RANK-L induces the expression of NFATc1, but not of NFκB subunits during osteoclast formation

Abstract

We report the program of gene expression during osteoclast formation from RAW264.7 cell precursors in response to RANK-ligand (RANK-L) using a combination of quantitative real time PCR and Affymetrix gene chip assays. We found that genes obligatory to osteoclast formation and function, namely tartrate-resistant acid phosphatase, cathepsin K, β3 integrin, and calcitonin receptors, were up-regulated by RANK-L markedly by up to ∼2000-fold. In contrast, we found a cluster of genes that were significantly down-regulated: these included interleukin-18, insulin-like growth factor-1, interleukin-6 receptor, and cathepsins B, C, and L. These results from real time PCR were broadly concordant with those obtained from Affymetrix. We also explored the expression of the transcription factors of the NFAT and NFκB family at days 3 and 5 of culture. Whereas NFATc1 expression was increased significantly at days 3 and 5 following RANK-L exposure, there were no significant increases in the expression of NFκB subunits, namely p65, p50, c-Rel, IκBα, and IκBβ. There were also no significant differences in transcription modulator expression between days 3 and 5, except for c- Rel and NFATc4, which were both decreased significantly at day 5. The studies suggest RANK-L regulates the expression only of NFATc1, while it signals through both NFATc1 and NFκB.