We purified the pancreatic islets (Kuo et al, JBC 2016) and FAC-sorted the beta cells. ChIP was performed using appropriate antibody against modified histone. ChIP DNA libraries were prepared from ChIP DNA with the following steps: end-repair, dA-addition, adaptor ligation and PCR amplification. The resulting ChIPseq DNA libraries were quantified with Bioanalyzer (Agilent), and sequenced on Illumina NextSeq 500 with 75-nt reads and single-end.