. The aim of this study was to examine the expression and regulation of Pebp2 A/ AML3/Cbfa1 expression in the chondrocyte-like cell line, TC6. Northern blot analysis indicated that Cbfa1 mRNA was constitutively expressed as a 6·3 kb message in TC6 cells and the level of Cbfa1 expression was enhanced by treatment with bone morphogenetic protein-2 (BMP2) in a time-and dose-dependent manner. This effect was blocked by an RNA polymerase inhibitor, 5,6-dichloro-1---ribofuranosylbenzimidazole, but not by a protein synthesis inhibitor, cycloheximide. Western blot analysis of the cell lysates using polyclonal antibody raised against Cbfa1 indicated that BMP2 treatment increased the Cbfa1 protein level in TC6 cells. In TC6 cells, BMP2 treatment enhanced expression of alkaline 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 expression in these cells similarly to its effect on TC6 cells. These data indicate that the Pebp2 A/AML3/Cbfa1 gene is expressed in a chondrocyte-like cell line, TC6, and its expression is enhanced by treatment with BMP.

Differential regulation of Cbfa1/Runx2 and osteocalcin gene expression by vitamin‐D3, dexamethasone, and local growth factors in primary human osteoblasts

“…It is unknown, however, whether BMPs may promote also the human osteoblastic phenotype by increasing the growth or differentiation of cells at different stages of maturation. An increase of Cbfa1 expression by BMP-2 has been consistently demonstrated in immortalized human neonatal calvarial cells [Hay et al, 2000], in an immortalized human marrow stromal cell line (hMS (2-6)) [Gori et al, 1999], in mouse pluripotent mesenchymal precursor cells (C2C12) [Lee et al, 1999], and in a chondrocyte like cell line (TC6) [Takazawa et al, 2000]. In a conditionally immortalized human marrow stromal cell line (hMS (2-6)), BMP-2 enhanced osteoblast differentiation as assessed by a 1.8-fold increase in expression of Cbfa1.…”

A Review of the Clinical Side Effects of Bone Morphogenetic Protein-2

“…27,28 Among other factors, BMP-2 induces the master osteogenic transcription factor runt-related transcription factor 2 (Runx2) in osteoblasts to induce osteogenic programming [29][30][31] (see Chen et al 32 for a more complete review of BMP-2 signaling). 65,69,[145][146][147][148] Seroma formation 65,66,[149][150][151][152][153][154] Radiculopathy Nerve root compression/postoperative radiculitis However, the cellular effects of BMP-2 a far more pleiotropic than this would suggest.…”

Indian hedgehog: Its roles and regulation in endochondral bone development

“…The same authors identified seven putative Runx2 binding elements within the 5 0 flanking region of Ihh and showed that three of these binding elements are important for Ihh transcriptional activation by Runx2. At least one study in chondrocytes has shown that BMP2 upregulated Runx2 mRNA [Takazawa et al, 2000] and many studies in both chondrocytes and osteoblasts have demonstrated cooperative regulation of gene expression by Runx2 and Smads [Leboy et al, 2001]. Therefore, BMP regulation of Ihh expression could be mediated by a combination of Smad and Runx2 transcription factors.…”