The human analog of murine cystein rich protein 16 is a 1α,25-dihydroxyvitamin D3 responsive immediate early gene in human fetal osteoblasts:: Regulation by cytokines, growth factors, and serum

1 alpha,25-dihydroxyvitamin D-3 (1,25-(OH)(2)D-3) is a potent mediator of differentiation and maintenance of specific functions of osteoblasts. To detect novel targets for 1,25-(OH)(2)D-3 action, we applied differential dis:play PCR to human fetal osteoblast-like cells and identified the human analog of murine cystein rich protein 61 (hCYR61) as a 1,25-(OH)(2)D-3-responsive immediate early gene in differentiated fetal osteoblast-like cells. The murine gene CYR61 is important for cell-cell and cell-matrix interactions, and it belongs to an emerging gene family of cysteine-rich proteins. hCYRG1 messenger RNA (mRNA) steady-state levels were stimulated 11-fold by 10 nM 1,25-(OH)(2)D-3 by 1 h and declined to control levels by 4 h. This transient stimulation of hCYRG1 mRNA was not inhibited by cycloheximide but was prevented by actinomycin D, indicating that the 1,25-(OH)(2)D-3 effect involves transcriptional events and does not require de novo protein synthesis. hCYR61 mRNA stability was not influenced by 1,25(OH)(2)D-3, whereas cycloheximide treatment stabilized hCYR61 mRNA. FCS, as well as growth factors and cytokines such as basic fibroblast growth factor, epidermal growth factor, tumor necrosis factor alpha, and interleukin-l, strongly elevated hCYR61 mRNA steady-state levels within 1 h. hCYR61 mRNA was expressed also in primary human osteoblasts and osteosarcoma cell lines. Using a commercial tissue blot, hCYR61 mRNA was only observed in skeletal muscle. The fast and transient response of hCYR 61 to 1,25-(OH)(2)D-3, serum, growth factors, and cytokines suggests an important role of hCYR61 for osteoblast function and differentiation.