After three washes in M9 buffer, animal pellets were resuspended in an equal volume of PBS + complete ULTRA protease inhibitor tablets (Roche) and flash frozen in liquid nitrogen and stored at -80°C until chromatin immunoprecipitation (ChIP). ChIP was preformed using Abcam antibody Ab290. Libraries were prepared using the SPRIworks Fragment Library System (Beckman Coulter) and single-end sequenced on an Illumina HiSeq2000 sequencer with v3 chemistry in high-output mode.