Total RNA was isolated from tissue samples using the TriPure Isolation Reagent (Roche Applied Science, Indianapolis, IN, USA). The RNeasy Mini Kit (Qiagen, Valencia, CA, USA) was used for clean-up according to the manufacturer's instructions. Two µg of total RNA from each sample were quantified and assessed for quality. RNA-Seq libraries were generated using the TruSeq RNA sample preparation kit (Illumina Inc., San Diego, CA).