Assessment of gene regulation by bone morphogenetic protein 2 in human marrow stromal cells using gene array technology

Marrow stromal cells can differentiate into osteoblasts, adipocytes, myobla sts, and chondrocytes. Bone morphogenetic protein 2 (BMP-2) is a potent sti mulator of osteoblastic differentiation, and identification of the genes re gulated by BMP-2 in these cells should provide insight into the mechanism(s ) of osteoblastic differentiation. Thus, we used a conditionally immortaliz ed human marrow stromal cell line (hMS) and a gene expression microarray co ntaining probes for a total of 6800 genes to compare gene expression in con trol and BMP-2-treated cultures. A total of 51 genes showed a consistent ch ange in messenger RNA (mRNA) frequency between two repeat experiments. Seve nteen of these genes showed a change in expression of at least 3-fold in BM P-2-treated cultures over control cultures. These included nuclear binding factors (10 genes), signal transduction pathway genes (2 genes), molecular transport (1 gene), cell surface proteins (2 genes) and growth factors (2 g enes). Of particular interest were four of the nuclear binding factor genes ID-1, ID-2, ID-3, and ID-4. These encode dominant negative helix-loop-heli x (dnHLH) proteins that lack the nuclear binding domain of the basic HLH pr oteins and thus have no transcriptional activity. They have been implicated in blocking both myogenesis and adipogenesis. Other transcription factors up-regulated at least 3-fold by BMP-2 included Dlx-2, HES-1, STAT1, and Jun B. The changes in these nuclear binding factor mRNA levels were confirmed b y real-time reverse-transcriptase-polymerase chain reaction (RT-PCR). A fur ther three transcription factors, core binding factor beta (CBF beta), AREB 6, and SOX4, showed changes in expression of between 2- and 3-fold with BMP -2 treatment. In summary, we have used a gene chip microarray to identify a number of BMP-2 responsive genes in hMS cells. Thus, these studies provide potential candidate genes that may induce osteoblastic differentiation or, in the case of the ID proteins, block differentiation along alternate path ways.