RNA-Seq: Flow cytometry sorting was performed on live β cells from isolated pancreatic islets of young and old MIP-GFP mice. Total RNA were isolated using the RNeasy kit (Qiagen). ChIP-Seq: ChIP was performed on sonicated chromatin obtained from sorted old and young mouse β cells using antibody against H3K27ac (39685, Active Motif), H3K4me1 (ab8895, Abcam) and H3K27me3 (07-449, upstate). Input and bound DNA fractions were purified using PCR purification kit (Qiagen) for library preparation. BIS-Seq: Genomic DNA was extracted from FACS sorted old and young beta cells using FFPE AllPrep kit (Ambion), sonicated and bisulfite converted by Qiagen Epitect Bisulfite Kit and used for preparation of libraries. RNA-Seq:Libraries were constructed from 200ng of total RNA using the standard TruSeq RNA sample prep kit (Illumina) using manufacturer's protocols. ChIP-Seq: Libraries were prepared using NEBNext ChIP-seq library prep reagent kit according to Illumina's instructions. BIS-Seq: Libraries were prepared following manufacturer's instructions using NEBNext ChIP-seq library prep reagent kit with methylated adapters (NEB).