ChIP experiments were performed in dissected proximal and distal forelimb buds of CD1 (wild type) and Prrx1Cre; EedDel/Flox (Eedc/-) mice at E12.5 following the same conditions as previously described (Berlivet et al., 2013). Chromatin was cross-linked for 13 minutes using formaldehyde and sonicated using Fisher Scientific, Model 100 sonic dismembrator to obtain fragments between 100-600 bp. Protein A and Protein G Dynabeads (Invitrogen) were incubated for 6 hours at 4℃ with 5ug of antibody. The chromatin was coupled to the beads overnight at 4℃. The immunoprecipitated samples were then washed with different wash buffers depending on the antibody present. Lastly, the DNA was purified on QIAquick columns (Qiagen).  Library and flow cells were prepared by the IRCM Molecular Biology Core Facility according to Illumina's recommendations and sequenced on Illumina Hiseq 2500 in a 50 cycles paired-end configuration.​