Embryonic day 17.5 (E17.5) nasal septum or postnatal day 1 (p1) rib chondrocytes isolated from wild-type ICR mice were immediately cross-linked with 1% formaldehyde for 10 minutes at room temperature, then 0.125 M Glycine was added to quench formaldehyde. 20,000,000 cells were used for a ChIP reaction. Chromatin was sonicated by 10 sessions of 30 pulses (1 sec on and 1 sec off) at 50% amplitude using the Branson sonifier 250D (Branson Ultrasonics Corporation, Danbury, CT) in order to obtain 100 – 600 bp of DNA fragments. One hundred microlitters of Dynabeads M-280 Sheep anti-Mouse IgG or anti-Rabbit IgG was combined with 9 μg of antibodies for targets of interest. ChIPseq libraries were constructed from input control samples (input DNA and IgG controls) as well as ChIP DNA using ChIP-seq DNA Sample Prep Kit (IP-102-1001; Illumina Inc., San Diego, CA), according to manufacturer’s instruction. Adaptor-modified DNA fragments were enriched by 18 cycles of PCR.