<p>Chromatin Immunoprecipitation (ChIP) assays were conducted using primary calvarial osteoblasts isolated from new born wild-type mice. Anti-Osx antibody (a-Osx) was used for ChIP analysis, and IgG was used as a negative control. The precipitated chromatin was analyzed by quantitative real-time PCR. As described in the Methods, primer Set 1 corresponds to a segment covering the GC-rich element within 80 bp <i>MMP13</i> promoter. As a negative control, Primer Set 2 covers a distal 3 kb region of the <i>MMP13</i> promoter, which does not contain GC-rich sequences.</p
