C2C12 cells at various stages were washed 2x (in PBS + Protease inhibitor), counted to normalize by cell number, cross-linked (ten minutes rotation in 1% formaldehyde), quenched with glycine (at 125mM on ice), washed 3x (PBS+PI) and pelleted at 10e7 cells per eppendorf. Pellets were lysed, resuspended in 1ml sonication buffer on ice (10mM Tris pH 8, 200mM NaCl, 1mM EDTA, 0.5mM EGTA, 0.1% NaDOC, 0.25% NLS and protease inhibitors), transferred to glass 12x12mm tubes (Covaris: 520081) and sonicated (Covaris settings: 5% duty cycle, PIP 140, 200cyles/ burst, 25 minutes). Sonication was then assessed by reverse cross-linking overnight in the presence of proteinase K and RNase, followed by DNA extraction and quantification on a Bioanalyzer (Agilent 2100 machine). Libraries were prepared according to Illumina's instructions. Libraries were prepared according to Illumina's instructions