TGFβ induces <i>SOST</i> expression through Smad3.

<p>Treating UMR-106 cells with TGFβ1 (5 ng/ml) for 2, 8, or 24 h results in an increase in <i>SOST</i> mRNA, while inhibiting TGFβ signaling with SB431542 results in a decrease in <i>SOST</i> expression (A). Smad3 overexpression with pRK5-Smad3 induces the <i>SOST</i> promoter-reporter construct, 3XECR-hSOSTpLuc, in a TGFβ dose-dependent manner within 24 h of TGFβ treatment (B). Blocking translation with cycloheximide (CHX) or transcription with actinomycin-D (ActD) for 2 h prevents TGFβ (5 ng/ml) induction of <i>SOST</i> expression (C). siRNA mediated knockdown of <i>Runx2</i> did not prevent TGFβ (5 ng/ml) induction of <i>SOST</i> expression (D). (For panel C, * represents p<0.05 computed by comparing samples with added TGFβ to samples without added TGFβ in each treatment group; for all other panels, * p<0.05 computed by comparing samples to untreated cells).