Dlx5 induces expression of COL1A1 promoter contained in a retrovirus vector

Aim. To determine whether retrovirally expressed Dlx5, a homeobox-containin g transcription factor, can induce a 2.3 kb rat COL1A1 promoter-reporter co nstruct, which is transduced into osteoblastic cells by the use of a retrov irus vector. Methods. A self-inactivating retrovirus vector containing the rat COL1A1 dr iving green fluorescent protein (GFP) was transduced into chick calvarial p eriosteal cells. These cells were then infected with a replication-competen t retroviral vector expressing Dlx5, or a control vector. The cells were cu ltured in the presence of ascorbic acid and beta -glycerol-phosphate, which promotes osteoblastic differentiation. Expression of the COL1A1 promoter w as assessed by detecting GFP with fluorescence microscopy. Results. GFP was detected only in cells infected with the Dlx5 expressing r etrovirus. The GFP positive cells were observed in regions of the culture t hat had undergone osteoblastic differentiation, as detected by cell morphol ogy and the presence of a mineralized matrix. Conclusion. The 2.3 kb rat COL1A1 promoter fragment contains elements respo nsive to Dlx5, and the self-inactivating retroviral vector allows these ele ments to be used appropriately.