Total RNA was extracted from islets isolated from 7-day old mice using the RNeasy Micro Kit (QIAGEN, Germantown, MD, USA). rRNA depletion libraries were prepared using QIAGEN FastSelect rRNA HMR Kit (Qiagen, Hilden, Germany) and NEBNext Ultra II RNA Library Preparation Kit for Illumina HiSeq (NEB, Ipswich, MA, USA), following the manufacturer's recommendations.